Satellite-based investigation of flood-affected rice cultivation areas in Chao Phraya River Delta,Thailand

The occurrence of catastrophic floods in Thailand in 2011 caused significant damage to rice agriculture. This study investigated flood-affected rice cultivation areas in the Chao Phraya River Delta (CRD) rice bowl, Thailand using time-series moderate resolution imaging spectroradiometer (MODIS) data. The data were processed for 2008 (normal flood year) and 2011, comprising four main steps: (1) data pre-processing to construct time-series MODIS vegetation indices (VIs), to filter noise from the time-series VIs by the empirical mode decomposition (EMD), and to mask out non-agricultural areas in respect to water-related cropping areas; (2) flood-affected area classification using the unsupervised linear mixture model (ULMM); (3) rice crop classification using the support vector machines (SVM); and (4) accuracy assessment of flood and rice crop mapping results. The comparisons between the flood mapping results and the ground reference data indicated an overall accuracy of 97.9% and Kappa coefficient of 0.62 achieved for 2008, and 95.7% and 0.77 for 2011, respectively. These results were reaffirmed by close agreement (R² > 0.8) between comparisons of the two datasets at the provincial level. The crop mapping results compared with the ground reference data revealed that the overall accuracies and Kappa coefficients obtained for 2008 were 88.5% and 0.82, and for 2011 were 84.1% and 0.76, respectively. A strong correlation was also found between MODIS-derived rice area and rice area statistics at the provincial level (R² > 0.7). Rice crop maps overlaid on the flood-affected area maps showed that approximately 16.8% of the rice cultivation area was affected by floods in 2011 compared to 4.9% in 2008. A majority of the flood-expanded area was observed for the double-cropped rice (10.5%), probably due to flood-induced effects to the autumn–summer and rainy season crops. Information achieved from this study could be useful for agricultural planners to mitigate possible impacts of floods on rice production.     

Global change and the intensification of agriculture in the tropics

Bridging understanding of local environmental change with regional and global patterns of land-use and land-cover change (LUCC) remains a key goal and challenge for our understanding of global environmental change. This meta-analysis attempts to bridge local and regional scales of LUCC by demonstrating the ways in which previously published case studies can be compared and used for a broader regional synthesis in the tropics. In addition to providing results from a meta-analysis, this paper suggests ways to make future case studies more widely comparable.     

基于EA-SD模型的生态农业系统模拟与优化调控——以平凉市崆峒区为例

以甘肃省平凉市崆峒区生态农业系统为例,基于农业产业链的物质、能量流动机理,运用Vensim软件建立生态农业系统动力学分析模型（EA-SD）。量化分析和模拟了生态农业发展的综合效益及其演变趋势。经模拟,按照现在的发展模式不变,系统不但存在牛粪尿污染等负效应,而且随着肉牛年屠宰量的快速上涨,未来崆峒区可能出现肉牛数量锐减,制沼产业、有机农业衰落,整个系统难以持续发展的情况。根据模拟结果,论文制定了系统优化调控政策,并模拟了优化后系统的发展情景。结果显示,优化能够消除系统缺陷和负效应,提升综合正效应,增强系统的可持续发展能力。本研究的模型及调控过程能够为类似的生态经济系统优化研究提供借鉴和参考。     

近40年河北省地表干燥度的时空变化

利用河北省1970-2007年48个气象台站逐日资料, 采用Penman-Monteith模型计算潜在蒸散量, 由潜在蒸散量和降水量之比构建干燥度指数, 并采用Kriging插值法进行空间插值以分析其区域特征。结果表明:1970-1985年, 由于降水量减少和潜在蒸散量减少, 蒸散量的减少速率大于降水量的减少速率, 地表干燥度指数呈下降趋势, 潜在蒸散量的显著减少是地表干燥度下降的主要原因, 而风速和日照时数的显著降低决定了潜在蒸散量的显著下降; 1986-2007年, 由于年平均气温的显著升高, 潜在蒸散量增加, 使得地表干燥度略呈上升趋势。河北省地表干燥度高值区分布在张家口地区的桑洋盆地和坝西高原, 而低值区主要在燕山南麓低山丘陵地区的承德西南部、唐山的北部和秦皇岛中北部大部分地区。干燥度减少区域主要集中在河北省东北部至河北省西部的带状区域。     

