Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 16 de 16
Filtrar
Más filtros

País/Región como asunto
Intervalo de año de publicación
1.
Proc Natl Acad Sci U S A ; 121(33): e2310157121, 2024 Aug 13.
Artículo en Inglés | MEDLINE | ID: mdl-39102539

RESUMEN

The Amazon forest contains globally important carbon stocks, but in recent years, atmospheric measurements suggest that it has been releasing more carbon than it has absorbed because of deforestation and forest degradation. Accurately attributing the sources of carbon loss to forest degradation and natural disturbances remains a challenge because of the difficulty of classifying disturbances and simultaneously estimating carbon changes. We used a unique, randomized, repeated, very high-resolution airborne laser scanning survey to provide a direct, detailed, and high-resolution partitioning of aboveground carbon gains and losses in the Brazilian Arc of Deforestation. Our analysis revealed that disturbances directly attributed to human activity impacted 4.2% of the survey area while windthrows and other disturbances affected 2.7% and 14.7%, respectively. Extrapolating the lidar-based statistics to the study area (544,300 km2), we found that 24.1, 24.2, and 14.5 Tg C y-1 were lost through clearing, fires, and logging, respectively. The losses due to large windthrows (21.5 Tg C y-1) and other disturbances (50.3 Tg C y-1) were partially counterbalanced by forest growth (44.1 Tg C y-1). Our high-resolution estimates demonstrated a greater loss of carbon through forest degradation than through deforestation and a net loss of carbon of 90.5 ± 16.6 Tg C y-1 for the study region attributable to both anthropogenic and natural processes. This study highlights the role of forest degradation in the carbon balance for this critical region in the Earth system.


Asunto(s)
Carbono , Conservación de los Recursos Naturales , Bosques , Brasil/epidemiología , Carbono/metabolismo , Humanos , Árboles/crecimiento & desarrollo , Ciclo del Carbono
2.
Am J Respir Crit Care Med ; 209(10): 1238-1245, 2024 05 15.
Artículo en Inglés | MEDLINE | ID: mdl-38190701

RESUMEN

Rationale: The association of acute cellular rejection (ACR) with chronic lung allograft dysfunction (CLAD) in lung transplant recipients has primarily been described before consensus recommendations incorporating restrictive phenotypes. Furthermore, the association of the degree of molecular allograft injury during ACR with CLAD or death remains undefined. Objectives: To investigate the association of ACR with the risk of CLAD or death and to further investigate if this risk depends on the degree of molecular allograft injury. Methods: This multicenter, prospective cohort study included 188 lung transplant recipients. Subjects underwent serial plasma collections for donor-derived cell-free DNA (dd-cfDNA) at prespecified time points and bronchoscopy. Multivariable Cox proportional-hazards analysis was conducted to analyze the association of ACR with subsequent CLAD or death as well as the association of dd-cfDNA during ACR with risk of CLAD or death. Additional outcomes analyses were performed with episodes of ACR categorized as "high risk" (dd-cfDNA ⩾ 1%) and "low risk" (dd-cfDNA < 1%). Measurements and Main Results: In multivariable analysis, ACR was associated with the composite outcome of CLAD or death (hazard ratio [HR], 2.07 [95% confidence interval (CI), 1.05-4.10]; P = 0.036). Elevated dd-cfDNA ⩾ 1% at ACR diagnosis was independently associated with increased risk of CLAD or death (HR, 3.32; 95% CI, 1.31-8.40; P = 0.012). Patients with high-risk ACR were at increased risk of CLAD or death (HR, 3.13; 95% CI, 1.41-6.93; P = 0.005), whereas patients with low-risk status ACR were not. Conclusions: Patients with ACR are at higher risk of CLAD or death, but this may depend on the degree of underlying allograft injury at the molecular level. Clinical trial registered with www.clinicaltrials.gov (NCT02423070).


