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Search Results: 1 - 10 of 474810 matches for " Mark A. Cochrane "
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Forest Fragmentation and Its Potential Implications in the Brazilian Amazon between 2001 and 2010  [PDF]
Izaya Numata, Mark A. Cochrane
Open Journal of Forestry (OJF) , 2012, DOI: 10.4236/ojf.2012.24033
Abstract: In recent decades, human development pressures have results in conversions of vast tracts of Amazonian tropical rain forests to agriculture and other human land uses. In addition to the loss of large forest cover, remaining forests are also fragmented into smaller habitats. Fragmented forests suffer several biological and ecological changes due to edge effects that can exacerbate regional forest degradation. The Brazilian Amazon has had greatly contrasting land cover dynamics in the past decade with the highest historical rates of deforestation (2001-2005) followed by the lowest rates of forest loss in decades, since 2006. Currently, the basin-wide status and implications of forest fragmentation on remnant forests is not well known. We performed a regional forest fragmentation analysis for seven states of the Brazilian Amazon between 2001 and 2010 using a recent deforestation data. During this period, the number of forest fragments (>2 ha) doubled, nearly 125,000 fragments were formed by human activities with more than 50% being smaller than 10 ha. Over the decade, forest edges increased by an average of 36,335 km/year. However, the rate was much greater from 2001-2005 (50,046 km/year) then 2006-2010 (25,365 km/year) when deforestation rates dropped drastically. In 2010, 55% of basin-wide forest edges were < 10 years old due to the creation of large number of small fragments where intensive biological and ecological degradation is ongoing. Over the past decade protected areas have been expanded dramatically over the Brazilian Amazon and, as of 2010, 51% of remaining forests across the basin are within protected areas and only 1.5% of protected areas has been deforested. Conversely, intensive forest cover conversion has been occurred in unprotected forests. While 17% of Amazonian forests are within 1 km of forest edges in 2010, the proportion increases to 34% in unprotected areas varying between 14% and 95% among the studied states. Our results indicate that the Brazilian Amazon now largely consists of two contrasting forest conditions: protected areas with vast undisturbed forests and unprotected forests that are highly fragmented and disturbed landscapes.
Priority Areas for Establishing National Forests in the Brazilian Amazon
Adalberto Veríssimo,Mark A. Cochrane,Carlos Souza Jr.,Rodney Salom?o
Ecology and Society , 2002,
Abstract: Brazil will benefit if it gains control of its vast Amazonian timber resources. Without immediate planning, the fate of much of the Amazon will be decided by predatory and largely unregulated timber interests. Logging in the Amazon is a transient process of natural resource mining. Older logging frontiers are being exhausted of timber resources and will face severe wood shortages within 5 yr. The Brazilian government can avoid the continued repetition of this process in frontier areas by establishing a network of National Forests (Florestas Nacionais or Flonas) to stabilize the timber industry and simultaneously protect large tracts of forest. Flonas currently comprise less than 2% of the Brazilian Amazon (83,000 km2). If all these forests were used for sustainable logging, they would provide less than 10% of the demand for Amazonian timber. To sustainably supply the present and near-future demand for timber, approximately 700,000 km2 of the Amazon forest needs to be brought into well-managed production. Brazil's National Forest Program, launched in 2000, is designed to create at least 400,000 km2 of new Flonas. Objective decision-making tools are needed to site these new national forests. We present here a method for optimally locating the needed Flonas that incorporates information on existing protected areas, current vegetation cover, areas of human occupation, and timber stocks. The method combines these data in a spatial database that makes it possible to model the economic potential of the region's various forests as a function of their accessibility and timber values while constraining model solutions for existing areas of protection or human occupation. Our results indicate that 1.15 x 106 km2 of forests (23% of the Brazilian Amazon) could be established as Flonas in a manner that will promote sustainable forest management; these Flonas would also serve as buffer zones for fully protected areas such as parks and reserves.
