Effects of post fire ecology on plant species and abundance in Southern Californian Semi-Arid Shrublands

Chaparral strands are considered to be fire- adapted due to diverse recovery mechanisms used by chaparral plant species during secondary succession. The mixture of seeds used in the mulch for the hydroseeded site may be a combination of species native to California but not specific to the CSUSM site. Ultimately the natural emergence of native plants may be affected by hydroseeding, which can result in a decline of native plant diversity. Changes in fire frequency and/or intensity may also occur. Hydroseeding affects initial post- fire recovery of native chaparral vegetation, due to species exclusivity of seed-mixes. It was hypothesized that species diversity and abundance as well as plant cover would be higher in the area treated with hydroseed. 8 individual plots per treatment of unburned and burned, naturally regenerating and hydroseeded, stands at CSUSM. Topsoil (0-10 cm) was collected on February 1, 2019 from 24 randomly located plots (n = 8 plots/site). Woody shrubs (green shrubs) were measured for canopy area and species identification. Identified species included Adenostoma fasiciculatum, Acmispon glaber, Ceanothus tomentosus, Mimulus aurantiacus, Malosma laurina, and Salvia mellifera. The hydroseeded stand had the most diversity among plant species while the unburned stand had the least. Hydroseeded stands have more diversity due to the seed mixture of mulch that was used to initiate restoration on the CSUSM site. There was a significant difference across four major plant species. The mixture of seeds used in the mulch for the hydroseeded site may be a combination of species native to California but not specific to the CSUSM site. Ultimately the natural emergence of native plants may be affected by hydroseeding, which can result in a decline of native plant diversity. Changes in fire frequency and/or intensity may also occur

Temporal and spatial differences of methane flux at arctic tundra in Alaska

High latitude ecosystems were thought to enhance CH_4 emission in relation to the current arctic warming. However, we have little information about this potential feedback mechanisms on climate change, thus, model parameterization is insufficient and the observational data are required. We observed CH_4 flux at several types of tundra in Alaska over the growing seasons since 1995. From these observed data, we examined current CH_4 emission and its controlling factors on Alaskan tundra. Then we discussed about spatial and temporal differences in CH_4 flux. Daily trend of half hourly CH_4 flux had little relation with soil temperature, but the seasonal trend of daily flux changed with soil or water temperature. Cumulative CH_4 fluxes during the growing seasons were 8.1gCH_4m^(-2) on wet sedge tundra at Happy Valley in 1995, 3.3gCH_4m^(-2) on non-acidic moist tundra in 1996, and 3.58-8.24gCH_4m^(-2) on wet sedge tundra at Barrow between 1999-2003. Non-acidic tundra had low CH_4 emission with low CO_2 accumulation. There was large spatial difference in CH_4 flux caused by tundra type, and the large temporal difference at the wet sedge tundra reflected yearly weather variability

Surface albedo and temperature models for surface energy balance fluxes and evapotranspiration using SEBAL and Landsat 8 over Cerrado-Pantanal, Brazil

The determination of the surface energy balance fluxes (SEBFs) and evapotranspiration (ET) is fundamental in environmental studies involving the effects of land use change on the water requirement of crops. SEBFs and ET have been estimated by remote sensing techniques, but with the operation of new sensors, some variables need to be parameterized to improve their accuracy. Thus, the objective of this study is to evaluate the performance of algorithms used to calculate surface albedo and surface temperature on the estimation of SEBFs and ET in the Cerrado-Pantanal transition region of Mato Grosso, Brazil. Surface reflectance images of the Operational Land Imager (OLI) and brightness temperature (Tb) of the Thermal Infrared Sensor (TIRS) of the Landsat 8, and surface reflectance images of the MODIS MOD09A1 product from 2013 to 2016 were combined to estimate SEBF and ET by the surface energy balance algorithm for land (SEBAL), which were validated with measurements from two flux towers. The surface temperature (Ts) was recovered by different models from the Tb and by parameters calculated in the atmospheric correction parameter calculator (ATMCORR). A model of surface albedo (asup) with surface reflectance OLI Landsat 8 developed in this study performed better than the conventional model (acon) SEBFs and ET in the Cerrado-Pantanal transition region estimated with asup combined with Ts and Tb performed better than estimates with acon. Among all the evaluated combinations, SEBAL performed better when combining asup with the model developed in this study and the surface temperature recovered by the Barsi model (Tsbarsi ). This demonstrates the importance of an asup model based on surface reflectance and atmospheric surface temperature correction in estimating SEBFs and ET by SEBAL

