Himalayan subtropical pine forests
Himalayan subtropical pine forests are a distinct forest biome located primarily in the lower elevations of the Himalaya Mountain range, spanning from Afghanistan to Myanmar. Dominated by the chir pine (Pinus roxburghii), these forests extend approximately 1,240 miles and are characterized by relatively low biodiversity compared to other forest types. The region experiences a subtropical climate with significant rainfall influenced by the summer monsoon, making it suitable for various flora and fauna, including around 120 mammal species and 480 bird species, some of which are endemic to this biome.
The chir pine serves multiple ecological and economic roles, as it is drought-resistant, fast-growing, and utilized for timber production, resin extraction, and as a source of fuel. However, these forests face numerous environmental threats, including deforestation, grazing, and frequent fires, leading to significant degradation and the presence of stunted trees. Conservation efforts are critical to protect the remaining forest areas, as they play a vital role in preventing soil erosion and maintaining ecosystem stability. The dynamics of climate change also pose challenges, highlighting the need for sustainable management practices to ensure the longevity of these unique forests.
Himalayan subtropical pine forests
- Category: Forest Biomes.
- Geographic Location: Asia.
- Summary: This unique subtropical forest biome is dominated by Pinus roxburghii, the chir pine, and has low levels of floristic and faunal biodiversity.
The Himalayan region extends across south-central Asia from Afghanistan to Burma, or Myanmar. The Himalaya Mountain range arcs east and west for 1,491 miles (2,400 kilometers). Altitude zonation breaks out into three major zones: the Sub Himalayas, with elevations of 2,952 to 3,937 feet (900 to 1,200 meters); Lower Himalayas, averaging 12,139 feet (3,700 meters); and Greater Himalayas, rising above 19,685 feet (6,000 meters), including the world's tallest peak, Mount Everest. Annual rainfall here is in the 59–98-inch (1,500–2,500-millimeter) range, and is affected by the June-to-September summer monsoon.
Vegetation
In the Himalayan region, the vegetation transitions from a semideciduous, willow tree species of sal (Shorea robusta) in the foothills, through evergreen tree stands based around chir pine (Pinus roxburghii), and to oak trees (Quercus spp). As elevation increases, evergreen vegetation dominates up to 11,480 feet (3,500 meters), after which alpine meadows occur above the timberline. The pine forests here stretch for almost 1,240 miles (2,000 kilometers) across the lower elevations of almost the entire length of the Himalaya Mountain range.
The predominant pine species in the region is chir pine (Pinus roxburghii). Chir pine dominates in the lower elevations at less than 7,550 feet (2,300 meters) along the central and western Himalayas. At higher elevations, above 7,550 feet (2,300 meters) and up to 9,840 feet (3,000 meters), the blue pine (Pinus wallichiana) proliferates. Other, less dominant pine species include chilgoza pine (Pinus gerardiana), which occurs in the dry valleys of the Himalayas, eastern Afghanistan, and northern Pakistan; khasi pine (Pinus kesiya); and mercus pine (Pinus merkusii), which occurs mostly in the eastern Himalayas of Assam state and Burma, or Myanmar.
The dominant chir pine subspecies here, Pinus roxburghii Sargent, is a wind-pollinated, subtropical evergreen species. It is also an early colonizer and a fast-growing tree, replacing the oak forests that are affected by negative habitat pressures across the Himalayas. The density of pine trees in a typical forest can vary from 80 to 630 trees per 2.5 acres (one hectare). The biomass density varies widely, depending on the succession stage and site-disturbance regimes.
Chir pine is found interspersed with other trees here, such as sal; the oaks Quercus leucotrichophora, Q. floribunda, and Q. semecarpifolia; west Himalaya fir (Abies pindrow); and Himalayan birch (Betula utilis). The chir pine is highly drought-resistant; it is widely planted by locals because of its high survival rate and ease of plantation establishment and management.
Although chir pine trees themselves are fire-resistant, the dried pine needles that constitute forest litter are quite fire-prone, due to their high resin content. Chir pine forests are characterized by frequent fires; this often results in low plant biodiversity. To control fires and facilitate growth of grass for cattle feeding, local people use fire as a management tool. The resultant grass layer in the pine forest is dominated by species such as Arundinella nepalensis, Themeda anathera, and Imperata cylindrica, which all have fodder value.
Human Use of Resources
Pines serve as a valuable timber resource for the human population. Chir pine timber is particularly useful for making items such as railway sleeper cars, wooden poles for telecommunications lines, home furniture and cabinets, and packing cases and crates. Chir pine also is a source of good-quality oleo resin, which after distillation generates turpentine oil and rosin. This turpentine is then used in the preparation of paints, varnishes, polishes, chemicals, and pharmaceuticals; whereas rosin is used extensively in many industries to make soaps, paper, sealing waxes, oilcloth, inks, and disinfectants.
The resinous wood and pinecones of the chir pine are burned for both fuel and lighting. The seeds are edible. The resin from the leaves has medicinal properties and is used by locals to heal skin lesions. The leaves are also used for purposes such as thatching, packing, cattle bedding, and fertilizer.
The oil of chir pine needles is used as a diuretic by the local people. The bark decoction made from blue pine yields a yellow dye, which is used for dyeing woolen clothes and home textiles. For all of these reasons, pines in the region are widely planted by locals as well as forest officials for economic use as well as ecosystem functions, especially for preventing erosion on the hillsides.
Wildlife
The wildlife supported by the Himalayan subtropical pine forests is relatively poor compared with that of many tropical evergreen forests. Mammals account for about 120 species within these forests, including the Asian elephant (Elephas maximus), clouded leopard (Pardofelis nebulosa), gaur (Bos gaurus), golden langur (Trachypithecus geei), barking deer (Muntiacus muntjak), and goral (Nemorhaedus goral).
The forests also support a rich variety of about 480 bird species. Among those species unique to this biome and found nowhere else, that is, endemic species here, are the cheer pheasant (Catreus wallichi), the chestnut-breasted partridge (Arborophila mandellii) and nine other endemic and near-endemic bird species.
Environmental Threats
The Himalayan subtropical pine forests are under intense anthropogenic pressure, due to deforestation, grazing, lopping of tree branches, and removal of litter for fodder and fuelwood, in addition to frequent fires. Most of the pine trees in the region are stunted; the forests are of secondary nature, having been logged or otherwise cleared for agriculture. Prime forests are now restricted to less than five percent of the region.
Some non-anthropogenic causes of forest degradation include geological disturbances such as landslides, soil erosion, and earthquakes. These phenomena affect both ecosystem stability and function. Conservation efforts to mitigate these effects are needed to protect the remaining forests in the region.
Potential climate change threats to this area were once thought to be mainly from melting glaciers, according to a 2007 United Nations report that predicted Himalayan glaciers would disappear by about 2035, cutting into the groundwater supply to this biome. However, a more recent study from the universities of California and Potsdam report that the Himalayan glaciers are advancing, rather than retreating. Other factors beyond average air temperature—including the fields of rocks on the glacial fields—may have greater impact on preserving glaciers than originally thought.
Another issue throughout Himalayan forests, in general, is that while protected areas exist as part of a larger conservation effort, researchers have noted that much of this land is not the land most necessary to preserve and protect. Protecting the Himalayan subtropical pine forests is important as pine forests aid in erosion resistance. One group of researchers recommended that conservationists work to resort native forests, specifically, as such biomes effectively control soil erosion and soil quality.
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