| Title |
Investigators | Department | Objectives | Approach Keywords | Progress Reports | Impact Statements | Publications | |
Project * COL00535 | |
| Title | *Forest Conditions in The Rockies: Leopold, Fire, and Aspen |
| Investigator(s) | Binkley, DE; Burke, IC; |
| Department | Forest, Rangeland, & Watershed Sciences |
| Objectives | Our proposed project would initiate studies in 4 key areas that we have identified as current gaps in our knowledge for Rocky Mountain forests: 1) How does fire in a complex landscape influence soil nutrient supply and hydrophobicity? 2) What are the interactions among fire size, intensity, topographic variability, and other aspects of spatial complexity and how do they influence ponderosa pine re-establishment following fire? 3) How do fire and grazing in a complex landscape influence the invasion and persistence of the exotic annual, Bromus tectorum? 4) How does deer browsing on the Kaibab Plateau influence aspen recovery? |
| Approach | To examine the effects of fire and hydrophobicity, we will conduct a series of descriptive assessments of the effects of fire on soils, including: pre- and post-fire characterization of soils in prescribed fire areas; post-fire sampling in wildfire areas, stratified by levels of fire intensity; and repeated post-fire sampling to characterize soil recovery. To examine the interaction of fire size and forest recovery and Bromus tectorum invasion, we will identify a range of fires in ponderosa pine forests from the past several decades, from northern Arizona to the Front Range of Colorado, and characterize of tree regeneration and weed invasions. For the investigation of aspen, we propose a collaborative project to map the age distribution (using standard methods) of aspen on the Kaibab Plateau, with students and colleagues from Ft. Lewis College (Bill Romme) and Northern Arizona University (Margaret Moore). |
| Keywords | Fire ecology, Aspen, Ponderosa pine, Weeds, Soil hydrophobicity |
| Progress Reports | |
| 2001 | The first six months of this new project has focused on project implementation, and no results are available yet. Activities included field reconnaissance of the Kaibab Plateau and Front Range to determine optimal sampling designs for the coming field season. GS=1.75 |
| 2002 | The majority of the field sampling has been completed. Aspen comprise 14% of the basal area of the forests of the Kaibab Plateau, with no stands comprised of more than 40% aspen basal area. Preliminary data of aspen establishment support the idea of intensive deer browsing in the 1920's. GS=2 |
| 2003 | On the Kaibab Plateau, aspen structure was consistent with the classic story; the number of aspen dating (at 1.4 m) to the 1920s was an order of magnitude lower than the null expectation . Other periods of unusual numbers of aspen included high numbers of aspen dating to the 1880s and 1890s (coincident with the cessation of regular surface fires), low numbers of aspen dating to 1953 to 1962 (following a second irruption of the deer population), and very high numbers from 1968 to 1992 (coincident with widespread logging). Our study supports the idea of extreme deer herbivory in the 1920s, and the importance of predation in regulating deer populations on the Plateau was supported by patterns in deer population and hunting by humans later in the 20th Century. Although all available evidence is consistent with the classic story, some uncertainty remains. This level of ambiguity is common in case studies involving population ecology, land management, and people. A full version of the Kaibab deer story and its history would be a valuable case study for natural resource education. In the Front Range, aspen stands with conifer invasion showed no decrease in total basal area increment, whereas increment declined in stands without invasion. Maximum aspen growth related negatively to conifer basal area and basal area increment. Aspen mortality behaved independently of conifer invasion and was highly correlated with aspen density (r2 = 0.88, P=0.017). Conifer trees replace aspen via sub-canopy establishment and longevity rather than directly causing a decline in aspen growth or an increase in aspen mortality. Forest succession from aspen to conifer forests primarily occurs due to differential life history traits of the species involved, rather than species interactions. |
