黄土高原小流域植被恢复的土壤水分和养分权衡效应研究

  目的  明确黄土高原植被恢复影响下土壤水源涵养和养分积累的权衡和协同关系。  方法  基于野外采样和实验分析，应用多元统计方法研究了典型黄土高原小流域土壤水分和养分对不同植被恢复方式的响应。  结果  （1）不同类型人工植被恢复均会引起土壤水分含量降低，尤其是乔、灌植被深层土壤水分消耗较为严重；（2）植被恢复后土壤养分含量总体增加，其中乔、灌植被的土壤有机质、全氮、速效钾积累较草地更显著，然而不同植被类型下的土壤速效磷积累相对较低且无显著差异，并且所有人工恢复植被均引起土壤全磷和有效氮的降低，而土壤有机碳和全氮积累随植被恢复年限呈显著增加趋势。（3）综合考虑土壤水分亏缺和土壤养分积累时，乔、灌植被存在相对高水分亏缺和相对高养分积累的特征，相比而言草地土壤水分和养分的权衡更具可持续性。  结论  考虑到半干旱黄土区土壤水分和养分的权衡，合理的植被配置和对人工乔、灌植被的必要管理应该受到重视。

Trade-off Effects of Soil Moisture and Soil Nutrients under Vegetation Restoration in a Small Watershed on the Loess Plateau,China

  Objective  Identifying the tradeoffs and synergies between soil water conservation and soil nutrient accumulation is one of the key issues in exploring influence of human activities on soil ecosystem services.   Method  Based on field sampling and experimental analysis, multivariate statistical methods were used to study the responses of soil moisture and nutrients to different re-vegetation types in a typical loess watershed.  Result  (1) All introduced vegetation restorations would decrease soil water content, especially the deep soil layers in forests and shrubs. Generally, re-vegetation could increase soil nutrients. (2) The accumulation of soil organic matter (SOC), total nitrogen (N) and available potassium (K) in forestland and shrubland were significantly higher than those in grassland. However, the accumulation of available phosphorus (P) was relatively lower than other soil nutrients and has no significant difference between different vegetation types. In addition, all introduced vegetation could cause decreasing of total P and available N. The accumulations of SOC and total N significantly increased with the years of vegetation growth. (3) The significant correlations between soil moisture deficit and high soil nutrient accumulation were found in forests and shrubs and showed relatively high tradeoff between these two soil ecosystem services. The tradeoff and synergy between soil moisture content and soil nutrient content in grasslands suggested relatively sustainability of soil ecosystem services than other vegetation types.   Conclusion  Considering the tradeoff and synergy between soil moisture and soil nutrient in different vegetation restoration types in semi-arid Loess Plateau, scientific guidance and reasonable land management on introduced vegetation should be considered.