Great Basin montane forests
Great Basin montane forests are unique ecosystems located within the Great Basin Desert of North America, primarily spanning Nevada and parts of surrounding states. These forests emerge on isolated mountain ranges, transitioning from surrounding desert shrubland to diverse coniferous forests as elevation increases. The montane forests are characterized by varied vegetation, including pinyon-juniper woodlands, ponderosa pine forests, and ancient bristlecone pines, which are among the oldest living trees on Earth.
Climate and geography significantly influence the flora and fauna within these forests, which host a rich tapestry of life, including numerous mammal, bird, and plant species. Historically, these ecosystems have been shaped by natural processes and human activities, including livestock grazing and fire suppression, leading to increased vulnerability to wildfires and climate change. Conservation efforts are essential to manage these forests and address threats such as invasive species and altered fire regimes.
Public lands, including national parks and forests, play a crucial role in the preservation of Great Basin montane forests, providing recreational opportunities and vital resources. Understanding and managing the delicate balance between human use and ecological health is vital for the future sustainability of these remarkable forests.
Subject Terms
Great Basin montane forests
- Category: Forest Biomes.
- Geographic Location: North America.
- Summary: These forests, dominated by coniferous trees on isolated mountain ranges, rise up from desert shrublands within the Great Basin Desert. Altered fire regimes and climate change are potential threats to this ecosystem.
The Great Basin montane forests occupy isolated mountain ranges within the Great Basin Desert, rising from surrounding desert shrubland at lower elevations. This desert covers roughly 200,000 square miles (518,000 square kilometers), encompassing most of Nevada, parts of eastern California, western Utah, southern Idaho, and southeastern Oregon—and on some maps, it also extends into northwestern Arizona and southwestern Wyoming. Basin and range topography typifies this desert, consisting of valley basins flanked by north-south trending mountain ranges. Hundreds of these mountain ranges that support montane forests occupy the Great Basin Desert, with more than 300 discrete ranges mapped in Nevada alone.
A total of 33 Great Basin mountain ranges have peaks exceeding 10,000 feet (3,050 meters) above sea level. The higher-elevation mountains have cooler temperatures and greater precipitation, including snow, than the basins. The basins often receive only 6 inches (15 centimeters) of annual precipitation, compared with the mountains, which receive more than 20 inches (50 centimeters) per year. As a result, vegetation generally changes from desert shrubland in the basins to pinyon-juniper woodlands on lower mountain slopes, forests of various conifer species on higher mountain slopes, and alpine meadows on the highest peaks above where trees grow.
The current Great Basin montane forests partly originated from the contraction of conifer forests that during the last glacial period (more than 10,000 years ago) covered larger areas than forests do today. The petrified wood of these glacial-era trees can still be seen in areas that today support only desert shrubland.
Flora and Fauna
The plant and animal life of montane forests is not uniform from one mountain range to another. Forest composition varies with latitude, elevation, soil type, proximity to other mountain ranges (influencing species dispersal), geography (such as susceptibility to lightning that ignites wildfires), and past and present land use by humans.
The generalized vegetation pattern—which is not present on all mountain ranges—of Great Basin montane forests from low to high elevation includes: woodlands composed of the short trees juniper (such as Juniperus osteosperma) and pinyon pine (such as Pinus monophylla); ponderosa pine forests (Pinus ponderosa); mixed conifer forests comprised of species such as white fir (Abies concolor), limber pine (Pinus flexilis), spruce (Picea engelmannii), and subalpine fir (Abies lasiocarpa); and bristlecone pine (Pinus longaeva) or other conifers at the highest elevations. Bristlecone pines are among the oldest living organisms on Earth, often living more than 4,000 years on the high peaks. There also are alpine meadows near some of the highest peaks, above the tree line. Some mountain ranges contain deciduous forests of quaking aspen (Populus tremuloides); these trees colonize disturbed areas left by wildfires or avalanches.
