吉林东部天然林林下光质分布特征

Distribution characteristics of undergrowth light quality of natural forests in eastern Jilin

天然林林下光质对乔木幼苗以及灌草的组成与更新具有重要的生态学意义。但目前对于林下光质的研究仍然有限。以吉林东部地区天然林为例,通过调查乔木数据和林下光质数据,基于移动窗口法分析不同空间尺度森林冠层结构与林下光质的关系。结果表明:不同林型下红光光子通量密度(R)与蓝光光子通量密度(B)存在差异。其中沙松-千金榆-花楷槭混交林林下蓝光光子通量密度最小,而沙松-紫椴-臭冷杉混交林和长白落叶松纯林林下最大。随着尺度的增大,天然林乔木胸高断面积与R/PFD(红光/光子通量密度比值)和B/PFD(蓝光/光子通量密度比值)的比值呈显著正相关(P<0.05)。并且随着尺度的增加,相关系数总体逐渐增大,在35m处达到峰值。在此基础上在南向、东向和西向各延伸10m时呈现显著正相关(P<0.05)。在该尺度下分析优势树种对林下R/PFD和B/PFD比值的影响时发现:R/PFD与B/PFD比值随着针叶林胸高断面积的增加而增加。相对于阔叶林来说,多数林型针叶林下的冠层结构与林下R/PFD和B/PFD比值之间显著正相关(P<0.05)。在不同树种下,乔木冠层结构对R/PFD和B/PFD比值的影响不同。总体而言,冠层结构在尺度以及树种组成上存在的差异能在一定程度上影响林下R/PFD和B/PFD比值的分布。本研究结果将有助于我们了解冠层结构对林下光质分布的影响机制,从而为天然林的更新、演替、恢复以及合理经营提供理论依据。

The understory light quality of natural forests has importantly ecological significance for the composition and regeneration of tree seedlings,shrubs and grass.However,the knowledge on the understory light quality is still lacking.In this study,taking natural forests in eastern Jilin Province as an example,by monitoring tree data and understory light quality data,the relationship between forest canopy structure and understory light quality at different spatial scales was analyzed based on the moving window method.The results showed that there were differences between the red light photon flux density(R)and the blue light photon flux density(B)under different forest types.Among them,the blue light photon flux density was the lowest under the mixed forest of Abies holophylla-Carpinus cordata-Acer ukurunduense mixed forest,while the mixed forest of Abies holophylla-Tilia amurensis-Abies nephrolepis mixed forest and Larix olgensis pure forest were the largest.As the scale increased,the tree basal area of natural forest was significantly positively correlated with the ratios of R/PFD(red light photon flux density ratio/photon flux density ratio)and B/PFD(blue light photon flux density ratio/photon flux density ratio)(P<0.05).With the increase of scale,the correlation coefficient increased gradually,reaching a peak at 35 m.On this basis,there was a significantly positive correlation(P<0.05)when it was extended 10 m to the south,east,and west,respectively.When analyzing the influence of the dominant tree species on the ratios of R/PFD and B/PFD under this scale,it was found that the ratios of R/PFD and B/PFD increased with the increase of the basal area of the coniferous forest.Compared with the broad-leaved forest,the canopy structure under most coniferous forests was significantly positively correlated with the ratios of R/PFD and B/PFD under forest(P<0.05).Under different tree species,the tree canopy structure had different effects on R/PFD and B/PFD ratios.In general,differences in canopy structure in scale and tree species composition can affect the distribution of R/PFD and B/PFD ratios under forest to a certain extent.This study would help us understand the influence mechanism of canopy structure on the distribution of understory light quality,so as to provide a theoretical basis for natural forest regeneration,succession,restoration and rational management.