不同育苗环境对花椰菜生长发育的影响

通过研究不同育苗环境对花椰菜幼苗以及定植后花椰菜生育期、株高、花蕾变化的影响,为花椰菜育苗和栽培提供理论和实践依据。结果表明,在不同育苗环境下,花椰菜幼苗的生长状况存在显著差异,但在定植后,花椰菜生长发育间的差异则不再明显。综合考虑,在大田生产中,可在当地育苗以降低生产成本。     

Tree leafing phenology and crop productivity in semi-arid agroforestry systems in Kenya

The hypothesis that temporal separation of resource use between trees and crops minimises competition for wa ter in agroforestry systems during the cropping period and increases utilisation of annual rainfall was tested at Machakos in semi-arid Kenya. Four popular tree species were chosen to provide a range of leafing phenologies. These included Melia volkensii, which sheds its leaves twice a year, Senna spectabilis and Gliricidia sepium, which shed their leaves during the long dry season, and the evergreen Croton megalocarpus. All four species retained their foliage during the long rains, offering little scope for temporal separation of resource use. Maize (Zea mays) yields were reduced by 50–70% in the agroforestry treatments. Reductions in crop yield were strongly correlated with tree growth (r ² =0.94) and available soil moisture (r ² =0.88). G. sepium remained leafless for much of the short rains despite the presence of available soil water, and was least competitive with the bean crops (Phaseolus vulgaris) grown at this time. Reductions in crop yield in the agroforestry treatments were closely correlated with tree growth (r ² =0.99) and available moisture (r ² =0.79) during the 1996/97 short rains (158 mm), but not during the much wetter 1997/98 season (608 mm). Shading by trees or shade nets reduced crop yield, in contrast to previous studies in the semi-arid tropics. Low off-season rainfall during the study period (9% of annual rainfall compared to the long-term average of 20%) limited the potential for temporal separation of growing periods. Where the prospects for temporal or spatial separation in resource use are limited, shoot and/or root pruning may be necessary to manage competition between trees and crops. This revised version was published online in June 2006 with corrections to the Cover Date.     

不同环境下包被酸化剂对肉仔鸡生长性能、消化道内环境及血清生化指标的影响

本试验旨在研究不同环境下玉米-豆粕型基础饲粮中添加不同水平的包被酸化剂(CA)对肉仔鸡生长性能、消化道内环境及血清生化指标的影响.试验选用18日龄科宝500肉仔鸡960只,采用2×4交互设计,通过空气喷洒有害气体吸附剂改善鸡舍环境空气质量,将喷粉的鸡舍规定为良好环境,未喷粉的规定为较差环境,每个环境设4个组,分别为对照组、0.10％富马酸组、0.03％CA组和0.05％CA组,每组4个重复,每个重复30只鸡.肉仔鸡分别饲养在2个不同环境的鸡舍内,试验期25 d.结果表明:1)不同环境下,与对照组、0.10％富马酸组相比,0.03％CA组极显著增加了肉仔鸡平均日采食量(P＜0.01),显著提高了盲肠乳酸杆菌数量(P＜0.05);0.05％CA组盲肠双歧杆菌数量极显著高于其他各组(P＜0.01),各组胃肠道pH差异不显著(P＞0.05).2)良好环境下,0.03％CA组肉仔鸡血清总蛋白含量极显著低于其他各组(P＜0.01),0.05％ CA组盲肠大肠杆菌数量显著低于0.10％富马酸组和0.03％CA组(P＜0.05).3)较差环境下,0.03％CA组盲肠大肠杆菌数量显著低于其他各组(P＜0.05),0.05％CA组空肠乳酸杆菌数量显著高于其他各组(P＜0.05).4)对于平均日采食量、盲肠大肠杆菌和双歧杆菌数量、血清碱性磷酸酶和总超氧化物歧化酶活性,CA与环境的互作效应极显著(P＜0.01);对于盲肠乳酸杆菌和空肠乳酸杆菌数量,CA与环境的互作效应显著(P＜0.05).由此可见,添加CA能够改善肠道微生态环境,促进肉仔鸡生长;在良好环境下,CA的作用效果更好.     

北方日光温室土壤有机质累积特征研究

对山西日光温室有机肥施用状况和土壤有机质累积特征进行了调查和取样分析,研究结果表明:山西日光温室土壤有机肥施用量较低;日光温室土壤有机质含量处于缺乏水平,变幅为6.69~37.23g/kg;日光温室土壤有机质累积出现“南高北低”的变化趋势;设施生产中的“土壤”有失去原有功能而变为“载体”的趋势。     

Landscape planning and stress

Stress and stress-related illnesses, as reflected in medical records, have increased dramatically among adults and children in Western societies. A growing part of the budget for medical service in Sweden is used for individuals suffering from different stress-related illnesses such as burnout syndrome, insomnia and fatigue, depression, feelings of panic, etc. In this paper, we present results from a study in which 953 randomly selected individuals in nine Swedish cities answered a questionnaire about their health and their use of different urban open green spaces in and close to the city.The results indicate that city landscape planning may affect the health of town-dwellers. Statistically significant relationships were found between the use of urban open green spaces and self-reported experiences of stress – regardless of the informant's age, sex and socio-economic status. The results suggest that the more often a person visits urban open green spaces, the less often he or she will report stress-related illnesses. The same pattern is shown when time spent per week in urban open green spaces is measured.The distance to public urban open green spaces seems to be of decisive importance, as is access to a garden, in the form of a private garden or a green yard immediately adjacent to, for instance, an apartment building. People do not usually compensate for lack of green environments in their own residential area with more visits to public parks or urban forests.According to our results, laying out more green areas close to apartment houses, and making these areas more accessible, could make for more restorative environments. Outdoor areas that provide environments free from demands and stress, and that are available as part of everyday life, could have significant positive effects on the health of town-dwellers in Sweden. This may also apply to other Western societies.     

