The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
Dale W. Johnson - One of the best experts on this subject based on the ideXlab platform.
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Tamm Review: Nutrient Cycling in forests: A historical look and newer developments
Forest Ecology and Management, 2019Co-Authors: Dale W. Johnson, John TurnerAbstract:Abstract In this review, we consider a traditional conceptual model of Nutrient Cycling in forests and evaluate (1) assumptions and issues with existing methods for measuring and calculating Nutrient pools and fluxes, including the estimation of errors; (2) how various elements of the conceptual model vary with geographic and climatic region, and gaps in knowledge about certain regions; (3) predictions from Nutrient Cycling data for the effects of harvesting, burning, fertilization, and elevated CO2, including the effects of Nutrient Cycling on productivity and the effects of productivity on Nutrient Cycling. As is true of all models, traditional models of forest Nutrient Cycling are all incorrect in the sense that they are approximations and do not capture all features the real world. For example, none of these traditional models include the important effects of catastrophic events such as wildfire, insect attack, hurricanes, etc. Nonetheless, traditional Nutrient Cycling models have allowed us to explore the collective implications of our current understanding of Nutrient Cycling processes. While the methods apply to plantations the focus of this review has been on natural forest studies. Despite much effort, reliable estimates of some transfers such as soil weathering and nitrogen fixation remain elusive. Soluble exports on a watershed level are not reliable representatives of exports from terrestrial Nutrient cycles because correct conditions for such measurements are relatively rare and also because such estimates are subject to deep soil weathering and stream spiraling beyond the rooting zone. Soluble exports by lysimetery are subject to errors in the estimation of water flux and the delineation of the depth of rooting. The current versions of these traditional models will no doubt require modifications in the future to account for new information becomes available, for example, the delays between root uptake and the appearance of Nutrients in aboveground biomass, the importance of soil Nutrient hotpots for uptake, and the unforeseen ability of nitrogen-limited trees to extract additional nitrogen from soils when root growth in stimulated by elevated CO2.
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Development and evaluation of a Nutrient Cycling extension for the LANDIS-II landscape simulation model
Ecological Modelling, 2013Co-Authors: Sarah L. Karam, Dale W. Johnson, Peter J. Weisberg, Robert M. Scheller, Watkins W. MillerAbstract:Abstract Long-term Nutrient Cycling dynamics are the result of interactions between forest succession, disturbance, Nutrient Cycling, and other forest processes. We developed NuCycling-Succession, a simple Nutrient Cycling and succession extension for the LANDIS-II landscape model of forest dynamics, to examine the interactions between these forest processes in order to develop more realistic predictions of forest response to management practices and global change. NuCycling-Succession models carbon, nitrogen, and phosphorus Nutrient fluxes and masses associated with the living biomass, dead biomass, soil organic matter, soil mineral N and P, charcoal, and bedrock Nutrient pools. It includes direct effects of disturbance events on Nutrient Cycling as well as indirect effects mediated through changes in forest composition and structure. NuCycling-Succession represents the continuum of decomposition and associated changes in chemistry using annual cohorts of leaf and fine root litter. This formulation includes the interaction of decomposition dynamics with disturbances that affect the forest floor, such as fire. Evaluation of model results relative to field data and results reported in the literature indicate the model adequately represents Nutrient pools and fluxes. We present a case study of the effects of changing fire and biomass harvesting regimes on Nutrient Cycling in the Lake Tahoe Basin. Model results suggest that fire exclusion has resulted in substantially increased mass of Nutrient pools. The NuCycling-Succession extension provides a useful simulation framework for exploring how global change factors (climate change, altered disturbance regimes) may influence Nutrient Cycling processes and Nutrient budgets in forested ecosystems.
