青藏高原纳木错高寒草甸生态系统碳交换对多梯度增水的响应

doi:10.17521/cjpe.2015.0395

摘要/Abstract

摘要：

高寒草甸是青藏高原的主要草地类型, 对青藏高原生态系统碳收支具有重要的调节作用。目前, 有关高寒草甸生态系统碳交换对气候变化的响应所知甚少, 尤其是降水变化会如何影响高寒草甸碳交换过程的相关研究非常匮乏。该文作者于2013和2014年的生长季(5-9月)在青藏高原纳木错地区高寒草甸进行多梯度人工增水实验, 设置对照和5个水分添加梯度, 分别增加0%、20%、40%、60%、80%和100%的降水, 以研究高寒草甸生态系统在不同降水量条件下的碳交换变化。增水处理后, 各处理梯度之间的土壤温度没有显著差异, 而土壤含水量在不同增水处理后出现显著变化, 相对于对照, 增水幅度越大, 对应的土壤含水量越高。综合2013和2014年的观测结果, 高寒草甸生态系统整体表现为碳吸收, 在20%增水处理中, 净生态系统碳交换(NEE)达到最大值, 随着模拟的降水梯度进一步增加, NEE逐渐下降; 增水处理对生态系统呼吸(ER)无显著影响; 总生态系统生产力(GEP)的变化趋势与NEE一致, 即随着增水梯度增大, GEP先增加, 并在增水20%处理达到最大值, 随后GEP开始降低。研究表明, 在高寒草甸生态系统, 水分是影响GEP和NEE的重要因素, 对ER影响较弱; 未来适度的增水(20%-40%)能促进高寒草甸生态系统对碳的吸收。

关键词: 碳交换, 增水, 高寒草甸, 青藏高原

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.

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

耿晓东, 旭日, 刘永稳. 青藏高原纳木错高寒草甸生态系统碳交换对多梯度增水的响应. 植物生态学报, 2018, 42(3): 397-405. DOI: 10.17521/cjpe.2015.0395

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. Chinese Journal of Plant Ecology, 2018, 42(3): 397-405. DOI: 10.17521/cjpe.2015.0395

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2015.0395

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

图/表 5

图1 增水样地设计分布与增水装置现场。0%-100%表示降水增加的百分比。

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

图2 2013年和2014年高寒草甸生长季不同增水处理地下5 cm处土壤体积含水量(A, B)以及降水量(C, D)的动态变化。0%-100%分别表示不同增水处理。

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.

图3 2013年和2014年生长季不同增水处理地下5 cm处土壤体积含水量(A, B)和土壤温度(C, D) (平均值±标准误差)。相同的字母代表增水处理之间最小显著差异(LSD)法多重比较结果差异不显著(p > 0.05), 不同字母表示处理间差异显著(p < 0.05), 其中2014年增水60%处理的温度值缺失。

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.

图4 2014年净生态系统碳交换(NEE, ▼) (对照处理)、降水(柱状图)和温度(线图)的季节变化, NEE值采用每日多次测定平均值; 温度为地下5 cm温度。

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.

图5 2013-2014年生长季不同增水处理下的净生态系统碳交换(NEE) (A, B)、生态系统呼吸(ER) (C, D)以及总生态系统生产力(GEP) (E, F), (平均值±标准误差)。相同的字母代表不同处理之间最小显著差异(LSD)法多重比较结果差异不显著(p > 0.05), 不同字母表示处理间差异显著(p < 0.05)。

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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