Abstract:

In grassland， dominant species make a major contribution to aboveground biomass. A large number of studies have shown that biomass of dominant species is regulated both by environmental factors and by interspecific relationships among coexisting species. However， our current understanding about relationships between biomass of dominant species and environmental factors remains incomplete for many species and environmental conditions. To address this knowledge gap， this study investigated relative biomass （RB） of dominant species among 9 grassland types across 397 sites in Xinjiang grassland during 2011-2013. Firstly， we evaluated community composition for each grassland type and identified dominant species. Secondly， we explored relationships between RB of dominant species and elevation as well as linkage of RB among coexising dominant species using a general linear model. Our results showed that： 1） A total of 169 dominant species， which belong to 120 genera and 31 families， were identified in Xinjiang grasslands， with 19.53% of dominant species belonging to the Poaceae. In particular， Stipa capillata was the most important dominant species for alpine steppe， temperate meadow steppe， temperate steppe desert， temperate steppe and temperate desert steppe， while Polygonum viviparum， Achillea millefolium， and Ceratocarpus arenarius were the most important dominant species for alpine meadow， mountain meadow and temperate desert， respectively. 2） Relationships between RB of dominant species and elevation could be classified into the following five groups： no significant relationship， a U pattern （decreased initially and then increased with increasing elevation）， a significant positive relationship， a significant negative relationship and an arch-shaped pattern （increased initially and then decreased）. These five behavioral groups comprised， respectively， 50 （64.9%）， 9 （11.7%）， 8 （10.4%）， 6 （7.8%） and 4 （5.2%） of dominant species. 3） A total of 19 significant paired relationships were found involving 24 dominant species coexisting with another species. Most coexisting dominant species pairs were negatively correlated with each other in terms of their RB. These findings demonstrated that previous results indicating a varied relationship between biomass of dominant species and elevation were not conflicting. Rather different patterns concurrently exist in Xinjiang grassland driven by variation between sites in species behavior. Our findings highlight the importance of dominant species and interspecific relationships among coexisting dominant species in biomass conservation and management in Xinjiang grasslands.

Key words: dominant species, aboveground biomass, elevation, coexisting species, Xinjiang grasslands