CHARACTERISTICS OF SOIL NITROGEN AND CARBON OF PASTURES UNDER DIFFERENT MANAGEMENT IN NORTHWESTERN SICHUAN

doi:10.17521/cjpe.2005.0039

Abstract

Abstract:

Different methods of pasture management have been adopted in individualized pastures of northwestern Sichuan, one of the most important pastoral areas in China. In this paper, common analytical chemistry and barometric process separation methods were used to determine soil N and C pools, denitrification rates, gross nitrification rates, and N 2O and CO 2 flux rates of pastures under different management methods, including natural pasture, fenced pasture, tilled pasture and artificial pasture. The results indicated that SOM (Soil organic matter) and total N in soils of the study area were 101.8 and 5.1 g·kg -1, respectively, which were notably lower than 181.3 and 7.4 g·kg -1 of other typical sub-alpine soils. In contrast to common belief, the content of NO 3 --N was three-to-eleven times higher than that of NH 4 +-N, which was probably caused by the anthropogenic disturbance. There was a significant effect of different methods of pasture management to N and C pools, N transformation rates and soil respiration. After fence, SOM and total N increased notably. For example, fenced pasture was 61% and 58% and tilled pasture was 46% and 51% higher than natural pasture in these two respects, respectively. Accordingly, N transformation rates and soil respiration rates accelerated a lot, especially in soils of tilled pasture. For example, in soils of tilled pasture gross nitrification and N 2O flux rate were 5.1 times and 2.4 times that of natural pasture. Thus, although tillage in spring might help to enhanced crop yields (or pasturage), it also runs a great ecological risk including increased emissions of CO 2 and N 2O to the atmosphere and leaching of NO 3 - to ground water. This research also found that the gross nitrification rates were 20-93 times higher than net nitrification rates, and thus net nitrification rates do not provide valuable information on the dynamic character of soil nitrification in this high-altitude region.

Key words: Northwestern Sichuan, Sub-alpine meadow, Pasture management, Denitrification, Gross nitrification

SUN Geng, WU Ning, LUO Peng. CHARACTERISTICS OF SOIL NITROGEN AND CARBON OF PASTURES UNDER DIFFERENT MANAGEMENT IN NORTHWESTERN SICHUAN[J]. Chin J Plant Ecol, 2005, 29(2): 304-310.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2005.0039

https://www.plant-ecology.com/EN/Y2005/V29/I2/304

Figures/Tables 8

References 23

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草地类型 Types of pasture	容重 Bulk density (g·cm^-3)	pH	8月平均土壤温度 Soil mean temperature in August (℃)	8月平均土壤含水量 Soil mean moisture in August (kg·kg^-1)	主要植物种类 Main plant species
天然放牧草地 Natural pasture	1.344	6.42	13.3	0.31	丛生苔草 (Carex caespifosa) 、腋花马先蒿 (Pedicularis axillaris) 、多茎委陵菜 (Potentilla lancinata)
围栏草地 Fenced pasture	1.268	6.21	13.7	0.34	光盘早熟禾 (Poa elanataleng) 、腋花马先蒿 (Pedicularis axillaris) 、多茎委陵菜 (Potentilla lancinata)
翻耕草地 Tilled pasture	1.018	6.30	14.0	0.37	四齿蚤缀 (Arenaria quadridentata) 、腋花马先蒿 (Pedicularis axillaris) 、多茎委陵菜 (Potentilla lancinata)
人工草地 Artificial pasture	1.185	6.25	16.5	0.32	垂穗披碱草 Elymus nutans

