General Technical Report RMRS-GTR-22
The Northern Goshawk in Utah: Habitat Assessment and Management
Recommendations
General Technical Report RMRS-GTR-22
The Northern Goshawk in Utah: Habitat Assessment and Management Recommendations
Trends and Risks to Habitat
Natural Threats
Forests are complex and dynamic. The potential vegetation types of Utah range from subalpine fir to pinyon/juniper. Each of these potential vegetation types have a wide range of biophysical attributes that result in a variety of stand structures and compositions influenced by a wide range of disturbance factors. These range from those induced by wind, snow, ice, and fire to those that are human-caused. Landscapes of Utah are widely used by human habitation, timber extraction, recreation, livestock grazing, and are important sources of water. Because of these current and potential disturbances, lands classified by each of the potential vegetation types present their own unique threats to the goshawk and to its habitat.
White Fir -- The white fir potential vegetation type is dominated by late seral species with over 80 percent of the type occupied by white fir (table 8) (fig. 4). Even though this type is capable of supporting ponderosa pine and quaking aspen, only 3 percent of the potential vegetation type was occupied by these early seral species. Douglas-fir and ponderosa pine, also early seral species, were highly prized lumber species and many were removed in the late 1800's and early 1900's. Fires that historically burned in these forests at intervals of 20 years or less now have potential to be stand replacing. If the forests in this potential vegetation type were open and dominated by early seral species, the fires would likely be of low intensity and severity. Relatively shade tolerant late seral species tend to be more shallow rooted than early seral species. Therefore, more of the nutrient and microbiological capital of the soil is now close to the surface. In addition, the crowns of late seral species are nutrient rich and usually extend to the ground. Because of this, compression of the nutrients and microbiological attributes accumulate near the soil surface where they are at risk when these forests burn. In contrast, ponderosa pine is deep rooted and has high crowns with relatively lower nutrient content. So there is less risk to the microbes and nutrients even if the forest is replaced. Forests dominated by early seral species (especially the pines) are, in general, more stable in both the short- and long-term (Harvey and others in press).
In addition to forests in this potential vegetation type being potentially unstable and at risk to fire, their structural attributes make them undesirable for the goshawk compared to more open ponderosa pine, Douglas-fir, or quaking aspen forests. As a result of currently dense stocking levels and multiple canopy layers, large trees for nesting would be limited. In addition, dense, multistoried canopies would likely hinder foraging opportunities by obstructing flight and sight lanes.
Subalpine Fir -- The current vegetation of the subalpine fir potential vegetation type is dominated by late seral species primarily subalpine fir and Engelmann spruce mixed with lodgepole pine (table 8). These late seral species mixes are highly susceptible to insect and disease epidemics, as exemplified by the spruce beetle and balsam bark beetle mortality visible in much of the potential vegetation type. Insect surveys conducted in 1996 indicate a large proportion of the large trees in the potential vegetation type were killed by beetles (Gardner and others 1997) (fig. 5). This trend will likely continue, especially in areas with a high dominance of Engelmann spruce. Without some form of stand replacing disturbance, quaking aspen and lodgepole pine, the two major early seral species of the type, will continue to decline from their already low representation. Quaking aspen occupies less than 4 percent of the potential vegetation type and lodgepole pine occurs on less than 1 percent of the area. Quaking aspen is one of the most important cover types supporting the goshawk in Utah. If quaking aspen continues to decline in this potential vegetation type, it will likely impact goshawks. Stand replacing wildfires are an infrequent event in this potential vegetation type but, with the large amount of dead and down material found in this potential vegetation type, intense and severe wildfires are an increasingly likely possibility. Similar to the white fir potential vegetation type, wildfires in this type (because of the dominance of late seral species) would likely damage the soil resource and might impair long-term productivity. In the absence of wildfire in this potential vegetation type late seral vegetation will likely increase beyond 45 percent of this area that it already occupies. These subalpine fir dominated forests would provide poor to marginal habitat as a result of cluttered multistoried stands and lack of prey (except for the snowshoe hare).
Lodgepole Pine -- Lodgepole pine potential vegetation type covers only 1.3 percent of the State but it is unusual in that, because lodgepole pine is normally a seral species, there are only certain conditions that allow it to persist over the long-term. There are few other conifers that grow with lodgepole pine on this potential vegetation type, making any threat to that species a threat to forest cover. However quaking aspen is a frequent seral species. Since the 1960's bark beetles have been very active in this potential vegetation type, killing large areas and opening many stands. A large proportion of the potential vegetation type is currently occupied by mid- to old-aged trees (table 15); therefore the risk of additional insect related mortality is still high. In addition, some lodgepole pine stands on this potential vegetation type are prone to develop with high densities of slow growing trees. Historically, lodgepole pine in this potential vegetation type was affected by dwarf mistletoe and bark beetles, with fire periodically regenerating the species. Much of this potential vegetation type has been opened up by bark beetles but it is regenerating to lodgepole pine under the dead overstory. The present condition of the potential vegetation type appears to be part of normal cycle and most stands will continue to develop naturally. Surface fires that have frequented these forests could once again thin the even-aged structure. In their present form, most forests in this potential vegetation type, with dead overstory trees and a dense young understory, are good goshawk habitat. As the standing dead trees fall, they will decrease the habitat value.
