Basin and Wyoming big sagebrush plants growing in contiguous populations were studied to identify potential habitat differences in plant water and soil relationships. At 3 study sites, basin big sagebrush plants were growing in and adjacent to a drainage, while Wyoming big sagebrush plants occupied areas adjacent to the basin big sagebrush populations. Soil-and leaf-water potentials and leaf-transpiration resistances were measured from May to October 1980 to identify differences between basin and Wyoming big sagebrush plant-water relationships. Soil identification and plant tissue analyses were conducted to help characterize edaphic differences between the subspecies. The results of these studies showed that basin big sagebrush plants grew in a more mesic and fertile habitat than did Wyoming big sagebrush plants. Understanding the environmental differences of these two big sagebrush subspecies is important in effectively managing basin and Wyoming big sagebrush ranges. The woody sagebrushes (subgenus tridentatae (Rhdb.) E.D. McArthur of Artemisia L.) occur naturally only in western North America, ranging from southern Canada to northern Mexico (Beetle 1960, McArthur et al. I98 I). The most common, important, and widely distributed species is big sagebrush (Artemisia tridentata Nutt.). Big sagebrush plants are common on about 58,655,OOO hectares from the arid lands of the Great Basin to the moist, cool areas of mountain ranges (Beetle 1960, Hall and Clements 1923, McArthur 1979, Winward 1970). Considering the wide distribution of big sagebrush, it is not surprising to find genotypic variation among A. tridentata populations (Caldwell 1979). Presently, the big sagebrush complex consists of 3 subspecies with 2 forms (Beetle 1960, Beetle and Young Authors are range ecologist,

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Genotypic and phenotypic variations are characteristic among big sagebrush (Artemisia tridentata) plants. One obvious expression is the variability of big sagebrush plant stature along soilwater gradients. Large phmts are usually associated with mesic habitats such as drainages or swales, while small plants occupy the xeric portions of the gradients. The purpose of this study was to investigate the genetic influence on big sagebrush plant stature along soil-water gradients. Leaf morphological, phenological, chromatographical, and cytological investigations evaluated potential genetic differences and examined possible subspecies status of the huge and small plants. The results of these studies revealed a genetic difference between the large and small plants and confirmed subspecies status. The large plants were identified as basin big sagebrush (A. tridentata spp. tridentata) while the small plants were Wyoming big sagebrush (A. tridentata spp. wyomingensis). Three additional studies examined nossible differences in arowth Genotypic and phenotypic variation is characteristic of big sagebrush (Beetle 1960, Hanks et al. 1973, McArthur et al. 1981, West et al. 1978). An obvious expression is the variability in big sagebrush plant stature along soil-water gradients (Beetle 1960, Hall and Clements 1923, Hanks et al. 1973). Large plants may reach a height of 3.5 to 5.0 m in mesic habitats such as drainages or swales, while plants less than 1 .O m tall are associated with the xeric portions of moisture gradients. Considering the differences in big sagebrush plant stature, a logical question arises: Are the differences in plant stature due to genetic or environmental influences? The research herein discusses the influence of genetics on big sagebrush plant stature. Edaphic differences associated with the large and small big sagebrush plants are reported elsewhere (Barker 198 I, Barker and McKell 1983). Study Sites potential between the subspecies.'A greenhouse and &form _ garden study compared seedling and juvenile plmt growth. Three sites were selected for study because of differences in plant Annual leader growth of mature plants was measured in native stature that were observed within relatively short distances (Barker populations. Basin big sagebrush plants outgrew Wyoming big and McKell 1983). At each site, plant height decreased with dissagebrush in the greenhouse, uniform garden, and leader growth tance along a transect at a right angle to a drainage. Plant height experiments. Difference in growth potential between the subspe-along the drainages averaged 2.5 m and decreased to less than 1.0 ties may be a consequence of ploidy diierences. m. The distance of the plant height gradient transects were 60,40, and 100 m for Sage Creek. Greasewood Wash. and Maeser. The most common, important, and widely distributed woody sagebrush (Artemisia L. subgenus tridentatae (Rydb.) E.D. McArthur) is big sagebrush (Artemisia tridentata Nutt.). Big sagebrush is common on millions of hectares throughout western North America from sout...

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