Stephen B. Monsen. Dr. Allan R. Stevens. Dr. E. Durant McArthur

Transcription

1 Ecological and biological factors influencing the presence and distribution of sagebrush taxa within the Uncompahgre Plateau - implications to community restoration Stephen B. Monsen Dr. Allan R. Stevens Dr. E. Durant McArthur The Uncompahgre Plateau (UP) Program was instigated through efforts by the Colorado Division of Parks and Wildlife to restore and improve big game habitats principally within this region. Various agencies including the BLM and USDA Forest Service of Regions 2 and 4 formulated an advisory committee and obtained funding from the Federal Native Plant Program to support the program. The Utah Division of Wildlife Resources, other state and local agencies, different universities, and the Uncompahgre partners have also remained as active cooperators. The primary objectives of the program has been to restore selective native plant communities that have been seriously altered and prevent the continued invasion and presence of cheatgrass brome (Bromus tectorum) and associated weeds. After extensive surveys the conditions within the various sagebrush (Artemisia spp) communities were considered most critical for restoration. Studies were initially instigated to advance the primary native species associated with the different sagebrush communities. This required a careful description of the ecological conditions and species composition associated with different taxa of sagebrush. Cultural practices required to aid local agencies and sectors of the private seed industry were cooperatively established to advance the availability and use of site adapted native plant materials. Studies quickly expanded to address degraded conditions within the sagebrush communities and mediate weed invasion throughout the entire Colorado Plateau. West (1983) described three major ecological ecoregions within the Colorado Plateau with dissimilar soils and environments. Different synecological relationships of sagebrush were also noted to occur within the Colorado Plateau

2 and between the Great Basin. The Colorado Plateau is interfaced with some species including sagebrush that tend to migrate from warmer climates of southern Utah and Arizona into cooler climates of Utah and Colorado. Consequently, plant selection and development for this region must be based on the assembly of species required to reconstruct very specific and diverse plant communities. Performance of candidate plants must be equated based upon their adaptation, compatibility, and performance with associated species and conditions within specific natural environments. This requires ecological and geographical distribution data along with cytogenetic and molecular biology to delineate genetic relationships and classification systems. Conventional plant selection practices based upon the development of a typical or individual superior ecotype for widespread use across many plant associations is less important than matching species or subspecies to the right habitat. Since sagebrush is such an important plant from ecological and management perspectives, it is important to determine the type and even the ploidy (the number of sets of diploid chromosomes in a plant) levels of sagebrush on a landscape scale. Many sagebrush species include plants and populations with multiple sets of chromosomes. Differences in ploidy levels appear site adaptive and serve to prevent gene flow between plants and taxa at different ploidy levels (McArthur and Sanderson 1999). The purpose of this study was to map all sagebrush areas of the Uncompahgre Plateau by species, subspecies, and ploidy levels. The results would be important to manage existing sagebrush communities and restore disturbed communities. Knowing ploidy levels would be useful so planting sites matches can be better made. Ploidy levels can also be utilized as an adaptive strategy because polypoids can be better adapted to extreme ecological environments than their diploid relatives. Lands within the Uncompahgre Plateau were surveyed and areas where sagebrush taxa occurred were identified and mapped using a GPS (global position system) by taking points around the edge of each sagebrush area. Sagebrush taxa were identified on site by morphological characteristics. Within each site leaves from 300 plants were collected randomly. Leaf samples were crushed in water and viewed under long-wave ultraviolet light and the amount of florescence was

3 recorded to confirm morphological identification (Stevens and McArthur 1974; McArthur et al. 1988). The leaf material was then examined using a flow cytometer to determine ploidy levels (Monsen et al and data on file). We were able to identify the taxa and ploidy levels of 6 species and subspecies of sagebrush on 1,099,876 acres of the Uncompahgre Plateau. The sagebrush (genus Artemisia, subgenus Tridentatae; base chromosome number x = 9). Encountered were: A. bigelovi, 4x; A. cana, 2x; A. nova, 2x, 4x; A. tridentata ssp. tridentata, 2x, 4x; A. tridentata ssp. wyomingensis, 4x; A. tridentata ssp.vaseyana, 2x. We found that some taxa and plants of different ploidy levels grew sympatrically, while other grew tightly parapatrically 20 separate combinations of sagebrush occurred with one to three taxa per sagebrush community (Monsen et al. 2006). However, we found no compelling evidence of hybridization even though hybridization is a relatively common event among sagebrush taxa (McArthur et al. 1988). Populations of palatable stands of Wyoming big sagebrush (A. t. ssp. wyomingensis) and mountain big sagebrush (A. t. ssp. vaseyana) were quite widespread; sometimes mixed with other sagebrush taxa including black sagebrush (A. nova). Wyoming big sagebrush was often found to be closely associated with Bigelow sagebrush (Artemisia bigelovii). Populations of big sagebrush displayed close alliance to certain habitats within the Uncompahgre Plateau. Ploidy levels appeared to serve as an adaptive strategy as polyploidies were better adapted to ecological extremes than diploid relatives (Sanderson et al. 1989). Schultz (1986) also reported morphological specializations have evolved along environmental gradients for some subspecies. Davis and Stevens (1986) and Frank et al. (1986) also conclude that significant differences in growth rates among subspecies of big sagebrush have resulted as an adaptation to site origin. Meyer and Monsen (1992) report that seed dormancy and germination patterns are correlated among all three subspecies of big sagebrush each subspecies exhibit a different pattern of variation. Their studies conclude that populations from cold winter sites require mechanisms to reduce fall germination and provide long periods of cold chilling - (20) weeks to stimulate germination. Seeds were slow to germinate usually with less than 50 percent of all viable seed germinating within 10 days. These factors favor germination beneath a snowpack

