氮沉降对湿地松林土壤呼吸的影响

Effects of Nitrogen Deposition on Soil Respiration of Pinus elliottii

为了阐明湿地松林土壤呼吸对氮沉降响应的变化规律以及氮沉降是否改变土壤呼吸温度敏感性系数,运用LI-8100开路式土壤碳通量测量系统测定模拟氮沉降4种不同处理水平[0、5、15、30g/（m2·a）]下湿地松林（Pinuselliottii）的土壤呼吸速率及土壤温、湿度。结果表明：湿地松林土壤胡须呈明显季节变化,7月最高,1月最低。各处理土壤呼吸年累积量为：对照（CK）[（5.28±1.02）t/（hm2·a）]、低氮[LN（4.51±0.64）t/（hm2·a）]、中氮[LN（4.66±0.51）t/（hm2·a）]和高氮[HN（4.20±0.43）t/（hm2·a）]。全年对照处理土壤呼吸速率平均值为CK[（1.44±0.28）μmol/（m2·s）]比各氮沉降处理LN[（1.20±0.17）μmol/（m2·s）]、MN[（1.24±0.13）μmol/（m2·s）]、HN[（1.11±0.11）μmol/（m2·s）]高16.6%、13.8%、22.9%。土壤呼吸速率与10cm土壤温度呈显著相关正指数关系（P〈0.01）,相关性指数（R2）在0.6049~0.7557之间,湿地松林在各处理氮沉降下温度敏感性系数分别为LN（1.72）、MN（1.75）、HN（1.79）同对照（2.35）相比有降低趋势。土壤呼吸与5cm土壤湿度之间呈二次方程关系,但相关性不显著（P〉0.05）。研究表明,氮沉降是影响湿地松林CO2通量的一个重要因子。

In order to determine the effect of increased nitrogen deposition on total soil respiration of Pinus elliottii forest, and whether increased nitrogen deposition alters the temperature sensitivity of soil respiration, the author used LI-8100 to investigate the response of soil respiration of Pinus elliottii for increased nitrogen deposition, a field experiment with 4 simulated nitrogen deposition levels [0, 5, 15, 30 g N/（m 2 ·a）]. The soil temperature at 10 cm depth and soil moisture at 5 cm depth were recorded at the same time. Results showed that： soil respiration rate had an obvious seasonal change, with the maximum in July and the minimum in January. the annual cumulative soil respiration was [CK （5.28±1.02） t/（hm 2 ·a）] and [LN （4.51±0.64） t/（hm 2 ·a）] and [LN （4.66±0.51） t/（hm 2 ·a）] and [HN （4.20±0.43） t/（hm 2 ·a）]. On average, the mean rate of soil respiration was LN [（1.20±0.17） μmol/（m 2 ·s）] and MN [（1.24±0.13） μmol/（m 2 ·s）] and HN [（1.11±0.11） μmol/（m 2 ·s）], and reduced 16.6%, 13.8% and 22.9% respectively comparing with control level [（1.44±0.28） μmol/（m 2 ·s）]. The relationship between soil respiration and soil temperature at 10 cm of Pinus elliottii was significant （P〈0.01）（R 2 =0.6049-0.7557 ） The Q 10 values at 4 different nitrogen treatment levels of Pinus elliottii were LN （1.72） and MN （1.75） and HN （1.79）. Compared with which at control level, the Q 10 values of Pinus elliottii soil respiration tended to decrease with nitrogen deposition. The relationship between soil respiration and soil moistures at 5 cm depth also were not significant. The results indicated that nitrogen deposition was an important factor in affecting soil CO 2 efflux of Pinus elliottii.