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| | Tools and LinksManagement Forest Type Descriptions - Land Use History of the Colorado Plateau
- World Wildlife Fund
- NatureServe
- US Forest Service
Forest Health Wildlife - Species Lists - US Forest Service (Lists are within publication, see forest type code 2121 for mixed conifer)
General Reources Discussion ^This section is aimed specifically at the mixed conifer forests of Arizona, New Mexico and Arizona at elevations of 8000 feet to 10,000 feet (2500 to 3000m) and at lower elevation on north-facing slopes and in canyons (Ronco et al. 1983). The most common species include Douglas fir (Psuedotsuga menzisii), White Fir (Abies concolor), blue spruce (Picea pungens), and aspen (Populus tremuloides), while Engelmann spruce (Picea engelmannii), subapline fir (Abies lasiocarpa var. lasiocarpa), ponderosa pine (Pinus ponderosa), limber pine (Pinus flexilis), southwestern white pine (Pinus strobiformis), and gambel oak (Quercus gambelii). The forest type can be subdivided into a myriad of habitat types based on the plant associations of a small geographic region (e.g. Moir and Ludwig. 1979, Alexander et al. 1984). This discussion focuses on the ecology and management of the mixed conifer type more generally across the southwest.
As with most forests, southwestern mixed conifer forests provide a multitude of values including animal habitat, water storage, timber and non-timber forest products, recreation opportunities, and wilderness. For example, mixed conifer forests are home to many animals including threatened and endangered species such as tassel-eared squirrel (Sciurus aberti) and Mexican Spotted Owls (Strix occidentalis lucida).
The natural fire regime of southwestern mixed conifer forests is less frequent and more variable than that of ponderosa pine forest (Touchan et al. 1996).Researcher have identified a range of mean fire return intervals for southwestern mixed conifer forests from 7 to 37 years (Dieterich 1983: 22 yrs, Geils et al. 1995: 10 yrs, Grissino-Mayer et al. 1995: 7 yrs, Touchan et al. 1996: 10 to 14 yrs, Covington et al. 1998: 7 to 11 yrs, Webb 2003: 23 to 37 yrs). Pre-fire suppression fires in mixed conifer forests varied in severity from surface fires to patchy (or passive) crown fires across relatively small geographic areas (Fulé et al. 2003). All species within the southwestern mixed conifer are fire-intolerant when small and some species such as Douglas fir and ponderosa pine grow to become fire tolerant (US Forest Service 2006).
Southwestern mixed conifer forests support a wide variety of insects and pathogens (Ronco et al. 1983, Geils et al. 1995). Western spruce budworm (Choristoneura occidentalis) has the widest and most visible impact (Fellin and Dewey 1992). Since 1900, the trend of western spruce budworm outbreaks is toward increased severity and spatial synchrony (Ryerson et al. 2003). Dwarf mistletoe species (Arceuthobium sp.) infect a number of conifers including Douglas fir, southwestern white pine, and white fir (Mathiasen 1979, Mathiasen 1990, Filip et al. 2000). Each species of dwarf mistletoe is species specific and reducing growth and vitality of their host. Exotic pests and pathogens are also of concern, particularly Spruce aphid (Elatobium abietinum) (Lynch 2004) and white pine blister rust (Cronartium ribicola) (Conklin 2004).
The structure and species mixed in southwestern mixed conifer forests has changed greatly in the last century. As is common across western forests, many mixed conifer stands are more dense than they were before fire suppression (Dahms and Geils 1997). "The history of partial cutting, extensive cutting restrictions, and successful wildfire control in the Southwest have allowed ecological succession to increase the number of conifers, especially the proportion of shade-tolerant species such as white fir," (Johnson 1994). In some cases, fire suppression has shifted dominance from ponderosa pine to a white fir (Covington et al. 1998). Fire suppression has increased the impact of natural stresses on similar mixed conifer forests in California (Savage 1997). Management ^
This discussion of management of southwestern mixed conifer forests is guided by the ideas of ecological forestry (Evans 2006) and provides an general view of the possibilities that should be tailored to specific site conditions. A central management challenge is to reestablish fire in southwestern mixed conifer forests order to maintain their intrinsic value as well as the goods and services they provide for humans. Reestablishing fire will create forest conditions that are within the range of historic variation. In many areas, particularly those with high fuel loads early season (spring) burns are more appropriate than later season burns. "Burning areas with high fuel loads in early season when fuels are moister may lead to patterns of heterogeneity in fire effects that more closely approximate the expected patchiness of historical fires," (Knapp and Keeley 2006) Prescribe fire may also be effective in the fall when coarse woody material is still moist from the monsoon season (Orlando Romero, Senior Forester, Forest Guild, personal communication). At lower elevations, where mixed conifer forest interface with ponderosa pine, fire frequency is likely to be greater on S and W aspects (Fulé et al. 2003). Mixed conifer forests that have a mixed severity fire regime are less likely to experience the stand replacing fire events possible in dense mixed conifer stands (Fulé et al. 2003). Reintroduction may also reduce the impact of western spruce budworm by reducing the spatial extent of multi-storied stands with high densities of shade-tolerant trees, which tend to be more susceptible to western spruce budworm attacks (Dahms and Geils 1997). Stands that are have densities higher than the historic range of variability are more susceptible to exogenous stresses (Savage 1997). Therefore, returning stands to more natural conditions should make them more resistant to introduced pests and pathogens and global climate change.
