Maxime Cailleret

Hendrik Davi

Annabelle Amm

Sabrina Rachedi

Forest vulnerability to climate change

niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Forest vulnerability to climate change: example of the silver fir-beech community forest at its southern Alps margin

Maxime Cailleret*, Hendrik Davi, Annabelle Amm, Sabrina Rachedi URFM, Ecologie des Forêts Méditerranéennes, INRA Avignon,84914 Avignon,.02 -E-mail: maxime.cailleret@avignon.inra.fr Forest growth in Mediterranean mountains is limited by two major factors: summer drought at low elevation and low temperatures at high altitude (Korner 2007). As a consequence of climate change, observed trends would be the consequence of the contradictory effects of reduced frost and increased drought (Badeck et al. 2004;Jump et al. 2006). We chose a model ecosystem where both warming and drought trends will be measurable: the silver fir-beech community (Abieto-Fagetum) forest at its southern Alps margin. Using dendroclimatological data, growth differences along an altitudinal gradient, recent growth trends, and analysis of the spatial variability of the tree health, the objective of our works is to better understand the effects of climate change on the growth and the resistance of co-occurring trees. Climate-growth relationships show that silver fir is more sensitive to summer drought than beech, which is confirmed by a growth optimum at higher altitude. Common beech is more sensitive to climate events (2003 heat-wave and late frost), due to the non-persistence of its leaves. Forest productivity is positively affected by global change. But with the recent warming (0.6°C to 0.7°C by decade since 1960 in South-eastern France) and accumulation of summer drought, an upward shift in altitude of growth optima is already noticed and is higher for silver fir than for common beech. In the study area, rising temperatures and decreasing rainfalls (4-27%) are predicted (IPCC 2007). These growth trends would logically go on. At low elevation silver fir is declining with a high spatial variability which depends on tree characteristics (age, height, climatic sensitivity, past growth...), abiotic conditions (superficial and deep soil, stand composition, microclimate, and altitude) and biotic factors (pathogens). Beech vitality should be less affected except if heat-waves increase in intensity and frequency as expected (Meehl and Tebaldi 2004). At high elevation, the upward shift of beech would be limited by late frosts damage contrary to silver fir which would take advantage of higher carbon assimilation due to rising temperature and lengthening of the growing season.

To conclude the decline / resistance of forest to climate change is a complex process which depends on species-specific effects, and on site characteristics, and which needs an interdisciplinary approach to be understood. It also shows that the frequency and intensity of extreme events must be taken into account, because of their effects differ between cooccurring species.


domain: math info sdv

text:
Anne Goelzer

Catherine Tanous-Healy

G Scorletti

Vincent Fromion

come

Growth rate reflects a bottleneck on the resource sharing between cellular processes

Title:

Growth rate reflects a bottleneck on the resource sharing between cellular processes

Authors & affiliations:

A. Goelzer *12 , C. Tanous 1 , G. Scorletti 2 , V. Fromion The growth rate should be a highly optimized process in bacteria since the battle for the conquest of ecological niches is tough. Understanding the main elements governing the growth rate management is crucial to further understand and predict the bacterium behaviour with respect to various environmental conditions. Constraint-based approaches integrating the whole metabolic network of an organism such as Flux Balance Analysis successfully predicted the maximum growth rate reachable in various conditions [1]. However, they fail to predict a number of commonly observed metabolic strategies.

Here we showed that the sharing of resources between the cellular processes intrinsically and structurally limits the growth rate [START_REF] Goelzer | IEEE Conference on Decision and Control[END_REF]. We formalized the problem of resource repartition at the cell scale as an optimization problem and demonstrated the existence of a trade-off for the protein repartition between the translation apparatus and the metabolic network. Moreover, the resolution of this optimization problem for Bacillus subtilis allows the estimation for a given medium composition of (i) the maximal growth rate reachable; (ii) the concentrations of ribosomes, the concentration of proteins involved in the metabolic network and more generally the resource repartition between cell components; (iii) the flux distribution. Besides, we also predicted the induction and repression of metabolic sub-systems with respect to the environmental condition which correspond to the recently identified elementary modules of Bacillus subtilis [START_REF] Goelzer | [END_REF]. Finally we also recovered the well-known evolution of ribosomes and metabolic proteins with respect to the growth rate of the Copenhague school [4].

