Heather D. Alexander
A5015632890- Fire effects on ecosystems
- Climate change and permafrost
- Tree-ring climate responses
- Rangeland and Wildlife Management
- Ecology and Vegetation Dynamics Studies
- Forest ecology and management
- Plant Water Relations and Carbon Dynamics
- Geology and Paleoclimatology Research
- Cryospheric studies and observations
- Peatlands and Wetlands Ecology
- Seedling growth and survival studies
- Atmospheric and Environmental Gas Dynamics
- Geological Studies and Exploration
- Forest Ecology and Biodiversity Studies
- Coastal wetland ecosystem dynamics
- Indigenous Studies and Ecology
- Hydrology and Watershed Management Studies
- Soil erosion and sediment transport
- Remote Sensing and LiDAR Applications
- Soil Carbon and Nitrogen Dynamics
- Remote Sensing in Agriculture
- Animal Ecology and Behavior Studies
- Polar Research and Ecology
- Botany, Ecology, and Taxonomy Studies
- Methane Hydrates and Related Phenomena
Auburn University
2020-2025
Mississippi State University
2015-2021
University of Florida
2011-2021
Woodwell Climate Research Center
2019
Brownsville Public Library
2012-2015
University of Kentucky
2006-2015
The University of Texas at Austin
2006-2014
As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release offset by increased production Arctic boreal biomass; however, lack robust estimates net balance increases risk further overshooting international emissions targets. Precise empirical or model-based assessments critical factors driving are unlikely in near future, so address gap, we present from 98...
In boreal forests, climate warming is shifting the wildfire disturbance regime to more frequent fires that burn deeply into organic soils, releasing sequestered carbon atmosphere. To understand destabilization of storage, it necessary consider these effects in context long-term ecological change. Alaskan we found shifts dominant plant species catalyzed by severe fire compensated for greater combustion soil over decadal time scales. Severe burning soils shifted tree dominance from...
Significance Black spruce is the dominant tree species in boreal North America and has shaped forest flammability, carbon storage, other landscape processes over last several thousand years. However, climate warming increases wildfire activity may be undermining its ability to maintain dominance, shifting forests toward alternative forested nonforested states. Using data from across America, we evaluate whether loss of black resilience already widespread. Resilience was most common outcome,...
Abstract Circum-boreal and -tundra systems are crucial carbon pools that experiencing amplified warming at risk of increasing wildfire activity. Changes in activity have broad implications for vegetation dynamics, underlying permafrost soils, ultimately, cycling. However, understanding effects on biophysical processes across eastern Siberian taiga tundra remains challenging because the lack an easily accessible annual fire perimeter database underestimation area burned by MODIS satellite...
Prescribed fires are increasingly implemented throughout eastern deciduous forests to accomplish various management objectives, including maintenance of oak-dominated (Quercus spp.) forests. Despite a regional research-based understanding prehistoric and historic fire regimes, parallel contemporary use preserve oak is only emerging, with somewhat inconsistent results. For prescribed be effective, they must positively influence regeneration at one or more critical life stages: pollination,...
Abstract Climate warming and drying are modifying the fire dynamics of many boreal forests, moving them towards a regime with higher frequency extreme years characterized by large burns high severity. Plot‐scale studies indicate that increased burn severity favors recruitment deciduous trees in initial following fire. Consequently, set biophysical effects on postfire successional trajectories at decadal timescales have been hypothesized. Prominent among these greater cover tree species...
Abstract Pyrophytic oak landscapes across the central and eastern United States are losing dominance as shade-tolerant, fire-sensitive, or opportunistic tree species encroach into these ecosystems in absence of periodic, low-intensity surface fires. Mesophication, a hypothesized process initiated by intentional fire exclusion which encroaching progressively create conditions favorable for their own persistence at expense pyrophytic species, is commonly cited causing this structural...
Abstract The majority of variation in six traits critical to the growth, survival and reproduction plant species is thought be organised along just two dimensions, corresponding strategies size resource acquisition. However, it unknown whether global trait relationships extend climatic extremes, if these interspecific are confounded by within species. We test cold extremes life on Earth using largest database tundra yet compiled. show that plants demonstrate remarkably similar economic...
Abstract Climate change is intensifying the fire regime across Siberia, with potential to alter carbon combustion and post‐fire re‐accumulation trajectories. Few field‐based estimates of severity (e.g., tree mortality) exist in Siberian larch forests ( Larix spp.), which limits our ability project how an intensified will affect regional global climate feedbacks. Here, we present fire‐induced mortality loss eastern forests. Our results suggest that fires this region result high (means 83% 76%...
Fire suppression has facilitated the spread of red maple ( Acer rubrum L.), a fire-sensitive, yet highly adaptable species, in historically oak-dominated forests eastern United States. Here, we address whether shift from upland oaks to could influence forest hydrology and nutrient availability because species-specific effects on precipitation distribution inorganic nitrogen (N) cycling. In Kentucky, measured seasonal variations maple, chestnut oak Quercus montana Willd.), scarlet coccinea...
Ongoing changes in disturbance regimes are predicted to cause acute ecosystem structure and function coming decades, but many aspects of these predictions uncertain.A key challenge is improve the predictability post-disturbance biogeochemical trajectories at level.Both ecologists paleoecologists have generated complementary datasets about (type, severity, frequency) response (net primary productivity, nutrient cycling) spanning decadal multi-millennial timescales.Here, we take first steps...
Abstract Motivation The Tundra Trait Team (TTT) database includes field‐based measurements of key traits related to plant form and function at multiple sites across the tundra biome. This dataset can be used address theoretical questions about strategy trade‐offs, trait–environment relationships environmental filtering, trait variation spatial scales, validate satellite data, inform Earth system model parameters. Main types variable contained contains 91,970 18 traits. most frequently...
Fire frequency and severity are increasing in tundra boreal regions as climate warms, which can directly affect feedbacks by carbon (C) emissions from combustion of the large soil C pool indirectly via changes vegetation, permafrost thaw, hydrology, nutrient availability. To better understand direct indirect effects changing fire regimes northern ecosystems, we examined how differences burn (i.e., extent organic matter combustion) C, nitrogen (N), phosphorus (P) availability microbial...
In arctic tundra and boreal forest ecosystems vegetation structural functional influences on the surface energy balance can strongly influence permafrost soil temperatures. As such, changes will likely play an important role in carbon dynamics associated climate feedbacks. Processes that lead to vegetation, such as wildfire or ecosystem responses rising temperatures, are of critical importance understanding impacts future climate. Yet these processes vary within between this variability has...
Fire activity in boreal forests has increased recently with climate warming, altering stand structure and composition many areas. Changes dynamics have the potential to alter C cycling biophysical processes, feedbacks global regional climate. Here, we assess interactions between fire, structure, aboveground accumulation storage within of interior Alaska, where fire severity is predicted shift forest from predominantly black spruce ( Picea mariana ) greater deciduous cover. We measured...
Abstract. Climate change and land-use activities are increasing fire activity across much of the Siberian boreal forest, yet climate feedbacks from forest disturbances remain difficult to quantify due limited information on biomass distribution, disturbance regimes post-disturbance ecosystem recovery. Our primary objective here was analyse post-fire accumulation Cajander larch (Larix cajanderi Mayr.) aboveground for a 100 000 km2 area open in far northeastern Siberia. In addition examining...