This file was created by scanning the printed publication. Errors identified by the software have been corrected; however, some errors may remain. USDA United States =/ =/ Department of Agriculture Competitive Effects of -Forest Service Bluebunch Wheatgrass, Crested Rocky Mountain Research Station Wheatgrass, and Cheatgrass on Research Paper RMRS-RP-16 Antelope Bitterbrush Seedling February 1999 Emergence and Survival Derek B. Hall Val Jo Anderson Stephen B. Monsen Abstract Hall, Derek B.; Anderson, Val Jo; Monsen, Stephen B. 1999. Competitive effects of bluebunch wheatgrass, crested wheatgrass, and cheatgrass on antelope bitterbrush seedling emergence and survival. Res. Pap. RMRS-RP-16. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 7 p. The competitive environment into which plant seedlings emerge often determines the survival and performance of these individuals. This study was designed to determine the effects of bluebunch wheatgrass (Pseudoroegneria spicata), crested wheatgrass (Agropyron cristatum), and cheatgrass (Bromus tectorum) on soil moisture depletion, associated antelope bitterbrush (Purshia tridentata) seedling emergence, xylem pressure potential, and subsequent survival. In the fall of 1992, antelope bitterbrush seed was sown into the following four established competitive matrices: (1) bluebunch wheatgrass, (2) crested wheatgrass, (3) cheatgrass, and (4) bare soil control plots. Soil moisture and bitterbrush seedling xylem pressure potential data were collected through the spring and summer of 1993. Antelope bitterbrush seedling survival data were collected through the spring and summer of 1993, and again in July 1994. Invasion of bur buttercup (Ranunculus testiculatus) in the spring of 1993 increased the competitive environments with densities of 470 plants per m2 in the crested wheatgrass, 760 in bluebunch wheatgrass, 920 in control and 1,060 in cheatgrass plots. Soil moisture in crested wheatgrass plots tended to be lower than soil moisture in the bluebunch wheatgrass plots. The number of emerged bitterbrush seedlings were significantly (?= 0.99) negatively correlated with the number of total annuals per m2. Antelope bitterbrush seedling xylem pressure potentials were less negative in the bluebunch wheatgrass plots compared with the other plots. Percent antelope bitterbrush seedling survival over 2 years was significantly higher (nearly twice) when grown in association with bluebunch wheatgrass than seedlings grown in association with crested wheatgrass, cheatgrass, or bur buttercup. Keywords: Pseudoroegneria spicata, Agropyron cristatum, Bromus tectorum, Purshia tridentata, Rununculus testiculatus, xylem pressure potential, soil moisture, rangeland restoration The Authors graduate classes including range and pasture plant ecology, rangeland inventories and analysis, Natural Resource Plan- Derek B. Hall is a Scientist with Bechtel Nevada, PO Box ning, and Agrostology. He has completed research in Morocco, 98521, Las Vegas, NV 891 93-8521. His degrees are from Australia, and throughout the Western United States, focused Brigham Young University (B.S. in wildlife and range re- on the impacts to rangelands of land management practices sources, 1992; and M.S. in wildlife and range resources, 1994). and restoration of degraded rangelands. At the time of the research, he was a Research Assistant in the Stephen B. Monsen is a Botanist for the Shrubland Biology Botany and Range Science Department, Brigham Young Uni- and Restoration Research Work Unit at the Rocky Mountain versity, and concurrently a Biological Technician (1992 to (formerly, Intermountain) Research Station's Shrub Sciences 1994) for the Shrubland Biology and Restoration Research Laboratory in Provo, UT 84606. His degree is from Brigham Work Unit at the Intermountain (now Rocky Mountain) Re- Young University (B.S. in agronomy, 1958). He also has search Station's Shrub Sciences Laboratory in Provo, UT. graduate training at Brigham Young University (1958 to 1960) Val Jo Anderson is an Associate Professor in the Botany and in botany and range science. He began his Forest Service Range Science Department at Brigham Young University, research career in 1958 and has worked at the Forestry Provo, UT 84602. His degrees are from Snow College (A.S. in Sciences Laboratory in Boise, and since 1983 at the Shrub science, 1980), Utah State University (B.S., 1982 and M.S., Sciences Laboratory. From 1959 to 1969 he worked as a 1985 in range science) and Texas A&M University (Ph.D. in researcher for the Utah Division of Wildlife Resources in rangeland ecology, 1989). He joined the faculty at Brigham Ephraim, Utah. His research has emphasized wildland Young University in 1988 and teaches undergraduate and restoration in the