Christian CULAS 2019 "Nature and Human in Sino-Vietnamese conceptions and practices. Articulations between Asian vernacular "analogism" and Western modern "naturalism" modes of identification"

Keywords: Vietnam, China, Nature, Relation human/non-human, Ontologies, Analogism/Naturalism

One important finding about nature in Vietnam is there are only little studies about the ideasconceptions of nature and about the relations between human and non-human in Vietnam. My main objective is to describe and to understand what are the conceptions and practices of nature in Vietnam today. To attempt to reconstruct the conceptions of the world and the relationships humans / nature (or "non human" (Latour 2004) in Vietnam, I will proceed in two ways. First, I will give an overview of historical landmarks of the conceptions of relations human/nature and human/human (politics), because Vietnam is one important place where traditional Chinese mode of identification and worldview ("analogism" Descola 2005) and modern Western mode of identification and worldview meet ("naturalism") and build a new synthetic and hybrid way of thought and action. Second, some examples of what nature means in Sino-Vietnamese conceptions and practices will show the diversity of ways of thinking and acting nature. Historical process that built the current conceptions and practices of nature in Vietnam is deeply syncretic and hybrid.

Three examples selected will help us to understand what are the diversity of Vietnamese conceptions of nature: a) Taoist conceptions of Nature where man can learn and experience to reach nature through practice. b) Man can integrate some powers of nature by eating them. c) In Vietnamese conceptions and actions nature can be built by and around the human in "nature garden", similar in many points to Japanese notion and landscape calls "Satoyama" where biodiversity is built and maintained by human.

These examples of contextualized conceptions and actions with nature can show how the analogical tradition can articulate, integrate, and oppose with different forms of naturalism in certain specific situations to build the current conceptions and practices of nature in Vietnam.

Introduction

1) Finding

According to surveys I conducted since 2006 in Northern and Southern Vietnam1 and on the basis of the literature, we find that the vast majority of projects for the protection of natural areas or the environment in general applied in Vietnam are failures. [START_REF] O'rourke | Economics, Environment and Equity: Policy Integration During Development in Vietnam[END_REF][START_REF] O'rourke | Community-Driven Regulation: Towards an Improved Model of Environmental Regulation in Vietnam[END_REF][START_REF] Zink | Hot Science, High Water. Assembling Nature, Society and Environmental Policy in Contemporary Vietnam[END_REF]). The reasons for these failures are multiple. Some are related to the orientations of Vietnamese public policies. Vietnam, like many other countries2 , faces a dilemma in its development process. In order to maintain a high rate of economic growth, Vietnamese governments have chosen to promote industrialization and intensive agriculture at the expense of protecting the environment. [START_REF] Bass | Integrating Environment and Development in Viet Nam. Achievements, Challenges and Next Steps[END_REF][START_REF] O'rourke | Economics, Environment and Equity: Policy Integration During Development in Vietnam[END_REF][START_REF] Sikor | Economic and Environmental Dynamics of Reform in Vietnam[END_REF]. Other reasons are also related to the functioning of the information-communication system and control of violations of environmental protection laws. In short, the complexity of the laws and the very frequent corruption among civil servants are obvious obstacles to effective protection [START_REF] Do | Transplanting Common Law Precedents: An Appropriate Solution for Defects of Legislation in Vietnam[END_REF]Culas forthcoming 2018). Based on field studies and a wide range of literature on this topic, I can say there is one of the reasons usually forgotten or missing by researchers and experts: It is about the ways of thinking and acting the relations between human and nature (or non-human) by Vietnamese population. My paper focuses on some specificities of nature's conceptions and practices in Vietnam in order to better understand the difficulties of applying environmental protection projects in this country. It is interesting to note that all the environmental protection projects applied in Vietnam have been conceived and designed on a Western philosophical and ontological reference scheme. Implicitly, the populations involved locally in these projects are supposed to have the same conceptions of nature as Westerners… First I need to explain what "Western philosophical and ontological reference scheme" means. Historical and philosophical researches that studied the construction of the idea of "nature" in the West has shown that the exclusive division between humans (culture, language, thought) and nature (without culture, without language, without thought ) is a production from the Renaissance (14th to 16th centuries) and the beginnings of modern science in Europe [START_REF] Descola | Par-delà Nature et Culture[END_REF][START_REF] Latour | Politique de la Nature. Comment Faire Entrer les Sciences en Démocratie[END_REF]). In short, from this period, we observe a formalization of the thought of nature according to a dual and exclusive model: Culture / Nature, Human / Nonhuman. This ontological schema or "modes of identification" developed in the West to think nature is called "naturalism" because it essentializes nature as an entity distinct from humans. While in China, Vietnam and Japan, if the division Nature / Culture exists in some forms, it is less rigid and especially many bridges are thought to connect humans and non-humans by correspondence and analogies (Bruun and Kalland 1992).

The central idea of this approach is that each culture, each human group or society will classify humans and non-humans3 according to a large number of criteria (same physical, same ancestors, same kinship system, same spirit, etc.). This broad set of criteria can be summarized into two main distinctions: resemblance / difference of interiority (spirit) and resemblance / difference of physicalities (body). The synthesis of these ontological possibilities is presented in the diagram below. The above-mentioned theoretical framework will be the basis of our demonstration. The thinking and practice of Chinese and Vietnamese in relation to nature are globally classified in the "analogism" because in this mode of relations between human and nonhuman we observe that "Everything is constantly connected with everything". The distinctions between humans and non-humans are not key of thinking in Sino-Vietnamese conceptions. Because all the categories of actors in the world (human and non-human) are all different, then the Chinese and Vietnamese modes of identification work on the mapping of these different categories, this is what is called "analogism". It is by analogy that the different categories of the world are strongly linked to make sense, to make system. But for this very diversified world to be thinkable, these analogical modes of identification have created many forms of hierarchies between beings. The first of them applies to the cosmos which is divided into three levels: the highest is the "Sky", the middle level is that of "Men" and the lower level that of the "Earth". The classic Chinese formula is "Put the man in the center" (以人为本) » (Ouyang 2008: 1). In the same logic, China, Vietnam and Japan, have built social and linguistic hierarchies between men. As evidenced by the different levels of Vietnamese terms, the use of neutral "I" and "you" (as in English) are most often replaced by classificatory terms such as "older brother", "younger brother, "older aunt", "younger aunt", etc. In these systems of thought, the person is not isolated by the words that designate her, to name a person is to call to the all social, cultural and symbolic hierarchy that gives her his complete position and status [START_REF] Berque | speaks of "phenomenological" dimension, and the sinologists specialists in Taoism[END_REF][START_REF] Berque | speaks of "phenomenological" dimension, and the sinologists specialists in Taoism[END_REF][START_REF] Mus | Planète Viêt-Nam. Petite Sociologie Visuelle[END_REF].

Modes of identification

Modes of identification

2) State of art about Vietnam

The questions we raise here about the thought and actions of and about nature have been analysed in different ways for a long time in China 4 and Japan5 , but they are still very little studied and there is no intellectual Vietnamese production on the relationships between human and nature.

I would like to start with a brief state of knowledge in the literature on the relationships between humans and non-humans in Vietnam. Unlike China and Japan where there are philosophical and religious schools that study the relationship between men and nature for several centuries. The first works on the question of nature in Vietnam dated from the French colonial period 6 (1858-1945) [START_REF] Przyluski | Note sur le Culte des Arbres au Tonkin[END_REF][START_REF] Cadière | Croyances et pratiques religieuses des Annamites dans les environs de Huê. I. Le culte des arbres[END_REF][START_REF] Stein | Jardins en Miniature d'Extrême-Orient[END_REF]). These are usually ethnographic studies of pagoda gardens and tree cults. In the years 1980 to 2000 with the economic opening of the country, new studies deal with these topics. The most remarkable works based on precise field surveys are those of ethnobotanist Dinh Trong Hieu 7 . As the titles of these articles can show "Signs-Nature, Signatures, Biodiversity: the 'religious groves' in Vietnam. For a concept of 'green vestiges ' " (1997) and "Gardens in Vietnam: the nature between cultural representations and cultural practices" (2000). Two of his articles directly address broader issues such as "The Impacts of the Communist or Marxist-Leninist Development Model on the Environment in Vietnam" (1990) and "The Relationship between the Social Sciences and Biodiversity" (2003).

For the years 2000, we note an original sociological survey by questionnaire of twenty people in Hanoi [START_REF] Pham | Environmental Consciousness in Vietnam[END_REF]. The main objective of this innovative study was "Comparative studies of public perceptions of environmental problems and environmental consciousness in Hong Kong, Japan, Thailand, and Vietnam". The secondary objectives were to know how people perceive environmental responsibilities between individuals, governments and large private companies. The main weakness of this survey is that it only records responses to an environmental questionnaire. This is not enough to know the real practices of the Vietnamese. We must also point out Frédéric Thomas's Ph.D thesis about The forest exposed: anthropological essay on the construction of a tropical scientific object: "Indochinese forests and woods", (2003). From a historical point of view, several chapters approach the Chinese and Vietnamese cosmologies on forests and on nature and also introduce the diversity of conceptions of nature in Vietnam by highlighting the cosmologies and rites of certain ethnic groups of Highland of Central Vietnam. Except for Dinh Trong Hieu's works, there is to my knowledge no serious field study that deals with the relationship of men to nature among Kinh (majority group in Vietnam). On the other hand, some anthropologists specializing in "minority" mountain ethnic groups have studied the relationships between local cosmologies and the conceptions of nature 8 . With regard to the literature on Vietnam, there is a lack of both field researches and synthetic and philosophical approaches that integrate the symbolic and phenomenological dimensions of the man / nature relationships. However, from the above data and their contextualization with the religious and popular representations of the Vietnamese, it is possible to begin to see the outlines of the thoughts and practices of nature.

Of course, there are many studies in Vietnam on the management of natural resources9 (fauna, flora, management of protected areas...) but these researches are almost all focused on a "Western naturalism" approach and is based on the principle that man and nature are two exclusive and distinct entities. On the other hand, almost all of these works study human and natural relations through the relations of uses, productive relations and technical relations. All symbolic, religious, emotional and philosophical dimensions of human / nature relationships are forgotten. The purpose of this paper will also be to show that in order to understand what nature means in Vietnam today, we must be able to integrate both the technical and scientific dimensions (such as the utilitarian uses of natural resources) as well as the dimensions less easy to grasp and to describe, such as those related to tree cults, sacred forests or the symbolic aspects of plants and animals of traditional Vietnamese medicine. In this way, my approach is similar with Augustin Berque (2014) when he finds that modern science based on the "naturalist" modes of identification focuses solely on the technical, utilitarian and economic dimensions of human activities, but that it obscures all the activities of "phenomenological" type that can also be called sensitive, emotional, affective or belief-related activities.

