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Forest Resources Status
Insects, disease, competing vegetation, climate, fire, and humans are the main factors that determine the health of forests. Overcrowded conditions are a widespread problem on some Nevada forestlands.
A majority of the forested lands in Nevada are administered by  the USFS. Federal agency reports were relied upon to compile forest health information. Other sources of information include state agency reports, scientific publications, and personal communication with experts. Detailed information is lacking on the condition of much of Nevada's forested lands. However, during Summer 2000, the National Forest Health Monitoring (FHM) program was begun by the USFS in Nevada. The FHM will provide ongoing information on forest conditions in the state. The first report became available in Spring 2002 (U.S. Forest Service, 2002)
Subalpine Timberline Forests and Woodlands
This high elevation ecosystem occurs in remote locations in the island mountain ranges in Nevada. Five needle pines (whitebark, limber, and bristlecone pines) are common species. The typical forest structure is open with older aged trees. Fires are infrequent in this forest type due to its open nature, low fuel accumulation, and cooler conditions. Fire return intervals are likely over 100 years. Consequently fire suppression has likely had limited impact on this type. Aerial surveys in 1999 revealed a fair amount of mortality caused by mountain pine beetle in the Toquima, Toiyabe, Shoshone, Jarbidge, Ruby and East Humboldt Ranges. This is the first time these ranges have been surveyed in a number of years, so it is uncertain whether or not this beetle activity is unusual. Five needle pines are susceptible to the exotic disease white pine blister rust. This pathogen has not appeared yet in the interior of the state, but is located on the western border in all five-needle pine species.
Engelmann Spruce - Subalpine Fir
This forest type is found primarily in the Jarbidge range and Pilot, Snake and Schell Creek ranges. Subalpine fir mortality is occurring at high levels in the Jarbidge Mountains due to a complex of insects and disease pathogens. Extended drought in the late 80's and early 90's stressed the trees, leading to increased insect and disease activity. High levels of subalpine fir mortality can significantly change the structure and composition of the fir forests. Historically, fire regimes of mixed severity occurred on a 50 to 80 year cycle, with lethal fires every 100 to 300 years. Because of increased mortality in these older age class forests the potential for stand replacing fires has increased. However, current conditions within the Region are within the historical range of variation for the type.
Potential major changes in stand structure and composition are high for this type. Changes will eventually occur as a result of large, stand-replacing fires, insect epidemics, or a combination of the two throughout much of the fir range.
Quaking Aspen
Quaking aspen is distributed throughout the State, occurring primarily along drainages, and at springs and seeps in mountainous terrain. The age of trees generally varies from 60 to 120 years. Most of the quaking aspen in Nevada is in a mid-to late seral stage of succession. Stands are not regenerating across much of the state for different reasons. In upper mountain locations, conifers are beginning to dominate aspen stands. Without some form of  disturbance to stimulate aspen suckering, and reduce shade intolerant conifers, these stands will continue to decline. In other areas wild and domestic grazing animals are preventing the stands from regenerating. Without management, these aspen clones will disappear and the probability is high that significant aspen acreage will continue on the path of succession to other vegetation types. The lack of successful regeneration over large areas increases this risk. Continued heavy browsing pressure on existing quaking aspen and other forage species will result in habitat degradation for all species found within this type.
Sierra Nevadan Forests
Sierran coniferous forests below the subalpine type can be classified as Red fir/Lodgepole pine, mixed conifer, and eastside pine. The red fir/lodgepole pine type occurs between 7000 and 8500 feet. Composition varies from almost pure fir to pure pine; with less frequent associates being white fir, Jeffrey pine at lower elevations and western white pine and mountain hemlock at the upper elevations. Fire frequencies are low in these high elevation forests and consequently, fire suppression policies have had less effect here than within the lower, drier forest types in Nevada.
The insects commonly associated with the species are fir engraver beetle, needle miners, and mountain pine beetle. Insect activity is at background levels currently. Earlier in the decade a prolonged drought combined with high stocking levels and annosus root disease led to high levels of mortality in the red fir. Lodgepole pine at high elevations was little impacted by the drought. Where associated with locally high soil moisture conditions at lower elevations, mountain pine beetle caused significant mortality. Overcrowding, the species' branch retention habit, and large numbers of beetle killed trees combine to create a significant wildfire hazard.
