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113 results for “Coweeta Hydrologic Laboratory”
Habitat suitability and the distribution of species: Polygonatum biflorum demography data from the Coweeta Hydrologic Laboratory from 1998 to 2006
Metapopulation theory posits that suitable habitat may frequently be unoccupied because it is isolated and has never been colonized or has been colonized followed by local extinction and has not yet been recolonized. This research addresses the question of how to identify suitable, unoccupied habitat and distinguish it from unsuitable habitat. We are studying a group of six species of forest understory herbs chosen to represent a broad range of habitat distribution and dispersal characteristics. Our aim is to quantify the fundamental niche of these species (sensu Hutchinson 1957), in terms of variables such as soil moisture and temperature, by developing a set of habitat specific demographic stage transition models (i.e. conditional on such environmental variables) for these species. These models, in combination with data from field surveys of the local distribution of the species, will be used to develop testable predictive maps of the distribution of suitable habitat which can be compared to the observed distribution of the plants. We hypothesize that both dispersal ability and the distribution of suitable habitat are important determinants of the actual distribution of species. The goal of this research is both to further our conceptual understanding of the relationships between habitat requirements and species distributions, and to provide a practical approach to operationalizing the concept of "suitable habitat."
Growth-mortality relationships for southern Appalachian trees from the Coweeta Hydrologic Laboratory in 1995
Ecologists and foresters have long noted a link between tree growth rate and mortality, and recent work suggests that interspecific differences in low growth tolerance is a key force shaping forest structure. Little information is available, however, on the growth-mortality relationship for most species. We present three methods for estimating growth-mortality functions from readily obtainable field data. All use annual mortality rates and the recent growth rates of living and dead individuals. Annual mortality rates are estimated using both survival analysis and a Bayesian approach. Growth rates are obtained from increment cores. Growth-mortality functions are fitted using two parametric approaches and a non-parametric approach. The three methods are compared using bootstrapped confidence intervals and likelihood ratio tests. For two example species, Acer rubrum and Cornus florida, growth-mortality functions indicate a substantial difference in the two species abilities to withstand slow growth. Both survival analysis and Bayesian estimates of mortality rates lead to similar growth-mortality functions, with the Bayesian approach providing a means to overcome the absence of long-term census data. In fitting growth-mortality functions, the non-parametric approach reveals that inflexibility in parametric methods can lead to errors in estimating mortality risk at low growth. We thus suggest that non-parametric fits be used as a tool for assessing parametric models.
Tree seedling densities across an elevation and moisture gradient from the Coweeta Hydrologic Laboratory from 1996 to 1999
First year seedling densities of all woody perennials (trees, vines, shrubs) were censused across five permanent vegetation plots to compare spatial distributions with adult trees, seed densities and seed bank densities.
Rhododendron maximum cover across an elevation gradient from the Coweeta Hydrologic Laboratory from 1997 to 1999
Rhododendron maximum leaf area was measured at 167 locations to determine the spatial extent of this understory shrub, and compare Rhododendron maximum cover with seedling germination rates and seedling diversity (measured in another study). Rhododendron maximum leaf area index was determined at 167 points within each permanent vegetation plot. The initial 86 points were sampled in 1997, and the remainder sampled in the summer of 1999.
Gradient throughfall (thrufall) collection at the Coweeta Hydrologic Laboratory from 1992 to 1997
To investigate long term forest ecosystem responses to disturbance and stress along an elevational gradient, five plots were established as follows: xeric oak-pine (782 m), cove hardwood (795 m), low elevation mixed oak (865 m), high elevation mixed oak (1001 m), and northern hardwoods (1347 m). Phenomena being studied in these plots include: climatology, nutrient dynamics, decomposition, vegetation productivity and population dynamics, and below-ground processes. As part of study on nutrient dynamics, throughfall was sampled weekly and concentrations and fluxes were examined from each of the five gradient plots.
