baumzaehlen - Primeval Forests & Their Trees

©2017copyright christoph hase

Olympic National Park, Washington, USA

 

Olympic National Park (3733 km2) is famous for its untouched temperate rainforests and snow capped mountains. Elevations range from 0 to 2432 m. The park consists of two separate parts: a narrow strip along the Pacific coast and a large mountainous area to the east of it. Some of the largest known specimens of numerous tree species have been found in the park: Opens internal link in current windowThuja plicata (western redcedar), Opens internal link in current windowPseudotsuga menziesii var. menziesii (coast Douglas-fir), Opens internal link in current windowPicea sitchensis (Sitka spruce), Cupressus nootkatensis (Nootka cypress), Opens internal link in current windowTsuga heterophylla (western hemlock), Abies grandis (grand fir), Opens internal link in current windowAbies amabilis (Pacific silver fir) and Opens internal link in current windowPicea engelmannii (Engelmann spruce)1.

 

The forests of western North America are unique among the mesic temperate zone regions of the world in that they are almost totally conifer dominated from sea level upwards. This has often been explained by the present climate, with very mild winters and relatively dry summers, both of these phenomena favouring evergreen conifers over summer green angiosperms. Conifers are able to assimilate more effectively during moisture stress (summer) than angiosperms and they are able to continue assimilation almost throughout the mild winter. It has to be noted, however, that on the western slopes of the Olympic Mountains, not even summers are actually dry although most precipitation occurs during autumn, winter and spring: in the western valleys, approx. 250 mm of rain falls in the summer months (June-August). There are also persistent fogs during summer, further increasing the “precipitation”.2 Annual figures right on the coast are approx. 2300 mm, in the western valleys 3000–3600 mm 3 and along the western flanks of Mt. Olympus up to 6000 mm 4. Average annual temperature at the coast is approx. 10°C.

 

There are about 25 tree species in the park5, most are easy to identify. On the coastal plain, the most common tree species are Tsuga heterophylla and Thuja plicata. Immediately behind the beaches, particularly P. sitchensis and Opens internal link in current windowAlnus rubra (red alder) occur. In the western valleys further from the coast, P. sitchensis and T. heterophylla dominate both in denser forest as well as in those areas with very open canopy, where there is an undergrowth of impenetrable Opens internal link in current windowAcer circinatum (vine maple) thicket a few metres tall. In these areas, conifer reproduction is essentially confined to "nurse logs", and it has been suggested that the open forests are the result of insufficient numbers of nurse logs6. A. rubra groves are common along rivers. The slopes are dominated by Tsuga heterophylla and Abies amabilis on the western side and by Tsuga heterophylla and Pseudotsuga menziesii on the drier eastern side where fire is an important disturbance agent. Opens internal link in current windowTsuga mertensiana (mountain hemlock) is common near the treeline.

 

In addition to the A. circinatum and Vaccinium thickets, fallen giant trees and many steep slopes make off-trail hiking slow. Camping is allowed throughout the park excepting some areas with high visitation.

 

References:

 

1       Van Pelt, R. (2001): Forest Giants of the Pacific Coast. Global Forest Society.

2       Franklin, J. F. & Dyrness, C. T. (1988): Natural Vegetation of Oregon and Washington. Oregon State University Press.

3       Kirk, R. (2001): The Olympic Rain Forest, an Ecological Web. University of Washington Press.

4       Van Pelt, R. (2007): Opens external link in new windowIdentifying Mature and Old Forests in Western Washington. Washington State Department of Natural Resources.

5       Latham, R. E. & Ricklefs, R. E. (1993): Opens external link in new windowGlobal patterns of tree species richness in moist forests: energy-diversity theory does not account for variation in species richness. Oikos 67: 325-33.

6       Franklin. J. F. & Hemstrom, M. A. (1981): Aspects of Succession in the Coniferous Forests of the Pacific Northwest. In West, D. C., Shugart, H. H. & Botkin D. B. (eds.): Forest Succession. Concepts and Application. Springer.


Official site:

 

http://www.nps.gov/olym


Coastal Picea sitchensis (Sitka spruce) forest.
Picea sitchensis (Sitka spruce) stand north from Quinault Lake. The trees behind the large P. sitchensis are Tsuga heterophylla (western hemlock).
Picea sitchensis (Sitka spruce), large tree, centre; Pseudotsuga menziesii var. menziesii (coast Douglas-fir), large tree, left background; Tsuga heterophylla (western hemlock), conifer foliage; Acer circinatum (vine maple) shrubs, left and right. Elev. 280 m.
Pseudotsuga menziesii var. menziesii (coast Douglas-fir) stand on steep slope. Elev. 300 m.
Alnus rubra (red alder) forest on alluvial plain. Elev. 275 m.
South Fork Hoh River, elev. 275 m. Along the river, Alnus rubra (red alder) with Picea sitchensis (Sitka spruce) - Tsuga heterophylla (western hemlock) forest behind.
South Fork Hoh River, elev. 250 m. Along the river, Alnus rubra (red alder) dominates pioneer vegetation; behind it Picea sitchensis (Sitka spruce) - Tsuga heterophylla (western hemlock) forest.
Elev. 250 m. Along the river, Alnus rubra (red alder) dominates pioneer vegetation; behind it Picea sitchensis (Sitka spruce) - Tsuga heterophylla (western hemlock, drooping tops) forest.
South Beach. Stunted Picea sitchensis (Sitka spruce) foreground.
Picea sitchensis (Sitka spruce) invades Alnus rubra (red alder) forest. Elev. 275 m.
Populus trichocarpa (black cottonwood). Behind it Picea sitchensis (Sitka spruce).
Alnus rubra (red alder), left; Populus trichocarpa (black cottonwood), centre; Picea sitchensis (Sitka spruce), right, also left background. Elev. 275 m.
Partly dry South Fork Hoh River. On the left Alnus rubra (red alder) forest and the Populus trichocarpa (black cottonwood) of image 12 (the tall broadleaf crown surrounded by Picea sitchensis (Sitka spruce)).
Acer macrophyllum (bigleaf maple).
Acer circinatum (vine maple) thicket in open forest.
Open forest, elev. 250 m. Picea sitchensis (Sitka spruce), large trunks; Tsuga heterophylla (western hemlock), conifers with dense foliage; Acer circinatum (vine maple), shrubs.
Shady Tsuga heterophylla (western hemlock) forest. Elev. 300 m.
Large Thuja plicata (western redcedar) on a slope; Tsuga heterophylla (western hemlock), foliage on the right. Elev. 250 m.
Salix sitchensis (Sitka willow).
Sambucus racemosa subsp. pubens (Pacific Coast red elder).
Some broadleaf trees of the western valleys. S. callicarpa = S. racemosa subsp. pubens (Pacific Coast red elder).