MODELLING GROSS PRIMARY PRODUCTION OF TROPICAL FOREST BY REMOTE SENSING

The application of remote sensing has provided an opportunity to improve the estimation of gross primary production (GPP) on a regional scale. Several models to estimate GPP of homogeneous ecosystems, such as agricultural areas, entirely based on remote sensing data exist, but models to describe more heterogeneous areas are less common. Thus, the aim of the study was to evaluate the GPP estimated by different remote sensing methods in an Amazon-Cerrado transition forest in Mato Grosso, using MODIS spectral data. Two models, known as the temperature and greenness model (TG) and the vegetation index (VI) model, were used to estimate seasonal and interannual variations in GPP. Our results indicated that the TG and VI models were incapable of reproducing the seasonal variation in GPP, because the lack of correlation between vegetation indices and the GPP measured from tower-based eddy covariance (GPPEC). Furthermore, the time series of the enhanced vegetation index (EVI) was delayed by 2 months with GPPEC. The results presented in this paper highlight some of the complexities in validating satellite products. Further study over a variety of Brazilian forests is needed to quantitatively assess the TG and VI and other methods to improve their accuracy

Ecological research in the Large Scale Biosphere Atmosphere Experiment in Amazonia: A discussion of early results

The Large-scale Biosphere–Atmosphere Experiment in Amazonia (LBA) is a multinational, interdisciplinary research program led by Brazil. Ecological studies in LBA focus on how tropical forest conversion, regrowth, and selective logging influence carbon storage, nutrient dynamics, trace gas fluxes, and the prospect for sustainable land use in the Amazon region. Early results from ecological studies within LBA emphasize the variability within the vast Amazon region and the profound effects that land-use and land-cover changes are having on that landscape. The predominant land cover of the Amazon region is evergreen forest; nonetheless, LBA studies have observed strong seasonal patterns in gross primary production, ecosystem respiration, and net ecosystem exchange, as well as phenology and tree growth. The seasonal patterns vary spatially and interannually and evidence suggests that these patterns are driven not only by variations in weather but also by innate biological rhythms of the forest species. Rapid rates of deforestation have marked the forests of the Amazon region over the past three decades. Evidence from ground-based surveys and remote sensing show that substantial areas of forest are being degraded by logging activities and through the collapse of forest edges. Because forest edges and logged forests are susceptible to fire, positive feedback cycles of forest degradation may be initiated by land-use-change events. LBA studies indicate that cleared lands in the Amazon, once released from cultivation or pasture usage, regenerate biomass rapidly. However, the pace of biomass accumulation is dependent upon past land use and the depletion of nutrients by unsustainable land-management practices. The challenge for ongoing research within LBA is to integrate the recognition of diverse patterns and processes into general models for prediction of regional ecosystem function

Mecanismos de Controle da Variação Sazonal da Transpiração de uma Floresta de Transição Amazônia Cerrado

No presente trabalho foi estudada a variação sazonal datranspiração, de uma floresta tropical, e sua dependência com fatoresbióticos e abióticos. Utilizaram-se dados do projeto Experimento de GrandeEscala da Biosfera-Atmosfera na Amazônia (LBA), coletados floresta detransição Amazônia-cerrado, norte de Mato Grosso. Os valores máximosda condutividade de superfície (Cs), foram observados no período úmido(0,17 m s-1), e os mínimos (0,011 s m-1) no período de transição úmidoseco.A condutância aerodinâmica (Ca) máxima foi 0,052 m s-1 no períodoúmido e 0,068 m s-1 no período seco. A análise horária do fator dedesacoplamento sugere que a evapotranspiração, durante a manhã, tem ummaior controle realizado pela disponibilidade de energia, quando comparadoao período menos chuvoso. Durante a tarde verifica-se que o dossel dafloresta progressivamente tende a estar mais acoplado à atmosfera, para osperíodos estudados, demonstrando maior controle superficial natranspiração

Índice de Área Foliar em Floresta de Transição Amazonia Cerrado em Diferentes Métodos de Estimativa