To attempt to reconstruct the conceptions of the world and the relationships humans / nature in Vietnam, I will proceed in two ways that will structure this article: First, I will give an overview of historical landmarks of the conceptions of relations human/nature and human/human (politics), because Vietnam is one important place where traditional Chinese modes of identification and modern Western modes of identification meet and build a new synthetic way of thought and action. Second, some examples of what nature means in Sino-Vietnamese conceptions will show the diversity of ways of thinking and acting nature. What I present today is still a work in progress, this is just the first step of a long term research project.

I -Historical landmarks of the conceptions of relations human/non-human

Presenting the history of the conceptions of nature in Vietnam in a few broad phases may seem very simplistic, it is not a question here of going into details but rather of showing how historical conceptions and modes of identification can be synthesized to constitute the complexity of current conceptions. I will only outline the four bold steps in the diagram above, as they are the most important milestones in the evolution of human and non-human relationship conceptions in Vietnam.

1) Ancien Vietnam under Chinese rules

From 1st century BCE to 10th century after, Vietnam was under Chinese rules. During this long colonization, intellectual and political elites were trained according to Chinese criteria to build a body of scholars. This body of political, moral and aesthetic principles will gradually spread to the entire Vietnamese population. Thus these principles and their practical applications will be borrowed, assimilated and often adapted by the population of all social classes. Thus will gradually established a Sino-Vietnamese cosmology without conceptual separation between nature and human. Some Chinese literary formulas describe this cosmology: "All belong to The Great All, the orders and hierarchies create the links between them". For example, the conception of imperial political power is directly connected to the cosmological conception of the world. The Chinese character "King" 王 (Váng) has a traditional etymology: three horizontal lines are Sky, Human and Earth, and the vertical one is making the best connection between them. It symbolic meaning is "To govern is to establish the harmony between Heaven, Human and the Earth". We find again the idea of the link and the search for harmony between entities and distinct cosmological spaces. Relationships between human and nature and human and human are based on analogical mode of identification (Descola 2015).

2) French colonisation (1858-1945)

French colonisation introduced in Vietnam a conceptual and exclusive separation between nature and human 10 . The two domains that will have the greatest impact in Vietnamese thinking are the introduction of modern scientific, technical and industrial approaches and, some new political ideas including individualism, State-Nation system, democratic and human rights. We note that Vietnamese elite incorporated some elements of Western naturalism with a strong focus on political points of view because their main objective was national emancipation in reaction to colonial domination. But they paid less attention about new conception of nature. But the most important borrowed items about relationships with nature are probably Western medicine and science. Today we can observe a juxtaposition without contact of two medical systems in Vietnam: the traditional one based on an ancient knowledge fund partly common to China, the other Western-style scientific and technical medicine. Western naturalism mode of identification was also a strong basis for Marxist-Leninist ideology. The liberation of the country from the French colonial forces will be partly thanks to communist organizations. I will distinguish two communist periods because their political orientations and practical applications are very different.

3) First Communist Period (1945 à 1986)

During the First Communist Period (1945 à 1986), Marxism -Leninism ideology and project was an imported system of human relationships from Russia, China and France. In short, we can say this is an extreme case of application of Western naturalism (Descola 2015) because development of human society can be done without paying attention to non-humans. The main components of the Communist Party-State ideology and actions are: -Marxist social evolutionism is founded on a "natural" and "historical" hierarchy between societies with different steps of material, technical and political development (from feudal society and capitalist society to communist society) -Collectivization of the means of production is actions against capitalist system to share resources and productions tools with equitable distribution for all.

-Modernisation and industrialisation used natural resources without limit as tools to achieve these goals of nation development to reach communist objectives.

-The main tools of this socio-economical and political system are a very strong social, cultural and political control on the society, because the final aim is to build the "New Socialist Man" for Revolutionary purposes to reach the "Perfect society".

4) Second Communist period (1986 until today)

The Second Communist period called « Transitional Period » begins with Đổi Mới Economical Reforms (1986) and continues today. The new national slogan is "Socialistoriented market economy". In short, to achieve the ultimate communist goal one must use the capitalist system, as China did since the 1980s. From the analytical point of view, this is another aspect of Western naturalism mode of identification because on Western capitalist ideology nature and non human don't have any right, so they can be used to produce wealth and generate profits. On this point, Marxism and capitalism share the same relationship of uses of nature. The main components of this transitional period are: -Marxist social evolutionism need to be adapted because market economy will be a new support to build the socialist society.

-The Private enterprises are often strongly connected with Party-State system. These connections and the high level of corruption among officials allows a very low level of respect of the laws: This leaves a large open door for many offenses for the environment (massive deforestation, large-scale agricultural and industrial pollution).

-The first national goal is economic development, which is also a guarantee of political stability, for that, we rely on the use of natural resources. Economic development is the first and the protection of the environment comes after, later.

-Even with important economical changes, we observe a strong cultural and political control on civil society and media (Internet, newspapers, social movements…)w;

Beyond the complexity of borrowing and syncretism processes (which we cannot detail here), the main thing to remember is how these ideas and practices will fit in superimposed layers. We observe this even if the new elements seem to contradict the old ones. As seems to be the case of Sino-Vietnamese traditional medicine based on analogies between natural substances and parts of the human body and technico-scientific medicine based on chemistry and modern physics. However, these elements are not mutually exclusive or not delete each other out. They are cohabiting. For example, it is usual for Vietnamese patients to follow a traditional medical treatment and at the same time a modern treatment. The fact that these treatments belong to two logical, two distinct modes of identification does not make any problem for the patient. In practice, in a pragmatic way, they can accumulate and syncretized by superpositions of more or less nested layers. However, detailed case studies of these ontological syncretisms are still missing for Vietnam. We observe these different forms of syncretism both in discourses (see the very utilitarian dimensions of national development objectives) and the daily actions of Vietnamese (cults of sacred trees and forests on one side and the other side (serious industrial and domestic pollution...) in relation to nature today.

II -Examples of relations between nature and man in Vietnam, China and Japan

The three examples below of what "nature" means in Sino-Vietnamese world will make it possible to show the diversity of the means of expression of the relation to nature in the same mode of identification and at the same time the homogeneity of the type of exchange between human and non-human.

1) Learn to reach nature through practice

According to the Chinese philosopher Chuang Tzu (4th century BC): When men reach a very high level of mastery of their arts (religious rituals, studies of classical texts, technical and aesthetic through physical exercise or handicraft, etc.), they can act without mobilizing their minds. For example, an excellent wood-carver can take several decades to make his action on the wood without having to think about it. A kind of automatism both conscious and spontaneous made possible because man, material and action are no longer separated, or so little separated that they succeed in making totally One. The action is then done in a natural way, without effort and reaches its perfection. This action is then in conformity with Sky, which is natural and spontaneous [START_REF] Billeter | Notes sur Tchouang-Tseu et la Philosophie[END_REF]. The action of man on the world is then in harmony with Sky and Earth, so by this way man can then reach nature. We find again the idea of governing in harmony with the cosmology which is at the center of the practice of management of men by traditional Chinese royalty. Man can access to nature by a long work on himself. So access to nature is achieved by a significant effort, a deep attention to non-human and actions and long time training. This idea and practice are in opposition with Western conception of nature where nature is thought of as something "given" that cannot be "acquired" by experience, conscience and training. This first example also shows that ancient Chinese philosophical and ontological conceptions are often directly connected with very concrete or even technical practices, such as calligraphy, Tai-chi-chuan, wood carving, swimming in whirlpools or cutting of meat, etc. [START_REF] Billeter | Notes sur Tchouang-Tseu et la Philosophie[END_REF], Levi 2003). Thought and action are usually united in this world.

2) Integrate some powers of nature by eating them

China and Vietnam are two countries with a very high demand for wild meat from protected species for traditional medicine uses but also for cooking expensive dishes. Thus the last rhinoceros was killed in Cat Tien national park (Southern Vietnam) in April 2010 for his horn sold 20.000 Euros. The last tigers and bears are endangered because of the very high price of their meat. Chinese and Vietnamese believe that animal species are able to transmit their qualities to humans. By eating certain parts of these animal humans can incorporate some of their physical and spiritual qualities. For example, meat and bones of tiger and bear are supposed to transmit the power of the animal, especially the sexual force. The horn of Rhinoceros because it symbolically resembles a phallus are supposed to strengthen the sexual abilities of the man, it is the same for fresh snake blood. While the chemical composition of Rhinoceros horn is exactly the same as the human hairs and nails and snakes sexual abilities are rather mundane. These are symbolic actions and thought by analogy. This is the same analogical thinking than medical "doctrine of signatures 11 " in European Middle Age: "the leaves in the shape of eye look after the eyes"… This is an example, where human and non-human can share the same domain. Although different in their physicality and in their interiority, humans and non-humans can exchange physical abilities.

3) Building nature around the human -Pagoda Gardens in Vietnam

For Vietnamese peasants of Red River Delta, we observed that for them nature is not a distant thing that one would encounter in the deep forests or in the mountains far from their own places of life, but nature is mainly around them, just next to them [START_REF] Culas | Relations entre l'Histoire de la Gestion des Espaces Agricoles et l'Environnement au Vietnam[END_REF]. In a milieu they know well and on which they act on a daily basis. According to them, nature is especially present in the gardens of pagodas, in their own gardens and in the big old trees at the crossroads [START_REF] Przyluski | Note sur le Culte des Arbres au Tonkin[END_REF][START_REF] Stein | Jardins en Miniature d'Extrême-Orient[END_REF], Dinh 1985[START_REF]Signes-Nature, Signatures, Biodiversité : les 'Bosquets Cultuels' au Vietnam. Pour un Concept de 'Vestiges Verts[END_REF]. This specific way of thinking and constructing nature contrasts sharply with the Western idea of "wilderness", protected from the attacks of human activities: A "virgin nature" thought out of any relation to man (Larerre 2008).

