基于NSGA-Ⅱ算法的若尔盖高原高寒湿地生态修复格局优化

Optimization of ecological restoration pattern of alpine wetland in Zoige Plateau based on NSGA-Ⅱalgorithm

随着全球气候变暖和人类活动增强,高寒湿地面临着面积萎缩、动植物生境恶化、生态系统结构和功能退化等环境问题。以若尔盖高原高寒湿地为研究对象,基于生态系统稳态转化理论,使用湿地景观演变函数和第二代非支配排序遗传算法(non-dominated sorting genetic algorithmⅡ,NSGA-Ⅱ)分析1980—2015年7期湿地动态变化,计算多情景多目标函数值,选择适宜目标并基于社会经济生态可持续性发展、湿地生态系统稳态平衡原则,制订湿地修复优化策略。结果表明,可持续发展区、过度关注区与过度扰动区呈围绕发展,分别占湿地总面积的45.25%、17.27%与37.48%;基于NSGA-Ⅱ算法评价无偏好(等权最优)、经济效益最大化、生态效益最大化、空间紧凑度最大化、修复适宜性最大化5个目标下的湿地修复策略,无偏好策略函数值在经济效益、生态效益与湿地修复适宜性方面分别提升41.45%、9.18%和1.65%;基于社会经济可持续性发展的需求,构建保护优先、自然恢复、近自然恢复和适度修复4类若尔盖高原湿地生态修复空间优化格局。

[Background]The Zoige Plateau is the most important ecological function area in the eastern margin of the Qinghai-Tibet Plateau,and is also a sensitive area of climate change and ecological environment,with the largest alpine marsh in the world.With warming of global climate and enhancement of human activities,the Zoige Plateau alpine wetland is faced with the environmental problems such as the area shrinkage,the deterioration of animal and plant habitat,and the degradation of ecosystem structure and function.Protecting the local unique ecological environment and exploring the best way to restore the ecology of alpine wetland have become the focus of current research,and are also the research objectives of this paper.[Methods]Taking the Zoige Plateau alpine wetland as the research object and based on land use data,wetland landscape evolution function was adapted to analyze the dynamic changes of wetlands in seven periods from 1980 to 2015.Based on the data of ecological and economic benefits of various finished products,the NSGA-Ⅱ(non-dominated sorting genetic algorithmⅡ)was applied to calculate multi-scenario and multi-objective function values,and to compare the differences of the function values.Finally,according to the principles of sustainable development and ecosystem stability,appropriate function results were selected to formulate the optimization strategy of wetland restoration.[Results]1)Sustainable development area,over-concerned area,and over-disturbed area accounted for 45.25%,17.27%and 37.48%of the total wetland area,respectively.On the whole,there were many unreasonable restoration behaviors and over-utilization behaviors in the Zoige wetland.2)Based on the principles of sustainable social and economic development and ecological protection,a multi-objective optimization model for ecological restoration of Zoige Plateau alpine wetland was constructed.With the help of the NSGA-Ⅱalgorithm,the wetland restoration strategies with five objectives were evaluated,including no preference(equal weight optimal),maximum economic benefit,maximum ecological benefit,maximum spatial compacity and maximum restoration suitability.As the optimal land use scheme,the function value of no preference strategy increased by 41.45%in economic benefit,9.18%in ecological benefit and 1.65%in wetland restoration suitability respectively.3)The spatial optimization pattern for the ecological restoration of four types in Zoige Plateau wetland was constructed,which gave priority to conservation,combined with natural restoration,near-natural restoration and moderate restoration.The area proportions of the four restoration methods were 57.93%,16.08%,17.50%and 11.67%,respectively.[Conclusions]Most areas of the alpine wetland of the Zoige Plateau are sustainable development areas,and the proportion of over-disturbed area is bigger than that of over-concerned area.It presents a spatial pattern with the sustainable development area as the center and other regions around the sustainable development area.According to the optimized allocation results for conservation and sustainable utilization of wetland resources,no preference strategy and optimization partition scheme can provide support for management of alpine wetland.The optimization method can be easily adapted to other regions by modifying the fitness functions and findings can provide a more scientific reference for the conservation and restoration plan of alpine wetland.