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East China Normal University (2020)

Responses of Tree Non-structural Carbohydrates to Drought and the Regulation Mechanisms

张佩佩;

Titre : Responses of Tree Non-structural Carbohydrates to Drought and the Regulation Mechanisms

Auteur : 张佩佩;

Grade : Doctoral Dissertation 2020

Université : East China Normal University

Résumé
Non-structural carbohydrates(NSCs)are important buffering substances for plants to tackle climate changes and play a crucial role in maintaining tree survivals under environmental stress.With globally increased intensity and frequency of extreme drought events,a better understanding of NSC responses to drought and the underlying mechanisms is greatly essential for accurately predicting global vegetation dynamics and ecosystem carbon cycling under future climate change.In ecosystems,many factors(e.g.,tree species,drought intensity and duration)affect NSC responses to drought.Among them,differences in water use and carbon storage capacity at different tree developmental stages may have great impacts on NSC dynamics in response to drought.However,little is known about whether and how such differences in tree developmental stages(e.g.,mature trees and saplings/seedlings)affect NSC responses to drought,and our knowledge on the key factors in influencing tree NSC responses and the underlying mechanisms remains elusive.In this study,we collected NSC data under drought and performed a meta-analysis to explore the general patterns of tree NSC response to drought and examine the effects of the key factors,especially tree developmental stages.Furthermore,we conducted a large-scale field throughfall exclusion experiment to compare the differences in NSC response to drought between mature trees and understory seedlings growing in the same ecosystem.To clearly reveal the function of NSC in tree resistance and resilience to drought,we conducted a drought-rewatering gradient potted experiment on two species to detect tree NSC responses during persistent drought and recovery and explore the carbon-water coupling relationships.The main results are as follows :(1)Using a meta-analysis on tree NSC under drought from 32 studies on mature trees and 94 studies on seedlings at a global scale,we analyzed the response magnitudes of tree NSC to drought and investigated the key factors influencing the response magnitudes.The results showed that,drought significantly increased soluble sugar concentrations by 7.3% and decreased starch concentrations by 18.96%,although it had no significant effects on the total NSC concentrations.Under drought conditions,both the increase of soluble sugars and the decrease of starch in seedlings were larger than those in mature trees.

Mots clés : Non-structural carbohydrates; Tree carbon balance; drought; Subtropical evergreen broadleaf forest; Tree mortality; Developmental stages; Resistance; Resilience;

Présentation (CNKI)

Page publiée le 15 juin 2021