碳添加下黑钙土胞内、胞外脲酶活性变化及其机制

Responses of soil intracellular and extracellular urease activities to carbon additions in cher-nozem

土壤脲酶作为能够催化尿素水解的最重要酶类,对草地生态系统氮素供应具有重要作用。目前探讨不同碳添加对草地土壤胞外脲酶影响的研究报道相对较多,但碳添加对土壤胞内脲酶的影响,以及胞内和胞外脲酶对碳添加的响应是否一致等尚需深入研究。本研究依托额尔古纳森林草原过渡带生态系统研究站开展的碳添加野外试验平台(以葡萄糖为碳源),选取无碳添加(C0)、250(C250)和500(C500)kg C·hm^-2·a^-1处理为供试对象,探讨碳添加下黑钙土胞内、胞外脲酶活性响应及其与土壤性质的关系。结果表明:碳添加显著提高了土壤胞内脲酶活性,增加了土壤胞内脲酶活性占总脲酶活性的比例,但对土壤胞外脲酶活性没有显著影响。土壤胞内脲酶活性与微生物生物量具有显著正相关关系,表明胞内脲酶活性增加主要是由微生物生物量增加引起的。结构方程模型(SEM)分析表明,碳添加通过影响土壤微生物生物量间接提高了土壤胞内脲酶活性。

Urease in soil,as the most important enzyme catalyzing urea hydrolysis,plays an important role in nitrogen supply of grassland ecosystems.While the effects of different carbon additions on extracellular urease in grassland soil are well understood,their effects on soil intracellular urease remain unknow.Moreover,whether the responses of intracellular and extracellular urease to carbon additions are consistent need to be clarified.With a field experiment in Hulun Buir grassland of Inner Mongolia,we investigated soil intracellular and extracellular urease activities in chernozem under four treatments,including carbon-free(C0),250(C250),and 500(C500)kg C·hm-2·a-1,using glucose as carbon source.Further,we analyzed their relationships with soil properties.Carbon additions significantly increased soil intracellular urease activity and its ratio to total urease activities and total urease activity,but did not affect soil extracellular urease activities.There was significant positive correlation between soil intracellular urease activity and microbial biomass,suggesting that the increases of soil intracellular urease activities were mainly caused by the increases of microbial biomass.Results of structural equation modeling(SEM)analysis showed that carbon additions indirectly increased soil intracellular urease activities by affecting microbial biomass.