The western part of the Olympic Peninsula is one of the unique places in the United States and even in the world, where so-called temperate rainforests grow.
Rainforests are usually associated with tropical jungles, that is, with humid dense forests in the equatorial region. But where is the equator and where is the northwest of the United States? The question is rhetorical, and nevertheless, rainforests grow here too. The fact is that, in addition to tropical and subtropical forests, there are also temperate rainforests. It would be more accurate to say that these are rainforests in the temperate zone, or in temperate latitudes.
A necessary condition for the existence of rainforests is regular heavy rainfall. And in this part of the United States there are no problems with this, which is due to the unique location of these forests. On one side is the nearby Pacific Ocean, on the other (in the central part of the peninsula) are the Olympic Mountains.
The Olympic Mountains, which reach heights of 2,400 meters in places, do not allow rain clouds from the ocean to travel further east. As a result, the greatest amount of precipitation in the United States falls to the west of Olympic Mountain: 3.6–4.2 m (!) each year. And to the east of these mountains, a relatively dry climate prevails, like in southern California.
Another (in addition to precipitation) important factor for rain forests in these latitudes is moderate seasonal temperatures. In winter, the temperature here rarely drops below zero degrees Celsius, and in summer it rarely rises above +25C. One of the most popular areas among tourists to see local rain forests is the Hoh River basin.
In these forests, unlike the tropics, coniferous species dominate (Sitka spruce, Western hemlock, Douglas fir), but some deciduous trees also grow, in particular, bigleaf maple. Many of them reach a height of 70-80 meters and are over 100 years old.
A characteristic feature of rainforests is the abundance of epiphytes. This tricky name hides plants that, unlike ordinary ones growing on the ground, live on other plants, using them only as a place to settle, a support. Due to this, they are freed from competition from representatives of the flora living on the surface of the soil for light and nutrients.
Trees whose branches and trunks are “decorated” with epiphytic plants (mosses, lichens, ferns, etc.) look very expressive. Although epiphytes “sit on the neck” of their green brothers, they are not parasites, independently receiving energy and nutrients through photosynthesis, and moisture from the air and precipitation. And forests decorated with epiphytes have a mysterious or even fabulous look.
All trees die sooner or later, falling to the ground. The biological decomposition of wood in temperate latitudes can be very long, taking up to several centuries. While this is happening, dead trunks are covered with vegetation, becoming home to young shoots of plants of various species. Americans define this phenomenon as “nurse logs”, which can be loosely translated as “nurse trees”.