Asunto(s)
Rechazo de Injerto , Trasplante de Pulmón , Humanos , Trasplante de Pulmón/efectos adversos , Masculino , Femenino , Persona de Mediana Edad , Estudios Prospectivos , Adulto , Aloinjertos , Ácidos Nucleicos Libres de Células/sangre , Modelos de Riesgos Proporcionales , Factores de Riesgo , Estudios de Cohortes , Anciano , Enfermedad Aguda
3.
Am J Respir Crit Care Med ; 209(6): 727-737, 2024 03 15.
Artículo en Inglés | MEDLINE | ID: mdl-38117233

RESUMEN

Rationale: Plasma cell-free DNA levels correlate with disease severity in many conditions. Pretransplant cell-free DNA may risk stratify lung transplant candidates for post-transplant complications. Objectives: To evaluate if pretransplant cell-free DNA levels and tissue sources identify patients at high risk of primary graft dysfunction and other pre- and post-transplant outcomes. Methods: This multicenter, prospective cohort study recruited 186 lung transplant candidates. Pretransplant plasma samples were collected to measure cell-free DNA. Bisulfite sequencing was performed to identify the tissue sources of cell-free DNA. Multivariable regression models determined the association between cell-free DNA levels and the primary outcome of primary graft dysfunction and other transplant outcomes, including Lung Allocation Score, chronic lung allograft dysfunction, and death. Measurements and Main Results: Transplant candidates had twofold greater cell-free DNA levels than healthy control patients (median [interquartile range], 23.7 ng/ml [15.1-35.6] vs. 12.9 ng/ml [9.9-18.4]; P < 0.0001), primarily originating from inflammatory innate immune cells. Cell-free DNA levels and tissue sources differed by native lung disease category and correlated with the Lung Allocation Score (P < 0.001). High pretransplant cell-free DNA increased the risk of primary graft dysfunction (odds ratio, 1.60; 95% confidence interval [CI], 1.09-2.46; P = 0.0220), and death (hazard ratio, 1.43; 95% CI, 1.07-1.92; P = 0.0171) but not chronic lung allograft dysfunction (hazard ratio, 1.37; 95% CI, 0.97-1.94; P = 0.0767). Conclusions: Lung transplant candidates demonstrate a heightened degree of tissue injury with elevated cell-free DNA, primarily originating from innate immune cells. Pretransplant plasma cell-free DNA levels predict post-transplant complications.


Asunto(s)
Ácidos Nucleicos Libres de Células , Trasplante de Pulmón , Disfunción Primaria del Injerto , Humanos , Estudios Prospectivos , Estudios Retrospectivos , Gravedad del Paciente
4.
J Infect Dis ; 2024 Aug 14.
Artículo en Inglés | MEDLINE | ID: mdl-39140311

RESUMEN

BACKGROUND: Chronic norovirus infection (CNI) causes significant morbidity in immunocompromised patients. No effective prevention or treatment currently exists. METHODS: Two patients with inborn errors of immunity, X- linked severe combined immunodeficiency (X-SCID) and DOCK8 deficiency, were followed longitudinally for clinical course, immune reconstitution, norovirus-specific T cell (NST) response, B cell reconstitution, and norovirus-specific antibody production. Samples were obtained in the peri-hematopoietic stem cell transplant setting (HSCT) before and after CNI clearance. The norovirus strain causing CNI was followed longitudinally for norovirus stool viral loads and sequencing. RESULTS: The noroviruses were identified as GII.4 Sydney[P4 New Orleans] in one patient and GII.17[P17] in the other. An exacerbation of diarrhea post-HSCT in the patient with X-SCID was consistent with norovirus infection but not with graft-vs-host-disease on pathologic samples. Both patients recovered polyfunctional NSTs in the CD4 and CD8 T cell compartments which recognized multiple norovirus structural and non-structural viral antigens. T cell responses were minimal during active CNI but detectable after resolution. Mapping of norovirus-specific T cell responses between the patient with DOCK8 and his matched sibling donor were nearly identical. B cell reconstitution or new endogenous antibody production for IgA or IgG were not observed. CONCLUSION: This report is the first to demonstrate reconstitution of norovirus-specific T cell immunity after HSCT closely temporally aligned with clearance of CNI suggesting that cellular immunity is sufficient for norovirus clearance.

