Treesearch

Eddy covariance nighttime fluxes are uncertain due to potential measurement biases. Many studies report eddy covariance nighttime flux lower than flux from extrapolated chamber measurements, despite corrections for low turbulence. We compared eddy covariance and chamber estimates of ecosystem respiration at the GLEES Ameriflux site over seven growing seasons under high turbulence [summer night mean friction velocity (u*) = 0.7 m s−1], during which bark beetles killed or infested 85% of the aboveground respiring biomass. Chamber-based estimates of ecosystem respiration during the growth...

Current scientific conversation and practice often emphasizes the importance of interdisciplinary research in tackling complex, contemporary issues. Direct observation is one of the most abiding, and sometimes overlooked, scientific methods that is common across most disciplines. On a summer afternoon in 2012, our USDA Forest Service research team went for a hike along a long stretch of the Rockaways—a peninsula abutting Jamaica Bay. Our goal was to explore this urban gradient—its shifts in land use and vegetative cover—and to better understand the methods each one of us...

The timing of births in ungulates has significant implications for juvenile survival and population growth. For North American elk (Cervus elaphus), typical parturition season ranges from late May to early Jun., and juveniles born outside of this peak characteristically exhibit lowered survival. We observed abnormally long parturition seasons in free-ranging elk populations in Missouri and South Dakota during 2012. Both populations exhibited late births; the last known births occurred on 26 Sep. in Missouri and 4 Sep. in South Dakota. Duration of parturition season was 112 and 119 d in...

Landscape fire succession models (LFSMs) predict spatially-explicit interactions between vegetation succession and disturbance, but these models have yet to fully integrate ungulate herbivory as a driver of their processes. We modified a complex LFSM, FireBGCv2, to include a multi-species herbivory module, GrazeBGC. The system is novel in that it explicitly accommodates multiple herbivore populations, inter- and intra-specific spatial forcing of their forage demands, and site-specific dietary selectivity to interactively modify biomass, fuels and fire behavior across a landscape and over...

A hydropedologic approach can be used to describe soil units affected by distinct hydrologic regimes. We used field observations of soil morphology and geospatial information technology to map the distribution of five hydropedologic soil units across a 42-ha forested headwater catchment. Soils were described and characterized at 172 locations within Watershed 3, the hydrologic reference catchment for the Hubbard Brook Experimental Forest, New Hampshire. Soil profiles were grouped by presence and thickness of genetic horizons. Topographic and bedrock metrics were used in a logistic regressio...

Classical podzolization studies assumed vertical percolation and pedon-scale horizon development. However, hillslope-scale lateral podzolization also occurs where lateral subsurface water flux predominates. In this hydropedologic study, 99 podzols were observed in Watershed 3, Hubbard Brook Experimental Forest, New Hampshire. Soil horizon samples were extracted with citrate-dithionite (d) and acid ammonium oxalate (o) to quantify Fed, Mnd, Alo, and Feo. Optical density of oxalate extract (ODOE) was measured to assess spodic C. Amorphous organometallic complexes (AOC) were observed in thin...

Droughts can influence forest composition directly by limiting water or indirectly by intensifying other stressors that affect establishment, growth, and mortality. Using community assemblages of eastern US tree species and drought tolerance characteristics assessed from literature, we examine recent drought conditions in relation to the spatial distribution of species and their tolerance to drought. First we calculate and compare a cumulative drought severity index (CDSI) for the conterminous US for the periods 1960-1986 and 1987-2013 using climate division Palmer Drought Severity Index...

The genus Liancalus Loew is revised for the Nearctic Region. Seven species are documented from this region including two new species: Liancalus genualis Loew, L. hydrophilus Aldrich, L. limbatus Van Duzee, L. pterodactyl sp. n., L. querulus Osten Sacken, L. similis Aldrich, and L. sonorus sp. n. Lectotypes are designated for the following species: L. genualis, L. hydrophilus, L. querulus, and L. similis. The species are illustrated, a key to males and females is provided, and their distributions mapped. Adults of Liancalus are some of the largest species of Dolichopodidae and commonly...

Open space lands are provided by a variety of entities from private individuals to the federal government and these entities make management decisions based on a very broad range of priorities. The net benefits of additional open space depend on the number, quality, and composition of existing open space in the vicinity. In areas where open space is abundant and there is a significant proportion that is federally owned, the net benefits are not well understood. In this study, the marginal willingness to pay for proximity to public open space is estimated using the hedonic property method...

The replacement of native C4-dominated grassland by C3-dominated shrubland is considered an ecological state transition where different ecological communities can exist under similar environmental conditions. These state transitions are occurring globally, and may be exacerbated by climate change. One consequence of the global increase in woody vegetation may be enhanced ecosystem carbon sequestration, although the responses of arid and semiarid ecosystems may be highly variable. During a drier than average period from 2007 to 2011 in the northern Chihuahuan Desert, we found established...