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Browsing by Author "Binkley, Daniel, advisor"

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    Aspen forests on the Uncompahgre Plateau: current and future expectations
    (Colorado State University. Libraries, 2012) Alsanousi, Attia A. Mussa, author; Binkley, Daniel, advisor; Smith, Frederick W., committee member; Sibold, Jason S., committee member
    Dynamic changes in aspen cover on the Uncompahgre Plateau have raised concerns among researchers and communities about the stability and long-term survivorship of aspen forests. In the summer of 2010, aspen increment cores were measured for current age distribution from sixty-three random locations across the Plateau including pure aspen and mixed conifer- aspen stands, to provide insights about aspen forests in the near future. Most of aspen trees on the Plateau in 2010 were 100 to 130 years old, and having established after the last major landscape-scale fire in 1879. Trees older than 140 years accounted for about 2% of all stems, with the oldest tree in our random sample being 272 years at breast height. Aspen cover will likely decline over the next five decades, as young cohorts (<80 years) have fewer stems than older cohorts (100- 130 years). Several ecological processes or events could accelerate aspen decline, including conifer replacement of aspens in mixed stands and severe drought. The three survivorship scenarios showed that the reduction in aspen cover by 2060 will likely vary from about 40% of current aspen cover in the most optimistic scenario to a 84% reduction in a higher mortality scenario. The Plateau currently has abundant numbers of aspen suckers, but few of these escape browsing pressure to become trees. The aspen decline predicted in the scenarios may continue beyond 2060 if recruitment remains low, or could be turned around if widespread disturbance regenerates forests, or if browsing pressure drops substantially.
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    Carbon and nitrogen eroded from burned forests in the western U.S.
    (Colorado State University. Libraries, 2013) Pierson, Derek, author; Binkley, Daniel, advisor; Rhoades, Charles, committee member; Kelly, Eugene, committee member
    Post-wildfire landscapes and downstream aquatic resources are influenced by carbon (C) and nitrogen (N) losses from soil erosion. As opposed to soil erosion, rarely measured losses of sediment C and N may account for a substantial portion of fire impacts. We measured erosion of C and N following eight wildfires for four to six years in the western U.S and compared losses from untreated, burned hillslopes and small catchments with those from adjacent areas that received erosion mitigation treatments. Losses of C, N and sediment were greatest the first two years and declined in subsequent years. Cumulative losses from untreated, burned areas were 16 - 4,700 kg C/ha and 0.7 - 185 kg N/ha over the study period. Across wildfire locations, median sediment C and N concentrations ranged from 0.011 - 0.036 g N/kg and 0.23 - 0.98 g C/kg. Post-fire erosion control treatments reduced C, N and sediment losses by 65-75% compared to untreated areas and generally increased the concentrations of C and N in eroded material. The total C and N lost in post-fire erosion was < 20% of the estimated amount lost from organic and mineral soil layers during combustion and < 5% of the estimated amount remaining in mineral soils after combustion. In general, the N lost with soil erosion is unlikely to impair the productivity of recovering forests, but the eroded N may have consequences on downstream water quality and aquatic habitat.
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    Ecosystem respiration and foliar morphology of a primary tropical rain forest: the effects of canopy structure and environmental gradients
    (Colorado State University. Libraries, 2007) Cavaleri, Molly A., author; Binkley, Daniel, advisor; Ryan, Michael, advisor
    Wood and foliage are major components of ecosystem respiration, but estimates of large-scale rates for tropical rain forests are uncertain because of poor sampling in the upper canopy and across landscapes. Carbon balance models often rely on leaf mass per area (LMA) because it correlates with many plant physiological parameters. Researchers have long assumed variation in LMA to be a response to light (sun/shade leaf dichotomy), but LMA also reflects increases in leaf density that result from decreasing water potential with height. We used a portable scaffolding tower to measure plant respiration, LMA, and light from ground level to the canopy top across 55 sites in a primary tropical rain forest in Costa Rica. The first objective of this study was to extrapolate woody CO2 efflux to the forest by characterizing its variation with canopy structure and landscape gradients. The second objective was to extrapolate foliar and total respiration to the forest by investigating the variation in foliar respiration with foliar parameters, canopy structure, and landscape gradients. The third objective was to determine whether LMA varied primarily because of light or water potential. Wood and foliage respiration rates increased with height and showed differences between plant functional groups. Wood respiration per unit ground area was 1.3 μmo1 CO2 M-2 s-1 and foliar respiration was 3.5 μmol CO2 m-2 s-1, representing 14% and 37% of total ecosystem respiration, respectively. Total ecosystem respiration (9.38 ± 1.43 μmol CO2 m-2 s-1) was 33% greater than eddy flux nighttime net ecosystem exchange for the same forest, suggesting that eddy flux studies reporting a large sink for tropical rain forests may be in error. We found LMA to be better related to height than light environment, supporting the hypothesis that the LMA gradient within forest canopies is primarily driven by a linear decrease in turgor pressure with height, caused by an increase in hydraulic resistance with gravity and longer path length. While light does affect LMA slightly, especially in the light-limited understory, the sun/shade leaf model taught in every plant physiology textbook is too simplistic to describe the large variation of LMA with vertical structure.
