Detection of Mortality in Tropical Forests Using Remote Sensing: From Treefall Gaps to Large Disturbances

The frequency, severity, and intensity of natural disturbances in tropical forests continually re-shape forest structure. At small scale, branch or tree-falls gaps and subsequent recovery are important mechanisms for carbon cycling. At landscape scale, large disturbances (blow-downs) may also play a role on the structure and composition of tropical forests. Quantitative studies of natural disturbances across the occurrence spectrum (branch fall-gaps to blow-downs) are rare for the Amazon. Remote sensing coupled with intense field work data collection provides the means to analyze the dynamic of tropical forests at multiple scales. In this dissertation three aspects of natural disturbances were examined: (1) formation and detection of small scale disturbances investigated in the field and with high resolution remote sensing; (2) mapping and spatial analysis of large disturbances (blow-downs) caused by convective cloud drafts; and (3) a quantitative characterization of the large spectrum of natural disturbances in tropical ecosystems. For small scale disturbances, two large plots of 114 and 53 ha were established and surveyed in unmanaged tropical forest of the Amazon. Data of gap area, canopy openness (CO), leaf area index (LAI), coarse woody debris (CWD) and tree mortality were collected in both plots. The relation between CO and LAI of gaps coupled with high resolution satellite images IKONOS-2 was investigated using geostatistics. Based on field plot measurements, tree-fall gaps account only about 30% of the flux of annual tree mortality. Most mortality does not result in gap formation. On average, gap formation accounted for a minor proportion of the stocks (about 5% of the total fallen CWD) and fluxes (about 23%) of CWD carbon. There was no significant correlation between remote sensing products and variables of CO and LAI in both large plots, probably due to high shadow fraction in high-resolution images. For large scale disturbances, a spatial pattern analysis of blow-downs apparently caused by severe storms was discovered using 27 Landsat images and daily precipitation from NOAA satellite data. In this image mosaic from 1999 to 2000, there are 279 patches (from 5 ha to 2,223 ha) characteristic of blow-downs. A total of 21,931 ha of forest were disturbed. There was a strong correlation between occurrence of blow-downs and frequency of heavy rainfall (Spearman\u27s rank, r2=0.84, p\u3c0.0003). We provided the first spectrum analysis of disturbances, at several scales of severity by combining data collected for this dissertation with previously published information from a variety of sources: (1) Large plot surveys; (2) mapped blow-downs; (3) RAINFOR permanent plots; (4) historical blow-downs ≥ 30 ha; and (5) the published mean above-ground biomass map of the Amazon. We found two disjointed disturbance regimes---small-scale tree-fall gaps and larger-scale blow-down disturbances---suggesting that there may be other missed disturbance mechanisms in the Amazon may also play a role in the dynamics of tropical forest ecosystems

Storm intensity and old-growth forest disturbances in the Amazon region

We analyzed the pattern of large forest disturbances or blow-downs apparently caused by severe storms in a mostly unmanaged portion of the Brazilian Amazon using 27 Landsat images and daily precipitation estimates from NOAA satellite data. For each Landsat a spectral mixture analysis (SMA) was applied. Based on SMA, we detected and mapped 279 patches (from 5 ha to 2,223 ha) characteristic of blow-downs. A total of 21,931 ha of forest were disturbed. We found a strong correlation between occurrence of blow-downs and frequency of heavy rainfall (Spearman\u27s rank, r2 = 0.84, p \u3c 0.0003). The recurrence intervals of large disturbances were estimated to be 90,000 yr for the eastern Amazon and 27,000 yr for the western Amazon. This suggests that weather patterns affect the frequency of large forest disturbances that may produce different rates of forest turnover in the eastern and western Amazon basin

Old-growth forest loss and secondary forest recovery across Amazonian countries

There is growing recognition of the potential of large-scale forest restoration in the Amazon as a 'nature-based solution' to climate change. However, our knowledge of forest loss and recovery beyond Brazil is limited, and carbon emissions and accumulation have not been estimated for the whole biome. Combining a 33 year land cover dataset with estimates of above-ground biomass and carbon sequestration rates, we evaluate forest loss and recovery across nine Amazonian countries and at a local scale. We also estimate the role of secondary forests in offsetting old-growth deforestation emissions and explore the temporal trends in forest loss and recovery. We find secondary forests across the biome to have offset just 9.7% of carbon emissions from old-growth deforestation, despite occupying 28.8% of deforested land. However, these numbers varied between countries ranging from 9.0% in Brazil to 23.8% in Guyana for carbon offsetting, and 24.8% in Brazil to 56.9% in Ecuador for forest area recovery. We reveal a strong, negative spatial relationship between old-growth forest loss and recovery by secondary forests, showing that regions with the greatest potential for large-scale restoration are also those that currently have the lowest recovery (e.g. Brazil dominates deforestation and emissions but has the lowest recovery). In addition, a temporal analysis of the regions that were >80% deforested in 1997 shows a continued decline in overall forest cover. Our findings identify three important challenges: (a) incentivising large-scale restoration in highly deforested regions, (b) protecting secondary forests without disadvantaging landowners who depend on farm-fallow systems, and (c) preventing further deforestation. Combatting all these successfully is essential to ensuring that the Amazon biome achieves its potential in mitigating anthropogenic climate change

