北方农牧交错区退耕地植被演替调控机制研究

Focusing on the scientific problems of the regulation mechanisms of vegetation succession in northern farming-pastoral ecotone, this project adopts three methods including field control experiment, the transect survey of vegetation and MaxEnt model with the corresponding three spatial scales of sample plot, sample transect and the region. The research aims (1) to study the effect of artificial tending methods on vegetation succession rate in abandoned croplands, so as to illuminate the regulation mechanism of vegetation succession with artificial tending, and select the best tending method for vegetation restoration; (2) to study the influence of natural environment on vegetation succession process in abandoned croplands, so as to illuminate the regulation mechanisms of vegetation succession controlling by topographic feature, soil, hydrology and other environmental factors; (3) to model the suitability of the typical vegetation in the abandoned croplands, and propose optimization solutions. This project will benefit to revealing the regulation mechanisms of vegetation succession, therefore its important application prospect is expected for the restoration of vegetation in northern farming-pastoral ecotone.

本项目拟围绕“北方农牧交错区退耕地植被演替调控机制”这一科学问题，采用野外控制实验、植被样带调查和MaxEnt模型3种主要研究方法，分别在样地、样带和区域3个空间尺度上，(1) 研究人工抚育对退耕地植被演替速率的影响，阐明人工抚育对退耕地植被演替的调控机制，优选出有利于植被恢复的最佳植被抚育方式；(2) 研究自然环境因子对退耕地植被演替进程的影响，阐明地貌、土壤、水文等环境因子对退耕地植被演替的调控机制；(3) 模拟退耕地典型植被的适宜性，提出优化方案。本项目有利于从不同角度揭示退耕地植被演替的调控机制，在北方农牧交错区植被恢复中有重要应用前景。

中国北方农牧交错区是生态脆弱区和生态敏感区，也是三北防护林和退耕还林还草等生态工程的重点区。杨树和刺槐是该地区退耕还林还草的主要造林树种。项目围绕“北方农牧交错区退耕地植被演替调控机制”这一科学问题，以北方农牧交错区的杨树林、刺槐林和草地为主要研究对象，重点研究了干旱、溃疡病和人工抚育等对植被演替的制约关系；探索人工森林和天然草地大面积退化的现状及其原因；模拟了1961-1990、1971-2000、1981-2010，以及RCP4.5和RCP8.5气候情景下北方农牧交错区典型植被的潜在分布及其时空变化。主要研究结果如下：（1）北方农牧交错区杨树林衰退死亡的演替过程是干旱和溃疡病共同促进的。（2）杨树林受到土壤水分和溃疡病胁迫，表现出脆弱性，主要特征是生长缓慢，大面积枯梢和死亡。（3）从草甸草原向荒漠草原，生态功能（生物量、覆盖度、生物多样性等）降低与土壤水分、营养元素（有机质、氮、磷等）的降低具有协同变化特点。（4）MaxEnt模拟结果显示黄土高原适合刺槐林生存的区域位于陕西和山西南部，黄土高原西北和北部地区不适合刺槐林生存。（5）相对于基准年1961-1990，在1960-2010期间刺槐潜在存在概率P > 0.6的区域有缩小趋势。（6）未来RCP4.5和RCP8.5气候情景下刺槐存在概率P > 0.6的区域也存在明显缩小趋势，表现出明显的气候脆弱性。该研究对维持我国北方地区植被可持续发展，防治植被生态系统退化，以及应对气候变化风险等具有重要参考价值。