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Lanzhou University (2020)

Research of Carbon-water Coupling Mechanisms of Typical Vegetation in An Arid Oasis Ecosystem


Titre : Research of Carbon-water Coupling Mechanisms of Typical Vegetation in An Arid Oasis Ecosystem

Auteur : 韩拓;

Grade : Doctoral Dissertation 2020

Université : Lanzhou University

Résumé partiel
Oasis plays a very important role in regulating regional climate and feeding population in the arid area of northwest China,although it covers less than 5% of the total area.Water resource is the most valuable natural resource in oasis ecosystem,which has a significant impact on restricting vegetation survival and evolution.A better understanding of the carbon-water coupling mechanism of diverse vegetation which grow in environment with limited water can not only be helpful for guiding local scientific planting and irrigating,but also be of great significance in predicting the feedback mechanism of vegetation-atmosphere in the context of climate change.However,the mechanisms on the coupled relationships between photosynthesis and transpiration at leaf scale have not been reported in detail,especially in arid oases.Thus,we conducted a series of field experiments in Nanhu Oasis,supported by Dunhuang Eco-hydrological Observation Station.Meanwhile,some laboratory tests and related models were also performed in this study.Firstly,we revealed photosynthetic characteristics and photosynthetic capacity of 36 species which belonging to 6 plant functional types(PFTs),respectively ;then,explored the behavior of photosynthesis-transpiration coupling and its influence factors ;meanwhile,revealed the impact of stomatal control on carbon-water coupling behavior ;finally,compared the water use efficiency(WUE)among species.The main conclusions are as follows :(1)Characteristics of diurnal courses and seasonal variation of the net photosynthesis rates(An)among species were basically identical,while the carbon fixation capacity(Anmax):the diurnal courses were similar to parabolic curves,with single-peak or double-peak ;affected by both environmental factors and physiological conditions,An showed obvious seasonal variation which firstly increased and then decreased from May to October,and reached the maximum value in August ;C4vegetation had the strongest carbon fixation capacity,Anmax can reach up to 38.77 mol m-2 s-1,while ENF had the lowest carbon fixation capacity,only about 6.39 mol m-2 s-1.(2)Sensitivity analysis effectively identified key parameters among all photosynthetic parameters.Based on the result of sensitivity analysis,we created the hierarchical Bayesian structure which had the ability to estimate parameters across diverse species at different levels(i.e.,plant,species,and PFTs level)simultaneously

Mots clés : Arid oasis; Photosynthesis; Stomatal conductance; Carbon-water coupling; Water use efficiency;

Présentation (CNKI)

Page publiée le 5 juin 2021