Secondary forests offset less than 10% of deforestation-mediated carbon emissions in the Brazilian Amazon

Secondary forests are increasing in the Brazilian Amazon and have been cited as an important mechanism for reducing net carbon emissions. However, our understanding of the contribution of secondary forests to the Amazonian carbon balance is incomplete, and it is unclear to what extent emissions from old‐growth deforestation have been offset by secondary forest growth. Using MapBiomas 3.1 and recently refined IPCC carbon sequestration estimates, we mapped the age and extent of secondary forests in the Brazilian Amazon and estimated their role in offsetting old‐growth deforestation emissions since 1985. We also assessed whether secondary forests in the Brazilian Amazon are growing in conditions favourable for carbon accumulation in relation to a suite of climatic, landscape and local factors. In 2017, the 129,361 km2 of secondary forest in the Brazilian Amazon stored 0.33 ± 0.05 billion Mg of above‐ground carbon but had offset just 9.37% of old‐growth emissions since 1985. However, we find that the majority of Brazilian secondary forests are situated in contexts that are less favourable for carbon accumulation than the biome average. Our results demonstrate that old‐growth forest loss remains the most important factor determining the carbon balance in the Brazilian Amazon. Understanding the implications of these findings will be essential for improving estimates of secondary forest carbon sequestration potential. More accurate quantification of secondary forest carbon stocks will support the production of appropriate management proposals that can efficiently harness the potential of secondary forests as a low‐cost, nature‐based tool for mitigating climate change

Variações espaciais e temporais nas condições limnológicas de um lago de planície de inundação (lago Catalão) conectado aos rios Solimões e Negro, Amazônia Central

Lakes play an important role in biogeochemical, ecological and hydrological processes in the river-floodplain system. The aim of this study was to evaluate the dynamics of the limnological conditions of Catalão Lake, an Amazon floodplain lake. Thus, some of the main limnological environment variables (O2, temperature, pH, nutrient, electrical conductivity) of the Catalão Lake were analyzed under temporal and spacial scales. The study was conducted between November/2004 and August/2005. Sampling excursion were carried out every three months; one excursion for each of the four different hydrological periods (low water, rising water, high water and falling water). Sampling points were chosen so that it could be obtained a gradient of the distance from Negro River. Limnological profiles in Catalão Lake showed generally acidic to slightly alcaline water, with low levels of dissolved oxygen and low concentrations of soluble reactive phosphorous. The Negro River seems to exert the main influence during the rising water period, while the Solimões River is the principal controlling river during peak water. The Principal Component Analysis (PCA) grouped the seasonal collections by hydrological period, showing the formation of a north-south spatial gradient within the lake in relation to the limnological variables. Multivariate dispersion analysis based on distance-to-centroid method demonstrated an increase in similarity over the course of the hydrological cycle, as the lake was inundated in response to the flood pulse of the main river channels. However, the largest spatial homogeneity in the lake was observed in the epilimnion layer, during the falling water period. The daily analysis of variation indicated an oligomitic pattern during the years in which the lake was permanently connected to the Negro River. Although Catalão Lake receives large quantities of both black water from the Negro River and sediment-filled water from the Solimões River, the physical and chemical characteristics of the lake are more similar to those of the Solimões (várzea lake) than the Negro (blackwater lake).Os lagos exercem um papel importante nos processos biogeoquímicos, ecológicos e hidrológicos no sistema rio-planície de inundação. O objetivo do presente estudo foi avaliar a dinâmica das condições limnológicas do lago Catalão, um lago da planície de inundação amazônica. Algumas das principais variáveis limnológicas (por exemplo, O2, temperatura, pH, condutividade elétrica, nutrientes) do lago Catalão foram analisadas em uma escala temporal e espacial. O presente estudo foi realizado no período de novembro de 2004 a agosto de 2005. As amostragens foram trimestrais, com um total de quatro coletas, uma em cada fase do ciclo hidrológico (Seca, Enchente, Cheia e Vazante). Os pontos de amostragem foram escolhidos de modo a obter um gradiente de distância em relação ao rio Negro. No geral, as águas do lago Catalão mostraram-se pouco oxigenadas, ácidas a levemente alcalinas e com baixas concentrações de Fósforo Solúvel Reativo (FSR). A Análise de Componentes Principais (ACP) agrupou as estações de coleta por fases do ciclo hidrológico e evidenciou a formação de um gradiente espacial na distribuição das variáveis limnológicas, que vai da região mais ao norte até mais ao sul do lago. A influência do rio Negro sobre as águas do lago parece ser maior na enchente e a do rio Solimões na cheia. A análise de dispersão multivariada com abordagem baseada na distância ao centróide evidenciou o aumento da similaridade espacial em função da inundação. Contudo, a maior homogeneidade espacial do lago foi registrada no epilímnio, na fase de vazante. Os resultados da análise de variação diária indicaram que o lago Catalão apresenta comportamento oligomítico nos anos em que permanece conectado permanentemente ao rio Negro. Apesar de receber grande aporte de águas pretas (rio Negro) e brancas (rio Solimões), as características físicas e químicas das águas do Catalão permitem classificá-lo como um sistema mais próximo dos lagos de várzea típicos do que daqueles de águas preta

