The impact of ?available area? onArtemisia tridentata seedling dynamics

Abstract

Seedling survival ofArtemisia tridentata ssp.tridentata (basin big sagebrush) was studied during 1984 and 1986 on a semi-arid rangeland in central Utah, USA. Seedlings were mapped in ungrazed pastures and observed on a 10 day interval for survival. Available resource area around individual seedlings was calculated using Theissen polygons. Over 90% of the naturally-occurring seedlings occurred in polygons of 150 mm2 or less. Seedlings with available areas greater than 300 mm2 were more likely to survive than seedlings with less resource area. Differences in overall seedling survival in different study sites were noted. Survival was similar for all seedlings with less than 50 mm2 available area. In 1986, precipitation and seedling survival were considerably lower than in 1984. Even in 1986, however, seedling survival in polygons greater than 300 mm2 was always higher than for seedlings in smaller polygons. Survival patterns over each growing season closely followed the precipitation patterns.