内蒙古温带草原不同放牧强度和围栏封育对凋落物分解的影响

doi:10.17521/cjpe.2016.00051

摘要/Abstract

摘要：

放牧和围封通过影响植物群落结构和土壤微环境来调控草地生态系统的碳循环。该研究在内蒙古温带草原设置轻度放牧后围封、轻度放牧、重度放牧后围封、重度放牧4种样地, 通过测定干旱年(2011年)和湿润年(2012年)地上、地下凋落物产量、质量及其分解速率和土壤养分含量, 分析不同放牧强度对凋落物形成和分解的影响, 以及围栏封育对生态系统恢复的作用。结果表明: 重度放牧地上凋落物产量和分解速率均高于轻度放牧。干旱年轻度放牧样地地下凋落物产量和分解速率高于重度放牧, 湿润年相反。短期围封显著提高了凋落物产量, 轻度放牧样地围封后地上凋落物分解速率和养分循环加快, 而重度放牧样地围封后地上凋落物分解减慢。因此, 与重度放牧相比, 轻度放牧草地的恢复更适合采用围栏封育措施; 而重度放牧草地的恢复可能还需辅以必要的人工措施。降水显著促进地上、地下凋落物形成和分解。地下凋落物的生产和分解受降水年际波动影响较大, 重度放牧草地对降水变化的敏感度比轻度放牧草地高。地上凋落物分解速率与凋落物N含量显著正相关, 与土壤全N显著负相关, 与地上凋落物C:N和木质素:N相关性不大; 地下凋落物分解速率与凋落物C、C:N和纤维素含量显著负相关。该研究结果将为不同放牧强度的草地生态系统恢复和碳循环研究提供理论依据。

关键词: 放牧强度, 围栏封育, 降水, 凋落物分解, 凋落物生产, 凋落物质量

Abstract:

Aims Grazing intensity and grazing exclusion affect ecosystem carbon cycling by changing the plant community and soil micro-environment in grassland ecosystems. The aims of this study were: 1) to determine the effects of grazing intensity and grazing exclusion on litter decomposition in the temperate grasslands of Nei Mongol; 2) to compare the difference between above-ground and below-ground litter decomposition; 3) to identify the effects of precipitation on litter production and decomposition. Methods We measured litter production, quality, decomposition rates and soil nutrient contents during the growing season in 2011 and 2012 in four plots, i.e. light grazing, heavy grazing, light grazing exclusion and heavy grazing exclusion. Quadrate surveys and litter bags were used to measure litter production and decomposition rates. All data were analyzed with ANOVA and Pearson’s correlation procedures in SPSS. Important findings Litter production and decomposition rates differed greatly among four plots. During the two years of our study, above-ground litter production and decomposition in heavy-grazing plots were faster than those in light-grazing plots. In the dry year, below-ground litter production and decomposition in light-grazing plots were faster than those in heavy-grazing plots, which is opposite to the findings in the wet year. Short-term grazing exclusion could promote litter production, and the exclusion of light-grazing could increase litter decomposition and nutrient cycling. In contrast, heavy-grazing exclusion decreased litter decomposition. Thus, grazing exclusion is beneficial to the restoration of the light-grazing grasslands, and more human management measures are needed during the restoration of heavy-grazing grasslands. Precipitation increased litter production and decomposition, and below-ground litter was more vulnerable to the inter-annual change of precipitation than above-ground litter. Compared to the light-grazing grasslands, heavy-grazing grasslands had higher sensitivity to precipitation. The above-ground litter decomposition was strongly positively correlated with the litter N content (R²= 0.489, p < 0.01) and strongly negatively correlated with the soil total N content (R² = 0.450, p < 0.01), but it was not significantly correlated with C:N and lignin:N. Below-ground litter decomposition was negatively correlated with the litter C (R² = 0.263, p < 0.01), C:N (R² = 0.349, p < 0.01) and cellulose content (R² = 0.460, p < 0.01). Our results will provide a theoretical basis for ecosystem restoration and the research of carbon cycling.

