Abstract
Patterns of tree distribution are an important attribute of forest structure and directly affect the health and stability of forest ecosystems. This paper studied the effects of forest management on the forest distribution pattern of Larix kaempferi plantations with an aim to improve the quality of the spatial structure of plantations by providing scientific grounds for near-nature distribution pattern adjustment. We set up 15 long-term positioning and monitoring plots of 20 m × 20 m of L. kaempferi plantations in Xiaolongshan, Gansu Province, China, based on the Clark and Evans index, and applied the structure analysis method of the neighboring tree relationship to determine the standard angle of the uniform angle index of regularly distributed plantation forests. The changes in forest distribution patterns were compared before and after randomized management (R1 (dumbbell-shaped random unit), R2 (torch-shaped random unit) and R1:R2 = 1:2 models) and underlayer tending and unmanaged control (CK). The results showed that (1) Under different management modes, the distribution patterns obtained by the Clark and Evans index and the mean values of the uniform angle index were entirely the same; all stand patterns were evenly distributed. (2) Regardless of randomized management or underlayer tending, the number of trees in the even distribution was the largest, accounting for more than 40%. (3) The mean values of the uniform angle index of most stands increased obviously after randomized management, among which the R1 and R2 stands showed an upward trend, while the R1:R2 = 1:2 stands showed a slight decrease. However, the mean values of the uniform angle index of the stands with underlayer management showed a decreasing trend. (4) The proportion of random trees in most stands increased significantly after randomized management, increasing by 1%~19% compared with that before adjustment, while the proportion of random trees in the underlayer tending treatment decreased by 2%~10%. Our results suggest that (1) The method based on the modified uniform angle index standard angle could effectively improve the accuracy of the distribution pattern of individual trees in plantation forests and further improve the accuracy of the overall stand pattern quantitatively. (2) Randomized management significantly increased the proportion of random trees in the stands, which accelerated the evolution of the forest distribution pattern of the L. kaempferi plantation to a random distribution.
Highlights
Introduction conditions of the Creative CommonsWith the global decrease in natural forest resources, plantations play an increasingly important role in alleviating the contradiction between the supply and demand of wood, increasing forestry-related incomes and protecting the natural environment [1,2]
The stand spatial structure refers to the distribution pattern of individual trees in horizontal space and the spatial arrangement of their attributes [10], which is an important attribute of forest ecosystems
Our results showed that the mean value of the uniform angle index of the stand in the 15 plots before management ranged from 0.227 to 0.302, and the stands were uniformly distributed overall; the results were consistent with the Clark and Evans index
Summary
Introduction conditions of the Creative CommonsWith the global decrease in natural forest resources, plantations play an increasingly important role in alleviating the contradiction between the supply and demand of wood, increasing forestry-related incomes and protecting the natural environment [1,2]. The stand spatial structure refers to the distribution pattern of individual trees in horizontal space and the spatial arrangement of their attributes [10], which is an important attribute of forest ecosystems. It affects the competition among trees, their spatial ecological niche, and determines whether forest functions can be maximized [11,12]. Tree distribution patterns are an important aspect of stand spatial structure and reflect the comprehensive effects of the biological characteristics of the population itself, intraspecies and interspecific competition, and the environmental conditions of the community (such as competitiveness, soil, climate, and topography) on long temporal and spatial scales [13,14,15,16,17]. The study or adjustment of tree distribution patterns has become the basis for the study or adjustment of community spatial behavior; there are few reports on operational techniques for the adjustment of spatial patterns in plantations
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