Alexandre Zhao

Rui Huang

Wang

Panda seems like a new "cat" : China's digital panda public diplomacy

Keywords: public diplomacy, public relations, social media, panda, affect

Introduction

The giant panda has become once again the public diplomacy business card of China at the closing ceremony of the 2018 Pyeongchang Winter Olympics. As China's "national treasure," China has used panda's image to promote the 2022 Beijing Winter Olympics. In fact, showing pandas and their images have long been one of the "big ideas" of China's public diplomacy for endorsing its international perception. From Richard Nixon's 1972 visit to China, panda diplomacy practice has entered on the stage of the contemporary Chinese diplomacy.

China's panda diplomacy has gone through four 4 modalities so far: 1) giving giant pandas to foreign governments for diplomatic relations building; 2) sending giant pandas abroad for short-term exhibitions; 3) "leasing" giant pandas to foreign governments; 4) sending giant pandas abroad in the form of scientific research and cooperation.

In the new millennium, the web has been questioned more and more like the "configuration" [START_REF] Rebillard | Le Web 2.0 en perspective: une analyse socio-économique de l'Internet[END_REF] that a large number of actors intend to produce different models (political, economic, statistical, technical, sociological) for exploiting the potential overtures by the network and its applications. Meanwhile, the social media have been seen as a medium within which social relations are conducted (Hirsch & Silverstone,1992) that all urban people live in a mediatized environment, they adopt and combine diverse converging communication technologies and communicative modalities to "perpetually" (Katz & Aakhus, [START_REF] Huang | Twitter: affective sign, image promotion and permanent Chinese diplomat[END_REF]. Panda seems like a new "cat" : China's digital and Panda diplomacy on Twitter: affective sign, image promotion and permanent Chinese diplomat. In EUPRERA 2018 Congress: Big Ideas ! -Challenging Public Relations Research and Practice -Social media. Aarhus.

2 2002) and "multimodally" (Schroeder, 2010) stay connected in their networks. The connectivity and interactivity of social media reinforce the circulation of information and emotion. In fact, emotional signals are elicited by the information should become embedded in the individual's associative memory and thus serve as persisting guides for the future [START_REF] Mackuen | The Affective Signatures of Political News Stories[END_REF]. The rapid transmission of social media enables the frequency of transmission of emotional signals. The Chinese government has also discovered the new blue ocean of its traditional animal diplomacy: using social media to display giant pandas in various forms and to reinforce the interaction with the target audience for stimulating public interest. In fact, on social media platform, such as Twitter, the Chinese state-owned media have advanced to mobilize the cute image and videos of pandas and to adopt a more proactive digital strategy for enhancing the positive perception of "China"

among Internet users in the world as well as circulating information which encapsulated political implications. This achievement could be considered as an attempt by Chinese diplomats to combine its animal diplomacy and public diplomacy with the social network for the sake of the expansion of its international influence and attractiveness.

This paper assesses how China's state-owned media use the image of the panda to serve its public diplomacy. Besides, the Chinese public diplomacy will also be examined in the affective capitalism lenses. In the first part, by using different approaches, we propose a conceptual framework articulating public diplomacy, affective theory as well as capitalism and aiming to guide our field approaches to question China's online panda diplomacy practice.

Second, through the combination of quantitative and qualitative methods, this study attempts to underline the specific practice of Chinese national media in the implementation of Panda diplomacy on Twitter, and its techniques, contents, and strategies will also be demonstrated.

Literature Review: what is China's digital panda public diplomacy?

The concept of public diplomacy is commonly found in the textbooks of political science, international relations, public relations and articles in the media. However, the effort of conceptualization stumbles on the diversity of the practices supposedly covered by these terms and the ideological dimension of their content. In the political science lenses, the public diplomacy, described as "one of the most salient political communication issues" (Snow & Taylor, 2009, p. ix), which participates in the Nation-State's soft power consolidation (Keohane [START_REF] Keohane | Power and interdependence[END_REF][START_REF] Melissen | The new public diplomacy: soft power in international relations[END_REF][START_REF] Van Ham | Power, Public Diplomacy, and the Pax Americana[END_REF] and is regarded as "an instrument that governments use to mobilize soft power resources for communicating with and attracting the foreign publics" (Nye, 2008, p. 95). Since the achievement of public diplomacy missions often needs to be supported by media frameworks or non-governmental communication campaigns, Desmoulins and Huang detected its "track-II diplomacy" feature, namely: "all non-diplomatic contacts and activities which unofficially bring citizens or organizations together" [START_REF] Desmoulins | The Second-Track Diplomacy of French International Relations and Security Studies Think Tankers: Insights on Minor Players of Transnational Mediations[END_REF]Diamond & McDonald, 1991, p. 1) in order to communicate political or diplomatic positions, to establish transnational dialogue, even to exert influence.

Public relations theorists mobilize strategic communication, country image and relation management approaches to refine the primary purpose of public diplomacy. The public diplomacy is considered as a "national communication practice to seek to affect, in a very gentle and hidden way, the foreign public opinions; to manage the nation's diplomatic environment; to construct a positive national image on the international arena; as well as to build a mutual transcultural and transnational understanding" [START_REF] Huang | Polyphonic contents and monophonic core -Comparing Chinese diplomatic Twitter accounts in Ottawa and Brussels for use for public diplomacy[END_REF]. [START_REF] Signitzer | Public relations and public diplomacy: Conceptual covergences[END_REF] identify that both public diplomacy and public relations have similar aims and tools for affecting public opinion. According to [START_REF] Zhong | Public diplomacy meets social media: A study of the U.S. Embassy's blogs and micro-blogs[END_REF], public diplomacy "involves relationship management and public relations tactics intended to effect change in foreign publics" (p. 543). Besides, Gilboa underlines, in a "post-truth" society, public diplomacy as "people to people engagement on common or conflicting national and global interests" (2015).

The term of "public diplomacy" is generally replaced by "wai xuan"(our translation: external propaganda) or "international public relations" in Chinese political and academic discourses. Although western scholars critic the "propaganda" practice as the lack of pluralism of information sources for citizens, the truncated or misleading introduction of political facts and governmental disinformation and censorship (Ollivier-Yaniv, 2010), in China's social dimension, the propaganda refers to the practice of "publicity" or "promotion", and the external propaganda deals with "a positive connotation associated with such essentially benign activities as the release of news, general shaping of ideology, or even advertisement or publicity" (Wang, 2008, p. 259) 4

focuses more and more on the information exchange and public-centric communication [START_REF] Zaharna | Trends[END_REF]. Chinese public relations scholars [START_REF] Chen | Les conceptions stratégiques des relations publiques étatiques sur la diffusion des valeurs fondamentales chinoises (Hexin jiazhiguan chuanbo de guojia gonggong guanxi zhanlve gouxiang)[END_REF][START_REF] Zhou | Du changement de contexte international à la promotion des droits de parole: analyse sur les enjeux des relations publiques nationales de la Chine (cong guoji yujing bianqian dao huayuquan tisheng: shilun zhongguo guojia gongguan de jiyu yu tiaozhan)[END_REF] also recognize this new trend and underline the essential role of international grass-roots level for increasing the government's global perception. They also suggest using social media platforms to establish a direct communication model with target audiences to enhance the effectiveness and coverage of information delivery.

In recent years, some scholars highlight "two revolutionary impulses" in public diplomacy, which are the decisive role of public opinion and the use of digital communication technologies [START_REF] Balzacq | Traité de relations internationales[END_REF]Pahlavi, 2015, pp. 553-565). Indeed, like Britain diplomat Tom Fletcher's metaphor: the "diplomacy is Darwinian" [START_REF] Fletcher | Naked Diplomacy: Power and Statecraft in the Digital Age[END_REF], particularly it's changing in the digital age. In a co-creational perspective, the public diplomacy has already developed from the simple "top-down" to a "two-way dialogic model" (Fitzpatrick, 2007, p. 203) so that publics are seen as "co-creators of meaning and communication as what makes it possible to agree to shared meanings, interpretations, and goals" (Botan & Taylor, 2004, p. 652).

H1. The Chinese government integrates the traditional "panda diplomacy" into the "public diplomacy" practice in social media; this attempt facilitates to enhance the cognitive influence of China's national treasure and to soften China's image in the social network.

The exercise of "animal diplomacy" which, has a long history, is seen as "the use of live native fauna (…) for diplomatic purposes" (Cushing & Markwell, 2009, p. 255). Three fundamental conditions are requested for the success of the animal diplomacy: the animal's visual recognition, its natural distribution, and its introduction to the audiences (Hartig, 2013, p. 55;Xing, 2010, p. 20). However, the most important hallmark of successful animal diplomacy is the animal's image recognition. The more attractive the animal, the more the public exposure in order to arouse the public's positive response, the more successful the animal diplomacy.

