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  • 1
    Electronic Resource
    Electronic Resource
    Resource-based niches provide a basis for plant species diversity and dominance in arctic tundra (2002)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 415 (2002), S. 68-71 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Ecologists have long been intrigued by the ways co-occurring species divide limiting resources. Such resource partitioning, or niche differentiation, may promote species diversity by reducing competition. Although resource partitioning is an important determinant of species diversity and ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/415068a
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  • 2
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    A stable isotope simulator that can be coupled to existing mass balance models (2005)
    Details
    Publication Date: 2018-07-06
    Description: Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Applications 15 (2005): 1772–1782, doi: 10.1890/04-0643
    Description: To facilitate the simulation of isotope dynamics in ecosystems, we developed software to model changes in the isotopic signatures of the stocks of an element using the output from any parent model that specifies the stocks and flux rates of that element based on a mass balance approach. The software alleviates the need to recode the parent model to incorporate isotopes. This parent model can be a simple mass balance spreadsheet of the system. The isotopic simulations use a linear, donor-controlled approximation of the fluxes in the parent model, which are updated for each time step. These approximations are based on the output of the parent model, so no modifications to the parent model are required. However, all fluxes provided to the simulator must be gross fluxes, and the user must provide the initial isotopic signature for all stocks, the fractionation associated with each flux, and the isotopic signature of any flux originating from outside the system. We illustrate the use of the simulator with two examples. The first is based on a model of the carbon and nitrogen mass balance in an eight-species food web. We examine the consequences of using the steady-state assumption implicit in multi-source mixing models often used to map food webs based on 13C and 15N. We also use the simulator to analyze a pulse chase 15N-labeling experiment based on a spreadsheet model of the nitrogen cycle at the Harvard Forest Long Term Ecological Research site. We examine the constraints on net vs. gross N mineralization that are necessary to match the observed changes in the isotopic signatures of the forest N stocks.
    Description: The information in this document has been funded in part by the U.S. Environmental Protection Agency (QT-RT-00-001667). This work was also supported in part by grants from the National Science Foundation (DEB-0108960, OPP-9911681).
    Keywords: C-13 ; Food web model ; Harvard Forest, Massachusetts, USA ; Isotope dynamics ; Isotope simulation ; Mass balance model ; N-15 ; Nitrogen cycle ; Stable isotopes
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 3
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    Processing arctic eddy-flux data using a simple carbon-exchange model embedded in the ensemble Kalman filter (2011)
    Ecological Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Ecological Society of America, 2010. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Applications 20 (2010): 1285–1301, doi:10.1890/09-0876.1.
    Description: Continuous time-series estimates of net ecosystem carbon exchange (NEE) are routinely made using eddy covariance techniques. Identifying and compensating for errors in the NEE time series can be automated using a signal processing filter like the ensemble Kalman filter (EnKF). The EnKF compares each measurement in the time series to a model prediction and updates the NEE estimate by weighting the measurement and model prediction relative to a specified measurement error estimate and an estimate of the model-prediction error that is continuously updated based on model predictions of earlier measurements in the time series. Because of the covariance among model variables, the EnKF can also update estimates of variables for which there is no direct measurement. The resulting estimates evolve through time, enabling the EnKF to be used to estimate dynamic variables like changes in leaf phenology. The evolving estimates can also serve as a means to test the embedded model and reconcile persistent deviations between observations and model predictions. We embedded a simple arctic NEE model into the EnKF and filtered data from an eddy covariance tower located in tussock tundra on the northern foothills of the Brooks Range in northern Alaska, USA. The model predicts NEE based only on leaf area, irradiance, and temperature and has been well corroborated for all the major vegetation types in the Low Arctic using chamber-based data. This is the first application of the model to eddy covariance data. We modified the EnKF by adding an adaptive noise estimator that provides a feedback between persistent model data deviations and the noise added to the ensemble of Monte Carlo simulations in the EnKF. We also ran the EnKF with both a specified leaf-area trajectory and with the EnKF sequentially recalibrating leaf-area estimates to compensate for persistent model-data deviations. When used together, adaptive noise estimation and sequential recalibration substantially improved filter performance, but it did not improve performance when used individually. The EnKF estimates of leaf area followed the expected springtime canopy phenology. However, there were also diel fluctuations in the leaf-area estimates; these are a clear indication of a model deficiency possibly related to vapor pressure effects on canopy conductance.
    Description: This material is based upon work supported by the U.S. National Science Foundation under grants OPP-0352897, DEB-0423385, DEB-0439620, DEB-0444592, and OPP- 0632139.
