A5026447497- Climate change and permafrost
- Geology and Paleoclimatology Research
- Ecology and Vegetation Dynamics Studies
- Plant Water Relations and Carbon Dynamics
- Cryospheric studies and observations
- Plant and animal studies
- Rangeland and Wildlife Management
- Peatlands and Wetlands Ecology
- Plant responses to elevated CO2
- Fire effects on ecosystems
- Forest ecology and management
- Remote Sensing in Agriculture
- Leaf Properties and Growth Measurement
- Tree-ring climate responses
- Tree Root and Stability Studies
- Botany and Plant Ecology Studies
- Polar Research and Ecology
- Smart Materials for Construction
- Botany, Ecology, and Taxonomy Studies
- Lichen and fungal ecology
- Seedling growth and survival studies
- Ecology and Conservation Studies
- Species Distribution and Climate Change
- Plant Pathogens and Fungal Diseases
- Fern and Epiphyte Biology
Wilkes University
2015-2024
Florida International University
2021
The University of Texas at El Paso
2021
Marine Biological Laboratory
2021
University of Stirling
2021
Finnish Museum of Natural History
2020
University of Helsinki
2020
Swedish University of Agricultural Sciences
2020
University of Scranton
1999-2008
Universidad Santa Paula
2007
SUMMARY (1) Measurements of photosynthetic photon flux density (PPFD) in four sites within a lowland tropical rain forest were compared. The habitats investigated 0.5 ha clearing, 400 m2 gap, 200 and heavily shaded understorey. (2) made during both wet dry seasons under variety weather conditions. Quantum sensors used to monitor continuously 10-min average PPFD over 3-10 day period at each location. Daily PPFD, total daily frequency distributions analysed for two adjacent per site on...
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...
Abstract Arctic and alpine tundra ecosystems are large reservoirs of organic carbon 1,2 . Climate warming may stimulate ecosystem respiration release into the atmosphere 3,4 The magnitude persistency this stimulation environmental mechanisms that drive its variation remain uncertain 5–7 This hampers accuracy global land carbon–climate feedback projections 7,8 Here we synthesize 136 datasets from 56 open-top chamber in situ experiments located at 28 arctic sites which have been running for...
Patterns of biomass, productivity, and nutrient cycling were compared between water—track nontrack areas in Alaskan tussock tundra. Water tracks (channels subsurface water drainage) sampled tundra 2.4—fold more productive than adjacent due almost entirely to the 10—fold greater aboveground production sedge Eriophorum vaginatum L. track. Nitrogen phosphorus cycled rapidly slightly warmer soil temperature, deeper thaw, higher phosphatase protease activities, rapid nitrogen mineralization. The...
Landslides are common in mountainous regions of the Caribbean and triggered by heavy rains earthquakes, often occur association with human disturbances (e.g., roads). Spatially heterogeneous removal both substrate vegetation is responsible for a variety patterns ecosystem development plant successional trajectories within landslides. Soil nutrient pools exposed mineral soils reach levels comparable to mature forest 55 yr but soil organic matter recovers more slowly. Plant colonization...
Forests are often subject to multiple, compounded disturbances, representing both natural and human‐induced processes. Predicting forest dynamics requires that we consider how these disturbances interact affect species demography. Here present results of an individual‐based, spatially explicit simulator developed analyze the effects hurricane disturbance land use legacies on a subtropical forest. We used data from 16‐ha Luquillo Forest Dynamics Plot in Puerto Rico, together with...
Following damage caused by Hurricane Hugo (September 1989) we monitored inorganic nitrogen availability in soil twice 1990, leaf area index 1991 and 1993, litter production from 1990 through 1992 subtropical wet forest of eastem Puerto Rico. Experimental removal woody debris generated the hurricane (plus any standing stocks present before hurricane) increased above-ground productivity as much 40% compared to unmanipulated contro! plots. These increases were similar those created quarterly...