5.
Am J Transplant ; 2024 Apr 19.
Artículo en Inglés | MEDLINE | ID: mdl-38643944

RESUMEN

Reactivation or primary infection with double-stranded DNA viruses is common in recipients of solid organ transplants (SOTs) and is associated with significant morbidity and mortality. Treatment with conventional antiviral medications is limited by toxicities, resistance, and a lack of effective options for adenovirus (ADV) and BK polyomavirus (BKPyV). Virus-specific T cells (VSTs) have been shown to be an effective treatment for infections with ADV, BKPyV, cytomegalovirus (CMV), and Epstein-Barr virus (EBV). Most of these studies have been conducted in stem cell recipients, and no large studies have been published in the SOT population to date. In this study, we report on the outcome of quadrivalent third-party VST infusions in 98 recipients of SOTs in the context of an open-label phase 2 trial. The 98 patients received a total of 181 infusions, with a median of 2 infusions per patient. The overall response rate was 45% for BKPyV, 65% for cytomegalovirus, 68% for ADV, and 61% for Epstein-Barr virus. Twenty percent of patients with posttransplant lymphoproliferative disorder had a complete response and 40% of patients had a partial response. All the VST infusions were well tolerated. We conclude that VSTs are safe and effective in the treatment of viral infections in SOT recipients.

6.
Clin Immunol ; 266: 110332, 2024 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-39069111

RESUMEN

Both non-malignant and malignant lymphoproliferative disorders (LPD) are commonly seen in patients with inborn errors of immunity (IEI), which may be the presenting manifestations or may develop during the IEI disease course. Here we review the clinical, histopathological, and molecular features of benign and malignant LPD associated with IEI and recognize the diagnostic challenges.


Asunto(s)
Enfermedades del Sistema Inmune , Trastornos Linfoproliferativos , Niño , Humanos , Trastornos Linfoproliferativos/inmunología , Trastornos Linfoproliferativos/genética , Enfermedades del Sistema Inmune/complicaciones , Enfermedades del Sistema Inmune/genética
7.
Pediatr Blood Cancer ; 71(4): e30871, 2024 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-38279890

RESUMEN

BACKGROUND: Drug shortages are a common issue that healthcare systems face and can result in adverse health outcomes for patients requiring inferior alternate treatment. The United States recently experienced a national drug shortage of intravenous immunoglobulin (IVIG). Several reported strategies to address the IVIG and other drug shortages have been proposed; however, there is a lack of evidence-based methods for protocol development and implementation. OBJECTIVE: To evaluate the efficacy of introducing a multidisciplinary task force and tier system of indications and to minimize adverse effects during a shortage of IVIG. METHODS: Faculty members across disciplines with expertise in IVIG use were invited to participate in a task force to address the shortage and ensure adequate supply for emergent indications. A tier system of IVIG indications was established according to the severity of diagnosis, urgency of indication, and quality of supporting evidence. Based on inventory, indications in selected tiers were auto-approved. Orders that could not be automatically approved were escalated for task force review. RESULTS: Overall, there were 342 distinct requests for IVIG during the study period (August 1, 2019 to December 31, 2019). All Tier 1 indications were approved. Of all requests, only 2.6% (9) of requests were denied, none of which resulted in adverse effects based on retrospective chart review. Seven patients who regularly receive IVIG had possible adverse effects due to dose reduction or spacing of treatment; however, each complication was multifactorial and not attributed to the shortage or tier system implementation alone. CONCLUSION: Implementation of a multidisciplinary task force and tier system to appropriately triage high-priority indications for limited pharmaceutical agents should be considered in health institutions faced with a drug shortage.


Asunto(s)
Efectos Colaterales y Reacciones Adversas Relacionados con Medicamentos , Inmunoglobulinas Intravenosas , Niño , Humanos , Inmunoglobulinas Intravenosas/efectos adversos , Estudios Retrospectivos , Atención Terciaria de Salud , Centros de Atención Terciaria , Inyecciones Intravenosas , Efectos Colaterales y Reacciones Adversas Relacionados con Medicamentos/tratamiento farmacológico
8.
Clin Podiatr Med Surg ; 41(3): 391-405, 2024 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-38789160

RESUMEN

Fifth metatarsal features are the most common fractures in the foot. They have a long history that has resulted in many classification systems and little consensus on appropriate treatment. Although there is some agreement among experts, there are also many questions yet to be answered. There is a general consensus that dancer's fractures and zone 1 fractures can generally be treated nonoperatively. There is much more debate about zone 2 and 3 fractures and appropriate treatment guidelines. The authors review the current literature and give the recommendation for treatment based on their experience in a community-based private practice.


