模拟氮沉降对樟树人工林土壤呼吸的短期效应

Short-term effects of nitrogen deposition on soil respiration of Cinnamomum camphora plantation

通过对中亚热带地带性植被樟树林进行模拟氮沉降试验,氮沉降水平分别为对照(CK,0 g.m-2a-1)、低氮(LN,5 g.m-2a-1)、中氮(MN,15 g.m-2a-1)和高氮(HN,30 g.m-2a-1),利用LI-8100土壤呼吸测定系统,研究了模拟氮沉降对其土壤呼吸速率的影响以及与土壤表层温湿度的响应。结果表明,不同浓度氮沉降处理水平下的土壤呼吸速率平均值分别为CK 4.09±0.66μmol.m-2s-1、LN 2.39±0.29μmol.m-2s-1、MN 2.18±0.19μmol.m-2s-1、HN 2.28±0.25μmol.m-2s-1。对照处理显著高于其它3种处理(P<0.01);土壤呼吸温度敏感系数Q10值分别为CK1.80、LN 1.67、MN 1.77、HN 1.53,各处理土壤呼吸速率与土壤地表温度呈显著正相关关系;5 cm土壤体积含水率在0.266 6～0.294 4(m3.m-3)之间,各月份土壤体积含水率差异不大(1.8%～9.4%),土壤呼吸速率与5 cm土层土壤体积含水率相关性不显著(P>0.05),模拟氮沉降初期明显抑制了樟树人工林土壤呼吸。

The nitrogen deposition experiments on Cinnamomum camphora plantation of Hunan provincial botanical garden were simulated from June the 7th to October the 7th 2010,the nitrogen deposition levels was respectively as control（CK,0 g·m^-2a^-1）,low nitrogen（LN,5 g·m^-2a^-1）,medium nitrogen（MN,15 g·m^-2a^-1） and high nitrogen（HN,30 g·m^-2a^-1）.The soil respiration speed and soil surface temperature and the surface water content of the soil were determined by LI-8100 measuring instrument.The results show that the average values of soil respiration speed were CK（4.09±0.66 μmol·m-2 s-1）,LN（2.39±0.29 μmol·m-2 s-1）,MN（2.18±0.19 μmol·m-2 s-1）,HN（2.28±0.25 μmol·m-2 s-1）,that of the CK was obviously higher than the other three treatments（P〈0.01）.With different nitrogen concentrations deposition treatments,the Q10（temperature sensitivity coefficients） for soil respiration of CK,LN,MN and HN treatments were 1.84,1.71,1.83 and 1.56.It was positive correlation between the respiration speed and the surface（≤10 cm） temperature of tested soil.It was negative correlation between the respiration speed and the surface（≤5 cm） water content of tested soil（P〈0.05）.Volumetric water content of 5 cm soil was between 0.266 6～0.294 4（m^3·m^-3）,it did not vary much monthly during the research period（1.8%～9.4%）.The findings suggest that the initial stage of nitrogen deposition obviously influenced the soil respiration of Cinnamomum camphora plantation.