Vegetation Survey of Meeks Creek Watershed
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SWANSON HYDROLOGY + GEOMORPHOLOGY Appendix B. Vegetation Survey of Meeks Creek Watershed ecological system science hydrology + geomorphology restoration engineering regulatory compliance BOTANICAL RESOURCES OF MEEKS CREEK WATERSHED PURPOSE The study of vegetation carried out for this project includes preparation of a map of existing vegetation communities and a description of the ecological conditions of those communities. These can be used to compare the predicted consequences of different restoration options and as a baseline map for monitoring restoration effects. In addition, this study addresses pre-settlement vegetation and ecological processes - the only available reference basis for the restoration objectives of some of the community types. METHODS A comprehensive search was made from available published and unpublished information on the vegetation resources in Meeks Meadow, Campground and Marina (Study Area). The literature reviewed included: Lake Tahoe Watershed Assessment (Murphy and Knopp et al. 2000), Meeks Creek and Taylor Creek Wetland Conservation Plan (WTNC 2002), Meadows in the Sierra Nevada of California (Ratliff 1985), Riparian Community Type Classification of the Sierra Nevada (Potter 2003) and Status of the Sierra Nevada (SNEP 1996). Refer to the Literature Cited section for a more complete literature listing. As appropriate, information from these and other references have been incorporated into this botanical resources report. The botanical resources of the Study Area were examined on foot during October 2003. Plant ecologists Brian Cleary (M.S.), and Adrian Juncosa (Ph.D.) carried out the botanical fieldwork. Plant communities were identified based on field observations and analysis of vegetation signatures using color orthophotos provided by Aerial Data Inc., at a scale of 1-inch = 200 feet. Due to the onset of inclement weather, the vegetation boundaries were mapped as hand-drawn polygons in-house, then digitized into GIS using an IKONOS color satellite photo provided by the U.S. Forest Service, Lake Tahoe Basin Management Unit (LTBMU). During the field survey, notes were recorded on plant communities and species composition including invasive and non-native plant species. Plant species observed were recorded and included as Attachment B-1. Additional species are likely to occur and would require further investigation during the spring and summer blooming period. A sequence of historic aerial photographs (1940-2003) were examined in an attempt to identify vegetation changes over time as a result of natural ecological processes, such as the effect of fire on the progression of different vegetation communities leading to a climax community, known as succession, and to reveal potential anthropogenic perturbations including logging, livestock use, and recreation associated with resource acquisition in Meeks Meadow and recreational development of Meeks Bay Campground and Marina. Vegetation communities such as Mixed Conifer Forest, Montane Chaparral, and herbaceous habitats including wet and dry Montane Meadows were readily distinguishable. Unfortunately, these aerial photos could not elucidate the B-1 ecological conditions that occurred prior to the Euro-American settlement that took place in the Lake Tahoe Basin during the mid 1800s. Thus, despite the value of historic aerial photographs, much of our understanding of ecological changes and processes is derived from knowledge of Sierra Nevada plant ecology and observations obtained from field studies rather than analysis of historic aerial photographs. VEGETATION CLASSIFICATION FOR THE STUDY AREA Sierra Nevada plant communities are extremely variable in size and shape. For example, riparian areas along stream banks are linear features that can vary from fractions of an acre to several acres wide, and they can contain plant communities that extend many feet in length. Conversely, a willow community in a meadow is a patchy feature that can occupy a fraction to several acres and have dimensions that are many feet on a side (Potter 2003). It is recognized that hydro-geomorphic features, including banks, shores, floodplains, bars and terraces, play a significant role in determining riparian plant community composition (Warner and Hendrix et al. 1984). Similarly, herbaceous meadow communities may be classified based on various moisture regimes that largely indicate the vegetation type and dominant species. With forest communities, broader physiographic differences including slope, aspect, precipitation, temperature, and soil development govern the distribution of this vegetation type, although their shared boundaries are seldom distinct (Whitney 1979). It is widely believed that most plant species