Treesearch

The ambient atmospheric environment affects the growth and spread of wildland fires, whereas heat and moisture released from the fires and the reduction of the surface drag in the burned areas can significantly alter local atmospheric conditions. Observational studies on fire–atmosphere interactions have used instrumented towers to collect data during prescribed fires, but a few towers in an operational-scale burn plot (usually >103 m2) have made it extremely challenging to capture the myriad of factors controlling fire–atmosphere interactions, many of which exhibit strong spatial variabili...

Pitch pine (Pinus rigida Mill.) can be found across a broad range in eastern North America but assumes local dominance only on poor soils in the northeastern United States. Contemporary management goals in the Northeast for areas dominated by pitch pine are focused on noncommercial benefits of forests, such as carbon density, reduced wildfire risk, habitat for rare species, and water provisioning. We present a density management diagram that empirically articulates the size-density limits of even-aged pitch pine stands. Included in the diagram are wildfire risk and carbon density, which...

Across much of the eastern United States, oak forests are undergoing mesophication as shade-tolerant competitors become more abundant and suppress oak regeneration. Given the historical role of anthropogenic surface fires in promoting oak dominance, prescribed fire has become important in efforts to reverse mesophication and sustain oaks. In 2000 we established the Ohio Hills Fire and Fire Surrogate (FFS) study to examine whether repeated prescribed fire (Fire), mechanical partial harvest (Mech), and their combined application (Mech + Fire) reduced the dominance of subcanopy mesophytic...

Peatlands are sources of bioaccumulating neurotoxin methylmercury (MeHg) that is linked to adverse health outcomes. Yet, the compounding impacts of climate change and reductions in atmospheric pollutants on mercury (Hg) export from peatlands are highly uncertain. We investigated the response in annual flow-weighted concentrations (FWC) and yields of total-Hg (THg) and MeHg to cleaner air and climate change using an unprecedented hydroclimatic (55-year; streamflow, air temperature, precipitation, and peatland water tables), depositional chemistry (21-year; Hg and major ions), and streamwater...

Organic peat soils occupy relatively little of the global land surface area but store vast amounts of soil carbon in northern latitudes where climate is warming at a rapid pace. Warming may result in strong positive feedbacks of carbon loss and global climate change driven by microbial processes if warming alters the balance between primary productivity and decomposition. To elucidate effects of warming on the microbial communities mediating peat carbon dynamics, we explored the abundance of broad microbial groups and their source of carbon (i.e. old carbon versus more recently fixed...

Climate change is reducing the amount, duration, and extent of snow across high‐latitude ecosystems. But, in landscapes where persistent winter snow cover develops, experimental platforms to specifically investigate interactions between warming and changes in snowpack, and impacts on ecosystem processes, have been lacking. We leveraged a whole‐ecosystem warming experiment in a boreal peatland forest to quantify how snow duration, depth, and fractional cover vary with warming of up to +9°C. We found that every snow‐related quantity we examined declined precipitously as the amount of warming...

Wildland fire–atmosphere interaction generates complex turbulence patterns, organized across multiple scales, which inform fire-spread behaviour, firebrand transport, and smoke dispersion. Here, we utilize wavelet-based techniques to explore the characteristic temporal scales associated with coherent patterns in the measured temperature and the turbulent fluxes during a prescribed wind-driven (heading) surface fire beneath a forest canopy.We use temperature and velocity measurements from tower-mounted sonic anemometers at multiple heights. Patterns in the wavelet-based energy density of...

Mercury (Hg) is a pollutant that bioaccumulates in the food web, leading to health issues in humans and other fauna. Although anthropogenic Hg deposition has decreased over the past 20 years, our watersheds continue to be sources of Hg to downstream communities. Wetlands, especially peatlands in the Boreal Region of the globe, play a vital role in the formation of bioaccumulative methylmercury (MeHg). Few studies have assessed how increases in temperatures such as those that have already occurred and those predicted will influence the hydrologic transport of Hg to downstream communities or...

The use of prescribed fire to reduce the risk of wildfires and maintain or enhance desired ecological conditions is increasing in forests of the Mid-Atlantic region. Accurate estimates of forest carbon (C) dynamics associated with prescribed burning, including net ecosystem productivity (NEP) and time to accumulate the C lost during burns, termed neutral net ecosystem C balance (NECB), as a function of fire intensity and burn intervals would assist fire managers optimize treatment timing while balancing other ecosystem services provided by forests. We quantified forest C dynamics and...

Although northern white-cedar (Thuja occidentalis; henceforth cedar) is thought to have few insect pests, arborvitae leafminers (primarily Argyresthia thuiella) have been known to cause leaf necrosis. Yet, historical evidence for leafminer outbreaks is limited. We combined leafminer larval surveys conducted between 1950 and 1992 with tree-ring analyses from eight cedar stands to reconstruct a history of leafminer outbreaks in Maine, USA. Our tree-ring data show distinctive 2- to 3-year growth reductions that we attribute to leafminers. Several such growth reductions correspond to peak...