Sitka Spruce Plantation Forest

Category: Forest Biomes.

Geographic Location: North America.

Summary: The first afforestation site in North America has tested the toughness and adaptability of the Sitka spruce species since the project began in 1805.

The original Sitka Spruce Plantation Forest biome is located on the Aleutian island of Amaknak (also called Umaknak), Alaska; it is the site of the oldest recorded afforestation project on the continent. The forest, known to researchers as The Forest or AHRS UNL-074, is a National Historic Landmark site and was naturally treeless until the early-19th-century experiment that planted the spruce here.

The Sitka spruce is a species named for the Alaskan town of Sitka—even though the tree is found all along the northwest coast of the United States. It has a straight trunk, conical shape, and long, downward flowing branches. The tree can grow to 164 feet (50 meters) tall—or even to 300 feet (92 meters) in the most spectacular of the documented cases—with a trunk diameter of more than 6 feet (2 meters). The tree’s bark is greyish brown with curved fissures and flaky plates as it grows, and the leaves are green flattened needles that are stiff, hard, very sharp, and grow individually. The spruce reaches maturity relatively quickly, and takes 40–60 years to reach its maximum timber potential, rather than, for example, 150 years for oak.

Amaknak is located 800 miles southwest of Anchorage, Alaska. The climate of the island, and all of adjoining Unalaska Bay, is cold maritime, with long periods of wind, drizzling rain, and fog. The mean annual temperature is about 40 degrees F (5 degrees C), and temperatures range from a cold of 32 degrees F (0 degrees C) in winter to a summer high of 52 degrees F (11 degrees C). The area has approximately 225 days of rain every year, making it one of the rainiest places in the United States.

Afforestation

The Sitka Spruce plantation forest here was started in 1805, when the Aleutian Islands were part of Russia. The Russian government supported a tree-planting program on Amaknak Island to establish a reliable timber industry and promote human settlement on the treeless island. The plantings consisted mainly of Sitka spruce (Picea sitchensis) that was transplanted from southeast Alaska’s Kodiak Island to the Russian establishment of Unalaska here and on neighboring islands. Climatic and ecosystem conditions on the island proved generally too harsh for the forest to thrive.

After the area was purchased by the United States in 1867, the project attracted visiting botanists, who, throughout the 20th century, kept trying to develop forest on the island. Many waves of seedlings from the contiguous United States were transplanted to Unalaska in the effort to combat erosion and to make the island more habitable for settlers.

The Sitka spruce was the most successful of the various planted species, and reforestation efforts tended to focus on the continuation of this particular conifer. It normally has a lifespan of 400–700 years. A handful of the original, 1805-planted trees have endured both the tough northern climate and soil, as well as contamination from human projects and pests such as bud moth (Zeirapnera spp.).

It is thought that, as some Sitka spruce on Amaknak and Expedition Islands have survived for centuries, and have spread some of their own seedlings, the species could become naturalized on those islands. Natural regeneration is indeed succeeding in some areas, with seed crops succeeding from plantings established in 1950–70. Successful spruce trees, however, need on the order of 670–700 growing degree days for pollination, fertilization, and embryo growth to occur properly, and an additional 625 growing degree days for germination after pollination.

Biodiversity

Sitka spruce can grow close together to make a very dense canopy that blocks sun from penetrating to the woodland floor, making it difficult for other plants to grow beneath them. Sitka spruce forests at their maximum provide shelter from wind, rain, cold, and heat to biota below, so that such animals as deer and fox can find cover. Birds of prey, including goshawks and sparrowhawks, tend to find the spruce ideal for nesting and hunting. Birds such as the crossbill, tree creeper, coal tit, and siskin live and feed around Sitka spruce in many locations.

Prior to the establishment of the forests on Amaknak, native vegetation was primarily meadow with grasses, sedges, and herbs. The first plot of trees was planted among lyme grass (Leymus spp.). The volcanic soils, finely textured and rich in organic matter, were considered adequate to support rapid tree growth.

In other parts of the world, notably Iceland, arborists and other researchers have attempted to replicate the Amaknak Sitka spruce afforestation program. The scale of the life span of the species makes it difficult to assess the relative success or failure of such experiments in the near term.

Environment

Increased human population, exposure to industrialization, and construction on adjacent lands has altered the topography of the Sitka Spruce Plantation Forest biome here. Drainage systems on the site have not been updated, and with the frequent flooding, seepage from underground fuel tanks and a diesel fuel spill have contaminated water runoff and soils. These factors endanger the sites of the remaining original trees.

There are recent initiatives to arrange a pollution cleanup in and around the forests by both private land owners and public agencies. The U.S. Forest Service has recommended installation of a new drainage system and a public education program to inform the community of the ecological repercussions of construction and contaminants in the area.

Climate change poses other threats to the forest that could have both positive and negative effects. Milder temperatures could extend the growing season and curtail tree mortality. However, the warmer temperatures—and increased rainfall—could attract more pests and, with sea-level rise, worsen erosion problems.

Bibliography

Alden, J. and D. Bruce. Growth of Historical Sitka Spruce Plantations at Unalaska Bay, Alaska. Portland, OR: U.S. Forest Service Pacific Northwest Research Station, 1989.

Dammert, Auri. “Dressing the Landscape: Afforestation Efforts on Iceland.” Unasylva 52, no. 207 (2001).

Hermann, R. “North American Tree Species in Europe.” Journal of Forestry 85 (1987).

"Sitka Spruce Plantation National Historic Landmark." National Park Service, 26 Oct. 2021, www.nps.gov/places/sitka-spruce-plantation.htm. Accessed 1 Sept. 2022.