| 2004 | During the 20th Century, the lower and mid-elevation forests in the Rocky Mountains changed fundamentally in structure and composition. Aspen forests responded in a variety of ways to changes in fire regimes and browsing by wildlife and livestock. Changes in fire regimes altered the structure and composition of many ponderosa pine and mixed-conifer landscapes. These fundamental changes have led to unprecedented increases in risks to forest health. Our project has been examining several aspects of these changes, with a key focus on spatial and temporal patterns. A key component of this year's work has been characterizing spatial and temporal patterns in an intact, old-growth ponderosa pine forest in the Manitou Experimental Forest. This 9-ha stand has been stem mapped and remeasured at decadal intervals since the 1970s. Our research revealed that the current stand density of 400 trees/ha was double that of 1860 (before Euro-American settlement), representing an increase in basal area of about 30%. Both fire and climate historically influenced tree establishment, and stand structure also played a major role in the location and timing of regeneration events. The patchy process of regeneration resulted in spatial independence and some segregation of size classes. Large (40-55 cm dbh), old trees exhibited some regularity in their spatial distribution at short distances. Contemporary patterns of mortality were mostly patchy, possibly as a result of density-dependent mortality as well as disease. The growth of individual trees depended in large part on the number and size of neighboring trees, with the greatest influence of trees within 14 m of the focal tree. The supply of soil N influenced tree growth at very small scales (< 2 m), but the effect of N was swamped by the effects of competition at larger scales . Although the natural processes driving them have changed considerably, both establishment and mortality have retained spatial patterns that are at least consistent with pre-settlement forests, and that may help to preserve elements of the heterogeneous structure attributed to historical ponderosa pine forests. |
| 2005 | A. Invasive, exotic species are now one of the major land management issues in the western United States. Invading species are intimately associated with fire regimes and management activities (particularly livestock grazing), but these interactions remain poorly characterized, particularly for western forested landscapes. How does the spatial complexity of landscapes, including topography, soil fertility, fire history, and proximity to roads and other exotic seed sources, influence the success of invasive species? Understanding how these variables interact to influence the presence and success of exotics is crucial for determining which areas are susceptible to invasion and for making informed decisions about land use and exotic species management. B. During the 20th Century, the lower and mid-elevation forests in the Rocky Mountains changed fundamentally in structure and composition. Aspen forests responded in a variety of ways to changes in fire regimes and browsing by wildlife and livestock. Changes in fire regimes altered the structure and composition of many ponderosa pine and mixed-conifer landscapes. These fundamental changes have led to unprecedented increases in risks to forest health. Our project has been examining several aspects of these changes, with a key focus on spatial and temporal patterns. A. Exotic Species: We conducted several experiments to evaluate where invasive species are most successful in Colorado's Front Range. We found that the most important variable for predicting both exotic species richness was accessibility of the site from large population centers. Exotic richness increased with increasing human accessibility. We also found that successful invasion of cheatgrass (Bromus tectorum) increases nitrogen cycling, which may generate feedbacks leading to persistence of cheatgrass. B. A key focus of this year's work has been on determining the age structure of aspen trees in Rocky Mountain National Park. Our previous work determined that most of the aspen stands in the Front Range had at least some successfully regenerated trees in the past 40 years, despite very high populations of elk. We cored a number of trees, which we are still aging at this point. The distribution of stem diameters indicates thus far that the number of stems younger than 40 years may be about 75% lower than the would be predicted by the pattern that developed over the previous 150 years. |
