Zhonghua Zhao

Large trees are surrounded by more heterospecific neighboring trees in Korean pine broad-leaved natural forests.

Negative conspecific density dependence is one of the principal mechanisms affecting plant performance and community spatial patterns. Although many studies identified the prevalence of density dependent effects in various vegetation types by analyzing conspecific spatial dispersal patterns (spatial patterning) of forest trees, interactions between individuals and heterospecific neighboring trees caused by density-dependent effects are often neglected. The effects of negative density dependence lead us to expect that neighbourhood species segregation would increase with increasing tree size and that larger trees would be surrounded by more heterospecific neighbours than would smaller trees. We studied four mapped 1-Ha plots on Changbaishan Mountain in North-eastern China and used marked point pattern analysis to explore whether trees of different sizes exhibited differences in neighbourhood species segregation; we also determined whether larger trees were more likely to have heterospecific neighbours than smaller trees were. Our results show that bigger trees generally have higher species mingling levels. Neighborhood species segregation ranged from lower than expected levels to random or nearly random patterns at small scales as tree size classes increased under heterogeneous Poisson null model tests. This study provides some evidence in support of negative density dependent effects in temperate forests.

Spatial structural characteristics of forests dominated by Pinus tabulaeformis Carr.

The Chinese pine (Pinus tabulaeformis Carr.) is an ecologically and economically important evergreen coniferous tree which dominates warm temperate forests throughout northern China. We established two permanent plots within the Chinese pine forest in the Jiulong Mountains, Beijing, China. To understand the structural characteristics and dynamics of these plots, we analyzed the spatial structural characteristics within nearest-neighbor relationships using the bivariate distributions of the stand spatial structural parameters: uniform angle index, W; mingling index, M; dominance index, U; and crowding index, C. Results revealed that most trees in the forest were randomly distributed. The predominant individuals and randomly arranged trees were in very dense areas and surrounded by the same species. In addition, both plots exhibited a uniform size differentiation pattern. The two plots differed mainly in the level of species mixture and dominance. The majority of reference trees in the pure Chinese pine forest (plot 1) exhibited poor species mingling and low dominance, whereas trees in the mixed Chinese pine forest (plot 2) were evenly distributed in each mingling class and most trees were of intermediate dominance. The study results are useful for optimizing forest management activities in the studied stands, promoting tree growth, regeneration and habitat diversity, and improving forest quality at a fine scale.

Composition of basal area in natural forests based on the uniform angle index

Abstract This study presents an analysis of the small scale spatial patterns in natural forest plots in different parts of China. The focus of the analysis is to assess the spatial characteristics of different natural forests at a high level of resolution. The results may provide a theoretical basis for nature-approximating forest management practices in plantations established with a regular arrangement of planting points. Method Using a new measure for describing small scale forest structures, known as the Uniform Angle Index, it was possible to identify local structure units as even, random, or clustered. We analysed 11 selected natural forest plots with mapped trees with a wide geographical distribution in different regions of China. In each plot, with a known basal area density, the proportion of the total basal area was assessed that can be assigned to local structure units with specific patterns. Specifically, the basal area of each tree, and the associated local spatial pattern in the vicinity of that tree, provided the information about the distribution of local spatial patterns in the 11 natural forests. Results (1) Most trees were distributed in neighbourhoods with a random structure, regardless of whether the entire forest pattern was classified as even, random, or clustered. Less than half of the tree neighbourhoods were either clustered or evenly structured. (2) More than 50% of the basal area of the reference trees consisted of random units in all 11 natural forests. (3) Similarly, the basal areas of the random structure units occupied more than half of the total basal area. Conclusions Our findings suggest that the major part of the basal area natural forests consists of random structure units. This observation may be helpful in the design of planting patterns or harvesting schedules to improve the stability of planted monocultures.