Diversity of the land resources in the Amazonian State of Rond?nia, Brazil
Cochrane, T.T.;Cochrane, Thomas. A.;
Acta Amazonica , 2006, DOI: 10.1590/S0044-59672006000100011
Abstract: conflicting opinions are recorded in the literature concerning the suitability of amazon lands for sustainable agriculture following deforestation. this article has been written to shed light on this question by summarizing climate, landform, soil and vegetation features from the findings of a land resource study of the brazilian state of rond?nia in south-west amazonia. the work, which followed the world soils and terrain digital database (soter) methodology, was financed by the world bank. during the course of the survey special emphasis was given to studying soils; 2914 profiles were analyzed and recorded. the study identified a complex pattern of land units with clear differences in climate, landform, soils and native vegetation. forested areas mosaic with lesser areas of natural savannas. the latter occur on both poorly-drained and well-drained, albeit nutrient deficient sandy soils. the tallest and most vigorous forests or their remnants were seen growing on well-drained soils formed from nutrient-rich parent materials. many of these soils could, or are being used for productive agriculture. soils developed on nutrient-poor parent materials support forests that are significantly lower in height, and would require large lime and fertilizer inputs for agriculture. low forests with high palm populations and minor areas of wet land savannas cover the poorly drained soils. it is evident that forest clearing in the past was indiscriminant; this cannot be condoned. the diversity of land conditions found throughout rond?nia would suggest that many past studies in the amazon have simply been too broad to identify significant soil differences.
Diversity of the land resources in the Amazonian State of Rond nia, Brazil
Cochrane T.T.,Cochrane Thomas. A.
Acta Amazonica , 2006,
Abstract: Conflicting opinions are recorded in the literature concerning the suitability of Amazon lands for sustainable agriculture following deforestation. This article has been written to shed light on this question by summarizing climate, landform, soil and vegetation features from the findings of a land resource study of the Brazilian state of Rond nia in south-west Amazonia. The work, which followed the World Soils and Terrain Digital Database (SOTER) methodology, was financed by the World Bank. During the course of the survey special emphasis was given to studying soils; 2914 profiles were analyzed and recorded. The study identified a complex pattern of land units with clear differences in climate, landform, soils and native vegetation. Forested areas mosaic with lesser areas of natural savannas. The latter occur on both poorly-drained and well-drained, albeit nutrient deficient sandy soils. The tallest and most vigorous forests or their remnants were seen growing on well-drained soils formed from nutrient-rich parent materials. Many of these soils could, or are being used for productive agriculture. Soils developed on nutrient-poor parent materials support forests that are significantly lower in height, and would require large lime and fertilizer inputs for agriculture. Low forests with high palm populations and minor areas of wet land savannas cover the poorly drained soils. It is evident that forest clearing in the past was indiscriminant; this cannot be condoned. The diversity of land conditions found throughout Rond nia would suggest that many past studies in the Amazon have simply been too broad to identify significant soil differences.
Quantifying Responses of Dung Beetles to Fire Disturbance in Tropical Forests: The Importance of Trapping Method and Seasonality
Rafael Barreto de Andrade, Jos Barlow, Julio Louzada, Fernando Zagury Vaz-de-Mello, Mateus Souza, Juliana M. Silveira, Mark A. Cochrane
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0026208
Abstract: Understanding how biodiversity responds to environmental changes is essential to provide the evidence-base that underpins conservation initiatives. The present study provides a standardized comparison between unbaited flight intercept traps (FIT) and baited pitfall traps (BPT) for sampling dung beetles. We examine the effectiveness of the two to assess fire disturbance effects and how trap performance is affected by seasonality. The study was carried out in a transitional forest between Cerrado (Brazilian Savanna) and Amazon Forest. Dung beetles were collected during one wet and one dry sampling season. The two methods sampled different portions of the local beetle assemblage. Both FIT and BPT were sensitive to fire disturbance during the wet season, but only BPT detected community differences during the dry season. Both traps showed similar correlation with environmental factors. Our results indicate that seasonality had a stronger effect than trap type, with BPT more effective and robust under low population numbers, and FIT more sensitive to fine scale heterogeneity patterns. This study shows the strengths and weaknesses of two commonly used methodologies for sampling dung beetles in tropical forests, as well as highlighting the importance of seasonality in shaping the results obtained by both sampling strategies.
