草甸湿地土壤溶解有机碳淋溶动态及其影响因素

采用土柱淋溶试验研究了草甸湿地有机土层（2～13 cm）DOC的淋溶动态，并探讨了土壤呼吸、NH₄⁺产生速率和淋溶液pH与DOC生成速率的关系.试验第一周，小叶章湿草甸（Ⅺ）和小叶章沼泽化草甸（Ⅻ）土壤DOC的释放速率经历了一个快速下降的过程，而后达到平稳水平，其DOC的释放动态可用一次指数衰减方程进行描述（R²>0.96,P<0.05）.整个试验期间（35 d），两种草甸湿地土壤DOC的累积释放量分别为2109（Ⅺ）和506.58 μgC·g^-1（Ⅻ），CO₂的累积释放量为679.64（Ⅺ）和455.54 μgC·g^-1（Ⅻ），表明Ⅺ的低DOC释放可能与高CO₂释放所造成的微生物碳源受限有关.DOC的释放速率与NH₄⁺的生成速率呈显著正相关（r_Ⅺ=0.886,P<0.05;r_Ⅻ=0.972,P<0.01），而与淋溶液pH无相关性.多元回归分析表明，草甸湿地DOC的生成主要受土壤氮矿化潜势制约（P<0.05）.

Dynamics of dissolved organic carbon (DOC) leaching in meadow marsh soil and related affecting factors

In this paper, an incubation test with soil columns was carried out for 35 days to study the dynamics of DOC leaching from the organic layers (2 approximately 13 cm) of two meadow marsh soils, and the correlation of DOC release with soil respiration, NH4+ formation, and leachate pH. The results showed that in the first week, DOC release presented a fast decrease, and then held on a steady level, which could be well described by one order exponential equation (R2 > 0.96, P < 0.05). During 35 days incubation, the cumulative release of DOC from two test soils was 210.9 microg C x g(-1) and 506.58 microg C x g(-1), and the cumulative emission of CO2 was 679.64 microg C x g(-1) and 455.54 microg C x g(-1), respectively. It was suggested that in the course of incubation, the lower DOC release might be related to the microbial carbon limitation because of the greater CO2 production rate. A significantly positive correlation was found between DOC release and NH4+ formation (rXI = 0.886, P<0.05; rXII = 0.972, P<0.01), while no significant correlation was observed between DOC release and leachate pH. Multiple regression analysis showed that the nitrogen mineralization potential of meadow marsh soil was the main factor affecting DOC production.