-Satoyama: Biodiversity maintained by human in Japan The Japanese notion of Satoyama combines in a single word the idea of nature, of human and the relationship between them. "Sato" means "village and its agricultural lands" and "Yama" means "mountain and the maintained forests that make it up". Satoyama includes the environmental mosaic of forests, tree plantations, grasslands, farms, lakes and villages. This is a specific form of bidodiversity maintained and built by humans. In 2010 at UNESCO assembly, Japan proposed to introduce the concept of Satoyama into international regulations on environment and biodiversity12 . Satoyama means man and nature are not separated but necessarily connected by reciprocally influencing each other. The idea of "man made landscapes that build man" (Takeuchi 2010) is also central in A. Berque's demonstration (2014) to overcome and criticize Western dualism thought between human and nature. To describe the relations woven between humans and non-humans in Satoyama, specialists speak of "socio-ecological landscapes" [START_REF] Ichikawa | Socio-Ecological Production Landscapes in Asia[END_REF]. I think according to the examples above, it is possible to go further in the analysis of the meaning of "socio-ecological landscapes13 ". In a discrete but central way, the Satoyama diagram above presents the third perspective as "Recognition of the value and the importance of local tradition and culture" (my italics). But the content of this perspective is not only sociological and ecological, it asks to introduce other dimensions that are underlying in our examples above. The notion of "Value" is directly connected with ethics and religion, thus with the relationships between humans and non-humans, sometimes including immaterial beings (spirits and divinities, and all beings of the so-called "supernatural" world).

In fact, Satoyama is not only innovative because it integrates ecological and social dimensions and their reciprocal interactions, but it also opens the landscape to philosophical, ethical and religious dimensions.

Conclusion

These three examples show the diversity of the conception of nature and non-human in the Sino-Vietnamese and Japanese world. In the first example, nature is the product of human learning after a long practice until the activity becomes integral part of the human being. The second example show how certain qualities of non-humans (animals or plants) can be integrated into the human body and mind-spirit. Finally, the last example shows how the idea of nature and biodiversity is not to be found in isolated, protected and supposedly "virgin" spaces, but rather in gardens and socio-ecological landscapes built and maintained by man. One of the common features of these examples seems to be that nature is not a self-defined and immutable state (as in the Western naturalism mode of identification) but this is the product of an action (examples 1 and 3), or the product of a relationship between human and non-human (examples 2). In Western naturalistic mode of identification, nature is defined as a state of things, as an object. There is nature when there is no man. In the Sino-Vietnamese analogical mode of identification, nature is defined rather by types of actions and specific agreements between humans and non-humans. It is in a very particular relationship with humans that nature can be defined. In the world, there is thus a wide variety of ways of how to conceive of "nature" and the relationship between humans and nature. Many of them are still largely unknown. Often these relationships are only lived and acted by the local people, but there are not the object of philosophical and ontological discourses constructed. This is what we observed for Vietnam and for the populations of mountain ethnic groups in Vietnam, China, Laos and Thailand, but also for many forest populations in the Amazon or Siberia (Descola 2015). In the case of China, some Taoist, Buddhist and Confucian schools of thought have for several centuries studied the relationship between man and nature, including political, medical, religious and metaphysical dimensions. Describe, know and perhaps understand the conceptions and practices of nature in different social groups of Vietnam (artisanal fishermen, collectors of plants and animals in the forest, rangers, mountain farmers, polluting industrialists ...) will allow to define what discourses on nature they are willing to hear and understand from a protection project, but also what they will be able to do in this direction. These different ways of speaking about nature and the possible protective actions will be built with local people and according to their conceptions and practices. But the protection project must still be able to integrate all the local dimensions of nature, so it must be able to challenge Western supremacy over the dual idea of Nature / Culture. The analysis of human societies is usually based on three broad dimensions (economy, social and environment). But these three dimensions do not make it possible to describe for all the relationships that humans have with non-humans, and in particular with nature. By introducing new dimensions, such as philosophical, ethical and religious, but also the emotional, affective and sensitive dimensions, because they produce meaning, channel or guide the relations between humans and non-humans, we will reach a level of understanding

Fig. 1

 1 Fig. 1.1 Scheme of modes of identification possible (Descola 2005: 221, adapted by Culas 2018)

Fig. 3

 3 Fig.3.1 Scheme of Satoyama Initiative (http://satoyama-initiative.org/en/)

Lao Cai and Kien Giang provinces.

See extreme pollution cases of Chinese cities.

Since B.[START_REF] Latour | Politique de la Nature. Comment Faire Entrer les Sciences en Démocratie[END_REF], we prefer the notion of "non-human", which is more descriptive and not ideological than "nature", because the opposition between human and nature is not necessary. The non-human can be an object (a mountain, a river, a car ...), a living being (plant, animal), an arrangement or a spirit or a god.

For example, in China, the study of relationships human / nature is very old, as shown by a poet and philosopher, Tao Yuanming (365-427) which is a symbol of classical Chinese study about nature[START_REF] Lu | The Ecological Era and Classical Chinese Naturalism[END_REF][START_REF] Lee | Xunzi and Early Chinese Naturalism. Suny Series in Chinese Philosophy and Culture[END_REF]

Japan concentrates several original initiatives. The most important is certainly "International Partnership for the Satoyama Initiative" promoting collaboration in the conservation and restoration of sustainable humaninfluenced natural environments (Socio-Ecological Production Landscapes and Seascapes) through broader

[START_REF] Vu | Forest Ecological Stratification in Vietnam, Hanoi: RCFEE, FAO, UN-REDD[END_REF],USAID (2013)

The presentation of Mrs Bui Linh Hue (Thai Nguyen University, Vietnam) about "A Ecocritical Study of the Discourses on Progress and Western Civilization by Early 20th Century Vietnamese Intellectuals", made at the ASLE Conference in Hanoi (2018), complete my demonstration of Vietnamese borrowings to French modernity.

The Global Workshop on the Satoyama Initiative was held at UNESCO (Paris, 2010).

See the history of invention of landscape in China (4th century) and Europe (16th century)(Berque 2013).


Antony Cyril Arulrajan

Christophe Renault

Stanley C S Lai
email: stanley_chi.lai@syngenta.com

How changes in interfacial pH lead to new voltammetric features: The case of the electrocatalytic oxidation of hydrazine

The electrochemical oxidation of hydrazine was investigated in strongly and weakly pH buffered solutions to reveal the role of buffer capacity in proton-electron transfer redox reactions. In sufficiently buffered solutions, a single voltammetric feature was observed. However, increasing the hydrazine concentration (or, equivalently, moving to an insufficiently buffered solution) gave rise to a second voltammetric feature. These results are rationalized with a conceptually simple model and finite element simulations. We demonstrate that the new voltammetric feature is caused by a large change in the pH at the electrode surface as the reaction proceeds. Importantly, we show that the occurrence of additional voltammetric features are general for proton-electron transfer reactions in insufficiently buffered solutions, and should not be confused with changes in the reaction mechanism.

Introduction

Proton-electron transfer reactions 1,2 are (half-)reactions in which both protons and electrons are transferred. Such reactions are ubiquitous in chemical and biological processes. In particular, many redox reactions which are currently being studied involve the transfer of both protons and electrons, in diverse research fields such as energy generation (e.g. the oxidation of hydrogen, hydrazine or small organic molecules, or the reduction of oxygen), fuel generation (e.g. CO2 reduction and water splitting reactions) and bioanalytical chemistry (e.g. oxidation of neurotransmitters). In general terms, proton-electron transfer half-reactions occurring at an electrode surface can be described by equation 1

Red ⇌ Ox + m H + + n e - (1)
Here, the oxidation reaction releases protons into the electrolyte solution, whereas reduction consumes protons, and the electrode acts as an electron donor or acceptor. Thus, the electrochemical processes can change the pH at the electrode surface in unbuffered or weakly buffered solution, causing it to differ from the pH of the bulk solution. A variety of techniques has been employed to map such (proton) concentration gradients near electrode surfaces and other interfaces. [3][4][5][6][7][8][9][10][11] For example, fluorescence confocal laser scanning microscopy has been employed to provide three dimensional images of pH gradients at (arrays of) microelectrodes of various types and configurations resulting from the reduction of p-benzoquinone, 3 the hydrogen evolution reaction [4][5][6] and the oxygen reduction reaction, 4 all of which consume protons, causing an increase in the interfacial pH. This capability to visualize surface pH with an optical method has shown promise as a tool to identify faulty electrodes in a microelectrode array, 4 to electrotitrate on a micrometer scale, 6 and for the identification and screening of electrocatalysts. 5,11 Alternatively, pH gradients near interfaces can be visualized by means of scanning electrochemical miscroscopy (SECM), using either amperometric 8 or voltammetric probes. 9, 10 Thus, while the formation of a pH gradient at an electrode surface due to proton-electron transfer reactions have been well established, how the interfacial pH change in turn impacts on the kinetics of protonelectron transfer reaction has remained somewhat overlooked. 12,13 Here, we investigate the interplay between electron transfer kinetics and interfacial pH changes for electrocatalytic protonelectron transfer reactions, using the oxidation of hydrazine (N2H4) as a model system. The electrochemistry of hydrazine is of great interest for fuel cell applications, as it is liquid at room temperature (facilitating transport and storage), has a high theoretical energy density, and its oxidation produces carbonfree products. 14,15 Furthermore, hydrazine (derivates) are used extensively as precursors in the synthesis of pharmaceuticals and agrochemicals. However, residual hydrazine constitutes a key genotoxic impurity, and consequently there is considerable interest for the (electrochemical) detection of hydrazine. 16,17 Finally, from a fundamental point of view, hydrazine oxidation This journal is © The Royal Society of Chemistry 20xx

Please do not adjust margins Please do not adjust margins is often employed as a model electrocatalytic system as the onset potential strongly depends on the electrode material and structure, yet quickly reaches mass transport limitations once the onset potential is exceeded. This makes it, for example, a popular choice for a redox probe in nanoparticle collision experiments. [18][19][20][21][22] The overall reaction (in acidic and neutral media) is given by equation 2:

N2H5 + → N2 + 5 H + + 4 e - E 0 = -0.33 V vs NHE (2)
It is generally accepted that the reaction on platinum is initiated by the reversible adsorption of (the deprotonated form of) hydrazine at a vacant surface site, followed by stepwise deprotonation steps that leave the N-N bond intact.

