Study on the stand structure and soil physicochemical properties of artificial mixed forests of Pinus elliottii and Liriodendron chinense in the rocky desertification area of Western Hunan

Abstract

To explore the forest structure and soil physicochemical properties of the artificial mixed forest of Pinus elliottii and Liriodendron chinense in the rocky desertification area of Western Hunan, taking Pinus elliottii and Liriodendron chinense artificial coniferous and broad-leaved mixed forest in the rocky desertification area of Western Hunan as the research object, this paper provides a theoretical basis for vegetation restoration, plantation structure optimization, and soil improvement in this area. The stand structure and soil physicochemical properties of existing stands were analyzed using plant community analysis and field sampling detection methods. Winklemass 1.0 was used to calculate the spatial structure parameters of the stands, and three-dimensional discrete random variables were used to analyze the spatial distribution pattern of dominant species. The results were as follows: (1) A total of trees of 897 plants·hm-2 with diameter at breast height (DBH) ≥ 2 cm in the stand, belonging to 15 families and 16 genera. The main forest layer was Pinus elliottii, with an average DBH of 32.3 cm and an important value of 44.2%; the secondary forest layer was the broad-leaved tree, with the majority of young and middle-aged trees. Cinnamomum camphora and Liriodendron chinense were the dominant species, with important values of 17.1% and 13.2%, respectively. In addition, there were many natural regeneration species at the disadvantaged ecological niche. (2) The horizontal distribution pattern of trees tended to be random (W-=0.503); the overall trend of forest stands tended to transition towards mediocrity and disadvantage (U-=0.505); the degree of interspecific isolation was relatively high (M-=0.689), and the mixed forest was in good condition. Three-dimensional discrete random variables of spatial structure parameters showed that 87.3% of Pinus elliottii was dominant and sub-dominant, 41.7% of Liriodendron chinense was sub-dominant, 26.9% was moderate, 23.5% of Cinnamomum camphora was moderate, 56.8% was inferior and absolute inferior. (3) The pH value of forest soil tended to be neutral; compared with abandoned land, the bulk density, water capacity, porosity, organic carbon, total potassium, total nitrogen, and total phosphorus of the forest soil had significantly improved. However, the forest soil was still relatively barren, with local soil compaction and poor water retention ability. To sum up, after 43 years of growth of Pinus elliottii and Liriodendron chinense as pioneer species, the stand has a trend of succession to the uneven-aged forest and intensive mixed forest. However, the number of young and middle-aged broad-leaved trees in the forest is relatively large, and faults appear in the near mature forest. The elderly coniferous trees occupy the dominant ecological location. Needles need to be drawn to supplement the broad-leaved trees, interspersed to cultivate the broad-leaved trees, and selective felling the inferior trees, to promote the structural succession of the forest with mainly sunny broad-leaved trees, followed by mesophytic and shade-tolerant broad-leaved trees. The results of this study provide a theoretical basis for vegetation restoration, plantation structure optimization and soil improvement in the rocky desertification area of Western Hunan.

Keywords

• rocky desertification
• artificial mixed forest of pinus elliottii and liriodendron chinense
• stand composition
• stand spatial structure
• physical and chemical properties of soil