草地类型 Types of pasture	容重 Bulk density (g·cm^-3)	pH	8月平均土壤温度 Soil mean temperature in August (℃)	8月平均土壤含水量 Soil mean moisture in August (kg·kg^-1)	主要植物种类 Main plant species
天然放牧草地 Natural pasture	1.344	6.42	13.3	0.31	丛生苔草 (Carex caespifosa) 、腋花马先蒿 (Pedicularis axillaris) 、多茎委陵菜 (Potentilla lancinata)
围栏草地 Fenced pasture	1.268	6.21	13.7	0.34	光盘早熟禾 (Poa elanataleng) 、腋花马先蒿 (Pedicularis axillaris) 、多茎委陵菜 (Potentilla lancinata)
翻耕草地 Tilled pasture	1.018	6.30	14.0	0.37	四齿蚤缀 (Arenaria quadridentata) 、腋花马先蒿 (Pedicularis axillaris) 、多茎委陵菜 (Potentilla lancinata)
人工草地 Artificial pasture	1.185	6.25	16.5	0.32	垂穗披碱草 Elymus nutans

草地类型 Types of pasture	7月 July					8月 August
草地类型 Types of pasture	有机质SOM (g·kg^-1)	全氮Total N (g·kg^-1)	C/N	NH₄⁺-N (mg·kg^-1)	NO₃^--N (mg·kg^-1)	NH₄⁺-N (mg·kg^-1)	NO₃^--N (mg·kg^-1)
天然放牧草地 Natural pasture	69.71 ±3.40^d	3.74 ±0.008^c	10.81	1.08 ±0.03^b	13.27 ±1.30^b	4.37 ±0.11^b	20.82 ±8.39^a
围栏草地 Fenced pasture	112.39 ±3.04^b	5.92 ±0.02^b	11.01	1.95 ±0.08^a	9.23 ±0.81^c	5.25 ±0.03^a	23.85 ±0.24^a
翻耕草地 Tilled pasture	102.00 ±8.71^c	5.65 ±0.002^b	10.47	2.14 ±0.04^a	6.79 ±0.53^d	4.80 ±0.01^a	20.85 ±0.86^a
人工草地 Artificial pasture	144.64 ±0.75^a	11.51 ±0.007^a	7.29	2.29 ±0.007^a	20.44 ±0.32^a	5.42 ±0.03^a	22.90 ±1.79^a

草地类型 Types of pasture	7月 July					8月 August
草地类型 Types of pasture	有机质SOM (g·kg^-1)	全氮Total N (g·kg^-1)	C/N	NH₄⁺-N (mg·kg^-1)	NO₃^--N (mg·kg^-1)	NH₄⁺-N (mg·kg^-1)	NO₃^--N (mg·kg^-1)
天然放牧草地 Natural pasture	69.71 ±3.40^d	3.74 ±0.008^c	10.81	1.08 ±0.03^b	13.27 ±1.30^b	4.37 ±0.11^b	20.82 ±8.39^a
围栏草地 Fenced pasture	112.39 ±3.04^b	5.92 ±0.02^b	11.01	1.95 ±0.08^a	9.23 ±0.81^c	5.25 ±0.03^a	23.85 ±0.24^a
翻耕草地 Tilled pasture	102.00 ±8.71^c	5.65 ±0.002^b	10.47	2.14 ±0.04^a	6.79 ±0.53^d	4.80 ±0.01^a	20.85 ±0.86^a
人工草地 Artificial pasture	144.64 ±0.75^a	11.51 ±0.007^a	7.29	2.29 ±0.007^a	20.44 ±0.32^a	5.42 ±0.03^a	22.90 ±1.79^a

草地类型 Types of pasture	反硝化速率 Denitrification rate (mg N·kg^-1·d^-1)	总硝化速率 Gross nitrification rate (mg N·kg^-1·d^-1)	N₂O排放速率 N₂O flux rate (g N₂O·kg^-1·d^-1)	CO₂排放速率 CO₂ flux rate (g CO₂·kg^-1·d^-1)
天然放牧草地Natural pasture	2.54±1.06^c	6.66±0.38^d	0.005 1±0.001 9^b	0.23±0.13^d
围栏草地Fenced pasture	3.42±0.54^b	7.40±1.20^c	0.007 0±0.003 6^b	0.69±0.42^c
翻耕草地Tilled pasture	5.99±1.18^a	33.92±3.76^a	0.012±0.004 9^a	2.73±0.60^a
人工草地Artificial grassland	3.66±0.96^b	9.44±1.52^b	0.007 4±0.003 7^b	1.76±0.34^b