The ethologist Lorenz has shown a schema of childlike characteristics (Kindchenschema) in the visual recognition [START_REF] Lorenz | Die angeborenen Formen möglichen Verhaltens[END_REF]. According to him, human beings have feelings for animals with these "juvenile physical configurations": high and slightly bulging forehead, large head, big eyes, round faces, short or stubby limbs. These characteristics trigger the "innate releasing mechanisms" for emotion and nurturance in adults (Jay Gould, 1979, p. 34). When people see an animal which has babyish characteristics, just like pandas which have "a round, rather at face, large black eye patches and a cuddly and clumsy appearance" (Schaller, 1994, p. xvi), people will have some universal reactions:

disarming tenderness automatically, desiring to hug, kiss and protect this innocent animal.

Emotions are "an essential part of the human experience, and they can convey significant messages" (Seaton & Wu, 2018, p. 3). Emotions could be considered as a necessary part of human experience. They can also transmit clear messages. Like Ng and Kidder argued, the emotion is an inseparable component of human's social life, because it organizes the experience of creating and forming cultural meaning [START_REF] Ng | Toward a Theory of Emotive Performance: With Lessons from How Politicians Do Anger[END_REF]. Social media, such as blogs, Twitter, Facebook, and Instagram, has not only speed up organizational and institutional communication due to its flexibility and convenience of communication as long as its limited cost of communication. It has also reinforced symmetrical interaction, dialogues, and engagements in order to shape and alter realities by using the message and emotion.

Beijing is also fully enjoying the conveniences offered by social networks, through Twitter, China operates its official media's accounts for "panda diplomacy." Panda is becoming not only the Chinese tourism, natural, and cultural business card, but also become China's unofficial international political communication medium.

H2. The affective fragments on social media could be capitalized for serving to public diplomacy achieving

The use of social networks faces the balance between the systems that manage devices and the "cognitive systems" of designers and users. Because the Internet can be regarded as a cognitive mechanism that combines different aspects such as attention, information processing, influence, and ideological connections (Pierre & Alloing, 2015, p. 4). According to Martin-Juchat, affects include impulses, emotions, and feelings, the communication is the main channel and the dynamic of objectification and circulation of affects (Martin-Juchat, 2014a, 2014b).

6

In the business community, the two significant aspects of influence and emotion have long been combined with the economy. Like the attention economy, the image of emotional life will be objectified so as to make it a saleable commodity. As Krappi and al. put it, sentiment and capitalism are interrelated and interacted. "In other words, affective capitalism is a broad infrastructure in which the emotional culture and its classed history merge with value production and everyday life" (Karppi, Kähkönen, Mannevuo, Pajala, & Sihvonen, 2016, p. 5).

Being a transversal form, the affective capitalism is described as "the ability of affect to produce an economic effect more swiftly and surely than economics itself means that affect is itself a real condition, an intrinsic variable of the late-capitalist system, as infrastructural as a factory" (Massumi, 2002, p. 45). In affective capitalism system, the production and modulation of emotions, feelings, and reactions are vital for the creating profit (Graefer, 2016, p. 145). This system absorbs and mobilizes the emotional resources of target audiences, because these "inner" resources are not seen as actions, but are inherent in the economically exploited behavior [START_REF] Hochschild | The managed heart: Commercialization of human feeling[END_REF]. The actions evoked by emotional appeals can often go beyond rationality.

The use of affective capitalism could also be mobilized in a variety of ways in the public diplomacy practice, especially for nation branding and place branding. In reality, place branding is linked to nation branding efforts. If the nation branding focuses on using brandbuilding tools to positively alter, confirm or change a country's behavior, attitude, identity or image, the place branding aims at the government's desire to marketing the area and sector in order to achieve economic or political value. Both of these practices in the public diplomacy rely on the persuasive power and attraction. Regarding China's panda digital public diplomacy, if a well-known and loved animal is widely used in different forms (image, gif and video) to circulate diverse information, these practices could create an emotional infrastructure that attracts people and stimulates them.

Method

This paper intends to highlight Chinese State-owned media's panda public diplomacy efforts on Twitter. Our primary research question focuses on Chinese smart practice of public diplomacy by mobilizing the image of pandas on Twitter, to enhance friendly relations with foreign political leaders and people as long as to establish a warm, peaceful and lovely image on international social media.

Concerning the quantitative study, in this paper, the platform Crimson Hexagon (CH)

has been mobilized to collect data. CH is a social media analysis tool that provides researchers with access to the full Twitter firehose. By using CH, researchers can set "Buzz Monitors" and "Social Account Monitors" for data monitor and collection from specific topics or social media accounts.

First, we set a "Buzz Monitor" to monitor and analyze the data about China's panda diplomacy. We utilize the keyword "panda" and apply the authors as the three Chinese mainstream media outlets: Xinhua News Agency (@XHNews), China Global Television Network, or CGTN (@CGTNOfficial), and the People's Daily (@PDChina). The query was established as the following:

"panda AND ((author:(@XHNews OR @PDChina OR CGTNOfficial))

OR ("RT @XHNews" OR "RT @PDChina" OR "RT @CGTNOfficial"))"

By adopting this query, we collected all tweets that include the term "panda" posted by these three Chinese mainstream media organizations and their retweets. A total of 63,434 tweets posted between January 1, 2017, and December 31, 2017, were saved for analysis.

Second, we set three "Social Account Monitors" for observing the three most influential Chinese mainstream media groups (@XHNews, @CGTNOfficial, @PDChina) on

Twitter. The social account monitor allows gathering tweets are corresponding to each specific social media account. By using the filter function, we can receive the original tweets including the word and image of "panda."

The quantitative study is based on a comparative methodology. This observation intends to underline the different subjective attitudes and sentiments of the Chinese government on the panda topic comparing to other hot issues in 2017. Therefore, in this analysis, we chose the "overall opinion of China," the "BRI (Belt and Road Initiative)" and the "19 th National Congress of the Communist Party of China" as the references for this analysis:

For examining the overall opinion of China on Twitter, we set a buzz monitor in CH by inserting the query "China OR Chinese" with the time frame of the complete year of 2017 (January 1 st ,2017, to December 31, 2017). The data collection yielded 100,823,799 tweets. This study based on the CH's sentiment analysis and emotion analysis. As an application of natural language processing, computational linguistics, and text analytics, the sentiment analysis identifies and extracts subjective attitudes of words (positive, neutral, or negative) from the source materials. "It is the computational study of people's opinions, appraisals, attitudes, and emotions toward entities, individuals, issues, events, topics and their attributes" [START_REF] Kharde | Sentiment analysis of twitter data: A survey of techniques[END_REF][START_REF] Ray | Twitter sentiment analysis for product review using lexicon method[END_REF] for discovering the attitude of information publishers. In fact, all tweets gathered were coded by the computer-assisted training algorithm in the analysis tool CH. This tool has already installed the pre-defined sentiment dictionary. By training over 500,000 posts, various linguistic terms have been handlabeled as positive, negative or neutral in the dictionary. In the quantitative observation, we use these labeled terms to "calculate the frequency of distribution of each word, negated word, emoticon, etc. present in those documents across the positive, negative and neutral categories. These frequency distributions are then used to construct a model that analyzes each new post and classifies it by sentiment" (Crimson Hexagon, 2018).

Based on the six emotional characteristics distinguished by Ekman in An argument for basic emotions published in 1992 (p. 180), the emotion analysis of CH allows categorizing all verbatims into one of the following six basic human emotions: anger, fear, disgust, joy, surprise, and sadness. This study provides an additional layer of contextual analysis for discovering China national media's communicational attitude on panda topics.

1 The query of the BRI issue was set as the following: "Belt and Road" OR "One Belt One Road" OR "One Belt and One Road" OR #BeltandRoad OR #OneBeltOneRoad OR #OneBeltandOneRoad OR "#OBOR" 2 The query was set as the following: "((China OR China's OR Chinese) AND ("National Congress" OR "Party Congress" OR "19th Communist Party" OR "7 men" OR "19th CCP" OR "19th CPC" OR "19th Congress" OR "19th National Communist Party Congress")) OR (#19thCPC OR #19thCPCCongress OR #19thNationalCongress OR #19thPartyCongress)". To complete the quantitative research, we adopt a qualitative study in order to observe the discourses, images, videos published by China's national media on Twitter. We focused principally on the top 10 most frequent retweets and the top 10 hashtags as the primary case study for this paper. The qualitative analysis will show the specific practices and strategies of China in digital panda public diplomacy.

Quantitative finding:

Panda related tweets have the highest proportion of positive (14%) and the lowest percentage of negative (1%) in sentiment analysis than other China-related topics studied on Twitter. evident that the panda image has been embedded in a pluralistic discourse system. In this section, by coding and analyzing the verbatims of tweets as well as interpreting the videos and pictures in the tweets, we intend to categorize and summarize different tweets and underline their typologies.

Result: at least four modalities of China's panda diplomacy were discovered during this preliminary study:

1) To publish videos of pandas' daily life, especially some short entertainment videos to show the lovely and cute side of pandas.

Half of the observed tweets use this method to attract more audiences and followers of China's news agencies on Twitter on the one hand, on the other, retweeting these videos by a large number of users allows increasing the influence of these para-diplomatic accounts.

For instance, the most retweeted tweet is the video published by People's Daily (@PDChina) on October 28, 2017: "A clumsy attempt to escape a panda daycare."