Table 15 -- Proportion of each potential vegetation type with various stand structures.
Engelmann Spruce -- Engelmann spruce and subalpine fir mixed stands dominate this potential vegetation type. Similar to the white fir and subalpine fir potential vegetation types, it is also dominated by late seral species, subalpine fir and Engelmann spruce. Also similar to other potential vegetation types where quaking aspen is seral, only 2 percent of the type is covered by quaking aspen but there is 12 percent of the potential vegetation type covered by a mix of lodgepole pine and quaking aspen. There is also a fair representation of lodgepole pine mixed with Engelmann spruce, covering 14 percent of the potential vegetation type. This potential vegetation type has a good mix of early and late seral species. The current high proportion (79 percent ) of mid- and old-aged trees (table 15) make these stands highly susceptible to infestations of spruce bark beetles. Bark beetles tend to attack and kill large trees within infested stands. As a result, nesting habitat would likely be adversely affected. As the bark beetle kills Engelmann spruce, however, there may be enough of a seed source for the early seral species to regenerate. It appears that, depending on the spatial arrangement of the seral species in the long-term, these forests will regenerate to a mixture of Engelmann spruce and early seral species. In the short-term, forests growing on this potential vegetation type will be susceptible to damaging wildfires but because of their elevation, wildfires are likely to be infrequent.
Ponderosa Pine -- Ponderosa pine dominates this potential vegetation type even though Gambel oak, and quaking aspen are important seral species (table 8). Ponderosa pine is highly prized for its lumber; as a result, the majority of the ponderosa pine potential vegetation type has been partially cut, removing mature trees. Domestic livestock grazing, along with the exclusion of fire, has disrupted native fire cycles and probably contributed to the decrease of early seral species. Ingrowth of small trees has created high, large fuel loads in some areas, along with thick layers of needles on the forest floor. However, this ingrowth has not occurred to the same extent that it has occurred in other potential vegetation types. When fires burn in these forests, trees can be killed and limited soil damage is possible depending on the duration and intensity of the fire. Stand-replacing fires are more likely now, compared to the time prior to successful fire exclusion. In some areas, root disease and bark beetles are likely to stress and kill trees as a result of the dense forest conditions. In the short-term, forests growing on this potential vegetation type will probably continue to become more dense and more prone to fire and disease, likely to adversely altering goshawk foraging habitat. In addition, if large trees are not produced, future nesting opportunities will be limited. In the long-term, this type has the greatest potential of all of the potential vegetation types in Utah for the introduction of restorative mechanical and fire treatments. These treatments can clean stands, making them more insect, fire, and disease resistant and better goshawk habitat.
Quaking Aspen -- The quaking aspen potential vegetation type covers 10 percent of Utah. Quaking aspen stands dominate this potential vegetation type, occupying 84 percent of it. In addition, this potential vegetation type and the quaking aspen it supports, are some of the most valuable goshawk habitat in the State. Many successional changes occur in the forb, shrub, and grass layers as they respond to different disturbances. But these changes are probably not a great influence on habitat quality for goshawks. Since quaking aspen is normally an early seral species, the environmental conditions that make quaking aspen a persistent species are unknown, but major disturbances might alter the environment, disrupting the gradual and continuous regeneration. An important characteristic of this potential vegetation type is that the stands tend to be uneven-aged; quaking aspen growing on other potential vegetation types tends to be even-aged. The primary threats to quaking aspen stands growing on this type are browsing by domestic livestock and wild ungulates and stand-replacing fires that are ignited from adjacent types. Without a major disturbance or overgrazing, both in the short- and long-term, these stands should remain relatively stable and resilient.
