ORCID Profile
0000-0002-7832-7009
Current Organisation
Northern Arizona University
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Publisher: Springer Science and Business Media LLC
Date: 08-09-2011
DOI: 10.1007/S00442-011-2106-X
Abstract: Model-data fusion is a powerful framework by which to combine models with various data streams (including observations at different spatial or temporal scales), and account for associated uncertainties. The approach can be used to constrain estimates of model states, rate constants, and driver sensitivities. The number of applications of model-data fusion in environmental biology and ecology has been rising steadily, offering insights into both model and data strengths and limitations. For reliable model-data fusion-based results, however, the approach taken must fully account for both model and data uncertainties in a statistically rigorous and transparent manner. Here we review and outline the cornerstones of a rigorous model-data fusion approach, highlighting the importance of properly accounting for uncertainty. We conclude by suggesting a code of best practices, which should serve to guide future efforts.
Publisher: Wiley
Date: 29-11-2013
DOI: 10.1111/NPH.12042
Abstract: Nonstructural carbohydrate reserves support tree metabolism and growth when current photosynthates are insufficient, offering resilience in times of stress. We monitored stemwood nonstructural carbohydrate (starch and sugars) concentrations of the dominant tree species at three sites in the northeastern United States. We estimated the mean age of the starch and sugars in a subset of trees using the radiocarbon ( 14 C) bomb spike. With these data, we then tested different carbon (C) allocation schemes in a process‐based model of forest C cycling. We found that the nonstructural carbohydrates are both highly dynamic and about a decade old. Seasonal dynamics in starch (two to four times higher in the growing season, lower in the dormant season) mirrored those of sugars. Radiocarbon‐based estimates indicated that the mean age of the starch and sugars in red maple ( Acer rubrum ) was 7–14 yr. A two‐pool (fast and slow cycling reserves) model structure gave reasonable estimates of the size and mean residence time of the total NSC pool, and greatly improved model predictions of interannual variability in woody biomass increment, compared with zero‐ or one‐pool structures used in the majority of existing models. This highlights the importance of nonstructural carbohydrates in the context of forest ecosystem carbon cycling.
Publisher: Wiley
Date: 27-08-2013
DOI: 10.1111/NPH.12448
Abstract: The allocation of nonstructural carbon ( NSC ) to growth, metabolism and storage remains poorly understood, but is critical for the prediction of stress tolerance and mortality. We used the radiocarbon ( 14 C ) ‘bomb spike’ as a tracer of substrate and age of carbon in stemwood NSC , CO 2 emitted by stems, tree ring cellulose and stump sprouts regenerated following harvesting in mature red maple trees. We addressed the following questions: which factors influence the age of stemwood NSC ? to what extent is stored vs new NSC used for metabolism and growth? and, is older, stored NSC available for use? The mean age of extracted stemwood NSC was 10 yr. More vigorous trees had both larger and younger stemwood NSC pools. NSC used to support metabolism (stem CO 2 ) was 1–2 yr old in spring before leaves emerged, but reflected current‐year photosynthetic products in late summer. The tree ring cellulose 14 C age was 0.9 yr older than direct ring counts. Stump sprouts were formed from NSC up to 17 yr old. Thus, younger NSC is preferentially used for growth and day‐to‐day metabolic demands. More recently stored NSC contributes to annual ring growth and metabolism in the dormant season, yet decade‐old and older NSC is accessible for regrowth.
Publisher: Copernicus GmbH
Date: 17-01-2019
Abstract: Abstract. The ratio of CO2 efflux to O2 influx (ARQ, apparent respiratory quotient) in tree stems is expected to be 1.0 for carbohydrates, the main substrate supporting stem respiration. In previous studies of stem fluxes, ARQ values below 1.0 were observed and hypothesized to indicate retention of respired carbon within the stem. Here, we demonstrate that stem ARQ 1.0 values are common across 85 tropical, temperate, and Mediterranean forest trees from nine different species. Mean ARQ values per species per site ranged from 0.39 to 0.78, with an overall mean of 0.59. Assuming that O2 uptake provides a measure of in situ stem respiration (due to the low solubility of O2), the overall mean indicates that on average 41 % of CO2 respired in stems is not emitted from the local stem surface. The instantaneous ARQ did not vary with sap flow. ARQ values of incubated stem cores were similar to those measured in stem chambers on intact trees. We therefore conclude that dissolution of CO2 in the xylem sap and transport away from the site of respiration cannot explain the low ARQ values. We suggest refixation of respired CO2 in biosynthesis reactions as possible mechanism for low ARQ values.
Location: United States of America
Location: United States of America
No related grants have been discovered for Mariah Carbone.