Key words: grazing intensity, grazing exclusion, precipitation, litter decomposition, litter production, litter quality

杨丽丽, 龚吉蕊, 王忆慧, 刘敏, 罗亲普, 徐沙, 潘琰, 翟占伟. 内蒙古温带草原不同放牧强度和围栏封育对凋落物分解的影响. 植物生态学报, 2016, 40(8): 748-759. DOI: 10.17521/cjpe.2016.00051

Li-Li YANG, Ji-Rui GONG, Yi-Hui WANG, Min LIU, Qin-Pu LUO, Sha XU, Yan PAN, Zhan-Wei ZHAI. Effects of grazing intensity and grazing exclusion on litter decomposition in the temperate steppe of Nei Mongol, China. Chinese Journal of Plant Ecology, 2016, 40(8): 748-759. DOI: 10.17521/cjpe.2016.00051

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2016.00051

https://www.plant-ecology.com/CN/Y2016/V40/I8/748

图/表 8

表1 样地基本信息(平均值±标准误差, n = 5)

Table 1 Basic information of the sampling plots (mean ± SE, n = 5)

样地基本信息 Basic information of the sampling plots	轻度放牧样地 Light grazing plot	重度放牧样地 Heavy grazing plot
平均高度 Average height (cm)	13.11 ± 1.46^b	19.85 ± 1.13^a
平均盖度 Average coverage (%)	57.36 ± 3.92^a	65.29 ± 2.55^a
地上生物量 Above-ground biomass (g·m^-2)	62.26 ± 0.89^b	108.76 ± 5.51^a
粪便数 Number of feces (No.·m^-2)	575.50 ± 2.04^b	1 230.00 ± 12.25^a

表2 样地、年份及其交互作用对地上凋落物产量、质量、分解速率和土壤养分的影响

Table 2 The impact of sampling plots, year and their interactions on above- ground litter production, quality, decomposition and soil total C and N

	Y	P	Y × P
凋落物产量 Litter production	< 0.01	< 0.01	< 0.01
凋落物分解速率 Litter decomposition	< 0.01	< 0.01	< 0.01
凋落物C 含量 Litter C content	< 0.01	< 0.01	0.02
凋落物N含量 Litter N content	0.01	0.04	0.01
凋落物纤维素含量 Litter cellulose content	< 0.01	< 0.01	0.01
凋落物木质素含量 Litter lignin content	< 0.01	0.02	0.03
凋落物C:N Litter C:N	< 0.01	< 0.01	0.27
凋落物木质素:N Litter lignin:N	< 0.01	< 0.01	< 0.01
土壤全C Soil total C	0.01	< 0.01	< 0.01
土壤全N Soil total N	< 0.01	0.01	0.03

表3 样地、年份及其交互作用对地下凋落物产量、质量、分解速率的影响

Table 3 The impact of sampling plots, year and their interactions on below-ground litter production, quality and decomposition rates

	Y	P	Y × P
凋落物产量 Litter production	< 0.01	< 0.01	< 0.01
凋落物分解速率 Litter decomposition	< 0.01	< 0.01	< 0.01
凋落物C含量 Litter C content	< 0.01	< 0.01	0.09
凋落物N含量 Litter N content	0.07	< 0.01	< 0.01
凋落物纤维素含量 Litter cellulose content	< 0.01	< 0.01	0.04
凋落物木质素含量 Litter lignin content	0.45	< 0.01	< 0.01
凋落物C:N Litter C:N	< 0.01	0.05	< 0.01
凋落物木质素:N Litter lignin:N	0.40	0.07	< 0.01

图1 2011和2012年4个样地地上凋落物(A)和地下凋落物(B)产量(平均值±标准误差)。不同大写字母表示2011年凋落物产量在不同样地之间差异显著, 不同小写字母表示2012年凋落物产量在不同样地之间差异显著(p < 0.05)。HG, 重度放牧样地; HGE, 重度放牧后围封样地; LG, 轻度放牧样地; LGE, 轻度放牧后围封样地。

Fig. 1 Above-ground (A) and below-ground (B) litter production in the four treatment plots in 2011 and 2012 (mean ± SE). Capital letters indicate significant difference in litter production between different plots in 2011 at 0.05 levels, and lowercase letters indicate significant difference in litter production between different plots in 2012 at 0.05 levels. HG, heavy-grazing; HGE, heavy-grazing exclusion; LG, light-grazing; LGE, light-grazing exclusion .