Douglas-fir -- Forests growing on the Douglas-fir potential vegetation type are dominated by Douglas-fir or Douglas-fir mixed with other species (79 percent) (table 8). Less than 2 percent of the type is occupied by ponderosa pine. The mixed species condition, as with the other potential vegetation types, compresses nutrient and microbiological processes near the soil surface making them vulnerable to loss from wildfires and some management activities. Because of multiple canopies, live fuel loadings in many of these stands are high and the structure facilitates the initiation and spread of stand replacing wildfires. In addition to the lack of ponderosa pine in this potential vegetation type, there is an absence of quaking aspen, highly important for goshawk habitat. Since European settlement, large ponderosa pine and Douglas-fir were frequently harvested in this type. Multiple canopies, dominated by Douglas-fir, make the current conditions of this type very susceptible to root diseases and insects. In the short-term, forests growing on this potential vegetation type are relatively unstable and prone to a wide range of stand replacing disturbances including epidemics of insects and diseases. Similar to stands growing on the ponderosa pine potential vegetation type, these too are good candidates for the introduction of fire and restoration of seral species. In the long-term, under active management to introduce ponderosa pine and quaking aspen into the system, these forests will become more stable and resilient. If Douglas-fir continues to be the dominant species, stands will continue to be unstable and decrease in value for the goshawk.
Pinyon/Juniper -- The pinyon/juniper potential vegetation type covers approximately 50 percent of the forests and woodlands of the State and is totally (100 percent) occupied by pinyon and juniper trees. No recognizable amounts of early seral forbs, grasses, or shrubs were evident from our assessment. No other potential vegetation type is so dominated by the late successional species. With this condition and the indeterminate successional pathways present in this type, the short-term prognosis is a continued dominance of pinyon and juniper. Throughout the State there have been various attempts to transform many of these woodlands to earlier successional stages with limited success. Mechanical, chemical, and fire treatments have been used to convert late seral pinyon/juniper to grass, forb, and shrub communities (Everett 1987). Post-treatment plant communities do not follow any standard successional pathway and if a species is not on the site at the time of disturbance, it will not be there after the treatment (Everett 1987) (fig. 1). Moreover, these communities are susceptible to the introduction of exotics either intentionally or accidently. The introduction of exotics also changes successional pathways and makes future trends even more indeterminate. The introduction of cheatgrass (Bromus tectorum) into this potential vegetation type has made fires more intense, severe, and frequent. The resulting fire cycle decreases the perennial shrubs, grasses, and trees and increases the annuals that degrade the site (West and Van Pelt 1987). Similar to the other potential vegetation types that are dominated by late seral vegetation, the pinyon/juniper potential vegetation type is unstable in the long-term, in this case because of exotics and unknown successional pathways. In Utah, there are no documented nests occurring in this potential vegetation type but, because it occupies so much of the State, it may be important to the goshawk, especially as winter foraging habitat.
Administrative Threats
Owners or administrators of the forests and woodlands of Utah include the USDI National Park Service, USDI Bureau of Land Management, USDA Forest Service, State of Utah, and private and Native Americans. Lands owned and managed by the different entities are distributed throughout the State (map 10). By far, the USDA Forest Service administers the majority of the lands in these potential vegetation types (table 16). Also, these lands contain the majority of the high and medium valued nesting habitat (table 17). The majority of the lands controlled by the USDA Forest Service are important foraging habitat for mammals and woodpeckers (table 18). The largest proportion of high (60 percent) and optimum (56 percent ) value habitats are managed by the USDA Forest Service with State, private, and Native American entities managing smaller amounts (table 19). Lands administered by the Federal agencies are managed by laws, policies, and regulations that provide for the protection and enhancement of wildlife habitat. Conversely, lands managed by State, private, and Tribal entities are not controlled by such laws. Of the lands administered by the State, 34 percent are rated as high value habitat and 9 percent are rated as optimum (table 20). On non-Federally administered lands there is no assurance that they will be managed in a manner which will be favorable to goshawks and their habitats. Activities on these lands that alter forest vegetation, such as timber harvest, fire, and livestock grazing, if not properly executed, could adversely affect goshawk habitat at least for the short-term, and likely for the long-term.
Map 10 -- Principle owners or administrators of the forest and woodlands of Utah.
Table 16 -- Proportion of each potential vegetation type managed by various administrative entities.
Table 19 -- Proportion of high and optimum value habitat managed by various administrative entities.
Threats From Management Activities
The subalpine-fir, white fir, lodgepole pine, ponderosa pine, and Engelmann spruce potential vegetation types are primarily administered by the USDA Forest Service (table 16). Private land owners control limited amounts of the potential vegetation types, with the exception of the white fir, quaking aspen, and Douglas-fir potential vegetation types where over 26 percent is controlled by private land owners. Because there are minimal restrictions on the use of private land, there are no assurances that goshawk habitat will be sustained on these lands. Moreover, these potential vegetation types are dominated by late seral species prone to fire, insects, and disease. These are all endemic processes that can have both positive and negative effects to goshawk habitat. It is likely that these lands will not be managed to reduce these natural risks nor will they be managed to perpetuate goshawk habitat.
