Influences of Adjacent Forest Management Activities on Migratory Elk of Mount Rainier National Park
Kurt J. Jenkins, Edward E. Starkey

CONCLUSIONS

Recent forest management activities on land adjacent to MORA appear to have benefited elk populations wintering outside the park. During the mild winter of this study, high-quality winter forages were more abundant in early seral than in old-age forest communities, which resulted in improved dietary quality for elk wintering outside MORA. High soil moisture, intensive browsing pressure by elk, and competition with productive understories all appear to have hindered conifer regeneration in cutover bottomland forests along the White River, and to have prolonged the beneficial influences of logging on elk forage resources. Presumably, below-average winter severity which prevailed during much of the last 10-15 years, coupled with enhanced forage production resulting from logging, has contributed to improved winter nutrition, survival rates and reproductive rates of cow elk, and population growth observed in the 1970's and early 1980's.

As described above, our results leave little question that clearcutting improved forage resources available to elk during a mild winter. Old-age forest communities, however, also provided important forage during a short critical period following one 12" snowstorm. These findings, together with abundant supportive evidence from other similar studies, suggest that mature coniferous forests are critical winter habitats of elk during winters when snow cover forage resources in clearcuts and other open areas. Mature coniferous forests are important both because of forage resources available within them and reduced energetic cost of foraging associated with low snow depths. Clearly, the optimum ratios of seral vs. old-age communities in the managed forest will depend upon prevailing winter severity, forage production trends, and elk management objectives for the region.

We offer the following interpretation of influences of forest harvesting on population growth and regulation of elk populations in seasonally variable winter environments. First, from the viewpoint of elk habitat management, we define the optimum level of forest harvesting as that which produces a balance between forage used by elk in mature forest during critical winter periods and forage used on the remaining winter range during mild periods (Scharp et al. 1985). The more mild the prevailing winter weather, the less forage is needed in old-age forest communities to sustain elk through an average winter. Therefore, clearcutting old-age forests will increase carrying capacities of elk winter ranges until forage produced in old-growth becomes limiting during snowy winter periods. Further reduction of mature coniferous forests below this optimum may increase carrying capacity during mild winters permitting continued population growth, but forage limitations in old-age forests may promote increased density-dependent and -independent mortality of elk herds during periodic severe winters. We suggest, therefore, that in the absence of intensive management of elk harvests, excessive reduction of old-age forests will increase the amplitude of population fluctuations over time due to increased population growth during mild winters and increased mortality of elk during periodic severe winters.

Intensive forest harvesting on elk winter-spring ranges in the White River, although providing a short-term boom of forage resources for elk, now has resulted in declining forage values. Future reductions of available forage, together with reductions of mature forested cover used by elk for foraging and energy conservation during severe winters, will probably reduce carrying capacities of seasonal elk ranges adjoining the park, and may increase density- dependent and density-independent winter mortality of elk. Increased human disturbance on elk winter ranges may further reduce carrying capacity of elk winter ranges adjoining MORA. Furthermore, increased harvest of antlerless elk is anticipated in the region, which in addition to helping stabilize population fluctuations may also further reduce population numbers.

In conclusion, we anticipate that in the absence of innovative new forage enhancement activities, past logging activities and continued forest succession will reduce and destabilize elk populations summering within MORA. We foresee little improvement in winter ranges adjoining MORA that will permit elk populations to continue to grow in the White River in the 1990's.