JOURNAL OF NANJING FORESTRY UNIVERSITY ›› 2023, Vol. 47 ›› Issue (4): 166-174.doi: 10.12302/j.issn.1000-2006.202108025

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Evaluating influences of diameter classes on the species diversity of natural forests in the Nanpan River basin

LI Minghui(), LI Yuanfa()   

  1. College of Forestry, Guangxi Key Laboratory of Forest Ecology and Conservation, Guangxi University, Nanning 530004, China
  • Received:2021-08-12 Revised:2021-11-19 Online:2023-07-30 Published:2023-07-20

Abstract:

【Objective】Species diversity and tree size play an important role in maintaining the stability and complexity of forest ecosystems, and also characterize the diversity of forest ecosystems. The relationship between species diversity and tree size is not well understood. 【Method】Three fixed plots (30-year-old forest, 30-YF; 57-year-old forest, 50-YF; 200-year-old forest, 200-YF) located at Guangxi Yachang orchid national reserve were established and their diameter distributions were divided using diameter classes of 2, 3, 4 and 5 cm. The number of individuals (N), species richness (RS), diversity (Simpson, D; Brillouin, BH), and evenness (Pielou, EH; Sheldon, ES) were calculated for each diameter class. 【Result】(1) N and RS displayed a reversed J shape, decreasing with the increase in diameter. N and RS increased with increasing diameter class, and their curves became more bent. (2) D and BH were slightly affected by diameter class and showed a linear decrease (P >0.05). (3) Overall, increasing tree diameter promoted a balance of abundance among tree populations. With an increase in diameter, EH fluctuated and ES increased linearly and was slightly affected by the diameter classes (P >0.05). (4) A significant difference in species diversity indices was found among the three stands (P<0.05) when the diameter class was 2 cm. 【Conclusion】 Diameter class had little effect on species diversity within the same stand. However, stand age enhanced this effect, highlighting the importance of the diameter range and small trees on species diversity. The diameter of 2 cm better reflects the diversity of species among natural forests in the Nanpan River basin than the other diameter classes. This justifies its widespread use.

Key words: natural forest, tree sizes, diameter class, richness, abundance, species evenness

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