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East China Normal University (2021)

Effects of Drought on Root Respiration and the Mechanisms

翟德苹

Titre : Effects of Drought on Root Respiration and the Mechanisms

Auteur : 翟德苹

Grade : Doctoral Dissertation 2021

Université : East China Normal University

Résumé partiel
In the context of global climate change,the frequency,intensity and duration of extreme drought events will significantly increase over time.Extreme drought and its consequent changes in soil moisture could strongly affect terrestrial carbon cycle,especially for belowground carbon processes.As the second-largest flux in terrestrial ecosystems,soil respiration consists of soil heterotrophic and autotrophic(root)respiration,which are both considerably influenced by soil water content.Previous studies on responses of soil carbon fluxes to drought mostly focused on soil respiration and heterotrophic respiration.It remains unknown how root respiration responds to drought and what mechanisms underpin the biological and abiotic regulations.In this study,we first explored potential mechanisms controlling responses of root respiration to drought in different ecosystems by analysing a global dataset of drought simulation experiments.Secondly,we monitored root respiration in a long-term rainfall exclusion experiment in a subtropical evergreen broad-leaved forest to investigate the roles of soil environment and key biological processes in response to extreme drought.By conducting a greenhouse drought experiment on four dominant tree species with different hydraulic characteristics in subtropical forests,we further revealed the differential regulatory mechanisms influencing responses of fine root respiration to drought among tree species.The main findings were as follows :(1)By analysing the global dataset of simulated drought experiments,we found that drought significantly inhibited root respiration and specific root respiration in natural ecosystems(e.g.,forests and grasslands).The total and specific root respirations decreased by 21% and 10%,respectively.With the increase of drought intensity and the decrease of soil water content,the extent to which root respiration was inhibited by drought increased gradually.Among the biotic factors,photosynthesis,fine root biomass and root/shoot ratio were important factors affecting the responses of root respiration to drought.Under drought,both root respiration and specific root respiration declined with the decreased photosynthesis.In addition,drought caused a reduction in fine root biomass and an increase in root/shoot ratio at a global scale,which both consequently led to decreased root respiration.These results suggest that plants may change carbon allocation strategy under drought(e.g.,allocating a larger portion of carbon to belowground than aboveground parts)to mitigate the adverse effects of drought on plant physiology

Mots clés : Root respiration ;Drought;Subtropical forest ;Fine root ;Root order ;Carbon allocation ;

Présentation (CNKI)

Page publiée le 18 février 2022