(Figure 9. The image of panda on China's national media's Twitter)

In the short 54-second video, the little pandas tried to climb from their proper suitcases to other panda's boxes. Their awkward movements and fascinating interactions between them have attracted at least 206,000 times of viewing. This tweet was retweeted over 3,200 times and received at least 6,190 likes. Besides, in these videos, the intimate interactions between pandas and human beings have been discovered as well, pandas play games with their breeders, or pandas are petting breeders. These images also record the pious and friendly character of the panda in the daily life which have attracted the attention of many netizens.

2) To use panda's image for serving to China's brand building

The panda diplomacy encompasses the "affective capitalism"(Martin-Juchat, 2014b; [START_REF] Pierre | Presented at the La communication numérique au coeur des sociétés : dispositifs, logiques de développement et pratiques[END_REF] for the Chinese brand building: on the one hand, China's news agencies Through the above analysis, the image of panda has already been widely mobilized by the Chinese government in its industrial promotion and national brands. Beijing's media are also trying to use the panda's image to create the added value of communication.

3) Panda is as an "animal diplomat"

In order to enrich the case study, by analyzing top hashtags, we found that pandas are first seen as friendly ambassadors and animal diplomat of China. On Chinese national media's Twitter, pandas are often seen as a bilateral friendly witness to China and other countries.

Three hashtags have been found for serving China's political communication, and diplomatic relation-building: #France (quoted 890+), #XiVisit (quoted 530+) in Germany, #Tokyo (quoted 430+), each hashtag refers to a diplomatic narrative between China and other countries.

For instance, the panda theme tweets related to the #France revolve around the relationship between Yuan Meng, a French-born panda cub, and the French President's family.

While Emmanuel Macron was celebrating his 40 th birthday with his family, he visited this newborn panda cub (see the figure 10), and his wife Brigitte Macron has given the name to this panda and been its godmother 5 . Through the use of different pictures and storytelling, China's official news agencies have established an atypical "diplomatic" interaction with French politicians and people on Twitter. The new-born panda Yuan Meng has become an ambassador who links the relations between China and France.

14

(Figure 10)

4) To tweet panda's information for achieving pedagogical goals

In practice, the Chinese news agencies spread panda's news and knowledge for achieving pedagogic objectives. These tweets which, present some detailed information about panda's life and habits, have also been welcomed by the world audience to know more and more details about panda.

Regarding the French-born panda Yuan Meng, before it was born, the Xinhua News Agency and the CGTN had always been concerned about the situation of its mother. When the panda mother gave birth, the Chinese media Twitter accounts used live tweet for showing and explaining the delivery process of panda. The Chinese reporter has invited a French animal expert to give a "live lecture" about panda's knowledge in the video. This communication action has profound educational implications (see the figure 11). After the panda's cub was born, China's news agencies also paid regular attention to its growth and introduced the biological characteristics of panda through Twitter. This series of efforts shows that China's media not only use the image of the panda for achieving its diplomatic aims, they also intend to spread biological and scientific knowledge as well as to introduce the living environment of giant pandas to the world audiences. This study creates an innovative approach in public diplomacy research field. By using the mixed method of the quantitative and qualitative methodologies, as well as the computerassisted big data analysis, this study shed lights on social media analysis in public diplomacy research.

Through this paper, both quantitative and qualitative analysis confirmed that the Chinese government used the Twitter account of its state-owned media to conduct the emotional influence strategy in the panda diplomacy practice. The universal image of pandas helps Beijing to conquer the vast difficulties of language, politic, ideological and cultural gap (Xing, 2010, p. 22) of China's public diplomacy, therefore, publishing regularly pandas' videos, GIF images and pictures on Chinese official media's Twitter facilitates the government to reach overseas target audiences, especially appealing to young netizens. Regardless of race, cultural background, faiths and nationality, the panda's lovely and babyish image will be deeply rooted in the hearts and minds of people. This practice can also interact with foreign audiences and effectively promote a close picture of China in target countries.

By qualitative analysis of the top tweets and hashtags, we also detected four typologies of China's panda public diplomacy on Twitter: entertaining public to building the attractiveness; using panda's image for achieving add-value; panda as an ambassador for serving to atypical diplomatic interactions; and the pedagogical objectives in panda diplomacy.

The panda diplomacy joins the exercises of affective capitalism to focus on promoting local economy, showing China's branding, and attracting potential foreign tourists, on the one hand, on the other, the hiding objective is to influence foreign governments by affecting their citizens who become China-friendliest (Hartig, 2013, p. 64).

Limitation and Future research

This study is a pilot study of our research plan. The current paper mainly focuses on computer-assisted coding for sentiment and emotion analysis, as well as qualitative analysis of top tweets. The method used in this study is more descriptive than statistical. We plan to add more statistical analysis in future studies. Future studies include but are not limited to: explore more tweets posted by mainstream Chinese media outlets as well as the retweets;

analyze public opinions and reactions; find more innovative methods and approaches in public diplomacy, especially digital public diplomacy research; and compare human coding and computer coding for detecting a valid mixed method for big data analysis in public diplomacy.

Figure 1 .

 1 Figure 1. Sentiment analysis of panda tweets.

Figure 2 .

 2 Figure 2. Sentiment analysis of overall China-related tweets.

Figure 3 .

 3 Figure 3. Sentiment analysis of Belt and Road tweets.

Figure 4 .

 4 Figure 4. Sentiment analysis of 19th National Congress of CPC tweets.

Figure 5 .

 5 Figure 5. Emotion analysis of panda tweets.

Figure 6 .

 6 Figure 6. Emotion analysis of overall China-related tweets.

Figure 7 .

 7 Figure 7. Emotion analysis of Belt and Road tweets.

Figure 8 .

 8 Figure 8. Emotion analysis of 19th National Congress of CPC tweets.

  add an intro caption for highlighting the support China Conservation and Research Center for Giant Panda at the end of each video, this effort intends to promote this Panda Conservation Center based in Sichuan province for attracting more international tourists; on the other hand, the panda's image has been used to show China's achievements in different fields. Two tweets have been found for China's brand building. The tweet published by China Xinhua News (@XHNews) on May 3, 2017 has shown the test operation of the world's 1st new-energy suspension train in China, and the train looks like a panda 3 . Another tweet sent on December 6th which promotes the new high-speed train service from Xi'an to Chengdu, 4 in this tweet, China's news agency invited the world's tourists to choose this service to visit the Giant Panda hometown -Chengdu -by experiencing China's high-speed train and service.

  Huang, Z., & Wang, R. (2018). Panda seems like a new "cat" : China's digital and Panda diplomacy on Twitter: affective sign, image promotion and permanent Chinese diplomat. In EUPRERA 2018 Congress: Big Ideas ! -Challenging Public Relations Research and Practice -Social media. Aarhus. 15 (Figure.11) Discussion This study explores how China used panda public diplomacy to enhance the cognitive influence of China's national treasure and to soften China's image in the social network. It is the first time that large Twitter dataset was used to prove the effectiveness of China's digital public diplomacy.

  [START_REF] Huang | Twitter: affective sign, image promotion and permanent Chinese diplomat[END_REF]. Panda seems like a new "cat" : China's digital and Panda diplomacy on Twitter: affective sign, image promotion and permanent Chinese diplomat. In EUPRERA 2018 Congress: Big Ideas ! -Challenging Public Relations Research and Practice -Social media. Aarhus.

  [START_REF] Huang | Twitter: affective sign, image promotion and permanent Chinese diplomat[END_REF]. Panda seems like a new "cat" : China's digital and Panda diplomacy on Twitter: affective sign, image promotion and permanent Chinese diplomat. In EUPRERA 2018 Congress: Big Ideas ! -Challenging Public Relations Research and Practice -Social media. Aarhus.For the BRI topic, we use the dataset created by[START_REF] Luo | The role of Chinese media in Twitter discussion of China's Belt and Road Initiative[END_REF], which collected tweets relating to the "Belt and Road Initiative" that posted between May 7 and May 22, 2017.This time frame corresponds to the stage for China's Belt and Road Forum in May 2017. A total of 184,687 tweets have been collected 1 .

	For the issue of the 19 th National Congress of the Communist Party of China, we
	mobilize the dataset created by Luo and Wang (2018), which collected tweets relating to 19th
	CPC National Congress that posted between October 11 and October 31, 2017. 2 The tweets
	amassed total 110,690 posts.

  [START_REF] Huang | Twitter: affective sign, image promotion and permanent Chinese diplomat[END_REF]. Panda seems like a new "cat" : China's digital and Panda diplomacy on Twitter: affective sign, image promotion and permanent Chinese diplomat. In EUPRERA 2018 Congress: Big Ideas ! -Challenging Public Relations Research and Practice -Social media. Aarhus.

  [START_REF] Huang | Twitter: affective sign, image promotion and permanent Chinese diplomat[END_REF]. Panda seems like a new "cat" : China's digital and Panda diplomacy on Twitter: affective sign, image promotion and permanent Chinese diplomat. In EUPRERA 2018 Congress: Big Ideas ! -Challenging Public Relations Research and Practice -Social media. Aarhus.