There is some debate on rate-determining step, which may depend on the structure of the electrode surface as well as electrolyte composition. [23][24][25] Regardless of the precise mechanism, voltammetric profiles of hydrazine oxidation typically show a single irreversible voltammetric feature. [25][26][27] In this work, we employ hydrazine oxidation as an exemplar electrocatalytic proton-electron transfer reaction involving both adsorption and reaction steps and at both macroscopic (mm-size) and microscopic platinum electrodes in pH-buffered electrolyte solutions. Importantly, we will highlight the importance of buffer concentration in studying protonelectron transfer reactions. Finally, we will demonstrate with a simple fundamental model how the use of insufficiently buffered solutions can cause unexpected voltammetric profiles for proton-electron transfer reactions.

Experimental

Finite element method

All simulations were performed using the finite element method (FEM) modeling package Comsol Multiphysics 4.4 running on a personal computer with a 3.4 GHz processor and equipped with 8 GB of RAM. Full details on the simulations are provided in the Supporting Information.

Results and discussion

Figure 1a schematically depicts the various physical and chemical processes involved in the hydrazine oxidation reaction in a buffered solution of neutral and acidic pH. Under these conditions, hydrazine predominantly exist in its protonated form, N2H5 + (pKa,hydrazine ≈ 8.2). 28 Other molecular species in the (bulk) solution are protons (H + ) and a conjugate acid-base pair (HA and A -). In this study, H3PO4 and H2PO4 -was used as conjugate acid-base pair for buffer solutions with 1 < pH < 4 (pKa = 2.2), and H2PO4 -and HPO4 2-for pH 6-7 solutions (pKa = 6.9). Here, the hydrazine oxidation reaction is described by a two step process:

N2H5 + + Ptsite ⇌ N2H4,ad + H + (3a) N2H4,ad → N2 + 4 H + + 4 e - (3b)
Initially, hydrazine in solution is reversibly adsorbed as on a vacant platinum site, releasing one proton in the process (equation 3a). As the electrochemical oxidation reaction is initiated, adsorbed hydrazine is converted to molecular nitrogen, while releasing four electrons and a further four protons (equation 3b). This generates a concentrations gradient, causing a diffusional flux of hydrazine from the bulk solution towards the electrode surface. Meanwhile, the released protons react with the buffer species to establish a new local acid-base equilibrium. This local equilibrium can have concentrations of the participating species which differ from those in the bulk solution, generating a diffusional flux of these species to and from the electrode surface.

A typical cyclic voltammogram (CV) for the oxidation of hydrazine at low concentrations in a phosphate buffer solution (pH 6.9) on a polycrystalline platinum electrode is shown in Figure 1b, along with the corresponding blank CV (i.e. without

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Please do not adjust margins hydrazine in solution). This CV is in good agreement with those widely reported in literature. [25][26][27] Under the present working conditions, hydrazine oxidation starts at ca. -0.45 V, within the hydrogen underpotential deposition region of the platinum electrode. This corresponds to an overpotential of ca. 600 mV, demonstrating that, even on catalytically active materials such as platinum, this reaction is subject to substantial kinetic limitations. Hydrazine oxidation quickly reaches a diffusionlimited peak current at -0.38 V, followed by a broad current plateau. [START_REF] Bard | Electrochemical Methods -Fundamentals and Applications[END_REF] The fact that no reduction peak can be observed further confirms that hydrazine oxidation is an irreversible process (at least in this potential window). The CV for hydrazine oxidation also shows that the characteristics of the blank CV, such as the oxide formation and reduction process, are retained.

As shown in Figure 1c, the pH-dependence of the peak potential and the half-wave potential (i.e. the potential at which the current is half of the peak current) for hydrazine oxidation of -72 ± 3 mV / pH unit and -70 ± 3 mV / pH unit, respectively, obtained from CVs for hydrazine oxidation in buffers of varying pH (Supporting Information, SI-1) These (absolute) values are larger than the value expected for a 'trivial' (i.e. Nernstian) pH-effect of -59 mV/pH unit, indicating that effects other than the proton concentration contribute to the overall pH-dependence of the reaction In order to gain further insight in the role of possible pH shifts during the hydrazine oxidation reaction, CVs were obtained for solutions with varying hydrazine concentrations, whilst keeping the buffer concentration fixed at 50 mM phosphate (pH 6.9). Figure 2a-i shows the CVs at low hydrazine concentration (0.5, 2 and 5 mM), corresponding to high buffer-to-hydrazine ratios (100, 25 and 10 respectively). It can be seen that under these conditions, the CVs have the typical profile for hydrazine oxidation (vide supra). As the hydrazine concentration is increased in this concentration range, the observed currents increase proportionally, and the oxidation peak current shifts towards more positive potentials, as expected for a diffusionlimited irreversible electrochemical reaction. [START_REF] Bard | Electrochemical Methods -Fundamentals and Applications[END_REF] A further increase of the hydrazine concentration to 7 and 10 mM (buffer-to-hydrazine ratios of 7.1 and 5; Figure 2a-ii) gives rise to a second oxidation peak, at approximately 0 -0.1 V. A closer inspection further reveals that both the magnitude and the position of the first (initial) oxidation peak become nearly independent of the hydrazine concentration. Similar doublepeaked voltammetric profiles have been previously been reported for the hydroquinone/p-benzoquinone redox couple 13,[START_REF] Rafiee | [END_REF][31][32] and the hydrogen oxidation/evolution reactions 12 (both of which involves the exchange of two protons and two electrons) in minimally buffered and unbuffered solutions.

Various mechanisms have been put forward for this behavior, including changes in interfacial pH, 12,13 variations in the protonation state of the redox species, 32 differences in basicity of solution species, [START_REF] Rafiee | [END_REF] and changes in the reaction mechanism. 31 While it is tempting to assign the two oxidation features to a multi-step mechanism, here we will argue that the main cause of the appearance of a second voltammetric feature in the oxidation of hydrazine is the result of changes of the interfacial pH during the reaction. In particular, we will show that the appearance of the second voltammetric feature is caused by a shift in the adsorption equilibrium preceding the electrochemical reaction. To illustrate this concept, we have employed FEM modeling to set up a general model for protonelectron transfer reactions. This model is described in detail in Supporting Information (SI-2). Conceptually, the model is fairly simple, and consists of the four elements outlined in Figure 1a, namely diffusional mass transport of species to and from the electrode surface, a solution-phase acid-base equilibrium, a hydrazine adsorption equilibrium at the electrode surface and the electrochemical reaction of adsorbed hydrazine. Mass transport and the acid-base equilibrium are described by Fick's diffusion laws and the Henderson-Hasselbach equation, respectively. The adsorption equilibrium is described by a Langmuir isotherm:

𝐾 𝑎𝑑𝑠 = [N 2𝐻4 ][𝐻 + ] [N 2𝐻5 + ][Pt] (4)
, where [N2H4,ad] and [Pt] are surface concentrations (in mol cm -2 ), while [N2H5] and [H + ] are volume concentrations (mol cm -3 ). Both the acid-base and adsorption equilibria are considered to be fast (at equilibrium) compared to the diffusion of species and the electron transfer kinetics. Finally, the electron transfer is described by a Butler-Volmerlike relationship for an irreversible reaction (equation 5):

𝑗 = 𝑛𝐹𝐷𝐶𝑘 0 exp[(1 -𝛼) 𝑛𝑎𝑝𝑝𝐹 𝑅𝑇 (𝐸 𝑎𝑝𝑝 -𝐸 0 )] (5)
, where F, R and T are defined previously, E 0 is the formal potential for the reaction of N2H4,ads (equation 3b), j is the current density, C is the (pH-dependent) surface concentration of adsorbed hydrazine, Eapp is the applied potential, D is the diffusion coefficient of hydrazine, k 0 is the heterogeneous electron transfer rate constant, α is the transfer coefficient, and napp is the number of electrons exchanged in the rate determining step. It is important to note that we do not assign a specific molecular mechanism to the hydrazine oxidation reaction, other than the presence of a pre-adsorption step.

While we recognize that this may be simplified interpretation of the hydrazine oxidation reaction, we will show below that the main concentration dependency of the voltammetric profiles are well captured by this simple model. Furthermore, by not including specific mechanisms for the electrode reaction, we believe insights from this model can be generalized to other proton-electron transfer reactions involving a pre-reaction adsorption step.

The key element of this model is that changes in surface pH are reflected in changes of the position of adsorption equilibrium in equation 3a, thereby changing the activity of the This journal is © The Royal Society of Chemistry 20xx

Please do not adjust margins Please do not adjust margins reduced species in the electrochemical step (equation 3b). Using this model, we have simulated CVs for hydrazine oxidation, shown in Figure 2b. Comparing the simulated CVs with the experimentally obtained CVs, it is clear that the main features of the CVs are extremely well reproduced. For example, both the magnitude and the position of the first oxidation peak at different hydrazine concentrations are in good agreement. Importantly, the model predicts the appearance of a second voltammetric feature when the hydrazine concentration exceeds a certain threshold. Furthermore, both the position and the absolute magnitude of the second feature are reproduced reasonably by the simulations (although less well than that of the first feature), demonstrating that the occurrence of a second peak can be explained through the simple kinetic model employed here. So how does the interfacial pH affect the voltammetric profile, and what role does the buffer capacity play? In order to answer these questions, one needs to take a closer look at the evolution of the interfacial pH during a voltammetric sweep.

Figure 3a shows the interfacial pH as a function of applied potential for the case of a high buffer-to-hydrazine ratio, corresponding to the simulated CVs of 0.5 mM in 50 mM phosphate buffer in Figure 2b-i. In this case the pH starts to decrease at the onset of hydrazine oxidation (ca. -0.45 V). The pH continues dropping as long as the hydrazine oxidation takes place, as the reaction continuously releases protons into the solution, until a quasi-steady state is reached. However, the decrease in pH is limited to only ca. 0.1 pH unit, indicating that in this case the buffer manages to maintain the solution pH as expected. Thus, the 'bulk' concentration of the reacting species in the electrochemical step (N2H4,ad) does not change, and a 'regular' CV is obtained.

