甘南高寒草甸退化过程中土壤理化性质和微生物数量动态变化

研究甘南高寒草甸退化草地土壤理化性质和微生物数量动态变化特征,为退化草地改良修复提供理论依据。于2017年5,7,10月分别采集极度(ED)、中度(MD)和轻度(LD)退化草地,以及未退化的对照草地(CK)土壤,测定其理化特性及微生物数量特征。结果表明:CK的土壤含水量在5,7月均显著小于LD、MD和ED的土壤含水量,而在10月显著大于LD、MD和ED的土壤含水量;随着退化程度的加剧,土壤pH逐渐增大,有机碳、全氮和全磷含量逐渐减小;土壤细菌数量对草地的退化反映更敏感,放线菌次之,真菌最小;CK和LD的土壤微生物数量随土层深度下降更为明显;冗余分析结合蒙特卡罗置换检验结果发现,各月份影响微生物数量的环境因子不同,显著影响5月微生物数量的是土壤全磷和土壤含水量,而7月除土壤pH外,其余指标均有显著影响,10月除土壤pH和土壤碳氮比外,植被盖度和生物量等均有显著影响。可见,甘南高寒草甸土壤理化特征和三大微生物数量对退化程度的响应具有季节差异,不同时期影响因素和权重需在草地管理中予以重视。

Dynamic Characteristics of Soil Physicochemical Properties and Microbial Quantity During the Degradation of Gannan Alpine Meadow

The aim of the current study was to examine the dynamic changes of soil physicochemical properties and microbial quantities, and to provide theoretical basis for the improvement and restoration of the degraded grassland in Gannan alpine meadow. The soil samples were collected from light degradation (LD), moderate degradation (MD), extreme degradation (ED) and control grassland (CK) in May, July and October, 2017, to investigate the physiochemical characteristics and the microbial quantities. The results showed that the soil water content of CK was significantly lower than that of the degraded grassland in May and July, while significantly higher than that of the degraded grassland in October. With the aggravation of degradation degree, soil pH value gradually increased, while the content of organic carbon, total nitrogen and total phosphorus gradually decreased. The number of soil bacteria was more sensitive to grassland degradation, followed by actinomycetes and fungi. The soil microbial quantities of CK and LD decreased more obviously with the increasing of soil layer depth. Redundancy analysis and the Monte Carlo permutation test showed that the environmental factors affecting soil microbial quantities were different in each month. Soil microbial quantities were significantly affected by total phosphorus and soil water content in May, while other factors except soil pH had significant effects in July. Except soil pH value and C/N, vegetation coverage, aboveground and underground biomass and other environmental factors had significant effects in October. All of the above results revealed that the responses of soil physicochemical characteristics and soil microbial quantities to grassland degradation had have seasonal variation in Gannan alpine meadow, the influencing factors and weights in different periods also needed to be paid attention to in grassland management.