白龙江上游云冷杉林垂直层次叶面积指数空间分异格局OACHSSCD

The Leaf Area Index(LAI)serves as a fundamental biophysical parameter critical for describing vegetation canopy architecture,quantifying photosynthetic potential,and modeling the exchange fluxes of carbon,water,and energy within terrestrial ecosystems.Its spatial heterogeneity constitutes a key attribute that fundamentally determines the structural organization and functional dynamics of forest ecosystems.Conducting precise quantification of this heterogeneity is therefore essential for achieving a more profound mechanistic understanding of how ecosystems respond and adapt to environmental changes.This study targeted the spruce-fir dark coniferous forest(constructive species:Picea asperata,Picea purpurea,Abies fargesii var.faxoniana)in the upper reaches of the Bailong River.Our methodology integrated digital hemispherical photography(DHP),a widely used optical technique for indirect LAI estimation,with a suite of geostatistical analysis tools.This combined approach was employed to systematically dissect and characterize the spatial distribution patterns of LAI across three distinct vertical strata:the canopy layer,the understory vegetation layer(comprising shrubs and herbs),and the integrated whole-stand level.The key findings of our investigation are summarized as follows:(1)The total whole-stand LAI was measured at 2.32±0.07.Within this total,the canopy layer,with an LAI of 1.55±0.06,functioned as the predominant contributor.However,the understory vegetation layer also presented a substantial and non-negligible LAI value of 0.91±0.05,underscoring its functional significance.(2)Compared with the canopy,the understory LAI exhibited higher spatial variability and a significantly right-skewed distribution,with a weak positive correlation observed between them.(3)From a spatial perspective,areas characterized by high LAI values across all three vertical layers were consistently aggregated in the northern sector of the study area.Conversely,zones of low LAI exhibited a high degree of spatial overlap,concentrated predominantly in the central portion of the sampling plot.(4)All layers showed pronounced spatial directional dependence.The azimuths of the maximum range for the whole-stand,canopy,and understory LAI were 155.39°(range 39.04 m),149.06°(range 72.46 m),and 107.92°(range 72.46 m),Standard deviational ellipse analysis further revealed that the dominant orientation angles(major axis directions)for their spatial point distributions were 7.68°,20.36°,and 9.88°,respectively.This research substantiates that understory vegetation acts not merely as an important reservoir for forest biodiversity,but also as a critical structural component that actively shapes the spatial heterogeneity of the entire ecosystem.The results provide crucial spatial pattern parameters and theoretical support for modeling processes in alpine forest ecosystems,accurately assessing carbon sinks,and formulating biodiversity conservation strategies.