Abstract:

Spruce forest is a typical alpine forest type near timberline in the eastern Tibetan Plateau. However, little is known about this ecosystem. In the present study we investigated community structure and vascular plant composition of such forests in northern Zamtang County, Sichuan Province, China. We sampled six plots (40 m×50 m) in primary forests in a range of 3,700-3,800 m elevation. For all trees ≥ 3 m in height in each plot, height and diameter at 50 cm height were measured. A total of 180 subplots (1 m×1 m), 30 for each plot, were sampled to estimate the coverage of shrubs, herbs and bryophytes, and species composition of shrubs and herbs. Four sub-layers could be recognized within the canopy, suggesting that the forest is uneven-aged and multi-storied. Structure analysis of tree height and diameter showed that the arborous layer was stable and maintained a certain regenerative ability. Shrubs showed a patchy spatial pattern with simple structure and low richness. Compared to low coverage (15.4±20.9%) of shrubs, coverage of herbs and bryophytes (49.4±21.9% and 36.6±21.2%, respectively) were higher, forming obvious herb and bryophyte layers. A total of 124 vascular species (109 herbs and 15 shrubs) were recorded in all six plots, belonging to 68 genera and 30 families. Temperate areal-type genera and hemicryptophyte species were dominant. We concluded that the forest was a moss-spruce forest type. Although the species composition and richness were quite similar to other forests in Tibetan Plateau, community structure differed significantly. Our results provide insights into management and biodiversity conservation in forests near the timberline in the eastern Tibetan Plateau.

Key words: spruce forest, timberline, community structure, eastern Tibetan Plateau, primary forest, species composition