  [START_REF] Huang | Twitter: affective sign, image promotion and permanent Chinese diplomat[END_REF]. Panda seems like a new "cat" : China's digital and Panda diplomacy on Twitter: affective sign, image promotion and permanent Chinese diplomat. In EUPRERA 2018 Congress: Big Ideas ! -Challenging Public Relations Research and Practice -Social media. Aarhus.

Tweet : "World's 1st new-energy suspension train has run for 10,000km in test operation. The futuristic train resembles panda https://t.co/yEIXwpRPA4" (05/02/2017 20:04 @XHNews)


Kouamé Fulgence Koffi
email: fulkoffi@yahoo.fr

Aya Brigitte N'dri

Jean-Christophe Lata

Souleymane Konaté

Tharaniya Srikanthasamy

Sarah Konaré

Marcel Konan

Sébastien Barot

Handling Co-ordinating

Keywords: demographic parameter, fecundity, fire regime, humid savanna, Lamto, mortality, perennial tussock grass, tussock circumference, tussock fragmentation, tussock retrogression

Questions: Perennial tussock grasses represent the principal fuel source for savanna fires, however basic information about the impact of fire on their demography remains scarce. Do dominant perennial grass species differ in their demographic parameters? What is the overall impact of tussock circumference and fire regimes on grass demographic parameters? Do grass species differ in the sensitivity of their demographic parameters to fire regimes and tussock circumference?

Location: The study site is located in the savanna of the Lamto reserve, in the center of Ivory Coast (6˚ 9 to 6° 18 N; 5˚ 15 to 4° 57 E).

Methods: Data on the nine dominant species of tussock grasses were sampled over one year under four fire treatments (early fire, mid-season fire, late fire and no fire). We studied the impact of these fire treatments and tussock circumference on five demographic parameters: mortality, fragmentation (the division of a tussock into several smaller ones), growth, retrogression (the decrease in tussock size) and fecundity.

INTRODUCTION

Fires are critical to the functioning of savannas [START_REF] Abbadie | Environmental constraints on living organisms[END_REF][START_REF] Bond | The global distribution of ecosystems in a world without fire[END_REF]. In particular, fires are used to conserve and sustainably manage savannas by stopping tree encroachment (Case & Staver, 2017;[START_REF] Stevens | Savanna woody encroachment is widespread across three continents[END_REF], which is a common phenomenon occurring world-wide in savannas [START_REF] Archer | Mechanisms of shrubland expansion: land use, climate or CO 2 ?[END_REF]Moleele, Ringrose, Matheson, & Vanderpost, 2002) and could lead to the disappearance of these ecosystems [START_REF] Gillson | Evidence of a tipping point in a Southern African savanna?[END_REF]. In this perspective, different fire regimes are studied to compare their impact on savanna functioning

Accepted Article

This article is protected by copyright. All rights reserved.

to find the most appropriate regime (Case & Staver, 2017;[START_REF] Stevens | Savanna woody encroachment is widespread across three continents[END_REF]. These studies mostly focus on trees [START_REF] February | Influence of competition and rainfall manipulation on the growth responses of savanna trees and grasses[END_REF][START_REF] Gignoux | Establishment and early persistence of tree seedlings in an annually burned savanna[END_REF][START_REF] Smit | An examination of the potential efficacy of high-intensity fires for reversing woody encroachment in savannas[END_REF] with few studies focusing on fire impacts on perennial grasses for which basic demographic information is scarce, especially in West Africa [START_REF] Keeley | Fire as an evolutionary pressure shaping plant traits[END_REF][START_REF] O'connor | Composition and population responses of an African savanna grassland to rainfall and grazing[END_REF].

Perennial tussock grasses generally dominate the herbaceous layer of humid savannas that is the main source of fire fuel [START_REF] Williams | Vegetation[END_REF]. These grasses are adapted to fires. Indeed, their aboveground biomass burns while belowground biomass tends to stay alive [START_REF] Monnier | Les effets des feux de brousse sur une savane préforestière de Côted'Ivoire. Abidjan, Côte d'Ivoire[END_REF][START_REF] Sarmiento | Adaptive strategies of perennial grasses in South American savannas[END_REF], which allows the quick regrowth of tussocks after fire [START_REF] Abbadie | Environmental constraints on living organisms[END_REF][START_REF] Moore | Effects of drought and fire on resprouting capacity of 52 temperate Australian perennial native grasses[END_REF][START_REF] Sarmiento | Adaptive strategies of perennial grasses in South American savannas[END_REF]. Nevertheless, fires and fire regimes likely impact the demographic parameters of grass tussocks: mortality (Zimmermann, Higgins, Grimm, Hoffmann, & Linstädter, 2010), retrogression i.e. decrease in tussock size (Canales, Trevisan, Silva, & Caswell, 1994), growth i.e. increase in tussock size (Yuan, Liang, & Zhang, 2016), fragmentation i.e. the division of a tussock into several smaller tussocks which leads to a form of clonal reproduction [START_REF] Fair | Demography of Bouteloua gracilis in a mixed prairie: analysis of genets and individuals[END_REF][START_REF] Hartnett | The genet and ramet population dynamics of Solidago canadensis in an abandoned field[END_REF], and fecundity [START_REF] Brys | Fire increases aboveground biomass, seed production and recruitment success of Molinia caerulea in dry heathland[END_REF]. Our first goal is to document for perennial grasses the impact of contrasted fire regimes and the absence of fire on these demographic parameters. These parameters are hypothesized to vary with grass species, fire regimes and the interaction between the two, if species have different sensitivities to fire regimes. Testing this broad hypothesis is an important step to choose the best fire regime for the sustainable management of savannas.

Accepted Article

This article is protected by copyright. All rights reserved.

The demographic parameters of tussock grasses also likely depend on tussock circumference, since plant demographic parameters are highly dependent on plant size [START_REF] Caswell | Matrix population models[END_REF] and tussock circumference is considered as a good proxy of their size (Garnier & Dajoz, 2001;[START_REF] Lata | Interactions entre processus mocrobiens, cycle des nutriments et et fonctionnement du couvert herbacé: cas de la nitrification dans les sols d'une savane humide de Côte d'Ivoire sous couvert à Hyparrhenia diplandra[END_REF]. We therefore studied the impact of tussock circumference on the five demographic parameters (see above) and tested interactions between the circumference, fire regimes and species, because tussock circumference might have different demographic impacts in different species and under different fire regimes.

In West African humid savannas, three fire regimes are generally described [START_REF] Bruzon | Les pratiques du feu en Afrique subhumide, exemples des milieux savanicoles de la Centrafrique et de la Côte d'Ivoire[END_REF]N'Dri et al., 2018): (1) Early fires occur at the beginning of the dry season when vegetation is not fully dry, (2) Mid-season fires occur in the middle of the dry season when grass biomass is dry and neither grasses nor trees are growing, (3) Late fires occur at the end of the dry season when trees and grasses have resumed their growth. We analyzed over one year the impact of these three fire regimes and the absence of fire on five demographic parameters (see above) of the nine dominant perennial grass species of the Lamto savanna (Abbadie, Gignoux, Le Roux, & Lepage, 2006) in Ivory Coast. This savanna is a natural reserve and has been managed since 1962 using the mid-season fire. This fire regime negatively impacts the demography of trees in this savanna [START_REF] Gignoux | Spatial pattern, dynamics, and reproductive biology of the grass community[END_REF][START_REF] Gignoux | Establishment and early persistence of tree seedlings in an annually burned savanna[END_REF] and is critical to maintain a savanna ecosystem, i.e. to maintain areas deprived of trees. In turn, this is important to preserve the whole biodiversity of Lamto savanna, which includes forbs growing in the herbaceous layer, and a range of animals (insects, small mammals and larger mammals such as the kob antelope) that all depend on the presence of a grass layer [START_REF] Mishra | More woody plants? the status of bush encroachment in Botswana's grazing areas[END_REF][START_REF] Ritchie | Herbivore effects on plant and nitrogen dynamics in oak savanna[END_REF]. For almost thirty years, some bush encroachment has nevertheless been observed in Lamto savanna, with areas transformed into savanna woodland [START_REF] Dauget | Evolution sur 20 ans d'une parcelle de savane boisée non protégée du feu dans la réserve de Lamto (Côte-d'Ivoire)[END_REF][START_REF] Gautier | Contact forêt-savane en Côte d'Ivoire centrale: évolution du recouvrement ligneux des savanes de la Réserve de Lamto (sud du V-Baoulé)[END_REF]. This justifies testing the impact of the different possible fire regimes on the tree

Accepted Article

This article is protected by copyright. All rights reserved. community of Lamto savanna but it is also important to test whether these fire regimes are not detrimental to the whole grass layer, or to some grass species, therefore threatening grass diversity. We specifically addressed the following questions: (1) How does tussock circumference affect grass demographic parameters? (2) What is the overall impact of fire regimes on grass demographic parameters? (3) Do grass species differ in the sensitivity of their demographic parameters to fire regimes and tussock circumference? (4) What is the fire regime that better maintains grass diversity and abundances?

