祁连山东段不同类型灌丛斑块土壤特征对围封的响应

土壤作为高寒带植被的立地条件,是高寒灌丛生态系统发挥其生态功能的重要基础之一。本研究选取祁连山东段头花杜鹃、山生柳和金露梅3种典型灌丛斑块土壤作为研究对象,系统分析围封前后其理化性质分布特征。结果表明:土壤含水量、有机碳、全磷、全钾、速效氮5个理化指标在灌下、灌外差异显著;土壤含水量、容重、有机碳、全磷、速效氮、速效磷6个理化指标在围栏内外差异显著。主成分分析进一步表明,围栏内速效氮与孔隙度的贡献率较高,表明围封后速效氮与孔隙度是影响祁连山东段3种灌丛斑块土壤理化性质的重要环境因子;围栏外速效氮与全磷的贡献率较高,表明有放牧干扰时速效氮与全磷是影响祁连山东段3种灌丛斑块土壤理化性质的重要环境因子。头花杜鹃灌丛斑块不论是否受到放牧干扰,均能保持其良好的土壤理化性质,表明头花杜鹃灌丛斑块抗外界干扰能力较强。短期围封能够显著增加灌丛斑块土壤含水量和速效养分含量,从而改善立地条件,也进一步证明围封更加有利于退化灌丛草地的恢复与重建。

Response of soil characteristics of different types of shrub patches to enclosure on eastern Qilian Mountain

Soil is one of the basic functional components of the alpine shrub ecosystem. This study aimed to provide scientific guidance for the restoration of the degraded alpine shrub ecosystem. A typical area of the alpine shrub ecosystem on eastern Qilian Mountain with and without enclosures was selected as the sampling site. We selected three typical shrubs (Rhododendron capitatum, Salix oritrepha, Potentilla fruticosa) for detailed analyses of their soil properties. We measured 10 soil physico-chemical properties: total nitrogen (TN), total phosphorus (TP), total potassium (TK), available nitrogen (AN), available phosphorus (AP), available potassium (AK), soil organic carbon (SOC), soil moisture (SM), bulk density (BD), and soil porosity (SP). We analyzed the relationships among soil physico-chemical properties of different distributed community types using various field and experimental methods and statistical analyses including one-way ANOVA, the Tukey-Kramer HSD test, and principal component analysis (PCA) across inside and outside enclosures. We also compared soils from under shrubs and outside the shrub canopy in this ecosystem. It was found that SM, SOC, TP, TK, and AN differed significantly between samples collected under shrubs and outside the shrub canopy, and SM, BD, SOC, TP, AN, and AP differed significantly between inside and outside enclosures. The PCA indicated that AN and SP contributed more to vegetation distribution than did other environmental factors in the fenced plots, and were important predictors of the distribution of different shrubs and plants inside fenced areas on eastern Qilian Mountain. The PCA also indicated that AN and TK contributed more than did the other environmental factors in the grazed plots, and were important predictors of the distribution of different shrubs and plants in grazed grassland on eastern Qilian Mountain. R. capitatum patches always had better soil physical and chemical properties, indicating that this plant has a strong anti-interference ability. The results of these analyses show that short-term enclosure can significantly increase the SM content and available nutrient content in soil in shrub patches, further confirming that fencing is the best way to restore degraded alpine shrub ecosystem.