The proposed method, named ``Resource Balance Analysis'' (RBA), thus constitutes a powerful tool to explore many biological aspects such as the amino acid composition of enzymes, the codon usage or the emergence of structured genetic regulations. Moreover, RBA should be helpful to evaluate the impact of genetic modifications in the context of synthetic biology.


domain: sdv sde

text:
Felix D Dakora

Samson B M Chimphango

Alex J Valentine

Claudine Elmerich

William E Newton

J J Drevon

S Gugliemni

G Boyer

E Lafosse-Bernard

) R Métral

C Pernot

John Howieson

E Danckwerts

I Ndoye

M Gueye

S Sylla

S Mpepereki

Zimbabwe Karanja

Mali Yattara

L Thiombiano

Ghana Fao

S K A Danso

D Lesueur

M Neyra

IITA R Abaidoo

Nigeria Beki

D Odee

Senegal M M Spencer

R Dixon

Z M Dong

Canada Emerich

R Haselkorn

M Hungria

R J Campo

F G Barcellos

L M O Chueire

P Menna

R M Boddey

C P Jantalia

L Zotarelli

A Okito

B J R Alves

Chemical Manufacturing Consumer Packaged Goods Pharma Editors

Keywords:

Measuring N 2 fixation in legumes using 15 N natural abundance: Some methodological problems associated with choice of reference plants How to quantify biological nitrogen fixation in forage legumes in the field Nodular diagnosis for integrated improvement of symbiotic nitrogen fixation in cropping systems Evaluation of seed and liquid inoculation on biological nitrogen fixation and grain yield of soybean Initiation, localization, and growth of nodules within the root system of pea as affected by assimilate availability Enhanced early nodulation of Medicago truncatula co-inoculated with Sinorhizobium medicae and Achromobacter xylosoxidans x

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Estimates of N 2 fixation in cowpea grown in farmers' fields in the upper west region of Ghana J. B. Naab, S. B. M. Chimphango and F. D. Dakora . . . . . . . . . . . . . . . . . . . . . . . . . . 109 The alternative sigma factor rpoH2 is required for salt tolerance

The commercialisation of small holder agriculture through biological nitrogen fixation (BNF) He was involved in the implementation of five Biotechnology Education and Training Centres (BETCEN), one on each continent. The MIRCENs and BETCENs proved to be very successful and offered training to young scientists from developing countries as well as opportunities for international cooperation. He developed fellowship programs for research and training both within UNESCO's biotechnology program and also with partners like the American Society for Microbiology (ASM) and the International Union of Microbiological Societies (IUMS). One of his ambitions was that research carried out in developing countries should be recognized and given the necessary support. To this end, in 1985, he was instrumental in the launch of a journal, which is now published by Springer as "World Journal of Microbiology and Biotechnology". Edgar wrote numerous articles and reviews for many journals, especially those in the fields of microbiology and biotechnology. After his retirement in 2001, he continued his visits to many countries and also served as co-editor of the "Biotechnology" theme for the UNESCOsponsored "Encyclopaedia for Life Support Systems". We thank Lucy Hoareau, Division of Basic and Engineering Sciences at UNESCO, for supplying this dedication.

Poverty is a severe problem in Africa, Asia, South America and even in pockets of the developed world. Addressing poverty alleviation via the expanded use of biological nitrogen fixation in agriculture was the theme of the 15th International Congress on Nitrogen Fixation. Because nitrogen-fixation research is multidisciplinary, exploiting its benefits for agriculture and environmental protection has continued to attract research by diverse groups of scientists, including chemists, biochemists, plant physiologists, evolutionary biologists, ecologists, agricultural scientists, extension agents, and inoculant producers.

The 15th International Congress on Nitrogen Fixation was held jointly with the 12th International Conference of the African Association for Biological Nitrogen Fixation. This joint Congress was hosted in South Africa at the Cape Town International Convention Centre, 21-26 January 2007, and was attended by about 200 registered participants from 41 countries world-wide. During the Congress, some 100 oral and approximately 80 poster papers were presented. The wide range of topics covered and the theme of the Congress justifies this book's title, Nitrogen Fixation: Applications to Poverty Alleviation.