MATERIAL AND METHODS

Study site description

The study site is located in the savanna of the Lamto reserve [START_REF] Abbadie | Environmental constraints on living organisms[END_REF], in the center of Ivory Coast (6˚ 9 to 6° 18 N; 5˚ 15 to 4° 57 E) where the vegetation is a forestsavanna mosaic, with a tropical humid climate. The average annual rainfall is 1200 mm and the mean annual temperature is 27°C. Mid-season fire has been used for the management of the reserve since 1962. The grass stratum is mostly composed of nine perennial grass species: Andropogon ascinodis C. B. Cl., Andropogon canaliculatus (Schumach.), Andropogon schirensis (Hochst. ex A. Rich), Brachiaria brachylopha Stapf (now Urochloa serrata, [START_REF] Soreng | A worldwide phylogenetic classification of the Poaceae (Gramineae): phylogenetic classification of the grasses[END_REF][START_REF] Sosef | Taxonomic novelties in Central African grasses (Poaceae), Paniceae 1[END_REF], Hyparrhenia diplandra (Hack.) Stapf, Hyparrhenia smithiana (Hook. f.) Stapf, Loudetia simplex (Nees) C.E. Hubbard, Sorghastrum bipennatum (Hack.) Pilg. and Schizachyrium platyphyllum (Franch.) Stapf [START_REF] Menaut | Vegetation[END_REF].

Study plots

Three separate blocks of 3.72 ha each were identified in the shrubby savanna zone. In each block, four plots were established in September 2013 to implement four fire treatments (N'Dri et al., 2018): early fire (in November), mid-season fire (in January), late fire (in March) and no fire (unburned plot). In each of these plots, a plot was delimited to monitor

Accepted Article

This article is protected by copyright. All rights reserved. grass demography. This results in a total of 12 plots (3 blocks × 4 plots) on which data were collected. These plots were 5 x 5-m for early fire, late fire and no fire treatments, and 5 x 10m for the mid-season fire.

Data collection

The first sampling of perennial grasses took place in April and May of 2015 after 2 yrs of implementation of the different fire regimes. All tussocks with more than five tillers were labelled with a fire-proof metal label tied to a metal peg. Pegs were placed at the base of each tussock in the same direction to avoid confusing neighboring tussocks, skipping a tussock or repeatedly counting the same tussock. Grass species were identified using the herbarium of the Ecology Station of the Lamto Reserve. The circumference of each tussock was measured at the soil surface using a measuring tape.

In May and June 2016, all labelled tussocks were retrieved to determine their status, i.e. dead or alive. When a tussock was alive, it was determined whether it was fragmented or not, i.e. whether the tussock was divided in at least two independent tussocks because of the death of groups of tillers. In cases of fragmentation, the number of fragment was recorded, the old peg was given to the principal fragment (i.e. the fragment with the largest circumference) and the other fragments were each labelled with a new peg. New tussocks arising from seed germination were also labeled. These new tussocks were distinguished from fragments of old tussocks due to their very small sizes and the absence of mark of fire at the base of the tussocks (remains of burnt stems). The circumference (cm) of all live tussocks (old live tussocks, tussock fragments and new tussocks) was measured. The difference between the new circumference (in 2016) and the former one (in 2015) was calculated to determine tussocks that had grown (difference > 5 cm), tussocks that had retrogressed (difference < -5 cm) and tussock that had not change in size (-5 cm < difference < 5 cm). The 5 cm threshold was chosen due to the uncertainty in the precise circumference measurement. Finally, fifteen

Accepted Article

This article is protected by copyright. All rights reserved. tussocks of various circumferences were chosen for each species on each plot to count the number of seeds produced from mid-November to mid-March 2016 before each fire regime (depending on the maturation of seeds for each species and plot). The number of new tussocks (deriving from seed germination, as proved by the absence of marks of fire) and the number of seeds produced per tussock were used to estimate fecundity. The fecundity in new tussocks was calculated as the number of new tussocks per adult of the same species in a plot, assuming that all individuals have the same fecundity regardless of their circumference.

Data analyses

All statistical analyses were performed using the 3.1.1 version of the R software. Mixed linear models with the block as random effect were used to account for the dependence of measurements within the same block for variables measured at the tussock scale, i.e. for all variables except the fecundity (measured as a number of seeds). The glmer procedure of the lme4 package was used to test the effects of fire treatments, species, circumference and all interactions between them on tussock probability to die, to become fragmented, to grow (increase in circumference > 5 cm) and to retrogress (decrease in circumference > 5 cm), using a binary logistic regression model. Linear models using lm procedure were used to analyse: (1) the effect of fire treatments and species on the average fecundity measured as the number of new tussocks per adult; (2) the effect of fire treatments, grass species and tussock circumference on the number of seeds produced by tussock (in this case no random effect was used because there was no significant block). The Tukey Honest Significant Difference (HSD) post-hoc test was used to compare the different modalities of factors (fire treatments and species) with a significant effect, using the glht procedure of the multcomp package. The cld procedure was used following Tukey HSD post-hoc tests to group non-significantly different modalities. All tests were achieved with a significance level = 0.05.

Accepted Article

This article is protected by copyright. All rights reserved.

RESULTS

During the first sampling year (i.e. 2015) 5116 tussocks were found on all plots. During the second year (i.e. June 2016) a total of 5355 tussocks were recorded with 797 new tussocks (Table 1). One hundred and ninety tussocks (4% of the tussocks) had become fragmented and 558 tussocks (11% of the tussocks) had died. Fifty percent of the new tussocks were fragments coming from old tussocks, 43% had arisen from seed germination and 6% were small tussocks that had not been tagged the first year. About 34% of alive tussocks had not changed in size (decrease or increase in circumference > 5 cm), 43% had grown (increase in circumference > 5 cm) and 23% had retrogressed (decrease in circumference > 5 cm).

Mortality

Grass mortality decreased with increased tussock circumference (Table 2, circumference effect) from about 30% for the smallest circumferences (3 -10 cm circumference) to 0% for the highest circumferences (about 150 cm) irrespective of fire treatment (Figure 1c) and grass species (Figure 1d). Overall, mortality differed significantly between fire treatments and species (Table 2, Fire treatment x Species). This mortality was significantly higher in the late fire treatment compared to other fire treatments. Mortality was significantly lower for the early and mid-season fire treatments than for the no fire treatment (Tukey HSD test, p < 0.01.

Figure 1a

). Mortality of S. platiphylum was significantly higher than that of any of the other species (Tukey HSD test, p < 0.001. Figure 1b). Andropogon schirensis, H. diplandra and H. smithiana had higher mortality than L. simplex (Tukey HSD test, p < 0.001, p = 0.016 and p = 0.018 respectively. Figure 1b) and A. canaliculatus had lower mortality than A. schirensis (Tukey HSD test, p = 0.002. Figure 1b). The significant effect of the "Fire treatment x Species" interaction on mortality (Table 2) revealed by the glmer suggests that species differed in their sensitivity to fire treatment. The impact of circumference differed between fire treatments (Table 2, significant interaction

Accepted Article

This article is protected by copyright. All rights reserved. between fire treatment and circumference. Figure 1c) and species (Table 2, significant interaction between species and circumference. Figure 1d). Tussock mortality decreased slower with circumference for the late fire and the no fire treatments than for the early and mid-season fire treatments (Tukey HSD test, p < 0.01). Tussock of S. platiphylum revealed more rapid mortality when compared to the tussocks of A. canaliculatus, H. diplandra and H. smithiana (Tukey HSD test, p =0.048; p < 0.001 and p = 0.005). The mortality decreased slower with circumference for A. schirensis than for H. diplandra (Tukey HSD test, p = 0.032).

Tussock fragmentation

Overall, the probability of fragmentation increased with tussock circumference from 0.2 for the smallest circumferences to about 0.8 for the highest circumferences (Table 2, circumference effect) regardless of fire treatment (Figure 2c) and species (Figure 2d). This probability varied with the fire treatment (Table 2, fire treatment effect) and the grass species (Table 2, species effect) and was significantly higher for the late fire (Tukey HSD test, p < 0.01. Figure 2a). The probability was higher for A. ascinodis than for A. schirensis, H. diplandra and L. simplex (Tukey HSD test, p = 0.032, p = 0.014 and p = 0.001 respectively).

Andropogon canaliculatus had a higher probability of fragmentation than H. diplandra and L. simplex (Tukey HSD test, p = 0.046 and p =0.005 respectively. Figure 2b).

Tussock growth

The probability of tussock growth decreased with tussock circumference (Table 2, circumference effect) from approximately 0.6 for the smallest circumferences to about 0.2 for the highest circumferences (logistic regression, p < 0.05) for all fire treatments (Figure 3c) and all species (Figure 3d). Generally, regardless of the circumference, this probability differed significantly between fire treatments and species. It was higher for the mid-season than for the late fire (Tukey HSD test, p < 0.001. Figure 3a). Schizachyrium platiphylum had

Accepted Article

This article is protected by copyright. All rights reserved. a lower growth probability than all other species (Tukey HSD test, p < 0.01) but B. brachylopha that had a lower growth probability than H. diplandra (Tukey HSD test, p = 0.02. Figure 3b).

