Effects of grazing and simulated warming on plant community structure and productivity of alpine grassland in Northern Xizang, China

doi:10.17521/cjpe.2018.0288

Abstract

Abstract:

Aims Climate change and grazing activities have important effects on species diversity and productivity of grassland ecosystems. The aim of this study is to reveal the differences in responses of species diversity and productivity to warming, grazing and their interactions in an alpine meadow ecosystem. Methods Warming experiment was established in 2011. In 2016, the grazing experiment and the combination of warming and grazing experiment were added. A two-year continuous field experiment was conducted (from 2016 to 2017) and plant community structure, community composition, productivity and species diversity were monitored. Twelve sites were sampled, and were divided into four treatments: control, warming, grazing and the combination of warming and grazing. All sampled species were classified into three functional groups: sedges, grasses and forbs. The species diversity and productivity were sampled in three different treatments. Important findings Results showed that warming and grazing had significant interaction on vegetation height and net primary productivity in alpine grassland. Under grazing treatment, warming had no significant effect on plant height, while warming significantly increased plant height without grazing. Under grazing treatment, the warming effect on net primary productivity significantly differed between 2016 and 2017. In 2016, warming had no significant effect on net primary productivity, while in 2017, warming significantly decreased net primary productivity. Warming and grazing had no significant interaction on species richness, coverage, species important value and species diversity in the alpine meadow. Under the treatments of warming and grazing, the total vegetation coverage decreased, and the proportion of forbs significantly increased. However, no significant effect of warming or grazing was found on species diversity. This study showed that warming and grazing significantly changed the community structure of alpine grassland. Therefore, with the projected climate change in the future, the intensification of grazing activities may lead to the decrease of alpine meadow productivity.

http://jtp.cnki.net/bilingual/detail/html/ZWSB201910002

Key words: warming, grazing, the combination of warming and grazing, species diversity, net primary productivity

WU Hong-Bao, GAO Qing-Zhu, Ganjurjav Hasbagan, LI Yu, YAN Yu-Long, HU Guo-Zheng, WANG Xue-Xia, YAN Jun, HE Shi-Cheng. Effects of grazing and simulated warming on plant community structure and productivity of alpine grassland in Northern Xizang, China[J]. Chin J Plant Ecol, 2019, 43(10): 853-862.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2018.0288

https://www.plant-ecology.com/EN/Y2019/V43/I10/853

Figures/Tables 10

Fig. 1 Mean diurnal air temperature and precipitation in the experiment site of alpine grassland in Northern Xizang (from 2016 to 2017).

Fig. 2 The diagram of the warming equipment used here— open top chamber.

Fig. 3 Mean air temperature, temperature and moisture of the soil (from April to August in 2016 and 2017) in control (CK), warming (W), grazing (G) and warming + grazing (WG) plots.

Table 1 Results (p value) of the three way ANOVA of year, warming, grazing and their interaction effects on height, coverage, species important value, net primary productivity and species diversity index of alpine grassland in Northern Xizang

因子 Factor	高度 Height			盖度 Coverage	物种重要值 Species important value			净初级生产力 Net primary productivity	物种多样性指数 Species diversity index
因子 Factor	莎草类 Sedges	禾草类 Grasses	杂类草 Forbs	盖度 Coverage	莎草类 Sedges	禾草类 Grasses	杂类草 Forbs	净初级生产力 Net primary productivity	Species richness index	Shannon- Weiner index	Pielou index
Y	0.061	0.032	0.480	0.481	0.052	0.412	0.446	0.074	0.209	0.907	0.078
W	<0.001	<0.001	0.001	<0.001	0.055	0.773	0.174	0.618	1.000	0.543	0.331
G	<0.001	<0.001	<0.001	0.004	0.008	0.445	0.003	0.503	0.396	0.872	0.236
Y × W	0.065	0.055	0.396	0.444	0.716	0.191	0.199	0.158	0.668	0.523	0.511
Y × G	0.380	0.283	0.143	0.092	0.482	0.177	0.290	0.122	0.001	0.019	0.470
W × G	0.003	0.001	0.001	0.376	0.882	0.103	0.066	0.048	1.000	0.617	0.347
Y × W × G	0.903	0.103	0.587	0.926	0.169	0.201	0.708	0.145	0.209	0.332	0.904

Fig. 4 Mean vegetation height (mean ± SE) in the control (CK), warming (W), grazing (G) and warming + grazing (WG) plots of alpine meadow in Northern Xizang. Different lowercase letters indicate significant differences in height in group plant (p < 0.05).

Table 2 Species composition and their important values of alpine grassland communities under treatments of control, warming, grazing and the combination of warming and grazing in Northern Xizang in 2017

植物类群 Plant group	物种 Species	CK	W	G	WG
莎草类 Sedges	高山嵩草 Kobresia pygmaea	0.420	0.354	0.475	0.448
	青藏薹草 Carex moorcroftii	0.109	0.118	-	-
	矮生嵩草 Kobresia humilis	0.028	-	-	-
禾草类 Grasses	紫花针茅 Stipa purpurea	-	-	0.113	0.179
禾草类 Grasses	草地早熟禾 Poa pratensis	0.197	0.238	-	-
杂类草 Forbs	垫状点地梅 Androsace tapete	0.003	0.002	-	-
	星状雪兔子 Saussurea stella	-	-	0.064	0.033
	矮火绒草 Leontopodium nanum	-	-	0.040	-
	蓝花棘豆 Oxytropis caerulea	0.032	0.041	0.058	-
	藏豆 Stracheya tibetica	-	0.019	-	0.064
	蒲公英 Taraxacum mongolicum	-	-	0.014	0.025
	肉果草 Lancea tibetica	0.052	0.034	-	0.007
	短穗兔耳草 Lagotis brachystachya	0.008	0.030	0.034	0.024
	二裂委陵菜 Potentilla bifurca	0.043	0.069	0.068	0.071
	钉柱委陵菜 Potentilla saundersiana	0.047	0.061	0.073	0.075
	多裂委陵菜 Potentilla multifida	0.047	0.034	0.061	0.074
	山莓草 Sibbaldia procumbens	0.014	-	-	-

Fig. 5 Mean species important values in control (CK), warming (W), grazing (G) and warming + grazing (WG) plots of alpine grassland in Northern Xizang.

Fig. 6 Mean vegetation coverage and net primary production (mean + SE) in control (CK), warming (W), grazing (G) and warming + grazing (WG) plots of alpine grassland in Northern Xizang. Different lowercase letters indicate significant differences in coverage and net primary production in different treatments (p < 0.05).

Fig. 7 Mean species diversity (mean + SE) in control (CK), warming (W), grazing (G) and warming + grazing (WG) plots of alpine grassland in Northern Xizang. Different lowercase letters indicate significant differences in species diversity in different treatments (p < 0.05)

Fig. 8 Community structure, species diversity and productivity (mean + SE) in warming (W), grazing (G) and warming + grazing (WG) plots of alpine grassland in Northern Xizang. Different lowercase letters indicate differences in treatment effect (p < 0.05); **, indicate differences between treatment effect and zero (p < 0.01).

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