Hokkaido montane conifer forests

• Category: Forest Biomes.
• Geographic Location: Japanese archipelago.
• Summary: The major Japanese island of Hokkaido features mountain peaks and valleys that are home to a vibrant evergreen ecosystem with high species diversity.

Hokkaido, the northernmost of Japan's major islands, has a rugged landscape of snow-capped volcanoes. Natural high-elevation cold temperature regimes here are mitigated somewhat by the moderating atmospheric influence of the surrounding ocean. Together, elevation zones and strong seasonal changes have provided for rich species diversity. Human impact on the environment here, however, has become profound.

Japan's high levels of species richness and endemism (species found nowhere else) are by-products of island geography, climatic influences, and ice-age refugia. Nearly 2 million years ago, colliding Pacific and Eurasian plates gave rise to snow-capped mountains and volcanoes, many of which are active today. Hokkaido, the northern-most of Japan's 6,852 islands, is bound by the Sea of Japan (west), Sea of Okhotsk (north), and Pacific Ocean (east). Soya Strait, to its south, separates the island from the largest Japanese island, Honshu.

Hokkaido is home to the Hokkaido Montane Forest biome, one of nine such forest ecoregions in Japan. The World Wildlife Fund considers this biome vulnerable, due to high rates of habitat conversion, few intact areas, wildlife poaching, and development pressures.

Geography and Climate

Japan's island ecosystems are distributed along a north-south climate gradient, according to regional differences in temperature and precipitation. An oceanic mild climate is responsible for warm temperate rainforests—also known as evergreen broadleaf or Laurisilva—in the south. To the north lie the cool temperate montane forests, including those on Hokkaido, where the average annual temperature hovers at 46 degrees F (8 degrees C) and average annual precipitation is 45 inches (115 centimeters).

Most of the island experiences cool summers and icy winters. The conifer forests on Hokkaido thrive from sea level up to about 4,900 feet (1,500 meters). In the central highlands is the mostly volcanic Daisetsu mountain range, also known as the Roof of Hokkaido. The elevation of the highest mountain within the range is approximately 7,500 feet (2,290 meters).

Biota

Hokkaido coniferous forests share several species with the Siberian taiga, including snow forest affinities along upper montane and subalpine zones. Dominant conifers include Asian or Jezo spruce (Picea jezoensis) and Sachalin fir (Abies sachalinensis), mixing with birches (Betula ermanii and B. maximowicziana) that are sometimes found in pure, post-fire stands. Upper elevations, in the alpine zone, are dominated by Siberian dwarf pine (Pinus pumila) interspersed with birch-alder (B. ermanii-Alnus maximowiczii) and mountain ash (Sorbus sambucifolia). These create thicket and scrub communities with poorly developed understories, but thick ground mosses.

Notably, Asian spruce is widely distributed in East Asia, including the Kamchatka Peninsula in Russia, presumably through an ancient connection to the Russian Far East established during repeated ice ages. Recurring ice ages also resulted in circumpolar species distributed on Hokkaido, such as bunchberry dogwood (Cornus canadensis) and wood sorrel (Oxalis acetosella), among others.

In the central part of this ecoregion can be found many rare and endemic (found only here) plant species, including the willow (Salix paludicola), the wolf's bane (Acontium yamazaki), and the whitlow grass (Draba nakaiana). There are also more than 400 species of ferns and 200 species of mushrooms on the island.

Hokkaido's vertebrate species total more than 200 birds and 40 mammals. Species of conservation concern include Stellar's sea-eagle (Haliaeetus pelagicus); white-tailed sea-eagle (H. albicilla); Blakiston's fish owl (Keputa blakistoni), a rare and endangered owl; the endangered Japanese crane (Grus japonensis); and an endemic subspecies of hazel grouse (Tetraste bonasia vicinitas).

