氮、磷养分添加对高寒草甸土壤酶活性的影响

本试验以典型的青藏高原高寒矮嵩草草甸(Kobresia humilis meadow)为研究平台,以表征土壤碳、氮、磷、硫养分循环的6种土壤酶为研究对象,研究土壤酶以及土壤速效养分在4年氮、磷养分添加的累积效应下的变化规律,分析和评价氮、磷养分添加对土壤养分循环方面的影响。试验结果为:氮、磷养分添加改变了土壤中速效养分的含量;氮添加与0~10cm土层中的碱性磷酸酶活性有正效应,磷添加抑制了0~10cm土层中的碱性磷酸酶活性;氮、磷养分添加均抑制了0~10cm土层中的脲酶活性;氮添加抑制了2个土层中的纤维素酶活性;芳基硫酸酯酶活性和蔗糖酶活性没有表现出显著差异性;10~20cm土层中的几丁质酶活性在氮、磷养分添加处理下均增强,其中磷添加对几丁质酶活性的增幅最显著。结果表明:外源添加的氮在调控磷的矿化方面有促进作用,磷的添加对氮素的释放也有一定的作用;青藏高原高寒草甸受磷限制的程度可能更大。

The effect of nitrogen and phosphorus applications on soil enzyme activities in Qing-hai-Tibetan alpine meadows

This study investigates the effect of nitrogen and phosphorus applications on soil nutrient cycles,fo-cusing on soil enzyme activities in particular.Enzyme activities and available nutrients have been measured in plots of Qinghai-Tibetan alpine meadow with 4 years of N and P fertilizer application.The study focuses on six soil enzyme activities that represent several significant nutrient cycles (C,N,P,S).The results showed that the contents of available phosphorus and alkaline nitrogen increased under the different treatments.The activities of alkaline phosphatase,urease,chitinase and cellulase vary significantly under the different treat-ments,while there is no significant difference in the activities of arylsulfatase and sucrase.In soils at a depth of 0-10 cm,nitrogen applications have a positive effect and phosphorus applications a negative effect on alkaline phosphatase activity.Urease activity is repressed in 0-10 cm soils under both nitrogen and phosphorus treat-ments.In soils at a depth of 10-20 cm,chitinase activity is significantly promoted by nitrogen and phosphorus applications,and especially by phosphorus.Cellulase activity at both soil depths is repressed by nitrogen treat-ment.The results indicate that nitrogen supply effects the mineralization of P and that phosphorus supply canpromote the decrease of N.The relative degree of phosphorus limitation may be higher than nitrogen limitation in Qinghai-Tibetan alpine meadows.