Impacts of grazing intensity and management regimes on aboveground primary productivity and compensatory growth of grassland ecosystems in Inner Mongolia

doi:10.3724/SP.J.1003.2010.300

Abstract

Abstract:

Based on the ongoing Sino-German grazing experiment, which was designed to test how grazing intensity and management regimes (traditional system vs. mixed system) would affect the aboveground net primary productivity (ANPP) and compensatory growth of a typical steppe ecosystem in Inner Mongolia dominated by Leymus chinensis and Stipa grandis. Our experimental treatments included two management systems (e.g., a traditional versus a mixed system) and seven levels of stocking (i.e., 0, 1.5, 3.0, 4.5, 6.0, 7.5, and 9.0 sheep/ha). The traditional system was managed with grazing and haymaking on two different areas. The mixed system was managed with a yearly shift between grazing and haymaking on the same area. The results showed that, with increasing stocking rate, aboveground net primary productivity (ANPP) declined in both traditional and mixed grazing plots. At high stocking rates, ANPP in mixed grazing plots was significantly higher than that in the traditional grazing plots. Our results were partially in agreement with the grazing optimization hypothesis. Under the two management regimes, and using different methods for estimating the annual ANPP, we observed overcompensation, equal-compensation, and under-compensation in plant growth along a gradient of stocking rates. Equal-compensation was generally observed in the low stocking rate plots, while under-compensation was found in the high stocking rate plots. For most systems, compensatory growth could be simulated with linear or quadratic models when the percent biomass eaten by sheep was used as an index for estimating the relative stocking rate. Our study suggests that stocking rate, grazing regime, topographic position, and methods for estimating the net aboveground productivity were all important factors determining the magnitude and directions of estimated ANPP responses to grazing.

Key words: management regimes, grazing, haymaking, stocking rate, aboveground net primary productivity, compensatory growth

Rui Xue, Shuxia Zheng, Yongfei Bai. Impacts of grazing intensity and management regimes on aboveground primary productivity and compensatory growth of grassland ecosystems in Inner Mongolia[J]. Biodiv Sci, 2010, 18(3): 300-311.

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URL: https://www.biodiversity-science.net/EN/10.3724/SP.J.1003.2010.300

https://www.biodiversity-science.net/EN/Y2010/V18/I3/300

Figures/Tables 10

Table 1 Match methods for the relationship between stocking rate (SR), relative stocking rate (RSR), aboveground net productivity (DM) and relative aboveground net productivity (RDM)

	SR	RSR1	RSR2
DM1	方法 a: SR-DM1	方法 g: RSR1-DM1	方法 k: RSR2-DM1
DM2	方法 b: SR-DM2	方法 h: RSR1-DM2	方法 l: RSR2-DM2
RDM1	方法 c: SR-RDM1	方法 i: RSR1-RDM1
RDM2	方法 d: SR-RDM2	方法 j: RSR1-RDM2
RDM3	方法 e: SR-RDM3		方法 m: RSR2-RDM3
RDM4	方法 f : SR-RDM4		方法 n: RSR2-RDM4

Table 2 Effects of stocking rate, grazing system and topography on the remained aboveground biomass of Leymus chinensis community

因素 Factor	自由度 df	均方值 Mean square	F	P
载畜率 Stocking rate (SR)	6	22445.970	11.412	0.0000
放牧制度 Grazing system (GS)	1	1683.411	0.856	0.3582
地形 Topographic position (TP)	1	248.6485	0.126	0.7233
载畜率×放牧制度 SR × GS	6	2022.704	1.028	0.4148
载畜率×地形 SR × TP	6	939.0434	0.477	0.8228
放牧制度×地形 GS × TP	1	25405.280	12.917	0.0006
载畜率×放牧制度×地形 SR×GS×TP	6	2472.729	1.257	0.2891

Fig. 1 Remained aboveground biomass of Leymus chinensis community at different stocking rates in traditional and mixed grazing systems. Different lowercase letters denote significant difference among different stocking rates at P< 0.05. TGF, Traditional grazing flat system; TGS, Traditional grazing slope system; MGF, Mixed grazing flat system; MGS, Mixed grazing slope system.

Fig. 2 Aboveground net primary productivity (ANPP) of Leymus chinensis community in traditional grazing, traditional hay and mixed grazing systems at the stocking rate of 9.0 sheep/ha in (A) flat and (B) slope blocks. Different lowercase letters denote significant difference among different grassland management types at P< 0.05. TG, Traditional grazing system; TH, Traditional haymaking system; MG, Mixed grazing system.

Fig. 3 Aboveground net productivity (A: Method a, b) and relative aboveground net productivity (B: Method c, d; C: Method e, f) of Leymus chinensis community at different stocking rates in traditional and mixed grazing systems. The abbreviations denote the same grazing systems as Fig. 1.

Table 3 Aboveground net productivity (using Method b) and relative aboveground net productivity (using Method d and f) of Leymus chinensis community at different stocking rates in traditional and mixed grazing systems

方法 Method	载畜率 Stocking rate	传统放牧平地系统TGF	传统放牧坡地系统TGS	混合利用平地系统MGF	混合利用坡地系统MGS
Method b	0	151.05^a	153.54^a	171.77^a	188.63^ab
	1.5	212.55^a	138.19^ab	95.93b^cd	241.38^a
	3.0	178.95^a	137.86^ab	112.26^b	128.2^b
	4.5	145.5^a	151.55^ab	108.98^bc	109.21^b
	6.0	163.65^a	122.02^ab	104.74^bcd	155.52^b
	7.5	130.03^a	128.27^ab	51.14^d	121.43^b
	9.0	118.05^a	78.67^b	56.69^cd	142.33^b
Method d	0	1^ab	1^a	1^a	1^ab
	1.5	1.14^a	0.89^a	0.67^ab	1.18^a
	3.0	0.53^b	0.92^a	0.61^bc	0.68^bc
	4.5	0.66^ab	0.8^a	0.4^bc	0.481^c
	6.0	0.69^ab	0.65^a	0.54^bc	0.51^c
	7.5	0.57^ab	0.62^a	0.31^c	0.77^bc
	9.0	0.57^ab	0.51^a	0.31^c	0.64^bc
Method f	0	1^a	1^ab	1^a	1^b
	1.5	1.18^a	1.02^ab	0.82^a	1.59^a
	3.0	1.39^a	1.06^ab	0.78^a	0.83^bc
	4.5	0.82^a	1.34^b	0.79^a	0.74^bc
	6.0	0.7^a	1.15^ab	0.76^a	0.64^c
	7.5	0.98^a	1.1^ab	0.31^b	0.95^b
	9.0	1.01^a	0.48^a	0.22^b	0.56^c

Fig. 4 Aboveground net productivity at different relative stocking rates in traditional and mixed grazing systems (Method h). The abbreviations denote the same grazing systems as Fig. 1.

Fig.5 Relative aboveground net productivity at different relative stocking rates in traditional and mixed grazing systems (Method j). The abbreviations denote the same grazing systems as Fig. 1.

Fig. 6 Aboveground net productivity at different relative stocking rates in traditional and mixed grazing systems (Method l). The abbreviations denote the same grazing systems as Fig. 1.

Fig. 7 Relative aboveground net productivity at different relative stocking rates in traditional and mixed grazing systems (Method n). The abbreviations denote the same grazing systems as Fig. 1.

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