Physical Sciences and Mathematics Commons^™

Data From: Forest Density Intensifies The Importance Of Snowpack To Growth In Water-Limited Pine Forests, Kelly E. Gleason, John B. Bradford, Anthony W. D’Amato, Shawn Fraver, Brian J. Palik, Michael A. Battaglia

Environmental Science and Management Datasets

Research Study
Warming climate and resulting declines in seasonal snowpack have been associated with drought stress and tree mortality in seasonally snow-covered watersheds worldwide. Meanwhile, increasing forest density has further exacerbated drought stress due to intensified tree-tree competition. Using a uniquely detailed dataset of population-level forest growth (n=2495 sampled trees), we examined how inter-annual variability in growth relates to snow volume across a range of forest densities (e.g., competitive environments) in sites spanning a broad aridity gradient across the United States. Forest growth was positively related to snowpack in water-limited forests located at low latitude, and this relationship was intensified …

Quantitative And Qualitative Approaches To Assess Tree Vigor And Stand Health In Dry Pine Forests, Nancy Grulke, Craig Bienz, Kate Hrinkevich, Jason Maxfield, Kellie Uyeda

Biology Faculty Publications and Presentations

Despite a critical need to evaluate effectiveness of forest treatments in improving stand health, practitioners lack quantitative, repeatable metrics to assess tree vigor and stand health. We evaluated canopy and whole tree attributes of ponderosa pine (Pinus ponderosa Dougl. Ex Laws) related to carbon balance, water balance, and susceptibility to insects and pathogens in dry, pine-dominated forest stands during a multi-year drought, an environmental challenge to stand resilience. Metrics of trees in two unmanaged, and seven treated forested stands, in both uplands and lowlands to develop the quantitative approach. Whole tree and crown attributes including needle length and color, branchlet …

A Landscape Model Of Variable Social-Ecological Fire Regimes, Robert M. Scheller, Alec M. Kretchun, Todd J. Hawbaker, Paul D. Henne

Environmental Science and Management Faculty Publications and Presentations

Fire regimes are now recognized as the product of social processes whereby fire on any landscape is the product of human-generated drivers: climate change, historical patterns of vegetation manipulation, invasive species, active fire suppression, ongoing fuel management efforts, prescribed burning, and accidental ignitions. We developed a new fire model (Social-Climate Related Pyrogenic Processes and their Landscape Effects: SCRPPLE) that emphasizes the social dimensions of fire and enables simulation of fuel-treatment effects, fire suppression, and prescribed fires. Fire behavior was parameterized with daily fire weather, ignition, and fire-boundary data. SCRPPLE was initially parameterized and developed for the Lake Tahoe Basin (LTB) …

Four-Fold Increase In Solar Forcing On Snow In Western U.S. Burned Forests Since 1999, Kelly E. Gleason, Joseph R. Mcconnell, Monica M. Arienzo, Nathan Chellman, Wendy M. Calvin

Environmental Science and Management Faculty Publications and Presentations

Forest fires are increasing across the American West due to climate warming and fire suppression. Accelerated snow melt occurs in burned forests due to increased light transmission through the canopy and decreased snow albedo from deposition of light-absorbing impurities. Using satellite observations, we document up to an annual 9% growth in western forests burned since 1984, and 5 day earlier snow disappearance persisting for >10 years following fire. Here, we show that black carbon and burned woody debris darkens the snowpack and lowers snow albedo for 15 winters following fire, using measurements of snow collected from seven forested sites that …

Interactions Among Fuel Management, Species Composition, Bark Beetles, And Climate Change And The Potential Effects On Forests Of The Lake Tahoe Basin, Robert M. Scheller, Alec M. Kretchun, E. Louise Loudermilk, Matthew D. Hurteau, Peter J. Weisberg, Carl Skinner

Environmental Science and Management Faculty Publications and Presentations

Climate-driven increases in wildfires, drought conditions, and insect outbreaks are critical threats to forest carbon stores. In particular, bark beetles are important disturbance agents although their long-term interactions with future climate change are poorly understood. Droughts and the associated moisture deficit contribute to the onset of bark beetle outbreaks although outbreak extent and severity is dependent upon the density of host trees, wildfire, and forest management. Our objective was to estimate the effects of climate change and bark beetle outbreaks on ecosystem carbon dynamics over the next century in a western US forest. Specifically, we hypothesized that (a) bark beetle …

Bending The Carbon Curve: Fire Management For Carbon Resilience Under Climate Change, E. Louise Loudermilk, Robert M. Scheller, Peter J. Weisberg, Alec M. Kretchun

Environmental Science and Management Faculty Publications and Presentations

Context: Forest landscapes are increasingly managed for fire resilience, particularly in the western US which has recently experienced drought and widespread, high-severity wildfires. Fuel reduction treatments have been effective where fires coincide with treated areas. Fuel treatments also have the potential to reduce drought-mortality if tree density is uncharacteristically high, and to increase long-term carbon storage by reducing high-severity fire probability.

Objective: Assess whether fuel treatments reduce fire intensity and spread and increase carbon storage under climate change.

Methods: We used a simulation modeling approach that couples a landscape model of forest disturbance and succession with an ecosystem model of …

Competition Amplifies Drought Stress In Forests Across Broad Climatic And Compositional Gradients, Kelly E. Gleason, John B. Bradford, Alessandra Bottero, Anthony W. D'Amato, Shawn Fraver, Brian J. Palik, Michael A. Battaglia, Louis Iverson, Laura Kenefic, Christel C. Kern

Environmental Science and Management Faculty Publications and Presentations

Forests around the world are experiencing increasingly severe droughts and elevated competitive intensity due to increased tree density. However, the influence of interactions between drought and competition on forest growth remains poorly understood. Using a unique dataset of stand-scale dendrochronology sampled from 6405 trees, we quantified how annual growth of entire tree populations responds to drought and competition in eight, long-term (multi-decadal), experiments with replicated levels of density (e.g., competitive intensity) arrayed across a broad climatic and compositional gradient. Forest growth (cumulative individual tree growth within a stand) declined during drought, especially during more severe drought in drier climates. Forest …

Restoring Surface Fire Stabilizes Forest Carbon Under Extreme Fire Weather In The Sierra Nevada, Daniel J. Krofcheck, Matthew D. Hurteau, Robert M. Scheller, E. Louise Loudermilk

Environmental Science and Management Faculty Publications and Presentations

Climate change in the western United States has increased the frequency of extreme fire weather events and is projected to increase the area burned by wildfire in the coming decades. This changing fire regime, coupled with increased high-severity fire risk from a legacy of fire exclusion, could destabilize forest carbon (C), decrease net ecosystem exchange (NEE), and consequently reduce the ability of forests to regulate climate through C sequestration. While management options for minimizing the risk of high-severity fire exist, little is known about the longer-term carbon consequences of these actions in the context of continued extreme fire weather events. …