季节性雪被对新疆天山雪岭云杉林凋落物分解的影响

Litter decomposition is one of the key ecological processes of carbon turnover and nutrient cycling in forest ecosystem. Seasonal snow cover is considered to be the important factors of controlling forest ecosystem structure and function in mid and high latitude mountain regions, which may play an important role in litter decomposition of forest ecosystem. However, little information has been available on the effects of different snow depths on litter decomposition of forest ecosystem in arid areas. Taking Picea schrenkiana forest in Tianshan Mountain of Xinjiang as the test object, this research will conduct a field litterbag experiment to investigate litter decomposition. The air-dried leaf litter of Picea schrenkiana will be placed in litterbags, and placed on the forest floor along a snow cover gradient from forest gap to under the canopy. The samples will be retrieved at different critical stages (onset of freezing period, deep freezing period, thawing stage early growing season, mid-growing season, and late growing season) during two years of decomposition. The properties of litter decomposition and litter quality will be monitored while the patterns of major elements migration will be studied. We will analyze influences of abiotic environmental factors (temperature, moisture and soil nutrient) and biotic factors (litter quality, soil microorganisms and soil animals) to litter decomposition under different snow cover conditions, and identify the major degradative enzyme contributors, which will be used to determine driving forces of litter decomposition. This study attempts to reveal litter decomposition properties and theirs driving mechanism in mountain forest ecosystem of arid areas, and explore effects of snow cover change on litter decomposition. Our findings will supplement the study on ecological process of mountain forest ecosystem driven by snow, and be beneficial for extending research fields of biogeochemical cycle in terrestrial ecosystems. Results will provide significant references for the optimized management and applicable protection of forest ecosystem.

凋落物分解是森林生态系统碳素周转和矿质养分循环的关键生态过程。森林异质环境形成的季节性雪被是控制中高纬度地区山地森林结构和功能的重要因素，可能显著影响凋落物分解，而干旱区山地森林凋落物对雪被的响应机制尚不明确。本研究以新疆天山北坡中山带雪岭云杉林为对象、样区内林窗中央至林下形成的天然雪被为梯度，分析不同厚度雪被下凋落物在雪被形成期、覆盖期、消融期及非雪被期的分解特征和基质质量动态，判断不同元素迁移模式；讨论雪被对非生物因子（温度、水分、土壤养分）和生物因子（基质质量、土壤微生物、土壤动物、酶活性）的影响以及凋落物分解与各因子的关系，确定主要的凋落物分解酶，多角度探求凋落物分解的驱动因素。研究旨在揭示雪被作用下干旱区山地森林生态系统凋落物分解特征和驱动机制，探讨冬季环境改变对森林物质循环的影响，补充雪因子对干旱区山地森林生态过程驱动的研究成果，促进森林的优化管理和合理保护。

凋落物分解是森林生态系统碳素周转和养分循环的关键生态过程。森林异质环境形成的季节性雪被是控制中高纬度地区山地森林结构和功能的重要因素，可能显著影响凋落物分解，而干旱区山地森林凋落物对雪被的响应机制尚不明确。本研究以新疆天山北坡中山带雪岭云杉林为对象、样区内林窗中央至林下形成的天然雪被为梯度，分析了不同厚度雪被下凋落物在雪被形成期、覆盖期、消融期及非雪被期的分解特征和基质质量动态，判断了不同元素迁移模式，讨论了雪被对非生物因子和生物因子的影响以及凋落物分解与各因子的关系，多角度探求凋落物分解的驱动因素。结果表明：经过两年的分解，雪岭云杉凋落物总干重损失量达33-41%，其中，第一年损失量为25-29%，第二年为6-9%。不同雪被厚度下质量损失综合表现为厚雪被>中型雪被>薄雪被>无雪被。随分解凋落物C浓度下降，C素逐渐释放；N浓度先降低后增高，N素为先富集后释放；P浓度冬季高于生长季，P素先略微富集后逐渐释放。凋落物木质素为富集状态，纤维素为先释放后富集再释放。林下土壤细菌中变形菌门、放线菌门、酸杆菌门和拟杆菌门相对丰度约占总和80%，属优势种群；土壤真菌中被孢霉门、担子菌门和子囊菌门的对丰度约占总和70%，属优势种群。土壤细菌多样性表现出在冻融初期较小，在深冻期和生长季中期较大；土壤真菌多样性则在生长季中期最高。不同雪被梯度下凋落物干质量与凋落物C、P、纤维素、C:N和C:木质素间均具有显著或极显著正相关，与凋落物N、木质素、C:P和木质素:纤维素间呈较强负相关。细菌和真菌多样性指数多与凋落物性质呈负相关。研究揭示了雪被作用下干旱区山地森林生态系统凋落物分解特征和驱动机制，探讨了冬季环境改变对森林物质循环的影响，补充了雪因子对干旱区山地森林生态过程驱动的研究成果，有助于促进森林的优化管理和合理保护。

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