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a spreadsheet based biogeochemical model to simulate Nutrient Cycling processes in forest ecosystems
Ecological Modelling, 2001Co-Authors: P S J Verburg, Dale W. JohnsonAbstract:Abstract A Nutrient Cycling Spreadsheet (NuCSS) model was developed to simulate Nutrient Cycling in forest ecosystems. This model is intended to provide a tool for Nutrient management and is intermediate in complexity between simple budget calculations and complex, process-based ecosystem models. NuCSS simulates biomass production, organic matter decomposition, N mineralization, cation adsorption, weathering and leaching (hydrology not included) using empirical relationships and simple mechanistic process descriptions. The model calculates a target biomass production and associated Nutrient uptake. By reviewing soil Nutrient pools the user can assess whether available soil Nutrients can sustain the targeted biomass production. NuCSS was calibrated to a Norway spruce site in the Solling Mountains, Germany. The model performance was evaluated using long-term data on deposition, vegetation, water quality and soil Nutrient inventories. Long-term predictions were made using a ‘business as usual’ and two reduced deposition scenarios. Results from NuCSS were compared with simulations from other biogeochemical models. The element distribution over soil, forest floor and vegetation closely matched measurements both after one and 15 years. Forest floor Nutrients were underestimated but data on forest floor accumulation proved to be unreliable. NuCSS overestimated N uptake, N mineralization and leaching but not enough data on these fluxes were available to determine whether NuCSS was wrong. Simulated base cation leaching agreed well with the measurements but K leaching was overestimated most likely due to an underestimation of the selectivity coefficient for K adsorption. The reduced deposition scenarios caused N and base cation leaching to decrease with time. When N deposition was reduced by 95%, a N deficit occurred and N mineralization and deposition could not sustain the (fixed) uptake. For most simulated parameters NuCSS agreed well with more detailed, process-based, biogeochemical models. In general, NuCSS simulated a higher N leaching and N mineralization than most other models. Trends in base saturation and base cation leaching simulated by NuCSS agreed well with other models. The model proved to be helpful in addressing some of the uncertainties in Nutrient Cycling regarding vegetation uptake, weathering rates and N mineralization. Given the uncertainties in description of certain processes, a quantitative use of NuCSS may not be justified. These uncertainties also apply to more complex Nutrient Cycling models, however.
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The Nutrient Cycling model: lessons learned
Forest Ecology and Management, 2000Co-Authors: Dale W. Johnson, Trine A. Sogn, Sheila KvindeslandAbstract:Abstract The Nutrient Cycling model (NuCM) is a stand level model that depicts the Cycling of N, P, K, Ca, Mg, and S on daily, weekly or monthly time scales. NuCM has been applied to several forest ecosystems (ponderosa pine, red spruce, beech, eastern deciduous, loblolly pine, slash pine, Scots pine, and Norway spruce) to simulate the effects of changing atmospheric deposition, harvesting, species change, precipitation quantity, increased temperature, elevated CO2, and liming. In some cases (e.g., harvesting, liming), the model output has matched field data quite well; however, it cannot be known whether the model does so because it accurately portrays Nutrient Cycling processes or simply because of chance. In other cases, NuCM simulations have either failed to match field data (as in the case of the observed chromatographic response of soil solution cations to a nitrate pulse in a beech forest) or produced results that are counterintuitive but as yet untested (as in the case where increased N translocation caused increased leaching). In that the primary purpose of these simulations has been heuristic rather than predictive, the simulation outputs that are either inconsistent with field data or counter-intuitive are of greatest interest. This review of NuCM applications led to the conclusion that the model has been more successful in matching decadal-scale changes in Nutrient pools and soils and less successful in capturing intra-annual variations in soil solution chemistry. The NuCM model, like all models, can use improvements and these have been suggested; however, the model as it is has provided valuable insights into Nutrient Cycling in forest ecosystems, including the potential for short-term soil change and the great importance of Nutrient translocation in N Cycling.
Sheila Kvindesland - One of the best experts on this subject based on the ideXlab platform.
