Spatial variability of topsoils and vegetation in a grazed steppe ecosystem in Inner Mongolia (PR China)
Spatial variability of topsoils and vegetation in a grazed steppe ecosystem in Inner Mongolia (PR China)
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DOI：
10.1002/jpln.200700309
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发表时间：
2009-02
影响因子：
2.5
通讯作者：
M. Steffens;A. Kölbl;M. Giese;C. Hoffmann;K. Totsche;L. Breuer;I. Kögel‐Knabner
中科院分区：
文献类型：
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作者：
M. Steffens;A. Kölbl;M. Giese;C. Hoffmann;K. Totsche;L. Breuer;I. Kögel‐Knabner
从文献中还不清楚停止放牧如何影响表土和植被特性的空间分布。因此，本研究的目的是阐明长期放牧围封是否增加了中国东北草原生态系统表层土壤和植被特性的空间异质性。计算了堆积密度、有机碳（OC）、总氮和总硫浓度、δ 13 C、pH、Ah-Horizon厚度、植被覆盖度和地上生物量的变异函数和交叉变异函数。5个不同放牧强度（自1979年以来未放牧，自1999年以来未放牧，冬季放牧，连续放牧，严重放牧）的网站进行了采样，两个不同的网格大小，允许探索规模效应。小网格（15米间距，5米嵌套采样）表现出不同的空间结构相比，大网格（50米间距，10米嵌套采样）。小网格内的空间分布随放牧强度的变化而变化。一般来说，表层土壤性质的异质性增加放牧强度从均匀的斑块分布。我们把这归因于植被恢复/演替和沉积的风吹材料在未放牧地区。自1999年以来未放牧的地块表现出不同的空间依赖性比连续和严重放牧的地块，但尚未达到高变异性的情节是自1979年以来未放牧。大网格采样没有检测到小规模的变化或放牧的影响，但表现出空间的依赖性，归因于地形或土壤侵蚀/沉积。低OC浓度和低AH厚度与山顶和肩膀的位置，导致在这些地形单位的OC库存较低。
It is not clear from the literature how the spatial distribution of topsoil and vegetation properties is affected by grazing cessation. Thus, the objective of this study was to elucidate if long-term grazing exclosure increases spatial heterogeneity of topsoil and vegetation properties in a steppe ecosystem in NE China. Variograms and crossvariograms were calculated for bulk density, organic carbon (OC), total N, and total S concentration, δ 13 C, pH, Ah horizon thickness, vegetation cover, and aboveground biomass. Five sites with different grazing intensities (ungrazed since 1979, ungrazed since 1999, winter grazing, continuously grazed, heavily grazed) were sampled with two different grid sizes, allowing the exploration of scale effects. Small grids (15 m spacing, 5 m nested sampling) exhibited a different spatial structure compared to large grids (50 m spacing, 10 m nested sampling). Spatial distribution in small grids changed with grazing intensity. Generally, heterogeneity of topsoil properties increased with decreasing grazing intensity from a homogeneous to a patchy distribution. We attribute this to vegetation recovery/succession and deposition of windblown material in ungrazed areas. The plot ungrazed since 1999 showed different spatial dependencies than continuously and heavily grazed plots, but has not yet reached the high variability of the plot which was ungrazed since 1979. Large grid sampling did not detect small-scale variability or grazing impacts, but showed spatial dependencies that were attributed to topography or soil erosion/deposition. Low OC concentration and low Ah thickness were associated with hilltop and shoulder positions, resulting in lower OC stocks at these topographic units.