基于光竞争截止系数的崇礼冬奥核心区华北落叶松人工林目标树抚育间伐模拟

Simulation on Crop Tree Management Tending and Thinning of Larix principis-rupprechtii Plantation in Chongli Winter Olympics Core Area Based on Coefficient of Light Competition

【目的】以崇礼冬奥核心区华北落叶松人工近熟林为研究对象,探讨目标树抚育间伐采伐木选择方法及其对林分空间结构的影响,为更加合理开展森林经营活动、促进人工林质量提升提供科学依据。【方法】设置并调查6块面积0.09 hm^(2)(30 m×30 m)标准地,按125株·hm^(-2)目标树密度,采用定性与定量指标相结合的方法标记目标树。基于树冠重叠和树冠光竞争高度构建采伐木选择指标,设置不同光竞争截止系数(c)模拟选择采伐木,分析采伐强度变化,运用角尺度、混交度、密集度、交角竞争指数、林层指数和综合空间结构指数分析不同c值下目标树和林分空间结构指标的变化。【结果】c取值在0~1之间时,株数采伐强度和断面积采伐强度在10%~35%范围内变化,且呈随c值增大而降低的相同变化趋势。经模拟采伐后目标树空间结构得到优化,改善幅度随采伐强度增大而增大。综合空间结构指数在c值0.6时达到最大提升幅度45.50%,角尺度和密集度在c值0.7时变化幅度最大,分别为17.93%和46.83%,其他空间结构参数在c值0.6时达到最大变化幅度。抚育间伐可同时优化林分空间结构,对林分树种隔离程度、林木透光条件和竞争水平均具有不同程度改善。【结论】基于树冠重叠和树冠光竞争高度的采伐木选择方法,可通过调整光竞争截止系数控制采伐强度。树冠光竞争截止系数可作为目标树经营采伐木选择的约束条件,但具体抚育对象和抚育方式须结合林分特征和作业要求而定。

【Objective】Taking larch near-mature plantations(Larix principis-rupprechtii)in the core area of Chongli Winter Olympics as objects,this paper was carried out to discuss the selection method of target trees thinning and its effects on forest spatial structure in order to provide scientific bases for reasonable management activities making and plantation quality improvement.【Method】Six sample plots with the area of 0.09 hm^(2)(30 m×30 m)were set up and measured.125 tree·hm^(−2) target trees were marked according to qualitative and quantitative indicators.Based on crown overlap and crown light competition height,the method of cutting trees selection was developed,which was used to select cutting trees simulated in 6 sample plots by setting different values of light competition coefficient().Changes on cutting intensity were analyzed while those of target tree and stand spatial structure indexes under different c values were analyzed by using angular scale,mingling,crowding,intersection competition index,storey index and comprehensive index.【Result】The cutting intensity of both tree number and basal area varied from 10%to 35%when the value of ranged from 0 to 1,indicating the same trend of decreasing with the increase of value of.The spatial structure of target trees was optimized by simulated tending thinning,and the improvement increased along with the increase of cutting intensity.The maximum increase of comprehensive spatial structure index was 45.50%when value of was 0.6.The maximum improvement of angular scale and crowding were 17.93%and 46.83%,respectively,under value was 0.7,while other spatial structure parameters reached the maximum improvement with the values of cis 0.6.Thinning also optimized the spatial structure of stand,and improved the isolation degree of tree species,light transmission conditions and competition level among trees in different degrees.【Conclusion】The thinning intensity could be controlled by adjusting the coefficient of light competition using cutting trees selection method based on crown overlap and crown light competition height.The coefficient of canopy light competition could be used as a constraint for selecting cutting trees of crop tree management.However,the thinning objects and thinning methods should be determined according to the stand characteristics and operation requirements.