长白山针阔混交林凋落物-土壤生态化学计量特征

目的 研究林分尺度下凋落物-土壤生态化学计量特征，阐明森林生态系统凋落物和土壤养分的变化规律以及二者的相互关系，为天然针阔混交林的经营和管理提供科学依据。 方法 以长白山北坡4块面积1 hm2的云冷杉-阔叶混交林样地为研究对象，采集0～20、20～40 cm土样，收集半分解层（F层）和完全分解层（H层）凋落物，测定凋落物碳、氮、磷与土壤pH、有机质、全氮、全磷、有效磷和速效钾，并计算凋落物现存量及凋落物-土壤化学计量比。采用相关性分析和冗余分析等方法研究云冷杉-阔叶混交林凋落物特征与土壤养分及化学计量比的关系。 结果 凋落物现存量与0～20 cm土壤碳氮比呈极显著正相关（P < 0.01）。凋落物碳、碳磷比和氮磷比均随凋落物分解程度加深显著降低（P < 0.05）。冗余分析结果表明，F层凋落物现存量与F层凋落物碳、碳磷比和H层凋落物磷具有较强的正效应。凋落物与土壤养分化学计量比均表现为碳磷比> 碳氮比 > 氮磷比。 结论 完全分解层凋落物氮是影响云冷杉-阔叶混交林0～20 cm土壤pH、有机质、全磷、速效钾和土壤碳磷比的关键因子；凋落物氮为20～40 cm土壤全氮的主要来源。因此，凋落物氮可能是驱动研究区土壤养分变化的重要因素。

Eco-stoichiometry Characteristics of Litter-Soil in Coniferous and Broad-leaved Mixed Forest of Changbai Mountains

Objective The ecological stoichiometry of litter-soil at the stand scale was studied to clarify the changes of litter and soil nutrients and their relationship in forest ecosystem, and to provide a scientific basis for the operation and management of natural coniferous and broad-leaved mixed forest. Method Based on the four plots of spruce-fir broad-leaved mixed forest with an area of 1 ha on North slope of Changbai Mountains, soil samples of 0−20 and 20−40 cm and litter samples of the semi-decomposed horizon (F) and completely decomposed horizon (H) were collected. Soil pH, soil organic matter, total nitrogen, total phosphorus, available phosphorus and readily available potassium were determined, and litter standing crop and litter-soil stoichiometric ratios were calculated. The correlation analysis and redundancy analysis were used to study the litter characteristics and their effects on soil nutrients and the stoichiometric ratios in spruce-fir broad-leaved mixed forest. Result The results showed that litter standing crop had a very significant and strong correlation with soil C/N at depth of 0-20 cm (P < 0.01). Litter C, C/P and N/P decreased significantly with increasing litter decomposition degree (P<0.05). The redundancy analysis results showed that litter standing crop had a strong positive effect on the litter carbon and C/P in F horizon and litter phosphorus in H horizon. The stoichiometric ratios of litter nutrients and soil nutrients were C/P > C/N > N/P. Conclusion Litter nitrogen in the H horizon is the critical factor affecting soil pH, soil organic matter, total phosphorus, readily available potassium and C/P ratio in 0−20 cm soil. Litter nitrogen is the main source of total nitrogen in 20−40 cm soil. Therefore, litter nitrogen may be an important factor driving soil nutrient changes in the study area.