| 2006 | Our work spans two areas key to understanding forests of the Rockies: the interaction of fire , aspen, wildlife, and livestock, and human impacts on forests via invasive species and urbanization. During the 20th Century, the lower and mid-elevation forests in the Rocky Mountains changed fundamentally in structure and composition. Aspen forests responded in a variety of ways to changes in fire regimes and browsing by wildlife and livestock. Changes in fire regimes altered the structure and composition of many ponderosa pine and mixed-conifer landscapes. These fundamental changes have led to unprecedented increases in risks to forest health. Our project has been examining several aspects of these changes, with a key focus on spatial and temporal patterns. A key focus of this year's work has been on determining the age structure of aspen trees in Rocky Mountain National Park. Our previous work determined that most of the aspen stands in the Front Range had at least some successfully regenerated trees in the past 40 years, despite very high populations of elk. Exceptions to this general trend occurred only in areas of the heaviest, year-round use (such as Horseshoe and Moraine Parks). Based on the second year of intensive sampling, it appears that regeneration of aspen has remained relatively strong across the Park as whole despite high elk populations over the past 4 decades. The intensively used winter range is an exception to this overall trend, however, and aspen recruitment was dramatically lower in the past 4 decades than in earlier periods. Humans are having strong impacts on the structure of forests in the West, not only through logging, grazing, and fire suppression, but also through the expansion of suburban and urban settlements. We expanded our studies this year to include the assessment of the carbon storage capacity of urban forests in the Front Range. The Colorado Front Range is interesting as a set of semi-arid ecosystems that represent one of the most rapidly growing regions in the US. We modeled potential carbon storage in aboveground woody biomass for urban trees in the city of Fort Collins, Colorado. In our model potential carbon storage depends on species composition, tree density, and age distribution. These factors vary through time based upon the spatial and temporal distribution of human decisions. Our results suggest that the aboveground carbon pool in urban areas can reach values that compete with native forests in Colorado, and approach values within 30% of the most productive forests in Colorado. |
| Impact | |
| 2001 | The impacts of this project will include providing a clearer picture of the historic conditions of Colorado forests (including species composition, dynamics, and fire effects), and the current challenges we face in sustaining our forests (including the interactions of fire and exotic plant species, fire and aspen regeneration, and predator/prey relationships). |
| 2002 | The impacts of this project will include providing a clearer picture of the historic conditions of forests on the Kaibab Plateau (including species composition) and the current challenges we face in sustaining our forests (including the interactions of aspen regeneration with predator/prey relationships). |
