Abstract:

Objective: Carpinus tientaiensis is an endemic tree species in China, which is only disjunctively distributed in the east and middle of Zhejiang Province. Due to the habitat fragmentation, the population of C.tientaiensis becomes smaller and isolated from each other, so it has been in a critically endangered state. The research on the natural community characteristics of C. tientaiensis and their association with environment in Tiantai County and Pan'an County of Zhejiang Province can provide a basis for scientifically and effectively restoring the population of C. tientaiensis. Method: Based on the field community and habitat survey data, the community characteristics of C. tientaiensis were quantitatively analyzed through two-way indicator species analysis (TWINSPAN) and canonical correspondence analysis (CCA). The associations of the community characteristics and species distribution pattern of C. tientaiensis in the two regions with environment were explored. Result: 24 quadrats of C. tientaiensis community were investigated in the survey regions, and a total of 46 species of vascular plants (40 genera and 29 families) were recorded. The important value of main species was subjected to TWINSPAN clustering, based on which the C. tientaiensis community was divided into 7 association types. C. tientaiensis played a dominant role in the community, and the commonly-seen associated plants in each quadrat included Indocalamus latifolius (17/24), Lindera reflexa (9/24), Symplocos paniculata (9/24), Castanea seguinii (8/24) and Crytomeria fortunei (7/24). According to the analysis of the floristic geographical elements of seed plants in the community, there were significant warm-temperate characteristics in the community, and the tropical and subtropical elements occupied a large proportion. The rationality of TWINSPAN classification result was verified by CCA ranking order. 72.66% of the association between species distribution and environmental factors could be explained through the first 3 axes of CCA, and the 7 association types had significant differentiation in terms of the environmental gradients. The first axis prominently reflected the altitudinal gradients (P < 0.01) and disturbance (P < 0.01), and the second axis reflected the change trends of slope position and slope gradients (P < 0.01). The Monte Carlo permutation test showed that the species had extremely significant correlations with the altitude, disturbance, and slope. The C. tientaiensis community was mainly distributed in the subtropical evergreen broad-leaved forest on the middle and lower mountains at an altitude of 850-1 250 m. Due to the habitat loss and fragmentation, only a few plants of C. tientaiensis were left in the association, such as Pinus taiwanensis-C. tientaiensis-Quercus glandulifera var. brevipetiolata + I. latifolius-L. reflexa association, and C. tientaiensis-Lindera erythrocarpa-Acer pubipalmatum + I. latifolius + Antenoron filiforme association. The structure of some associations became incomplete, such as C. tientaiensis+ Potentilla freyniana-Houttuynia cordata-Clinopodium gracile association composed of only tree layer and herb layer, with simple community composition and low species coverage. In Tiantai County, C. tientaiensis-Rhododendron fortune-C. polyneura + I. latifolius-Smilax glaucochina + Aster ageratoides association was distributed in areas with gentler slopes and better soil humidity, which was the largest wild community of C. tientaiensis, with a few survived wild saplings and seedlings. Conclusion: C. tientaiensis narrow distribution range, its community stability is not high, and the age structure of the population is decaying. The relationship between vegetation communities and environmental factors was reflected by CCA ordination, as altitude, slope and disturbance were the dominant environmental factors affecting the community structure and spatial distribution of C. tientaiensis, which can be used as an important basis for the restoration and enhancement of C. tientaiensis population. Relevant studies should take into account its unique habitat, it is necessary to pay close attention to the stability of original natural community and enhance the protection of the native environment and associated plants during the restoration and protection of C. tientaiensis population, so as to ensure the long-term survival of C. tientaiensis population.

Key words: Carpinus tientaiensis, community, two-way indicator species analysis (TWINSPAN), canonical correspondence analysis (CCA), environmental factors