Study on niche of dominant species of subalpine scrubland and meadow community in Guandi Mountains ON THE FLORA OF SEED PLANTS IN GUANDI MOUNTAINS,SHANXI Interspecific Relationships of Dominant Species of Sub-alpine Scrub Community and Sub-alpine Meadow Community in the Guandi Mountains THE VERTICAL BELTS OF NATURAL VEGETATION PARTITIONING OF THE GUANDI MOUNTAINS BY USING ORDERED PLOT CLUSTERING,SHANXI,NORTH CHINA