are ordered along environmental gradients, therefore, it is important to note that overlap in species distribution is considered largely coincidental and independent, and this may create difficulties for plant ecologists attempting to classify intricate and complex vegetation communities. Smith and Houston (1989) suggest that the vast majority of spatial and temporal structure in vegetation can be attributed to competition among species for light and water, as plants grow larger. Nevertheless, vegetation classification is a language created to bring order out of apparent chaos (Sawyer and Keeler-Wolf 1995) and is particularly useful to develop a baseline vegetation map for analyzing restoration alternatives and long-term monitoring. For this study, no single existing classification system fully accommodated the observed and somewhat complex vegetation community types located on site. Some of the designations used for naming the plant communities within the watershed are based in part on the U.S. Forest Service Region 5 Ecology Group using the Calveg Series Classification System (Parker and Matayas 1979). Other references, including Sawyer and Keeler-Wolf (1995), CDFG (2002), and Potter (2003), identified similar mapping units, however, these sources did not provide sufficient overlap among the vegetation types located within the Study Area. To the extent feasible, an attempt was made to divide vegetation complexes into a level of detail that was accurate enough for practical application to the present project. B-2 In general, the dominant plant species were considered “indicator” plant species, and thus, were used to delineate the vegetation communities where necessary. However, attention was also given to the presence of non-native and native invasive plants with emphasis placed on the herbaceous wet meadow communities dominated by various hydrophytic (water-loving) graminoid (grasses and grass-like plants such as rushes and sedges) species. Typically, this wet meadow vegetation formed somewhat distinct mosaic patterns with conifer and willow communities across the Meeks Meadow landscape, although some portions of the site did not exhibit clear, identifiable vegetation boundaries. For example, numerous young lodgepole pines (Pinus contorta var. murrayana) appeared to be invading portions of Wet Graminoid Meadow community in mesic (i.e., seasonally not too wet or dry) areas on site. Such areas were intentionally mapped as Lodgepole Pine Forest to reflect the ecological significance of this invading species in the context of maximizing opportunities to restore wet meadow communities in Meeks Meadow. Conversely, vegetation communities such as Mixed Conifer Forest were not mapped at a level of detail based on dominant species (e.g., White-fir Forest and Jeffrey Pine Forest etc.), as this habitat is not the primary focus of the study. FLORISTICS AND NOMENCLATURE The majority of the vascular plant species were identified using site identification, although numerous plants, particularly the graminoid species, were identified based on detailed examination with the use of a dissecting scope. The Jepson Manual (Hickman 1993) supplied taxonomy and nomenclature, as well as information regarding the distribution and habitats for many of the species identified on site. Additional references included A California Flora and Supplement (Munz and Keck 1968), A Flora of Marshes of California (Mason 1969), and the Manual of Grasses of the United States (Hitchcock 1971). All plant species provided in this report, including dominant and associate species, are first introduced with the common name, followed parenthetically by the scientific name. Thereafter, only the common name is used for each plant. PLANT SPECIES ECOLOGY Information regarding the identification of dominant and associate plant species with respect to classifying the vegetation communities on site was based on a subjective, qualitative assessment of the relative cover and density for each species within a given area; no quantitative measurements such as transect sampling were carried out for this phase of the project. Based on the importance of attempting to predict the consequences of several alternatives for restoring Montane Riparian and Montane Wet Meadow communities in Meeks Meadow, the wetland indicator status of each plant was obtained from the 1987 Wetland Plant List, California (Reed 1988) to examine the likelihood of plants found in various soil moisture regimes with which the listed species are typically associated. B-3 Wetland indicator species are so designated according to their frequency of occurrence in wetlands. For instance, a species with a presumed frequency of occurrence of 67% to 99% in wetlands is designated a facultative wetland indicator species. The wetland indicator groups, indicator symbol