Farming the urban fringes of Barcelona: Competing visions of nature and the contestation of a partial sustainability fix

While the concept of urban agriculture investigates the way in which disused land within the consolidated city is returned to its citizens through a variety of farming practices, many pockets of rural land in peri-urban areas continue to be contested by institutions and communities – including informal farmers, formal farmers, municipal planners, metropolitan agencies, and investors – with contrasting interests. To date however, little scholarly attention has been paid to informal practices within the degraded areas of urban fringes and, more specifically, to the link between the expansion of peri-urban agriculture and the civic appropriation and negotiation of space in neglected peripheral areas. In this paper, we ask how a metropolitan sustainability fix is produced and contested both materially and discursively. We also explore how local residents involved in peri-urban agriculture claim the use of land for agricultural practices and in turn attempt to influence the urban agenda of the neoliberal city. Inquiring how competing visions of nature act as obstacles in this negotiation process, our analysis of the peri-urban Baix Llobregat Agricultural Park in Barcelona reveals that the imposition of official visions about how needs for food and agriculture should be fulfilled, which landscapes are esthetically acceptable, what nature is, and how land should be controlled and developed indicate why apparently “marginal” and informal urban agriculture in the periphery has come to be subordinated to the planning of the neoliberal city and of a metropolitan sustainability fix – a partial sustainability fix that is however progressively being questioned and renegotiated.     

矿山排供结合探讨

本文解决大水矿床排供结合问题是国民经济建设中具有实际意义的重要课题。本文较系统地论述了解决排供矛盾和排供结合的办法。着重从地质一水文地质条件,从矿山排水前后矿床地下水的补给、迳流、排泄条件来论证对排供结合方案的选择,并以一个典型的矿床作为实例加以阐明。     

The economic impact of climate change on Kenyan crop agriculture: A Ricardian approach

This paper measures the economic impact of climate on crops in Kenya. We use cross-sectional data on climate, hydrological, soil and household level data for a sample of 816 households. We estimate a seasonal Ricardian model to assess the impact of climate on net crop revenue per acre. The results show that climate affects crop productivity. There is a non-linear relationship between temperature and revenue on one hand and between precipitation and revenue on the other. Estimated marginal impacts suggest that global warming is harmful for crop productivity. Predictions from global circulation models confirm that global warming will have a substantial impact on net crop revenue in Kenya. The results also show that the temperature component of global warming is much more important than precipitation. Findings call for monitoring of climate change and dissemination of information to farmers to encourage adaptations to climate change. Improved management and conservation of available water resources, water harvesting and recycling of wastewater could generate water for irrigation purposes especially in the arid and semi-arid areas.     

ON THE ORIGIN OF RICE AGRICULTURE IN SOUTHERN CHINA AND ITS PROPAGATION EAST ASIA

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Discussion of “Neuro-fuzzy models employing wavelet analysis for suspended sediment concentration prediction in rivers”

Citation Abrahart, R.J. & Mount, N.J. (2011) Discussion of “Neuro-fuzzy models employing wavelet analysis for suspended sediment concentration prediction in rivers by S.A. Mirgagheri et al. (2010, Hydrol. Sci. J. 55(7), 1175–1189).” Hydrol. Sci. J. 56(7), 1325–1329.     

农田表面粗糙度参数的测量与精度分析

表面粗糙度是有效解释雷达后向散射系数和微波辐射亮度温度的关键参数之一。表面粗糙度参数的测量精度受到测量方法、测量仪器、数据预处理等的影响,如何获取到表面粗糙度的"真"值是地表粗糙度测量急需解决的问题,并且有助于提高利用微波遥感技术反演地表参数的能力。本文利用激光扫描仪的二维高度数据和蒙特卡罗方法模拟的一维表面高度数据,分析了重复采样次数、采样间隔、采样剖面长度、空间自相关函数类型和大尺度结构(数据倾斜和农田垄行结构)对表面粗糙度精度的影响,研究表明:在大于20次重复采样、小于10mm的采样间隔、200倍相关长度的剖面长度的条件下,农田表面粗糙度参数的测量精度约为80%;分形相关函数与实测农田表面的空间自相关系数的吻合性要高于高斯函数和指数函数;数据倾斜和农田垄行结构严重影响表面粗糙度参数的结果,在进行表面粗糙度参数的计算之前,需从剖面高度分布数据中去除以上两个因素的影响。