Wildfires in Bamboo-Dominated Amazonian Forest: Impacts on Above-Ground Biomass and Biodiversity
Jos Barlow, Juliana M. Silveira, Luiz A. M. Mestre, Rafael B. Andrade, Gabriela Camacho D'Andrea, Julio Louzada, Fernando Z. Vaz-de-Mello, Izaya Numata, Sébastien Lacau, Mark A. Cochrane
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0033373
Abstract: Fire has become an increasingly important disturbance event in south-western Amazonia. We conducted the first assessment of the ecological impacts of these wildfires in 2008, sampling forest structure and biodiversity along twelve 500 m transects in the Chico Mendes Extractive Reserve, Acre, Brazil. Six transects were placed in unburned forests and six were in forests that burned during a series of forest fires that occurred from August to October 2005. Normalized Burn Ratio (NBR) calculations, based on Landsat reflectance data, indicate that all transects were similar prior to the fires. We sampled understorey and canopy vegetation, birds using both mist nets and point counts, coprophagous dung beetles and the leaf-litter ant fauna. Fire had limited influence upon either faunal or floral species richness or community structure responses, and stems <10 cm DBH were the only group to show highly significant (p = 0.001) community turnover in burned forests. Mean aboveground live biomass was statistically indistinguishable in the unburned and burned plots, although there was a significant increase in the total abundance of dead stems in burned plots. Comparisons with previous studies suggest that wildfires had much less effect upon forest structure and biodiversity in these south-western Amazonian forests than in central and eastern Amazonia, where most fire research has been undertaken to date. We discuss potential reasons for the apparent greater resilience of our study plots to wildfire, examining the role of fire intensity, bamboo dominance, background rates of disturbance, landscape and soil conditions.
Ten-Year Landsat Classification of Deforestation and Forest Degradation in the Brazilian Amazon
Carlos M. Souza, Jr,Jo?o V. Siqueira,Marcio H. Sales,Ant?nio V. Fonseca,Júlia G. Ribeiro,Izaya Numata,Mark A. Cochrane,Christopher P. Barber,Dar A. Roberts,Jos Barlow
Remote Sensing , 2013, DOI: 10.3390/rs5115493
Abstract: Forest degradation in the Brazilian Amazon due to selective logging and forest fires may greatly increase the human footprint beyond outright deforestation. We demonstrate a method to quantify annual deforestation and degradation simultaneously across the entire region for the years 2000–2010 using high-resolution Landsat satellite imagery. Combining spectral mixture analysis, normalized difference fraction index, and knowledge-based decision tree classification, we mapped and assessed the accuracy to quantify forest (0.97), deforestation (0.85) and forest degradation (0.82) with an overall accuracy of 0.92. We show that 169,074 km 2 of Amazonian forest was converted to human-dominated land uses, such as agriculture, from 2000 to 2010. In that same time frame, an additional 50,815 km 2 of forest was directly altered by timber harvesting and/or fire, equivalent to 30% of the area converted by deforestation. While average annual outright deforestation declined by 46% between the first and second halves of the study period, annual forest degradation increased by 20%. Existing operational monitoring systems (PRODES: Monitoramento da Florestal Amaz?nica Brasileira por Satélite) report deforestation area to within 2% of our results, but do not account for the extensive forest degradation occurring throughout the region due to selective logging and forest fire. Annual monitoring of forest degradation across tropical forests is critical for developing land management policies as well as the monitoring of carbon stocks/emissions and protected areas.
