温带森林土壤溶液溶解性N2O和CO2含量特征及其影响机制

利用陶瓷头土壤溶液收集器采集2006年7月～2007年8月问长白山阔叶红松天然林不同深度(15cm和60 cm)土壤溶液,探讨应用气液萃取平衡-气相色谱法测定森林土壤溶液中溶解性气体N_2O和CO_2浓度的可行性,并利用此方法研究林地不同深度土壤溶液中两种气体含量特征及其影响机理.研究结果显示观测期内林地15 cm和60 cm深度土壤溶液中溶解性CO_2浓度的变化范围分别为5.26～10.71μg·mL~(-1)(C)和3.13～6.16 μg·mL~(-1)(C),溶解性N_2O浓度的变化范围分别为2.44～13.40 ng·mL~(-1)(N)和3.23～27.98 ng·mL~(-1)(N).阔叶红松天然林土壤溶液中溶解性CO_2和N_2O浓度均呈现出明显的季节性变化.春融后的降水促进了土壤溶液中溶解性N_2O产生,尤其在60 cm深度.与60 cm深度相比,林地15 cm深度溶液中溶解性CO_2浓度的季节性变化更明显,尤其在植物生长旺季.逐步回归分析显示,水溶性有机碳含量可以解释林地不同深度溶液中溶解性CO_2浓度变化的29%;水溶性有机氮含量可以解释林地60 cm深度溶解性N_2O浓度变化的34%.因此,水溶性有机碳和有机氮分别是长白山阔叶红松林土壤溶液溶解性CO_2和N_2O形成的重要因子.同时研究结果表明本文实验方法对于测定林地不同深度土壤溶液中溶解性N_2O和CO_2含量均有较好的适用性,连续三次萃取后所获得的气体浓度可有效反映溶液中的实际气体浓度.

Dissolved N2O and CO2 Concentrations in Soil Solution under Temperate Old-Growth Forest and Their Associated Mechanisms

Soil solutions at 15 cm and 60 cm depths under a Korean pine and broadleaf mixed natural forest stand at Changbai mountain, Northeast China, were sampled using porous ceramic suction cups during the period from July 2006 to August 2007, to study the dynamics of dissolved N_2 and CO_2 concentrations in solution and their key associated driving mechanisms.A combination of multiple phase equilibration procedure and gas chromatography was used for measurement of dissolved N_2O and CO_2 concentrations of solution During the period of sampling, the concentrations of dissolved CO_2 in soil solution at 15 cm and 60 cm depths ranged from 5.26 to 10.71 μg · mL~(-1) (C) and from 3.13 to 6.16 μg · mL~(-1) (C),respectively, and the dissolved N_2O concentrations at both depths ranged from 2.44 to 13.40 ng · mL~(-1) (N) and from 3.23 to 27.98 ng · mL~(-1) (N),respectively. The seasonal change in concentrations of dissolved CO_2 and N_2O in soil solution under such forest stand was significant, with differences at both depths (pass 0.05 significance level). The results suggest that rainfall after thawing in late spring can promote the accumulation of dissolved N_2O in forest soil solution at 15 cm and 60 cm depths, particularly at 60 cm depth.Seasonal changes in dissolved CO_2 concentrations of soil solution were more pronounced at 15 cm depth than those at 60 cm depth. Stepwise regression analysis showed that 29% of the variance in dissolved CO_2 concentrations of solution at both depths was accounted for by the concentrations of water soluble organic C, and 34% of the variance in dissolved N_2O concentrations at 60 cm depth by the concentrations of water soluble organic N. Hence, both water soluble organic C and organic N can contribute to the formation of dissolved CO_2 and N_2O in soil solution under such forest stand, respectively.The results also suggest that actual concentrations of both dissolved gases in soil solution could be obtained by the continual three phase equilibration method.