1,720,960 research outputs found
Obtaining rubber plantation age information from very dense Landsat TM & ETM + time series data and pixel-based image compositing
No full textDetermining the age of rubber tree plantations (Hevea brasiliensis) is of great interest to plantation managers and land-use decision makers as it enables, among others, reliable forecasts of resource availability. The acquisition of age information with field campaigns, however, is time consuming, laborious and expensive. We present an approach that facilitates rapid assessment of rubber plantation age at regional scales applying very dense Landsat times series (LTS) satellite data over China's second largest rubber planting area - Xishuangbanna. We aggregated 270 Landsat TM and ETM + surface reflectance images into annual best-available-pixel composites of minimum Normalized Difference Moisture Index (NDMI). The annual composites were classified into vegetated and non-vegetated pixels applying a global NDMI threshold of 0. As it is common practice in Xishuangbanna to clear the land before a new plantation is established, the last year in which a pixel located in a rubber plantation, was classified as non-vegetated, was recorded as the year of plantation establishment. The resultant plantation age map was validated using a stratified random sample of 184 data points, collected by visual interpretation of historical Landsat data. A Root Mean Square Error (RMSE) of 2.5 years was achieved. We estimate that in 2015 50% of Xishuangbanna's rubber plantations had an age suitable for latex tapping (8-25 years), 27% were too young to be tapped (25 years) and will be presumably harvested for wood in the near future. The proposed technique enables acquisitions of accurate rubber plantation age information from Landsat time series and NDMI over large areas with the potential of providing insights into land cover dynamics and allowing for the development of improved management strategies and local decision support activities. (C) 2017 Elsevier Inc. All rights reserved.GTZ/BMZ Green Rubber Project [13.1432.7-001.00
Landscape transformation through the use of ecological and socioeconomic indicators in Xishuangbanna, Southwest China, Mekong Region
No full textRapid land-use transformations are occurring throughout the Mekong Region, and especially in Xishuangbanna, Yunnan Province in southwest China. Most of this is due to the spread of monoculture rubber plantations. Using a new map derived from Landsat and RapidEye imagery tracking the spread of rubber from 1992 to 2010 in combination with a literature review and interviews with key local experts and officials, we performed a general overview of the extent, causes and consequences of landscape transformation in Xishuangbanna. We discovered that structural and functional biodiversity has been reduced, habitat fragmentation has increased,,carbon sequestration in natural forests has been reduced, and hydrological systems altered. For humans, while incomes have risen, food insecurity has also grown. The drivers of these changes are regional economic integration, government policy, and conservation vs development value systems. To improve land-use management, we surveyed the availability of ecological and socioeconomic indicators that may better track such changes. We found that combining both types of indicators within a multi-scale conservation planning framework would help to inform policy making in the region. As yet, however, there is little integrative research using indicators to track changes in ecosystems and human livelihoods in the region. (C) 2012 Elsevier Ltd. All rights reserved
Standardizing the protocol for hemispherical photographs: accuracy assessment of binarization algorithms.
No full textHemispherical photography is a well-established method to optically assess ecological parameters related to plant canopies; e.g. ground-level light regimes and the distribution of foliage within the crown space. Interpreting hemispherical photographs involves classifying pixels as either sky or vegetation. A wide range of automatic thresholding or binarization algorithms exists to classify the photographs. The variety in methodology hampers ability to compare results across studies. To identify an optimal threshold selection method, this study assessed the accuracy of seven binarization methods implemented in software currently available for the processing of hemispherical photographs. Therefore, binarizations obtained by the algorithms were compared to reference data generated through a manual binarization of a stratified random selection of pixels. This approach was adopted from the accuracy assessment of map classifications known from remote sensing studies. Percentage correct (Pc) and kappa-statistics (K) were calculated. The accuracy of the algorithms was assessed for photographs taken with automatic exposure settings (auto-exposure) and photographs taken with settings which avoid overexposure (histogram-exposure). In addition, gap fraction values derived from hemispherical photographs were compared with estimates derived from the manually classified reference pixels. All tested algorithms were shown to be sensitive to overexposure. Three of the algorithms showed an accuracy which was high enough to be recommended for the processing of histogram-exposed hemispherical photographs: "Minimum" (Pc 98.8%; K 0.952), "Edge Detection" (Pc 98.1%; K 0.950), and "Minimum Histogram" (Pc 98.1%; K 0.947). The Minimum algorithm overestimated gap fraction least of all (11%). The overestimation by the algorithms Edge Detection (63%) and Minimum Histogram (67%) were considerably larger. For the remaining four evaluated algorithms (IsoData, Maximum Entropy, MinError, and Otsu) an incompatibility with photographs containing overexposed pixels was detected. When applied to histogram-exposed photographs, these algorithms overestimated the gap fraction by at least 180%
Can carbon-trading schemes help to protect China's most diverse forest ecosystems? A case study from Xishuangbanna, Yunnan
