Control/exclosure monitoring of tule elk effects on Tomales Point vegetation, Point Reyes National Seashore, 1998-1999.

McEachern, Kathyrn; Semenoff-Irving, Marcia; Atkinson, Andrea

Cattle were removed from Tomales Point at Point Reyes National Seashore, and native tule elk were re-introduced, in 1979. The elk herd is confined to an approximately 2,600 acre area at the tip of the point, and it has grown exponentially from 15 animals in 1979 to 451 in 2000 (Gogan 1986, Point Reyes National Seashore 2000). The vegetation of the elk range exhibits signs of release from cattle grazing by increased shrubbiness, and changes in the abundance and distribution of some plants that were palatable to cattle (Bartolome 1993). Management objectives are to maintain a healthy elk herd on Tomales Point, within a healthy ecosystem that supports populations of an endangered butterfly and several listed plants (National Park Service 1993). The objectives of this study are to make an assessment of the role of tule elk grazing in vegetation succession on the elk range; and provide an early warning system for the development of undesirable characteristics in the vegetation, both in terms of vegetation management for a sustainable native ecosystem and for elk nutritional needs. Data on habitat use indicate that the elk congregate and feed more intensely in some areas of Tomales Point than others. Therefore, vegetation degradation is likely to proceed at a faster rate in the heavily used areas than elsewhere. These areas may be retarded in their recovery toward a more balanced, healthy ecosystem. Alternatively, they may reach an undesired degraded condition faster that other areas as elk density increases. One goal of this study is to evaluate whether impacts to vegetation are substantially greater in high use areas than in low use sites, within the three main vegetation types on the elk range. Twelve pairs of fenced and unfenced plots are used in this study to monitor vegetation over the long term in both high and low elk use areas of the three main vegetation types of Tomales Point. Exclosure fences were installed in early spring of 1998. Vegetation was sampled in spring and summer 1998 and 1999. The 1998 data were taken soon after the fences were installed, so they were not expected to show effects of release from elk herbivory. Rather the 1998 data establish the baseline characteristics of the vegetation. The 1998 and 1999 data were used in an analysis of variance to evaluate differences in the rate of change in vegetation in high and low use areas of each vegetation type, and to show the initial effects of exclusion from elk grazing. Results show that there are differences among the vegetation types in species composition and apparent recovery processes for individual species. Changes detected through the monitoring thus far are for the most part consistent with predictions from ecological observations of recovery from grazing release in similar systems. The range is similar to other northern coastal sites that have been heavily grazed by cattle in the past, and there are no apparent widespread and systematic problems with erosion, lack of ground cover or loss of important elk forage plants. It is impossible to see trends yet, with only one transition between 1998 and 1999 to evaluate. Addition of the 2001monitoring data to the analysis should bring better resolution to patterns hinted at in these data. And, longer term monitoring will allow for trend analyses that show the effects of elk on the vegetaion, and provide early warning of undesirable conditions in the vegetation.