INTERSPECIFIC RELATIONSHIP ANALYSIS OF DESERT RIPARIAN FOREST PLANT COMMUNITIES IN THE MIDDLE AND LOWER REACHES OF THE TARIM RIVER Disturbance regimes and gaps characteristics of the desert riparian forest at the middle reaches of Tarim River Seedling recruitment in desert riparian forest following river flooding in the middle reaches of the Tarim River Response of the Species Diversity of Desert Riparian Forest to the Changes of Groundwater Depth in Middle Reaches of Tarim River Sap Flow of Populus euphratica in a Desert Riparian Forest in an Extreme Arid Region During the Growing Season