长白山温带森林生态系统关键要素耦合及演替过程动态模拟

认识生态系统内和生态系统间耦合机制,揭示复合生态系统功能规律,对促进我国山水林田湖草沙项目一体化修复和保护实践具有重要的意义。针对目前修复和保护工程中出现的缺乏系统性、连续性等问题,以拥有丰富生态资源的长白山温带森林生态系统为研究区域,对其关键要素"水土气生"进行耦合建模。通过分析模型的运行机理,探究重要子模块之间的相互作用以及子模块内部生态关键要素的耦合机制,并以长白山温带落叶阔叶林的组成树种和环境因素为对象构建模型参数,通过运行林窗模型1000次,得出长白山温带森林的动态演替过程。结果表明:在森林生态系统的演替过程中,"水土气生"体现为模型中有效积温、干旱天数(低于土壤凋萎点的天数)、土壤可利用氮以及可利用光,这些关键要素之间相互影响,综合决定着每棵树木的更新、生长、死亡过程。模拟结果显示在长白山温带针阔混交林的动态演替过程中0-70 a,70-170 a,170-280 a,280-400 a四个阶段分别有不同的树种组成特征,与真实演替过程比较发现模拟林具有明显的阶段性。白桦、山杨为演替先锋树种,0-70 a期间生物量共占比为55%,70 a后生物量减少最后消失;紫椴、蒙古栎、水曲柳等为过渡树种,这些树种进一步改变了生长环境。红松在170 a前生物量占比仅为3%左右,随演替的发展生物量持续增加,170-280 a期间生物量占比15%,280 a之后红松生物量占总林分的50%。该结果模拟森林动态过程符合演替规律,充分说明多关键要素"水土气生"耦合机制的合理性,对于促进生态系统尺度上多生态要素耦合的相关研究提供了科学理论基础以及方法技术。

Coupling key elements and simulating the succession dynamic in the Changbai Mountain temperate forest ecosystem

Understanding the coupling mechanisms within and among ecosystems and revealing the functional laws of composite ecosystems are of significance in promoting the integrated restoration and protection practice of the Mountains-Rivers-Forests-Farmlands-Lakes-Grasslands-Sandlands in China. Considering the lack of systematicness and continuity in current restoration and protection projects, we took the temperate forest ecosystem of Changbai Mountain, which is rich in ecological resources, as the study area, and carry out the coupling modelling of its key elements, "water, soil, air and life".this paper coupled the key elements of the temperate forest ecosystem in the Changbai Mountain.Through analyzing the operation mechanism of the model, we explored the interactions among important sub-modules and the coupling mechanism of key ecological elements within the sub-modules, and constructing the parameters of the model with the constituent tree species and environmental factors of the temperate deciduous broad-leaved forests in the Changbai Mountains, we obtained the dynamic succession process of the temperate forests in the Changbai Mountains by running the forest window model for 1000 times. The results showed that the key elements, such as the degree days, the days of drought (lower than the days of the soil wilting point), soil available nitrogen, and available light mutually influenced each other, which comprehensively determined the regeneration, growth, and death process of each tree. The simulation results also showed that during the succession dynamic process in the Changbai Mountain temperate forest ecosystem, there were distinctly compositional characteristics of tree species in four periods: from 0 to 70 years, from 70 to 170 years, from 170 to 280 years, and from 280 to 400 years. Compared with the actual succession process, we found that the simulated forest had obvious periods. Betula platyphylla and Populus davidiana were pioneer species in succession, accounting for a total biomass of 55% during the 0-70 year period. However, their biomass decreased and eventually disappeared after 70 years; Transition tree species such as Tilia amurensis, Quercus mongolica, and Fraxinus manshurica further altered the growth environment. Initially, Pinus koraiensis accounted for only about 3% of the biomass 170 years ago, but its biomass continued to increase as succession progresses. During the 170-280 year period, Pinus koraiensis biomass accounted for 15% of the total forest stand. After 280 years, Pinus koraiensis biomass represented 50% of the total. These results indicate that the simulated forest dynamics conform to the laws of succession, which fully demonstrating the rationality of the coupling mechanism of multiple key elements "water, soil, air and plant", which provides a scientific theoretical basis and methodological technology for promoting research on the coupling of multiple ecological elements at the scale of the ecosystem.