Asunto(s)
Fracturas Óseas , Huesos Metatarsianos , Humanos , Huesos Metatarsianos/lesiones , Fracturas Óseas/terapia , Fracturas Óseas/clasificación , Fijación Interna de Fracturas/métodos , Traumatismos de los Pies/terapia
9.
Transplant Cell Ther ; 30(5): 475-487, 2024 May.
Artículo en Inglés | MEDLINE | ID: mdl-38447751

RESUMEN

Pharmacovigilance (PV), also known as drug safety, is the science of risk management involving the detection, assessment, understanding, and prevention of adverse effects related to a medication. This discipline has traditionally focused on the postmarketing period, with less attention to early-phase clinical trials. However, during the immunotherapy and cellular therapy investigational stage, regulatory agencies are increasingly emphasizing the need to identify and characterize safety signals earlier in clinical development as part of a comprehensive safety surveillance plan. Compliance with PV and safety regulations are further heightened as cell and gene therapy (CGT) trials grow in complexity and scope owing to ever-changing and increasingly rigorous regulatory mandates. Based on this changing landscape, a critical aspect of early-phase trials of cellular products where significant safety events are anticipated is to ensure that every effort is made to protect clinical trial participants by maximizing attention to the risk-versus-benefit profile. This includes the development of robust plans for safety surveillance that provide a continual assessment of safety signals to enable safety reporting to regulatory bodies and the Food and Drug Administration, a regular analysis of aggregate safety data, and a plan to communicate safety findings. This report focuses on PV in early-phase clinical trials of first-in-human investigational products sponsored by academic centers in which the availability of PV resources and subject matter experts is limited. To more fully understand the challenges of CGT PV oversight within pediatric academic medical centers conducting early-phase clinical trials, a working group from institutions participating in the Consortium for Pediatric Cellular Immunotherapy composed of faculty and regulatory professionals was convened to compare experiences, identify best practices, and review published literature to identify commonalities and opportunities for alignment. Here we present guidelines on PV planning in early-phase CGT clinical trials occurring in academic medical centers and offer strategies to mitigate risk to trial participants. Standards to address regulatory requirements and governance for safety signal identification and risk assessment are discussed.


Asunto(s)
Tratamiento Basado en Trasplante de Células y Tejidos , Inmunoterapia , Humanos , Tratamiento Basado en Trasplante de Células y Tejidos/normas , Tratamiento Basado en Trasplante de Células y Tejidos/métodos , Inmunoterapia/efectos adversos , Inmunoterapia/legislación & jurisprudencia , Inmunoterapia/métodos , Ensayos Clínicos como Asunto/legislación & jurisprudencia , Farmacovigilancia , Vigilancia de Productos Comercializados
10.
J Heart Lung Transplant ; 43(9): 1374-1382, 2024 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-38705500

RESUMEN

BACKGROUND: Lung transplant recipients are traditionally monitored with pulmonary function testing (PFT) and lung biopsy to detect post-transplant complications and guide treatment. Plasma donor-derived cell free DNA (dd-cfDNA) is a novel molecular approach of assessing allograft injury, including subclinical allograft dysfunction. The aim of this study was to determine if episodes of extreme molecular injury (EMI) in lung transplant recipients increases the risk of chronic lung allograft dysfunction (CLAD) or death. METHODS: This multicenter prospective cohort study included 238 lung transplant recipients. Serial plasma samples were collected for dd-cfDNA measurement by shotgun sequencing. EMI was defined as a dd-cfDNA above the third quartile of levels observed for acute rejection (dd-cfDNA level of ≥5% occurring after 45 days post-transplant). EMI was categorized as Secondary if associated with co-existing acute rejection, infection or PFT decline; or Primary if not associated with these conditions. RESULTS: EMI developed in 16% of patients at a median 343.5 (IQR: 177.3-535.5) days post-transplant. Over 50% of EMI episodes were classified as Primary. EMI was associated with an increased risk of severe CLAD or death (HR: 2.78, 95% CI: 1.26-6.22, p = 0.012). The risk remained consistent for the Primary EMI subgroup (HR: 2.34, 95% CI 1.18-4.85, p = 0.015). Time to first EMI episode was a significant predictor of the likelihood of developing CLAD or death (AUC=0.856, 95% CI=0.805-0.908, p < 0.001). CONCLUSIONS: Episodes of EMI in lung transplant recipients are often isolated and may not be detectable with traditional clinical monitoring approaches. EMI is associated with an increased risk of severe CLAD or death, independent of concomitant transplant complications.