| 2003 | In Rocky Mountain National Park, we now know that the decline of old aspen trees (>100 yr old) does not appear to be accelerated by the invasion of conifers; conifer invasion halts aspen reproduction, but does not reduce growth or longevity of established aspens. Therefore, concerns about the effects of conifer invasion on aspen stands can focus on the impacts of aspen recruitment, without major concern about early senescence of established aspen. On the Kaibab Plateau, our results demonstrated a marked increase in aspen following cessation of surface fires in 1880, a decline in aspen during the 1920s and 1930s (consistent with the classic story of deer population irruption), a second decline in aspen in the 1950s (following a second deer irruption), and a dramatic increase in aspen in the 1970s and 1980s as a result of a huge increase in logging of conifers. The three major impact conclusions are that low predation on deer does appear to allow deer irruptions; aspen recruitment is very sensitive to fire regimes (surface fires inhibit aspen); and widespread logging led to a widespread increase in aspen. |
| 2004 | The key impacts of this component of our project include verification that although this reference forest changed during the 20th Century, the changes were not as dramatic as found for ponderosa pine forests on other soils in other areas. The doubling of stem numbers and 1/3 increase in basal area may be within the historic range of variation, or marginally beyond this range. The forest still retained many of the key structural characteristics of historical forests, include spatial aggregation of trees, clumped patterns of mortality, and an all-age distribution of trees. Restoration treatments may be useful in stands of this type, but other areas that demonstrated major changes in the 20th Century should have a higher priority. |
| 2005 | A. Exotic Species: These three studies on exotic species will aid land managers by describing the extent and success of exotic species along the Front Range, but also by identifying the processes and abiotic factors that may increase the susceptibility of an area to exotic invasions (e.g., human disturbance, physical disturbance, or increases in nutrient and water availability). These results will allow managers to focus exotic species management and control efforts in areas that are most likely to have conditions that favor the successful establishment of exotics. B. Aspen:The key impacts of this component of our project include verification that the number of aspen stems established in the past 4 decades is probably much lower than would be expected based on historic trends. The paucity of new aspen trees probably relates to heavy browsing from elk, as the weather patterns were not unusual during this period, and the incidence of fire remained low for the entire 20th Century. |
| 2006 | Forest managers in the Rocky Mountain West need to have a solid understanding of what controls forest structure and recruitment, to make decisions that will provide for future sustainability of timber, grazing, and wildlife resources. Our results indicate that elk grazing does not generally limit aspen recruitment, except in the very most heavily grazed systems associated with winter range. Among the most important management priorities in the Rockies today are minimizing fire risk, minimizing invasive species, and maximizing carbon storage potential of Front Range Forests. Our recent results indicate that fuels treatment protocols that minimize nutrient availability during initial phases will decrease invasive species, particularly cheatgrass. Finally, many municipalities in the U.S. are beginning to develop carbon credit trading, and our results show that investments in urban forests along the Front Range have a strong potential for capturing significant carbon over several decades. |
| Publications | |
| 2002 |
Adair, E.C., and Binkley, D. 2002. Co-limitation of first year Fremont cottonwood seedlings by nitrogen and water. Wetlands 22:425-420. Augusto, L., Ranger, J., Binkley, D., and Rothe, A. 2002. Impact of several common tree species of European temperate forests on soil fertility. Annals of Forest Science 59:233-254. Binkley, D., Ryan, M.G., Stape, J.L., Barnard, H., and Fownes, J. 2002. Age-related decline in forest ecosystem growth: an individual-tree, stand-structure hypothesis. Ecosystems 5:58-67. Kaye, J., Binkley, D., Zou, X., and Parrotta, J. 2002. Non-labile 15Nitrogen retention beneath three tree species in a subtropical plantation. Soil Science Society of America Journal 66:612-619. Kaye, Margot. 2002. Forest ecology of quaking aspen in Rocky Mountain National Park: A landscape survey, a reconstruction, and a predictive model. PhD Dissertation, Colorado State University, Ft. Collins, CO. Resh, S., Binkley, D., and Parrotta, J. 2002. Greater soil carbon sequestration under nitrogen-fixing trees compared with Eucalyptus species. Ecosystems 5:217-231. Stape, Jose Luiz. 2002. Production ecology of clonal eucalyptus plantations in Northeastern Brazil. PhD Dissertation, Colorado State University, Ft. Collins, CO. Uowolo, Amanda. 2002. Successional development of riparian vegetation on the floodplains of the Green and Yampa Rivers, Colorado, USA. M.S. Thesis, Colorado State University, Ft. Collins , CO. |
