Abstract:

Objective: Understanding of the habitat quality of Hainan gibbons (Nomascus hainanus) is crucial to its population conservation. Therefore, this study aims to compare the differences in stand structure, plant species composition and diversity between the current habitat of Hainan gibbons in the natural forest and the potential habitat in the pine forest at the same altitude, and to explore the differences in habitat quality between the two types of habitats, which could help to scientifically evaluate the restoration status of pine forest and finally lay a theoretical foundation for the ecological space expansion of Hainan gibbons. Method: The existing natural forest habitat of gibbons and the potential habitat of pine forest in the Bawangling area of Hainan tropical rainforest national park at an altitude of 400-800 m were targeted. Based on the CTFS (center for tropical forest science) plot construction standard, a total of 59 plots with each area of 400 m² were set in the two habitats. The diversity characteristics and differences of stand structure, forest plants and gibbons’ edible plants in the two types of habitats were investigated and analyzed. Result: A total of 450 plant species in 93 families and 259 genera were found in the current natural forest habitats, including 86 edible plant species of 43 families and 70 genera which were mainly composed of Rubiaceae taxa. Whereas a total of 301 plant species in 74 families, and 186 genera were found in the pine forest, including 60 species of edible plants in 29 families, and 46 genera, with Camellia species being dominant. The stand structure factors of forest community plants in the natural forest habitats, such as the mean DBH (6.30 cm±5.90 cm), the mean tree height (6.02±4.92 m), mean crown area (5.21±12.52 m2), mean crown thickness (2.10±1.65 m), and plant density (6 136±1 930 plants·hm^?2), were all greater than those in the pine forest potential habitats (mean DBH 5.19±4.19 cm, mean tree height 5.04±3.38 m, mean crown area 2.87±7.75 m2, mean canopy thickness 1.99±1.62 m, and plant density 5 517±1 901 plants·hm^?2). With the increase in diameter class and tree height, the tree density in the pine forest reduced more significantly than that in the natural forest. At the overall scale, the Shannon-Wiener index and richness index of forest community plant species in the natural forest habitat were the highest (H'=4.37, S=452). The Shannon-Wiener index and richness index of large edible plant species in the pine forest potential habitat was the lowest ( H'=4.37, S=452), while the evenness index was the highest (E=0.83). At the scale of 20 m×20 m plot, the plant species richness index of natural forest habitat was significantly higher than that of the pine forest potential habitat (Forest community plants: t=4.72, P=0.02; Edible plants: t=4.61, P=0.01; Small edible plants: t=2.03, P=0.02), while the Shannon-Wiener index and richness index of large edible plants of the pine forest potential habitats were extremely significantly lower than those of the natural forest habitats (Shannon-Wiener index: t=5.03, P<0.001; richness index:t=4.58, P<0.001). The similarity of the community plants between the two habitats was the highest at the family level (C_J=0.76). At the species level, the similarity of small edible plants was the highest ( C_J=0.67), while that of large edible plants was the lowest ( C_J=0.31). The order of the difference in plant beta diversity between the two habitats was large edible plants ( F=1.64, P<01) > forest community plants (F=48.10, P<0.001) > edible plants (F=7.72, P=0.01) > small edible plants ( F=7.72, P=0.01). Conclusion: Compared with the natural forest habitat, the pine forest potential habitat does not only lack large broad-leaved trees and also large edible plants which are suitable for Hainan gibbons to inhabit, but the plant species diversity is also significantly lower than the natural forest habitats. Thus, the survival needs of Hainan gibbons could not be met in the pine forest habitats for the time being. Nevertheless, the species composition and diversity of small edible plants in the pine forest potential habitats are similar to that of the natural forest habitats, which shows that there is potential for the pine forest potential habitats to be developed into Hainan gibbons’ habitat. While large edible plants are the key ecological species for the current restoration of the pine forest's potential habitats.

Key words: Nomascus hainanus, pine forest, stand structure, plant species diversity, edible plant, habitat