Anthropogenic burning of big sagebrush Artemisia tridentata habitats may have positive or negative outcomes.Poorly planned burning and subsequent inappropriate livestock grazing regimes has resulted in serious vegetation and soil deterioration. Prescribed burns followed by good grazing practice may conversely result in improved range condition with enhanced forage availability for both livestock and wildlife. In this study, long-term vegetation changes following summer burning of sagebrush-grass range on the Snake River Plains near Dubois, Idaho (central USA) was assessed.
Prior to burning, a grid of 400, 100 ft² (9.3 m²) plots were established. In August 1936, 640 acres (259 ha) were burned, and the area was ungrazed by livestock for one year. Subsequently, sheep grazed in spring and autumn (at about 2 acres/sheep month).
Plots were divided into unburned, lightly, moderately or heavily burned. Herbage production was estimated by species (samples collected dried and weighed) before the burn in 1936, and in 1937, 1939, 1948 and 1966. Big sagebrush plants were counted in 1948 and 1966.
Burning initially reduced average densities of sagebrush but overtime it recovered (1948: unburned 25.7/plot, burned 3.7; 1966: unburned 41.0, burned 34.3). However, a higher proportion of younger plants in the burned plots indicated that the climax Artemesia community had not yet been reached on the burned plots by 1966. Following burning, sagebrush yields also increased and sagebrush was able to reinvade vigorous grass stands that became dominant following burning.
Concurrently, as sagebrush recovered, by 1966 after showing initial increases, other main shrubs (rabbitbrush Chrysothamnus viscidiflorus and horsebrush Tetradymia canescens), and grasses (thickspike wheatgrass Agropyron dasystachyum, plainsreedgrass Calamagrostis montanensis, bluebunch wheatgrass Agropyron spicatum, Idaho fescue Festuca idahoensis, bluegrasses Poa secunda and P.nevadensis) and forb species decreased. Total grass yields (1948: unburned 212 lb/acre, burned 364; 1966: unburned 68, burned 73) and total forb yields (1948: unburned 96 lb/acre, burned 144; 1966: unburned, burned) were higher in 1948 on the burned than on the unburned plots, but production of both had declined significantly by 1966.
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