氮添加下城市森林土壤呼吸动态变化及其影响因素

城市森林是生态系统重要碳库,其土壤呼吸是构成陆地土壤碳循环的重要环节。为了研究全球氮沉降增加背景下城市森林土壤呼吸动态变化及影响因素,本研究选取安徽省合肥市蜀山森林公园典型城市森林为研究对象,通过添加0(CK)、50(LN)、100(HN) kg N·m^-2·a^-1硝酸铵试验,对其土壤呼吸速率、温湿度及理化性质进行动态观测。结果表明: 城市森林土壤呼吸具有明显的季节差异,氮添加没有改变土壤呼吸季节动态特征;土壤呼吸与土壤温度存在显著相关性,土壤温度与土壤湿度的交互作用能更好地解释土壤呼吸的变异;氮添加在一定程度上改变了土壤呼吸的温度敏感性,其指数Q₁₀值表现为LN(2.12)>CK(2.10)>HN(2.05);不同氮添加条件下,土壤呼吸与土壤硝态氮、溶解性有机碳、pH、碳氮比存在显著相关关系;氮添加对土壤呼吸的促进作用主要表现在生长季,对非生长季土壤呼吸则表现出轻微的抑制作用。

Dynamics of soil respiration and its influencing factors in urban forests under nitrogen addition

Urban forest is an important carbon pool, soil respiration of which is an important part of terrestrial carbon cycle. To understand the dynamics and influencing factors of soil respiration in urban forest under the background of increasing nitrogen deposition, we conducted dynamic observation on soil respiration rate, temperature, moisture and chemical properties by adding 0 (CK), 50 (LN), 100 (HN) kg N·m^-2·a^-1 ammonium nitrate to a typical urban forest. The results showed that soil respiration had significant seasonal variation, which was not affected by nitrogen addition. Soil respiration was significantly correlated with soil temperature. The interaction between soil temperature and soil moisture could better explain the variation of soil respiration. Nitrogen addition changed temperature sensitivity of soil respiration, with the order of Q₁₀ values as LN (2.12) > CK (2.10) > HN (2.05). Soil nitrate concentration, soil soluble organic carbon, pH, soil carbon to nitrogen ratio had significant correlation with soil respiration. The positive effect of nitrogen deposition on soil respiration was mainly in the growing season, with slightly inhibitive effect in the non-growing season.