At low buffer-to-hydrazine ratio, on the other hand, such as the case for 10 mM hydrazine in 50 mM pH buffer (c.f. Figure 2b-ii), the pH change is much more severe, dropping from the bulk pH of 7.1 to a pH of ca. 2.5 at the most driving potentiallargest driving force (Figure 3b). Not surprisingly, this value agrees reasonably with the value which obtained with a crude calculation based on the reaction stoichiometry: 10 mM hydrazine releases 50 mM protons at the surface. As the buffer contains 25 mM of the basic component, half of the released protons are neutralized by the buffer, leaving a 25 mM concentration of protons (pH 1.6). An implicit assumption in this calculation is that all species (hydrazine, protons and buffer components) have equal diffusivities. As the diffusion of protons is significantly higher than the other species, the surface excess of protons will be diminished, resulting in a somewhat higher pH than the approximate calculation. An important consequence of the large pH change is that the position of the adsorption equilibrium changes, as the concentrations during the reaction, and thus the concentration of the reacting adsorbed species, also changes during the reaction. Initially, as long as the pH remains approximately constant, the CV follows the well-known profile as in the wellbuffered case. However, as the driving force of the reaction is increased, the buffer becomes unable to maintain the pH and the pH drops sharply. This, in turn, causes a drop in the concentration of the adsorbed reactant species (N2H4), giving rise to the first oxidation peak in the voltammogram. At this point, as the potential is further increased, the pH continues to drop, and the resulting voltammogram is a complex interplay between the adsorption equilibrium, changes in equilibrium potential and electrochemical kinetics. Finally, the pH somewhat stabilizes, and application of the potential sweep can again be described using simple electrochemical theory, albeit with a lower concentration of the reactant adsorbed hydrazine., eventually leading to the second oxidation feature.

In both cases, the region in which the local pH differs from the bulk pH (i.e. proton diffusion layer thickness) can extend up to ca. 400 µm into the bulk solution at the highest driving potential (see insets). Thus, conceptually, one can understand the complex voltammetric profile in insufficiently buffered solutions as follows: it essentially comprises two separate voltammetric measurements at different conditions, one at the initial pH of the solution (here, pH 7.1), and one at the surface pH at the end of the voltammetric sweep (here, pH 2.5). The overall voltammetric profile is then approximately the sum of the two separate profiles. Importantly, our findings show that complex voltammetric profile can be fully explained without the need to consider a specific (change in) mechanism for the hydrazine oxidation reaction. This phenomenon is not only manifested in measurements on macroscopic electrodes, where it could be argued that slow diffusional mass transport rates allow the buildup of protons at the electrode surface, but also at high mass transport rates. This is evident from voltammetric profiles recorded at an UME, as shown in Figure 4a. At low hydrazine concentrations (0.5 mM and 2 mM), the voltammograms are sigmoidal in shape, typical for a (reasonable) facile reaction at a microelectrode. The onset potentials are similar to those observed on macroscopic electrodes, and at potentials above ~ -0.2 V a clear, well-defined diffusion limited current plateau is observed. Using the equation for the diffusion limited current at a (disc) UME (ilim = 4nFDCr, where D is the diffusion constant, r is the radius of the UME, and n, F and C are as defined previously), a diffusion constant of 1.0 × 10 -5 cm 2 s -1 can be calculated for hydrazine. This value lies within the reported range for hydrazine, 19,27,33,34 and is typical for small molecules in an aqueous solution. As the hydrazine concentration is increased, the voltammetric profiles start to deviate from the sigmoidal behavior observed at low hydrazine concentrations, eventually giving rise to a second plateau at higher potentials. Previously, the occurrence of a second plateau in the voltammetric profile for hydrazine oxidation at UMEs have typically been attributed to multiple steps in the hydrazine oxidation process, e.g. with the first plateau corresponding to the formation of an intermediate species. 22,35 In this case, one would expect that the ratio of two plateau current would not only be constant, but also correspond to an integer number of electrons for both steps, which is not the case. Additionally, one should take care to select sufficiently wide potential windows for performing voltammetric measurements and ensure a stable steady state current is Please do not adjust margins Please do not adjust margins reached in with a (relatively) low concentration of buffer species, in order to not make (potentially) erroneous conclusions based on what seems to be diffusion limited current plateau. 18,20 We believe a key diagnostic is that the final plateau current should scale linearly with the hydrazine concentration such as in Figure 4a, indicating that the overall reaction stoichiometry remains the same.

Using the model outlined above (with minor adjustments to account for the more complex geometry of a UME measurement), the main trends of the transition from a single voltammetric wave to a signal with multiple plateaus as the hydrazine concentration is increased is well reproduced, both in the position and the magnitude of the voltammetric waves (Figure 4b). This clearly illustrates that the appearance of the second plateau is the manifestation of a change in interfacial pH, equivalent to the second oxidation peak at a macroscopic electrode. Furthermore, our results emphasize the importance of selecting sufficiently wide potential windows for performing voltammetric measurements in insufficiently buffered solutions.

Conclusions

In this contribution, we have highlighted the importance of interfacial pH changes during proton-electron transfer reactions using the case of hydrazine oxidation. We show that an additional oxidation feature can appear in a voltammetric measurements at low buffer-to-hydrazine ratios, such as a second peak on macroscopic electrodes or a second current plateau for UMEs. While it is tempting to interpret the occurrence of new voltammetric features as changes the reaction mechanism, we demonstrate that the main cause is the result of a more trivial consideration. By using a simple model and FEM simulations, we unambiguously demonstrate that the main cause of the appearance of an additional voltammetric feature is the significant pH change at the electrode surface if the buffer capacity is insufficient, due to the protons released by the electrochemical oxidation of hydrazine, causing a progressive shift the adsorption equilibrium of the electrochemically active species. Importantly, as our model only considers a simplified reaction mechanism, without the need to take the role of the electrode material into account, the effect of interfacial pH changes highlighted herein can be generalized to proton-electron transfer reactions which contain a pH dependent preadsorption step, and in which a significant amount of protons (relative to the buffer capacity) are released or consumed. It emphasizes the need to reflect on the buffer capacity of the solution that is employed in a given experiment. This is particularly important in the case of ready-made 'standard' buffers (such as e.g. phosphate buffered saline, which only has 10 mM buffer capacity), as one might not consider the buffering capability of the medium, but rather implicitly assumes it is sufficient. Finally, we advocate caution in interpreting additional voltammetric features in buffered electrode solutions as insights in a reaction mechanism, as we show that the main cause of the occurrence of an additional voltammetric feature can be simply related to interfacial pH changes.

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Figure 1 : 8 |

 18 Figure 1: (a) Schematic representation of the hydrazine oxidation reaction in a buffered medium. (b) Cyclic voltammograms of a macroscopic polycrystalline platinum electrode in a 50 mM phosphate buffer (pH 6.9) in the absence (dashed line) and presence (solid line) of 0.5 mM hydrazine. First voltammetric cycle, scan rate 20 mV s-1. (c) Variation of peak potential and half-wave potential as a function of pH, measured in 0.5 mM hydrazine in 50 mM phosphate buffer solutions.

Figure 2 :

 2 Figure 2: (a) Experimental and (b) simulated cyclic voltammograms for the electrocatalytic oxidation of varying concentrations of hydrazine in a 50 mM phosphate buffer solutions (pH 6.9). First voltammetric cycles, scan rate 20 mV s -1 .

Figure 3 :

 3 Figure 3: Simulated development of surface pH (left axis) and applied overpotential (right axis) during a voltammetric cycle for hydrazine oxidation in a (a) well-buffered (0.5 mM hydrazine in 50 mM phosphate buffer) and (b) poorly buffered solution (10 mM hydrazine in 50 mM phosphate buffer). The arrows indicate the sweep direction. Insets show the pH profile as a function of distance to the electrode at 200 mV.

Figure 4 a

 4 Figure 4 a) Experimental and b) simulated linear sweep voltammograms (LSVs) for the electrocatalytic oxidation of various concentrations of hydrazine in a 50 mM phosphate buffer solution (pH 6.9) on a platinum ultramicroelectrode (r = 5 µm). First voltammetric cycle, scan rate 20 mV s -1 .

This journal is © The Royal Society of Chemistry 20xx J. Name., 2013, 00, 1-3 | 3

Commenté [CR1]:Ep is independent of C(N2H5) for an irreversible electron transfer.

This journal is © The Royal Society of Chemistry 20xx J. Name., 2013, 00, 1-3 | 7

Acknowledgements

The authors acknowledge partial financial support from the European Research Council (ERC) under project number 278801. We wish to thank Prof. Serge Lemay (University of Twente) for general support and Dr. Chang-Hui Chen (University of Warwick) for fruitful discussions.


Narjiss Araba

Alain François-Heude

Price discovery and volatility spillovers in the French wheat market

This study contributes to the literature on the information and volatility transmissions for wheat.

It investigates the relationship between the French spot market of wheat and its futures contract, through the information and volatility transfers that occur between them. The analysis of the price discovery process, i.e. the information flow between both markets is based on daily prices between 2001 and 2018, and applies a vector error correction model (VECM) for the cointegrated price series. The information share, the permanent-transitory and the component share price discovery metrics are then computed to analyze the link between both markets. Our main finding is that the futures market completely dominates the price discovery for wheat, making the French physical market and agricultural producers exposed to the effects that excessive speculation can have. Furthermore, the volatility spillovers between both markets are analyzed from 2010 to 2018 with a bivariate asymmetric quadratic GARCH model and a BEKK model. We find that volatility spillovers from the spot to futures market are stronger than from futures to spot markets.

Introduction

With their futures contracts, futures markets allow producers to hedge against price risks through risk transfer. They also provide information about the spot market, making futures contract an efficient estimate of the spot price. We say that futures contracts facilitate price discovery, the mechanism determining prices. According to [START_REF] Lehmann | Some desiderata for the measurement of price discovery across markets[END_REF], price discovery is the "efficient and timely incorporation of the information into market prices". What is meant by efficient is the avoidance of noise, whereas by timely "the speed at which the information about the fundamental value is revealed" (Janzen & Adjemian, 2017).

