Browsing by Author "Binkley, Dan, advisor"
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Item Open Access Competition from neighboring trees in eucalyptus monoculture and in mixed species native forest restoration plantations(Colorado State University. Libraries, 2012) Luu, Trung Canh, author; Binkley, Dan, advisor; Rocca, Monique, committee member; Laituri, Melinda, committee member; Kelly, Eugene F., committee memberCompetition has been recognized as a crucial factor in determining stand structure and productivity. However, competition is not a simple pattern. Its intensity and importance vary with structures of neighboring tree size and composition, and nutrient gradients. Our studies examined the influence of neighborhood uniformity on growth of individual trees in Eucalyptus monoculture, and competition between pioneer and non-pioneer species in mixed native species restoration plantations by developing a number of alternative neighborhood growth models. Our analyses showed that neighborhood uniformity of tree sizes had significant effects on growth of individual clonal Eucalyptus trees and these effects increased with increasing age of stand because stand and neighborhood tree size became less uniform with age. For competition from pioneer trees to non-pioneer trees, competition from neighboring trees had strong effects on the growth of individual non-pioneer trees, and the intensity of competition from neighboring trees varied with focal tree species guild and degrees of silviculture interventions. For example, non-pioneer legumes experienced competition as a function of neighboring tree sizes and distances only. Non-pioneer non-legumes experienced competition as a function of neighboring tree sizes and distances, and also by the identity of neighboring species guilds. The non-pioneer non-legumes experienced stronger competition in the intensive silviculture treatment, probably resulting from the neighboring species guild of pioneer non-legumes, unlike the non-pioneer legumes. Although intensive silviculture initially enhanced forest stand productivity (both density and tree size), strong competition from fast-growing lowered the later growth of individual non-pioneer trees. Our analyses suggested implications to: (i) increase and maintain stand uniformity to increase stand stem productivity and quality; and (ii) control strong, even exclusive completion in some cases from pioneer trees to non-pioneer trees through matching species to be mixed and managing their abundance.Item Open Access Drivers of conifer regeneration in severely burned ponderosa pine ā dominated forests of the Colorado Front Range(Colorado State University. Libraries, 2015) Chambers, Marin, author; Binkley, Dan, advisor; Fornwalt, Paula, advisor; Sibold, Jason, committee memberWildfires have increased in size and severity in ponderosa pine (Pinus ponderosa) ā dominated forests in recent decades, and the ability of ponderosa pine and other co-occurring conifers to regenerate in severely burned portions of such fires is unclear. I collected post-fire conifer regeneration and other data within and surrounding five 11 to 18 year-old Colorado Front Range wildfires to examine whether severely burned patches are regenerating, and how regeneration density in these patches is governed by biotic and abiotic factors. Data were collected in plots distributed along transects originating within surviving forest and extending into high severity burn areas, and in plots located outside the fire perimeters. My results indicate that conifers have regenerated in severely burned areas (mean density of 118 stems ha-1, 81% of which is ponderosa pine), but at densities that were more than five times lower than those in unburned and lightly to moderately burned areas. Generalized linear mixed model analyses revealed that as distance from surviving forest increased, conifer regeneration decreased; estimates of conifer regeneration were ~100 stems ha-1 50 m from surviving forest but <10 stems ha-1 ā„200 m from surviving forest. These analyses also identified elevation as an important predictor of conifer regeneration in high severity burn patches, with densities decreasing with decreasing elevation. Regression tree analyses likewise found distance from surviving forest and elevation to be important predictors of regeneration, where within 50 m of live trees mean regeneration was 150 stems ha-1 at elevations ā¤2490 m and 1120 stems ha-1 at elevations >2490 m, but at distances ā„50 m from live trees mean regeneration was 49 stems ha-1. Extrapolating my regression tree results to the 2002 Hayman Fire, 84% of the now unforested portion of this fire is predicted to have regeneration densities of 150 stems ha-1 or less. Taken as a whole, these findings suggest that activities such as tree planting may be warranted in high severity patches of Colorado Front Range wildfires if managers wish to return these areas to ponderosa pine ā dominated forest in the foreseeable future, particularly where surviving forest is not in close proximity or where elevation is low.Item Open Access Forest structure in unharvested old-growth: understanding the influence of soils on variability of long-term tree dynamics and fire history(Colorado State University. Libraries, 2013) Hasstedt, Steven C. M., author; Binkley, Dan, advisor; Rocca, Monique, committee