沙丘植被斑块网络及其对榆树疏林天然更新的调控

Vegetation patches, distributed in the sandy land ecosystem all over the world, are the important characteristics of sand dune ecosystems. The vegetation patches (high coverage) and bare patches(low coverage) form patches network. Vegetation patches not only have the characteristics of size, coverage and area, but also have the characteristics of network structure. Elm tree is the primary species in the Horqin Sandy Land and Hunsandak Sandy Land, and its natural regeneration is widely concerned. It is not clear that how the natural regeneration of elm trees is affected by vegetation patches. The reason maybe that the network characteristics of vegetation patches are poorly understood, the field investigation of seed dispersal is not suitable for long distance dispersal seeds and the seed dispersal model is insufficient for the heterogeneity of underlying surface. The rapid development of network analysis methods makes it possible to analyze the influence of vegetation patch network on seed diffusion. Meanwhile, individual models could well simulate the migration and interaction of individual in the heterogeneous patches. In this project, we use field investigation, laboratory analysis, controlled experiments, network analysis, statistical analysis and model simulation to analyze vegetation patch network characteristics, to study effects of vegetation patch network on seed dispersal, seed germination, seedling growth, and to build individual model with patch structures. The aim of this project is to answer scientific questions, i.e. what are the characteristics of vegetation patches network in dune ecosystems and how the vegetation patches network regulates the regeneration of elm trees in sparse woodland. This study is helpful for clarifying the vegetation patch characteristics, and revealing the mechanisms of regeneration of elm trees, and plays a key role in providing a scientific basis for the elm trees reproduction, vegetation restoration and fragmentation of habitat protection.

植被斑块在全球沙地生态系统中均有分布，表现为高盖度植被斑块与低盖度裸地斑块镶嵌排列，构成斑块网络。植被斑块不仅具有大小、盖度、面积等特征，而且具有网络结构特征。榆树疏林是科尔沁沙地和浑善达克沙地原生植被，其天然更新广受关注。榆树疏林天然更新如何受植被斑块影响尚不完全清楚。其原因可能在于植被斑块网络特征知之甚少，种子扩散野外调查对长距离扩散种子不完全适用，种子扩散原有模型对下垫面异质性考虑不足。本课题利用野外调查、室内分析、控制试验、网络分析、统计分析与模型模拟等方法，分析植被斑块网络特征，研究植被斑块网络对种子扩散、种子萌发、幼苗生长的影响，构建基于斑块网络的榆树疏林天然更新模型，试图回答沙丘生态系统植被斑块网络有何特征，植被斑块网络如何调控榆树疏林天然更新等关键科学问题，从而阐明植被斑块网络特征，揭示榆树疏林天然更新内在机制，为榆树疏林种群繁衍、沙地植被恢复与破碎化生境保护提供科学依据。

植被斑块在全球沙地生态系统中均有分布，表现为高盖度植被斑块与低盖度裸地斑块镶嵌排列，构成斑块网络。植被斑块不仅具有大小、盖度、面积等特征，而且具有网络结构特征。榆树疏林是科尔沁沙地和浑善达克沙地原生植被，其天然更新广受关注。榆树疏林天然更新如何受植被斑块影响尚不完全清楚。本项目在前期研究基础上执行，以科尔沁沙地为研究区，利用野外调查、室内分析、网络分析、控制实验、统计分析和模型模拟等方法开展综合研究，探究沙丘生态系统植被斑块网络特征，回答植被斑块网络如何调控榆树疏林天然更新的科学问题。本项目提出刻画种子扩散与休眠过程的集合种群模型，发现增加种子扩散率和降低休眠种子死亡率有利于种群维持；初步建立植被斑块框架下的榆树种子扩散多智能体模型，并通过野外实验验证模型有效性，发现植被斑块影响下的风力驱动是影响种子扩散的重要影响因素。榆树种子扩散数量在各个方向上呈现先增加后减小的单峰分布的规律，在各方向上种子扩散距离和种子数量相差均不明显；通过计算不同沙丘类型下的典型群落生态服务价值，发现榆树疏林群落的生态系统服务价值高于其他典型群落类型，提出从提高生态系统服务价值的角度，稀疏榆林应予以优先保护。本项目有助于阐明植被斑块网络特征，揭示榆树疏林天然更新内在机制，为榆树疏林种群繁衍、沙地植被恢复与破碎化生境保护提供科学依据。