图2 2011和2012年4个样地地上凋落物C含量(A)、N含量(B)、C:N (C)、纤维素含量(D)、木质素含量(E)和木质素:N (F)(平均值±标准误差), 不同大写字母表示2011年地上凋落物质量在不同样地之间差异显著, 不同小写字母表示2012年地上凋落物质量在不同样地之间差异显著(p < 0.05)。HG, 重度放牧样地; HGE, 重度放牧后围封样地; LG, 轻度放牧样地; LGE, 轻度放牧后围封样地。

Fig. 2 Above-ground litter C content (A), N content (B), C:N (C), cellulose content (D), lignin content (E) and lignin:N (F) in four plots in 2011 and 2012 (mean ± SE). Capital letters indicate significant difference in litter quality between different plots in 2011 at 0.05 levels, and lowercase letters indicate significant difference in litter quality between different plots in 2012 at 0.05 levels. HG, heavy-grazing; HGE, heavy-grazing exclusion; LG, light-grazing; LGE, light-grazing exclusion.

图3 2011和2012年4个样地地下凋落物C含量(A)、N含量(B)、C:N (C)、纤维素含量(D)、木质素含量(E)和木质素:N (F) (平均值±标准误差)。不同大写字母表示2011年地下凋落物质量在不同样地之间差异显著, 不同小写字母表示2012年地下凋落物质量在不同样地之间差异显著(p < 0.05)。HG, 重度放牧样地; HGE, 重度放牧后围封样地; LG, 轻度放牧样地; LGE, 轻度放牧后围封样地。

Fig. 3 Below-ground litter C content (A), N content (B), C:N (C), cellulose content (D), lignin content (E) and lignin:N (F) in four plots in 2011 and 2012 (mean ± SE). Different capital letters indicate significant difference in litter quality between different plots in 2011 at 0.05 levels, and different lowercase letters indicate significant difference in litter quality between different plots in 2012 at 0.05 levels. HG, heavy-grazing; HGE, heavy-grazing exclusion; LG, light-grazing; LGE, light-grazing exclusion.

图4 2011和2012年4个样地地上凋落物(A)和地下凋落物(B)分解速率k (平均值±标准误差)。不同大写字母表示2011年凋落物分解速率在不同样地之间差异显著; 不同小写字母表示2012年凋落物分解速率在不同样地之间差异显著(p < 0.05)。HG, 重度放牧样地; HGE, 重度放牧后围封样地; LG, 轻度放牧样地; LGE, 轻度放牧后围封样地。

Fig. 4 Aboveground (A) and belowground (B) litter decomposition rates (k) in four plots in 2011 and 2012 (mean ± SE). Different capital letters indicate significant difference in litter decomposition rate between different plots in 2011 at 0.05 levels, and different lowercase letters indicate significant difference in litter decomposition rate between different plots in 2012 at 0.05 levels. HG, heavy-grazing; HGE, heavy-grazing exclusion; LG, light-grazing; LGE, light-grazing exclusion.

图5 2011和2012年4个样地土壤全C (A)和全N (B)含量(平均值±标准误差)。不同大写字母表示2011年土壤C、N在不同样地之间差异显著, 不同小写字母表示2012年土壤C、N在不同样地之间差异显著(p < 0.05)。HG, 重度放牧样地; HGE, 重度放牧后围封样地; LG, 轻度放牧样地; LGE, 轻度放牧后围封样地。

Fig. 5 Soil total C (A) and total N content (B) in four plots in 2011 and 2012 (mean ± SE). Different capital letters indicate significant difference in soil nutrient content between different plots in 2011 at 0.05 levels, and different lowercase letters indicate significant difference in soil nutrient content between different plots in 2012 at 0.05 levels. HG, heavy-grazing; HGE, heavy-grazing exclusion; LG, light-grazing; LGE, light-grazing exclusion.

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