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31.
黄蟹“和”绿蟹“的鉴别方法及两者的蜕壳死亡率 总被引:1,自引:0,他引:1
介绍了中华绒螯蟹蟹种中“黄蟹”和“绿蟹”的鉴别方法,报导了用这两种蟹种进行对照饲养试验的结果。 相似文献
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33.
In this paper the results of the first comprehensive study on perception of and satisfaction with urban forests and green space in seven Southeast European cities are presented. The aims of the paper are to analyse 1) citizen perceptions of the current state of urban forests and green space in their cities, 2) to what extent current urban forests and green space meet their needs and how this can be improved. A cross-sectional study was conducted by using a common face-to-face survey questionnaire. Respondents were selected based on census data though a stratified sampling procedure by taking into account age, gender and city district (n = 384 in each city). The results showed that citizens genuinely care for urban forests and green space in their cities, but are not satisfied with their current state. The respondents found issues related to misbehaviour of other users, the presence and quality of facilities, as well as the presence and quality of management or maintenance the most pressing. There were more statistically significant differences than similarities between cities. Socioeconomic variables explained perceptions only to some extent. Citizens were very supportive of educational campaigns about the importance of urban forests and green space as well as of better enforcement of the existing regulations though having more community wardens that were expected to tackle current unsatisfactory situations. Urban planning and urban forest and green space management in these cities are facing many problems characteristic for post-socialist countries. Study findings are expected to contribute to decision making in urban planning and natural resource management. 相似文献
34.
Recent studies have emphasized the presence of microclimates in urban settings, but most do not have the high resolution observations necessary to understand the interactions taking place at a neighborhood scale. This study used a network of 10 identical weather stations and high resolution land cover data in Knoxville, Tennessee, to analyze the microclimates of a medium-sized city with a temperate climate. Two stations were installed in each of four urban neighborhoods in locations with varying localized tree cover, and two additional stations were installed in the center of downtown and in a nearby urban nature center. The intra-neighborhood results suggested that there is significant temperature variability within a single neighborhood based on the tree canopy density immediately surrounding a given weather station. However, the inter-neighborhood variability (differences between neighborhoods) was similar in magnitude, which suggests that the overall differences in neighborhood characteristics also have an effect on climate. Land cover at the neighborhood scale (in particular tree canopy percentages at the 500-m radii) had the highest correlation with the minimum daily temperature (Tmin) during the summer season. Maximum daily temperature (Tmax) relied most on the distance of each station from Downtown and the amount of impervious area in the 50 m surrounding each station. Tmax was also most influenced by surrounding land cover during dry conditions (a Dry Moderate air mass). Overall, highly localized impervious land cover percentages and larger-scale forested canopy were important in explaining temperature fluctuation, pointing to the importance of scale in microclimate assessments. Dry air masses enhanced the relationship between land cover and temperature during the day, while moist air masses did the same overnight. These data can be used to better inform planning strategies to build resiliency to extreme heat into urban environments by considering the influence of tree canopy. 相似文献
35.
This study examines the impact of green space health on local flooding based on the analysis of eighty-two watersheds in four Texas metropolitan statistical areas: Dallas, Houston, San Antonio, and Austin. The runoff records in October 2007 and October 2012 were selected for the assessment. The study met the methodological challenge posed by comparison by using the Normalized Difference Vegetation Index (NDVI) datasets produced based on the Moderate Resolution Imaging Spectroradiometer (MODIS) imagery of the 250-m resolution as a proxy to represent the health of green space. Two linear regression models were employed to explain the variation in mean daily runoff depth in 2007 and 2012, while controlling multiple contextual variables.Results indicate that watersheds containing healthier green spaces were likely to generate lower amounts of runoff in both periods. Standardized coefficients of green space health also show that the NDVI is a powerful and significant predictor to explain variation in runoff. These findings illustrate the important role of urban green spaces in attenuating local flooding and may provide planners and decision-makers with a method to consider, using this kind of objective greenery index in further developing local and regional green infrastructure and land-use plans. 相似文献
36.
不同温度下圆叶决明降解过程红壤可溶性氮及氮水解酶动态变化研究 总被引:1,自引:0,他引:1
为了探明圆叶决明(Chamaecrista rotundifolia)降解过程果园红壤供氮水平的变化规律,本研究采用模拟培养试验,研究15℃和25℃培养果园红壤硝态氮、铵态氮、可溶性总氮、可溶性有机氮含量的变化及脲酶、蛋白酶、天冬酰胺酶活性的变化。结果表明,圆叶决明降解过程果园红壤4种可溶性氮含量均显著提高,且在培养140 d达到最大值,25℃培养的效果更佳。其中,可溶性总氮、可溶性有机氮和硝态氮含量随时间的动态变化可用三次曲线方程来拟合。圆叶决明降解过程还能显著提高脲酶、蛋白酶和天冬酰胺酶的活性,其中蛋白酶活性和脲酶活性的变化可用指数方程和三次曲线方程来拟合。本研究认为圆叶决明降解过程可提高果园红壤可溶性氮含量,因此可通过翻压圆叶决明提高土壤的供氮水平。 相似文献
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通过对濮阳市主要交通性道路绿地景观建设的调查与分析,分别从树种选择、生态效应、景观效果等方面进行评价,总结了值得学习和借鉴的道路绿地景观设计特点,对道路绿地景观存在的问题加以分析,并提出相应的解决办法。 相似文献
38.
节水农业是水资源高效利用和农业可持续发展的重大问题,对于节约水资源具有极其重要的意义。为了解当前绿色农业高效节水领域的最新研究热点和发展趋势,本文梳理总结了我国现代化节水农业领域的基础背景、研究现状以及发展态势。结果表明,“灌溉设备与技术开发”、“农业用水精量调配与控制”、“作物高效用水机理”及“农业用水对环境变化的响应”等是近年来的研究热点,并建议开展水肥一体化智能技术与管理及其对作物、土壤、环境、社会等综合效应等的相关研究,以期为我国农业绿色高质量发展提供帮助。 相似文献
39.
通过探讨秸秆还田与化肥减施下间作绿肥对木薯产量性状的影响,着力解决连作木薯土壤肥力提高与改良相关技术的协调增效。于2019-2020年,以木薯品种“南美1号”为供试材料,设置8个处理,调查每个小区的木薯茎径、叶绿素(SPAD)、块根直径、块根长、单株茎秆鲜重、单株块根鲜重、株高、单片叶重、单株块根数以及小区产量等农艺性状。结果表明,处理5(木薯秆还田+化肥减量12.5%+12.5%营养元素当量黑豆绿肥还田)的木薯产量最高,并得到拟合方程。绿肥秸秆还田以及间作绿肥从整体上改良了土壤肥力,并通过显著影响木薯块根、单片叶重以及单株块根数而影响最终产量。 相似文献
40.
不同绿茶品种区域试验研究 总被引:1,自引:0,他引:1
本文对16个无性系绿茶品种的成活率、新梢物候期、发芽密度、鲜叶产量、制茶品质、抗性等性状进行分析,为国家级良种鉴定提供科学依据.结果表明,苏茶早、元宵绿、中茶108、武义早等4个品种为特早生种;中茶108、81-8-30、中茶302等3个品种的产量极显著高于CK种,武义早的产量显著高于CK种;桂香18、六杯香、鸠20、中茶302、春波绿、81-8-30、南江1号等7个品种的品质优于CK;中茶108、81-8-30等2个品种的耐寒性表现为强,浙农139、中茶302、桂香18等3个品种的耐旱性表现为强. 相似文献