The "Fire treatment x Species" interaction had a significant effect on the growth probability (Table 2) showing that species differed in the sensitivity of their growth to the fire treatment.

The impact of circumference differed between fire treatments (Table 2, significant interaction between fire treatment and circumference, Figure 3c) and species (Table 2, significant interaction between species and circumference, Figure 3d). Tussock probability to grow decreased quicker with circumference for the late fire than for the early fire treatment (Tukey HSD test, p = 0.022). This probability decreased with circumference slower for the early fire and no fire treatments than for the mid-season fire (Tukey HSD test, p < 0.001). Tussock growth probability decreased with circumference slower for S. platiphylum than for H. diplandra, H. smithiana, L. simplex and S. bipennatum (Tukey HSD test, p < 0.01) and slower for A. ascinodis and A. canaliculatus than for H. smithiana (Tukey HSD test, p = 0.032 and p = 0.031 respectively).

Tussock retrogression

The probability of tussock retrogression increased with tussock circumference (Table 2, circumference effect) from about 0.1 for the smallest circumference to about 0.9 for highest circumference (logistic regression, p < 0.01) whatever the fire treatment (Figure 4c) and whatever the species (Figure 4d). Overall, this probability differed significantly between fire treatments and species. It was significantly higher for the late fire than for the other fire treatments (Tukey HSD test, p < 0.001. Figure 4a) and was higher for the no fire treatment than for the mid-season fire (Tukey HSD test, p = 0.001). The overall probability of retrogression was significantly higher for S. platiphylum than for A. canaliculatus, A.

Accepted Article

This article is protected by copyright. All rights reserved.

schirensis, H. diplandra and L. simplex (Tukey HSD test, p < 0.01). H. smithiana presented a higher probability of retrogression than A. canaliculatus and H. diplandra (Tukey HSD test, p = 0.02, Figure 4b).

The "Fire treatment x Species" interaction had a significant effect on the retrogression probability (Table 2). The impact of circumference differed between fire treatments (Table 2, significant interaction between fire treatment and circumference, Figure 4c) and species (Table 2, significant interaction between species and circumference, Figure 4d). Tussock probability of retrogression increased slower with circumference for the mid-season fire than for all other fire treatments (Tukey HSD test, p < 0.01). It increased quicker for S. platiphylum and A. canaliculatus than for L. simplex (Tukey HSD test, p = 0.013 and p = 0.042 respectively).

Fecundity

The interaction between fire treatment, species and circumference significantly affected the number of seeds produced by grass tussocks (Table 2). Overall, whatever the fire treatment (Figure 5c) and the species (Figure 5d) the number of seeds significantly increased with tussock circumference (Figure 5d). More seeds were produced by tussock on the no fire plots than on the early and mid-season fire plots (significant fire treatment effect, Table 2 and Tukey HSD test, p = 0.002 and p < 0.001 respectively, Figure 5a). Hyparrhenia smithiana and S. bipennatum produced more seeds than the other species (significant effect of species, Table 2 and Tukey HSD test, p < 0.001, Figure 5b). The "species x fire treatment" interaction was significant (Table 2): S. bipennatum had more seeds in the no fire treatment than in the other fire treatments (Tukey HSD test, p < 0.001). Brachiaria brachylopha did not produce any seed on the early and late fire plots. Loudetia simplex produced more seeds on the midseason fire plots but none on the no fire plots. Schizachyrium platiphylum did not produce any seed on the early and mid-season fire plots. The number of seeds increased quicker with

Accepted Article

This article is protected by copyright. All rights reserved. circumference for the no fire treatment than for the other fire treatments (significant interaction between circumference and fire treatment, Table 2, Tukey HSD test, p < 0.01. Figure 5c). The number of seeds increased quicker with circumference for H. smithiana and S. bipennatum than for the other species (significant interaction between circumference and species, Table 2, Tukey HSD test, p < 0.01. Figure 5d).

The production of new tussocks per adult tussock varied with the species (Table 2, F 8.51 = 4.38; p = 0.0004). Brachiaria brachylopha produced more new tussocks than all the other species (Tukey HSD test, p < 0.05. Figure 6) except S. bipennatum (Tukey HSD test, p = 0.25). The fire treatment and the interaction between fire and species had no effect on grass new tussock production (Table 2, F 24.51 = 1.66; p = 0.06).

DISCUSSION

Tussock mortality

Although tussock mortality was low (11%) in our study compared to values obtained in Namibia (57%) by Zimmermann et al. (2010) or in Argentina (55 -85%) by [START_REF] Pelaez | Effect of fire on perennial grasses in central semiarid Argentina[END_REF], it remained very high compared to that obtained by [START_REF] Gignoux | Spatial pattern, dynamics, and reproductive biology of the grass community[END_REF] in the Lamto savanna. Grass mortality decreased with tussock circumference irrespective of the fire treatment and the species showing that small individuals are more likely to die than larger ones, as reported by other studies that considered basal diameter as a measure of size for grass tussocks (Garnier & Dajoz, 2001;[START_REF] O'connor | Composition and population responses of an African savanna grassland to rainfall and grazing[END_REF][START_REF] Silva | Fire and fire exclusion effects on the growth and survival of two savanna grasses[END_REF]. Overall, this confirms that the size of plant individuals allows predicting their fate [START_REF] Silva | Fire, growth and survivorship in a neotropical savanna grass Andropogon semiberbis in Venezuela[END_REF]. The causes of the death of tussocks are not precisely identified but, most probably, small tussocks are more vulnerable to accidents (e.g. trampling by buffalos in Lamto savanna) and to the exhaustion of resources due to repeated fires burning aboveground biomass and to the competition with larger tussocks. Indeed, small

Accepted Article

This article is protected by copyright. All rights reserved.

tussocks have fewer tillers, lower root biomass, and can therefore store less photosynthates in their roots during the dry season [START_REF] Gignoux | Spatial pattern, dynamics, and reproductive biology of the grass community[END_REF].

The late fire and the no fire treatments caused higher mortality than the mid-season and early fire treatments. This can be explained by the fact that late fire occurs at the beginning of the wet season, when grasses are vulnerable because they have already resumed their annual development cycle. The underground living buds ensuring their survival have already started their development, making them more vulnerable to fire. In turn, this probably makes small tussocks more vulnerable to late fire because they have fewer meristems: these tussocks cannot regrow if all their meristems have been killed and thus die. [START_REF] Silva | Fire and fire exclusion effects on the growth and survival of two savanna grasses[END_REF] obtained similar results with two perennial grass species on a plot burned at the end of the dry season.

The effect of the no fire treatment could be explained by the accumulation of dead aboveground biomass (Zimmermann et al., 2010) that could be detrimental to the resumption of tussock growth at the beginning of the rainy season. Moreover, the absence of fire could exacerbate competition between tussocks and increase the success of larger tussocks [START_REF] Milton | Disturbance, drought and dynamics of desert dune grassland, South Africa[END_REF]. Fire allows the access to light to all tussocks, regardless of their size, at least at the beginning of the dry season, when there is a low aboveground biomass. Conversely, the absence of fire could directly kill small tussocks that have not stored enough photosynthates to grow through the accumulating aboveground dead biomass.

The difference of mortality observed between species confirms that species differ by the effect of tussock size on demographic parameters. The studied grass species can be sorted in three distinct groups according to their tussock circumference i.e. large, medium and small size species [START_REF] Koffi | Effect of fire regime on the grass community of the humid savanna of Lamto, Ivory Coast[END_REF]. In this context, the high mortality of S. platiphylum can be explained by the fact that the species is mostly represented by small tussocks.

Accepted Article

This article is protected by copyright. All rights reserved.

Tussock fragmentation

As found by [START_REF] César | Étude de la production biologique des savanes de Côte d'Ivoire et de son utilisation par l'homme: biomasse, valeur pastorale et production fourragère[END_REF] and [START_REF] Gignoux | Spatial pattern, dynamics, and reproductive biology of the grass community[END_REF], we demonstrated the existence of tussock fragmentation in Lamto grasses. Such fragmentation has already been observed for tussock grass species (Festuca gracillima) in South America [START_REF] Oliva | Demography of grazed tussock grass populations in Patagonia[END_REF], in North American prairies (Schizachyrium scoparium, [START_REF] Butler | Population structure and tiller demography of the bunchgrass Schizachyrium scoparium in response to herbivory[END_REF]), in Australia (Astrebla spp. [START_REF] Orr | Effects of sheep grazing Astrebla grassland in Central Western Queensland. 1. Effects of grazing pressure and livestock distribution[END_REF] and for several other perennial grass species in South Africa [START_REF] Hartnett | The genet and ramet population dynamics of Solidago canadensis in an abandoned field[END_REF][START_REF] O'connor | Composition and population responses of an African savanna grassland to rainfall and grazing[END_REF].