农业机器人导航中两类纹理边缘的快速跟踪与透视变换

野外田间的主动摄像机视觉,尤其是对作物割过与未割过的高相似颜色表面进行实时识别与跟踪是一项极具挑战性的工作。提出了两种全新的快速分割方法,以用于农业机器人导航。其关键是基于多尺度特征提取,通过求取k-层行像素极值的加权均值来形成窄带兴趣区,以及基于相邻行像素两类特征证据增强与多证据模糊判别进行分割增强。提出了新的方法,分割出导向线能够自适应环境的一些变化。同时,本研究还提出了一种快速透视变换算方法和摄像机主姿态的一次性校正方法,能够在1 ms内完成对分割导向线参数的透视投影变换,在0.5 s内通过自校正获取相机的主姿态角。开发了一套对园艺草割过与未割过的边缘进行在线跟踪的分析软件。试验和相应的误差分析结果令人满意（160×120显示分辨率下,能在55 ms内自主做出经透视投影变换的作业机理想移动方向决策,普通难度的相似颜色序列图像的分割误差被控制在了平均5%以内）。对最佳适应步法（BFS）做了改进,提出了多行最佳适应步法（MR-BFS）,在不降低正确性的前提下使其分割速度提高了100%以上。通过折衷组合多行最佳适应步法（MR-BFS）与多证据模糊增强法（MEFE）进行在线试验,获得了160×120分辨率下8～9帧/秒的边缘自动跟踪性能。边缘跟踪试验显示：自然图像中的不同色块和阴影对其分割影响不大,能够快速输出导向跟踪参数。如果待分割纹理表面的颜色距离相对较远,还可采用本文新提出的颜色分量运算＋颜色位屏蔽方法。该方法能在320×240分辨率下,在20～30 ms内实现全帧的鲁棒分割,获得田间实时的多边缘跟踪性能。该方法避免了耗时的计算和人的操作介入,可被进一步应用于农业机器人的实际导航控制中。     

Erosion assessment and administration in subtropical China: A case study from Fujian Province

Soil erosion continues to represent a major environmental issue in China. This paper considers some of the practical difficulties of assessing the severity of soil erosion in subtropical southern China, with particular reference to a case study in Fujian Province. The administration of soil and water conservation and procedures for erosion evaluation in an area of southern China are outlined. Although the hierarchy of bodies involved in soil conversation is impressive compared to other countries in subtropical environments, little is known about the dynamics of erosion, its impact on productivity or its contribution to sediment yields.     

台风暴潮对浙东沿海农田生态环境的影响及其对策

研究了1997年11号台风引起的台风暴潮对浙东沿海地区农田生态环境的影响。结果表明,受海水浸泡的影响,土壤和农用灌溉水含盐量显著升高,浸泡72h及72h以上表层土壤含盐量分别达1.27%和1.38%;在海水倒灌发生后8d农用灌溉水表层、3m、6m和10m深层水含盐量分别为2.36‰、3.22‰、3.84‰和4.03‰,尽管海水退落后各深层水含盐量有所下降,但总体仍维持在2.26‰左右,二者含盐量均远超过农业生产标准。进而提出了清理枯株、深沟翻耕、优化农作物种植结构和实施栽培管理措施等恢复受咸农田生态环境的对策。     

Concentrated flow erosion rates as affected by rock fragment cover and initial soil moisture content

Concentrated flow experiments using a small hydraulic flume and a constant flow discharge and bed slope have been conducted in order to investigate the effects of rock fragment cover (Rc) on sediment yield for an initially wet and an initially air-dry loamy topsoil. The experimental results indicate that Rc reduces concentrated flow erosion rates (E) in an exponential way (i.e., E=e^−bRc), which is similar to previously reported relations for other water erosion processes such as interrill erosion and sheet-rill erosion measured on runoff plots. The decay rate (b) of this exponential relationship increased throughout the experiments because of scour-hole development and bed armouring. The concentrated flow erosion rates and b-values also depend on the initial moisture content of the topsoil. Depending on Rc, mean concentrated flow erosion rates were 20% to 65% less on initially wet compared to initially air-dry topsoils. The mean value for b was 0.032 for the initially wet, but only 0.017 for the initially air-dry topsoil, indicating that a rock fragment cover is less efficient in reducing concentrated flow erosion rates when the topsoil is initially air-dry than when it is initially wet. The results help explain the data scatter in reported relationships between Rc and interrill–rill erosion rates. They also indicate that a given surface rock fragment cover will offer more protection to wet topsoils than to dry topsoils, which are very common in Mediterranean environments. Event-based water erosion models should incorporate effects of antecedent soil moisture content as well as those of Rc on concentrated flow erosion rates.     

新世纪人居环境的塑造

通过对改革开放以来广州住宅小区居住环境发展进程的研究,结合实例从住宅小区居住环境的发展初期、发展中期到相对成熟期的变迁分析了区域性人居环境的基本特征,提出了新世纪岭南地区人居环境的理想模式。