Effects of yak and Tibetan sheep grazing on plant and microbial carbon and nitrogen pools in alpine grassland

doi:10.17521/cjpe.2025.0006

Abstract

Abstract:

Aims Alpine grasslands, a critical component of global ecosystems, are highly sensitive to climate change and human activities. The carbon and nitrogen pools of plants and soil microbes constitute essential parts of the carbon and nitrogen pools in these ecosystems. Grazing, one of the primary land-use practices in alpine grasslands, directly shapes the allocation, storage, and utilization of carbon and nitrogen resources by both plants and soil microbes.
Methods To investigate the effects of different grazing regimes on alpine grassland carbon and nitrogen pools, a field experiment was conducted in Xihai Town, Haibei Prefecture, Qinghai Province. The experiment included six treatments: only yak grazing (YG), only Tibetan sheep grazing (SG), mixed grazing of yak and Tibetan sheep at ratios of 1:2 (MG1:2), 1:4 (MG1:4), and 1:6 (MG1:6), as well as a no-grazing control (CK).
Important findings The results revealed that under no-grazing conditions, the plant community carbon pool and microbial biomass carbon pool were 930.81 and 58.43 g·m^-2, respectively. Yak grazing significantly reduced the plant community carbon pool, but had no effect on microbial biomass carbon pool. Similarly, mixed grazing treatments decreased the plant community carbon pool, but notably increased microbial biomass carbon pool. Regarding nitrogen pools, the no-grazing treatment had plant community nitrogen and microbial biomass nitrogen pools of 20.50 and 11.87 g·m^-2, respectively. Both yak and Tibetan sheep grazing did not alter plant community nitrogen pools, yet significantly increased microbial biomass nitrogen pool. In contrast, mixed grazing significantly reduced plant community nitrogen pools, but leaved microbial biomass nitrogen unchanged. The above results indicate that even under moderate grazing intensities, different grazing regimes exert divergent effects on the plant community and microbial carbon and nitrogen pools in alpine grasslands.

Key words: grazing, alpine grassland, plant, microorganism, carbon pool, nitrogen pool

LÜ Wei-Dong, DONG Quan-Min, SUN Cai-Cai, LIU Wen-Ting, LIU Yu-Zhen, ZHANG Zhen-Xiang, LI Meng-Qi, YANG Xiao-Xia. Effects of yak and Tibetan sheep grazing on plant and microbial carbon and nitrogen pools in alpine grassland[J]. Chin J Plant Ecol, 2025, 49(9): 1424-1433.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2025.0006

https://www.plant-ecology.com/EN/Y2025/V49/I9/1424

Figures/Tables 5

References 33

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处理 Treatment	牦牛数量(头) Number of yaks (head)	藏羊数量(只) Number of Tibetan sheep (head)	小区面积 Area of plot (hm²)	小区重复个数 Number of plots
不放牧 CK	0	0	0.05	3
藏羊单牧 SG	0	2	0.17	3
牦牛单牧 YG	1	0	0.26	3
牦牛藏羊1:2混牧 MG1:2	1	2	0.43	3
牦牛藏羊1:4混牧 MG1:4	1	4	0.60	3
牦牛藏羊1:6混牧 MG1:6	1	6	0.76	3

处理 Treatment	牦牛数量(头) Number of yaks (head)	藏羊数量(只) Number of Tibetan sheep (head)	小区面积 Area of plot (hm²)	小区重复个数 Number of plots
不放牧 CK	0	0	0.05	3
藏羊单牧 SG	0	2	0.17	3
牦牛单牧 YG	1	0	0.26	3
牦牛藏羊1:2混牧 MG1:2	1	2	0.43	3
牦牛藏羊1:4混牧 MG1:4	1	4	0.60	3
牦牛藏羊1:6混牧 MG1:6	1	6	0.76	3