Western United States and Australia. Rocky Mountain Research Station 324 25th Street Ogden, UT 84401 Competitive Effects of Bluebunch Wheatgrass, Crested Wheatgrass, and Cheatgrass on Antelope Bitterbrush Seedling Emergence and Survival Derek 9. Hall Val Jo Anderson Stephen B. Monsen Introduction These introduced annual and perennial grass spe- cies appear to affect native shrub recruitment and Shrubs dominate many plant communities through- subsequent community composition. Several studies out the Western United States, particularly in the have shown that competition from introduced grasses Great Basin. McGinnies (1972) suggested that the restricts either shrub seedling emergence or estab- northern desert shrub type is among the most impor- lishment or both. Hormay (1943a,b) reported that tant shrub community in North America. Shantz and cheatgrass retarded natural establishment of ante- Zon (1924) recognized three main associations in the lope bitterbrush. Holmgren (1956) concluded that few sagebrush or northern desert shrub type. Among antelope bitterbrush seedlings were able to survive these is the big sagebrush (Artemisia tridentata Nutt.) the first summer in cheatgrass stands. Monsen and association including communities dominated by big Shaw (1983) suggested that established stands of sagebrush, rubber rabbitbrush (Chrysothamnus nau- desert wheatgrass (Agropyron desertorurn Linn.), a seosus Britt.), and antelope bitterbrush (Purshia tri- close relative of crested wheatgrass, limited the natu- dentata Pursh.), among others. ral regeneration of antelope bitterbrush. Price and These communities, consisting of a variety of small Brotherson (1987) partially attributed low recruit- to large shrubs that form an open canopy, support a ment rates in stands of Stansbury cliffrose (Cowania grass/forb understory. Shrub-dominated communities mexicana stansburiana Torr.) to competition from provide crucial winter and spring habitat for wild annual grasses. Melgoza and others (1990) deter- ungulates, particularly mule deer and elk, as well as mined that cheatgrass competes with needle-and- cattle and sheep (McKell and Goodin 1973; Plummer thread grass (Stipa comata Trin. & Rupr.) and Dou- 1972).High energy content of dry grass culms coupled glas rabbitbrush (Chrysothamnus viscidiflorus Nutt.) with high protein levels found in the current year twig for soil water and negatively affects their water status growth of shrubs provide excellent winter and spring and productivity. Eissenstat and Caldwell(1988) re- forage (Cook 1972). ported that sagebrush indicator plants had lower Relatively constant and heavy use by wild and survival, growth, reproduction, and late-season water domestic ungulates has created changes in species potential in areas dominated by desert wheatgrass in composition of both woody and herbaceous compo- contrast to areas dominated by bluebunch wheatgrass nents of many communities. Cheatgrass (Bromus tec- (Pseudoroegneria spicata [Pursh.] Love). torum Linn.) and other annual weeds have invaded Native grass understories may also negatively im- and dominate many areas within brush communities pact shrub seedling survival (Eissenstat and Caldwell where native plant species have been weakened 1988; Hubbard 1959). However, introduced annual (Vallentine 1989). Crested wheatgrass (Agropyron and perennial grasses, namely, desert wheatgrass, cristatum Linn.) has been seeded onto millions of acres crested wheatgrass, and cheatgrass utilize soil mois- of rangeland throughout the Western United States to ture earlier in the growing season than the native stabilize herbage production, protect watersheds, and bluebunch wheatgrass because of their rooting char- control weeds (Holechek 1981). Crested wheatgrass acteristics (Aguirre and Johnson 1991; Caldwell and persists under heavy grazing pressure relative to Richards 1986; Harris 1967; Harris 1977; Harris and many native counterparts and has been seeded into Wilson 1970). The ability of these introduced grasses weakened native plant communities. to utilize soil moisture earlier in the growing season USDA Forest Service Res. Pap. RMRS-RP-16. 1999 than bluebunch wheatgrass gives them a competitive 0.5 m spacings in 9 m2 matrices with 49 plants in each advantage over bluebunch wheatgrass and quite pos- matrix. The transplants were watered periodically sibly, over other native species as well. Although through the first growing season to ensure the estab- bluebunch wheatgrass competes with shrub seedlings, lishment of a uniform and strong competitive matrix. it may not have as detrimental effect on shrub seed- Cheatgrass seed was collected near the study site ling survival as the introduced species (Eissenstat and and seeded in rows spaced 20 cm apart in