Forest Succession in Relation to River Terrace Development in Olympic National Park, Washington

Abstract

The floodway zone of the Hoh River exhibits four terrace levels of different ages, formed by erosional activity of the river on valley fills. The vegetation in this valley is in a long—term seral sequence as shown by the zonal pattern in relation to aging and development of these land surfaces. Succession starts on gravel bars, which are dominated by Alnus rubra and Salix scouleriana. The following sequential forest communities, and associated ages of land surfaces, are found: Alnus rubra on alder flats (80—100 yr); Picea sitchensis—Acer macrophyllum—Populus trichocarpa on first terraces (400 yr); Picea sitchensis—Tsuga heterophylla on second terraces (750 yr); and Tsuga heterophylla on third terraces. The latter represents the climax community for the river terrace sere, and it occurs on surfaces exposed by retreating Pleistocene alpine glaciers. The first three terraces are derived from Neoglacial alluvial fills. There is a strong correlation among zonation patterns, forest succession, age of terraces, soil moisture, and soil profile development. Available soil moisture is an important factor governing the zonal sequence. The younger land surfaces are significantly drier than the older terraces. Plants on alder flats and first terraces must withstand greater moisture stress than those of second and third terraces. As the land surface ages, the soil profile develops; deeper, more mature soils are found away from the river. The term "Olympic rain forest" is inappropriately applied to this vegetation; "temperate moist coniferous forest" is more appropriate not only for forests in the Hoh Valley, but also for the rest of the Olympic Mountains and vegetation along the northern Pacific coast.

Wolves, trophic cascades, and rivers in the Olympic National Park, USA

“…Previous vegetation studies in the western drainages of Olympic National Park have consistently documented reduced recruitment of palatable tree species. For example, over three decades ago, Fonda (1974) found 4-30 cm dbh black cottonwood and bigleaf maple completely absent on Hoh River floodplains (¾1 m above the river), even though bigleaf maple seedlings were common. Black cottonwood, bigleaf maple, Douglas-fir (Pseudotsuga menziesii ) and western hemlock <10 cm dbh were also absent or infrequent on the first terrace (¾3 m above the river) even though larger size classes of these trees were present.…”

Postglacial vegetation and climate dynamics in the Seymour‐Belize Inlet Complex, central coastal British Columbia, Canada: palynological evidence from Tiny Lake

“…A migration lag is also unlikely because a possible refugium for Picea and Abies existed on the Queen Charlotte Islands during the Last Glacial Maximum (Warner et al, 1982), suggesting that postglacial recolonisation of the SBIC by these trees would have occurred rapidly had climate conditions been permissive. Soil moisture is restrictive for both taxa in Pacific North America today (Fonda, 1974), so Lateglacial climate amelioration was probably the ultimate cause of Lateglacial vegetation change at Tiny Lake. A similar mixed conifer community existed at Two Frog Lake (Galloway et al, 2007), Woods Lake (Stolze et al, 2007) and throughout Vancouver Island at this time (Hebda, 1983;Brown and Hebda, 2002;Lacourse, 2005), providing further evidence that the formation of this community at Tiny Lake was controlled by regional climate change.…”

“…sinuata; both species are common within open T. heterophylla forests in coastal BC today (Uchytil, 1989a,b). Neither taxa can selfregenerate owing to low shade tolerance and, as a result, stands are often even-aged and less than 60-100 a old (Fonda, 1974;Uchytil, 1989a,b). Therefore, the persistence of Alnus, irregardless of species, at Tiny Lake throughout most of the early Holocene suggests that an open coniferous canopy was maintained by less than optimal climate conditions and/or disturbance.…”

Modelling river and riparian vegetation interactions and related importance for sustainable ecosystem management

“…The steady distributions establish when the river does not migrate across the floodplain. Such distributions are the result of the dominant hydrological mechanisms that affect the riparian vegetation in the river system that is taken into consideration (Fonda, 1974;Nanson and Beach, 1977;Bradley and Smith, 1986). A first typical shape of stationary density distribution (called F1, see Fig.…”