寒温性云杉次生林树种更新过程中幼苗生态化学计量特征的时空格局及环境响应

Refering to the technical specifications for tropical rain forest sample plots established by the Center for Tropical Forest Sciences (CTFS), we are going to make a series of study in 5 established Guandi Mountain permanent forest dynamic plots (equal altitude difference is 100 m). In this study, we will acquire continuous dynamic monitoring data on C、N、P stoichiometry of different aged regeneration seedling leaf, brunch and root by means of laboratory experiment. Combining phenotypic morphology indicators measured data of seedling with different growth rate, soil C、N、P stoichiometry measured data and environmental factors survey data, we will study the spatiotemporal pattern and variation characteristics of C、N、P stoichiometry in each tree species seedlings and their relations to environmental factors such as altitude, temperature, soil. This study aims to illuminate temporal and spatial patterns and environmental response of ecological stoichiometry of generation seedling in cold temperate Picea secondary forest in small scale. Results will shed light on the basic approach for species ecological stoichiometry control in the process of forest regeneration and help to further understand the ecological adaptation strategies and regeneration mechanism of seedlings in the process of natural regeneration, which will be an important supplement to constructing a natural regeneration theory of forests.

本项目以关帝山林区5个云杉次生林固定样地 (样地间海拔梯度为100 m) 为研究平台，按照CTFS热带雨林样地技术规范并结合室内实验，获取样地各更新树种不同龄级幼苗各器官(叶枝根)碳氮磷化学计量定位连续监测数据，同时结合幼苗异速生长性表型形态指标测定、土壤碳氮磷化学计量测定和环境因子调查，在群落水平上研究云杉次生林各更新树种幼苗生态化学计量的时空格局及变异特征、格局及变异与海拔、温度、土壤等环境因子的关系。研究旨在综合阐释寒温性云杉次生林树种更新过程中幼苗小尺度生态化学计量特征的时空变异及环境响应，结果将揭示森林生态系统树木天然更新过程中幼苗生态化学计量调控的基本途径，以及天然更新幼苗的生态适应策略和更新机制，为森林天然更新理论的构建做重要补充。

为从元素水平上揭示树种更新过程中幼苗生态化学计量调控的基本途径，项目研究了华北寒温性云杉次生林树种天然更新过程中：（1）幼苗碳、氮、磷计量在不同发育阶段（年龄）和生长季节的时间分异及格局特征；（2）幼苗碳、氮、磷计量的空间分异及格局特征；（3）云杉幼苗更新过程中的碳、氮、磷调控；（4）云杉幼苗更新过程中碳、氮、磷计量化学计量特征变异的环境解释。结果表明，（1）随龄级和海拔增加，云杉幼苗叶长、宽、周长、面积在增加，比叶面积在减小，叶形态与其碳、氮、磷计量存在显著相关性。（2）幼苗碳、氮、磷计量水平一方面随发育年龄和生长季节变化，表现出异速生长的特征，主要表现为，随龄级增加，叶片C、P含量、C:N值在增加，N含量、C:P及N:P值在减小；另一方面，环境中的土壤和光分别作为植物吸收碳、氮、磷的重要养分来源和植物光合调控碳、氮、磷形成的重要能量来源影响幼苗的碳、氮、磷计量水平，主要表现为随海拔变化的土壤C、N、P与根系C、N、P显著正相关，根系和土壤C、P含量与叶片C、P含量显著正相关，与叶片N含量显著负相关。受海拔影响的光合过程中的Rubisco酶活力与幼苗叶片C、N、P存在耦合关系。（3）云杉叶片C、N、P通过影响叶片形态特征从而对幼苗的更新过程起调控作用。叶片C、N、P计量受根系及土壤C、N、P计量的影响，同时与调控C、N、P形成的Rubisco酶活力密切相关。土壤C、N、P含量能很好的解释云杉幼苗叶片C、P含量的变化；Rubisco酶活力对叶片C、N、P含量的解释量均高于土壤各养分含量对叶片C、N、P含量的解释量。研究结果以期为森林生态系统树木天然更新理论的构建提供重要基础依据。