Asunto(s)
Ácidos Nucleicos Libres de Células , Rechazo de Injerto , Trasplante de Pulmón , Donantes de Tejidos , Humanos , Trasplante de Pulmón/efectos adversos , Masculino , Femenino , Estudios Prospectivos , Persona de Mediana Edad , Ácidos Nucleicos Libres de Células/sangre , Aloinjertos , Enfermedad Crónica , Adulto , Disfunción Primaria del Injerto/sangre , Disfunción Primaria del Injerto/diagnóstico , Disfunción Primaria del Injerto/etiología , Disfunción Primaria del Injerto/epidemiología , Factores de Riesgo , Estudios de Seguimiento , Medición de Riesgo/métodos
11.
Transplant Direct ; 10(7): e1669, 2024 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-38953039

RESUMEN

Background: A prior single-center, retrospective cohort study identified baseline lung allograft dysfunction (BLAD) as a risk factor for death in bilateral lung transplant recipients. In this multicenter prospective cohort study, we test the association of BLAD with death in bilateral lung transplant recipients, identify clinical risk factors for BLAD, and assess its association with allograft injury on the molecular level. Methods: This multicenter, prospective cohort study included 173 bilateral lung transplant recipients that underwent serial pulmonary function testing and plasma collection for donor-derived cell-free DNA at prespecified time points. BLAD was defined as failure to achieve ≥80% predicted for both forced expiratory volume in 1 s and forced vital capacity after lung transplant, on 2 consecutive measurements at least 3 mo apart. Results: BLAD was associated with increased risk of death (hazard ratio, 1.97; 95% confidence interval [CI], 1.05-3.69; P = 0.03) but not chronic lung allograft dysfunction alone (hazard ratio, 1.60; 95% CI, 0.87-2.95; P = 0.13). Recipient obesity (odds ratio, 1.69; 95% CI, 1.15-2.80; P = 0.04) and donor age (odds ratio, 1.03; 95% CI, 1.02-1.05; P = 0.004) increased the risk of developing BLAD. Patients with BLAD did not demonstrate higher log10(donor-derived cell-free DNA) levels compared with no BLAD (slope [SE]: -0.0095 [0.0007] versus -0.0109 [0.0007]; P = 0.15). Conclusions: BLAD is associated with an increased risk of death following lung transplantation, representing an important posttransplant outcome with valuable prognostic significance; however, early allograft specific injury on the molecular level does not increase the risk of BLAD, supporting further mechanistic insight into disease pathophysiology.

12.
Nat Commun ; 15(1): 2749, 2024 Mar 29.
Artículo en Inglés | MEDLINE | ID: mdl-38553461

RESUMEN

Virus-specific T cells (VST) from partially-HLA matched donors have been effective for treatment of refractory viral infections in immunocompromised patients in prior studies with a good safety profile, but rare adverse events have been described. Here we describe a unique and severe adverse event of VST therapy in an infant with severe combined immunodeficiency, who receives, as part of a clinical trial (NCT03475212), third party VSTs for treating cytomegalovirus viremia following bone marrow transplantation. At one-month post-VST infusion, rejection of graft and reversal of chimerism is observed, as is an expansion of T cells exclusively from the VST donor. Single-cell gene expression and T cell receptor profiling demonstrate a narrow repertoire of predominantly activated CD4+ T cells in the recipient at the time of rejection, with the repertoire overlapping more with that of peripheral blood from VST donor than the infused VST product. This case thus demonstrates a rare but serious side effect of VST therapy.


Asunto(s)
Trasplante de Células Madre Hematopoyéticas , Virosis , Lactante , Humanos , Trasplante de Médula Ósea/efectos adversos , Médula Ósea , Inmunoterapia Adoptiva , Linfocitos T/trasplante , Trasplante de Células Madre Hematopoyéticas/efectos adversos
13.
Nat Commun ; 15(1): 3258, 2024 Apr 18.
Artículo en Inglés | MEDLINE | ID: mdl-38637498

