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Lanzhou University (2021)

Drought Decreases Optimum Population Density in Dryland Wheat:Modeling and Mechanisms

朱赛勇

Titre : Drought Decreases Optimum Population Density in Dryland Wheat:Modeling and Mechanisms

Auteur : 朱赛勇

Grade : Doctoral Dissertation 2021

Université : Lanzhou University

Résumé partiel
Rational planting density was crucial in agricultural production,which enabled sufficient and efficient use of space,solar energy,water and soil nutrients,and produced considerable economic yield.Estimating optimum population density in rain-fed regions relied mostly on descriptive models,which was only suitable for some special climates.However,erratic climate changes,especially the irregular precipitations and drought stress,occurred repeatedly in rain-fed regions.As one of the most important environmental stresses,drought impaired wheat plant growth,reduced population yield and lowered optimum population density.Available models for estimating optimum population density were empirical and did not provide biological or ecological significance for explaining the variations of optimum population density in response to soil water availability.In the present study,model based on the law of constant final yield and the scaling relationship of biomass allocation was built as to discover the mechanisms underlying optimum population density dynamics in response to soil water availability.Pot culture and field experiments were carried out to verify the reliability of the deduced model.In order to investigate the relationship between allometry of biomass allocation and optimum population density,dynamics of biomass accumulation and allocation during wheat plant growth under drought and crowding situations was analyzed in pot culture experiment.Furthermore,different wheat cultivars were selected to verify the above trends in a broader scope.1.The deductions of optimum population density model for dryland wheatThe yield formation of wheat was largely decided by two factors,which were biomass accumulation and biomass allocation.Two classical ecological theories,incluing the law of constant final yield and the metabolic theory of ecology,were used to build the model.1)Based on basic ecological theories,the deduced model was characterized by asymptotic biomass increasing and allometry of biomass allocation.Optimum population density was decided by two parameters,which was k(the density producing half of maximum biomass)andα(the scaling exponent between grain mass and body size).The model assumed that the optimum population density was the trade-off outcome between resources acquisition(vegetative allocation)and reproduction(reproductive allocation)

Mots clés : Optimum population density ;Drought stress ;Reproductive allocation ;Allometry growth ;The law of constant final yield ;

Présentation (CNKI)

Page publiée le 18 février 2022