The plants growing on the forest floor and in the understory also vary among mountain ranges and with elevation and soil type. Understories can be dominated primarily by shrubs, forbs, grasses, or mixtures. These plants reduce soil erosion, provide forage and habitat for animals, play an important role in fire ecology (by providing fuel), and enhance species diversity. Among the thousands of understory species are big sagebrush (Artemisia tridentata), currant (Ribes cereum), fleabane (Erigerondivergens), muttongrass (Poa fendleriana), and squirreltail (Elymus elymoides).
As with plants, a long-term perspective illustrates how animal species of the Great Basin have changed. During the last ice age, now-extinct camels, mastodons, sabertooth tigers, American cheetahs, and other species inhabited the area. Today, a different but still diverse array of species inhabits the region, including mammals, birds, amphibians, reptiles, fish, and invertebrates.
The 76,603-acre (31,000-hectare) Great Basin National Park in eastern Nevada, for example, lists 71 mammal, 241 bird, eight fish, 18 reptile, and six amphibian species as living in the park and vicinity. Carnivorous mammals include mountain lions (Pumua concolor), gray foxes (Urocyon cinereoargenteus), and coyotes (Canis latrans). Herbivorous mammals include mule deer (Ococoileus hemionus) and elk (Cervus elaphus). Other characteristic animal species that may be found in the Great Basin montane forests include bighorn sheep, jackrabbit, porcupine, marmot, weasel, and the ring-tailed cat.
Human Threats and Conservation
Beginning in earnest in the late 1800s and early 1900s, Euro-American settlement brought livestock grazing (cattle and sheep), timber harvesting, introduction of nonnative plant species (plants introduced as livestock forage or inadvertently introduced), and other human influences to the Great Basin area. Additionally, some of the montane forests are believed to have been partly shaped since the last ice age by recurring fires (ignited by lightning and in some places by Native Americans), which could affect tree density and species composition. Humans began suppressing these fires in some areas during the 1900s, which is believed to have resulted in a buildup of fuel and thus susceptibility to severe, deforesting fires.
Nonindigenous plants such as cheatgrass (Bromus tectorum) also have increased fuel loads in some areas. Climate changes may further influence montane forests, especially because the mountain ranges are isolated (limiting potential for species migrations), and species currently occupying the highest peaks cannot migrate upward. The most recent climate change has already had effects on this ecoregion: warmer temperatures, decline in snowpack, earlier spring runoff, and extended fire seasons may all have grave implications for water resources, and therefore for native ecosystems and biodiversity.
Public lands containing Great Basin montane forests are managed by the U.S. Forest Service, Bureau of Land Management, National Park Service, and Fish and Wildlife Service. Examples of these areas include the Humboldt-Toiyabe National Forest and Great Basin National Park in Nevada, Death Valley National Park in California, Cedar Breaks National Monument in Utah, Sawtooth National Forest in Idaho, and Malheur National Forest in Oregon.
Key management considerations common to all areas include understanding and accommodating fire regimes, ensuring that forests have desirable densities of trees (forests that are too dense are more susceptible to insect outbreaks and severe fires), limiting movements of undesired nonindigenous species, controlling livestock grazing areas, incorporating climate change into planning, and balancing human uses of forests with conservation strategies. These forests supply many services directly to humans, such as timber, grazing lands, water resources, carbon storage, and recreational opportunities. Montane forests within the larger desert landscape are irreplaceable resources to humans and numerous other species.
Bibliography
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“Great Basin Native Plant Project Report 2018-2021.” USDA Forest Services, 2021, www.fs.usda.gov/rm/pubs‗journals/2022/rmrs‗2022‗kilkenny‗f001.pdf. Accessed 12 Nov. 2024.
Pardi, Melissa I. et.al. "Testing Climate Tracking of Montane Rodent Distributions over the Past Century Within the Great Basic Ecoregion." Global Ecology and Conservation, vol. 24, Dec. 2020, doi.org/10.1016/j.gecco.2020.e01238. Accessed 12 Nov. 2024.
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U.S. Department of Agriculture (USDA), Forest Service. National Roadmap for Responding to Climate Change. Washington, DC: USDA, 2010.