Modeling the Potential Distribution of <i>Machilus thunbergii</i>under the Climate Change Patterns in China

The potential geographic distribution and favorable climatic conditions of Machilus thunbergii under current and future predicted climates in China are predicted based on MaxEnt model and ArcGIS software. The results show that the AUC values in different time periods and emission seniors are more than 0.9, which indicates the prediction is excellent. Precipitation of the coldest quarter, precipitation of the driest month, annual precipitation, mean diurnal range, and temperature annual range are the most important environmental factors affecting the distribution of Machilus thunbergii. At present, the suitable areas of Machilus thunbergii are mainly concentrated in the eastern subtropics of China, with a total area of 118.47 × 104 km2. The medium-suitability area and the high-suitability area are concentrated in Wuyi Mountains, Luoxiao Mountains, Xuefeng Mountains, Nanling and east of Taiwan Mountains. With the change of climate, the suitable area increases, and the medium-suitability area and high-suitability area migrate and expand to the east, and the low-suitability area expands slightly to the west and north. So, the simulated distribution of Machilus thunbergii should be one of priorities, when instigating in-situ conservation. The research results can provide a theoretical reference for the popularization and planting of Machilus thunbergii.

浙江定海次生林内物种丰富度与生物量和生产力关系的环境依赖性

迄今生物多样性与生态系统功能关系的研究主要在物种组成随机配置的人工生态系统中进行,在自然生态系统中研究较少,且未考虑环境因子如何影响生态系统功能及其与生物多样性的关系。本研究选取亚热带广泛分布的次生林为研究对象,利用模型拟合的方法,探讨亚热带次生林中物种丰富度与生物量和生产力之间的关系,以及环境因子(海拔、坡度、坡向、土层厚度)和次生林恢复时间(林龄)对生物量、生产力、物种丰富度与生物量和生产力间关系的影响。结果表明,当不考虑环境因子时,物种丰富度与生物量之间存在显著的线性正相关关系,而与生产力之间存在显著的二次关系(先增加后减少的驼峰型)。当考虑环境因子时,个体密度和土层厚度对生物量具有显著影响,而环境因子对生产力并无显著效应。在坡度较陡、坡向朝南及土层较厚的环境条件下,物种丰富度与生物量具有显著的线性正相关关系;而在坡度较缓、坡向朝北及土层较薄的环境条件下,物种丰富度不影响生物量。在较高海拔环境条件下,生产力随物种丰富度先增加后减少(驼峰形状),而在其他环境条件下,生产力均不响应物种丰富度。以上结果说明自然森林生态系统中物种丰富度与生物量和生产力的关系存在差异,且其相互间的关系依赖于环境因子。