【摘要】 为解决陕北黄土区水土保持林空间结构不合理的问题,提升森林的稳定性和健康度,通过分析陕北黄土区不同林型林分空间结构特征,对其进行分级评价,来确定抚育优先顺序和抚育措施。以陕西省吴起县水土保持林为研究对象开展样地调查,分析以山杏、榆树、河北杨为优势树种的林分空间分布格局、大小分化程度、垂直结构分布情况,选取混交度、角尺度、大小比数,开敞度、林层指数、竞争指数对林分结构进行综合评价。结果表明:所有样地角尺度均值> 0.517,林分分布格局都属于团状分布;林木大小分化程度榆树>山杏>河北杨;林层指数均值<0.5,表明林层结构简单垂直空间利用率低;竞争指数均在0.2附近,处于弱度竞争或弱度竞争向中度竞争的过渡态。从样地综合得分来看,大部分属于四级样地,3种林型结构状况榆树优于河北杨,山杏林最差。陕北黄土区水土保持林林分空间结构存在树种单一、分布格局不合理的问题,应针对存在问题采取相应措施从而提升森林稳定性和健康度。更多还原

【Abstract】 [Background]In the hilly and gully loess region of northern Shaanxi,due to the complicated terrain and insufficient precipitation, the low survival rate of afforestation and serious individual differentiation of some stands have emerged since the implementation of the project of Returning Farmland to Forest.Traditional afforestation planning and design adopted regular plant and row spacing for planting,and there was a big gap between stand state and ideal structure of near-natural stands.The influence of stand space structure on the overall growth status of stands was ignored in the process of afforestation.[Methods]In order to analyze the spatial structure of soil and water conservation forest in the loess area of northern Shaanxi,three plots( each 40 m × 40 m) were selected for 3 types of forest( Armeniaca sibirica,Ulmus pumila,Populus hopeiensis forests),with the same site conditions.Taking the southwest corner of the plot as the origin,the spatial coordinates of each tree were obtained.The spatial distribution pattern,degree of differentiation and vertical structure distribution were analyzed.The mingling degree,uniform angle index,neighborhood comparison,open degree,forest layer index,and competition index were selected as the evaluation indexes,and the weight analysis was carried out by AHP,and the evaluation function was finally obtained.[Results] 1) The mean value of all uniform angle exceeded 0.517,and stand distribution patterns were clustered type.The tree size differentiation was as follows: U.pumila > A.sibirica > P.hopeiensis.2) The mean value of forest layer index was< 0.5,indicating that the forest structure was simple and vertical space utilization was low.3) The competition indexes were all around 0.2,and they were in the transition state of weak competition or weak competition to moderate competition.According to the comprehensive score of plots,the mean value of all kinds of plots was low,and most of them belonged to grade 4 plots.From the perspective of the forest structure,U.pumila was superior to P.hopeiensis,and A.sibirica was the worst.[Conculsions]The spatial structure of soil and water conservation forest stands in the loess area of northern Shaanxi has the problems of single species and unreasonable distribution,thus we should take corresponding measures to solve the problem.The priority of tending is determined according to the evaluation results of stand spatial structure.Strengthening the mixture and stand density is the major measures, and supplemented by the adjustment of individual trees and improving forest stability and health through proper tending.更多还原