土壤增温降低亚热带森林土壤可溶性有机碳数量和质量

Soil warming decreased dissolved organic carbon quantity and quality in subtropical forests

土壤可溶性有机碳(DOC)是森林土壤碳库中最活跃的部分,其对气候变暖的响应将深刻影响森林生态系统碳循环。本研究基于亚热带常绿阔叶林野外增温实验平台,原位收集土壤溶液,结合紫外可见光谱、红外光谱和三维荧光光谱分析,探究土壤剖面DOC通量及组成对增温(+4℃,1年)的响应。结果表明:土壤DOC通量在土层之间没有显著差异。土壤DOC主要由2个类腐殖酸组分和1个微生物代谢产物组分组成。与对照相比,增温显著降低了土壤DOC通量,降低了土壤溶液芳香化指数和疏水组分比例,增加了小分子碳水化合物的含量。此外,增温还提高了表层土壤(0~10 cm)类腐殖酸组分的相对贡献,增加了深层土壤(30~40 cm)微生物代谢产物组分的相对贡献,这在一定程度上表明变暖加速了深层土壤微生物周转。总体来说,土壤增温降低了亚热带常绿阔叶林土壤DOC数量,使DOC结构趋于简单。

Soil dissolved organic carbon(DOC)is the most active part in forest soil carbon pool,the responses of which to climate warming has profound effects on forest carbon cycling.Based on a manipulative soil warming experiment in subtropical evergreen broad-leaved forests,we collected soil solutions in situ and used ultraviolet-visible,infrared and three-dimensional fluorescence spectroscopy analyses to explore the effects of soil warming(+4℃,1 year)on soil DOC quantity and quality along the soil profile.The results showed that soil DOC flux remained constant along the soil profile.Soil DOC mainly included two humic-like fractions and one microbial metabolite.Warming significantly decreased soil DOC flux and the abundance of aromatic and hydrophobic components,and increased the amount of low molecular weight carbohydrates.Furthermore,soil warming increased the relative proportion of humic-like fractions in the surface soil layer(0-10 cm)and microbial metabolite in the deep soil layer(30-40 cm),indicating that warming might accelerate microbial turnover in the deep layer.Overall,soil warming not only decreased soil DOC content,but also simplified the composition of soil DOC in subtropical evergreen broad-leaved forests.