    Keywords: Alaska, USA ; Data assimilation ; Ecosystem carbon balance ; Ecosystem models ; Eddy covariance ; Kalman filter ; Net ecosystem carbon exchange
    Repository Name: Woods Hole Open Access Server
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  • 4
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    Recovery from disturbance requires resynchronization of ecosystem nutrient cycles (2013)
    Ecological Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Ecological Society of America, 2013. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Applications 23 (2013): 621–642, doi:10.1890/12-0751.1.
    Description: Nitrogen (N) and phosphorus (P) are tightly cycled in most terrestrial ecosystems, with plant uptake more than 10 times higher than the rate of supply from deposition and weathering. This near-total dependence on recycled nutrients and the stoichiometric constraints on resource use by plants and microbes mean that the two cycles have to be synchronized such that the ratio of N:P in plant uptake, litterfall, and net mineralization are nearly the same. Disturbance can disrupt this synchronization if there is a disproportionate loss of one nutrient relative to the other. We model the resynchronization of N and P cycles following harvest of a northern hardwood forest. In our simulations, nutrient loss in the harvest is small relative to postharvest losses. The low N:P ratio of harvest residue results in a preferential release of P and retention of N. The P release is in excess of plant requirements and P is lost from the active ecosystem cycle through secondary mineral formation and leaching early in succession. Because external P inputs are small, the resynchronization of the N and P cycles later in succession is achieved by a commensurate loss of N. Through succession, the ecosystem undergoes alternating periods of N limitation, then P limitation, and eventually co-limitation as the two cycles resynchronize. However, our simulations indicate that the overall rate and extent of recovery is limited by P unless a mechanism exists either to prevent the P loss early in succession (e.g., P sequestration not stoichiometrically constrained by N) or to increase the P supply to the ecosystem later in succession (e.g., biologically enhanced weathering). Our model provides a heuristic perspective from which to assess the resynchronization among tightly cycled nutrients and the effect of that resynchronization on recovery of ecosystems from disturbance.
    Description: This material is based upon work supported by the National Science Foundation under Grants 0108960, 0716067, 0949420, 0949324, 0949317, and 0949854.
    Keywords: Co-limitation ; Disturbance ; Ecosystem succession ; N:P ratio ; Nutrient cycles ; Nutrient limitation ; Resource optimization ; Stoichiometric constraints ; Terrestrial ecosystem cycling
    Repository Name: Woods Hole Open Access Server
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  • 5
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    N and P constrain C in ecosystems under climate change: role of nutrient redistribution, accumulation, and stoichiometry (2022)
    Ecological Society of America
    Details
    Publication Date: 2022-10-27
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Rastetter, E., Kwiatkowski, B., Kicklighter, D., Plotkin, A., Genet, H., Nippert, J., O’Keefe, K., Perakis, S., Porder, S., Roley, S., Ruess, R., Thompson, J., Wieder, W., Wilcox, K., & Yanai, R. N and P constrain C in ecosystems under climate change: role of nutrient redistribution, accumulation, and stoichiometry. Ecological Applications, (2022): e2684, https://doi.org/10.1002/eap.2684.
    Description: We use the Multiple Element Limitation (MEL) model to examine responses of 12 ecosystems to elevated carbon dioxide (CO2), warming, and 20% decreases or increases in precipitation. Ecosystems respond synergistically to elevated CO2, warming, and decreased precipitation combined because higher water-use efficiency with elevated CO2 and higher fertility with warming compensate for responses to drought. Response to elevated CO2, warming, and increased precipitation combined is additive. We analyze changes in ecosystem carbon (C) based on four nitrogen (N) and four phosphorus (P) attribution factors: (1) changes in total ecosystem N and P, (2) changes in N and P distribution between vegetation and soil, (3) changes in vegetation C:N and C:P ratios, and (4) changes in soil C:N and C:P ratios. In the combined CO2 and climate change simulations, all ecosystems gain C. The contributions of these four attribution factors to changes in ecosystem C storage varies among ecosystems because of differences in the initial distributions of N and P between vegetation and soil and the openness of the ecosystem N and P cycles. The net transfer of N and P from soil to vegetation dominates the C response of forests. For tundra and grasslands, the C gain is also associated with increased soil C:N and C:P. In ecosystems with symbiotic N fixation, C gains resulted from N accumulation. Because of differences in N versus P cycle openness and the distribution of organic matter between vegetation and soil, changes in the N and P attribution factors do not always parallel one another. Differences among ecosystems in C-nutrient interactions and the amount of woody biomass interact to shape ecosystem C sequestration under simulated global change. We suggest that future studies quantify the openness of the N and P cycles and changes in the distribution of C, N, and P among ecosystem components, which currently limit understanding of nutrient effects on C sequestration and responses to elevated CO2 and climate change.