Microclimate Measurements from the Terrestrial Gradient Plots, Coweeta Hydrologic Laboratory, North Carolina
The terrestrial gradient study at Coweeta compares vegetation, soils, and understory microclimate of five sites: 118 low elevation (782 m) pine-oak, 218 low elevation (795 m) cove hardwood, 318 low elevation (865 m) mixed oak, 427 high elevation (1001 m) mixed oak, 527 high elevation (1347 m) northern hardwood. Understory microclimate stations were installed in representative locations at the downslope margin of each 20 x 40 m gradient plot (within the 80 x 80 m plot).
Nitrogen transformation along an elevational and vegetative gradient from the Coweeta Hydrologic Laboratory from 1991 to 1995
Examination of N-transformation along elevation and vegetation gradient. These measurements are analysis of plant nitrogen availability and overall site productivity.
Nitrogen transformation along an elevational and vegetative gradient from the Coweeta Hydrologic Laboratory from 1991 to 1995
Examination of N-transformation along elevation and vegetation gradient. These measurements are analysis of plant nitrogen availability and overall site productivity.
Gap soil moisture at the Coweeta Hydrologic Laboratory from 1993 to 1996
Small canopy openings often alter understory microclimate, leading to changes in forest structure and composition. It is generally accepted that physical changes in the understory (i.e., microclimatic) due to canopy removal drive changes in basic forest processes, particularly seedling recruitment which is intrinsically linked to soil moisture availability, light and, to a lesser extent, temperature. We examined the impact of small canopy gaps of the type (snags) and size (~300 m2) most frequently observed in the southern Appalachians on the understory microclimate. We created artificial canopy gaps at two elevations (a.m.s.l.) by girdling trees in areas with and without a Rhododendron maximum L. (rosebay rhododendron) understory. Soil and air temperature (degrees C), photosynthetically active radiation (PAR; mmol m-2s-1), and volumetric soil water content (WC%) in the upper 15 cm of soil were measured along transects generally running north to south through each gap. Overall, PAR was substantially less in rhododendron gaps than in non-rhododendron gaps.
Gap PAR (Photosynthetic Active Radiation) at the Coweeta Hydrologic Laboratory from 1993 to 1997
Small canopy openings often alter understory microclimate, leading to changes in forest structure and composition. It is generally accepted that physical changes in the understory (i.e., microclimatic) due to canopy removal drive changes in basic forest processes, particularly seedling recruitment which is intrinsically linked to soil moisture availability, light and, to a lesser extent, temperature. We examined the impact of small canopy gaps of the type (snags) and size (~300 m2) most frequently observed in the southern Appalachians on the understory microclimate. We created artificial canopy gaps at two elevations (a.m.s.l.) by girdling trees in areas with and without a Rhododendron maximum L. (rosebay rhododendron) understory. Soil and air temperature (degrees C), photosynthetically active radiation (PAR; mmol m-2s-1), and volumetric soil water content (WC%) in the upper 15 cm of soil were measured along transects generally running north to south through each gap.
Tree census, demography, and exposed canopy area data at the Coweeta LTER Terrestrial Gradient Sites, Coweeta Hydrological Laboratory, Otto, NC from 1993 to 2016
The five Terrestrial Gradient sites were established in the early 1990s as part of the 1990 Coweeta LTER Renewal. The original terrestrial gradient sites were 20 x 40-m. In the late 1990s the plots were expanded to 80 x 80-m and later (around 1998) they were slope-corrected by Clark's lab using survey equipment. Much of the Coweeta LTER “core” datasets have been collected from the gradient plots. This study is one of the long-term studies that are ongoing with defined sampling intervals. The tree demography and census study consists of trees census every two years and seeds collected ~5 x each year.
Examining the potential effects of phytophagous insect frass on forest nitrogen cycling at the Coweeta Hydrologic Laboratory from 1999 to 2001
Human alteration of the global nitrogen cycle has increased the importance of understanding the major sources, sinks, and fluxes of the cycle within natural ecosystems. One poorly understood component of the nitrogen cycle in forest ecosystems is the contribution of phytophagous insect frass on soil N-cycling dynamics. This study proposes to investigate the influence of frass on (1) the dynamics of soil N-cycling; (2) the loss of N from the ecosystem via leaching; (3) the slow cycle decomposition of post-herbivore leaf litter; and (4) the overall potential of soil near the Coweeta Hydrologic Laboratory to retain nitrogen. Red Oak (Quercus rubra [Fagaceae]) saplings will be subjected to defoliation by the seasonal phytophagous insect larvae of the White-Marked Tussock Moth (Orgyia leucostigma [Lepidoptera: Lymantriidae]) and the frass added to the soil in a factorial, controlled experimental design. Soil nutrient concentrations, leachate nutrient concentrations, "soil" respiration, and leaf quality will be measured. The project is expected to increase our understanding of the complex relationship between above-ground and below-ground nitrogen cycling dynamics as well as inform the current debate concerning the relative impacts and importance of human versus natural alterations to the nitrogen cycle.