In this study, we discuss the relationship between European wheat futures and the French spot market. More specifically, we assess whether Euronext's wheat futures serve as a price discovery vehicle for French spot market movements. In other words, we estimate the proportion of price discovery occurring in wheat futures markets. This topic has attracted much interest and a large number of researchers examined this relationship for different commodities, including agricultural ones, as shown for example in [START_REF] Oellermann | Price discovery for feeder cattle[END_REF] for cattle; [START_REF] Schroeder | Price Discovery and Cointegration for Live Hogs[END_REF] for livestock; [START_REF] Yang | Futures Trading Activity and Commodity Cash Price Volatility[END_REF] for different agricultural commodities; [START_REF] Mattos | Price discovery in thinly traded markets: Cash and futures relationships in Brazilian agricultural futures markets[END_REF] for most commodities; [START_REF] Arnade | The Impact of Price Variability on Cash/Futures Market Relationships: Implications for Market Efficiency and Price Discovery[END_REF] for soybean; [START_REF] Adämmer | Price Discovery in European Agricultural Markets: When Do Futures Contracts Matter? Center for Quantitative Economics[END_REF] for canola, wheat and corn in Europe and [START_REF] Vollmer | Price discovery in the European wheat market[END_REF] for wheat in Europe too. All of the previous studies find that it is mostly cash markets that adjust to futures markets, except [START_REF] Arnade | The Impact of Price Variability on Cash/Futures Market Relationships: Implications for Market Efficiency and Price Discovery[END_REF] who find the same result only for a sub-period of the data. Janzen & Adjemian (2017) study price discovery between European and American wheat futures contract and find that the Chicago market is dominant, Euronext however plays a more important role starting 2010.

To the best of our knowledge, no study has been undertaken on the specific case of the French wheat market, although it is one of the most important ones in western Europe. And since studies show that price discovery is linked to liquidity (Janzen & Adjemian (2017), [START_REF] Grammig | Telltale tails: A new approach to estimating unique market information shares[END_REF] and [START_REF] Yan | A structural analysis of price discovery measures[END_REF]), our study on the French wheat market will enable us to conclude which of the markets is more liquid. Furthermore, in case price discovery takes place in the futures market, a conclusion about how increased speculation affects the spot market will be set; whereas if the contrary occurs and it is revealed that the spot market that dominates, we would conclude that the commercial producers have the bigger hand over financial actors when it comes to influencing the market. On a more practical side, knowing what market influences the other will give an indicator to French wheat producers on what market to look at when deciding on their marketing strategies.

Different measures exist for price discovery, the most widely used being Hasbrouck's information shares (IS) [START_REF] Hasbrouck | One security, many markets: Determining the contributions to price discovery[END_REF], the permanent-transitory decomposition (PT) [START_REF] Gonzalo | Estimation of common long-memory components in cointegrated systems[END_REF], and the component share (CS) [START_REF] Booth | Price discovery in the German equity index derivatives[END_REF], [START_REF] Chu | Price discovery on the S&P 500 index markets: An analysis of spot index, index futures and SPDRs[END_REF], [START_REF] Harris | Security price adjustments across exchanges: An investigation of common factor components for Dow stocks[END_REF]) that is based on Gonzalo and Granger's decomposition. In this study, all the preceding price discovery metrics have been computed. Furthermore, we investigate how volatility is propagated between the spot and futures market of wheat in France. Volatility spillovers can be analyzed between the spot and futures markets as in this article, but also between different commodities, and different countries.

We believe that no volatility spillovers study has been carried out before, in the French or Europen context for agricultural commodities. In China, for the case of wheat and soybean, [START_REF] Liu | Price Discovery in the Spot-Futures Markets: An Empirical Analysis in Chinese Agricultural Products[END_REF], find that volatility spillovers occur from the spot to the futures market, and so did [START_REF] Mahalik | Price discovery and volatility spillovers in futures and spot commodity markets: Some empirical evidence from India[END_REF], [START_REF] Srinivasan | Price Discovery and Volatility Spillovers in Indian Spot-Futures Commodity Market[END_REF] and [START_REF] Chauhan | Market efficiency and volatility spillovers in futures and spot commodity market: The agricultural sector perspective[END_REF] for agricultural markets in India. However, compared to Euronext, these are all emerging futures markets, hence the results can differ.

The rest of the article is organized as follows. Section 2 introduces the methodology followed by the article to reach the conclusions on the price discovery weights for each market, as well as the volatility spillovers parameters. Section 3 presents the specifications and the preliminary analysis of the data used. And finally section 4 shows the results and discusses them. Section 5 gives some concluding remarks.

Methodology

Price discovery

To derive the IS, PT and CS metrics, we first estimate a vector error correction model (VECM), a representation of a cointegrated vector autoregressive model (VAR), that is better suited in the presence of cointegration, i.e. when a market affects the other on the short and long term.

Let p s and p f be the spot and futures prices respectively of the same asset, milling wheat in our case. Both prices are linked by arbitrage strategies, since they represent the price of a futures and its underlying. While the spot price implies the immediate payment and delivery, the futures price comprises additional storing and delivery costs since it entails a delayed payment and delivery. In that respect, they are expected to be cointegrated, meaning that they cannot deviate from each other in the long run. Although there can be some shocks in the short run, they will end up converging to the pre-existing equilibrium. Cointegration between p s and p f can be written as:

𝑝 𝑡 𝑠 = 𝛼 + 𝛽𝑝 𝑡 𝑓 + 𝜇 𝑡 with 𝜇 𝑡 = 𝜌 × 𝜇 𝑡-1 + 𝜀 𝑡 𝜀 𝑡 ~𝒩(0, 𝜎 2 )
In this case, both price series that should not be stationary, can be written as different stationary linear combinations of stationary time series, integrated at the first order [START_REF] Engle | Co-integration and error correction: representation, estimation, and testing[END_REF]. To find the cointegration relationship, we use the two-step [START_REF] Engle | Co-integration and error correction: representation, estimation, and testing[END_REF] procedure that fits the best α and β, and then the best ρ. Only after cointegration has been verified can we fit a VECM model.

Two approaches of fitting a VECM model exist: [START_REF] Engle | Co-integration and error correction: representation, estimation, and testing[END_REF], and Johansen's maximum likelihood estimation [START_REF] Johansen | Statistical analysis of cointegration vectors[END_REF]. For this analysis, we choose the latter method. As detailed in [START_REF] Baillie | Price discovery and common factor models[END_REF] the VECM model can be represented as:

Δ𝑝 𝑡 = 𝛼𝛽′ × 𝑝 𝑡-1 + Γ 1 × Δ𝑝 𝑡-1 + ⋯ + Γ 𝑘 × Δ𝑝 𝑡-𝑘 + 𝜀
Where 𝛼𝛽′ × 𝑝 𝑡-1 translates into the long-term relationship, and ∑ Δ𝑝 𝑡-𝑖 into the short-run term. In addition, α is the error correction coefficient, that represents the speed of adjustment.

In other words, it allows the system to adjust back to the equilibrium. ε is the serially uncorrelated residuals vector.

Once the VECM estimated, we can start deriving the price discovery metrics by first obtaining the vector moving average (VMA) from the VECM equation:

Δ𝑝 𝑡 = Ψ(L) × ε 𝑡
Where L is the number of lags and ε a vector of the price innovations of mean zero and variance matrix Ω. Ψ is the matrix that reveals the impact of the innovations on the price change. This equation can be rewritten as:

Δ𝑝 𝑡 = ε 𝑡 + 𝜓 1 ε 𝑡-1 + 𝜓 2 ε 𝑡-2 + ⋯
Where 𝜓ε 𝑡 is the change is prices that is due to new information.

Integrated, it becomes:

𝑝 𝑡 = Ψ(1) ∑ 𝜀 𝑠 𝑡 𝑠=1 + Ψ * (𝐿)𝜀 𝑡
The matrix Ψ(1) contains the sum of the moving average coefficients, I being the identity matrix: [START_REF] Hasbrouck | One security, many markets: Determining the contributions to price discovery[END_REF] information share can be written as the market j's proportion in the total variance:

Ψ(1) = 𝐼 + 𝜓 1 + 𝜓 2 + ⋯
𝐼𝑆 𝑗 = 𝜓 𝑗 2 Ω 𝑗𝑗 𝜓Ω𝜓 ′
With j=spot or futures; 𝜓Ω𝜓 ′ is the variance of 𝜓ε 𝑡 , and 𝜓 𝑗 the j th element of the matrix 𝜓.

In case Ω is not diagonal, IS is written as:

𝐼𝑆 𝑗 = ([ 𝜓′𝐹 ] 𝑖 ) 2 𝜓Ω𝜓 ′
With FF'=Ω.

An alternative price discovery measure is [START_REF] Gonzalo | Estimation of common long-memory components in cointegrated systems[END_REF] permanent-transitory measure. In their decomposition of the VECM equation, Gonzalo and Granger get a permanent component:

𝑊 𝑡 = 𝛼 ⊥ ′ 𝑋 𝑡
𝑋 𝑡 is decomposed into:

𝑋 𝑡 = 𝐴 1 𝛼 ⊥ ′ 𝑋 𝑡 + 𝐴 2 𝛽𝑋 𝑡 𝐴 1 = 𝛽 ⊥ (𝛼 ⊥ ′ 𝛽 ⊥ ) -1 𝐴 2 = 𝛼(𝛽 ′ 𝛼) -1
We get:

𝑃𝑇 𝑗 = 𝛼 𝑗 𝛼 𝑗 -𝛼 𝑖
Alternatively, [START_REF] Harris | Security price adjustments across exchanges: An investigation of common factor components for Dow stocks[END_REF] propose the component share as a price discovery measure.

They use Gonzalo and Granger's decomposition and obtain as presented by [START_REF] Yan | The Dynamics of Price Discovery[END_REF], the "weighted average of observed prices with component weights":

𝐶𝑆 𝑗 = 𝜓 𝑗 𝜓 𝑗 + 𝜓 𝑖
Each measure has certain drawbacks and we would like to note that the information share cannot be used when there is a strong correlation of the innovations. This happens when prices are observed at a low frequency. However, no study has been carried out on the best sampling frequency. Another advantage of PT and CS over IS, is that they result in a unique price discovery weight, while IS provides a lower and higher bound.

Volatility spillovers

Different multivariate conditional volatility models are available to estimate volatility spillovers, but it is advised to use a model that takes into account the asymmetry of the returns volatility, i.e. when a negative shock has a different effect from a positive one. The model we start with, that is multivariate and asymmetric is the Bivariate Asymmetric Quadratic GARCH model (BaqGARCH), developed by [START_REF] Schmidbauer | News Impact in Bivariate GARCH Models[END_REF] and used by [START_REF] Schmidbauer | Volatility spillovers between crude oil prices and US dollar to Euro exchange rates[END_REF]. This model is in fact a combination of the GJR model [START_REF] Glosten | On the relation between the expected value and the volatility of the nominal excess return on stocks[END_REF] that takes into account the asymmetry but that is univariate, and the BEKK model developed by Baba, Engle, Karft and Kroner and defined in [START_REF] Engle | Multivariate simultaneous generalized ARCH[END_REF] that does not capture asymmetry but that is multivariate.