| 2003 |
Andersen, D.C., S.M. Nelson, and D. Binkley. 2003. Flood flows, leaf breakdown, and plant-available nitrogen on a dryland river floodplain. Wetlands 23:180-189. Binkley, D. 2003. Seven decades of stand development in mixed and pure stands of conifers and nitrogen-fixing red alder. Canadian Journal of Forest Research 33: 2274-2279. Binkley, D., F. Singer, M. Kaye, and R. Rochelle. 2003. Influence of elk grazing on soil properties in Rocky Mountain National Park. Forest Ecology and Management 185: 239-247. Binkley, D., R. Senock, and K. Cromack, Jr. 2003. Phosphorus limitation on nitrogen fixation by Falcataria seedlings. Forest Ecology and Management 186:171-176. Binkley, D., R. Senock, S. Bird, and T. Cole. 2003. Twenty years of stand development in pure and mixed stands of Eucalyptus saligna and nitrogen-fixing Falcataria mollucana. Forest Ecology and Management 182:93-102. Binkley, D., U. Olsson, R. Rochelle, T. Stohlgren, and N. Nikolov. 2003. Structure, production and resource use in old-growth spruce/fir forests in the central Rocky Mountains, USA. Forest Ecology and Management 172:271-279. Giardina, C., M.G. Ryan, D. Binkley, and J. Fownes. 2003. Primary production and C allocation in relation to nutrient supply in an experimental tropical forest. Global Change Biology 9:1438-1450. Ice, G.,and D. Binkley. 2003. Variations in forest streamwater concentrations of nitrogen (N) and phosphorus (P): implications of EPAs proposed water quality criteria for nutrients. Journal of Forestry 101:21-28. Kaye, J., D. Binkley, and C. Rhoades. 2003. Non-labile soil nitrogen accumulation and flexible organic matter stoichiometry during primary floodplain succession. Biogeochemistry 63:1-22. Kaye, M.W., T.J. Stohlgren, and D. Binkley. 2003. Aspen structure and variability in Rocky Mountain National Park, Colorado, USA. Landscape Ecology 18:591-603. Peter Brown. 2003. PhD Dissertation. Fire, Climate, and Forest Structure in Black Hills Ponderosa Pine Forests, 149 pages. Yanai, R.D., S.V. Stehman, M.A. Arthur, C.E. Prescott, A.J. Friedland, T.G. Siccama, and D. Binkley. 2003. Detecting change in forest floor carbon. Soil Science Society of America Journal 67:1583-1593. |
| 2004 |
Adair, E.C., D. Binkley, and D.C. Andersen. 2004. Nitrogen accumulation and supply in riparian floodplain ecosystems along the Green and Yampa Rivers, Colorado. Oecologia 139:108-116. Adams, M.A., P. Ineson, D. Binkley, G. Cadisch, N. Tokuchi, M. Scholes, K. Hicks, and M. Chadwick. 2004. Soil functional responses to excess N inputs at global scales. Ambio 33:530-536. Binkley, D. 2004. A hypothesis about the interaction of tree dominance and stand production through stand development. Forest Ecology and Management 190:265-271. Binkley, D., C.S. White, and J.R. Gosz. 2004. Tree biomass and net increment in an old aspen forest in New Mexico. Forest Ecology and Management 203:407-410. Binkley, D., G.G. Ice, J. Kaye, and C.A. Williams. 2004. Patterns of variation in nitrogen and phosphorus concentrations in forest streams of the United States. Journal of the American Water Association 2004:1277-1291. Binkley, D., J. Kaye, M. Barry, and M.G. Ryan. 2004. First rotation changes in soil carbon and nitrogen in a Eucalyptus plantation in Hawaii. Soil Science Society of America Journal 68: 1713-1719. Binkley, J.L. Stape, and M. Ryan. 2004. Thinking about resource use efficiency in forests. Forest Ecology and Management 193:5-16. Giardina, G.P., D. Binkley, M.G. Ryan, and J.H. Fownes. 2004. Belowground carbon cycling in a humid tropical forest decreases with fertilization. Oecologia 139:545-550. Ryan, M.G., D. Binkley, J. Fownes, C. Giardina, and R. Senock. 