UNDERSTORY PATCH DYNAMICS AND UNGULATE HERBIVORY IN OLD-GROWTH FORESTS OF OLYMPIC NATIONAL-PARK, WASHINGTON

The relationship between native ungulates (mainly Roosevelt elk, Cervu s elaphus L.) and the occurrence of three patch types in an old-growth (220- to 260-year-old) Sitka spruce (Picea sitchensis (Bong.) Carrier e) - western hemlock (Tsuga heterophylla (Raf.) Sarg.) temperate conif erous rain forest was investigated on the South Fork Hoh River in Olym pic National Park. The distribution, frequency, and size of two unders tory patches (grass, moss) and patches where shrubs had escaped herbiv ory (refugia) were sampled along transects. Vegetation standing crop, percent cover, species richness, and equitability along transects were compared with conditions in two 8-year-old 0.5-ha ungulate exclosures . Ungulate herbivory profoundly affected the distribution and abundanc e of understory patch types. Grass-dominated patches disappeared follo wing 8 years of protection from ungulate herbivory. Ungulates maintain ed a reduced standing crop, increased forb species richness, and deter mined the distribution, morphology, and reproductive performance of se veral shrub species. There is clearly a dynamic relationship between p atch type, tree fall, and ungulate herbivory in these old-growth fores ts. Our results show that ungulate herbivory is a driving force shapin g vegetation patterns in coastal coniferous forests.