From the text ... 'Pinyon-juniper (Pinus spp. and Juniperus spp.) vegetative type conversions have been made on millions of acres and semiarid rangeland. Chaining, which involves mechanically uprooting the trees with a large anchor chain suspended between two crawler tractors, is a frequently employed technique. In Arizona alone, almost a million acres of woodland have received some vegetation treatment between 1950 and 1960 (Dortignac, 1960). Yet many of the hydrological aspects of vegetation conversion are poorly understood. The secondary treatment effects of grazing and burning these treated areas are understood even less.'