摘要:春季降雨是内蒙古典型草原生产力最重要的影响因素之一，土壤湿度与微生物活性密切相关，但春季降雨对土壤微生物量磷周转的影响目前知之甚少。本研究2015年4月底在内蒙古锡林浩特毛登牧场，设立不降雨（W0）、一次模拟降雨20 mm（W1）和两次模拟降雨，每次20 mm（W2）试验，旨在比较不同模拟降雨量条件下，典型草原土壤微生物量磷季节变化特征，了解土壤微生物量磷周转特征及其与植物磷素营养的关系。结果表明：（1）模拟春季降雨显著地提高了土壤微生物量磷，W1和W2分别从W0的6.91 μg/g提高到7.47 μg/g和8.29 μg/g（全年平均值），尤其是模拟2次降雨，土壤微生物量磷周转期缩短至0.53年，周转通量增大至33.16 kg hm^-2 a^-1，而W0分别为0.59年和26.82 kg hm^-2 a^-1；（2）模拟春季降雨总体上降低了土壤酸性磷酸酶活性，但提高了碱性磷酸酶活性；（3）模拟降雨显著地提高了植物生物量和全磷含量，但是植物生物量和全磷含量与土壤微生物量磷、酸性和碱性磷酸酶活性及土壤有效磷含量之间没有显著的相关性。这可能反映出内蒙古典型草原土壤微生物量磷周转、土壤磷素供给及牧草磷素营养之间存在复杂的关系；土壤微生物与牧草竞争土壤磷素，从而影响牧草磷素营养。



Abstract:Precipitation during spring season greatly influences the productivity of typical steppe in Inner Mongolia. However, little is known whether spring rainfall affects the turnover of soil microbial biomass phosphorus. In this study, a simulated spring rainfall experiment with three treatments of none rainfall (W0), a simulated rainfall of 20 mm (W1) and twice simulated rainfalls of 40 mm (W2) was conducted in April 2015 at Maodeng farm Xilinhot Inner Mongolia. The aim was to compare the characteristics of seasonal changes in soil microbial biomass phosphorus, and understand the impact of the simulated rainfall on soil microbial phosphorus turnover and its relationship with plant P nutrition. The results showed that: (1) the simulated spring rainfall significantly increased soil microbial biomass phosphorus (SMB_P). The annual average values of SMB_P increased from 6.91 μg/g at W0 to 7.47 μg/g at W1 and 8.29 μg/g at W2, respectively. In particular, the turnover time of SMB_Pin W2 was shortened to 0.53 year. The turnover flux enhanced to 33.16 kg hm^-2 a^-1, while W0 was 0.59 year and 26.82 kg hm^-2 a^-1 respectively. (2) The simulated spring rainfall generally induced a reduction in soil acid phosphatase activity, but an increase in alkaline phosphatase activity. (3) The simulated spring rainfall resulted in obvious increases of both plants above-ground biomass and total phosphorus content. However, weak correlations were obtained among the plant above-ground biomass or total phosphorus content with soil microbial biomass phosphorus, acid /alkaline phosphatase activity, and soil available phosphorus content as expected.Our results might imply that there was a complex relationship among soil microbial biomass phosphorus, soil available phosphorus, and plant phosphorus nutrient in typical steppe of Inner Mongolia. Soil microbial biomass could compete with grass on soil phosphorus and thereafter influence plant P nutrition.





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