The Leaf Area Index (LAI) is a vegetation biophysical variableused for various primary production models across scales and global modelsof climate, hydrology, biogeochemistry and ecology. This paper comparesthree estimates of LAI by at transitional forest Amazon Cerrado. LAI isestimated on field measurements where were utilized light canopytransmittance through the Beer-Lambert equation, remotely sensedModerate Resolution Imaging Spectroradiometer (MODIS) monthly LAIproduct and hemispherical photographs. LAI based on field observationsfor Beer-Lambert equation presented seasonality, obtaining an annual meanvalue of 3.21 to 3.74 m2 m-2 in 2001 to 2003. LAI through MODIS sensorLAI product presented value of 5.25 a 5.54 m2 m-2 in 2001 to 2003. LAIbased on hemispherical photographs presented value of 3.05±0.52 to4.12±0.56 m2 m-2 in Jun/2004 to May/2005 (Silva, 2006). The MODISproduct did not presented significant correlation with others methods. TheMODIS LAI product for transitional forest and tropical forest tropicalcould be important for studies of canopy dynamics and need to be validatedto be used reliable in coupling biosphere atmosphere models.O Índice de Área Foliar (IAF) é uma importante variável biofísicada vegetação usada em vários modelos de produção primária através de escalase modelos globais de clima, hidrologia, biogeoquímica e ecologia. Esseartigo compara três estimativas de IAF na floresta de transição AmazôniaCerrado. O IAF é estimado por observações de campo da transmitância deluz e equação de Lambert-Beer, por sensoriamento remoto utilizando oproduto mensal IAF do sensor remoto Moderate Resolution ImagingSpectroradiometer (MODIS) e por fotografias hemisféricas. O IAF estimadopor Lambert-Beer apresentou sazonalidade e uma média anual variandode 3,21 a 3,74 m2m-2 para os anos de 2001 a 2003. A média de IAFestimada pelo produto MODIS variou de 5,25 a 5,54 m2m-2 para os anos de2001 a 2003. A média de IAF estimada por fotografias hemisféricas varioude 3,05±0,52 a 4,12±0,56 m2m-2 para o período de Jun/2004 a Mai/2005(Silva, 2006). O IAF obtido pelo produto MODIS não apresentou correlaçãosignificativa com o IAF estimado pela lei de Lambert-Beer e por fotografiashemisféricas. O produto IAF do sensor MODIS para floresta detransição e florestas tropicais pode ser importante para estudos de dinâmicade dossel e precisa ser validado para ser utilizado com segurança emmodelos de acoplamento biosfera-atmosfera.Palavras-chave: transmitância da luz no dossel, área foliar, sensoriamentoremoto, floresta tropical

Efeito do microclima no intercâmbio gasoso potencial de cambará (Vochysia divergens Pohl) e lixeira (Curatella americana L.) em área de Cerrado

Leaf gas exchange is affected by micrometeorological conditions, but in many cases and especially for native species, plant acclimation to prior conditions contributes to their physiological performance later. In this sense, the objective of this research was to assess the association between leaf gas exchange and climate variables prevailing at the time of measurement and taken as average values of the previous day, for two plant species Vochysia divergens and Curatella americana representatives of the region and two leaf ages (young and adult), in the case of V. divergens. The work was performed in a pasture in the Cerrado of Mato Grosso, located in Santo Antonio de Leverger 15 km SSE from Cuiabá, for the period between May and December of 2009. Based on the results, it was observed that V. divergens gas exchange rates were affected by both the past environmental conditions and prevailing conditions on the morning of the measurements. Within the ages of leaves of V. divergens, the young leaves showed greater sensitivity to variations in weather conditions as compared to older leaves. In contrast, the gas exchange of C. americana leaves were not significantly correlated with environmental variables. It’s like C. americana respond instantly to changes in microclimate that occur in the environment.O intercâmbio gasoso é afetado pelas condições micrometeorológicas. Porém, em muitos casos, e em especial para espécies nativas, a aclimatação das plantas a condições precedentes contribui para o seu desempenho fisiológico posterior. Neste sentido, o objetivo deste trabalho foi avaliar o efeito do microclima sobre o intercâmbio gasoso das espécies Vochysia divergens e Curatella americana em uma área de Cerrado Mato-Grossense. O trabalho foi relizado no município de Santo Antônio de Leverger, distante 15 km de Cuiabá, no período compreendido de maio a dezembro de 2009. Com base nos resultados, observou-se que as taxas do intercâmbio gasoso de V. divergens foram afetadas tanto pelas condições ambientais passadas quanto pelas prevalecentes na manhã das medições, com a participação significativa de todas as variáveis microclimáticas estudadas apenas para a segunda situação. Folhas jovens de V. divergens demonstraram maior sensibilidade às variações das condições meteorológicas em relação às adultas. Por outro lado, em nenhum momento, as taxas do intercâmbio gasoso de C. americana apresentaram correlação significativa com as variáveis ambientais, como se a espécie fosse sensível às mudanças instantâneas das condições microclimáticas, dentro dos limites empregados neste estudo

