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Search Results: 1 - 10 of 10415 matches for " Marcos;Trumbore "
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Models of soil organic matter decomposition: the SoilR package, version 1.0
C. A. Sierra, M. Müller,S. E. Trumbore
Geoscientific Model Development (GMD) & Discussions (GMDD) , 2012, DOI: 10.5194/gmd-5-1045-2012
Abstract: Soil organic matter decomposition is a very important process within the Earth system because it controls the rates of mineralization of carbon and other biogeochemical elements, determining their flux to the atmosphere and the hydrosphere. SoilR is a modeling framework that contains a library of functions and tools for modeling soil organic matter decomposition under the R environment for computing. It implements a variety of model structures and tools to represent carbon storage and release from soil organic matter. In SoilR, organic matter decomposition is represented as a linear system of ordinary differential equations that generalizes the structure of most compartment-based decomposition models. A variety of functions is also available to represent environmental effects on decomposition rates. This document presents the conceptual basis for the functions implemented in the package. It is complementary to the help pages released with the software.
Models of soil organic matter decomposition: the SOILR package, version 1.0
C. A. Sierra,M. Müller,S. E. Trumbore
Geoscientific Model Development Discussions , 2012, DOI: 10.5194/gmdd-5-993-2012
Abstract: Organic matter decomposition is a very important process within the Earth System because it controls the rates of mineralization of carbon and other biogeochemical elements, determining their flux to the atmosphere and the hydrosphere. SOILR is a modeling framework that contains a library of functions and tools for modeling soil organic matter decomposition under the R environment for computing. It implements a variety of model structures and tools to represent carbon storage and release from soil organic matter. In SOILR organic matter decomposition is represented as a linear system of ordinary differential equations that generalizes the structure of most compartment-based decomposition models. A variety of functions is also available to represent environmental effects on decomposition rates. This document presents the conceptual basis for the functions implemented in the package. It is complementary to the help pages released with the software.
Estimation of biomass and carbon stocks: the case of the Atlantic Forest
Vieira, Simone Aparecida;Alves, Luciana Ferreira;Aidar, Marcos;Araújo, Luciana Spinelli;Baker, Tim;Batista, Jo?o Luís Ferreira;Campos, Mariana Cruz;Camargo, Plinio Barbosa;Chave, Jerome;Delitti, Welington Braz Carvalho;Higuchi, Niro;Honorio, Euridice;Joly, Carlos Alfredo;Keller, Michael;Martinelli, Luiz Antonio;Mattos, Eduardo Arcoverde de;Metzker, Thiago;Phillips, Oliver;Santos, Flavio Antonio Maes dos;Shimabukuro, M?nica Takako;Silveira, Marcos;Trumbore, Susan Elizabeth;
Biota Neotropica , 2008, DOI: 10.1590/S1676-06032008000200001
Abstract: the main objective of this paper is to present and discuss the best methods to estimate live above ground biomass in the atlantic forest. the methods presented and conclusions are the products of a workshop entitled "estimation of biomass and carbon stocks: the case of atlantic rain forest". aboveground biomass (agb) in tropical forests is mainly contained in trees. tree biomass is a function of wood volume, obtained from the diameter and height, architecture and wood density (dry weight per unit volume of fresh wood). it can be quantified by the direct (destructive) or indirect method where the biomass quantification is estimated using mathematical models. the allometric model can be site specific when elaborated to a particular ecosystem or general that can be used in different sites. for the atlantic forest, despite the importance of it, there are only two direct measurements of tree biomass, resulting in allometric models specific for this ecosystem. to select one or other of the available models in the literature to estimate agb it is necessary take into account what is the main question to be answered and the ease with which it is possible to measure the independent variables in the model. models that present more accurate estimates should be preferred. however, more simple models (those with one independent variable, usually dbh) can be used when the focus is monitoring the variation in carbon storage through the time. our observations in the atlantic forest suggest that pan-tropical relations proposed by chave et al. (2005) can be confidently used to estimated tree biomass across biomes as long as tree diameter (dbh), height, and wood density are accounted for in the model. in atlantic forest, we recommend the quantification of biomass of lianas, bamboo, palms, tree ferns and epiphytes, which are an important component in this ecosystem. this paper is an outcome of the workshop entitled "estimation of biomass and carbon stocks: the case of atlantic rain fore
How old are large Brazil-nut trees (Bertholletia excelsa) in the Amazon?