member; Sibold, Jason, committee member; Martin, Patrick, committee memberWestern North American forests adapted to frequent fires have been fundamentally altered and fragmented as a result of fire exclusion, the transportation infrastructure, development patterns, and other landscape level changes. In order to enhance the resiliency, diversity, and productivity of forest ecosystems it is essential to encourage collaborative, science-based restoration of forest landscapes and to develop a public understanding of the dynamic nature of forests. The USDA's Collaborative Forest Landscape Restoration Program (CFLRP) provides guidelines for community stakeholders and private advocacy groups to engage with federal, state, and local agency stewards to develop monitoring and assessment goals for forest restoration projects. The Uncompahgre Plateau (UP) was identified as one of ten initial CFLRP locations nationwide and has very large, old heritage trees scattered across never-harvested areas within the National Forest boundaries. Understanding how soil depth influences fire behavior and canopy development and determining the nature of historical fire regime on the UP are key elements for the development of local forest restoration prescriptions. Heritage trees appeared to occur more often on rocky soils, and I expected this could result from different fire behavior in landscape patches where soils are too thin to support dense forest cover and fuels. I tested the influence of soil depth on forest composition and the fire history of the study area in three phases. First, I recorded soil depth and site characteristics for 80 randomly selected plots and included targeted site sampling of all heritage trees (ā„80 cm diameter) on two unroaded, never-harvested mesas to examine the relationship between soil depth, stand basal area, and the presence of heritage trees. The development of forest canopies (which influence fire regimes and tree survival) appeared to relate to soil characteristics (particularly rock cover). Single factor analysis revealed that soil depth alone only accounts for about 10% of stand basal area variation, but locations with soil > 30 cm deep had almost twice the basal area of locations with < 15 cm of soil depth. Comparing the observed to expected occurrence of heritage trees in four soil depth categories revealed a disproportionately greater presence of old-growth heritage trees on the locations with shallow soils. These results indicate that simple soil depth measurements can be used by restoration planners to develop stand-level spatial patterns. In the second phase, I used standard dendrochronology techniques to age trees from random plots, targeted heritage trees, and aspen transects to determine if historical stand structure patterns revealed forest age caps in concert with known landscape level historical fires. The spatial pattern of pre-1880 trees revealed that landscape level fires in the 1800s were likely not intense enough to kill all conifers over large areas, but were intense enough to kill most aspen stems on two of four sampled mesas. The mixed-severity nature of historical fires indicates that forest managers should have the leeway to plan for a spectrum of low to high severity fire effects within their restoration treatments. The third phase of my research tested the validity of my age-cap sampling methodology. I applied my sampling protocols to results from thirty systematic grid sampling locations composed of mixed conifer and spruce fir forests on the Kaibab Plateau, located on the North Rim of the Grand Canyon. My methodology targeted the largest trees and identified the oldest trees in the mixed conifer plots 97% of the time (in all but one plot). While a complete census of all trees would provide perfect information on the presence of an age cap, the validation of my targeted sampling approach provides a high confidence method to characterize the oldest trees in sampling locations with a substantial savings in the amount of time and resources expended. The subsequent ability to characterize the historical fire regime at the scale of the sampling design provides forest managers with another tool to inform restoration prescriptions. Applying the knowledge gained from the unroaded, never-harvested mesas to similar forest types on the Uncompahgre Plateau will guide landscape-scale treatment planning designed to restore ecosystem structure, composition, and function while reintegrating and managing wildfire as a natural component to reduce the risk of unnaturally severe crown fires.Item Open Access Patterns of growth dominance and neighborhood effects in eucalyptus plantations and tropical forests(Colorado State University. Libraries, 2008) Bui, Doi The, author; Binkley, Dan, advisor; Stohlgren, Thomas J., committee member; Steingraeber, David, committee member; Ryan, Michael G., committee memberForest stands have a broad range of tree sizes, even when all trees develop as a single cohort. Differences in size might result from different rates of resource uptake or resource use efficiency. Dominant trees often account for the majority of increment, but non-dominant trees can contribute a major part of stand growth in some cases. Pattern of growth dominance may provide predictive insight into the growth of trees and