Effects of Replanting Broad-leaved Trees in Pinus elliottii forest on Canopy Structure and Diversity

In order to explore the variation characteristics of canopy structure and understory species diversity after thinning and replanting broad-leaved trees in Pinus elliottii plantation, in 2021, the Pinus elliottii pure forest planted in Taihe County of Jiangxi Province in 1985, felled in 2012, and replanted different broad-leaved trees under the Pinus elliottii forest in 2013:Pinus elliottii + Michelia macclurei + Schima superba (S₆), (Pinus elliottii + Schima superba + Michelia macclurei (S₅), Pinus elliottii + Castanopsis eyrei + Castanopsis fargesii (S₇), Pinus elliottii + Michelia macclurei + Choerospondias axillaris (S₁₀) and control without replanting (S₁₁) for research object, the effects of thinning and broad-leaved tending measures on stand structure and species diversity of Pinus elliottii forest were studied by using canopy analyzer and fisheye camera to collect data and images, combined with plot survey.The results showed that the DBH, individual volume and volume of Pinus elliottii were significantly higher than those of the control after thinning and replanting broad-leaved trees, and the DBH, individual volume and volume of S₁₀ mode were the highest.The canopy openness of S₅ was 31.70, and the fixed-point factors were 32.09, 34.63 and 33.17, all of which were the highest.The leaf area index of S₇ was the highest, and there was no significant difference with the control.Most of the canopy structure parameters were significantly correlated, and the leaf area index showed a negative correlation with other parameters.The species diversity under the forest increased, the Simpson index and Shannon index of the shrub layer were higher than those of the control, and the shrub layer was higher than the herb layer.The evenness indexes of shrub layer and herb layer was the highest in S₆ and S₇.The comprehensive results show that Michelia macclurei and Choerospondias axillaris are better tree species for replanting broad-leaved trees after thinning of Pinus elliottii forest.