Effect of seasonal timing of drought on carbon exchange in the alpine meadow ecosystem of the Qinghai-Tibetan Plateau

doi:10.11686/cyxb2020276

Abstract

Abstract:

Extreme drought events can significantly change soil hydrothermal conditions and plant community characteristics， and then affect the ecosystem carbon exchange. In this study， we used rain shelters to artificially produce early season growing drough （ED， greening up stage， May-June） and middle growing season drought （MD， rapid growing stage， July-August）， to study the responses of plant community responses and ecosystem carbon exchange. It was found that vegetation height， cover and aboveground biomass were significantly lower in ED than in control （P<0.05） during the middle of the growing season. ED and MD depressed the total ecosystem productivity （GEP） and ecosystem respiration （ER） significantly （P<0.05） in the middle of the growing season. Moreover， net ecosystem carbon exchange significantly decreased （P<0.05） under the MD treatment. Regression analysis showed that there was a significant positive correlation between the soil moisture and ER （P<0.05） under ED in the middle of growing season. Also， ER was significantly positively correlated with soil moisture and community biomass （P<0.05） in the MD treatment during the early growing season. The mechanisms of drought impact differed with different seasonal timing of imposed drought. The ED mainly affected carbon exchange by inhibiting plant growth processes， while the MD primarily affected carbon exchange by inhibiting plant physiological activity. This study expands knowledge of how this alpine meadow ecosystem responds to drought at different times within the growing season， and provides data supporting climate change projection research.

Key words: growing season, drought events, carbon exchange, soil volume water content, biomass

Zi-xin WANG, Guo-zheng HU, Hong-wei SHUI, Yi-qing GE, Ling HAN, Qing-zhu GAO, Ganjurjav HASBAGAN, Luo-bu DANJIU. Effect of seasonal timing of drought on carbon exchange in the alpine meadow ecosystem of the Qinghai-Tibetan Plateau[J]. Acta Prataculturae Sinica, 2021, 30(4): 24-33.

Figures/Tables 5

Fig.1 Effects of precipitation and drought on soil volume water content at different times

Fig.2 Effects of drought in different growth period on plant community height, cover age and above-ground biomass

Fig.3 Effects of drought in different growth period on gross ecosystem productivity （GEP）, ecosystem respiration （ER） and ecosystem net carbon cycle （NEE）

Fig.4 Correlation analysis of soil volume water content and gross ecosystem productivity (GEP), ecosystem respiration (ER), net ecosystem carbon exchange (NEE)

Fig.5 Correlation analysis of above-ground biomass and gross ecosystem productivity (GEP), ecosystem respiration (ER), net ecosystem carbon exchange (NEE)

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