    Description: This material is based on work supported by the National Science Foundation under Grant No. 1651722 as well through the NSF LTER Program 1637459, 2220863 (ARC), 1637686 (NWT), 1832042 (KBS), 2025849 (KNZ), 1636476 (BNZ), 1637685 (HBR), 1832210 (HFR), 2025755 (AND). We also acknowledge NSF grants 1637653 and 1754126 (INCyTE RCN), and DOE grant DESC0019037. We also acknowledge support through the USDA Forest Service Hubbard Brook Experimental Forest, North Woodstock, New Hampshie (USDA NIFA 2019-67019-29464) and Pacific Northwest Research Station, Corvallis, Oregon.
    Keywords: Carbon dioxide fertilization ; Carbon sequestration ; Carbon-nitrogen interactions ; Carbon-phosphorus interactions ; Climate change ; Long-term ecological research (LTER) ; Nitrogen cycle ; Phosphorus cycle ; Terrestrial ecosystem stoichiometry
    Repository Name: Woods Hole Open Access Server
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  • 6
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    Sporadic P limitation constrains microbial growth and facilitates SOM accumulation in the stoichiometrically coupled, acclimating microbe-plant-soil model (2022)
    Elsevier
    Details
    Publication Date: 2022-10-18
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Pold, G., Kwiatkowski, B. L., Rastetter, E. B., & Sistla, S. A. Sporadic P limitation constrains microbial growth and facilitates SOM accumulation in the stoichiometrically coupled, acclimating microbe-plant-soil model. Soil Biology & Biochemistry, 165, (2022): 108489, https://doi.org/10.1016/j.soilbio.2021.108489.
    Description: Requirements for biomass carbon (C), nitrogen (N), and phosphorus (P) constrain organism growth and are important agents for structuring ecosystems. Arctic tundra habitats are strongly nutrient limited as decomposition and recycling of nutrients are slowed by low temperature. Modeling interactions among these elemental cycles affords an opportunity to explore how disturbances such as climate change might differentially affect these nutrient cycles. Here we introduce a C–N–P-coupled version of the Stoichiometrically Coupled Acclimating Microbe-Plant-Soil (SCAMPS) model, “SCAMPS-CNP”, and a corresponding modified CN-only model, “SCAMPS-CN”. We compared how SCAMPS-CNP and the modified SCAMPS-CN models project a moderate (RCP 6.0) air warming scenario will impact tussock tundra nutrient availability and ecosystem C stocks. SCAMPS-CNP was characterized by larger SOM and smaller organism C stocks compared to SCAMPS-CN, and a greater reduction in ecosystem C stocks under warming. This difference can largely be attributed to a smaller microbial biomass in the CNP model, which, instead of being driven by direct costs of P acquisition, was driven by variable resource limitation due to asynchronous C, N, and P availability and demand. Warming facilitated a greater relative increase in plant and microbial biomass in SCAMPS-CNP, however, facilitated by increased extracellular enzyme pools and activity, which more than offset the metabolic costs associated with their production. Although the microbial community was able to flexibly adapt its stoichiometry and become more bacteria-like (N-rich) in both models, its stoichiometry deviated further from its target value in the CNP model because of the need to balance cellular NP ratio. Our results indicate that seasonality and asynchrony in resources affect predicted changes in ecosystem C storage under warming in these models, and therefore build on a growing body of literature indicating stoichiometry should be considered in carbon cycling projections.
    Description: This work was funded by the National Science Foundation Signals in the Soil grant number 1841610 to SAS and EBR.
    Keywords: Stoichiometry ; Modeling ; Microbial physiology ; Tundra ; Climate change
    Repository Name: Woods Hole Open Access Server
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  • 7
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    An approach to modeling resource optimization for substitutable and interdependent resources (2020)
    Elsevier
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Rastetter, E. B., & Kwiatkowski, B. L. An approach to modeling resource optimization for substitutable and interdependent resources. Ecological Modelling, 425, (2020): 109033, doi:10.1016/j.ecolmodel.2020.109033.
    Description: We develop a hierarchical approach to modeling organism acclimation to changing availability of and requirements for substitutable and interdependent resources. Substitutable resources are resources that fill the same metabolic or stoichiometric need of the organism. Interdependent resources are resources whose acquisition or expenditure are tightly linked (e.g., light, CO2, and water in photosynthesis and associated transpiration). We illustrate the approach by simulating the development of vegetation with four substitutable sources of N that differ only in the cost of their uptake and assimilation. As the vegetation develops, it uses the least expensive N source first then uses progressively more expensive N sources as the less expensive sources are depleted. Transition among N sources is based on the marginal yield of N per unit effort expended, including effort expended to acquire C to cover the progressively higher uptake costs. We illustrate the approach to interdependent resources by simulating the expenditure of effort to acquire light energy, CO2, and water to drive photosynthesis in vegetation acclimated to different conditions of soil water, atmospheric vapor pressure deficit, CO2 concentration, and light levels. The approach is an improvement on the resource optimization used in the earlier Multiple Element Limitation (MEL) model.