Avaliação de dois Métodos para Estimativa do Indice de Área Foliar em Floresta de Transição Amazônia-Cerrado

The estimated leaf area index in Amazonian forest ecosystems has been held, in majority, by methods that include intensity and qualitybalance of electromagnetic radiation transmitted through the canopy. Toincrease the results reliability, it is necessary to test alternatives to estimatethe leaf area index. Thus, the objective of this paper was to test an alternativemethod to Monsi and Saeki (1953), proposed by Charles-Edwards and Lawn(1984).The comparative analyses were performed with data ofphotosynthetic active radiation obtained from a micrometeorological towerinstalled in a transitional area of the Amazonian forest to Savannah in 2003.The method proposed by Charles-Edwards and Lawn (1984) supplies valuesof the fraction of radiation intercepted significantly different from the Monsiand Saeki (1953) method. Although it has not been observed any significantdifference between the leaf area index calculated by both methods, thealternative method presented limitations to be used in forest ecosystems.Therefore, further studies in different forest ecosystems are needed toconfirm the use of both methods.Considerando a necessidade de se obter um método simples e eficiente na determinação da variabilidade espacial do índice de área foliar em ecossistemas florestais, o presente trabalho teve como objetivo testar um método alternativo ao de Monsi e Saeki (1953), proposto por Charles-Edwards e Lawn (1984). As análises comparativas foram realizadas a partir de dados de radiação fotossinteticamente ativa obtidos durante o ano de 2003 em uma torre micrometeorológica instalada em uma área de Floresta de transição Amazônia-Cerrado. O método proposto por Charles-Edwards e Lawn (1984) fornece valores da fração de radiação interceptada significativamente diferentes do método de Monsi e Saeki (1953) e, apesar de não verificada qualquer diferença significativa entre o índice de área foliar calculado por ambos os métodos, a variabilidade de resposta obtida permite inferir que esse método alternativo apresenta limitações para seu emprego em ecossistemas florestais

Trocas Gasosas de uma Espécie Lenhosa na Floresta de Transição Amazônia - Cerrado

As florestas de transição parecem ter um balanço de CO2 nulo, porém as mudanças climáticas que têm ocorrido, como a seca prolongada, podem alterar esse equilíbrio a longo prazo. Desta forma, o presente trabalho teve como objetivo estudar as variáveis fisiológicas: fotossíntese, fotorrespiração e respiração, e entender como essas variáveis podem ser afetadas pelas variações sazonais e a posição da folha na copa da árvore de uma espécie vegetal característica de floresta de transição Amazônia-Cerrado, a Brosimum lactescens S Moore (Moraceae). Utilizando-se um sistema portátil LI-6400 (LI-COR, Inc., Lincoln, NE, USA), as medidas foram realizadas mensalmente. Verificou-se que na estação seca, houve um incremento substancial na densidade de fluxo fotossinteticamente ativo, DFFA, elevando o déficit de pressão de vapor (DPV). Visando reduzir as perdas de água, a planta tende a promover o fechamento dos estômatos, havendo uma diminuição da condutância estomática (gs), reduzindo assim também a concentração de carbono interno (Ci). Como conseqüência, verificou-se que a fotossíntese comportou-se de maneira descendente. Contudo. Nesse contexto, como estratégia para dissipação de energia em excesso, a fotorrespiração (Rp) aumentou e de forma análoga a respiração (Rd) também aumentou. Os resultados encontrados neste estudo sugerem que variações na distribuição da precipitação alteram significativamente as trocas gasosas da espécie estudada