The BEKK and the BaqGarch models are similar, except the latter has an additional weight function.

The matrix 𝐻 𝑡 is a conditional variance-covariance of a random coefficient autoregressive process, and is given by the BEKK model as:

𝐻 𝑡 = 𝐶 ′ 𝐶 + ∑ 𝐴′ 𝑖 𝜀 𝑡-𝑖 𝜀′ 𝑡-𝑖 𝐴 𝑖 𝑘 𝑖=1 + ∑ 𝐵′ 𝑖 𝐻 𝑡-𝑖 𝐵 𝑖 𝑘 𝑖=1
Where k is the number of lags, C is a triangular 𝑁 × 𝑁 matrix of constants. A and B are also 𝑁 × 𝑁 matrices, but A is the ARCH parameters matrix and B is the GARCH matrix.

On the other hand, the baqGARCH model with its weight function 𝑆 𝑤 is written as:

𝐻 𝑡 = 𝐶 ′ 𝐶 + ∑ 𝐴′ 𝑖 𝜀 𝑡-𝑖 𝜀′ 𝑡-𝑖 𝐴 𝑖 𝑘 𝑖=1 + ∑ 𝐵′ 𝑖 𝐻 𝑡-𝑖 𝐵 𝑖 𝑘 𝑖=1 + ∑ 𝑆 𝑤 𝜀 𝑡-𝑖 Γ′𝜀 𝑡-𝑖 𝜀′ 𝑡-𝑖 Γ 𝑘 𝑖=1
This way, the weight w and the Γ matrix add the asymmetry component to the BEKK model. Details about the computation of the weight function 𝑆 𝑤 can be found in [START_REF] Schmidbauer | Volatility spillovers between crude oil prices and US dollar to Euro exchange rates[END_REF].

Data

Our study aims to analyze first the price discovery mechanism of wheat in France between the cash market on one hand, and futures market on the other, between September 2001 and October 2018, the period in which our sport prices data are available. Second, we attempt to analyze volatility spillovers between January 2010 and October 2018. Our data for the cash market covers the daily prices in the port of Rouen, the first western European port for grain trade [START_REF] Insee ; Janzen | Plus de 460 000 emplois liés à la logistique dans la Vallée de la Seine[END_REF] and is made available online by the National Institution of Agricultural and Sea Products (FranceAgriMer). Strategically located in the north of France, near the productive agricultural areas of Normandie, Picardie and Ile-de-France, it represents 40% of grain exports and 55% of milling wheat and barley exports (Passions Céréales, 2016). Different qualities are available, and we choose the standard quality ("supérieur A2"). As for the futures market, we take Euronext's milling wheat contract n°2, traded as EBM. It is exchanged in large amounts, making it a liquid contract (for 2016, more than 450,3 millions of tons were traded, 16 times the French wheat production of the same year).

The mentioned EBM contract is also considered as a "global price benchmark for the European underlying physical markets" by Euronext [START_REF] Pour L'avenir | The functioning of the futures markets: new regulation, challenge and opportunities[END_REF]. This argument is partially what we aim to clarify, by analyzing the price discovery function between the futures contract and its underlying. Accordingly, we use the settlement prices of milling wheat available on Euronext's website to construct two continuous price vectors, to get rid of any liquidity anomalies due to the expiration effects, also known as Samuelson effects [START_REF] Samuelson | Proof that properly anticipated prices fluctuate randomly[END_REF]. [START_REF] Samuelson | Proof that properly anticipated prices fluctuate randomly[END_REF] noted that during expiration months the traded volumes are low and price movements are irregular, which led him to warn about the volatility creation due to the use of the last day before delivery as the rollover date.

Over the years, the delivery months of EBM's futures contract has seen several changes (Table 1 EBM's delivery dates during the covered period) and omitting the first days of the delivery months by switching to the second nearby contract on the 1 st day of the delivery month, as is often done in similar studies [START_REF] Vollmer | Price discovery in the European wheat market[END_REF][START_REF] Vollmer | Price discovery in the European wheat market[END_REF][START_REF] Adämmer | Price Discovery in European Agricultural Markets: When Do Futures Contracts Matter? Center for Quantitative Economics[END_REF][START_REF] Adämmer | Price Discovery in European Agricultural Markets: When Do Futures Contracts Matter? Center for Quantitative Economics[END_REF] amongst others), will lead to irregularities in the data. Different studies tried to surpass this problem by omitting from the data, the month of delivery [START_REF] Junkus | Weekend and day of the week effects in returns on stock index futures[END_REF], or the last week before delivery (Östermark et al., 1995) and [START_REF] Martikainen | Sequential information arrival in the Finnish stock index derivatives markets[END_REF]. However, the literature produces contradictory results as to the importance of the rollover day on the results. [START_REF] Ma | Rolling over futures contracts: A note[END_REF] find biases according to the day chosen. [START_REF] Carchano | Rolling over stock index futures contracts[END_REF] test this claim and find no significant effect of the rollover day; therefore, they use the last day before delivery as a rollover date. In this article, and in order to keep one data per day, we construct an artificial futures contract with a constant horizon of a 180 days (6 months), which to our knowledge, has not been used before in a similar context.

The new contract that we call forward180 (Fwd180) is continuous and constructed as a weighted mean of the next and second-next contract settlement prices:

𝐹𝑤𝑑180 = 𝑃𝑟𝑖𝑐𝑒 𝜏 1 + (𝑃𝑟𝑖𝑐𝑒 𝜏 2 -𝑃𝑟𝑖𝑐𝑒 𝜏 1 ) × 𝜏 1 -180 𝜏 1 -𝜏 2 (1)
𝜏 1 and 𝜏 2 denote the number of days until the next and second next delivery dates, such that they are the successive immediate lower and upper bounds of 180. This way, an interval containing 180 days is created. For robustness checks of the price discovery measures, we construct the same price vector for 120 days (Fwd120). We end up with a database of 4365 observations for the price discovery part, and 2258 observations for the volatility spillover analysis. First, to help induce homoskedasticity and normally distributed errors, and for ease of interpretation, we take the log of all of our daily prices (the spot and forward prices). We then decompose our data to remove the seasonal component and test for stationarity using the augmented Dickey-Fuller (ADF) test to detect unit-roots, and the Kwiatkowski-Phillips-Schmidt-Shin (KPSS) test for trend stationarity. As displayed in Table 2 Empirical results of the stationarity tests the null hypothesis of the existence of a unit root is not rejected with the ADF test, and the KPSS test show that the prices series are not trend stationary. We also compute the number of differences necessary to make the series stationary and find that they should be differenced once.

Results and discussion

Price discovery

We then examine the short run and long run relationship between the spot and futures prices.

The short run relationship is examined by the Granger causality test. The results that are not

shown in this analysis indicate that both futures prices Granger cause the spot price, which is why we choose to model the spot price as a function of the futures price.

Next, we verify that a cointegration relationship exists, for the long term link, using Engle-Granger's cointegration procedure and find that the spot is cointegrated with both futures prices (Fwd180 and Fwd120). We find that the series are cointegrated Table 3 Cointegration results but the residuals do not seem to be well fitted by the auto-regressive series of order 1 used in the model. Hence the parameters of the residuals (ρ) may not be the best specification.

Since the series are not stationary but need to be differenced once to be so, and are cointegrated (I( 1)), we can estimate two VECM models, using Johansen's approach for both the Fwd180 and Fwd120 with the spot price.

We start by estimating the number of lags by estimating a VAR model using OLS and trying with different lags. We obtain that, for both equations that 6 and 2 lags are optimal. We fit VECM models using the 2 lags, and find that the best models are obtained with 2 lags (best Akaike and Bayesian information criteria (AIC and BIC)). Where ECT is the error correction term; *** denotes significance at a 1% level and ** at a 5% level.

First, we see that the error correction term is negative and lies between 0 and 1 in absolute terms, which entails that the process is converging in the long run, i.e. that the estimated model is stable and a long-run relationship exists between the spot and futures prices. The other coefficients indicate the short-run relationship. To better interpret these results, we plot the impulse response functions, i.e. the response of the spot and futures prices after an impulse on the spot prices to study the dynamics between them.

We see that (Impulse response function for the Fwd120Figure 2) a positive shock on the spot price led to an immediate reaction of the spot price itself, with a 1,45% increase of the spot price fluctuations. It stayed roughly the same, at its maximum level, until the last period. The reaction of the futures price (Fwd120) to the shock on the spot price, is very similar but at a lower magnitude. An increase of the fluctuations of 0.5% initially, until it reached 0.7% at the second period and then stagnated. As for the Fwd180 (Figure 3), the reaction remained similar.

As time passes, the shock does not decay to 0.

Table presents the price discovery metrics and we note a clear domination of the futures market, according to the IS, PT and CS measures between 2001 and the end of 2018. According to the IS measure, the futures market is responsible for between 70 and 99% of price discovery (for both price vectors), that is on average 84.5%. Likewise, the CS and PT measures are of a similar magnitude, and indicate a domination of approximately 93% in favor of futures prices (both price vectors), while the spot prices are responsible of less than 8% of the price discovery. This consistency between the three measures and both price vectors is a sign of the assertive role the futures market plays. It is also in line with the literature findings on the general context of agricultural commodities, where it is mostly the spot market that adjusts to the futures markets, and to the European framework as highlighted by [START_REF] Vollmer | Price discovery in the European wheat market[END_REF] and [START_REF] Adämmer | Price Discovery in European Agricultural Markets: When Do Futures Contracts Matter? Center for Quantitative Economics[END_REF] for Germany. We also study the reaction of the spot prices after a shock in the futures prices with impulse response functions (Figures 4 and5), we find that for both Fwd120 and Fwd180, the response of the spot price is quick and positive. 2017) make an interesting link between price discovery and speculation in their analysis, from which we can draw a commentary regarding our findings. The fact that it is the futures market that determines the efficient price for wheat in France, and not the fundamentals of supply and demand is an important point that implies the extensive role financial actors play.

