不同环境条件下土壤微生物对模拟大气氮沉降的响应

研究了林内及林缘两个生境中,在有苔藓覆盖和无苔藓覆盖条件下,人工加氮对土壤理化性质及土壤微生物群落的影响。结果显示加氮使土壤pH下降,有效态氮和有效态磷的含量上升,但不同生境及有无苔藓植物覆盖在一定程度上影响土壤理化性质及其对加氮的反应。苔藓植物覆盖可以缓解加氮引起的土壤酸化及有效氮含量上升压力,促进有效态磷含量上升。不同生境中,土壤微生物对氮沉降的响应亦不同。低氮使林缘生境土壤微生物的胁迫程度减小,中高氮使其胁迫程度上升,而任何加氮均增加林内生境中土壤微生物的胁迫程度。两个生境中,苔藓植物覆盖均可以缓解过量氮沉降对土壤微生物造成的压力,降低过量氮沉降对土壤微生物的伤害,提高土壤微生物的代谢活性。

Responses of soil microbial communities to moss cover and nitrogen addition

Soil microclimate and chemical/physical properties are among the key regulatory variables determining microbial activities in forest soils. We manipulated moss cover (i.e., modifications of soil microclimate) and added nitrogen in an interior forest and an area of edge influence (AEI) to examine how changes in microclimate and N addition may alter the soil microbes. With N addition, we found decreased pH and elevated N and P, although moss removals and ecotope complicated the changes of soil properties and their responses to N treatment. Overall, moss cover alleviated the stress of soil acidification, decreased available N, and stimulated the available P at N addition conditions. The above changes produced significant influences on soil microbial communities. The low N addition lowered the environmental stress of soil microorganisms at the AEI, while the intermediate and high level of N additions increased environmental stresses. Any N addition increased the environmental stress of soil microorganisms at the interior forest. The moss cover treatment decreased the environmental stresses on soil microorganisms and, consequently, enhanced the soil microbial metabolic activities.