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Journal of Arid Land  2020, Vol. 12 Issue (2): 252-266    DOI: 10.1007/s40333-020-0064-z
Research article     
Effects of long-term warming on the aboveground biomass and species diversity in an alpine meadow on the Qinghai-Tibetan Plateau of China
WEN Jing, QIN Ruimin, ZHANG Shixiong, YANG Xiaoyan, XU Manhou*()
Taiyuan Normal University, Jinzhong 030619, China
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Abstract  

Ecosystems in high-altitude regions are more sensitive and respond more rapidly than other ecosystems to global climate warming. The Qinghai-Tibet Plateau (QTP) of China is an ecologically fragile zone that is sensitive to global climate warming. It is of great importance to study the changes in aboveground biomass and species diversity of alpine meadows on the QTP under predicted future climate warming. In this study, we selected an alpine meadow on the QTP as the study object and used infrared radiators as the warming device for a simulation experiment over eight years (2011-2018). We then analyzed the dynamic changes in aboveground biomass and species diversity of the alpine meadow at different time scales, including an early stage of warming (2011-2013) and a late stage of warming (2016-2018), in order to explore the response of alpine meadows to short-term (three years) and long-term warming (eight years). The results showed that the short-term warming increased air temperature by 0.31°C and decreased relative humidity by 2.54%, resulting in the air being warmer and drier. The long-term warming increased air temperature and relative humidity by 0.19°C and 1.47%, respectively, and the air tended to be warmer and wetter. The short-term warming increased soil temperature by 2.44°C and decreased soil moisture by 12.47%, whereas the long-term warming increased soil temperature by 1.76°C and decreased soil moisture by 9.90%. This caused the shallow soil layer to become warmer and drier under both short-term and long-term warming. Furthermore, the degree of soil drought was alleviated with increased warming duration. Under the long-term warming, the importance value and aboveground biomass of plants in different families changed. The importance values of grasses and sedges decreased by 47.56% and 3.67%, respectively, while the importance value of weeds increased by 1.37%. Aboveground biomass of grasses decreased by 36.55%, while those of sedges and weeds increased by 8.09% and 15.24%, respectively. The increase in temperature had a non-significant effect on species diversity. The species diversity indices increased at the early stage of warming and decreased at the late stage of warming, but none of them reached significant levels (P>0.05). Species diversity had no significant correlation with soil temperature and soil moisture under both short-term and long-term warming. Soil temperature and aboveground biomass were positively correlated in the control plots (P=0.014), but negatively correlated under the long-term warming (P=0.013). Therefore, eight years of warming aggravated drought in the shallow soil layer, which is beneficial for the growth of weeds but not for the growth of grasses. Warming changed the structure of alpine meadow communities and had a certain impact on the community species diversity. Our studies have great significance for the protection and effective utilization of alpine vegetation, as well as for the prevention of grassland degradation or desertification in high-altitude regions.



Key wordsclimate warming      long-term warming      species diversity indices      aboveground biomass      soil microclimate      correlation analysis      alpine meadows     
Received: 13 May 2019      Published: 10 March 2020
Corresponding Authors: Manhou XU     E-mail: xumanhou@163.com
About author: *Corresponding author: XU Manhou (E-mail: xumanhou@163.com)
Cite this article:

WEN Jing, QIN Ruimin, ZHANG Shixiong, YANG Xiaoyan, XU Manhou. Effects of long-term warming on the aboveground biomass and species diversity in an alpine meadow on the Qinghai-Tibetan Plateau of China. Journal of Arid Land, 2020, 12(2): 252-266.

URL:

http://jal.xjegi.com/10.1007/s40333-020-0064-z     OR     http://jal.xjegi.com/Y2020/V12/I2/252

Fig. 1 Location of the study area on the Qinghai-Tibetan Plateau, China (a), a photograph of the warming plot (b) and the design of experimental plots (c)
Item T Y M T×Y T×M Y×M T×Y×M
Air temperature 0.054 0.000 0.000 0.038 0.294 0.000 0.560
Relative humidity 0.037 0.016 0.000 0.037 0.795 0.143 0.998
Table 1 Multi-way ANOVA of air temperature and relative humidity in different treatments, years and months
Fig. 2 Variations in air temperature (a) and relative humidity (b) in the growing season (from May to September) in different years and under different treatments. The shaded areas indicate standard errors (n=5).
Item T Y M T×Y T×M Y×M T×Y×M
Soil temperature 0.002 0.119 0.000 0.280 0.955 0.615 0.994
Soil moisture 0.277 0.223 0.015 0.977 0.995 0.933 1.000
Table 2 Multi-way ANOVA of soil temperature and soil moisture in different treatments, years and months
Fig. 3 Variations in soil temperature (a) and soil moisture (b) in the growing season (from May to September) in different years and under different treatments. The shaded areas indicate standard errors (n=5).
Item T Y F T×Y T×F Y×F T×Y×F
Importance value 0.098 0.000 0.000 0.793 0.604 0.019 0.892
Simpson index 0.774 0.000 0.236
Shannon-Weiner index 0.511 0.000 0.566
Margalef index 0.763 0.000 0.996
Pielou index 0.885 0.177 0.307
Aboveground biomass 0.826 0.164 0.000 0.570 0.332 0.315 0.962
Table 3 Multi-way ANOVA of vegetation importance value, species diversity indices and aboveground biomass in different treatments, years and families
Fig. 4 Variations in importance values of grasses (a), sedges (b) and weeds (c) in different years and under different treatments. The error bars indicate standard errors (n=3). It should be noted that grasses were not appeared under the warming treatment in 2011.
Fig. 5 Variations in species diversity indices in different years and under different treatments. (a), Simpson index; (b), Shannon-Weiner index; (c), Pielou index; (d), Margalef index. The error bars indicate standard errors (n=3).
Fig. 6 Variations in aboveground biomass of grasses (a), sedges (b) and weeds (c) and the total aboveground biomass (d) in different years and under different treatments. The error bars indicate standard errors (n=3). It should be noted that grasses did not appear in the warming plots in 2011.
Warming time scale Item Soil temperature Soil moisture
Control Warming Control Warming
Short-term warming
(three years)
Simpson index 0.246 0.143 -0.301 -0.223
Shannon-Weiner index 0.244 0.212 -0.282 -0.287
Margalef index 0.245 0.287 -0.251 -0.376
Pielou index 0.123 -0.127 -0.138 -0.084
Aboveground biomass 0.660* -0.287 -0.359 0.406
Long-term warming
(eight years)
Simpson index 0.298 0.144 -0.355 -0.304
Shannon-Weiner index 0.385* 0.159 -0.417* -0.326
Margalef index 0.418* 0.195 -0.414* -0.315
Pielou index 0.030 0.020 -0.074 -0.217
Aboveground biomass 0.296 -0.464* -0.028 0.178
Table 4 Correlation analysis of soil microclimate factors (soil temperature and soil moisture) with species diversity indices (Simpson index, Shannon-Weiner index, Margalef index and Pielou index) and aboveground biomass at different warming time scales and under different treatments
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