祁连山东缘高寒草甸灌丛化对植被群落与土壤理化特性的影响

为明晰祁连山东缘高寒草甸灌丛化对其植被群落与土壤理化特性的影响,选取甘肃省天祝藏族自治县高寒草甸灌丛化区域,调查其植被,采集土壤测定理化性质,分析植被与土壤的互馈关系。结果表明:高寒草甸植被的均匀度指数、高度、盖度、地上生物量、土壤含水率随灌丛化过程增加(P<0.05),而多样性指数和容重均降低;全磷含量在各土层以灌丛区最高,但C ∶ P和N ∶ P以草甸区最高;土壤N ∶ P<14表明土壤养分主要受限于氮;土壤脲酶和过氧化氢酶活性在草甸区各土层显著高于灌丛区(P<0.05);冗余分析显示前两个排序轴的累计解释量为54.88%,土壤过氧化氢酶与植被特征拟合的结果最好(Pr=0.010),表明高寒草甸灌丛化过程中土壤过氧化氢酶受植被特征的制约最大。可见,高寒草甸灌丛化显著影响了植被群落结构与土壤理化特性,在祁连山生态保护和管理中应该予以重视。

Effects of shrub encroachment of alpine meadows on vegetation community structure and soil physicochemical properties

Shrub encroachment is an important ecological process that affects the nutrient cycle of alpine meadows. In order to investigate the impact of shrub encroachment on vegetation communities and soil physicochemical properties in alpine meadows along the eastern edge of the Qilian Mountains, this study focused on the shrub encroachment alpine meadow area of Tianzhu Tibetan Autonomous Region in Gansu Province. The study analyzed the characteristics of the vegetation in the meadow area, excessive area under the crown grass, bush in the excessive area, excessive area under the crown grass, bush in the scrub area, as well as the physical properties of the soils at depths of 0-10 cm, 10-20 cm, and 20-30 cm. The study examined the nutrient content, stoichiometric ratios, the activities of urease, alkaline phosphatase, catalase, and sucrase activities. The results showed that the evenness index, height, cover and aboveground biomass of alpine meadow vegetation at the eastern edge of the Qilian Mountains increased significantly with the process of shrub encroachment. However, Simpson''s index, Shannon-Wiener''s index, and abundance index decreased. Soil water content in the 0-10 cm layer was significantly higher in the scrub area than in the meadow area. Additionally, the bulk density in the staggered area was significantly higher than that in the scrub area (P<0.05), and there was no significant change in pH. Soil nitrogen content in the 20-30 cm layer was significantly higher in the meadow area than in the staggered area, but C ∶ P soil total nitrogen content in the 20-30 cm layer was significantly higher in the meadow area than in the scrub area. Furthermore, the total phosphorus content in the 0-30 cm layer was significantly higher in the scrub area than in the meadow area (P<0.05), C ∶ P and N ∶ P were the highest in the meadow area, but the significance of soil organic matter content was not apparent. Soil N ∶ P<14 indicated that nitrogen was the main limiting factor for soil nutrients. The activities of soil urease and catalase were significantly higher in the 0-30 cm layer compared to the scrub area (P<0.05). There was no significant in pH. Soil water content was significantly higher in the 20-30 cm layer compared to the scrub area. Higher than that in the scrub area (P<0.05), there were no significant changes in alkaline phosphatase and sucrase. Axes I and II in the redundancy analysis explained 47.27% and 7.62% of the total variation, respectively, while vegetation characteristics cumulatively explained 54.88% of the variation in soil physical and chemical properties. The best fit between soil catalase and vegetation characteristics (Pr=0.010) indicated that soil catalase was most influenced by vegetation characteristics during the process of alpine meadows scrub fertilization. Soil organic matter, total nitrogen, and total phosphorus content were highly significantly and negatively correlated with vegetation diversity. It can be seen that the shrub encroachment of alpine meadows significantly affects the structure of vegetation communities and soil physicochemical characteristics, and the influence of shrub encroachment should be paid attention to in the ecological protection and management of Qilian Mountains.