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    Empowering collaborative forest restoration with locally relevant ecological research
    (Colorado State University. Libraries, 2015) Matonis, Megan Shanahan, author; Binkley, Daniel, advisor; Battaglia, Mike A., committee member; Reid, Robin S., committee member; Schultz, Courtney A., committee member
    Collaborative forest restoration can reduce conflicts over natural resource management and improve ecosystem function after decades of degradation. Scientific evidence helps collaborative groups avoid undesirable outcomes as they define goals, assess current conditions, design restoration treatments, and monitor change over time. Ecological research cannot settle value disputes inherent to collaborative dialogue, but discussions are enriched by locally relevant information on pressing natural resource issues. I worked closely with the Uncompahgre Partnership, a collaborative group of managers, stakeholders, and researchers in southwestern Colorado, to develop research questions, gather data, and interpret findings in the context of forest restoration. Specifically, my dissertation (1) explored ways to better align collaborative goals with ecological realities of dynamic and unpredictable ecosystems; (2) defined undesirable conditions for fire behavior based on modeling output, published literature, and collaborative discussions about values at risk; (3) assessed the degree to which restoration treatments are moving forests away from undesirable conditions (e.g., homogenous and dense forests with scarce open habitat for grasses, forbs, and shrubs); and (4) looked at the validity of rapid assessment approaches for estimating natural range of variability in frequent-fire forests. The current practice of defining desired future conditions pulls managers and stakeholders into command-and-control thinking and causes them to dream away resource tradeoffs and the unpredictability of forest change. Instead, moving ecosystems away from undesirable states and reducing unacceptable risk might allow for diverse and socially acceptable conditions across forested landscapes. The concept of undesirable conditions helped the Uncompahgre Partnership come to agreement over types of fire behavior and stand conditions they wanted to avoid through management. I determined that restoration treatments on the Uncompahgre Plateau are generally moving forests away from undesirably dense conditions that were uncommon prior to Euro-American settlement. My assessment was largely based on data collected during collaborative workdays with the Uncompahgre Partnership. Our rapid assessment approach for estimating historical forest structure took a quarter of the time required for scientifically rigorous stand reconstructions, and it provided reasonably accurate estimates of tree density and spatial patterns. Our data on historical stand structure revealed that fragmentation and loss of open grass-forb-shrub habitat between tree groups were the most dramatic and undesirable changes occurring in frequent-fire forests over the past century. Many restoration treatments are focused on restoring spatial patterns in tree groups, with little attention to spatial patterns in open grass-forb-shrub habitat. I determined that the juxtaposition of tree groups with grass-forb-shrub habitat >6 m from overstory trees is important for restoring understory cover, diversity, and composition. Focusing on undesirable conditions in stands, such as high tree density and scarcity of grass-forb-shrub habitat, can help collaborative groups find common ground and design treatments that restore structure, composition, and processes in forest ecosystems.
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    Engelmann spruce and subalpine fir stand dynamics in north central Colorado
    (Colorado State University. Libraries, 2015) Derderian, Drew Phillip, author; Binkley, Daniel, advisor; Paschke, Mark, committee member; Rocca, Monique, committee member
    Stemwood biomass and production were measured in a 600-year chronosequence of stands consisting of Engelmann spruce and subalpine fir in the Colorado Front Range. The stands were part of a chronosequence established and measured in 1984. The original chronosequence showed near-constant biomass of spruce after approximately 250 years of development. Spruce production also had remained nearly constant after an initial rise and fall during the first 250 years. Fir biomass decreased more than that of spruce after around 150 years. Fir biomass remained at lower consistent sub-dominate values through the end of the chronosequence. Fir's high production from early stand development decreased and remained constant after approximately 175 years of development. Changes over the most recent 29 years did not follow the patterns in the 1984 chronosequence: spruce biomass dropped by 70% with little change in fir biomass. This resulted in a 47% average decrease in total stand biomass since 1984. Stand biomass showed no relationship with stand age. Spruce beetle-kill appeared to have played a major role in live biomass decline in all stands. Net increment was negative in fir as increases in fir production were more than offset by fir mortality. The stands investigated have developed from post-fire initiation and, although there was no evidence of subsequent major disturbance in 1984, severe beetle infestation since then has altered expected trends in spruce-fir forest structure. Stand age pattern projections will likely continue to be altered by disturbances and changing disturbance regimes.