Crop yields depend on many factors, but primarily on three major inputs; the capture of the Sun's light energy as chemical energy through photosynthesis, a source of water, and on the availability of a fixed-nitrogen (either mineral or organic) source. This Congress dealt with the last of these three major inputs. An enormous reservoir of nitrogen resides in the atmosphere as nitrogen (N 2 ) gas, however, this atmospheric nitrogen is not directly usable. It only becomes available to the biosphere through biological nitrogen fixation (BNF), a process that only the simplest microorganisms have developed. Through associations with these nitrogen-fixing microorganisms, plants can, in turn, derive a significant proportion of their fixed-nitrogen requirement for growth from BNF. The most agriculturally important associations are those of legume crops (for example, soybeans, peas, and feed legumes, like alfalfa and clover) with Rhizobium bacteria, where a tight symbiotic relationship occurs within a specially developed organ, the nodule, usually on the roots of the plants. An ecologically significant association involves Frankia microbes with trees and shrubs, which help reclaim devastated soils, and through inter-cropping can enhance the growth of valuable lumber-producing trees. Other associations include cyanobacteria with plants and trees as well as the more informal associative and endophytic associations of microorganisms with grasses, most particularly with sugarcane, where possibly all of its fixed-nitrogen requirement can be supplied by BNF. These examples clearly illustrate why BNF is a key metabolic process for food production and the maintenance of life on Earth.

Preface xxvii

The Congress theme, the application of BNF to sustainable agriculture, poverty alleviation, and environmental concerns, was well covered and included the introduction of nitrogen-fixing legumes into local small holdings, appropriate use of both soil and water, the use of indigenous soil microbes to provide N and P, and good agricultural practices generally. In addition, the basic sciences that underpin these more applied aspects were also well represented through presentations and progress reports, among others, on the fundamentals of nitrogen fixation (including a nitrogenase -the enzyme responsible for the chemical conversion of N 2 gas to ammonia -that can fix N 2 at 92 C!), plant breeding, plant and microbial molecular biology, legume-Rhizobium genetics, genomics, gene expression, evolution of symbioses, and nodulation physiology, stress responses, bioremediation, and forestry.

Sustainable agriculture not only depends on appropriate agricultural practices but, to maintain high yields, it requires the use of plant cultivars that respond to environmental constraints. In addition to classical plant-breeding technology, the modern-day engineering of high-performance crops and symbiotic associations can now access and use the incredible insight acquired through plant and bacterial genomics. Both topics were well represented in the Congress. Indeed, refined gene-sequence maps of the model legumes, Lotus japonicus and Medicago truncatula, have led to exciting genomic work in other legumes. On the microbial side, research on Sinorhizobium meliloti and Mesorhizobium loti as well as the broad host range Rhizobium NGR234 has reached the post-genomics era. The recent and rapid progress made in sequencing the genomes of Azotobacter vinelandii, Azospirillum brasilense, Herbaspirillum seropedicae, Azorhizobium caulinodans, Gluconactetobacter diazotrophicus and Frankia was also reported. Moreover, there were reports of photosynthetic bradyrhizobia that lack the nodAC genes, which are necessary for Nod-factor biosynthesis and, therefore, for initiation of symbiosis. This discovery opens new opportunities for research in the area of plantmicrobe signaling during the early stages of symbiotic establishment. New exciting data showed that members of the ß-proteobacteria (only recently recognized as microsymbionts), isolated from Mimosoideae can infect and fix N 2 in Papillionoideae. All this plus a cyanobacterium that anticipates sunrise each morning! Taken together, the excellent technical presentations and the lively discussions that ensued, both during and after the oral and poster sessions, are clear indicators of the success of the Congress. We hope that this volume will serve as a living reminder of those sweet moments in Cape Town. On a sad note, during the preparation of these Proceedings, we learned of the untimely death of Edgar DaSilva, who was an avid supporter of biological nitrogen-fixation research. We feel it only appropriate to dedicate these Proceedings to his memory.

Finally, we wish to thank all the individuals who helped to organize this Congress and all those who gave their support, including Ms. Helen Zille, the Mayor of Cape Town, Mr. Ben Durham, who represented the RSA Department of Science and °xxviii Preface Technology, Professor Wieland Gevers, the CEO of the Academy of Sciences of South Africa, and Dr. Ibrahima Ndoye of the AABNF. We also thank the sponsoring organizations, listed elsewhere, without whose financial support the Congress would not have been possible. We especially thank Elizabeth Danckwerts (and her Mum) for their commitment and tireless effort in organizing the Congress. We sincerely appreciate Vicki Newton for her hard work, dedication, and guidance towards getting these Proceedings published. Lastly, we thank Edwina Felix for her voluntary service to the Congress and all the postgraduate students who assisted during the Congress.