	CK	SG	YG	MG1:2	MG1:4	MG1:6
生物量 Biomass (g·m^-2)
地上 Aboveground	168.9 ± 15.29^ab	161.7 ± 8.14^ab	182.4 ± 14.88^a	114.5 ± 13.18^c	117.0 ± 6.85^c	141.1 ± 5.52^bc
根系 Root	2 569.2 ± 292.6^a	2 344.7 ± 215.1^a	2 391.5 ± 237.7^a	1 321.9 ± 166.1^b	1 483.4 ± 129.3^b	1 648.1 ± 200.4^b
碳含量 Carbon content (g·kg^-1)
地上 Aboveground	409.2 ± 0.60^a	372.4 ± 0.53^e	412.9 ± 1.96^a	379.7 ± 2.46^d	385.8 ± 2.28^c	397.4 ± 0.90^b
根系 Root	335.2 ± 3.98^b	327.1 ± 2.47^b	255.1 ± 3.12^d	297.6 ± 9.10^c	355.4 ± 1.48^a	322.1 ± 1.34^b
氮含量 Nitrogen content (g·kg^-1)
地上 Aboveground	14.1 ± 0.43^c	14.5 ± 0.12^c	18.7 ± 0.27^a	15.0 ± 0.45^bc	15.8 ± 0.18^b	14.7 ± 0.27^c
根系 Root	7.1 ± 0.15^d	7.5 ± 0.08^c	6.7 ± 0.07^e	8.4 ± 0.09^a	7.9 ± 0.06^b	6.8 ± 0.05^e
碳氮比 C:N
地上 Aboveground	29.3 ± 0.93^a	25.6 ± 0.20^bc	22.1 ± 0.27^d	25.4 ± 061^c	24.4 ± 0.22^c	27.0 ± 0.55^b
根系 Root	47.5 ± 1.47^a	43.7 ± 0.68^b	37.9 ± 0.57^c	35.6 ± 1.35^c	44.7 ± 0.46^ab	47.2 ± 0.50^a
容重 Bulk density (g·cm^-3)
	1.1 ± 0.02^ab	1.0 ± 0.01^b	1.1 ± 0.01^a	1.0 ± 0.04^ab	1.0 ± 0.02^ab	0.9 ± 0.02^b

	CK	SG	YG	MG1:2	MG1:4	MG1:6
生物量 Biomass (g·m^-2)
地上 Aboveground	168.9 ± 15.29^ab	161.7 ± 8.14^ab	182.4 ± 14.88^a	114.5 ± 13.18^c	117.0 ± 6.85^c	141.1 ± 5.52^bc
根系 Root	2 569.2 ± 292.6^a	2 344.7 ± 215.1^a	2 391.5 ± 237.7^a	1 321.9 ± 166.1^b	1 483.4 ± 129.3^b	1 648.1 ± 200.4^b
碳含量 Carbon content (g·kg^-1)
地上 Aboveground	409.2 ± 0.60^a	372.4 ± 0.53^e	412.9 ± 1.96^a	379.7 ± 2.46^d	385.8 ± 2.28^c	397.4 ± 0.90^b
根系 Root	335.2 ± 3.98^b	327.1 ± 2.47^b	255.1 ± 3.12^d	297.6 ± 9.10^c	355.4 ± 1.48^a	322.1 ± 1.34^b
氮含量 Nitrogen content (g·kg^-1)
地上 Aboveground	14.1 ± 0.43^c	14.5 ± 0.12^c	18.7 ± 0.27^a	15.0 ± 0.45^bc	15.8 ± 0.18^b	14.7 ± 0.27^c
根系 Root	7.1 ± 0.15^d	7.5 ± 0.08^c	6.7 ± 0.07^e	8.4 ± 0.09^a	7.9 ± 0.06^b	6.8 ± 0.05^e
碳氮比 C:N
地上 Aboveground	29.3 ± 0.93^a	25.6 ± 0.20^bc	22.1 ± 0.27^d	25.4 ± 061^c	24.4 ± 0.22^c	27.0 ± 0.55^b
根系 Root	47.5 ± 1.47^a	43.7 ± 0.68^b	37.9 ± 0.57^c	35.6 ± 1.35^c	44.7 ± 0.46^ab	47.2 ± 0.50^a
容重 Bulk density (g·cm^-3)
	1.1 ± 0.02^ab	1.0 ± 0.01^b	1.1 ± 0.01^a	1.0 ± 0.04^ab	1.0 ± 0.02^ab	0.9 ± 0.02^b