A5024572966- Soil Carbon and Nitrogen Dynamics
- Soil and Water Nutrient Dynamics
- Peatlands and Wetlands Ecology
- Fire effects on ecosystems
- Ecology and Vegetation Dynamics Studies
- Forest ecology and management
- Isotope Analysis in Ecology
- Plant Water Relations and Carbon Dynamics
- Seedling growth and survival studies
- Lichen and fungal ecology
- Geology and Paleoclimatology Research
- Rangeland and Wildlife Management
- Soil erosion and sediment transport
- Legume Nitrogen Fixing Symbiosis
- Atmospheric and Environmental Gas Dynamics
- Hydrology and Watershed Management Studies
- Forest Management and Policy
- Plant responses to elevated CO2
- Groundwater and Isotope Geochemistry
- Forest Ecology and Biodiversity Studies
- Marine and coastal ecosystems
- Agronomic Practices and Intercropping Systems
- Tree-ring climate responses
- Geochemistry and Elemental Analysis
- Heavy metals in environment
United States Geological Survey
2015-2024
Forest and Rangeland Ecosystem Science Center
2012-2024
Oregon State University
2006-2021
Pacific Island Ecosystems Research Center
2014
Michigan State University
2008
Cornell University
1999-2002
Seattle University
1996
University of Washington
1996
Human activities have clearly caused dramatic alterations of the terrestrial nitrogen cycle, and analyses extent effects such changes are now common in scientific literature. However, any attempt to evaluate N cycling processes within ecosystems, as well anthropogenic influences on requires an understanding magnitude inputs via biological fixation (BNF). Although there been many studies addressing microbiology, physiology, at local scales, very few estimates BNF over large scales. We...
Human activity in the last century has led to a significant increase nitrogen (N) emissions and atmospheric deposition. This N deposition reached level that caused or is likely cause alterations structure function of many ecosystems across United States. One approach for quantifying pollution would be harmful determination critical loads. A load defined as input pollutant below which no detrimental ecological effects occur over long-term according present knowledge. The objectives this...
Nitrogen retention and recycling are topics of enduring interest in ecosystem ecology, yet we lack a mechanistic field-tested model how these processes work unpolluted, old-growth temperate forests. Forests the Cordillera Piuchué Ecosystem Study (CPES) southern Chile provide an opportunity to examine nitrogen cycling forest that is virtually free human disturbance. We applied 15N pool dilution pulse-chase tracer techniques as complementary approaches within small plots understand flows...
Quantifying global patterns of terrestrial nitrogen (N) cycling is central to predicting future primary productivity, carbon sequestration, nutrient fluxes aquatic systems, and climate forcing. With limited direct measures soil N at the scale, syntheses (15)N:(14)N ratio organic matter across gradients provide key insights into understanding cycling. In synthesizing data from over 6000 samples, we show strong relationships among isotopes, mean annual temperature (MAT), precipitation (MAP),...
Wide natural gradients of soil nitrogen (N) can be used to examine fundamental relationships between plant–soil–microbial N cycling and hydrologic loss, test N-saturation theory as a general framework for understanding ecosystem dynamics. We characterized plant production, uptake return in litterfall, gross net mineralization rates, losses nine Douglas-fir (Pseudotsuga menziesii) forests across wide gradient the Oregon Coast Range (USA). Surface mineral (0–10 cm) ranged nearly three-fold...
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...
Forests cover 30% of the terrestrial Earth surface and are a major component global carbon (C) cycle. Humans have doubled amount reactive nitrogen (N), increasing deposition N onto forests worldwide. However, other changes-especially climate change elevated atmospheric dioxide concentrations-are demand for N, element limiting primary productivity in temperate forests, which could be reducing availability. To determine long-term, integrated effects changes on forest cycling, we measured...
