Abstract

This study explores the elevational richness patterns of vascular and cryptogam species in the highest alpine zone in the world, the Tibet/Xizang Autonomous Region (78°25′–99°06′E, 26°50′–36°53′N). The data are based on the published flora for vascular plants, bryophytes, and lichens. Elevational ranges have been interpolated for each species recorded in the flora at altitudes between 4500 and 6000 m into 16 elevational bands of 100 m each. A species is assumed to be present at all elevational bands between its lower and upper limits as recorded in the flora. Total richness has been further subcategorized into richness of different functional groups and some dominant angiosperm families. Generalized linear models (GLMs) up to 3 orders are applied to assess the relationship between species richness and elevation and the statistically most appropriate model based on the highest F value among the significant models is selected. A total of 1585 species, 385 genera, and 111 families are recorded in the flora from this part of the alpine zone. Flowering plants are represented by 1328 species, 261 genera, and 54 families. A significant decreasing quadratic relation with increasing elevation is the most common pattern among most of the functional groups. Bryophytes, lichens, and their functional groups show a linear declining pattern except for a quadratic relation in foliose lichen richness. A significant unimodal relation is found with some angiosperm families. The patterns found are both similar and dissimilar to published results from studies using interpolation or direct observations. Scale, environmental heterogeneities, stress, disturbance, and tolerance by individual species are the likely causes for these patterns.

Highlights

  • Alpine life and its biodiversity are of considerable international interest (Korner 2003; Nagy and Grabherr 2009)

  • A total of 1585 species from 385 genera and 111 families were represented in the flora in the 4500–6000-m elevation range of the Tibet/Xizang Autonomous Region (TAR)’s alpine zone

  • One possible reason for these different elevational patterns among biological groups could be the differential adaptational features of individual species in the face of the very harsh and strong environmental filters in the alpine zone (Agakhanyantz and Breckle 1995; Klimes 2003; Korner 2003), which almost certainly apply to alpine species in the TAR

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Summary

Introduction

Alpine life and its biodiversity are of considerable international interest (Korner 2003; Nagy and Grabherr 2009). Survival in an alpine zone involves adaptation to severe cold and a short growing season. It is a habitat where many new species are yet to be discovered and described, and where a greater rate of speciation may take place due to long-term isolation, which is generally believed to increase with increasing elevation (Kluge et al 2006). Studies of species richness at high elevations and high latitudes are comparatively less common than elsewhere (Korner 2003), partly because these areas are difficult to access and generally have a low number of species

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