forest. My dissertation contains three chapters to explore growth dominance patterns of Eucalyptus plantations in Hawaii and Brazil, and natural tropical forests in Panama.Item Open Access Plant species effects on soil organic matter turnover and nutrient release in forests and grasslands(Colorado State University. Libraries, 1996) Scott, Neal Arthur, author; Binkley, Dan, advisor; Burke, Indy, committee member; Lauenroth, Bill, Ryan, Michael, committee memberAlthough feedbacks between plant species and ecosystem dynamics have been demonstrated in a variety of terrestrial ecosystems, little research has examined the mechanistic relationship between plant species characteristics, the formation and turnover of soil carbon and nitrogen pools, and ecosystem processes such as net N mineralization. My objective was to examine two possible effects of species on soil C and N dynamics; changes in organic matter quality and changes in soil aggregation. For several forest ecosystems, litter lignin:N ratio correlated negatively (non-linear) with net N mineralization, but the relationship did not apply to grass species. Climatic factors (temperature, precipitation) explained little of the variation in net N mineralization. The relationship between litter lignin:N ratio and net N mineralization from mineral soil and the forest floor was similar, suggesting that plant litter quality affects both forest floor and mineral soil organic matter quality. For tree species monocultures in Wisconsin, net N mineralization during 387 day laboratory incubations indicated that species alter the quality of readily decomposable pools of soil N, and have little effect on more recalcitrant soil N. Changes in the quality of soil N correlated positively with in situ net N mineralization. Grass species did not influence N mineralization. Neither grass nor tree species influenced soil C dynamics, but differences in soil characteristics between sites influenced soil C dynamics. Soil microbes appear to act as a ādecay filterā, converting heterogeneous plant material into relatively homogeneous soil humus. Changes in soil aggregate size distribution should alter whole-soil C and N quality because different size aggregates contain organic matter of different quality. Although tree species slightly altered aggregate size distribution, aggregate size distribution related poorly to whole-soil C and net N mineralization. Tree species had no effect on the physical protection of organic matter in soil aggregates or on organic matter quality of different size aggregates. Species characteristics had little effect on soil C mineralization, but species-related changes in the quality of readily decomposable soil N pools (not the pool size) influenced net N mineralization. This suggests that the feedbacks between plant species and soil N cycling occur rapidly, ensuring an adequate nutrient supply when plant community structure changes.Item Open Access Plant-soil-water relations in three contrasting environments(Colorado State University. Libraries, 2010) Gass, Tobah M., author; Binkley, Dan, advisor; Bauerle, William L. (William Leonard), 1972-, committee member; Knapp, Alan K., 1956-, committee member; Stromberger, Mary, committee memberThe relationships among soil nutrients, water availability, and vegetation can be studied over spatial and temporal scales that vary by orders of magnitude. Each provides a particular set of insights into tightly linked ecosystem dynamics. I examined the effects of rainfall on soil CO2-C efflux in a semi-arid woodland, the ramifications of ungulate herbivory for soil nutrients and microbial processes in a montane riparian zone, and the consequences of manipulating soil nutrient levels and vegetation density for carbon isotope discrimination in a wet tropical forest. Soil CO2-C efflux responded more strongly to a natural change in the timing and magnitude of precipitation that occurred during the study than to irrigation or drought treatments, indicating the importance of the timing of rainfall. Soil CO2-C efflux declined with artificial drought under trees and in open locations; the patterns and rates of the response differed between the two locations. Maximum efflux rates under trees occurred with supplemental irrigation; maximum rates in open locations occurred with ambient rainfall and artificial warming. Soil nutrient concentrations and quantities were significantly less than in paired plots that have been protected from grazing for 15 years. Low levels of nutrients were associated with higher bulk density and lower soil moisture in the grazed areas. Carbon isotopes from wood cellulose of trees in an experimental wet tropical forest were invariant across treatments, contrasting with significant treatment-related differences in gross primary production. I consider several reasons why discrimination might not co-vary with gross primary production, including decreased isotopic response when conductance is not limiting and the muting of signals in wood as compared to foliage. Each experiment reflected at least three years of treatment effects and included data ranging from the temporally and spatially integrated values of carbon isotopes from wood-tree rings and annual soil CO2-C efflux to the point processes captured by measurements of microbial biomass and fatty acids. Together, they