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The Nutrient Cycling model: lessons learned
Forest Ecology and Management, 2000Co-Authors: Dale W. Johnson, Trine A. Sogn, Sheila KvindeslandAbstract:Abstract The Nutrient Cycling model (NuCM) is a stand level model that depicts the Cycling of N, P, K, Ca, Mg, and S on daily, weekly or monthly time scales. NuCM has been applied to several forest ecosystems (ponderosa pine, red spruce, beech, eastern deciduous, loblolly pine, slash pine, Scots pine, and Norway spruce) to simulate the effects of changing atmospheric deposition, harvesting, species change, precipitation quantity, increased temperature, elevated CO2, and liming. In some cases (e.g., harvesting, liming), the model output has matched field data quite well; however, it cannot be known whether the model does so because it accurately portrays Nutrient Cycling processes or simply because of chance. In other cases, NuCM simulations have either failed to match field data (as in the case of the observed chromatographic response of soil solution cations to a nitrate pulse in a beech forest) or produced results that are counterintuitive but as yet untested (as in the case where increased N translocation caused increased leaching). In that the primary purpose of these simulations has been heuristic rather than predictive, the simulation outputs that are either inconsistent with field data or counter-intuitive are of greatest interest. This review of NuCM applications led to the conclusion that the model has been more successful in matching decadal-scale changes in Nutrient pools and soils and less successful in capturing intra-annual variations in soil solution chemistry. The NuCM model, like all models, can use improvements and these have been suggested; however, the model as it is has provided valuable insights into Nutrient Cycling in forest ecosystems, including the potential for short-term soil change and the great importance of Nutrient translocation in N Cycling.
Peter M. Vitousek - One of the best experts on this subject based on the ideXlab platform.
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The role of polyphenols in terrestrial ecosystem Nutrient Cycling
Trends in ecology & evolution, 2000Co-Authors: Stephan Hättenschwiler, Peter M. VitousekAbstract:Interspecific variation in polyphenol production by plants has been interpreted in terms of defense against herbivores. Several recent lines of evidence suggest that polyphenols also influence the pools and fluxes of inorganic and organic soil Nutrients. Such effects could have far-ranging consequences for Nutrient competition among and between plants and microbes, and for ecosystem Nutrient Cycling and retention. The significance of polyphenols for Nutrient Cycling and plant productivity is still uncertain, but it could provide an alternative or complementary explanation for the variability in polyphenol production by plants.
John Turner - One of the best experts on this subject based on the ideXlab platform.
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Tamm Review: Nutrient Cycling in forests: A historical look and newer developments
Forest Ecology and Management, 2019Co-Authors: Dale W. Johnson, John TurnerAbstract:Abstract In this review, we consider a traditional conceptual model of Nutrient Cycling in forests and evaluate (1) assumptions and issues with existing methods for measuring and calculating Nutrient pools and fluxes, including the estimation of errors; (2) how various elements of the conceptual model vary with geographic and climatic region, and gaps in knowledge about certain regions; (3) predictions from Nutrient Cycling data for the effects of harvesting, burning, fertilization, and elevated CO2, including the effects of Nutrient Cycling on productivity and the effects of productivity on Nutrient Cycling. As is true of all models, traditional models of forest Nutrient Cycling are all incorrect in the sense that they are approximations and do not capture all features the real world. For example, none of these traditional models include the important effects of catastrophic events such as wildfire, insect attack, hurricanes, etc. Nonetheless, traditional Nutrient Cycling models have allowed us to explore the collective implications of our current understanding of Nutrient Cycling processes. While the methods apply to plantations the focus of this review has been on natural forest studies. Despite much effort, reliable estimates of some transfers such as soil weathering and nitrogen fixation remain elusive. Soluble exports on a watershed level are not reliable representatives of exports from terrestrial Nutrient cycles because correct conditions for such measurements are relatively rare and also because such estimates are subject to deep soil weathering and stream spiraling beyond the rooting zone. Soluble exports by lysimetery are subject to errors in the estimation of water flux and the delineation of the depth of rooting. The current versions of these traditional models will no doubt require modifications in the future to account for new information becomes available, for example, the delays between root uptake and the appearance of Nutrients in aboveground biomass, the importance of soil Nutrient hotpots for uptake, and the unforeseen ability of nitrogen-limited trees to extract additional nitrogen from soils when root growth in stimulated by elevated CO2.
Dennis J. Minchella - One of the best experts on this subject based on the ideXlab platform.
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Parasites and Their Impact on Ecosystem Nutrient Cycling.
Trends in parasitology, 2018Co-Authors: J. Trevor Vannatta, Dennis J. MinchellaAbstract:Consumer species alter Nutrient Cycling through Nutrient transformation, transfer, and bioturbation. Parasites have rarely been considered in this framework despite their ability to indirectly alter the Cycling of Nutrients via their hosts. A simple mathematical framework can be used to assess the relative importance of parasite-derived Nutrients in an ecosystem.