Silvicultural treatments can play a crucial role in returning forests to conditions within the historic range of variation and produce timber and other goods for human use. In some cases, silvicultural thinnings need to occur before prescribed or "wildland fire use" fires will have a low severity effect (Heinlein et al. 1999). Thinnings can be difficult to finance because many of the products taken out of the woods will have low economic value because of their size or wood characteristics (Gorman et al. 1999). However, thinnings can produce products such as fence poles that have a high value for local use. Thinning may also increase water quantity in mixed conifer watersheds (Ffolliott and Thorud 1977), but there is insufficient research to recommend thinning for water production. Increased canopy openings that allow for accumulation of snow in shaded drifts can increase water storage in the spring (Smith et al. 1997 p453). Because of the impact on tree vigor, reducing mistletoe infestations through thinnings would have forest health benefits (Filip et al. 2000). Due to fire suppression there is likely to be higher populations of dwarf mistletoe across the forest type, and hence little risk of adversely affecting species that rely on its presence. Windthrow is a risk in thinned mixed conifer stands, especially those made up of suppressed trees (Ronco et al. 1983).
Because of the wide spectrum of species in mixed conifer forests, there are a wide variety of appropriate silvicultural treatments focused on regeneration. Individual, group, or patch selection systems can regeneration tolerant to mid-tolerant species (Ronco et al. 1983). Larger open areas may be necessary to regenerate and recruit shade intolerant species to the canopy. Large canopy opening where ponderosa pine and aspen regenerate may have be caused by patchy crown fires in the pre-fire suppress era (Touchan et al. 1996, Fulé et al. 2003). Groups or patches can be focused on particularly dense or stagnating areas within the stand or areas of bark beetle or budworm impact (Ronco et al. 1983). Refereces ^ Alexander, B. G., Jr, F. Ronco, Jr , E. L. Fitzhugh, and J. Ludwig. 1984. A Classification of Forest Habitat Types of the Lincoln National Forest, New Mexico. USDA Forest Service, Rocky Mountain Experiment Station, Fort Collins, CO.
Conklin, D. A. 2004. Development of the White Pine Blister Rust Outbreak in New Mexico. R3-04-01, USDA Forest Service, Southwestern Region Forestry and Forest Health, Albuquerque, NM.
http://www.fs.fed.us/r3/publications/documents/wp_blister_rust_nm.pdf Covington, W. W., M. M. Moore, P. Z. Fulé, and H. B. Smith. 1998. Grand Canyon forest ecosystem restoration: Report on pre-treatment measurements of experimental blocks. Division of Resource Management, Grand Canyon National Park., Grand Canyon, AZ.
Dahms, C. W., and B. W. Geils, editors. 1997. An assessment of forest ecosystem health in the Southwest. U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO.
http://www.rms.nau.edu/publications/rm_gtr_295/ chapter6.html#3 Dieterich, J. H. 1983. Fire history of southwestern mixed-conifer: a case study. Journal of Forest Ecology and Management 6(1):13-31.
Evans, A. 2006. What is ecological forestry? Forest Guild, Santa Fe, NM.
Fellin, D. G., and J. E. Dewey. 1992. Western Spruce Budworm. USDA Forest Service, Forest Insect & Disease Leaflet 53.
http://www.na.fs.fed.us/spfo/pubs/fidls/westbw/fidl-wbw.htm Ffolliott, P. F., and D. B. Thorud. 1977. Water resources and multiple-use forestry in the Southwest. Journal of Forestry 75(8):469-472.
http://www.ingentaconnect.com/content/saf/jof/1977/00000075/00000008/art00008 Filip, G. M., J. S. Beatty, and R. L. Mathiasen. 2000. Fir dwarf mistletoe. USDA Forest Service, Forest Insect & Disease Leaflet 89.
http://www.fs.fed.us/r6/nr/fid/fidls/firdm.pdf Fulé, P. Z., J. E. Crouse, T. A. Heinlein, M. M. Moore, W. W. Covington, and G. Verkamp. 2003. Mixed-severity fire regime in a high-elevation forest of Grand Canyon, Arizona, USA. Landscape Ecology 18(5):465-486.