Camargo, P.B. de;Salom?o, R. de P.;Trumbore, S.;Martinelli, L.A.;
Scientia Agricola , 1994, DOI: 10.1590/S0103-90161994000200028
Abstract: the age of a large brazil-nut tree (bertholletia excelsa) is measured by radiocarbon dating, and a discussion is made about their importance in the amazon rain-forest ecosystem.
Predicting decadal trends and transient responses of radiocarbon storage and fluxes in a temperate forest soil
C. A. Sierra,S. E. Trumbore,E. A. Davidson,S. D. Frey
Biogeosciences Discussions , 2012, DOI: 10.5194/bgd-9-2197-2012
Abstract: Representing the response of soil carbon dynamics to global environmental change requires the incorporation of multiple tools in the development of predictive models. An important tool to construct and test models is the incorporation of bomb radiocarbon in soil organic matter during the past decades. In this manuscript, we combined radiocarbon data and a previously developed empirical model to explore decade-scale soil carbon dynamics in a temperate forest ecosystem at the Harvard Forest, Massachusetts, USA. We evaluated the contribution of different soil C fractions to both total soil CO2 efflux and microbially-respired C. We tested the performance of the model based on measurable soil organic matter fractions against a decade of radiocarbon measurements. The model was then challenged with radiocarbon measurements from a warming and N addition experiment to test multiple hypotheses about the different response of soil C fractions to the experimental manipulations. Our results showed that the empirical model satisfactorily predicts the trends of radiocarbon in litter, density fractions, and respired CO2 observed over a decade in the soils not subjected to manipulation. However, the model, modified with prescribed relationships for temperature and decomposition rates, predicted most but not all the observations from the field experiment where soil temperatures and nitrogen levels were increased, suggesting that a larger degree of complexity and mechanistic relations need to be added to the model to predict short-term responses and transient dynamics.
Predicting decadal trends and transient responses of radiocarbon storage and fluxes in a temperate forest soil
C. A. Sierra, S. E. Trumbore, E. A. Davidson, S. D. Frey, K. E. Savage,F. M. Hopkins
Biogeosciences (BG) & Discussions (BGD) , 2012,
Abstract: Representing the response of soil carbon dynamics to global environmental change requires the incorporation of multiple tools in the development of predictive models. An important tool to construct and test models is the incorporation of bomb radiocarbon in soil organic matter during the past decades. In this manuscript, we combined radiocarbon data and a previously developed empirical model to explore decade-scale soil carbon dynamics in a temperate forest ecosystem at the Harvard Forest, Massachusetts, USA. We evaluated the contribution of different soil C fractions to both total soil CO2 efflux and microbially respired C. We tested the performance of the model based on measurable soil organic matter fractions against a decade of radiocarbon measurements. The model was then challenged with radiocarbon measurements from a warming and N addition experiment to test multiple hypotheses about the different response of soil C fractions to the experimental manipulations. Our results showed that the empirical model satisfactorily predicts the trends of radiocarbon in litter, density fractions, and respired CO2 observed over a decade in the soils not subjected to manipulation. However, the model, modified with prescribed relationships for temperature and decomposition rates, predicted most but not all the observations from the field experiment where soil temperatures and nitrogen levels were increased, suggesting that a larger degree of complexity and mechanistic relations need to be added to the model to predict short-term responses and transient dynamics.
Mass Spectrum in the Minimal Supersymmetric 3-3-1 Model  [PDF]
Marcos Cardoso Rodriguez
Journal of Modern Physics (JMP) , 2011, DOI: 10.4236/jmp.2011.210149
Abstract: We consider the minimal supersymmetric extension of the 3-3-1 model. We study the mass spectrum of this model in the fermionic and gauge bosons sectors without the antisextet. We also present some phenomenological consequences of this model at colliders such as Large Hadron Collider (LHC) and International Linear Collider (ILC).
