以中亚热带杉木(Cunninghamia lanceolata)幼苗为研究对象,设置埋设电缆以加热土壤增温(+5℃)结合模拟氮沉降的实验,施氮水平分别为对照(CT,0 kg hm~(-2) a~(-1)) 、施低氮(LN, 40 kg hm~(-2) a~(-1))和施高氮(HN, 80 kg hm~(-2) a~(-1)),用离子交换树脂袋法研究了土壤有效氮对模拟增温和施氮的短期响应。经过为期1a的研究,结果表明:土壤有效氮主要集中在夏冬季,而且硝态氮是土壤有效氮的主要存在形态;增温显著增加土壤有效氮含量(P<0.05),各月间的有效氮含量与气温和降雨量有关;总体来看,氮沉降显著增加土壤有效氮含量(P<0.05),而且随氮沉降水平的升高而增加。低氮处理下,大多数月份的土壤有效氮含量显著增加,高氮处理下,各月的有效氮含量均显著高于对照处理;增温*氮沉降在各月间均显著增加土壤有效氮含量(P<0.05),并随氮沉降水平的升高而增加。而且,两者的交互作用对有效氮的增幅显著大于任一单一因子的作用。说明增温和氮沉降两者的交互作用对土壤有效氮的影响具有叠加效应。因此,增温和氮沉降及其交互作用短期内都会显著增加土壤有效氮含量,为植物生长提供充足的养分。
英文摘要:
Soil available nitrogen is a small but crucial component in the nitrogen pool,as productivity in ecosystems is closely linked to nitrogen availability. Since the world' s first Industrial Revolution,global warming has increased and nitrogen deposition has increased; therefore,there is a strong focus on soil available nitrogen. To study the short-term response of soil available nitrogen to climate change (warming,nitrogen deposition),we conducted an experiment in four micro-plots planted with young Cunninghamia lanceolata in a mid-subtropical region,which was subjected to experimentally increased soil temperature (W,+ 5℃) and inorganic nitrogen concentration in artificial precipitation (control [CT],0 kg hm~(-2) a~(-1); low nitrogen addition [LN],40 kg hm~(-2) a~(-1); and high nitrogen addition [HN],80 kg hm~(-2) a~(-1)) by using NH_4 NO_3. Soil available nitrogen was measured monthly by using ion exchange resin bags. After one year,the results showed that soil available nitrogen concentrated primarily in the summer and winter,and nitrate nitrogen was the main form of available nitrogen. Increasing the soil temperature significantly increased the soil available nitrogen content (P < 0.05). In addition, the soil available nitrogen content was related to monthly air temperature and rainfall. Overall,nitrogen deposition significantly increased the soil available nitrogen content (P < 0.05). Under low nitrogen treatment,soil available nitrogen content increased significantly in most months; under high nitrogen,soil available nitrogen was significantly higher every month than that in the control treatment. With the combined treatment of increased soil temperature and nitrogen deposition, the soil available nitrogen content increased significantly each month,more than that by either increased temperature or nitrogen deposition alone. This indicated that increased soil temperatures and nitrogen deposition had a combined effect on soil available nitrogen content. Therefore,increased temperature and nitrogen deposition,individually or combined, increased soil available nitrogen content considerably,and thus could provide plants with sufficient nitrogen for productive growth.