http://dx.doi.org/10.1023/A:1026012118011 Geils, B. W., J. E. Lundquist, J. E. Negron, and J. S. Beatty. 1995. Disturbance Regimes and Their Relationships to Forest Health. Pages 246 in L. G. Eskew, editor. National Silviculture Workshop: Forest health through silviculture. USDA Forest Service, Rocky Mountain Research Station, RM-GTR-267, Mescalero, NM.
http://www.fs.fed.us/rm/pubs_rm/rm_gtr267/rm_gtr267_067_073.pdf Gorman, T., D. Lynch, and K. Mackes. 1999. Report on the test results for Colorado White Fir (Abies concolor). US Forest Service, Pagosa Springs, CO.
http://www.colostate.edu/programs/cowood/New_site/Publications/Articles/Gorman.pdf Grissino-Mayer, H. D., C. H. Baisan, and T. W. Swetnam. 1995. Fire history in the Pinaleño Mountains of southeastern Arizona: effects of human-related disturbances. USDA Forest Service, General Technical Report RM-GTR-264, Fort Collins, Co.
Heinlein, T. A., W. W. Covington, P. Z. Fulé, M. M. Moore, and H. B. Smith. 1999. Development of ecological restoration experiments in fire adapted forests at Grand Canyon National Park. Pages 381 in D. N. Cole, S. F. McCool, W. T. Borrie, and J. O'Loughlin, editors. Wilderness science in a time of change conference-Volume 5: Wilderness ecosystems, threats, and management. USDA Forest Service, Rocky Mountain Research Station, RMRS-P-15-VOL-5., Missoula, MT.
http://www.fs.fed.us/rm/pubs/rmrs_p015_5.html Johnson, M. 1994. Changes in Southwestern forests: Stewardship implications. Journal of Forestry 92(12):16-19.
Knapp, E. E., and J. E. Keeley. 2006. Heterogeneity in fire severity within early season and late season prescribed burns in a mixed-conifer forest. International Journal of Wildland Fire 15(1):37-45.
Lynch, A. M. 2004. Fate and characteristics of Picea damaged by Elatobium abietinum (Walker) (Homoptera: Aphididae) in the White Mountains of Arizona. Western North American Naturalist 64(1):7-17.
Mathiasen, R. L. 1979. Distribution and effect of dwarf mistletoes parasitizing Pinus strobiformis in Arizona, New Mexico, and northern Mexico. Southwestern Naturalist 24(3):455-461.
Mathiasen, R. L., F. G. Hawksworth, and C. B. Edminster. 1990. Effects of dwarf mistletoe on growth and mortality of Douglas-fir in the southwest. Great Basin Naturalist 50(2):173-179.
http://contentdm.lib.byu.edu/ Moir, W. H., and J. A. Ludwig. 1979. A classification of spruce-fir and mixed conifer habitat types of Arizona and New Mexico. RM-207, USDA Forest Service, Rocky Mountain Research Station, Fort Collins, CO.
Ronco, F., Jr , G. Gottfried, and R. Shaffer. 1983. Southwestern Mixed Conifers. in R. Burns, editor. Silvicultural systems for the major forest types of the United States. USDA Forest Service.
Ryerson, D. E., T. W. Swetnam, and A. M. Lynch. 2003. A tree-ring reconstruction of western spruce budworm outbreaks in the San Juan Mountains, Colorado, U.S.A. Canadian Journal of Forest Research 33(6):1010-1028.
http://search.ebscohost.com/login.aspx?direct=true&db=aph&AN=9991853&site=ehost-live Savage, M. 1997. The Role of Anthropogenic Influences in a Mixed-Conifer Forest Mortality Episode. Journal of Vegetation Science 8(1):95-104. weblink Smith, D. M., B. Larson, M. Kelty, and P. M. S. Ashton. 1997. The practice of silviculture : Applied forest ecology, 9th edition. John Wiley and Sons, New York, NY.
Touchan, R., C. D. Allen, and T. W. Swetnam. 1996. Fire history and climatic pattens in ponderosa pine and mixed-conifer forests of the Jemez Mountains, northern New Mexico. Pages 33-46 in C. D. Allen, editor. Fire Effects in Southwestern forests: Proceedings of the Second La Mesa Fire Symposium. USDA Forest Service General Technical Report RM-286, Fort Collins, CO.
US Forest Service. 2006. Fire Effects Information System. USDA Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.
http://www.fs.fed.us/database/feis%20Webb, J. 2003. High County Ranch: Fire History. Forest Stewardship Concepts Ltd., Monte Vista, CO.
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