INTEGRAÇÃO DE DADOS GEO-ESPACIAIS PARA O MAPEAMENTO DE UNIDADE DA PAISAGEM NA REGIÃO DO TAPAJÓS

The stratification of the ecosystem in homogeneous regions is crucial for determining the spatial variation of environment variables in studies related to the carbon dynamics in the Amazonia. Based on the hypothesis that landscape heterogeneity is determined by the interaction of the different types of vegetation, relief and land use, the principal aim of this research was to present a methodological routine to generate a Landscape Unit (LU) map for the Tapajos region. The study area is localized between the latitudes 02o 24’ 2” S and 04o 01’ 1” S, and longitudes 55o 30’ 2” W e 54o 29’ 5” W, in the Para State. Boolean logic operations were applied for the integration of the thematic maps containing the information about landscape attributes. The LU map showed that despite primary forests is the dominant vegetation type in the region, around 28% of the study area suffered human intervention. The proposed routine was efficient in characterizing the landscape heterogeneity. The advantages of this method are the preservation of more representative vegetation types and the reduction of the number of sample units. This mapping is important for helping regional scale researches using from a high to a moderate spatial resolution approach (from 30 to 500 meters). Key words: Stratification, Amazon, GIS, land use, mappingA estratificação do ecossistema em regiões homogêneas é crucial para a determinação da variação espacial das variáveis ambientais nos estudos relativos à dinâmica do carbono na Amazônia. Baseado na hipótese de que a heterogeneidade da paisagem é determinada pela interação dos diferentes tipos de vegetação, relevo, e uso da terra, o objetivo principal dessa pesquisa foi apresentar uma rotina metodológica para gerar um mapa de Unidades da Paisagem (UP) para região do Tapajós. A área de estudo esta localizada entre as latitudes 02o 24’ 2” S e 04o 01’ 1” S, e longitudes 55o 30’ 2” W e 54o 29’ 5” W, no estado do Para. Para a integração dos mapas temáticos, contendo as informações dos atributos da paisagem, foram realizadas operações de lógica booleana. O mapa de UP mostrou que apesar das florestas primárias predominarem na região estudada, cerca de 28% da área já sofreu intervenção antrópica. A rotina proposta foi eficiente na caracterização da heterogeneidade da paisagem. As vantagens desse método são a preservação das tipologias mais representativas e a redução do número de unidades amostrais. Este mapeamento mostra-se importante para auxiliar pesquisas na escala regional e resolução espacial de alta a moderada (de 30 a 500 metros). Palavras-chave: Estratificação; Amazônia; SIG; uso da terra; mapeament

BANCO DE DADOS GEOGRÁFICOS COMO FERRAMENTA DE SUPORTE PARA O MAPEAMENTO E MONITORAMENTO DA REGIÃO DA FLORESTA NACIONAL DO TAPAJÓS (PA)

This article presents the results of mapping and monitoring of Tapajós National Forest (PA), one of the test area of LBA “Large Scale Biosphere-Atmosphere Experiment in Amazônia” Project, through the development of a geographic database. Remote sensing images (Landsat 1988, 1997, 1999 e 2001; RADARSAT 2002; Hyperion 2001; and aerial Videography 1999 and 2000), forest inventories of large sampling intensity and ancillary informations (thematic maps, topographic charts and annual cumulative precipitation data) were employed as information layers of the database. Through the integration of these informations, it was possible to produce a map of land cover for the Tapajós National Forest region and to evaluate its natural conservation. Keywords: Remote Sensing; Geoprocessing; Tropical Forest and Amazonia.Este artigo apresenta os resultados do mapeamento e monitoramento da Floresta Nacional (FLONA) do Tapajós (PA), uma das áreas teste do projeto LBA “Large Scale Biosphere-Atmosphere Experiment in Amazônia”, através do desenvolvimento de um banco de dados geográfico. Imagens de sensoriamento remoto (Landsat 1988, 1997, 1999 e 2001; RADARSAT 2002; Hyperion 2001; e Videografia aérea de 1999 e 2000), dados de inventários florestais (IF’s) de grande intensidade amostral e informações auxiliares (mapas temáticos, cartas topográficas e dados de precipitação acumulada anual) foram empregados como planos de informação no banco de dados. Através da integração dessas informações, foi possível produzir um mapa de cobertura vegetal para a região da Floresta Nacional do Tapajós e avaliar o seu estado de conservação. Palavras-Chave: Sensoriamento Remoto; Geoprocessamento; Floresta Tropical e Amazônia