Endemic mammal subspecies include pika (Ochotona hyperborean yesoensis), a remnant of past glacial epochs, a threatened sable (Martes zibellina brachyuran), and the Sika deer. Hokkaido is also the only place in Japan that has brown bears (Ursos arctos yesoensis): the Yezo bear. Most of the other mammals here are small: rodents, rabbits, bats, red fox, and weasels. Hokkaido forests also provide habitat for a variety of frogs, salamanders, lizards, and snakes.

Examples of relatively intact montane forests occur in two main areas on the island: Daisetsuzan National Park, the largest national park in Japan; and the nature reserve Horoka Tomamu Montane Forest, located at the headwaters of the Mu River in the center of Hokkaido. This reserve includes species-rich hemiboreal (containing elements of both temperate and boreal zones) forests that provide good examples of native plant communities.

Human Impact

Present threats to the preservation of wildlife on Hokkaido include poaching, especially for sable fur; construction of roads; tourism; agricultural activity including over-grazing; and industrial development. Another concern is climate change. It is getting warmer in Japan—an increase of about 1.8 degrees F (1 degree C) during the last century—especially in urban areas, where the heat-island effect is combining with global warming to generate unusually hot temperatures. Japan's network of islands is particularly vulnerable to sea-level rise, which could be 1.5 to 3 feet (0.5 to 1 meter) or more by century's end, depending on how global emissions play out, and effects worsen when rising sea levels combine with storm surges.

Japan also will likely experience more frequent heat waves, droughts in places, intense rain and stronger typhoons (already on the rise), and a decline in marine productivity because of the degradation of coral reefs.

Upper elevation communities, especially unique subalpine ones, may recede on all but the tallest and most northern-latitude mountains here, due to the rising temperatures. Snowfall may increase on Hokkaido, however, given the island's relatively high latitude and high-elevation areas. Such climatic extremes will affect human health (e.g., rise in tiger mosquito populations, heat exhaustion); agricultural production (e.g., projected decline in rice yields of 12 to 13 percent by mid-century throughout most of Japan); and wildlife vigor (e.g., seasonal timing, growth, survival, and migration routes of Pacific salmon—the Okhotsk Sea is an important life line for regional salmon).

How climate change effects the composition and processes that maintain forests depends on many factors, including site-specific ones, such as microclimate and soils; topographic position, such as slope, aspect, and elevation; and the climate-niche preference of local forest species. It is likely that as conditions warm, species will move up in elevation and/or latitude, where they can.

It would appear that because of Hokkaido's high latitude, it may not experience as dramatic a change in its plant communities as will the more southerly areas. However, regional climate change projections forecast a decline in the climate niche for conifers—especially high-elevation types—and an increase in the climate niche of temperate-favoring broadleaf deciduous trees. A 38-year study found that rises in temperature and precipitation have resulted in an overall decline in conifers. Efforts are underway throughout Japan, given its vulnerable status, to address climate-change impacts on agriculture, water storage, fisheries, forestry, and urban areas.

Bibliography

Akashi, Nobuhiro, Noritoshi Nitta, and Yasuyuki, Ohno. "Effect of Forest Management on Understory Vascular Plants in Planted Abies Sachalinsis Forests." Forest Ecology and Management, vol. 497, 1 Oct. 2021, doi.org/10.1016/j.foreco.2021.119521. Accessed 22 Nov. 2024.

 “Climate Change Alters Tree Demography in Northern Forests.” Hokkaido University, 21 Jul. 2019, www.global.hokudai.ac.jp/blog/climate-change-alters-tree-demography-in-northern-forests/#:~:text=The%20rise%20in%20temperature%20and,of%20researchers%20from%20Hokkaido%20University. Accessed 22 Nov. 2024.

Government of Japan: Environment Agency. “Technology Transfer Manual on Nature Conservation.” Overseas Cooperation Panel, Japan, 1999. . Accessed 22 Nov. 2024.

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Uesaka, Shohei and Shiro Tsuyuzaki. “Differential Establishment and Survival of Species in Deciduous and Evergreen Scrub Patches and on Bare Ground, Mt. Koma, Hokkaido, Japan.” Plant Ecology 175, no. 2 (2005).