放牧强度对高寒嵩草草甸土壤养分特性的影响

植物-土壤系统是草地生态和生产服务价值实现的基础,放牧是草地植物群落演替的重要因素。植物、土壤亚系统对放牧的敏感性是评价草地稳定性和提高草地恢复力的重要依据。以不同放牧强度下的高寒嵩草(Kobresia)草甸为研究对象,探讨土壤养分特征对放牧强度的响应及作用位点,结果表明:改变放牧强度可以明显改变植物群落数量特征,但没有明显改变土壤层次分类特征,说明土壤养分特征对一定范围内放牧强度具有自我稳定维持功能;但放牧干扰强度不同时,土壤剖面过渡层养分含量存在差异,说明长期放牧强度的差异会对土壤剖面养分性质产生影响,且这种影响起源于土壤剖面过渡层。在放牧高寒嵩草草甸植物-土壤系统中土壤剖面养分特征较植物群落数量特征更稳定;土壤剖面过渡层养分特征是土壤亚系统中对放牧的敏感因素;而放牧引起土壤剖面养分特征的改变主要表现在各过渡层上,并构成土壤发生层迁移的风险,因此推测,更为持久和更高强度的放牧干扰将最终改变土壤剖面特征及养分性质。

Responses of soil nutrient traits to grazing intensities in alpine Kobresia meadows

Soil-Plant system is the base of eco-economic production in grassland system. Livestock grazing is the most important disturbance factor in plant community succession in Qinghai -Tibet plateau. Soil traits will become considerable indices when the plant community characteristics are different by livestock grazing. There are some relationships between soil and plant community traits, in vegetation cover, vegetation diversity, soil development, soil erosion, soil degradation, and geomorphological and hydrological behaviour of alpine meadow system. The health of plant-soil system is the focus issue in natural eco-system, and plant and soil properties can reflect the healthy of the ecosystem. So in the alpine meadow system which factor is more sensitive in grazing disturbing, soil nutrient characters or plant community characters. In our studies, we first investigated 4 plots in Haibei states, Qinghai province, China, which had the same geographical unit and climatic region but in different livestock grazing intensities. We inquired details information about stocking rates, grazing time and livestock species in these plots. In the same time, soil samples were collected to the laboratory to analyze characters of soil nutrient contents (containing organism, total nitrogen, total phosphorous, total potassium, slowly release potassium, ammonium nitrogen, nitrate nitrogen, available phosphorous, available potassium, pH value, and inorganic carbon). The results showed that: the soil parent materials were in the same style in different livestock grazing intensities, it illustrated that those plots had the same pedogenic basis. The discrimination of plant community characters were come from environmental disturbing intensities, like livestock grazing. Plant community characters were differences, but soil layers'' nutrient characters were consistent in the same soil layer under the different grazing intensities. In soil system, characters of soil profile transition layers were more sensitive to grazing disturbing, for example 5-10cm was a transition layer of mattic epipedon and leached layer, mattic epipedon would grow thickly when the livestock grazing intensity increasing to a certain extent, as a result, the plant community succession changed the root distribution length and density, and affected nutrient under the mattic epipedon soil layer (the leached soil layer), so 5-10cm had some transition characters between mattic epipedon and leached soil layer, it became the soil profile transition layers, those layers would more sensitive on livestock grazing intensities. It was inconformity between plant community characteristics and soil nutrient traits under different livestock pressure. Soil nutrient system were more stable than plant community system in different livestock intensities, meanwhile the different livestock intensities would not change soil profile nutrient classification, but it would more or less change the soil nutrients content in soil transition layer, and roots distributed condition could effect the soil nutrients by soil rhizosphere microbe, root exudates and so on. So in the soil-plant system, soil sub-system was more steady than plant community sub-system. In soil sub-system, soil transition layers were more sensitive than soil profile characters in livestock intensities. So plant community characters and the soil transition layers may become the discrimination index in livestock intensities in alpine meadows.