  in soybean A. Lopez, C. Plassard, P. Rodino and G. Viennois . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 P. W. Singleton and D. Borthakur . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 F. Rusinga, S. Israel and G. Tredoux . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 N. Ohtake and K. Sueyoshi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Rhizobium-legume symbioses xiii Integrating N 2 -fixing legumes, soils, and livelihoods in southern Africa: A consortium approach Distribution of promiscuous soyabean rhizobia in some Zimbabwean soils Ecophysiological studies of legumes in Botswana: Types of bacterial strains from root nodules of cowpea (Vigna unguiculata L. Walp.) and an assessment of the symbiotic status of grain legumes using 15 N natural abundance Symbiotic N nutrition and yield of cowpea genotypes under different plant densities and cropping systems in South Africa Rhizobial diversity associated with South African legumes Diversity and competitiveness of rhizobia of the legume tree Acacia nilotica in Senegal Effects of rock phosphate on indigenous rhizobia associated with Sesbania sesban O. Sacko, R. T. Samba, I. Yattara, N. Faye, F. do Rego, T. Diop, Effect of added fertilizers on N 2 fixation and plant performance of shrubby legumes Genetic diversity of Acacia seyal del. rhizobial populations indigenous to Senegalese soils in relation to salinity and pH of the sampling sites D. Diouf, R. Samba-Mbaye, D. Lesueur, A. Bâ, B. Dreyfus, Contents Potential effects of elevated UV-B radiation on N 2 -fixing legumes in agricultural systems The diversity of root nodule bacteria associated with Lebeckia species Edgar DaSilva (1941-2007) This volume is dedicated to the memory of Edgar DaSilva, former Director of the Division of Life Sciences at UNESCO, in recognition of his long-term interest in biological nitrogen fixation research. Edgar joined UNESCO in 1974 and was responsible for the life-sciences programs. His name is associated with the UNESCO Microbiological Resource Centers (MIRCEN) program, which was initiated in 1975 in partnership with the United Nations Environment Program (UNEP), and the United Nations Development Program (UNDP).

  All protocol observed!

	Preface	xxix
		Felix Dakora
		Samson Chimphango
		Alex Valentine
		Claudine Elmerich
		William E. Newton
		Cape Town
		December 31, 2007

801 002 scientific documents at your fingertips © Springer, Part of Springer Science+Business Media

was supported by Cape Peninsula University of Technology UNESCO CTA (Technical Centre for Agricultural and Rural Cooperation, operating within the Cotonou Agreement between the African, Caribbean and Pacific Group and the European Union) National Research Foundation, Pretoria (South Africa)


This study

• Authorities have limited information and limited budget • Objective : minimizing the number of agents who cheat • Mechanism with probabilistic audit • Conditionnal audit probability (conditionned on past observed behavior) Greenberg (1986) • In each period, each agent receives a random income y • Players report income z ≤ y • Net income -If not audited : y -T(z) (N.B. T(y) ≤ y) -If audited :

• Truthfull reporting : y -T(y) • Cheating : y -T(z) -P(y,z) with P(y,z) > T(y) -T(z)

• Audit probability : p > 0 • Audit is perfect Assumptions (2)

• Agents live an infinite number of periods • Agents are risk-neutral • Myopic behaviour • p i (y) is the smallest audit probability for which player i reports truthfully • Myopic players cheat for p < p i (y) whatever y

• (there exists > 0, such that for all y and all i p i (y) > )

Assumptions (3)

• r = audit probability determined by the tax authorithy's budget constraint (exogenous)

-If r = 1 all players report truthfully -If r < all players will cheat -If r < p i (y) max some players will cheat Experimental design (1)

• Income stream : each subject receives a randomly selected income between 100 and 1000 yens at each period • Infinite lifetime (cont. prob = 0.9) • Many lives : each subject experiences several lives. • Ending : end time announced at the beginning.

After end time, no new sequence could start. Running sequence were allowed to be continued during a maximum extra-time of 15mn. • Payment : One sequence randomly selected and paid out

Experimental design (2)

• Two-treatments :

-T1 = low audit probability : Group 1 : p 1 = 1/3 Group 2 : p 2 = 1/4 -T2 = high audit probability : Group 1 : p 1 = 1/2 Group 2 : p 2 = 1/3

Summary

• Mechanism to minimize fraud based on random auditing and segregation • Group 1 :subjects fraud less frequently than predicted, and fraud only a part of their income • Group 2 : subjects fraud too frequently • In both groups fraud is more frequent as income increases

Feasibility