Chlorthalidone plus amiloride reduces the central systolic blood pressure in stage 1 hypertension patients

Background: Hypertension reduction strategies use blood pressure in the brachial artery as the primary endpoint. Individuals who achieve the target blood pressure reduction with antihypertensive treatment have residual cardiovascular risk attributed to the difference in pressure between the aorta and brachial artery. Antihypertensive treatment affects the intrinsic properties of the vascular wall and arterial stiffness markers and consequently the central pressure. Recent publications stress the importance of adequate control of the central compared to peripheral blood pressure. Related clinical implications suggest that individuals with normal peripheral but high central blood pressure should not receive antihypertensive drugs that act on the central pressure. Therefore, they are at greater cardiovascular risk. The aim of the study was to evaluate the effect of treatment with a thiazide diuretic versus losartan on the central blood pressure in stage 1 hypertensive patients. Methods: Twenty-five patients were randomized to the chlorthalidone 25 mg/amiloride 5 mg group (q.d.) and 25 patients received losartan 50 mg (b.i.d). The central systolic blood pressure (CSBP) and augmentation index (AIx 75) were assessed using applanation tonometry. The paired t-test was used to compare the systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), pulse pressure (PP), CSBP and AIx 75 between the thiazide and losartan groups at baseline and after 6 months of treatment. Results: Significant reductions in CSBP (123.3 ± 14.2 vs. 113.4 ± 111.4, P = 0.0103) and AIx 75 (87.7 ± 9.6 vs. 83.8 ± 8.9, P = 0.0289) were observed after 6 months of drug treatment with chlorthalidone 25 mg/amiloride 5 mg (q.d.). The administration of losartan 50 mg (b.i.d) did not reduce the CSBP and there were insignificant changes in the AIx 75. Conclusions: Six-month treatment of chlorthalidone/amiloride but not losartan reduces the CSBP and AIx 75 in adults with stage 1 hypertension

Estimates of forest canopy height and aboveground biomass using ICESat

Exchange of carbon between forests and the atmosphere is a vital component of the global carbon cycle. Satellite laser altimetry has a unique capability for estimating forest canopy height, which has a direct and increasingly well understood relationship to aboveground carbon storage. While the Geoscience Laser Altimeter System (GLAS) onboard the Ice, Cloud and land Elevation Satellite (ICESat) has collected an unparalleled dataset of lidar waveforms over terrestrial targets, processing of ICESat data to estimate forest height is complicated by the pulse broadening associated with large-footprint, waveform-sampling lidar. We combined ICESat waveforms and ancillary topography from the Shuttle Radar Topography Mission to estimate maximum forest height in three ecosystems; tropical broadleaf forests in Brazil, temperate broadleaf forests in Tennessee, and temperate needleleaf forests in Oregon. Final models for each site explained between 59% and 68% of variance in field-measured forest canopy height (RMSE between 4.85 and 12.66 m). In addition, ICESat-derived heights for the Brazilian plots were correlated with field-estimates of aboveground biomass (r(2) = 73%, RMSE = 58.3 Mgha(-1))

Size and frequency of natural forest disturbances and Amazon carbon balance

Forest inventory studies in the Amazon indicate a large terrestrial carbon sink. However, field plots may fail to represent forest mortality processes at landscape-scales of tropical forests. Here we characterize the frequency distribution of disturbance events in natural forests from 0.01 ha to 2,651 ha size throughout Amazonia using a novel combination of forest inventory, airborne lidar and satellite remote sensing data. We find that small-scale mortality events are responsible for aboveground biomass losses of B1.28 Pg C y 1 over the entire Amazon region. We also find that intermediate-scale disturbances account for losses of B0.01 Pg C y 1 , and that the largest-scale disturbances as a result of blow-downs only account for losses of B0.003 Pg C y 1 . Simulation of growth and mortality indicates that even when all carbon losses from intermediate and large-scale disturbances are considered, these are outweighed by the net biomass accumulation by tree growth, supporting the inference of an Amazon carbon sink