2004. An experimental test of the causes of age-related decline in forest growth. Ecological Monographs 74:393-414. Schoenecker, K.A., F.J. Singer, L.C. Zeigenfuss, D. Binkley, and R.S.C. Menezes. 2004. Effects of elk herbivory on vegetation and nitrogen processes. Journal of Wildlife Management 68:835-847. Stape, J.L, M.G. Ryan, and D. Binkley. 2004. Testing the 3-PG process-based model to simulate Eucalyptus growth with an objective approach to the soil fertility rating parameter. Forest Ecology and Management 193:219-234. Stape, J.L., D. Binkley, and M.G. Ryan. 2004. Eucalyptus production and the supply, use and the efficiency of use of water, light and nitrogen across a geographic gradient in Brazil. Forest Ecology and Management 193:17-31. Stape, J.L., D. Binkley, M.G. Ryan, and A.N. Gomes. 2004. Water use, water limitation, and water use efficiency in a Eucalyptus plantation. Bosque 25:35-41. Starr, Banning. 2004. Effects of clearcutting on chemistry of subsurface flow in a subalpine forest. M.S. Thesis, Colorado State University. 33p. |
| 2005 |
Adair, Carol. 2005. Causes and Consequences of Exotic Species Invasion in the Ponderosa Pine Forests of Colorado's Front Range. Ph.D. Thesis. Dept. of Forest, Rangeland and Watershed Stewardship, Colorado State Univesity. Fort Collins, CO. Binkley, D., and O. Menyailo (eds). 2005. Tree Species Effects on Soils: Implications for Global Change. NATO Science Series, Springer, Dordrecht. Boyden, S., D. Binkley, and R. Senock. 2005. Competition and facilitation between Eucalyptus and nitrogen-fixing Falcataria in relation to soil fertility. Ecology 86:992-1001. Boyden, S., D. Binkley, and W. Shepperd. 2005. Spatial and temporal patterns in structure, regeneration, and mortality of an old-growth ponderosa pine forest in the Colorado Front Range . Forest Ecology and Management 219:43-55. Boyden, Suzanne. 2005. Spatial patterns in forests and tree growth. Ph.D. Thesis. Dept. of Forest, Rangeland and Watershed Stewardship, Colorado State Univesity. Fort Collins, CO. Kaye, J.P., R.L. McCulley, and I.C. Burke. 2005. Carbon fluxes, nitrogen cycling and soil microbial communities in adjacent urban, native and agricultural ecosystems. Global Change Biology 11:575-587. Kaye, M.W., D. Binkley, and T.J. Stohlgren. 2005. Long-term impacts of conifer invasion and elk browsing on quaking aspen forests in the central Rocky Mountains, USA. Ecological Applications 15:1284-1295. Uowolo, A.L., D. Binkley, and E.C. Adair. 2005. Plant diversity in riparian forests in northwest Colorado: effects of time and river regulation. Forest Ecology and Management 218:107-114. |
| 2006 |
Stape, J.L., D. Binkley, W.S. Jacob, and E.N. Takahashi. 2006. A twin-plot approach to determine nutrient limitation and potential productivity in Eucalyptus plantations at landscape scales in Brazil. Forest Ecology and Management 223:358-362. Adair, E. Carol. PhD Dissertation (supported by McIntire Stennis). Causes and Consequences of Exotic Species Invasion in the Ponderosa Pine Forests of Colorados Front Range 2006 Binkley, D. 2006. Soils in ecology and ecology in soils. Chapter 10 (pp. 259-278) in: Footprints in the Soil: People and Ideas in Soil History (B. Warkentin, ed.), Elsevier, Amsterdam. Binkley, D., D.M. Kashian, S. Boyden, M.W. Kaye, J.B. Bradford, M.A. Arthur, P.J. Fornwalt, and M.G. Ryan. 2006. Patterns of Growth Dominance in Forests of the Rocky Mountains, USA. Forest Ecology and Management, 236:193-201. Binkley, D., J.L. Stape, E.N Takahashi, and M.G. Ryan. 2006. Tree-girdling to separate root and heterotrophic respiration in two Eucalyptus stands in Brazil. Oecologia 148:447-454. Binkley, D., M. Moore, W. Romme, and P. Brown. 2006. Was Aldo Leopold right about the Kaibab deer herd? Ecosystems 9: 227-241. DeCant, Josepth. MS thesis (partially supported by McIntire Stennis): The influence of Russian olive, Elaeagnus angustifolia L., on soil nitrogen dynamics along the Rio Grande River, Albuquerque, NM 2006 Hogberg, P., H.B. Fan, M. Quist, D. Binkley, and C.O. Tamm. 2006. Tree growth and soil acidification in response to 30 years of experimental nitrogen loading on boreal forest. Global Change Biology 12:489-499. |