    Description: This work was supported in part by the National Science Foundation under NSF grants 1651722, 1637459, 1603560, 1556772, 1841608. Any Opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect those of the National Science Foundation.
    Keywords: Resource optimization ; Acclimation ; Substitutable resources ; Interdependent resources ; Resource limitation ; Multiple resource limitation
    Repository Name: Woods Hole Open Access Server
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  • 8
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    Modeling Carbon-Nutrient interactions during the early recovery of tundra after fire (2015)
    Wiley
    Details
    Publication Date: 2015-01-23
    Description: Fire frequency has dramatically increased in the tundra of northern Alaska, which has major implications for the carbon budget of the region and the functioning of these ecosystems that support important wildlife species. We investigated the post-fire succession of plant and soil carbon (C), nitrogen (N), and phosphorus (P) fluxes and stocks along a burn severity gradient in the 2007 Anaktuvuk River Fire scar in northern Alaska. Modeling results indicated that the early regrowth of post-fire tundra vegetation was limited primarily by its canopy photosynthetic potential, rather than nutrient availability, because of the initially low leaf area and relatively high inorganic N and P concentrations in soil. Our simulations indicated that the post-fire recovery of tundra vegetation was sustained predominantly by the uptake of residual inorganic N (i.e. in the remaining ash), and the redistribution of N and P from soil organic matter to vegetation. Although residual nutrients in ash were higher in the severe burn than the moderate burn, the moderate burn recovered faster because of the higher remaining biomass and consequent photosynthetic potential. Residual nutrients in ash allowed both burn sites to recover and exceed the unburned site in both aboveground biomass and production five years after the fire. The investigation of interactions among post-fire C, N, and P cycles has contributed to a mechanistic understanding of the response of tundra ecosystems to fire disturbance. Our study provided insight on how the trajectory of recovery of tundra from wildfire is regulated during early succession. # doi:10.1890/14-1921.1
    Print ISSN: 1051-0761
    Electronic ISSN: 1939-5582
    Topics: Biology
    Published by Wiley on behalf of The Ecological Society of America (ESA).
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  • 9
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    Recovery of arctic tundra from thermal erosion disturbance is constrained by nutrient accumulation: a modeling analysis (2014)
    Wiley
    Details
    Publication Date: 2014-12-04
    Description: We calibrated the Multiple Element Limitation (MEL) model to Alaskan arctic tundra to simulate recovery of thermal erosion features (TEFs) caused by permafrost thaw and mass wasting. TEFs could significantly alter regional carbon (C) and nutrient budgets because permafrost soils contain large stocks of soil organic matter (SOM) and TEFs are expected to become more frequent as the climate warms. We simulated recovery following TEF stabilization and did not address initial, short-term losses of C and nutrients during TEF formation. To capture the variability among and within TEFs, we modeled a range of post-stabilization conditions by varying the initial size of SOM stocks and nutrient supply rates. Simulations indicate that nitrogen (N) losses after the TEF stabilizes are small, but phosphorus (P) losses continue. Vegetation biomass recovered 90% of its undisturbed C, N, and P stocks in 100 years using nutrients mineralized from SOM. Because of low litter inputs but continued decomposition, younger SOM continued to be lost for 10 years after the TEF began to recover, but recovered to about 84% of its undisturbed amount in 100 years. The older recalcitrant SOM in mineral soil continued to be lost throughout the 100-year simulation. Simulations suggest that biomass recovery depended on the amount of SOM remaining after disturbance. Recovery was initially limited by the photosynthetic capacity of vegetation, but became co-limited by N and P once a plant canopy developed. Biomass and SOM recovery was enhanced by increasing nutrient supplies, but the magnitude, source, and controls on these supplies are poorly understood. Faster mineralization of nutrients from SOM (e.g., by warming) enhanced vegetation recovery but delayed recovery of SOM. Taken together, these results suggest that although vegetation and surface SOM on TEFs recovered quickly (25 and 100 years respectively), the recovery of deep, mineral soil SOM took centuries and represented a major ecosystem C loss. # doi:10.1890/14-1323.1
    Print ISSN: 1051-0761
    Electronic ISSN: 1939-5582
    Topics: Biology
    Published by Wiley on behalf of The Ecological Society of America (ESA).
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  • 10
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    The role of down-slope water and nutrient fluxes in the response of Arctic hill slopes to climate change (2004)
    Springer
    Details
    Publication Date: 2004-05-01
    Print ISSN: 0168-2563
    Electronic ISSN: 1573-515X
    Topics: Chemistry and Pharmacology , Geosciences
    Published by Springer
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