Fragmentation probability increased with tussock circumference. This is consistent with [START_REF] César | Étude de la production biologique des savanes de Côte d'Ivoire et de son utilisation par l'homme: biomasse, valeur pastorale et production fourragère[END_REF] and [START_REF] Oliva | Demography of grazed tussock grass populations in Patagonia[END_REF] who found that larger grass tussocks produced new individuals by fragmentation. The process of tussock fragmentation has never been thoroughly analyzed. Nevertheless, it is clearly due to the death of the tillers in some parts of the tussock. The probability of fragmentation could increase with tussock circumference for at least three reasons. (1) Large tussocks produce more biomass and thus more fuel for fires, which could locally increase fire intensity [START_REF] Lata | Interactions entre processus mocrobiens, cycle des nutriments et et fonctionnement du couvert herbacé: cas de la nitrification dans les sols d'une savane humide de Côte d'Ivoire sous couvert à Hyparrhenia diplandra[END_REF]. However, the probability of fragmentation also increased with tussock size in the no fire treatment. [START_REF] Orr | Effects of sheep grazing Astrebla grassland in Central Western Queensland. 1. Effects of grazing pressure and livestock distribution[END_REF] This suggests that the death of tillers could also be due to a higher competition for water, mineral nutrients and light between tillers in larger tussocks. Tillers from the center of the tussocks would lose this competition because they have less access to light and, maybe, water and mineral nutrients than external tillers. (3) Finally, since tussocks are growing by the production of new tillers at their periphery [START_REF] Lata | Interactions entre processus mocrobiens, cycle des nutriments et et fonctionnement du couvert herbacé: cas de la nitrification dans les sols d'une savane humide de Côte d'Ivoire sous couvert à Hyparrhenia diplandra[END_REF], tillers from the tussock centers are likely to be older and could be senescent, which would increase their mortality.

The probability of tussock fragmentation was higher for the late fire, probably due to the same mechanism that increases mortality in this fire treatment: late fire is more likely to kill tillers that are resuming their growth at the beginning of the rainy season, when only a fraction of tillers dies, fragmentation may occur.

Accepted Article

This article is protected by copyright. All rights reserved.

Andropogon canaliculatus and A. ascinodis had higher probabilities of fragmentation than A. schirensis, H. diplandra and L. simplex, but there was no interaction with fire treatment or tussock circumference. Andropogon canaliculatus was the species that formed the largest tussocks while A. ascinodis possessed medium size tussocks. These two species were opposed to A. schirensis and L. simplex that had small tussocks and H. diplandra that formed large tussocks [START_REF] Koffi | Effect of fire regime on the grass community of the humid savanna of Lamto, Ivory Coast[END_REF] but with fewer large tillers (personal observation). This supports the assumption that tussock fragmentation is influenced by the size and the number of tillers by tussock.

Tussock growth and retrogression

The tussock probability to grow was significantly lower for the late fire regime. This could be explained by the severity of this fire regime [START_REF] Louppe | The effects of bush fires on vegetation: the Aubréville fire plots after 60 years[END_REF]. Such fire regime could prevent tussock growth by killing some tillers. Some authors showed, on the contrary, that the growth of perennial grass tussocks was higher in the case of intensive disturbance [START_REF] O'connor | Composition and population responses of an African savanna grassland to rainfall and grazing[END_REF]Yuan et al., 2016). According to them, the late fire should rather stimulate tussock growth by reducing aboveground biomass, subsequently reducing competition and increasing light availability (Zimmermann et al., 2010). The stronger negative impact of the late fire, that does not have a higher intensity than the other fire regimes in Lamto savanna (N'Dri et al., 2018), is likely explained by the fact that grass tussocks have resumed their growth at the moment of late fire, so that late fire as a stronger negative impact on growth (and other demographic parameters, see above).

Tussock probability to grow decreased with circumference whatever the fire treatment and the species. Indeed, the larger a tussock is, the less resource (water, mineral nutrients, light) becomes available because the local tiller density increases, which likely increases competition between tillers and decreases the capacity to grow new tillers. In comparison to the mid-season fire, the absence of fire can also be detrimental to tussock growth as shown by

Accepted Article

This article is protected by copyright. All rights reserved. Garnier and Dajoz (2001) or [START_REF] Loydi | Effects of litter on seedling establishment in natural and semi-natural grasslands: a metaanalysis[END_REF]. For these authors, the accumulation of unburned litter could reduce the growth of seedlings that have lower access to light. There were small differences between species in their probability to grow. For example, S. platiphylum had overall a lower probability to grow that is only weakly sensitive to tussock size. On the contrary, A. ascinodis had a higher overall probability to grow than other species and this probability was high whatever the tussock size. This is consistent with the observed differences in tussock size between species [START_REF] Koffi | Effect of fire regime on the grass community of the humid savanna of Lamto, Ivory Coast[END_REF]. Schizachyrium platiphylum generally formed small tussocks with few thin and short tillers (personal observation). Due to competition with taller tussocks, this could prevent S. platiphylum tussocks from absorbing enough light and from producing new tillers to enlarge their tussocks. On the contrary, A. ascinodis had many tall tillers (personal observation), which could facilitate the accumulation of resources that can be used to grow more tillers and enlarge its tussocks (Fetcher & Shaver, 1982).

The probability of tussocks retrogression increased with tussock circumference.

Retrogression is due to the death of tillers, especially at the periphery of tussocks (Canales et al., 1994). Our result would again be due to a decrease in resource availability with tussock size, or maybe to a local increase in fire intensity with tussock biomass, as for fragmentation.

The retrogression of tussocks was significantly more likely for the late fire than for the other fire regimes, certainly due to the same mechanism explaining the lower growth and higher mortality of tussocks for this fire regime.

The probability of retrogression was significantly higher for S. platiphylum than for A. canaliculatus, A. schirensis, H. diplandra and L. simplex, and H. smithiana presented a higher probability of retrogression than A. canaliculatus and H. diplandra. This is consistent with the fact that S. platiphylum and H. smithiana had on the average small tussocks (Koffi et

Accepted Article

This article is protected by copyright. All rights reserved. al., 2019): higher rates of retrogression tend to lead to small tussocks. As for the effect of tussock size on growth, this could be explained by the lower capacity of resource accumulation of the smaller tussocks.

Fecundity

The number of seeds per tussock significantly increased with tussock circumference. Garnier & Dajoz (2001) obtained similar results with H. diplandra in both burned and unburned plots of the Lamto savanna. This confirms that for plants, size strongly influences fecundity [START_REF] Watkinson | Some life-history consequences of modular construction in plants[END_REF][START_REF] Weaver | Reproductive effort of two perennial weed species in different habitats[END_REF] and suggests that this relation between plant size and plant fecundity is linear [START_REF] Rees | Growth, reproduction and population dynamics[END_REF]. This is due to the fact that larger tussocks have more tillers, can produce more biomass and, everything else being equal, more seeds.

More seeds per tussock were produced in the no fire than in the early and mid-season fire treatments. This could be due to the return of more dead biomass and mineral nutrients to the soil in the absence of fire, because fires lead to the loss of the aboveground biomass and an important fraction of the mineral nutrients it contains (N'Dri, Kone, Loukou, Barot, & Gignoux, 2018). This is in agreement with [START_REF] Crowley | Seeds of the annual grasses Schizachyrium spp. as a food resource for tropical granivorous birds[END_REF]. However, [START_REF] Brys | Fire increases aboveground biomass, seed production and recruitment success of Molinia caerulea in dry heathland[END_REF] found that seed production was two times higher and seedling density six time higher in burned than in unburned savanna plots. Several other grass species have also been shown to produce more seeds in burned plots (Canales et al., 1994;Garnier & Dajoz, 2001). The reason for these contrasting results remains unclear. The absence of difference between the no fire and late fire treatments could be explained by the fact that, tussocks have the same time to produce and mature seeds in these treatments. While tillers stop growing during the dry season, some leaves remain green during at least a part of this season, which likely favors seed feeling and maturation till the death of aboveground biomass at the end of the dry season or due to fire, i.e. in March in the late and no fire treatments. Moreover, the number of seeds

Accepted Article

This article is protected by copyright. All rights reserved. increased quicker with circumference for the no fire treatment than for the other fire treatments. This is likely due to the increased competition for light in the no fire treatment and the fact that this treatment favors large tussocks.

Hyparrhenia smithiana and S. bipennatum produced more seeds per tussock than the other species and their number of seeds increased quicker with circumference. As seen above, these two species are among the ones with the lowest probability of fragmentation and the smallest tussocks [START_REF] Koffi | Effect of fire regime on the grass community of the humid savanna of Lamto, Ivory Coast[END_REF]. This suggests that small size species reproduce less by fragmentation but more by seeds likely explaining why these two species invest more in seed production relatively to their size. In particular, seed production might decrease in a fire treatment because it requires a particular timing from flower development to seed filling and because this timing is disturbed by fire [START_REF] Brys | Fire increases aboveground biomass, seed production and recruitment success of Molinia caerulea in dry heathland[END_REF][START_REF] Silva | Phenology, seed crop and germination of coexisting grass species from a tropical savanna in Wester Venezuela[END_REF]. This could be for example the case for B. brachylopha in the early and late fire treatments, and S. platyphyllum in the early and mid-season fire.