There is a disagreement in the financial literature on the role played by financial actors compared to commercial producers, especially when it comes to explaining what led to the 2007-2008 price peak of agricultural commodities. It has long been believed that each actor has a specific role in the financial market: commercial producers hedge, and financial agents speculate, hence creating liquidity to the commericals. However, more recent work [START_REF] Guilleminot | Les nouveaux modes d'investissement sur les marchés dérivés de matières premières agricoles[END_REF] undermined this argument by analyzing US commodities markets according to the positions taken by each type of agent (hedgers, index investors and hedge funds). The authors find that it is the hedgers that provide liquidity to index investors that since 2004, when the latter became the first financial participants.

Furthermore, since market liquidity provides more efficient price discovery, we can conclude that the financial market is more liquid than the spot market. This is in agreement with general beliefs on the EBM contract with its important trading volumes and facility to find a trading counterparty.

Volatility spillovers

Computation of returns is necessary to analyze volatility spillovers between both markets. We first compute the spot returns, by taking the difference of the log of the price at time t, and the log of the price at time t-1. We do the same for the futures return with the Fwd180 price

𝑟 𝑗 = log(𝑝 𝑡 𝑗 ) -log(𝑝 𝑡-1 𝑗 )
where j is either the spot or the futures price.

Figure 4 Volatilities

We note from Figure 4 Volatilities that both volatilities have a similar pattern with the spot volatility having higher swings. This might be due to the fact that the futures prices used to compute the volatilities are transformed to get rid of the expiration effect while the spot prices are not.

We also compute the implied volatility for the futures contract volatility (Figure 5) from Euronext's options on milling wheat futures (OBM), as an indicator of the futures volatility during the lifetime of the option. Like for the futures prices, the implied volatility is scaled to have a constant horizon of 180 days. We note that although the implied volatility is higher, both volatilities show a similar trend and coinciding peaks.

Figure 5 Volatilities

Correlation tests of the futures and spot volatilities using Pearson's method give us a correlation of 0.38 for when the futures volatility is computed using the returns, and 0.32 for when it is the implied volatility.

Further analysis of the relationship between both volatilities leads us to test the Granger causality and modelling the conditional volatilities. Before, the returns are deseasonalized, detrended and tested for seasonality. The tests show that both returns are unit root stationary according to the ADF test, and are trend stationary according to the KPSS test.

We first perform a Granger causality test to understand the interdependencies between the returns of the futures and spot markets. We first select the number of lags to be taken into account using a vector autoregressive (VAR) process, and find that 6 is the optimal number of lags. Exploring granger's causality via the Wald test, we find that there is a significant bi-causal relationship between futures and spot markets, since the spot returns Granger cause the futures returns and vice versa. 1995), our asymmetry parameters are not significant. Indeed, the weight parameter w is not significant, and two of the Γ parameters are not significant either. Hence we cannot reject the null hypothesis that there is no asymmetric interaction between spot and futures returns. Consequently, without interpreting the BaqGARCH results, we model the when deciding on marketing strategies. Further, we found that one unit shock in the futures price leads to a quick and positive response of the spot price.

On the other hand, with regards to the volatility spillovers, the results indicate that the innovations in the futures markets affect the spot market and vice versa and that volatility spillovers occur from the futures market to the spot market and vice versa. But the futures market reaction to the innovations and to the volatility of the spot market is slightly higher, even though it is the leading market in terms of price discovery. Therefore, the spot market is also a source of volatility.

The distortions created in the future markets do spill over to the French spot market, where the producers end up with an additional risk transferred through the spot and the futures markets.

Encouraging French wheat producers to use the futures markets can help increase the number of hedgers compared to the speculators, in order to stabilize the prices.

Figure 1

 1 Figure1Price evolution shows the common trend followed by the spot and futures prices, as

Figure 1

 1 Figure 1 Price evolution

Figure 2 Figure 3

 23 Figure 2 Impulse response function for the Fwd120

Table 1

 1 EBM's delivery dates during the covered period

		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
	2001	10/01/01		12/03/01		10/05/01		10/07/01		10/09/01		12/11/01
	2002	10/01/02		11/03/02		10/05/02		10/07/02		10/09/02		11/11/02
	2003	10/01/03		10/03/03		12/05/03		10/07/03		10/09/03		10/11/03
	2004	12/01/04		10/03/04		10/05/04		12/07/04		10/09/04		10/11/04
	2005	10/01/05		10/03/05		10/05/05		11/07/05		12/09/05		10/11/05
	2006	10/01/06		10/03/06		10/05/06		10/07/06		11/09/06		10/11/06
	2007	10/01/07		12/03/07		10/05/07				10/09/07		12/11/07
	2008	10/01/08		10/03/08		12/05/08			11/08/08			10/11/08
	2009	12/01/09		10/03/09		11/05/09			10/08/09			10/11/09
	2010	11/01/10		10/03/10		10/05/10			10/08/10			10/11/10
	2011	10/01/11		10/03/11		10/05/11			10/08/11			10/11/11
	2012	10/01/12		12/03/12		10/05/12			10/08/12			12/11/12
	2013	10/01/13		11/03/13		10/05/13						11/11/13
	2014	10/01/14		10/03/14		12/05/14						10/11/14
	2015	12/01/15		10/03/15		11/05/15				10/09/15			10/12/15
	2016			10/03/16		10/05/16				12/09/16			12/12/16
	2017			10/03/17		10/05/17				11/09/17			11/12/17
	2018			12/03/18		10/05/18				10/09/18			10/12/18

Table 2

 2 Empirical results of the stationarity tests

		ADF	KPSS
	Spot	-2.32***	2.17***
	Fwd120	-2.50***	2.28***
	Fwd180	-2.49***	2.34***

Where *** denotes significance at the 1% level.

Table 3

 3

			Cointegration results
		α	β	ρ
	Spot and Fwd120	0.55***	0.90**	0.96***
	Spot and Fwd180	0.71***	0.86**	0.98***
	Where *** denotes significance at the 1% level, and ** at the 5% level.

Table 5

 5 Stationarity tests for the returns

		ADF	KPSS
	rs	-12.009***	0.0602
	rf	-12.426***	0.3339
	Where *** denotes significance at the 1% level.

Table 6

 6 Granger causality tests for the returnsHowever, the Granger test does not take into account the autoregressive second moment which is why we also analyze the conditional volatility with multivariate conditional volatility models.We start with the BaqGARCH model to capture the asymmetry and find the following results with the t values in parenthesis:

					Hypothesis		Wald statistic p-value
			The spot returns Granger cause the futures returns	28.284	< 2.2e-16
			The futures returns Granger cause the spot returns	2.3512	0.0288
		-0.008 -0.006	0.239 0.046	0.456 -0.662
	C=(	(-) 0.000 -0.003 (-)	) A= ( 0.104 0.422 (-) (0.455)	) B=(	(-) 0.024 -0.126 (-17.843)	)
			(-)	(-)	(2.12)	(8.979)	(-)	(-0.863)
			0.182	0.530
	Γ=(	(2.275) -0.371 -0.188 (8.116) )
		(-12.367)	(-1.39)
	𝑤 = 0.201
	(0.646)
	AIC= -13968.45
	Contrary to Koutmos & Booth's finding regarding the asymmetry of volatility transmission in
	a stock market context (

conditional volatility with the Full BEKK model, since it is equivalent to the previous model without asymmetry parameters, but also because the AIC value of the BEKK model is better.

The matrices of the fitted BEKK model are the following, with the t values in parenthesis: C=( -0.005 -0.006 (-5.556) (-9.677) 0.000 -0.007 )

AIC=-13986.56

The first row of all the matrices is for the futures market while the second row is for the spot market. Similarly, the first column is the futures market's column and the second is the spot market's one.

We first start by examining the matrix A, more precisely its squared elements. They correspond to the ARCH parameters, meaning the volatility's response to the squared standardized residuals of the markets [START_REF] Mohammadi | Return and volatility spillovers across equity markets in mainland China, Hong Kong and the United States[END_REF]. The element (1,1) becomes 0.056 when squared, implying that the response of the futures market volatility to its own innovations is estimated to be 0.056. Likewise, the response of the spot market to its own innovations (squared element (2,2)) is 0.162. The off-diagonal parameters of matrix A tell us more about the response of one market to the innovations of the other market. Thus the response of the futures market's volatility to the shocks from the spot market (squared element (2,1)) is 0.007, and the response of the spot market's volatility to the shocks from the futures markets is 0.025.

On the other hand, the GARCH parameters matrix (matrix B) tell us about the past volatilities effect on the volatilities. We obtain that the response of the futures market to its own past volatility is 0.324, the response of the spot market to its own past volatility is 0.074, the response of the futures market to past spot market's volatility is 0.174, and the response of the spot market to past futures market's volatility is 0.138.

In light of the above and since all parameters are statistically significant (both ARCH and GARCH), we first conclude that the conditional variances of both markets are impacted by their own previous shocks. The spot market reaction to its own innovation being larger. In addition, the conditional variances of both markets are affected the shocks coming from the other market:

the futures market past shocks affect the spot market and vice versa. However, the spot market's reaction to the futures market shocks is 3.6 times larger. Second, from the GARCH parameters we note that both market respond to their own volatility, as well as to the other market's volatilities. Interestingly, the spot market responds more to the volatility of the futures market rather than to its own volatility.

In other words, the futures market leads the french spot market, yet it is slightly more impacted by the spot volatility. Nevertheless, it is more impacted by its own volatility rather than by that of the spot market, as opposed to the spot market, that has a stronger reaction to the futures volatility rather than to its own.

Conclusion

In this study we examined the relationship between EBM's futures prices and the French spot price for wheat using Hasbrouck's information share (1995), Gonzalo and Granger's permanent-transitory component (1995) and the component share of [START_REF] Harris | Security price adjustments across exchanges: An investigation of common factor components for Dow stocks[END_REF]. The three measures are consistent with eachother and point to the futures market being the price discovery vehicle for the spot market's movement. The complete domination of futures markets translates into the fact that speculation is an important factor in the wheat price determination.

This conclusion is relevant to the agricultural producers who use the futures markets to hedge against price risk, because it implies that futures market is efficient and liquid, yet heavily influences the spot market. And most importantly, since it is not the agricultural producers who play the biggest role in the physical market, they should pay more attention to the futures market