黄土丘陵区森林植物-凋落物-土壤化学计量特征耦合关系及对非生物环境因子的响应

To clarfy the coulped relation of plant-litter-soil stoichiometric of forest ecosystems and its responses to abiotic facors is better to understand the nutrient limition on the maintenance of forest ecosytem structure, function and productivity.The main task of the current pending project is to show the temporal-spatial stoichiometric characteristics of plant, litter and soil of middle-aged forest ecosystems between Pinus tabulaeformis and Robinia pseudoacacia plantations and Pinus tabulaeformis and Quercus wutaishanica natural secondary forests in the Loess Hilly Region. By measure the seasonly concentrations of C, N and P in the leaves, branch, stem, fine and corase roots of tree, shrub and herb on permanment sample plots under different climate gradients, the coulped relation on nutrient cyclying and balance constraints will be elucidated in the plant-litter-soil continuous flow system. Final, combining with the data of abiotic factors, to explain the regulation mechanism of the temporal-spatial stoichiometric characteristic patterns of forest ecosystems and try to scenario prediction of the effect of nutrient limition on forest ecosystems. The outcome of the current pending project would be explicit the dynamic balance and driving effect of C, N and P in the plant-litter-soil continuous flow system on the regulation strategy for optimum structure and fuction promotion of forest ecosystems,and explore the sustainable management model for vegetation restoration and reconstruction for these areas under global climate change.

明晰森林生态系统中植物-凋落物-土壤化学计量特征的耦合关系，及其对非生物环境因子的响应，有助于理解森林生态系统结构、功能和生产力维持的养分调控限制因素。本研究选取黄土丘陵区主要分布的油松和刺槐人工林，及油松和辽东栎天然次生林的中龄林为研究对象，通过设立不同环境梯度下的固定样地，在研究期内连续测量乔-灌-草不同器官(叶、枝、干、细根和粗根)、凋落物和土壤中碳氮磷含量的季节变化，阐明不同森林类型植物、凋落物、土壤的化学计量特征，及三者在养分循环和平衡制约间的耦合交互关系。结合降雨、温度、土壤水分等非生物环境因子，探明森林生态系统化学计量时空变化格局特征的调控机制并尝试对养分限制进行情景预测。该研究旨在探讨黄土丘陵区森林生态系统结构优化，功能提升的调控对策中碳氮磷在植被-凋落物-土壤中的动态平衡和驱动作用，探索全球气候变化下适合该地区森林生存策略的植被恢复和重建的经营管理调控模式。

本研究以黄土丘陵区人工林和天然林为研究对象，通过水分空间尺度和季节、年份时间尺度对植物--凋落物--土壤系统碳（C）、氮（N）、磷（P）化学计量特征进行了研究，主要得到以下结果：1、对于人工林树种刺槐和油松而言，空间水分梯度上，碳氮磷计量特征并无显著变化，其差异主要体现在树种间，固氮树种刺槐相比油松，其N、P含量要高，而C含量要低，刺槐C：N和C：P低于油松，N:P则高于油松； N、P具有良好的协同变化特性，而针对土壤来说，碳氮磷都表现出了表聚性，与植被层不同的是，土壤有机碳与土壤全氮间有着良好的协同变化特征，C：N变化幅度远小于C：P和N：P。2、对于天然林和人工林而言，起源对其化学计量组成并没有大的影响，其差异仍取决于树种，无论天然林抑或人工林，针叶树种植物组分均具有高的C含量，低的N、P含量。以上结果表明：植物CNP化学计量特征在较小的时间和空间尺度上具有良好的稳定性，种间不同的生理生态特性导致其计量组成的差异。