Effects of different management methods on growth and plant diversity in mature Pinus tabuliformis plantations

Objective This paper aims to explore a management method that takes into account the cultivation of large-diameter tree and ecological benefits based on the mature Pinus tabuliformis plantation, as well as to provide a reference for mature plantation management in China.

Method Taking 47- and 56-year-old P. tabuliformis plantations in Wangyedian Experimental Forest Farm in Chifeng City, Inner Mongolia of northern China as the research object, the data of sample plots under close-to-nature management (CTNM), conventional management (CM) and no human intervention (NHI) were collected in 2013 and 2019. Two-factor variance analysis was used to compare the effects of three management methods on mean DBH growth rate, mortality, seedling regeneration and diversity of trees, shrubs and herbs.

Result There were significant differences in mean DBH growth rate and 6-year mortality of mature P. tabuliformis plantations under three management methods (P < 0.05), CTNM was 0.40 cm/year and 0.51%, respectively, CM was 0.36 cm/year and 1.44%, and NHI was 0.31 cm/year and 3.55%. Over a span of 6 years, the number of understory plants species under CTNM increased by 3, while CM and NHI decreased by 5 and 9 species respectively. The increase of Shannon-Wiener index and Simpson index of trees in 47- and 56-year-old stands in 6 years was CTNM > CM > NHI, while the decrease of tree seedling mortality and the Shannon-Wiener index and Simpson index of herbs in 47-year-old stands was CM < CTNM < NHI. The effects on tree growth, mortality and plant diversity under three management methods disappeared over time. The mean DBH growth rate, Shannon-Wiener indices and Simpson index of trees and shrubs in 56-year-old stands were higher than those in 47-year-old stands under three management methods. However, the Shannon-Wiener and Simpson indices of herbs were higher in the 47-year-old stands compared to the 56-year-old stands.

Conclusion Forest management can increase the mean DBH growth rate, reduce the tree mortality and delay the decline of plant diversity of mature P. tabuliformis plantations, suggesting that mature plantation should be managed regularly to improve the economic and ecological benefits. Compared with CM and NHI, CTNM is the best to maintain the plant diversity of mature P. tabuliformis plantation as well as to cultivate large-diameter tree.