晋西黄土区长期人工林恢复对土壤水分和养分性质的影响

黄土高原地区是我国水土流失和环境问题严重的地区之一,人工植被恢复可以有效改善土壤性质,提高土壤质量,明确长期人工植被恢复后土壤水分和养分性质的响应差异,有利于进一步有效改善生态环境。选取晋西黄土区自然恢复的次生林地、人工刺槐林地、人工油松林地3种典型植被恢复类型为研究对象,通过测定土壤物理性质以及有机碳、氮磷钾元素含量等土壤养分,对比分析长期不同人工林恢复条件下的差异。结果表明:(1)次生林地、刺槐林地和油松林地在0-20 cm浅层土壤的容重分别1.15,1.04,1.06 g/cm³,次生林地的容重最大,土壤容重随着土层深度的增加而增大;(2)次生林地在浅层的土壤水分状况优于刺槐林地和油松林地,土壤水分消耗期(生长季开始前)过渡到积累期(生长期开始)时,次生林土壤水分动态变化更剧烈;(3)次生林地土壤碳储量较高,油松林地土壤氮、磷储量较高。3种林地土壤养分垂直变化差异显著,且均具有明显的表聚性,有机碳、全氮、全磷、速效氮和速效钾含量均随着土层深度的增加而减少,而速效磷含量随着土层深度的变化表现为先增大再减小。以水养条件为依据,建议在植被恢复过程中多以保育次生林为主来达到较好的水碳储量等生态效益,有利于优化晋西黄土区的林分管理,促进植被恢复和生态建设。

Effects of Long-term Artificial Forest Restoration on Soil Moisture and Nutrient Characteristics in the Loess Area of Western Shanxi Province, China

The Loess Plateau has always been one of the most serious soil erosion and environmental problems regions in China. Artificial vegetation restoration can effectively improve soil properties and soil quality, therefore clarifying the responses of soil moisture and nutrient properties to long-term artificial vegetation restoration is conducive to further effectively improving the eco-environment. This study selected three typical vegetation types, including natural restoration secondary forest land, artificial Robinia pseudoacacia forest land and artificial Pinus tabulaeformis forest land, during ecological restoration in the loess region of western Shanxi. By measuring soil physical properties, soil moisture contents and soil nutrients such as organic carbon, nitrogen, phosphorus and potassium contents, the differences under the long-term artificial vegetation restorations were comparatively analyzed. The results showed that:(1) The soil bulk density of secondary forest land, Robinia pseudoacacia forest land and Pinus tabulaeformis forest land in 0-20 cm shallow layer was 1.15, 1.04 and 1.06 g/cm³, respectively. The soil bulk density increased with the increase of soil depth. (2) The soil moisture of secondary forest land in shallow layer was better than those of Robinia pseudoacacia forest land and Pinus tabulaeformis forest land. When soil moisture consumption period (before the start of growth season) transited to the accumulation period (at the beginning of the growth season), the dynamic variations of soil moisture in secondary forest land were more dramatic. (3) The soil carbon storage in secondary forest land was higher, while the soil nitrogen and phosphorus storage in Pinus tabulaeformis forest land was higher. The vertical variations of soil nutrients of the three forest lands had significant differences with accumulation in surface layer. The contents of organic carbon, total nitrogen, total phosphorus, available nitrogen and available potassium all decreased with the increase of soil depth, while the contents of available phosphorus increased first and then decreased. Considering the soil moisture and nutrient condition, it was suggested that the secondary forest should be mainly conserved in the process of vegetation restoration to achieve the better water and carbon storage and other ecological benefits, which would be conducive to the optimization of stand management, and the promotion of vegetation restoration and ecological construction in the western Shanxi loess region.