The production of new tussocks by seed germination varied with the species but not with the fire treatment. Such effects should depend on differences in seed production, seed germination or seedling survival and growth [START_REF] Brys | Fire increases aboveground biomass, seed production and recruitment success of Molinia caerulea in dry heathland[END_REF]. In our case, B. brachylopha produced more tussocks and fewer seeds than H. smithiana and S. bipennatum. This suggests that B. brachylopha has a higher germination rate or higher seedling survival rate than H. smithiana and S. bipennatum. In turn, this suggests that the seeds and seedling of B. brachylopha are more adapted to fire than H. smithiana and S. bipennatum. Testing further these hypotheses would require monitoring seed germination and the dynamics of young seedlings in the different fire treatments.

Accepted Article

This article is protected by copyright. All rights reserved.

Conclusion

In the humid savanna of Lamto, the grass species differ by their demographic parameters and the sensitivity of their demographic parameters to both fire regimes and tussock circumference. Overall our results confirm that the most benign fire treatment for grasses is the mid-season fire treatment. This treatment, which has been applied for more than 50 years in Lamto savanna, is likely to maintain the highest diversity of perennial grasses because it is not particularly detrimental to any of their dominant species. Outside the Lamto reserve, due to farmer activities, the fire often burns savannas before the period of the mid-season fire (i.e. mid-January). Because of an absence of fire-break around the Lamto reserve, these fires often also burn the reserve savanna, disturbing the prescribed mid-season fire regime. However, our results show that such perturbations and the early-fire regime are not too detrimental to the demography of perennial grasses. On the contrary, the late fire regime would likely decrease the abundances of all perennial grass species and should be avoided to maintain the integrity of the grass community. Nevertheless, the late fire is likely the fire regime that has also the stronger negative impact on tree demography because, as for grasses, tree saplings and seedlings resume their growth at the beginning of the rainy season and are likely more vulnerable to fire [START_REF] Laris | The early/late fire dichotomy: time for a reassessment of Aubréville's savanna fire experiments[END_REF]. This would suggest that maintaining at the same time savanna structure (the tree grass equilibrium) and the grass community would require alternating mid-season and late fires.

New results are required to test the long term impact of fire regimes on grass biomass and the abundance and diversity of forbs [START_REF] Abella | Ten years of vegetation assembly after a North American mega fire[END_REF]. To predict the long term consequences of the fire regimes on the relative abundance of the different grass species, it is necessary to integrate all demographic parameters within the same framework. This will be achieved using our data to parameterize matrix population models [START_REF] Caswell | Matrix population models[END_REF]. Such models could predict the effect of the date and frequency of fires on the grass community.

Accepted Article

This article is protected by copyright. All rights reserved.

Accepted Article

This article is protected by copyright. All rights reserved. Otherwise same legend as for Fig. 1.

FireFigure 1 :

 1 Figure 1: Tussock mortality as a function of fire treatment, grass species and tussock

Figure 2 :

 2 Figure 2: Fragmentation of tussocks as a function of fire treatment, grass species and tussock

Figure 3 :

 3 Figure 3: Tussocks growth as a function of fire treatment, grass species and tussock

Figure 4 :

 4 Figure 4: Tussock retrogression as a function of fire treatment, grass species and tussock

Figure 5 :

 5 Figure 5: Seed production by tussock as a function of fire treatment (a), grass species (b) and

Figure 6 :

 6 Figure 6: Fecundity measured as the number of new tussocks per tussock of the same species

Table 1 :

 1 Abundance and proportion of perennial grasses on all plots the first and second years of study (overall tussocks).

	Species	Abundance the first year	Proportion the first year (%)	Abundance the second year	Proportion the second year (%)
	Andropogon ascinodis	105	2	116	2
	Andropogon canaliculatus	1588	31	1842	34
	Andropogon schirensis	494	10	494	9
	Brachiaria brachylopha	81	2	127	2
	Hyparrhenia diplandra	1351	26	1326	25
	Hyparrhenia smithiana	188	4	176	3
	Loudetia simplex	777	15	823	15
	Sorghastrum bipennatum	294	6	282	5
	Schizachyrium platyphyllum	238	5	169	3

Table 2 :

 2 Tableshowing(1) the χ² values of binary logistic regressions analyzing the effect of fire treatment, grass species, tussock circumference and two and three way interactions the interactions on tussock probability to die, to become fragmented, to grow and to retrogress using the glmer procedure, (2) the F values for linear regression analyzing the effect of fire treatment, grass species, tussock circumference and two and three way interactions on the number of seed produced by grasses and the production of new tussocks using the lm procedure. Only significant effects are displayed: ***, P < 0.001; **, P < 0.01; *, P < 0.05.

	df: degrees of freedom.
	Explained variables	Explanatory variables	Procedure used	Value of the statistic	df	p-value
		Circumference		χ² = 212.43	1	***
		Fire treatment		χ² = 435.67	3	***
	Tussock mortality	Species Circumference × Fire treatment Circumference × Species	glmer	χ² = 128.55 χ² = 11.13 χ² = 33.63	8 3 8	*** ** ***
		Fire treatment × Species		χ² = 104.1	23	***
		Circumference		χ² = 149.95	1	***
	Tussock fragmentation	Fire treatment Species	glmer	χ² = 31.79 χ² = 33.92	3 8	*** ***
		Circumference		χ² = 98.81	1	***
		Fire treatment		χ² = 167.52	3	***
	Tussock growth	Species Circumference × Fire treatment Circumference × Species	glmer	χ² = 88.74 χ² = 59.1 χ² = 18.85	8 3 8	*** *** *
		Fire treatment × Species		χ² = 62.13	23	***
		Circumference
		Fire treatment
	Tussock retrogression	Species Circumference × Fire treatment Circumference × Species
		Fire treatment × Species

ACKNOWLEDGMENTS

This publication was made possible thanks to the PhD grant provided by the Direction of Research and Training in the South of the Institute of Research for Development (IRD-DPF).

This study was conducted within the project ''Integrated and Sustainable Management of Savannah Ecosystems'' financed by IRD within the "Young Associated Team" program (JEAI-GIDES) and was helped by the French national program EC2CO MicrobiEn 2014 (project: Impact de la diversité des Graminées et ligneux de savane sur la diversité microbienne et le fonctionnement des sols) and the Sorbonne Université programme Emergence 2016 (project: SU-16-R-EMR-37-WASCINNI). We thank Yéo Kolo, the Director of the Ecology Station of Lamto, where this study had taken place. We thank all students (particularly Drissa Soro, Prospère Kpangba, Louis N'Guessan, Evelyne Kouakou, Sylvain Yoboué and Jean-Noël Kpré) who helped during data collection.

This publication was made possible thanks to the PhD grant provided by the Direction of Research and Training in the South of the Institute of Research for Development (IRD-DPF) to K. F. Koffi

Accepted Article

This article is protected by copyright. All rights reserved.

Finally, the mechanisms explaining the differences between species are so far largely unknown. They could be determined by further analyzing the grass species traits: the use of mineral nutrient, water and photosynthesis efficiency, phenology, classical root and leaf traits [START_REF] Violle | Let the concept of trait be functional![END_REF].

Data Availability Statement: Our raw data are now available to the scientific community on the Mendeley repository website at: http://dx.doi.org/10.17632/jvx4f5gt6t.1

Accepted Article

This article is protected by copyright. All rights reserved.

LITERATURE CITED

Abbadie, L., Gignoux, J., Le Roux, X., & Lepage, M. (Eds.). ( 2006). Lamto : structure, functioning and dynamics of a savanna ecosystem. Retrieved from http://www.documentation.ird.fr/hor/fdi:010039255 Accepted Article This article is protected by copyright. All rights reserved. Fetcher, N., & Shaver, G. R. (1982). Growth and tillering patterns within tussocks of Eriophorum vaginatum. Holarctic Ecology, 5(2), 180-186. https://doi.org/10.1111/j.1600-0587.1982.tb01034.x Garnier, L. K. M., & Dajoz, I. (2001). The influence of fire on the demography of a dominant grass species of West African savannas, Hyparrhenia diplandra. Journal of Ecology, Accepted Article This article is protected by copyright. All rights reserved. Yuan, J., Liang, D., & Zhang, S. (2016). Litter and its interaction with standing vegetation affect seedling recruitment in Tibetan alpine grasslands. Plant Ecology & Diversity, 9(1), 89-95. https://doi.org/10.1080/17550874.2015.1073400 Zimmermann, J., Higgins, S. I., Grimm, V., Hoffmann, J., & Linstädter, A. (2010). Grass mortality in semi-arid savanna: the role of fire, competition and self-shading. Perspectives in Plant Ecology, Evolution and Systematics, 12(1), 1-8. https://doi.org/10.1016/j.ppees.2009.09.003

Accepted Article

This article is protected by copyright. All rights reserved. Canales, J., Trevisan, M. C., Silva, J. F., & Caswell, H. (1994). A demographic study of an annual grass (Andropogon brevifolius Schwarz) in burnt and unburnt savanna. Acta Oecologica, 15(3), 261-273. Case, M. F., & Staver, A. C. (2017). Fire prevents woody encroachment only at higher-thanhistorical frequencies in a South African savanna. Journal of Applied Ecology,54(3),