Mixed conifer forests are located below the red fir/ lodgepole pine type. Depending on aspect, soil moisture regime and disturbance history, the forest can range in species composition from almost pure white fir to a well balanced mix of white fir, Jeffrey and ponderosa pines with a smaller complement of sugar pine and incense cedar. The elevation range of this type is roughly 5800 to 7000. As in other forest types, fire suppression policies and the lack of active forest management has led to very high stocking levels, large fuel accumulations, and unsustainable species compositions over much of this type. Fire frequency within this type typically ranged from 5 to 30 years. Many of these areas have not experienced fire for over 100 years, putting much of the area far outside the natural range of variability for many characteristics. This situation places the forest at high risk of rapid change due to fire and insect activity.
The drought of the late 1980's to the mid 1990's triggered a bark beetle epidemic in the mixed conifer type that led to the death of millions of forest trees range-wide. The standing dead trees constitute a large fuel load. Current bark beetle activity is at endemic levels. Dwarf mistletoe is the most significant pathogen in these forests. The parasitic plants exist on all conifers in the ecoregion, except for incense cedar. Where levels of infestation are high, natural regeneration of the affected individuals is not possible, leading to species composition changes in the future.
 Related Information -- Forest Health Program -- Nevada Division of Forestry
Below the mixed conifer type is the yellow pine type (e.g., Jeffrey and Ponderosa pine). Historically this type was characterized by open "park like" conditions with multiple age classes distributed as small even aged groupings. Wildfire burned on a 5 to 12 year cycle removing brush and tree regeneration, and stimulating herbaceous plant growth. Fuel accumulations were spotty and insignificant. In Nevada, the southernmost occurrence of the yellow pine forest type is in the Spring and Sheep ranges in Clark County. Past cutting practices and fire suppression have left large portions of the yellow pine forests in overstocked, even-aged conditions. Basal areas exceed 250 square feet per acre, distributed among smaller size classes. Fuel accumulations are exceedingly high for this type and wildfire hazard is high. Risk of attack by Jeffrey pine and western pine beetles, and flat-headed borers are very high under current conditions. Western dwarf mistletoe is widespread across the type and infections are intense.
Pinyon-Juniper Woodlands
The pinyon and juniper (PJ) type is the most widespread forest type in Nevada (Figure 4-4). The PJ woodland type is composed of pure stands or a mix of singleleaf pinyon pine and three species of juniper, western, Utah, and Rocky Mountain. Utah juniper is by far the most widespread of the three. PJ woodlands have been harvested for fuel wood, posts and Christmas Trees. Also called "pygmy conifers" due to their short stature at maturity, PJ woodlands are found throughout the state, occupying about 7.1 million acres (10 percent of the state). The most extensive woodland areas occur in eastern Nevada, though western and central Nevada woodland areas are also large.
The range of the PJ woodland type has expanded and receded over the past 7,000 years, apparently the result of climate fluctuations. Over the past 500 years, the PJ populations have expanded further north, into the higher elevations, and down slope onto deep, well-drained soils on alluvial fans. The "migration" is believed to be a response to climate change as well as human induced changes. Aggressive wildfire suppression and deteriorated rangeland habitats have presented pinyon and junipers opportunities to become established in shrub and grass communities. These factors may also be creating favorable conditions for PJ stand density to increase and create a closed pygmy conifer canopy. Figure 4-4 shows the distribution of PJ woodlands about 1990.
The rate of woodland expansion appears to have accelerated during this century. Wildfire in pre-settlement PJ woodlands is thought to have been comparatively frequent (10 to 30 year recurrence, compared to 30 to 50 year intervals for Great Basin sagebrush), burning small trees and lighter fuels and leaving more of this vegetation type open and thickets confined to rockier and more dissected terrain (Griffen, 2002).
