Natural distribution and community ecological characteristics of Taxus chinensis var. mairei in Shanxi Province, China.

Abstract

Taxus chinensis var. mairei is a national Category 1 protective species in China, with its northernmost natural distribution to the southeast of Shanxi Province, China. This study was conducted to investigate the natural distribution of T. chinensis var. mairei in Shanxi Province. The community classification, species diversity, population structure and competition intensity of T. chinensis var. mairei were studied. The results showed that T. chinensis var. mairei mainly formed four community types, including the community of T. chinensis var. mairei + Carpinus turczaninowii, the community of T. chinensis var. mairei - Vitex negundo var. heterophylla, the community T. chinensis var. mairei - Clerodendrum trichotomum and the community of T. chinensis var. mairei + Quercus variabilis. T. chinensis var. mairei was concentratedly distributed in Mohe of Linchuan County and Manghe Nature Reserve of Yangcheng County, and scattered in some other areas. The communities had an obviously vertical structure, with T. chinensis var. mairei trees growing into main canopy which were about 8-10 m high in mixed forests and 5-6 m high in pure forests. The species diversity index and evenness index had significant difference among the four community types. The average height of T. chinensis var. mairei was 5.16 m. The individuals in tree layer and succession layer were 43.4% and 56.6%, respectively, while they were scarce in the regeneration layer. 67.6% of the trees were small-diameter (DBH＜16 cm) and only 4.0% were large-diameter (32 cm≤DBH＜40 cm). T. chinensis var. mairei was considered to be lack of seedlings because only 4 seedlings were found, which might result in the declination of this species in future. T. chinensis var. mairei in Shanxi Province showed relatively concentrated distribution, with most individuals being small-diameter, resulting in tense intraspecific competition which accounted for 61.8% of the total intensity. The interspecific competition to T. chinensis var. mairei was mainly from C. turczaninowii and Q. variabilis, which were two dominant tree species with larger population in this area.