Shrub and herb flora and vertical distribution patterns in Shangri-La, China

As the most important components of global ecosystem functional services, grasslands are the basis for the development of agriculture, forestry, and animal husbandry; thus, a study of the characteristics of shrub and herb flora and geographical distribution is of great value, in particular to reveal regional species diversity and conservation strategies. In this study, the diversity, floristic characteristics, and vertical distribution patterns of shrubs and herbaceous (including graminoid) plants in Shangri-La were systematically analyzed with the use of field surveys and historical records database and applying the Wu Zhengyi flora zoning method. The results show that 1) the region is rich in shrub and herb (including graminoid) species, with 121 families, 619 genera and 2 442 species, and most of this richness can be attributed to herbs, with 94 families, 514 genera and 2 048 species. 2) In the composition of families and genera, the dominant families and genera were obvious, and the proportion of single species families and oligospecific genera was high, accounting for 32.23% and 51.05%, respectively, of the community composition. As well, the surveyed areas are extremely rich in endemic Chinese genera (28). 3) The regional components are diverse, containing 13 families and 15 genera of geographical distribution types. The distribution types of the family are mainly world distribution, pantropical distribution, and north temperate distribution. The ratio value of the tropical distribution and the temperate distribution is 1.29, which indicates that the tropical distribution type is slightly dominant. The distribution types of the genera are mainly north temperate distribution, East Asian distribution and pantropical distribution, and the ratio value of tropical distribution and the temperate distribution is 0.39, which indicates that the temperate distribution type is dominant. 4) In terms of vertical distribution, with the increase in elevation, the proportion of tropical zone components gradually decreases and temperate zone components gradually increase, and the species richness shows a single-peak distribution pattern of rising and then decreasing, with the peak of shrub and herb species richness located at 2 600 ~ 2 900 m and 3 200 ~ 3 500 m, respectively, and the number of herbaceous plants is more than that of shrubs in each altitude section (P < 0.01). With this study we have produced an altitudinal inventory of plant diversity and zone characteristics in the central area of the Three Parallel Rivers World Natural Heritage Site. This altitudinal inventory is expected to be a valuable reference for the selection and rational use of species for ecological restoration of regional shrublands and herbaceous vegetation.