摘要

土壤对氮添加的响应:来自天然草地的证据

作者(年代):卡门Postolache博士

在上个世纪，人为活性氮流量超过了自然周转率，显著改变了其生物地球化学循环。我们的研究重点是Neajlov流域(罗马尼亚LTSER遗址)天然草地土壤对氮添加的响应。我们使用2 m2的地块进行NH4NO3施肥，模拟夏季施肥时生物有效氮投入增加0、5和10 kg/ha/年。表层土壤样品每月收集一次，并进行三次分析。在每个重复中，我们测量了pH值、土壤水分和有机质含量，以及硝酸还原酶和脲酶的酶解速率。氯化钾萃取后用分光光度法测定无机氮。在低氧条件下，通过铵的形成对土壤微生物群落的矿化潜力进行了评价。研究表明，有轻微的酸化，更明显的最高氮添加量。硝态氮和铵态氮都有一定的积累，特别是在施肥期。正如预期的那样，酶促速率显示出季节性变化，但我们发现随着生物可利用氮的增加，酶促速率降低。 We observed strong correlations between soil extracellular enzymes and substrates, which were clearer when warm and cold season were analyzed separately. Urease activity positively correlates with organic matter, R2 values of 0.31 (warm season) and 0.41 (cold season), whereas R2 for nitrate reductase and N-NO3- were 0.49 and 0.47 respectively. Our findings suggest that more subtle responses of nitrogen surplus are found at soil microbial community level and that a natural ecosystem is more able to absorb this type of pressure.