Abstract We review the mechanisms of deleterious nitrogen (N) deposition impacts on temperate forests, with a particular focus trees and lichens. Elevated anthropogenic N to forests has varied effects individual organisms depending characteristics both inputs (form, timing, amount) (ecology, physiology) involved. Improved mechanistic knowledge these can aid in developing robust predictions how respond either increases or decreases deposition. Rising levels affect micro‐ macroscopic ways from...
Atmospheric deposition of nitrogen (N) influences forest demographics and carbon (C) uptake through multiple mechanisms that vary among tree species. Prior studies have estimated the effects atmospheric N on temperate forests by leveraging inventory measurements across regional gradients in deposition. However, United States (U.S.), these previous were limited number species spatial scale analysis, did not include sulfur (S) as a potential covariate. Here, we present comprehensive analysis...
Significance Tree species that form symbioses with nitrogen-fixing bacteria can naturally fertilize forests by converting atmospheric nitrogen gas into plant-available forms. However, other mineral nutrients plants require for growth are largely locked in bedrock, and released only slowly soil. We used strontium isotopes to trace nutrient sources six common tree a temperate rainforest, including one from globally widespread genus known high rates of biological fixation. found trees capable...
Abstract Accurately quantifying rates and patterns of biological nitrogen fixation (BNF) in terrestrial ecosystems is essential to characterize ecological biogeochemical interactions, identify mechanistic controls, improve BNF representation conceptual numerical modelling, forecast limitation constraints on future carbon (C) cycling. While many resources address the technical advantages limitations different methods for measuring BNF, less systematic consideration has been given broader...
Abstract Human activities are rapidly increasing the global supply of reactive N and substantially altering structure hydrologic connectivity managed ecosystems. There is long‐standing recognition that must be removed along flow paths from uplands to streams, yet it has proven difficult assess generality this removal across ecosystem types whether these patterns influenced by land use change. To how well upland nitrate (NO 3 − ) loss reflected in stream export, we gathered information >50...
High nitrogen (N) accumulation in terrestrial ecosystems can shift patterns of nutrient limitation and deficiency beyond N toward other nutrients, most notably phosphorus (P) base cations (calcium [Ca], magnesium [Mg], potassium [K]). We examined how naturally high from a legacy symbiotic fixation shaped P cation cycling across gradient nine temperate conifer forests the Oregon Coast Range. were particularly interested whether long-term legacies promoted coupled organic soils, biotic demands...
Abstract Few high‐elevation tropical catchments worldwide are gauged, and even fewer studied using combined hydrometric isotopic data. Consequently, we lack information needed to understand processes governing rainfall–runoff dynamics predict their influence on downstream ecosystem functioning. To address this need, present a combination of water stable observations in the wet Andean páramo Zhurucay Ecohydrological Observatory (7.53 km 2 ). The catchment is located Andes south Ecuador...
Summary Trait‐based models of ecological communities typically assume intraspecific variation in functional traits is not important, although such can change species trait rankings along gradients resources and environmental conditions, thus influence community structure function. We examined the degree relative to interspecific variation, reaction norms 11 for 57 forest understorey plant species, including: intrinsic water‐use efficiency ( iWUE ), Δ 15 N, five leaf traits, two stem root...
ABSTRACT Coastal margins are important areas of materials flux that link terrestrial and marine ecosystems. Consequently, climate-mediated changes to coastal ecosystems hydrologic regimes have high potential influence nearshore ocean chemistry food web dynamics. Research from tightly coupled, high-flux can advance understanding terrestrial–marine links climate sensitivities more generally. In the present article, we use northeast Pacific temperate rainforest as a model system evaluate such...
Accelerated nitrogen (N) inputs can drive nonlinear changes in N cycling, retention, and loss forest ecosystems. Nitrogen processing soils is critical to understanding these changes, since typically are the largest sink forests. To elucidate soil mechanisms that underlie shifts cycling across a wide gradient of supply, we added 15NH415NO3 at nine treatment levels ranging geometric sequence from 0.2 kg 640 N·ha−1·yr−1 an unpolluted old-growth temperate southern Chile. We recovered roughly...