Spatial distribution pattern of Arceuthobium sichuanense and its correlation with environment in Xianmi forest region of Qinghai, northwestern China.

Our research focused on Arceuthobium sichuanense and its host in Xianmi forest region, Qinghai of northwestern China, and transect survey method was chosen to investigate the typical sub-compartment. By analyzing the disease incidence, it was found that the hazard of A. sichuanense in the sub-compartment gradually increased from foot to the top of hill. Then all crown-third DMR(dwarf mistletoe rating)distribution of the host was counted in transect, it was figured out that A. sichuanense preferred to distribute from lower to the upper crown of the host. Forty standard samples were set in Xianmi forest region, taking DMI(dwarf mistletoe idex), mean DBH, mean height, stand type, mingle index, herb cover, moss depth as response variables, taking canopy density, slope, elevation as environmental factors. It was ascertained that crown density, slope, slope position, elevation and stand type were main factors which had an effect on the outbreak of A. sichuanense by using RDA analysis, in which the canopy density had a significantly negative correlation with the incidence of dwarf mistletoe; the slope and elevation had a significantly positive correlation with the incidence of dwarf mistletoe; the stand composition had an effect on the occurrence of dwarf mistletoe, and the dwarf mistletoe was less harmfulin the higher mingling forest.