demonstrate various sensitivities to environmental modifications that should increase our understanding of plant-soil-water relationships.Item Open Access Study on the growth of white bamboo (Dendrocalamus membranaceus Munro) under different ecological factors(Colorado State University. Libraries, 2009) Le, Truong Xuan, author; Binkley, Dan, advisorWhite bamboo is one of the most popular and valuable forest products in mountainous areas of Northern Vietnam. Long-term, sustainable management of white bamboo plantations will require improved knowledge about the ecological features of white bamboo in relation to growth. I examined patterns of bamboo growth and light interception in relation to topographic position and management intensity. I also determined how ecological factors relate to white bamboo growth, identifying possible nutrient limitation, and the efficiency of light use as a factor explaining growth patterns. Topographic position had strong effects on white bamboo growth. The differences between white bamboo growth on footslopes and hilltops were in total culm volume, DBH and height, and number of economically valuable culms. Management intensity had significant effects on DBH and height, total culm volume and culm wall volume as well as on dry culm mass. Pure intensive management had greatest white bamboo growth among the three management intensities. Topographic position significantly affected culm DBH, culm height, culm volume, and number of economically valuable culm light use efficiency. Management intensity affected culm DBH, culm height, culm volume, culm wall volume; and on dry culm mass light use efficiencies. Total culm volume correlated well with soil moisture. Culm wall volume had strong correlation with soil pH, and a moderate correlation with pH was also demonstrated by dry culm mass. The number of economically valuable culms correlated moderately with soil pH and cation exchange capacity. A fertilization experiment of 4 fertilizers (nitrogen, potassium, phosphate, and N+P+K) in 12 plots in Cau Hai showed a growth increase in response to N. In general, this study supported the hypothesis that topographic position and management intensity strongly influence white bamboo growth. There was a difference in white bamboo growth across four fertilizer experiments but the difference was only significant for nitrogen.Item Open Access The 2006 Warm Fire: effects on habitat and prey species of the northern goshawk(Colorado State University. Libraries, 2015) Lambert, Jeffrey S., author; Binkley, Dan, advisor; Reynolds, Richard, committee member; Savidge, Julie, committee memberReductions in the frequency of fire in Southwestern ponderosa pine and mixed-conifer forests since initiation of forest management early in 20th century changed the composition and structure of the forest habitats of the northern goshawks (Accipiter gentilis), a food-limited species of conservation concern, and the birds and mammals it feeds on. A conservation strategy for the species in the goshawk's food web in these forest types recommends restoring the mix of predator and prey habitats that historically characterized these forests--characteristics that were sustained by frequent low-severity surface fire. Thus, the effects of fire severities (high- and low-severity) and lack of fire on today's habitats may influence the abundances of bird and mammal goshawk prey. . The 2006 Warm Fire burned 235 kmĀ² of ponderosa pine and mixed-conifer forest on the North Kaibab Ranger District in northern Arizona in late June and early July 2006. Forest habitat metrics such as live tree and snag densities, cone production, canopy and ground cover estimates were collected from 2007-2010 on 60 0.5km transects to compare the effects of high- and low-severity fire and no fire on a suite of 13 important prey species of the goshawk. I describe habitat changes resulting from the different fire severities in ponderosa pine and mixed conifer forests. I estimated abundances for 13 bird and mammal prey species in forests burned by different fire severities and tested predictive models designed to gain an understanding which habitat characteristics, affected by fire, best predicted individual bird and mammal abundances. Red squirrels and golden-mantled ground squirrels showed the most sensitivity to fire, while chipmunks were evenly distributed across fire severities. Hairy woodpeckers and northern flickers, in contrast, benefitted from high-severity fire, due to increased snags, cavity nesting opportunities, and foraging. American robins and Steller's jays were also evenly distributed across fire severities. High-severity fire had a significant impact on forest ecosystems. Changes in forest structure were found to be detrimental to some species while creating short- and possibly intermediate-term benefits for others. Lowering the risk of high-severity fire by restoring composition and structure should also protect the habitats of goshawk and the prey species most sensitive to fire. The effects of low-severity fire were mixed, suggesting that it may be possible to return fire to ecosystem without a significant impact to many birds and mammals in the short term. Frequent low-severity fire could also help to maintain sub-canopy and understory grass / shrub openings by removing excess growth and ground debris.