Summary of lysimeter ion concentrations at Coweeta Watershed One at the Coweeta Hydrologic Laboratory from 1985 to 1988
None provided by researcher.
Bulk throughfall at Coweeta White Pine, Watershed One at the Coweeta Hydrologic Laboratory from 1985 to 1988
None provided by researcher.
Bulk stemflow at Coweeta Hardwoods, Watershed Two from 1985 to 1988 (Coweeta Hydrologic Laboratory)
Data was collected from six collectors. Statistical means were volume weighted.
Bulk throughfall at Coweeta Hardwoods, Watershed Two (Coweeta Hydrologic Laboratory) from 1985 to 1988
Data was collected from six collectors. Statistical means were volume weighted.
Bulk stemflow at Coweeta White Pines, Watershed One (Coweeta Hydrologic Laboratory) from 1985 to 1988
Data was collected from six collectors. Statistical means were volume weighted.
Elevational gradient in ant diversity in the Coweeta Hydrologic Laboratory in 2005
This study will examine spatial patterns of ant diversity, body size, and community composition along the elevational gradient at Coweeta. The data will be part of a larger study that will examine several gradients in the US and abroad to assess whether there are general mechanisms that shape these diversity gradients. Patterns of ant species diversity are well documented and yet the mechanisms promoting species coexistence among communities are often elusive. Two emerging hypotheses that account for coexistence in ant communities are the discovery-dominance tradeoff and the dominance-thermal tolerance tradeoff. Here we used behavioural assays and community-level sampling from ant assemblages in the southern Appalachians, USA to test for the discovery-dominance and dominance-thermal tolerance tradeoffs. The investigators involved were Nathan Sanders, Robert Dunn, JP Lessard, and Melissa Geraghty.
Seasonal leaf litter mass (2000 - 2010) for the Functional Diversity project, Coweeta Hydrologic Laboratory, Otto, North Carolina
The importance of the herbaceous layer in regulating ecosystem processes in deciduous forests is generally unknown. We use a manipulative study in a rich, mesophytic cove forest in the southern Appalachians to test the following hypotheses: (i) the herbaceous functional group (HFG) in mesophytic coves accelerates carbon and nutrient cycling, (ii) high litter quality input and rapid nutrient turnover associated with HFG will have a positive effect on overstory tree growth, and (iii) the HFG regulates tree regeneration with negative effects on seedling establishment due to competition for resources. We established treatment plots in a mesic, cove-hardwoods forest and removed the herbaceous flora (HR, removed twice per year) or added herbaceous organic material (OMA, once per year) for comparison to a no removal (NR) reference for a total of 14 years. The OMA treatment stimulated soil N-mineralization and increased litterfall mass and N content. OMA N-mineralization rates were more than two times greater than both the NR and HR treatments; however, we did not detect significant differences in soil CO2 efflux among treatments. Higher overstory litterfall mass and N in the OMA treatment plots indicated that overstory trees were benefiting from the enhanced soil N-mineralization. Higher overstory leaf mass and N suggests an important linkage between HR and aboveground net primary production even though this did not translate into greater tree basal area increment. We found an increase in regeneration of all tree species with HFG removal, and the response was particularly evident for Acer rubrum seedlings.
Forest floor Carbon & Nitrogen pools at the Coweeta LTER Terrestrial Gradient Sites, Coweeta Hydrological Laboratory, Otto, NC.
This project is part of a larger examination of site productivity along an elevational gradient. Forest floor weights, %C, and %N were measured at each of the five terrestrial gradient plots located along an elevational gradient at Coweeta Hydrologic Lab, Otto, NC.
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