Enunciative Texts Present in Physical Issues of Editions of a Brazilian National Exam as Possible Triggers of Socio-Scientific Discussions  [PDF]
Marcos Fernandes-Sobrinho
Creative Education (CE) , 2018, DOI: 10.4236/ce.2018.92021
Abstract: In this article we identify and analyze texts on physics questions in seven editions of a Brazilian national exam, with the purpose of bringing contributions to teaching planning and pedagogical actions with the perspective of supporting the creation of socio-scientific discussions (SSD), capable of inducing students in their citizenship development, in view of the difficulties of being worked in Sciences/Physics teaching environments appointed by the literature. A Brazilian state was chosen as a field, whose locus included six municipalities and 12 public institutions of basic education. Given that the results seem to distort the reality of the school context, the aforementioned difficulties were then theoretically and empirically disassembled, proving to be potentially minimized with the establishment of trails that enable the teacher to work on SSD identified in materials of easy and universal access, which contributes with advancement in the field of Science-Technology-Society education.
Linking agricultural crop management and air quality models for regional to national-scale nitrogen assessments
A. Angert, J. Muhr, R. Negron Juarez, W. Alegria Mu oz, G. Kraemer, J. Ramirez Santillan, J. Q. Chambers,S. E. Trumbore
Biogeosciences (BG) & Discussions (BGD) , 2012,
Abstract: Understanding the variability and the current value of the Dole Effect, which has been used to infer past changes in biospheric productivity, requires accurate information on the isotopic discrimination associated with respiratory oxygen consumption in each of the biosphere components. Respiration in tree stems is an important component of the land carbon cycle. Here we measured, for the first time, the discrimination associated with tree stem oxygen uptake. The measurements included tropical forest trees, which are major contributors to the global fluxes of carbon and oxygen. We found discrimination in the range of 12.6–21.5‰, indicating both diffusion limitation, resulting in O2 discrimination values below 20‰, and alternative oxidase respiration, which resulted in discrimination values greater than 20‰. Discrimination varied seasonally, between and within tree species. Calculations based on these results show that variability in woody plants discrimination can result in significant variations in the global Dole Effect.
Internal respiration of Amazon tree stems greatly exceeds external CO2 efflux
A. Angert, J. Muhr, R. Negron Juarez, W. Alegria Mu oz, G. Kraemer, J. Ramirez Santillan, E. Barkan, S. Mazeh, J. Q. Chambers,S. E. Trumbore
Biogeosciences (BG) & Discussions (BGD) , 2012,
Abstract: Respiration in tree stems is an important component of forest carbon balance. The rate of CO2 efflux from the stem has often been assumed to be a measure of stem respiration. However, recent work in temperate forests has demonstrated that stem CO2 efflux can either overestimate or underestimate respiration rate because of emission or removal of CO2 by transport in xylem water. Here, we studied gas exchange from stems of tropical forest trees using a new approach to better understand respiration in an ecosystem that plays a key role in the global carbon cycle. Our main questions were (1) is internal CO2 transport important in tropical trees, and, if so, (2) does this transport result in net release of CO2 respired in the roots at the stem, or does it cause the opposite effect of net removal of stem-respired CO2? To answer these questions, we measured the ratio of stem CO2 efflux to O2 influx. This ratio, defined here as apparent respiratory quotient (ARQ), is expected to equal 1.0 if carbohydrates are the substrate for respiration, and the net transport of CO2 in the xylem water is negligible. Using a stem chamber approach to quantifying ARQ, we found values of 0.66 ± 0.18. These low ARQ values indicate that a large portion of respired CO2 (~ 35%) is not emitted locally, and is probably transported upward in the stem. ARQ values of 0.21 ± 0.10 were found for the steady-state gas concentration within the stem, sampled by in-stem equilibration probes. These lower values may result from the proximity to the xylem water stream. In contrast, we found ARQ values of 1.00 ± 0.13 for soil respiration. Our results indicate the existence of a considerable internal flux of CO2 in the stems of tropical trees. If the transported CO2 is used in the canopy as a substrate for photosynthesis, it could account for up to 10% of the C fixed by the tree, and perhaps serve as a mechanism that buffers the response of the tree to changing CO2 levels. Our results also indicate, in agreement with previous work, that the widely used CO2 efflux approach for determining stem respiration is unreliable. We demonstrate here a field applicable approach for measuring the O2 uptake rate, which we suggest to be a more appropriate method to estimate stem respiration rates.
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