Grazing effects on soil chemical and physical properties in a semiarid steppe of Inner Mongolia (P.R. China)
Grazing effects on soil chemical and physical properties in a semiarid steppe of Inner Mongolia (P.R. China)
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DOI：
10.1016/j.geoderma.2007.09.004
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发表时间：
2008-01
期刊：
影响因子：
6.1
通讯作者：
M. Steffens;A. Kölbl;K. Totsche;I. Kögel‐Knabner
中科院分区：
文献类型：
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作者：
M. Steffens;A. Kölbl;K. Totsche;I. Kögel‐Knabner
从文献中还不清楚，在草原生态系统中，过度放牧是否会导致表层土壤的物理和化学参数恶化。我们在中国北方的5个不同放牧强度的地点，从1979年以来的未放牧到严重放牧，在540个采样点，0-4厘米的深度。分析每个样品的堆积密度、有机碳（OC）、总氮（N）、总硫（S）和pH。使用一般统计和探索性分析（ANOVA，Kruskal-Wallis）分析数据集。由于样本量大，我们能够检测到所有参数的平均值变化小于10%，统计功效为90%，显著性水平为0.01。容重随放牧强度的增加而显著增加。有机碳、全氮和全硫含量随放牧强度的增加而显著降低。未检测到对pH或C/N比的影响。不同放牧样地之间的C/S和N/S比值存在显著差异，这些差异表明，随着有机质下降或稀释凋落物的输入减少，放牧区与未放牧区相比硫的相对积累。使用测得的堆积密度计算上部4 cm的元素储备的OC、总N和总S。数据显示，在严重放牧的网站上的所有三种元素的量显着较低，但没有显着差异的其他地区。此外，计算元素储量时使用的是当量质量，而不是体积密度，以考虑放牧后体积密度的变化。结果表明，随着放牧强度的增加，土壤有机碳、全氮和全硫含量显著降低。有机碳、全氮和全硫含量对不同放牧强度的响应相似，呈极显著正相关。OC浓度与容重呈显著负相关。我们发现，只有在长期的放牧停止的影响，减少或排除放牧没有改善效果，可以检测到五年后停止放牧。排除25年后，发现所有参数的值均存在显著差异。因此，草原表层土壤的物理和化学参数显着恶化后，重放牧，保持稳定，如果减少或禁牧5年，禁牧25年后显着恢复。
It is not clear from the literature whether heavy grazing leads to a deterioration of physical and chemical parameters of topsoils in steppe ecosystems. We sampled five sites in northern China with different grazing intensities, ranging from ungrazed since 1979 to heavily grazed, at 540 sampling points to a depth of 0–4 cm. Each sample was analysed for bulk density, organic carbon (OC), total nitrogen (N), total sulphur (S) and pH. The dataset was analysed using general statistics and explorative analysis (ANOVA, Kruskal–Wallis). As a result of the large number of samples, we were able to detect a change in the mean value of all parameters of less than 10%, with a statistical power of 90% and a level of significance of 0.01. Bulk density increased significantly with increasing grazing intensity. Organic carbon, total N and total S concentrations decreased significantly with increasing grazing intensity. No effect on the pH or C/N ratio was detected. Significant differences in C/S and N/S ratios between differently grazed plots were found. These differences point towards a relative accumulation of sulphur in grazed compared to ungrazed areas following an increased organic matter decline or lower inputs of diluting litter. Elemental stocks of the upper 4 cm were calculated for OC, total N and total S using the measured bulk densities. The data revealed significantly lower amounts for all three elements on the heavily grazed site, but no significant differences for the other areas. In addition, elemental stocks were calculated using an equivalent mass instead of bulk density to take into account changes in bulk density following grazing. This revealed a highly significant decrease for OC, total N and total S with increasing grazing intensity. OC, total N and total S concentrations respond similarly to different grazing intensities, showing highly significant positive correlations. OC concentrations and bulk densities were significantly negatively correlated. We found effects of grazing cessation only in the long-term, as no ameliorating effects of reduced or excluded grazing could be detected five years after grazing cessation. After 25 years of exclusion, significantly different values were found for all parameters. Thus, physical and chemical parameters of steppe topsoils deteriorated significantly following heavy grazing, remained stable if grazing was reduced or excluded for five years, and recovered significantly after 25 years of grazing exclusion.