The retrovirus RNA trafficking granule: from birth to maturity
Alan W Cochrane, Mark T McNally, Andrew J Mouland
Retrovirology , 2006, DOI: 10.1186/1742-4690-3-18
Abstract: The life of an mRNA is directed by the protein components of ribonucleoprotein particles (RNP) whose roles include nuclear processing reactions, transport, translation and degradation. Retroviral replication depends on many of the same processes to form viral mRNA and genomic RNA providing an experimentally tractable system to study the cis and trans determinants of mRNA fate. In this review, we summarize the current understanding of the processes affecting retroviral RNA metabolism as the RNA moves from its site of synthesis within the nucleus to its encapsidation into viral particles that emerge from the plasma membrane. The field has not only illuminated the cellular processes regulating RNA fate in general but also provided insights into potential strategies to impair replication of these viral pathogens.The expression of viral proteins from unspliced, incompletely spliced and fully spliced transcripts has necessitated that retroviruses evolve strategies to control the extent of RNA splicing. Extensive studies of avian sarcoma virus (ASV) splicing revealed three mechanisms of splicing control. The first involves the maintenance of suboptimal 3' splice site (ss) signals. Use of the env 3'ss is controlled by a suboptimal branchpoint (bpt) sequence and a nearby exonic splicing enhancer (ESE) [1,2] whereas the src 3' ss has a suboptimal pyrimidine tract (ppt) [3]. Mutations that improved the quality of the signals increased splicing and had detrimental effects on replication. Consistent with a requirement of inefficient splicing for optimal replication, revertants contained mutations that restored inefficient splicing. In addition to suboptimal splicing signals, a second, poorly characterized negative element is also present upstream of the src 3' ss [4,5]. Whether this element represents an intronic splicing silencer (ISS) and what factors bind to it remains to be determined. These two splicing control mechanisms are shared with HIV (discussed below). A third, nove
Quantum-Noise Power Spectrum of Fields with Discrete Classical Components
J. Harms,P. Cochrane,A. Freise
Physics , 2007, DOI: 10.1103/PhysRevA.76.023803
Abstract: We present an algorithmic approach to calculate the quantum-noise spectral density of photocurrents generated by optical fields with arbitrary discrete classical spectrum in coherent or squeezed states. The measurement scheme may include an arbitrary number of demodulations of the photocurrent. Thereby, our method is applicable to the general heterodyne detection scheme which is implemented in many experiments. For some of these experiments, e.g. in laser-interferometric gravitational-wave detectors, a reliable prediction of the quantum noise of fields in coherent and squeezed states plays a decisive role in the design phase and detector characterization. Still, our investigation is limited in two ways. First, we only consider coherent and squeezed states of the field and second, we demand that the photocurrent depends linearly on the field's vacuum amplitudes which means that at least one of the classical components is comparatively strong.
Natural Variation in the Strength and Direction of Male Mating Preferences for Female Pheromones in Drosophila melanogaster
Alison Pischedda, Michael P. Shahandeh, Wesley G. Cochrane, Veronica A. Cochrane, Thomas L. Turner
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0087509
Abstract: Many animal species communicate using chemical signals. In Drosophila, cuticular hydrocarbons (CHCs) are involved in species and sexual identification, and have long been thought to act as stimulatory pheromones as well. However, a previous study reported that D. melanogaster males were more attracted to females that were lacking CHCs. This surprising result is consistent with several evolutionary hypotheses but is at odds with other work demonstrating that female CHCs are attractive to males. Here, we investigated natural variation in male preferences for female pheromones using transgenic flies that cannot produce CHCs. By perfuming females with CHCs and performing mate choice tests, we found that some male genotypes prefer females with pheromones, some have no apparent preference, and at least one male genotype prefers females without pheromones. This variation provides an excellent opportunity to further investigate the mechanistic causes and evolutionary implications of divergent pheromone preferences in D. melanogaster males.
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