RESUMEN

Viral infections remain a major risk in immunocompromised pediatric patients, and virus-specific T cell (VST) therapy has been successful for treatment of refractory viral infections in prior studies. We performed a phase II multicenter study (NCT03475212) for the treatment of pediatric patients with inborn errors of immunity and/or post allogeneic hematopoietic stem cell transplant with refractory viral infections using partially-HLA matched VSTs targeting cytomegalovirus, Epstein-Barr virus, or adenovirus. Primary endpoints were feasibility, safety, and clinical responses (>1 log reduction in viremia at 28 days). Secondary endpoints were reconstitution of antiviral immunity and persistence of the infused VSTs. Suitable VST products were identified for 75 of 77 clinical queries. Clinical responses were achieved in 29 of 47 (62%) of patients post-HSCT including 73% of patients evaluable at 1-month post-infusion, meeting the primary efficacy endpoint (>52%). Secondary graft rejection occurred in one child following VST infusion as described in a companion article. Corticosteroids, graft-versus-host disease, transplant-associated thrombotic microangiopathy, and eculizumab treatment correlated with poor response, while uptrending absolute lymphocyte and CD8 T cell counts correlated with good response. This study highlights key clinical factors that impact response to VSTs and demonstrates the feasibility and efficacy of this therapy in pediatric HSCT.


Asunto(s)
Infecciones por Virus de Epstein-Barr , Trasplante de Células Madre Hematopoyéticas , Virosis , Humanos , Niño , Herpesvirus Humano 4 , Factores de Riesgo , Trasplante de Células Madre Hematopoyéticas/efectos adversos
14.
Blood Adv ; 8(7): 1817-1819, 2024 Apr 09.
Artículo en Inglés | MEDLINE | ID: mdl-38592712

Asunto(s)
Edición Génica
15.
Biota neotrop. (Online, Ed. port.) ; 8(2)Apr.-June 2008. graf, tab
Artículo en Inglés | LILACS | ID: lil-489025

RESUMEN

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...


O principal objetivo deste artigo é apresentar e discutir a melhor forma para estimar a biomassa viva acima do solo (BVS) na Mata Atlântica. A biomassa viva acima do solo em florestas tropicais esta contida principalmente nas árvores. A biomassa das árvores é uma função do seu volume de madeira, obtido do diâmetro e da altura, de sua arquitetura e da densidade de sua madeira (peso seco por unidade de volume fresco). Ela pode ser quantificada pelo método direto (destrutivo) ou pelo método indireto onde a quantificação da biomassa é feita através de modelos matemáticos. Os modelos alométricos podem ser específicos para um determinado local, quando elaborado para um ecossistema particular, ou gerais, que podem ser utilizados em para estimar a biomassa em diferentes locais. Para a Mata Atlântica, a despeito de sua importância, existem somente duas medidas diretas de biomassa de árvores, que resultaram em modelos alométricos específicos para essas florestas. Para selecionar um ou outro modelo alométrico para estimar BVS, disponível na literatura, é necessário levar em conta o a questão a ser respondida e a facilidade com a qual é possível medir as variáveis independentes do modelo. Preferencialmente, deve-se utilizar modelos...


Asunto(s)
Árboles/clasificación , Árboles/efectos adversos , Biomasa , Botánica/clasificación , Flora/análisis , Flora/clasificación , Suelo/análisis
16.
Ciênc. cult. (Säo Paulo) ; 49(1/2): 87-98, jan.-abr. 1997. tab, graf
Artículo en Inglés | LILACS | ID: lil-198301

RESUMEN

Tropical forests of Amazonia play a major role in controlling the composition of the earth's atmosphere. Natural ecosystems of Amazonia contribute significant portions to the global budgets of the greenhouse gases methane and nitrous oxide. Amazon forest vegetation contributes to regional atmospheric chemistry as an important source of reduced gases such as volatile organics and carbon monoxide. The forest soils produce nitric oxide. Recent trends in land use change have led to increases in the sources of nitrous oxide and methane. The ozone precursor nitric oxide is internally recycled under forest conditions while deforestation leads to larger net emissions. We have limited knowledge of biosphere-atmosphere exchange of trace gases in Amazonia. However, recent advances in instrumentation approaches and the evolution in the design of interdisciplinary field campaigns enhance the prospects for successful study of this area in earth system science.


Asunto(s)
Ecosistema Amazónico , Trazadores Radiactivos , Atmósfera/análisis , Contaminantes Ambientales
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA