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1.
Sci Total Environ ; 894: 164995, 2023 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-37343878

RESUMO

Coastal wetlands provide critical ecosystem services but are experiencing disruptions caused by inundation and saltwater intrusion under intensified climate change, sea-level rise, and anthropogenic activities. Recent studies have shown that these disturbances downgraded coastal wetlands mainly through affecting their hydrological processes. However, research on what is the most critical driver for wetland downgrading and how it affects coastal wetlands is still in its infancy. This study examined drivers of three types of wetland downgrading, including woody wetland loss, emergent herbaceous wetland loss, and woody wetlands converting to emergent herbaceous wetlands. By using random forest classification models for the wetland ecosystems in the Alligator River National Wildlife Refuge, North Carolina, USA, during 1995-2019, we determined the relative importance of different hydrogeomorphic processes and the dominant variables in driving the wetland downgrading. Results showed that random forest classification models were accurate (> 97 % overall accuracy) in classifying wetland downgrading. Multiple hydrogeomorphic variables collectively contributed to the coastal wetland downgrading. However, the dominant control factors varied across different types of wetland downgrading. Woody wetlands were most susceptible to saltwater intrusion and were likely to downgrade if the saltwater table was shallower than 0.2 m below the land surface. In contrast, emergent herbaceous wetlands were most vulnerable to inundation and drought. The favorable groundwater table for emergent herbaceous wetlands was between 0.34 m above the land surface and 0.32 m below the land surface, beyond which the emergent herbaceous wetland tended to disappear. For downgraded woody wetlands, their distance to canals/ditches played a crucial role in determining their fates after downgrading. The machine learning approach employed in this study provided critical knowledge about the thresholds of hydrogeomorphic variables for the downgrading of different types of coastal wetlands. Such information can help guide effective and targeted coastal wetland conservation, management, and restoration measures.

2.
Ecol Appl ; 32(7): e2655, 2022 10.
Artigo em Inglês | MEDLINE | ID: mdl-35567435

RESUMO

Carbon (C) allocation and nonstructural carbon (NSC) dynamics play essential roles in plant growth and survival under stress and disturbance. However, quantitative understanding of these processes remains limited. Here we propose a framework where we connect commonly measured carbon cycle components (eddy covariance fluxes of canopy CO2 exchange, soil CO2 efflux, and allometry-based biomass and net primary production) by a simple mass balance model to derive ecosystem-level NSC dynamics (NSCi ), C translocation (dCi ), and the biomass production efficiency (BPEi ) in above- and belowground plant (i = agp and bgp) compartments. We applied this framework to two long-term monitored loblolly pine (Pinus taeda) plantations of different ages in North Carolina and characterized the variations of NSC and allocation in years under normal and drought conditions. The results indicated that the young stand did not have net NSC flux at the annual scale, whereas the mature stand stored a near-constant proportion of new assimilates as NSC every year under normal conditions, which was comparable in magnitude to new structural growth. Roots consumed NSC in drought and stored a significant amount of NSC post drought. The above- and belowground dCi and BPEi varied more from year to year in the young stand and approached a relatively stable pattern in the mature stand. The belowground BPEbgp differed the most between the young and mature stands and was most responsive to drought. With the internal C dynamics quantified, this framework may also improve biomass production estimation, which reveals the variations resulting from droughts. Overall, these quantified ecosystem-scale dynamics were consistent with existing evidence from tree-based manipulative experiments and measurements and demonstrated that combining the continuous fluxes as proposed here can provide additional information about plant internal C dynamics. Given that it is based on broadly available flux data, the proposed framework is promising to improve the allocation algorithms in ecosystem C cycle models and offers new insights into observed variability in soil-plant-climate interactions.


Assuntos
Carbono , Ecossistema , Ciclo do Carbono , Dióxido de Carbono , Pinus taeda , Solo/química
3.
Sci Total Environ ; 834: 155154, 2022 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-35413347

RESUMO

Urban spring phenology changes governed by multiple biological and environmental factors significantly impact urban ecosystem functions and services. However, the temporal changes in spring phenology (i.e., the start of the vegetation growing season, SOS) and the magnitude of SOS sensitivity to temperature in urban settings are not well understood compared with natural ecosystems. Therefore, we explored warming impacts on SOS across 292 rural and urban areas from 2001 to 2016. We found that warming occurred in 79.9% of urban areas and 61.3% of rural areas. This warming advanced SOS in 78.3% of the urban settings and 72.8% of the rural areas. The accelerated rate of SOS in urban settings was significantly higher (-0.52 ± 0.86 days/year) than in rural areas (-0.09 ± 0.69 days/year). Moreover, SOS was significantly more sensitive to warming in urban areas (-2.86 ± 3.57 days/°C) than in rural areas (-1.57 ± 3.09 days/°C), driven by urban-rural differences in climatic (precipitation, temperature, and warming speed) and vegetation factors. Precipitation contributed the most had the highest relative importance for controlling SOS, at 45% and 63% for urban and rural areas, respectively. These findings provide a new understanding of the impacts of urbanization and climate change on vegetation phenology. Moreover, our results have implications for urban environment impacts on ecosystems and human health.


Assuntos
Ecossistema , Desenvolvimento Vegetal , China , Cidades , Mudança Climática , Humanos , Estações do Ano , Temperatura
4.
Tree Physiol ; 42(1): 44-58, 2022 01 05.
Artigo em Inglês | MEDLINE | ID: mdl-34617120

RESUMO

Considering the temporal responses of carbon isotope discrimination (Δ13C) to local water availability in the spatial analysis of Δ13C is essential for evaluating the contribution of environmental and genetic facets of plant Δ13C. Using tree-ring Δ13C from years with contrasting water availability at 76 locations across the natural range of loblolly pine, we decomposed site-level Δ13C signals to maximum Δ13C in well-watered conditions (Δ13Cmax) and isotopic drought sensitivity (m) as a change in Δ13C per unit change of Palmer's Drought Severity Index (PDSI). Site water status, especially the tree lifetime average PDSI, was the primary factor affecting Δ13Cmax. The strong spatial correlation exhibited by m was related to both genetic and environmental factors. The long-term average water availability during the period relevant to trees as indicated by lifetime average PDSI correlated with Δ13Cmax, suggesting acclimation in tree gas-exchange traits, independent of incident water availability. The positive correlation between lifetime average PDSI and m indicated that loblolly pines were more sensitive to drought at mesic than xeric sites. The m was found to relate to a plant's stomatal control and may be employed as a genetic indicator of efficient water use strategies. Partitioning Δ13C to Δ13Cmax and m provided a new angle for understanding sources of variation in plant Δ13C, with several fundamental and applied implications.


Assuntos
Pinus taeda , Árvores , Isótopos de Carbono/análise , Secas , Árvores/fisiologia , Água/fisiologia
6.
Glob Chang Biol ; 26(12): 7268-7283, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33026137

RESUMO

Globally, soils store two to three times as much carbon as currently resides in the atmosphere, and it is critical to understand how soil greenhouse gas (GHG) emissions and uptake will respond to ongoing climate change. In particular, the soil-to-atmosphere CO2 flux, commonly though imprecisely termed soil respiration (RS ), is one of the largest carbon fluxes in the Earth system. An increasing number of high-frequency RS measurements (typically, from an automated system with hourly sampling) have been made over the last two decades; an increasing number of methane measurements are being made with such systems as well. Such high frequency data are an invaluable resource for understanding GHG fluxes, but lack a central database or repository. Here we describe the lightweight, open-source COSORE (COntinuous SOil REspiration) database and software, that focuses on automated, continuous and long-term GHG flux datasets, and is intended to serve as a community resource for earth sciences, climate change syntheses and model evaluation. Contributed datasets are mapped to a single, consistent standard, with metadata on contributors, geographic location, measurement conditions and ancillary data. The design emphasizes the importance of reproducibility, scientific transparency and open access to data. While being oriented towards continuously measured RS , the database design accommodates other soil-atmosphere measurements (e.g. ecosystem respiration, chamber-measured net ecosystem exchange, methane fluxes) as well as experimental treatments (heterotrophic only, etc.). We give brief examples of the types of analyses possible using this new community resource and describe its accompanying R software package.


Assuntos
Gases de Efeito Estufa , Atmosfera , Dióxido de Carbono/análise , Ecossistema , Gases de Efeito Estufa/análise , Metano/análise , Óxido Nitroso/análise , Reprodutibilidade dos Testes , Respiração , Solo
7.
Tree Physiol ; 39(12): 1984-1994, 2019 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-31748787

RESUMO

Drought frequency and intensity are projected to increase throughout the southeastern USA, the natural range of loblolly pine (Pinus taeda L.), and are expected to have major ecological and economic implications. We analyzed the carbon and oxygen isotopic compositions in tree ring cellulose of loblolly pine in a factorial drought (~30% throughfall reduction) and fertilization experiment, supplemented with trunk sap flow, allometry and microclimate data. We then simulated leaf temperature and applied a multi-dimensional sensitivity analysis to interpret the changes in the oxygen isotope data. This analysis found that the observed changes in tree ring cellulose could only be accounted for by inferring a change in the isotopic composition of the source water, indicating that the drought treatment increased the uptake of stored moisture from earlier precipitation events. The drought treatment also increased intrinsic water-use efficiency, but had no effect on growth, indicating that photosynthesis remained relatively unaffected despite 19% decrease in canopy conductance. In contrast, fertilization increased growth, but had no effect on the isotopic composition of tree ring cellulose, indicating that the fertilizer gains in biomass were attributable to greater leaf area and not to changes in leaf-level gas exchange. The multi-dimensional sensitivity analysis explored model behavior under different scenarios, highlighting the importance of explicit consideration of leaf temperature in the oxygen isotope discrimination (Δ18Oc) simulation and is expected to expand the inference space of the Δ18Oc models for plant ecophysiological studies.


Assuntos
Pinus taeda , Pinus , Secas , Isótopos de Oxigênio , Fotossíntese , Folhas de Planta , Árvores
8.
Tree Physiol ; 37(1): 142-150, 2017 01 31.
Artigo em Inglês | MEDLINE | ID: mdl-28173589

RESUMO

Stable isotope ratios (δ13C and δ18O) of tree-ring α-cellulose are important tools in paleoclimatology, ecology, plant physiology and genetics. The Multiple Sample Isolation System for Solids (MSISS) was a major advance in the tree-ring α-cellulose extraction methods, offering greater throughput and reduced labor input compared to traditional alternatives. However, the usability of the method for resinous conifer species may be limited by the need to remove extractives from some conifer species in a separate pretreatment step. Here we test the necessity of pretreatment for α-cellulose extraction in loblolly pine (Pinus taeda L.), and the efficiency of a modified acetone-based ambient-temperature step for the removal of extractives (i) in loblolly pine from five geographic locations representing its natural range in the southeastern USA, and (ii) on five other common coniferous species (black spruce (Picea mariana Mill.), Fraser fir (Abies fraseri (Pursh) Poir.), Douglas fir (Pseudotsuga menziesii (Mirb.) Franco), Norway spruce (Picea abies (L.) Karst) and ponderosa pine (Pinus ponderosa D.)) with contrasting extractive profiles. The differences of δ13C values between the new and traditional pretreatment methods were within the precision of the isotope ratio mass spectrometry method used (±0.2‰), and the differences between δ18O values were not statistically significant. Although some unanticipated results were observed in Fraser fir, the new ambient-temperature technique was deemed as effective as the more labor-consuming and toxic traditional pretreatment protocol. The proposed technique requires a separate acetone-inert multiport system similar to MSISS, and the execution of both pretreatment and main extraction steps allows for simultaneous treatment of up to several hundred microsamples from resinous softwood, while the need of additional labor input remains minimal.


Assuntos
Acetona/química , Isótopos de Carbono/análise , Celulose/análise , Ensaios de Triagem em Larga Escala/métodos , Isótopos de Oxigênio/análise , Traqueófitas/química , Caules de Planta/química , Madeira/química
9.
Tree Physiol ; 32(6): 707-23, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22467712

RESUMO

Deep root water uptake and hydraulic redistribution (HR) have been shown to play a major role in forest ecosystems during drought, but little is known about the impact of climate change, fertilization and soil characteristics on HR and its consequences on water and carbon fluxes. Using data from three mid-rotation loblolly pine plantations, and simulations with the process-based model MuSICA, this study indicated that HR can mitigate the effects of soil drying and had important implications for carbon uptake potential and net ecosystem exchange (NEE), especially when N fertilization is considered. At the coastal site (C), characterized by deep organic soil, HR increased dry season tree transpiration (T) by up to 40%, and such an increase affected NEE through major changes in gross primary productivity (GPP). Deep-rooted trees did not necessarily translate into a large volume of HR unless soil texture allowed large water potential gradients to occur, as was the case at the sandy site (S). At the Piedmont site (P) characterized by a shallow clay-loam soil, HR was low but not negligible, representing up to 10% of T. In the absence of HR, it was predicted that at the C, S and P sites, annual GPP would have been diminished by 19, 7 and 9%, respectively. Under future climate conditions HR was predicted to be reduced by up to 25% at the C site, reducing the resilience of trees to precipitation deficits. The effect of HR on T and GPP was predicted to diminish under future conditions by 12 and 6% at the C and P sites, respectively. Under future conditions, T was predicted to stay the same at the P site, but to be marginally reduced at the C site and slightly increased at the S site. Future conditions and N fertilization would decrease T by 25% at the C site, by 15% at the P site and by 8% at the S site. At the C and S sites, GPP was estimated to increase by 18% and by >70% under future conditions, respectively, with little effect of N fertilization. At the P site, future conditions would stimulate GPP by only 12%, but future conditions plus N fertilization would increase GPP by 24%. As a consequence, in all sites, water use efficiency was predicted to improve dramatically with future conditions. Modeling the effect of reduced annual precipitation indicated that limited water availability would decrease all carbon fluxes, including NEE and respiration. Our simulations highlight the interactive effects of nutrients and elevated CO(2), and showed that the effect of N fertilization would be greater under future climate conditions.


Assuntos
Mudança Climática , Pinus taeda/fisiologia , Raízes de Plantas/fisiologia , Transpiração Vegetal , Água/fisiologia , Carbono/metabolismo , Dióxido de Carbono/fisiologia , Fertilizantes , Modelos Biológicos , North Carolina , Chuva , Estresse Fisiológico , Temperatura , Árvores/fisiologia
10.
Glob Chang Biol ; 18(10): 3186-3201, 2012 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-28741818

RESUMO

Timber harvests remove a significant portion of ecosystem carbon. While some of the wood products moved off-site may last past the harvest cycle of the particular forest crop, the effect of the episodic disturbances on long-term on-site carbon sequestration is unclear. The current study presents a 25 year carbon budget estimate for a typical commercial loblolly pine plantation in North Carolina, USA, spanning the entire rotation cycle. We use a chronosequence approach, based on 5 years of data from two adjacent loblolly pine plantations. We found that while the ecosystem is very productive (GEP up to 2900 g m-2  yr-1 , NEE at maturity about 900 g C m-2  yr-1 ), the production of detritus does not offset the loss of soil C through heterotrophic respiration (RH ) on an annual basis. The input of dead roots at harvest may offset the losses, but there remain significant uncertainties about both the size and decomposition dynamics of this pool. The pulse of detritus produced at harvest resulted in a more than 60% increase in RH . Contrary to expectations, the peak of RH in relation to soil respiration (SR) did not occur immediately after the harvest disturbance, but in years 3 and 4, suggesting that a pool of roots may have remained alive for the first few years. On the other hand, the pulse of aboveground RH from coarse woody debris lasted only 2 years. The postharvest increase in RH was offset by a decrease in autotrophic respiration such that the total ecosystem respiration changed little. The observed flux rates show that even though the soil C pool may not necessarily decrease in the long-term, old soil C is definitely an active component in the site C cycle, contributing about 25-30% of the RH over the rotation cycle.

11.
Ambio ; 40(7): 828-31, 2011 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-22338721

RESUMO

China leads the world in afforestation, and is one of the few countries whose forested area is increasing. However, this massive "greening" effort has been less effective than expected; afforestation has sometimes produced unintended environmental, ecological, and socioeconomic consequences, and has failed to achieve the desired ecological benefits. Where afforestation has succeeded, the approach was tailored to local environmental conditions. Using the right plant species or species composition for the site and considering alternatives such as grassland restoration have been important success factors. To expand this success, government policy should shift from a forest-based approach to a results-based approach. In addition, long-term monitoring must be implemented to provide the data needed to develop a cost-effective, scientifically informed restoration policy.


Assuntos
Conservação dos Recursos Naturais , China , Ecologia
12.
Circulation ; 120(22): 2170-6, 2009 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-19917887

RESUMO

BACKGROUND: The Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) demonstrated that implantable cardioverter-defibrillator (ICD) therapy reduces all-cause mortality in patients with New York Heart Association class II/III heart failure and a left ventricular ejection fraction < or =35% on optimal medical therapy. Whether ICD therapy reduced sudden death caused by ventricular tachyarrhythmias without affecting heart failure deaths in this population is unknown. METHODS AND RESULTS: SCD-HeFT randomized 2521 subjects to placebo, amiodarone, or shock-only, single-lead ICD therapy. Over a median follow-up of 45.5 months, a total of 666 deaths occurred, which were reviewed by an Events Committee and initially categorized as cardiac or noncardiac. Cardiac deaths were further adjudicated as resulting from sudden death presumed to be ventricular tachyarrhythmic, bradyarrhythmia, heart failure, or other cardiac causes. ICD therapy significantly reduced cardiac mortality compared with placebo (adjusted hazard ratio, 0.76; 95% confidence interval, 0.60 to 0.95) and tachyarrhythmia mortality (adjusted hazard ratio, 0.40; 95% confidence interval, 0.27 to 0.59) and had no impact on mortality resulting from heart failure or noncardiac causes. The cardiac and tachyarrhythmia mortality reductions were evident in subjects with New York Heart Association class II but not in subjects with class III heart failure. The reduction in tachyarrhythmia mortality with ICD therapy was similar in subjects with ischemic and nonischemic disease. Compared with placebo, amiodarone had no significant effect on any mode of death. CONCLUSIONS: ICD therapy reduced cardiac mortality and sudden death presumed to be ventricular tachyarrhythmic in SCD-HeFT and had no effect on heart failure mortality. Amiodarone had no effect on all-cause mortality or its cause-specific components, except an increase in non-cardiac mortality in class III patients. [corrected] CLINICAL TRIAL REGISTRATION INFORMATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00000609.


Assuntos
Amiodarona/uso terapêutico , Antiarrítmicos/uso terapêutico , Morte Súbita Cardíaca/prevenção & controle , Desfibriladores Implantáveis , Insuficiência Cardíaca/tratamento farmacológico , Taquicardia/tratamento farmacológico , Causas de Morte , Terapia Combinada , Morte Súbita Cardíaca/epidemiologia , Seguimentos , Insuficiência Cardíaca/mortalidade , Humanos , Estimativa de Kaplan-Meier , Placebos , Modelos de Riscos Proporcionais , Fatores de Risco , Taquicardia/mortalidade
13.
J Environ Manage ; 90(8): 2762-70, 2009 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-19375215

RESUMO

Poplar plantation is the most dominant broadleaf forest type in northern China. Since the mid-1990s plantation was intensified to combat desertification along China's northwestern border, i.e., within Inner Mongolia (IM). This evoked much concern regarding the ecological and environmental effects on areas that naturally grow grass or shrub vegetation. To highlight potential consequences of large-scale poplar plantations on the water budget within semiarid IM, we compared the growing season water balance (evapotranspiration (ET) and precipitation (PPT)) of a 3-yr old poplar plantation (Kp(3)) and a natural shrubland (Ks) in the Kubuqi Desert in western IM, and a 6-yr old poplar plantation (Bp(6)) growing under sub-humid climate near Beijing. The results showed that, despite 33% lower PPT at Kp(3), ET was 2% higher at Kp(3) (228 mm) as compared with Ks (223 mm) in May-September 2006. The difference derived mainly from higher ET at the plantation during drier periods of the growing season, which also indicated that the poplars must have partly transpired groundwater. Estimated growing season ET at Bp(6) was about 550 mm and more than 100% higher than at Kp(3). It is estimated that increases in leaf area index and net radiation at Kp(3) provide future potential for the poplars in Kubuqi to exceed the present ET and ET of the natural shrubland by 100-200%. These increases in ET are only possible through the permanent use of groundwater either directly by the trees or through increased irrigation. This may significantly change the water balance in the area (e.g., high ET at the cost of a reduction in the water table), which renders large-scale plantations a questionable tool in sustainable arid-land management.


Assuntos
Clima , Ecossistema , Populus/metabolismo , Movimentos da Água , China , Transpiração Vegetal/fisiologia
14.
Int J Biometeorol ; 53(2): 127-34, 2009 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-19037664

RESUMO

The contribution of the organic (O) horizon to total soil respiration is poorly understood even though it can represent a large source of uncertainty due to seasonal changes in microclimate and O horizon properties due to plant phenology. Our objectives were to partition the CO(2) effluxes of litter layer and mineral soil from total soil respiration (SR) and determine the relative importance of changing temperature and moisture mediating the fluxes. We measured respiration in an oak-dominated forest with or without the O horizon for 1 year within the Oak Openings Region of northwest Ohio. Mineral soil and O horizon respiration were subtracted from mineral soil respiration (MSR) to estimate litter respiration (LR). Measurements were grouped by oak phenology to correlate changes in plant activity with respiration. The presence of the O horizon represented a large source of seasonal variation in SR. The timing of oak phenology explained some of the large changes in both SR and LR, and their relationship with temperature and moisture. The contribution to SR of respiration from the mineral soil was greatest during pre-growth and pre-dormancy, as evident by the low LR:MSR ratios of 0.65 +/- 0.10 (mean +/- SE) and 0.69 +/- 0.03, respectively, as compared to the other phenophases. Including moisture increased our ability to predict MSR and SR during the growth phenophase and LR for every phenophase. Temperature and moisture explained 85% of the variation in MSR, but only 60% of the variation in LR. The annual contribution of O horizon to SR was 48% and the ratio of litter to soil respiration was tightly coupled over a wide range of environmental conditions. Our results suggest the presence of the O horizon is a major mediator of SR.


Assuntos
Quercus/metabolismo , Solo/análise , Carbono/metabolismo , Dióxido de Carbono/metabolismo , Ecossistema , Conceitos Meteorológicos , Modelos Biológicos , Ohio , Folhas de Planta/metabolismo , Quercus/crescimento & desenvolvimento , Árvores/metabolismo
15.
New Phytol ; 179(3): 818-828, 2008.
Artigo em Inglês | MEDLINE | ID: mdl-18537894

RESUMO

* Climate change projections predict an intensifying hydrologic cycle and an increasing frequency of droughts, yet quantitative understanding of the effects on ecosystem carbon exchange remains limited. * Here, the effect of contrasting precipitation and soil moisture dynamics were evaluated on forest carbon exchange using 2 yr of eddy covariance and microclimate data from a 50-yr-old mixed oak woodland in northern Ohio, USA. * The stand accumulated 40% less carbon in a year with drought between bud-break and full leaf expansion (354 +/- 81 g C m(-2) yr(-1) in 2004 and 252 +/- 45 g C m(-2) yr(-1) in 2005). This was caused by greater suppression of gross ecosystem productivity (GEP; 16% = 200 g) than of ecosystem respiration (ER; 11% = 100 g) by drought. Suppressed GEP was traced to lower leaf area, lower apparent quantum yield and lower canopy conductance. The moisture sensitivity of ER may have been mediated by GEP. * The results highlight the vulnerability of the ecosystem to even a moderate drought, when it affects a critical aspect of development. Although the drought was preceded by rain, the storage capacity of the soil seemed limited to 1-2 wk, and therefore droughts longer than this are likely to impair productivity in the region.


Assuntos
Acer/metabolismo , Carbono/metabolismo , Quercus/metabolismo , Árvores/metabolismo , Água/metabolismo , Acer/crescimento & desenvolvimento , Ecossistema , Quercus/crescimento & desenvolvimento , Chuva , Estações do Ano , Solo , Temperatura , Árvores/crescimento & desenvolvimento
16.
J Am Acad Child Adolesc Psychiatry ; 45(12): 1412-8, 2006 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-17135986

RESUMO

OBJECTIVE: To examine the time to response for both pharmacotherapy and psychotherapy in the Treatment for Adolescents with Depression Study (TADS). METHOD: Adolescents (N = 439, ages 12 to 17 years) with major depressive disorder were randomized to fluoxetine (FLX), cognitive-behavioral therapy (CBT), their combination (COMB), or pill placebo (PBO). Defining response as very much improved or much improved on the Clinical Global Impression-Improvement Scale (CGI-I), survival analyses using Cox proportional hazards models, and Kaplan-Meier curves were conducted to evaluate time to first response and time to stable response for subjects receiving pharmacotherapy (COMB, FLX, PBO) as well as for subjects receiving CBT (COMB, CBT). Direct comparisons between pharmacotherapy and CBT were not made because of differences in visit schedules. RESULTS: Based on pharmacotherapist CGI-I scores, COMB and FLX showed faster onset of benefit than PBO on time to response and time to stable response (p < .001), and COMB was faster than FLX on time to stable response (p = .034). The probability of sustained early response was approximately threefold greater for COMB than PBO, twofold greater for FLX than PBO, and 1.5-fold greater for COMB than FLX. On the psychotherapist CGI-I scores, both first response and stable response occurred faster in COMB than CBT (p < .001), with a probability of sustained early response approximately threefold greater for COMB than CBT. CONCLUSIONS: In the acute treatment of depressed adolescents, FLX and COMB accelerate response relative to PBO, and COMB accelerates response relative to CBT alone.


Assuntos
Terapia Cognitivo-Comportamental/métodos , Transtorno Depressivo Maior/terapia , Fluoxetina/uso terapêutico , Inibidores Seletivos de Recaptação de Serotonina/uso terapêutico , Adolescente , Criança , Terapia Combinada , Transtorno Depressivo Maior/diagnóstico , Transtorno Depressivo Maior/tratamento farmacológico , Feminino , Humanos , Masculino , Inquéritos e Questionários , Fatores de Tempo
17.
Int J Biometeorol ; 51(2): 135-44, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-16874506

RESUMO

Soil respiration (SR) represents a major component of forest ecosystem respiration and is influenced seasonally by environmental factors such as temperature, soil moisture, root respiration, and litter fall. Changes in these environmental factors correspond with shifts in plant phenology. In this study, we examined the relationship between canopy phenophases (pre-growth, growth, pre-dormancy, and dormancy) and SR sensitivity to changes in soil temperature (T(S)). SR was measured 53 times over 550 days within an oak forest in northwest Ohio, USA. Annual estimates of SR were calculated with a Q(10) model based on T(S) on a phenological (PT), or annual timescale (AT), or T(S) and soil volumetric water content (VWC) on a phenological (PTM) or annual (ATM) timescale. We found significant (p<0.01) difference in apparent Q(10) from year 2004 (1.23) and year 2005 (2.76) during the growth phenophase. Accounting for moisture-sensitivity increased model performance compared to temperature-only models: the error was -17% for the ATM model and -6% for the PTM model. The annual models consistently underestimated SR in summer and overestimated it in winter. These biases were reduced by delineating SR by tree phenophases and accounting for variation in soil moisture. Even though the bias of annual models in winter SR was small in absolute scale, the relative error was about 91%, and may thus have significant implications for regional and continental C balance estimates.


Assuntos
Quercus/crescimento & desenvolvimento , Solo/análise , Modelos Teóricos , Ohio , Estações do Ano , Temperatura , Árvores , Água/análise
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