Abundance of Oedaleus asiaticus in natural grassland in the upper reaches of Heihe River,western China in relation to topography
The micro-scale environmental heterogeneity caused by topographical diversity is an environmental foundation underlying the formation and evolution of bio-geographic pattern. Based on the field survey in July-August 2009, and with the help of GIS and S-PLUS software, a quan-titative analysis with generalized additive model (GAM) was made on the relationships between the Oedaleus asiaticus abundance and topographical factors such as altitude, aspect, slope, and profile curvature in the natural grassland on northern slope of Qilian Mountains, the upper rea-ches of Heihe River. The model for O. asiaticus performed well, and could actually reflect the spatial distribution of 0. asiaticus abundance. Different topographical factors had different effects on the spatial distribution of 0. asiaticus abundance, among which, elevation and profile curva-ture showed dominant effects. With the increase of elevation, the O. asiaticus abundance showed a more or less reverse "V" trend. The abundance had a positive correlation with increasing alti-tude at altitude 2380-2560 m, but a negative correlation with the increasing altitude at altitude >2560 m. The 0. asiaticus was mainly distributed in the regions with a profile curvature <0. There existed a positive correlation between the abundance and profile curvature when the profile curvature was <-l. 6, and a negative correlation when the profile curvature was >-1. 6. The relationships between the abundance of 0. asiaticus and topographical factors as well as the spatial distribution pattern of 0. asiaticus abundance indicated that the redistribution of water and heat conditions due to topographical factors caused the heterogeneity of the spatial distributionpattern of 0. asiaticus.
Oedaleus asiaticusgeneralized additive model (GAM)abundancetopographical factorspatial patternQilian Mountains