4 as risk from premature germination is lessened. In contrast, these authors found seed of all subspecies of big sagebrush obtained from warm climates were nondormant and capable of germinating immediately after harvest. Winter conditions are optimal for establishment of seeds originating from warm environments. Under favorable conditions, seeds germinate rapidly with over 50 percent germinating within 10 days. However, shallow buried seeds amount to small carryover with limited germination in subsequent years. Studies within the Uncompahgre Plateau indicate different species of sagebrush and subspecies of big sagebrush with specific ploidy levels occupied different climatic environments. Although different taxa occupied closely aligned sites, features of the adjacent environments separated the different plant populations. The differences among seed germination and seedling establishment of seed harvested from closely aligned wildland stands of sagebrush is critical to successful restoration of large-scale projects. Seed from plants adapted to specific locations germinate at favorable periods which significantly improve planting success. Restoration and treatment of sagebrush communities is possible within most areas of the Colorado Plateau. However, success is dependent upon planting site adapted taxa indigenous to the proposed restoration sites. Difficulties arise in identification of different taxa and hybrids throughout the Colorado Plateau. Moving seed from sagebrush population to distances of less than 300 miles and less than 1500 feet elevation is commonly recommended (Mahalovich and McArthur 2004). However, studies within the Uncompahgre Plateau indicate sagebrush populations are adapted to very fine scale environmental conditions. Wang et al. (1997), in a hybrid zone transplant study found that populations of sagebrush perform better at their home site than seedlings from a site 1000 feet away. Planting adapted ploidy level taxa of sagebrush is particularly important when treating large areas with diverse sites that naturally support different native plant communities. Under these situations different taxa of sagebrush naturally occur and should be restored. Planting adapted materials is critical when restoring dry environments. This is particularly important when treating sites occupied by Wyoming big sagebrush, a tetraploid (4x) taxa, which is smaller than

5 other big sagebrush taxa and has a slower growth rate but exhibits increased drought tolerance. Literature Cited Davis, J.M., and R. Stevens Comparison of production of twentyseven accessions of four sagebrush taxa. in E.D. McArthur and B.L. Welch, compilers. Proceedings symposium on the biology of Artemisia and Chrysothamnus. USDA Forest Service General Technical Report INT-200, Ogden, Utah, USA. Frank, C.T., B.N. Smith, and B.L. Welch Photosynthesis, growth, transpiration, and 13C relationships among three subspecies of big sagebrush (Artemisia tridentata Nutt.) p in E.D. Mc Arthur and B.L. Welch, compilers. Proceedings symposium on the biology of Artemisia and Chrysothamnus. USDA Forest Service General Technical Report INT-200, Ogden, Utah, USA. Mahalovich, M. F., and E. D. McArthur Sagebrush (Artemisia spp.) seed and plant transfer guidelines. Native Plants Journal 5: McArthur, E. D., and S. C. Sanderson Cytogeography and chromosome evolution of subgenus Tridentatae of Artemisia (Asteraceae). American Journal of Botany 86: McArthur, E. D., B. L. Welch, and S. C. Sanderson Natural and artificial hybridization between big sagebrush (Artemisia tridentata) subspecies. Journal of Heredity 79: Meyer, S. E., and S. B. Monsen Big sagebrush germination patterns subspecies and population differences. J of Range Management 45: Monsen, S., E. D. McArthur, A. Stevens, and S. Sanderson Distribution and ploidy levels of sagebrush taxa on the Uncompahgre Plateau. Abstract #255, Society for Range Management Annual Meeting, Vancouver, BC, Society for Range Management, Denver, CO, 266 p. 1 Sanderson, S. C., E. D. McArthur, and H. C. Stutz A relationship between polyploidy and habitat in western shrub species, p in A. Wallace, E. D. McArthur, and M. R. Haferkamp, compilers. Proceedings of symposium on

6 shrub ecophysiology and biotechnology. USDA Forest Service General Technical Report INT-256, Ogden, Utah, USA. Schultz, L.M Taxonomic and geographic limits of Artemisia subgenus Tridentatae (Beetle) McArthur (Asteraceae: Anthemideae), p in E. D. McArthur and B. L. Welch, compilers. Proceedings - symposium on the biology of Artemisia and Chrysothamnus. USDA Forest Service General Technical Report INT 200, Ogden, Utah, USA. Stevens, R., and E. D. McArthur A simple field technique for identification of some sagebrush taxa. Journal of Range Management 27: Wang, H., E.D. McArthur, S.C. Sanderson, J.H. Graham, and D. C. Freeman Narrow hybrid zone between two subspecies of big sagebrush (Artemisia tridentata: Asteraceae) Reciprocal transplant experiment. Evolution 51: West, N.E Great Basin Colorado Plateau sagebrush semi-desert. In: West. N. E., ed. Temperate deserts and semi-deserts. Elsevier Scientific. Amsterdam This is the published abstract of a poster paper of the same title but the authors are listed as Stevens, A. R., E. D. McArthur, S. B. Monsen, and S. C. Sanderson. The poster paper has sagebrush populations mapped. Data for this are on file with S. B. Monsen and A. R. Stevens.