温度和水分对科尔沁沙质草地土壤氮矿化的影响

土壤氮矿化对陆地生态系统初级生产力起决定性作用,但其影响因素较多,其中温度和水分最为重要。研究沙质草地土壤氮矿化对温度和水分的响应,对预测全球变化对沙质草地生态系统结构和功能的影响具有重要作用。因此,通过开顶式气室(OTC)模拟增温和人工调控田间持水量的方法对科尔沁沙质草地的土壤进行原位培养,分析温度和水分对土壤氮矿化作用的影响。结果表明:无论温度如何变化,科尔沁沙质草地土壤氮净矿化/硝化速率随着田间持水量的增加而明显提高。净硝化速率和净矿化速率在田间持水量为9.5%时最大,田间持水量达到时12.5%明显下降。增温使沙质草地土壤氮矿化显著变化,但增温的效应与田间持水量存在一定的关联。在相对适宜的田间持水量条件下(田间持水量为6.5%~12.5%),OTC增温可以使科尔沁沙质草地的土壤氮矿化/硝化速率显著提高;但是在田间持水量处于相对较低或者过高的状态下,该地区土壤的净氮净矿化/硝化速率对温度增加的响应不明显。

Links of Temperature and Moisture with Soil Nitrogen Mineralization in the Horqin Sandy Grassland

The soil nitrogen mineralization is crucial to the primary productivity of terrestrial ecosystem, but it is affected by many factors, among which temperature and moisture are most important. The research of response of sandy grassland soil nitrogen mineralization to the temperature and moisture plays an important role to predict impact of global change on sandy grassland ecosystem structure and function. Therefore, in this paper, we did the in situ cultivation of sandy grassland soil in Horqin through the method of Open Top Chamber (Open Top Chamber, OTC) simulation of raising temperature and artificial regulation of field moisture capacity, then we analyzed the influence of temperature and moisture on soil nitrogen mineralization. Our results showed that no matter how the temperature changed, the sandy grassland soil net mineralization/nitrification rate increased significantly with the increase of field capacity. The net nitrification rates and net mineralization rates of soil N reached their maximums at the moisture of 9.5% and significantly decreased at the moisture of 12.5%. Raising temperature can make significant changes in sandy grassland soil nitrogen mineralization, but there were some correlations between the effect of raising temperature and the field moisture capacity. Net nitrification rates and net mineralization rates of soil N were significantly accelerated by simulation of raising temperature by OTC under the condition of relatively suitable for field capacity(between 6.5% and 12.5%). However, there were no significant response of net nitrification rates and net mineralization rates of soil N to the increase of temperature under the relatively low or too high condition of field moisture capacity. This implies that effect of raising temperature on soil N mineralization is significant only at the appropriate moisture conditions in the Horqin Sandy Grassland.