Risk of catastrophic wildfire is greater in the crowded conditions that are more commonplace in portions of eastern, central, and western Nevada. When conditions are right, stand-replacing fires can carry from the younger stands into the sparse, older stands, eliminating them as well. As woodland cover and density increase, other plant communities disappear. The replacement of native shrub and grass communities corresponds with a loss in diversity of land uses, native wildlife and habitat diversity, and favorable watershed conditions. For decades, ranchers, sportsmen, and agency land managers have attempted to remove and thin PJ forests using heavy equipment, herbicides, and fire in favor of shrub/grass vegetation. Likely there have been some locally important conversions; however, insufficient data exists to determine the amount of PJ forest converted and the resource advantages and disadvantages.
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| Wildfire in pinyon thickets can readily crown. PJ woodland harvesting and management ideas, viewed retrospectively, were mistaken. Ecologists surmise that clear-cutting; over-grazing herbaceous plants; and, fire exclusion abetted overcrowding. Actions taken to protect woodland zone watersheds and biodiversity include controlled burns in open PJ stands, pre-treatment of fuel-dense green woodlands, and restoring those burned. |
Insect and disease activity in the woodland type is at low levels. The most common destructive insects are pinyon ips bark beetle and borers. Population increases in these insects are usually local and are triggered by some sort of disturbance. Dwarf mistletoe is widespread in the pinyon pines and is the trees' most significant pathogen. Local pockets of Black Stain Root disease occur across the type. True mistletoe is common in the juniper species, but its harmful effects are minimal.
Currently, commercial and domestic use of woodland resources is limited to fuel wood, fence post, and Christmas tree harvesting. Opportunities exist to utilize PJ, but hauling distances and transportation costs to market are high. Promising economic ventures include combustion with other fuels at power plants to generate electricity, production of engineered chipboards, and the distillation of products from pinyon and juniper oils. As in other forest types of Nevada, the number of residential and commercial developments encroaching into woodland areas has increased. The risks and environmental impacts are the same. A major concern is the threat and management of wildfire. As an alternative to chaining, burning, or chemically treating woodlands, state and federal agencies are exploring and promoting productive uses.
Urban and Community Forests
For trees to grow in Nevada's communities, someone must plant them, then nurture and care for them for life. Nevada's earliest settlers planted the first urban forests with tree seeds and cuttings brought from their homelands and from cuttings taken from Nevada's native cottonwood trees. When the railroad was completed in the late 1860's and early 1870's, settlers began planting large, rooted trees delivered by train, alive and in good condition. Surviving trees continue to be the basis of the urban forests in older communities, providing shade, wind protection, and wildlife habitat. Unfortunately, many of these are in poor condition from improper care and pruning practices. Trees in Nevada are as important today as in settler times. The protection and proper care of community trees is a major concern. For every tree planted in America, four die. The average life expectancy of an urban tree ranges from seven to 15 years.
The NDF administers the state's Urban and Community Forestry Program. All tree care programs in Nevada have been implemented through the U.S. Forest Service, State and Private Forestry Program, municipal, or volunteer efforts. Since 1991, almost one million dollars of Federal funding has been awarded to communities and groups in Nevada for tree planting and tree care education. The loss of federal funding for urban forestry programming would seriously impact tree planting and tree care education in Nevada and could have a long lasting detrimental affect on the health of the urban forests.
Receiving recognition from the National Arbor Day Foundation under the Tree City USA program is an indication of the ability of a community to sustain and manage its urban forests. In 1990, only three Nevada towns had received Tree City USA distinction - Boulder City, Las Vegas and Reno. The number increased to seven in 1995, but fell to six by 2000 when Las Vegas failed to re-certify in 1999. The six Tree City USA communities are Henderson, Boulder City, Reno, Sparks, Carson City, and Nellis Air Force Base. Each has a recognized person or group responsible for tree management, a street tree ordinance, an Arbor Day Proclamation and tree planting celebration, and spends $2 per capita on their tree program. Non-incorporated towns in Nevada may have good tree care programs, but are difficult to enroll in the Tree City USA program. One reason is that county and a community's budget is difficult to separate; and, the county's tree budget may not meet the minimum $2 per capita requirement consistently from year to year.
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