不同放牧强度下蒙古栎天然林土壤物理性质及土壤质量综合评价

A comprehensive evaluation regarding the effect of various grazing intensities on the soil physical properties of natural Quercus mongolica forest

【目的】为定量分析不同放牧强度对冀北山地蒙古栎天然林林下土壤物理性质的影响,以及探究放牧干扰作用下的森林土壤物理性质的评价体系。【方法】采集放牧强度重度(HG)、中度(MG)、轻度(LG)下蒙古栎天然林0~20 cm土壤为研究对象,以及立地条件相同且长期封禁处理的作为对照组(CK)。对各放牧强度的土壤物理因子进行单因素方差分析(ANOVA)、灰色关联度分析来揭示不同放牧强度对蒙古栎天然林土壤物理性质的影响。应用主成分分析法、多维空间坐标综合评定值累加法、熵权-TOPSIS法对放牧干扰下的土壤物理质量进行综合评价。【结果】1)土壤中粗粉粒、沙粒、黏粒含量随放牧强度的增加而增加,中粉粒、细粉粒含量随放牧强度的增加而减少,放牧强度对土壤分形维数的影响并不显著。2)土壤容重随放牧强度的增加而增加,其余物理因子均随放牧强度的增加而减小,重度放牧组与其他各放牧组各土壤物理因子间均存在显著差异。3)所选用的3种评价方法均表现出一致的排序结果:CK>LG>MG>HG。【结论】针对于放牧后对林下土壤物理性质产生的影响,综合考虑后得出:轻度放牧会促进林下凋落物的分解并有利于改善林下土壤物理质量,过度放牧会对林下土壤造成不良影响。放牧对林下土壤的影响是多层次的,仍需加强长期监测与深入研究。

【Objective】In order to quantitatively analyze the effects of different grazing intensities on the understory soil physical properties of natural Quercus mongolica forest and explore the evaluation system of forest soil physical properties under grazing disturbance in mountain areas of northern Hebei province.【Method】Soil of 0-20 cm in natural Q.mongolica forest under heavy grazing(HG),moderate grazing(MG),and light grazing(LG)were collected as the research object,and the same site conditions and long-term closed treatment were taken as the control group(CK).One-way analysis of variance(ANOVA)and grey correlative degree analysis were conducted to reveal the effects of different grazing intensity on soil physical properties of natural Q.mongolica forest.Principal component analysis method,multidimensional coordinate-synthetic-evaluation method and entropy weight TOPSIS method were used to evaluate the soil physical quality under grazing disturbance.【Result】1)The contents of coarse silt,sand grain and clay in soil increased with the increase of grazing intensity,while the contents of medium silt and fine silt decreased with the increase of grazing intensity.The effect of grazing intensity on soil fractal dimension was not significant.2)The soil bulk density increased with the grazing intensity,and other physical factors decreased as the grazing intensity increased.There were significant differences in each soil physical factor between the heavy grazing group and other grazing groups.3)All the three evaluation methods showed consistent ranking results:CK>LG>MG>HG.【Conclusion】In view of the impact of grazing on the physical properties of understory soil,it is concluded that light grazing can promote the decomposition of understory litters and improve the physical quality of understory soil,while overgrazing may cause adverse effects on understory soil.The effects of grazing on the understory soil are multi-level,so it is necessary to strengthen the long-term monitoring and in-depth study.