特大冰冻干扰后大明山常绿阔叶林冠层结构空间异质性动态

Spatial Heterogeneity Dynamics of Canopy Structure in Evergreen Broadleaved Forest after a Severe Ice Storm Disturbance in Damingshan,Southern China

关键词:  常绿阔叶林  林冠结构  林冠开度  叶面积指数  空间异质性

Key words:  evergreen broadleaved forest  canopy structure  canopy openness  leaf area index  spatial heterogeneity

摘要:

[目的]揭示大明山常绿阔叶林灾后恢复中冠层结构的空间变化规律及空间异质性动态,为监测灾后受损森林生态系统的恢复能力及灾后管理提供理论依据。[方法]对2008年特大冰冻干扰后大明山常绿阔叶林的林冠结构进行了连续4年的监测,采用半变异函数和Moran's I指数对其林冠开度(Canopy openness,CO)和叶面积指数(Leaf area index,LAI)进行空间异质性和空间自相关性分析。[结果]冰冻干扰后4年间,大明山常绿阔叶林林冠开度的均值先减小后微弱增加,叶面积指数的均值先增加后微弱减小,2011年林冠开度最小、叶面积指数最大。半变异函数的指数模型和球状模型可较好地描述各年度样地林冠开度和叶面积指数的空间异质性。2011年和2012年林冠开度的空间变异程度大幅增加,结构性因素引起的空间变异大于随机因素;2010年叶面积指数的空间异质性大幅度增加,但随后两年其空间异质性大幅度降低并趋于稳定,空间异质性尺度较小且主要由结构性因素引起。[结论]在灾后恢复的第3~4年间,大明山常绿阔叶林冠层结构已有较大恢复,但恢复程度在空间上的变异极大。随着恢复演替的进行,大明山常绿阔叶林林冠结构在空间上向着越来越不均匀的方向发展,而叶面积指数则逐渐趋于稳定。

Abstract:

[Objective] The objective of this study was to reveal the dynamics of spatial change and heterogeneity of canopy structure after an ice storm disturbance in evergreen broadleaved forest in Damingshan.[Methods] The spatial heterogeneity dynamics of canopy structure were successively investigated in evergreen broadleaved forest in Damingshan from 2008 to 2012 after a severe ice storm disturbance.Semivariogram function and Moran's I index were employed to analyze the spatial heterogeneity and autocorrelation of canopy openness (CO) and leaf area index (LAI).[Results] During the 4 years after the ice storm disturbance, canopy openness showed an initial decrease and a subsequent slightly increase, while LAI showed an initial increase and a subsequent slightly decrease.Canopy openness decreased to the lowest and LAI increased to the highest in 2011.Geostatistical analysis indicated that the semivariogram function of canopy openness fitted with exponent (from 2009 to 2011) and spherical (2012) models which demonstrated structure factors with high spatial autocorrelation at middle scale.The degrees of spatial variation of canopy openness significantly increased in 2011 and 2012 compared with that in 2009 and 2010.The semivariogram function of LAI fitted with spherical (2009 and 2010) and exponent (2011 and 2012) models which also significantly demonstrated structure factors with high spatial autocorrelation at small scale.The degrees of spatial variation of LAI markedly increased in 2010, but gradually decreased and plateaued thereafter.[Conclusion] The canopy structure of this evergreen broadleaved forest had recovered to some extent during the third to the fourth years after disturbance.However the recover degree exhibited great spatial heterogeneity.Consequently, the spatial distribution of canopy structure of the evergreen broadleaved forest in Damingshan could become more and more heterogeneous while LAI could tend to stabilize with the development of the restoring succession.