No full textXishuangbanna has been largely transformed from biodiverse natural forests and mixed-use farms into monoculture rubber plantations in just twenty years. This conversion has expanded into forests previously protected by the community and onto marginal sites at high-elevation. Market-based ecosystem payments, especially carbon financing, are potential tools to prevent further forest loss in China. Here, we compare rubber net present value (NPV), carbon sequestration, and seed-plant species diversity for Xishuangbanna given three land-use scenarios: Business-As-Usual (BAU), Economic Oriented Scenario (EOS) and Conservation Oriented Scenario (COS) using a previously published spatial map of rubber profitability. The EOS achieved the greatest rubber profit but caused substantial reductions in natural forest area, biodiversity and carbon stocks. The EOS also requires substantial immigration of workers into a remote and ecologically important region with little social infrastructure for basic security, food security, health-care and education, causing frequently ignored costs. As expected, the COS will maintain the highest levels of natural forest area, sequester 57% more carbon, and 71% more biodiversity than EOS. Given the conservation value of the carbon stores and rich biodiversity residing in Xishuangbanna's natural forests, reducing rubber NPV only marginally would probably cost less than attempting to recover these resources. We recommend that rubber plantations be limited to established, productive lowland areas whilst protecting intact high-elevation forest and reforesting low-productivity plantations. These actions will enhance carbon sequestration and biodiversity conservation. Management policies focused solely on profits, like the EOS scenario, will fail to sustain the entire range of natural resources and ecosystem services. The prices in the carbon market would have to be considerably larger than they are currently to compete with the profitability of rubber. (C) 2014 Elsevier Ltd. All rights reserved
Environmental stratification to model climate change impacts on biodiversity and rubber production in Xishuangbanna, Yunnan, China
No full textsponsorship: Partial funding for this work was generously provided by the International Development Research Centre (IDRC) - Canada through the "Building Effective Water Governance in the Asian Highlands Project (107085-002)", the CSIRO Exploring Mekong Region Futures 2009-2010 2009-2010 Project and the Project"Making the Mekong Connected" - MMC (project number 08.7860.3-001.00) both funded by the German Ministry for Economic Cooperation and Development (BMZ), as well as CGIAR Research Program 6 on Forests, Trees and Agroforestry. We acknowledge the German National Space Agency DLR (Deutsches Zentrum fur Luft- und Raumfahrt e.V.) for the delivery of RapidEye images as part of the RapidEye Science Archive (Proposal No. 390). The provision of RapidEye images was funded by the German Federal Ministry of Economics and Technology (BMWi). The responsibility for any use of the results presented in this paper lies with the user. (International Development Research Centre (IDRC) - Canada through the "Building Effective Water Governance in the Asian Highlands Project|107085-002, CSIRO Exploring Mekong Region Futures, Project"Making the Mekong Connected" - MMC|08.7860.3-001.00, German Ministry for Economic Cooperation and Development (BMZ), CGIAR Research Program 6 on Forests, Trees and Agroforestry, German Federal Ministry of Economics and Technology (BMWi))status: Publishe
Data from: Quantifying the factors affecting leaf litter decomposition across a tropical forest disturbance gradient
No full textDeforestation and forest degradation are driving unprecedented declines in biodiversity across the tropics, and understanding the consequences of these changes for ecosystem functioning is essential for human well-being. Forest degradation and loss alter ecosystem functioning through changes in species composition and abiotic conditions. However, the consequences of these changes for heterospecific processes are often poorly understood. Leaf litter decomposition is a major source of atmospheric carbon and critical for carbon and nutrient cycling. Through a highly replicated litter-bag experiment (3360 bags), we quantified the effects of litter quality, decomposer functional diversity and seasonal precipitation regime on litter decomposition along a tropical disturbance gradient in SW China. In addition, using soil and litter from sites selected from across the disturbance gradient, we established replicated litter-bed treatments and exposed these to a gradient of simulated canopy cover in a shade-house. Across the landscape, mass loss from litter-bags after 12 months varied from 7% to 98%. Even after 12 months, litter-bags installed at the beginning of the dry season had much lower mass loss than those installed at the beginning of the wet season. As expected, litter quality and faunal exclusion had substantial effects on decomposition rates. Decomposition rates declined along the disturbance gradient from mature forest, through regenerating forest to open land, although the effect size was strongly dependent on installation season. The effect of excluding meso- and macro-invertebrates increased with increasing forest degradation, whereas the effect of litter quality declined. Results from the shade-house experiment strongly suggested that forest degradation effects were driven predominantly by changes in micro-climatic conditions resulting from increased canopy openness. To better model the impacts of anthropogenic global change on litter decomposition rates, it will be important to consider landscape scale processes, such as forest degradation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Phylogenetic clustering increases with succession for lianas in a Chinese tropical montane rain forest
No full textPrevious research found that phylogenetic clustering increased with disturbance for tropical trees, suggesting that community assembly is mainly influenced by abiotic factors during early succession. Lianas are an important additional component of tropical forests, but their phylogenetic community structure has never been investigated. Unlike tropical trees, liana abundance is often high in disturbed forests and diversity can peak in old secondary forest. Therefore, phylogenetic structure along a disturbance gradient might also differ from tropical tree communities. Here we determined phylogenetic community structure of lianas along a disturbance gradient in a tropical montane forest in China, using the net relatedness index (NRI) from 100 equivalent phylogenies with varying branch length that were constructed using DNA-barcode sequences. Three additional phylogenetic indices were also considered for comparison. When NRI was used as index phylogenetic clustering of liana communities decreased with decreasing tree basal area, suggesting that liana competitive interactions dominate during early succession, which is in contrast to the pattern reported for trees. Liana communities in mature forests, on the other hand, were phylogenetic clustered, which could be caused by dispersal limitation and/or environmental filtering. The three additional phylogenetic indices identified different, sometimes contradicting predictors of phylogenetic community structure, indicating that caution is needed when generalizing interpretations of studies based on a single phylogenetic community structure index. Our study provides a more nuanced picture of non-random assembly along disturbance gradients by focusing on a non-tree forest component
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