The changes in light availability the understory of a subtropical wet forest (Luquillo Experimental Forest, Puerto Rico) were monitored after passage Hurricane Hugo on 18 September 1989. Gallium arsenide phosphide sensors placed 1 m apart along 32 transect. Data collected for periods 7-10 d October and December 1989, March, July, November 1990. Daily histograms generated observations photosynthetic photon flux density (PPFD) taken every two seconds. Mean total daily PPFD was calculated each...
Seedlings of two tree species from the Atlantic lowlands Costa Rica, Ochroma la‐gopus Swartz, a fast‐growing pioneer species, and Pentaclethra macroloba (Willd.) Kuntze, slower‐growing climax were grown under enriched atmospheric CO 2 in controlled environment chambers. Carbon dioxide concentrations maintained at 350 675 μl 1 −1 photosynthetic photon flux densities 500 μol m −2 s temperatures 26°C day 20°C night. Total biomass both increased significantly elevated treatment; increase was...
SUMMARY (1) Life-tables were constructed for vegetative tillers of Eriophorum vaginatum from undisturbed and disturbed tussock tundra in Alaska. also that had been fertilized with N, P K. The life-tables used to estimate population parameters construct constant coefficient matrix models tiller demography. (2) Tiller survival was lower than it tundra, daughter produced sooner. Addition nutrients (as fertilizer) no change the age distribution production first year following fertilization....
Summary 1. Reciprocal transplant experiments designed to quantify genetic and environmental effects on phenotype are powerful tools for the study of local adaptation. For long‐lived species, especially those in habitats with short growing seasons, however, cumulative many years novel environments may be required fitness differences phenotypic changes accrue. 2. We returned two separate reciprocal thirty after their initial establishment interior Alaska ask whether patterns differentiation...
NED FETCHER, BRUCE L. HAINES,t ROBERTO A. CORDERO, D. JEAN LODGE,*? LAWRENCE R. WALKER,: DENNY S. FERNANDEZ and WILLIAM T. LAWRENCE*? Department of Biology, Box 23360, * Terrestrial Ecology Division, Center for Energy Environment Research, University Puerto Rico, GPO 363682, San Juan, tBotany Institute Ecology, Georgia, Athens, GA 30602-7271 tDepartment Biological Sciences, Nevada, Las Vegas, NV 89154-4004, USA
Summary Abiotic variables are critical drivers of succession in most primary seres, but how their influence on biota changes over time is rarely examined. Landslides provide good model systems for examining abiotic influences because they spatially and temporally heterogeneous habitats with distinct biotic gradients post‐landslide erosion. In an 18‐year study 6 P uerto R ican landslides, we used structural equation models to interpret the changing effects (landslide dimensions, slope,...
Abstract While the direct effects of white-tailed deer ( Odocoileus virginianus ) on vegetation have been intensively studied, less is known about indirect and interactive herbivory lower trophic levels, such as soil microbes their processing carbon pools. We explored how dynamics shift with release from over-browsing by in two mature stands oak hemlock trees. measured pools (for example, organic matter, stocks, litter biomass, stabilization) fluxes respiration, methane uptake, microbial...
Growth, flowering, and nutrient content of Eriophorum vaginatum were observed annually over 4 yr at 34 sites spanning 5.5° latitude 1050 m elevation in northern central Alaska. We found a strong correlation between the average number thawing degree—days during growing season peak—season leaf mass per tiller. However, results from reciprocal transplant gardens established five suggested was due more to genetic differences among populations than direct climatic effects. Other variables showed...
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Plants are often genetically specialized as ecotypes attuned to local environmental conditions. When conditions change, the optimal environment may be physically displaced from population, unless dispersal or in situ evolution keep pace, resulting a phenomenon called adaptational lag. Using 30-year-old reciprocal transplant study across 475 km latitudinal gradient, we tested lag hypothesis by measuring both short-term (tiller population growth rates) and long-term (17-year survival) fitness...
ABSTRACT Seedling dynamics were followed in a Puerto Rican forest for 20 months following severe hurricane to study the interactive effects of debris, nutrients, and light on seedling diversity, density, growth, mortality. Three treatments (debris removal, an unaltered control with chemical fertilization added debris) altered levels debris soil nutrients. Canopy openness was measured twice using hemispherical photographs canopy. We examined demographic responses six common species over time....