Abstract: Heterogeneity of plant population response to soil moisture is the environmental basis of their pattern’s formation and evolution. According to the pattern of soil water decreasing gradually from the wetland center to the edge, we set up five sampling plots to study the spatial distribution and spatial association of Kobresia tibetica and K. humilis under different soil moistures in north Qilian Mountain by using the point pattern analysis. The results showed that with the decrease of alpine wetland moisture content, the coverage, plant height and aboveground biomass of K. tibetica population were continuously increased, while the main biological features of K. humilis increased firstly then reduced. The distribution pattern of K. tibetica was clumped—regular—clumped and that of K. humilis gradually shifted from aggregation to regularity at small scale. Along with the decrease of soil moisture, the spatial association between K. tibetica and K. humilis population at small scale was positively correlated, then changed into no significant correlation and negative correlation finally. In the alpine wetland, the main biological features and spatial pattern of K. tibetica and K. humilis populations showed regular changes, which reflected the adaptability of the two species in response to habitat heterogeneity under different soil moistures.

Key words: completely autotrophic nitrogen removal over nitrite (CANON), denitrification, tidal flow constructed wetland (TFCW), COD/TN (C/N), anammox