1、Vegetation structure and productivity : The result of a game?,Niels Anten Plant Ecology & Biodiversity Utrecht University,Important challenge in plant ecology: Developing a theoretical framework to scale from:,Performance of the individual plant,Structure, productivity & species composition of veget
2、ation stand,Why is this scaling important?,Any mutation at the level of molecular level. Local fitness consequences population (vegetation stand) All of what we eat is (indirectly) the result of whole-stand productivity More than 50% of global CO2 uptake (120 Gt/yr) is taken up by terrestrial vegeta
3、tion,Why is scaling important? Climate influences plants and plants influence climate,Global temperature increase,Measuring leaf area photosynthesis of every leaf and then adding up,Need for simplicity,Future impact of vegetation change in a large area: We can not measure everything,Optimization,Con
4、ditions: limiting Factor (X),But what do plants optimize?,Three sections to this talkSimple optimization: Are vegetation stands optimal to maximize whole-stand productivity? Competitive optimization: Are vegetation stands the result of a game leading to a tragedy? Game theory and clonal plants: a sp
5、ecial case? Practical applications of game theory for crop science and climate change research,Part 1. Simple optimization: The case of optimal LAIs & and applications to global change research,Photosynthesis provides substrates for growth and reproduction,Focus on optimal nitrogen use by plants,Pho
6、tosynthesis and nitrogen are strongly positively correlated,Optimal leaf area production,An increase in LAI,Increased LAI assuming fixed total N: More light capture but also more selfshading A reduction in mean leaf N content (Narea = Canopy N /LAI) lower photosynthesis per unit leaf area,N content
7、of every equals minimum Photosynthesis = 0,LAI = 0 Photosynthesis = 0,Optimal LAI,Optimal LAI for maximum whole-stand photosynthesis exists: Above optimal LAI increased light capture no longer compensates for reduced photosynthetic capacity of leaves,Anten et al. 1995b Phys Plant,FACE experiment whe
8、re rice was grown at elevated CO2 (570 ppm) under otherwise natural conditions,Case study: Model for optimal LAI to predict effects of elevated CO2 on LAI at two nitrogen availabilities high (HN) and low N (LN),Anten et al. (2004) New Phyt,Differences between stands of different species or growing u
9、nder different conditions are well predictedMeasured LAI are always greater than optimal values,Anten et al. (1998) Plant Ecol Anten & Hirose (2001) Oecologia,optimal = actual line,r2 = 0.71,regression,Simple optimisation (Maximisation of performance at the stand level),Vegetations are summations of
10、 close to identical individualsoptimal characteristics of individuals reflected at the population-level,Part 2 Competitive optimization: Is the structure of vegetation stands the result of a game?,Sensitivity analysis for Xanthium canadense stands : Is its LAI optimal and can it be invaded?,Homogeno
11、us monostands ideal for studying competitive interactions,Stand level photosynthesis,Individual plants can increase their photosynthesis by increasing their leaf area even if the LAI of the stand is greater than optimal,Anten & Hirose 2001 Oecologia,Competitive instead of simple optimization: Evolut
12、ionarily stable strategies,The model for ES-LAI can be a good predictor of real LAIs,Anten (2002) J Theor Biol Anten et al. (2004) New Phyt,Evolutionary game theory a suitable theoretical framework for scaling from leaf to plant community?,Other traits subject to a tragedy of the commons,Plant heigh
13、t (Givnish 1982 Am Nat) Root growth (Gersani et al. 2001 J Ecol) Leaf turn over (Boonman, Anten, Pons et al 2006 Am Nat) Flowering time (Pronk, Anten, Werger 2007 Ecol Compl) Leaf angle (Hikosaka 1999 Ecoscience) Defence?,The root game,When plants share soil with neighbors: they overinvest in roots
14、to steal nutrients away from their neighborsThis goes at the expense of seed productionNote 20-30% difference in seed production,Gersani et al. (2001) J Ecol,The senescence game,N,N,Wild type surrounded by other genotypes with slower or no senesence?,We need an alternative plant that is the same in
15、all respects except those things predicted by the model,WT SAG,PSAG12-IPT (SAG) tobacco has delayed leaf senescence,WT monoculture,SAG monoculture,WT/SAG mixture,Characterizing responses of SAG and WT to stand density and modeling consequences for daily carbon gain,WT monostand,SAG monostand,leaf se
16、nescence,top canopy,bottom canopy,Boonman, Anten, Pons (2006) American Naturalist,Observed responses at the leaf level,Wild type has a lower fitness in a mono-stand than SAG but higher fitness they compete,Shade induced senescence: Plants drop their leaves sooner when growing in a canopy They use th
17、e N available to produce more leaf area not leaves with a higher N content This gives them higher fitness only when competing with genotypes that do otherwise,Anten & Geerlings (in prep),Part 3 Games with clonal plants: self/non-self interaction,In clonal plants genetically shoots can be neighbors,T
18、ragedy of the commons depends self/non-self interaction,Niinemets and Anten (2009),Aster lanceolata Guerilla,Solidago canadense Phallanx,Leaf production,Leaf death,Aster (guerilla),Solidago (guerilla),Schmid ,Tragedy of the commons,Simple optimization,Current Research: How about other species and ot
19、her traits?,Anten 2010 Oecologia,Part 4 Applications of evolutionary game theory,Two percent annual increase in yields needed to keep up with rising food demand!,Food supply,Are crops maximizing production per unit area?,Crops and game theory: current research,How large is yield reduction under fiel
20、d conditions? Genotypic variation: Do all crops and cultivars exhibit this tragedy of the commons? Physiological mechanisms: How are these tragedies regulated?,Climate-vegetation models,Vegetation strongly affects climate-Lowering CO2 -Evapotranspiration increasing local precipitation- Lower albedo,
21、 higher land temperature more convective moisture transport.,Vegetation climate-feedback Tipping points,Are deserts self-sustained?,9000 bp,5000 bp,present,Desertification of the Sahara,irradiance,temperature,rainfall,Vegetation cover,Was this a vegetation-climate feedback ? Can such feedbacks occur
22、 today?,36,Climate-vegetation models,Purely emperical models: too many data that can not be obtained (especially for the future or distant past) Simple optimisation: Inaccurate Evolutionary game theory? Maybe!,Concluding remarks,Optimal plant communities are not evolutionarily and can be invaded by
23、a cheater overinvesting in resource harvesting Real vegetation stands are not maximally productive. Competitive optimisation provides a theoretical framework to scale from leaf to canopy. We are beginning to understand species diversity through multiplayer games There are ample applications in crop science and climate change research,How good are big leaf models and can they be adjusted?,Coefficient for N distribution (Kn) about 0.4 x coefficient light (Kl),Mean error can be reduced from 8 to 2%,Anten 1997; Niinemets & Anten 2008,
