Search

Recent studies have documented local-scale associations between tree species and habitat factors in forests worldwide.A 30 hm2 plot(500 m×600 m) was established in the Jiaohe Forestry Experimental Zone Bureau of Jilin province to study the long term dynamics of a broad-leaved Korean pine mixed forest.Within the plot,all free-standing trees and shrubs with a DBH of at least 1cm were identified,tagged and mapped,and their geographic coordinates recorded following a standard field protocol.One objective was to study mechanisms of the formation of spatial distribution patterns of understory tree species and to explore how environmental gradients influence these patterns in a broad-leaved Korean pine mixed forest.Based on the data from the 30 hm2 plot,all trees with a DBH not greater than 5cm were defined as under storey trees.Only species represented by at least 300 individuals were chosen.14 tree species representing 94.32% of all understorey trees satisfied this condition.First,the spatial patterns of the 14 selected species were analysed at scale of 20m×20m cells,using Morisita′s index(Iδ).The results indicate that all 14 species show a clumped spatial distribution.Second,the spatial autocorrelations of the 14 species were studied at 15 distance classes using the spatial autocorrelation coefficient Moran′s I.The results show a significant positive correlation at small distance classes and significant negative correlations at large spatial distance classes in most species were.Third,the partial Mantel test was used to find the relationship between the abundance of the 14 tree species and certain habitat factors.The results show a significant correlation with spatial distances for 6 species which reprtesent 42.86% of the tested species.7 species(50%) were significantly correlated with habitat factors.4 species showed neither a significant correlation with spatial distance nor with habitat factors.3 species showed a significant correlation with both distance and at least one habitat factor.5 of 7 dominant species with more than 1000 individuals had significant correlation with spatial distances.5 species had significant correlation with habitat.The partial Mantel tests suggested that the mass effect from neighboring quadrats and habitat association could explain most of the tree species abundance distribution in a quadrat in the broad-leaved Korean pine forest community.At last,the Pearson correlation coefficient between species abundance in a quadrat and microtopographic attributes of the quadrat was calculated to test the effects of microtopography(elevation,slope,aspect,convexity) on species distribution.The results showed that Acer mono,Carpinus cordata preferred lower elevations and southern aspects.Acer barbinerve,Acer ukurunduense and Corylus mandshurica preferred higher elevations,steeper slopes and north-facing aspects.This result shows obvious habitat niche specialization and confirms niche theory.It is concluded that habitat niche specialization and mass effect are important factors in structuring distributions of understorey tree species in a broad-leaved Korean pine forest community.Many tree species prefer similar habitats which indicates similar resource usage and niche overlapping.Other tree species prefer specific habitat indicating repellency between different species,which may be the result of long term adaptation to different habitats,different resource usage,and which may explain the niche separation.

In order to study the structure of herbaceous biodiversity and its effect factors in broad-leaved Korean pine forest, a total of 100 1-m2 sub-plots were established in the 1 ha site which was monthly investigated from May to September in 2009. Data on soil attributes were also investigated (soil organic matter, available nitrogen, available phosphorus, available potassium, soil, water and pH) without light environment (leaf area index (LAI), photosynthetic photon flux density (PPFD) and, canopy presence). In this paper, the relationships between different layers (tree, shrub and herbaceous), soil attributes and light environment were analyzed. The effects of tree and shrub layers, soil attributes and light environment on the structure of herbaceous diversity were also discussed. The results show that there is an obvious seasonal dynamic for the herb in broad-leaved Korean pine forest. It was dominated by Anemone amurensis (Korsh.) Kom. and Corydalis ambigua Cham. et Schltdl. in May. The highest species richness was in June, when spring ephemeral, early and late-summer plant grew at the same time. July was the growing season and had highest diversity. From August to September, summer plant became withered gradually. There is a significant positive correlation between the diversity in shrub and herb layer Density of shrub layer positively correlated with the cover of herb layer, but negatively correlated with the diversity of herbaceous layer. The effect of the tree layer on the cover and the diversity of herbaceous layer did not arrive at the significant level. The correlation analysis of the cover, diversity and soil attributes, light environment at herbaceous layer, as well as the tree and shrub layer, indicated that available potassium, PPFD, soil water was the key connection between the tree- and shrub layer. The site locates in the broad-leaved Korean pine forest belonged to the old forest which could explain why the tree layer was not related to herbaceous layer in this paper. Therefore, it could be concluded that, the influence of the tree layer on the structure of herbaceous biodiversity carried out through the direct effect on light environment, precipitation and litter.Keywords:Tree layer, shrub layer, herbaceous layer, seasonal dynamic, soil attributes, light environmentAfrican Journal of Biotechnology, Vol 13(11), 1223-1230