Abstract
Subtropical natural forests are unique due to their ecological and economic functions. However, most of these forests are highly degraded, which impairs the ability to provide ecological and economic benefits. Enrichment planting is an important approach to restore natural degraded forests. Species arrangement is of great importance to inform enrichment planting. Species association refers to the interrelationship of different species occupying a habitat and is a static description of the organic connection formed by the interaction of species. Species association, therefore, provides a scientific basis for species arrangement in enrichment planting. Additionally, because an old-growth forest is a climax community that has attained great age without significant disturbance, the species association in an old-growth forest can provide valuable information on the reference conditions for forest management. In this study, the species association between dominant tree species (including saplings and adult trees) was investigated in an old-growth forest in the Gutianshan National Nature Reserve in Zhejiang province in subtropical China. The objective of the study was to inform species arrangement for enrichment planting. The result showed that the overall species association exhibited a significant net positive association, indicating a dynamic balance of stable structure and species composition in the old-growth forest. Additionally, the pairwise species association was examined using the χ2 test, the Dice index, and Spearman’s rank correlation coefficient; significant positive and negative pairwise species associations were detected. Based on the species association and the light requirements of the tree species, an optimal species arrangement was determined to support enrichment planting for restoring natural degraded forests. It is expected that the results of this study will contribute to the restoration of natural degraded forests in subtropical China.
Highlights
China has 84.91 million ha of subtropical natural forests with a total volume of 66.79 hundred million m3 [1]
For each dominant tree species, we grouped the trees into 5-cm diameter classes to determine the distribution (Figure 2)
The tree species with diameter at breast height (DBH) larger than 50 cm included C. eyrei (62.0 cm), S. superba (55.9 cm), M. thunbergii (53.0 cm), and C. tibetana (51.8 cm), though the individual trees in the DBH class larger than 50 cm are not visible in Figure 2 due to their small number
Summary
China has 84.91 million ha of subtropical natural forests with a total volume of 66.79 hundred million m3 [1]. Subtropical natural forests have unique ecological functions related to soil and water conservation, biodiversity conservation, and water and air purification, e.g., high biodiversity, complex structure, and high productivity [2,3,4]. The total stand volume of subtropical natural forests in Zhejiang province is only 54.87 m3 per hectare [1]. Many authors documented that natural degraded forests exhibit poor performance in terms of carbon sequestration, biodiversity conservation, and water conservation [7,8,9]. Subtropical natural degraded forests do not meet the increasing demand for ecological and economic benefits [5,13,14]
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