Responses of ecosystem carbon exchange to multi-level water addition in an alpine meadow in Namtso of Qinghai-Xizang Plateau, China

doi:10.17521/cjpe.2015.0395

Abstract

Abstract:

Aims Alpine meadow is widely distributed in the Qinghai-Xizang Plateau, playing an important role in regulating the regional carbon budget. Over the Qinghai-Xizang Plateau, precipitation generally shows an increasing trend during past the several decades, and is projected to increase during the 21st century. Alpine meadow is very susceptible to such climate change, but it remains unclear how its ecosystem carbon exchange responses to precipitation change. In this study, we aim to clarify the effects of altered precipitation on ecosystem carbon exchange in the alpine meadow by conducting a manipulative field experiment.

Methods We conducted a precipitation manipulation experiment at an alpine meadow site in the Namtso area of central Qinghai-Xizang Plateau during 2013 to 2014. A total of six treatments were established, with levels of water addition set for 0%, 20%, 40%, 60%, 80% and 100%, respectively, of equivalent increases in precipitation. We investigated the effects of water addition on gross ecosystem production (GEP), ecosystem respiration (ER), net ecosystem carbon exchange (NEE), and environmental conditions during the growing season.

Important findings The increasing water addition substantially increased soil moisture, but had no significant effect on soil temperature. Both GEP and NEE significantly increased with water addition equivalent to 20% of increases in precipitation, but were suppressed with further increases in the level of water addition. No significant difference was detected in ER across the water addition treatments. Our study suggests that: 1) The change in soil moisture significantly affected NEE and GEP but had a weak effect on ER in the alpine meadow; 2) CO₂ sequestration in the alpine meadow could be stimulated by moderate increases (e.g. 20%-40%) in precipitation.

http://jtp.cnki.net/bilingual/detail/html/ZWSB201803014

Key words: carbon exchange, water addition, alpine meadow, Qinghai-Xizang Plateau

GENG Xiao-Dong, Xu Ri, LIU Yong-Wen. Responses of ecosystem carbon exchange to multi-level water addition in an alpine meadow in Namtso of Qinghai-Xizang Plateau, China[J]. Chin J Plant Ecol, 2018, 42(3): 397-405.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2015.0395

https://www.plant-ecology.com/EN/Y2018/V42/I3/397

Figures/Tables 5

Fig. 1 Layout of water addition treatments and of the field experimental site. Values 0%-100% represent the percentage of increases in precipitation.

Fig. 2 Seasonal variations in soil volumetric water content (SVWC) at 5 cm depth under different water addition treatments (A, B) and precipitation for alpine meadow (C, D) in 2013 and 2014. Values 0%-100% represent different levels of water addition treatments.

Fig. 3 Soil volumetric water content (SVWC) (A, B) and temperature (C, D) at 5 cm depth under different water addition treatments in the growing seasons of 2013 and 2014 (mean ± SE). Same letters indicate a non-significant difference (p > 0.05) according to the least significant difference (LSD) test, and different letters indicate significant differences (p < 0.05) among treatments. Temperature data were not available for the water addition treatment of 60% in 2014.

Fig. 4 Seasonal dynamics of net ecosystem carbon exchange (NEE, ▼) (control), precipitation (column) and temperature (line) in 2014. The NEE value is the mean of multiple investigations in a day, and the temperature refers to the soil temperature at 5 cm depth.

Fig. 5 Net ecosystem carbon exchange (NEE) (A, B), ecosystem respiration (ER) (C, D) and gross ecosystem production (GEP) (E, F) under different water addition treatments in the growing seasons of 2013 and 2014 (mean ± SE). Same letters indicate a non-significant difference (p > 0.05) according to the least significant difference (LSD) test, and different letters indicate significant differences (p < 0.05) among treatments.

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