希拉穆仁草原近自然恢复状态下植被-土壤响应特征

通过对内蒙古阴山北麓围封区域草原近自然状态下植被群落特征及其土壤颗粒物理特性的研究,探讨草地群落与土壤颗粒物理特性在自然风蚀条件下的特征。结果表明:(1)草地全覆盖时以羊草、赖草为优势种,当草地盖度下降为40%以下时以指示草地退化的冷蒿为优势种;且随着植被盖度的降低,草地植物群落生物量呈降低趋势,Shannon-Wiener指数、Simpson指数均呈现出先升高后降低的趋势;(2)草地植被覆盖度对地表土壤颗粒分形维数有显著影响(P0.05),随着盖度的降低,其地表土壤颗粒分形维数呈显著降低趋势,地表土壤颗粒粗化明显;(3)在近自然状态下,草地植被覆盖较低时,地表0—1 cm土壤颗粒粗粒化现象尤为显著,粒度累计差异达到1 mm,垂直结构上表现为由3—5 cm、1—3 cm土层至0—1 cm土层,土壤颗粒粗粒化程度加重,粗颗粒粒度累积差异分别出现在0.1、0.25、1 mm;(4)在近自然状态下,随着草地植被盖度增加,表层土壤受植物遮蔽,得到有效保护,土壤颗粒逐渐细化,容重也缓慢下降。在近自然状态下,草地及土壤环境发生有层次且多样性的变化,草地植被的斑块状变化使得希拉穆仁围封区草原在近原始状态下出现自然风蚀现象成为可能。

Response of the vegetation soil under almost-natural restoration in the Xilamuren grassland

We studied the soil physical properties and characteristics of plant communities under almost-natural states in enclosed grasslands at the northern foot of the Yinshan Mountain in Inner Mongolia. The objective was to explore the characteristics of grassland communities and soil particles under natural erosion conditions. The results showed that (1) the dominant species in full coverage grassland were Leymus chinensis and Leymus secalinus. The indicator species of grassland degradation, Artemisia frigid, was the dominant species when the vegetation coverage was <40%. The biomass of the grassland community decreased with the vegetation coverage, and the Shannon-Wiener and Simpson indexes firstly increased and then decreased; (2) the fractal dimension was significantly influenced by the grassland coverage at the surface soil; it decreased significantly with decreasing coverage(P < 0.05), and the sand content obviously increased in the surface soil; (3) when the coverage was lower, coarse-grained soil particles were dominant in the 0-1 cm layer, and the accumulative particle difference was up to 1 mm. This showed that the degree of coarse-grained particles increased from the 3-5 cm layer and 1-3 cm layer to the 0-1 cm layer in the vertical soil structure. The cumulative differences of coarse particles were 0.1, 0.25, and 1 mm in the 3-5, 1-3 cm, and 0-1 cm layers, respectively; and (4) with increased coverage, surface soil was covered and effectively protected, and soil particles gradually become finer and the bulk density slowly reduced. Under the almost-natural state, the grassland and soil environment changed hierarchically and diversely, and the patchy changes of grassland vegetation resulted in natural erosion in the enclosed meadow in the Xilamuren grassland.