The USDA Forest Service manages its forested lands for a variety of objectives ranging from intensive forest management to recreation (table 21). The largest block of wilderness is in the Uinta Mountains in the northeastern Utah (map 11). Range management is emphasized (featured use or priority use) on 17 percent of the subalpine fir potential vegetation type and 4 percent of the white fir and Engelmann spruce potential vegetation types. The majority of lands in which range is emphasized are rated high or medium for nesting (table 22). These lands are also good mammal habitat and rated medium for woodpeckers (table 23). In terms of overall habitat, 34 percent of lands with a range emphasis (feature or priority use) were rated as high value habitat and 17 percent were rated as optimum (table 24). Of the high value habitat managed by the USDA Forest Service, 27 percent has a range emphasis (table 25). This management direction potentially can decrease prey habitat by removing cover and food for prey species. Indirectly it can interfere with fire regimes and native forest succession. Depending on the intensity and duration, grazing could be detrimental to goshawk habitat and in particular to aspen stands.
Map 11 -- The major management categories for Forest Service administered lands in Utah.
Table 21 -- Proportion of potential vegetation type in various Forest Service management categories.
In general, timber management is emphasized on 25 percent or less of the subalpine fir, white fir, and Engelmann spruce potential vegetation types (table 21). Similar to where range is emphasized, the majority of the lands where timber is emphasized is rated either high or medium nesting habitat (table 22). These lands are also excellent mammal habitat and moderately important for woodpeckers or other birds (table 23). Of the high valued habitat on USDA Forest Service lands, timber is emphasized on only 20 percent of the high value habitat and 18 percent of the optimum habitat (table 24).
Over 20 percent of subalpine fir and Engelmann spruce potential vegetation types is in the mixed uses management category. A variety of uses can occur on these lands such as timber harvesting, livestock grazing and recreation. On these lands, the general standards and guides of the National Forest Plan applies, and there is no single management emphasis. These forests are managed within regulations and policies that direct conservation and management of sensitive species. Therefore, if proper management strategies are implemented within these potential vegetation types, forest management actions are not likely to adversely affect goshawk habitat in the long-term.
The lodgepole pine, quaking aspen, and ponderosa pine potential vegetation types are the only potential vegetation types in Utah where the primary tree species and the late successional species for the type are the same. For the most part, lodgepole pine dominates the lodgepole pine potential vegetation type and quaking aspen dominates the quaking aspen potential vegetation type. These attributes make these potential vegetation types unique. Similarly, quaking aspen is the only early seral species on the ponderosa pine type. The USDA Forest Service administers 77 percent of the lodgepole pine potential vegetation type, over 45 percent of the quaking aspen and ponderosa pine potential vegetation types, and private owners control about 38 percent of the quaking aspen potential vegetation type (table 16, Map 10). On the proportion controlled by private owners there are minimal restrictions on land uses so there are no assurances that goshawk habitat will be sustained. Over 75 percent of the lodgepole pine potential vegetation type is administered by the USDA Forest Service with 58 percent managed with a timber emphasis. In the quaking aspen and ponderosa pine potential vegetation types, less than 15 percent are managed with a timber emphasis but over 15 percent of the types are in the mixed use category. Of the lands managed for a variety of uses, 53 percent are rated high for nesting habitat and 68 percent high value for mammals (tables 22, 23). Both mixed use and timber categories are managed within the standards and guides of the Forest Plans; if proper management strategies are implemented, the impact on goshawks should be minimal. In the ponderosa pine and quaking aspen potential vegetation types, range use was emphasized in over 15 percent of the area. Similar to the fir and spruce potential vegetation types, livestock grazing can change successional pathways and change fire regimes. In particular, livestock and wild ungulate grazing could retard and damage regeneration in the quaking aspen potential vegetation type which depends on continual regeneration. This potential vegetation type is important because quaking aspen is the only cover type and this tree species is widely used by goshawks.
The majority (60 percent) of the pinyon/juniper potential vegetation type is administered by the Bureau of Land Management with 15 percent or less privately owned, administered by the State, or administered by the USDA Forest Service. Because the successional pathways are so indeterminate in this type, and the majority of the type is occupied by late successional species, management actions could easily cause declines in habitat quality. Exotic grasses have changed the native successional pathways and disrupted the native fire frequencies, severities, and intensities. All these conditions indicate that the pinyon/juniper potential vegetation type will continue to experience instability and invasion of exotics.
Title: Trends
and Risks to Habitat: RMRS-GTR-22 -
The Northern Goshawk in Utah: Habitat Assessment and Management
Recommendations
Electronic Publish Date: May 26, 1999
Expires: Indefinite
Last Update: January
15, 2002