由降雨侵蚀引起的山坡面水土流失的研究进展

20世纪末，坡面降雨水土流失的研究日益深入。经验性模型是根据实际资料应用统计相关的方法建立起来的，其结构简单，使用方便。物理过程模拟模型试图对流域内发生的侵蚀产沙过程进行概化和近似，并用数学方程描述流域上侵蚀产沙的主要物理过程，再用比较严格的数值解法计算水沙运动过程，同时人们对侵蚀机理的研究也得到了深入发展。     

作物水分氮素生产函数模型的研究

在水分生产函数动态产量模型的基础上,考虑土壤氮素对作物生长的影响,建立了作物水分 氮素生产函数动态产量模型,根据作物生长过程中水分和氮素状态,可以对干物质生长过程进行跟踪和预测预报,利用北京永乐店试验资料进行模型参数的拟合,并应用该模型对不同生育阶段干物质产量进行预测,效果良好。     

Water management for irrigation,crop yield and social attitudes: a socio-agricultural agent-based model to explore a collective action problem

ABSTRACT

When rainfall does not meet crop water requirements, supplemental irrigation is needed to maintain productivity. On-farm ponds can prevent excessive groundwater exploitation – to the benefit of the whole community – but they reduce the cultivated area and require investments by each farmer. Thus, choosing the source of water for irrigation (groundwater vs on-farm pond) is a problem of collective action. An agent-based model is developed to simulate a smallholder farming system; the farmers’ long-/short-view orientation determines the choice of the water source. We identify the most beneficial water source for economic gain and its stability, and how it can change across communities and under future climate scenarios. By using on-farm ponds, long-view-oriented farmers provide collective advantages but have individual advantages only under extreme climates; a tragedy of the commons is always possible. Changes in farmers’ attitudes (and hence sources of water) based on previous experiences can worsen the economic outcome.     

新疆气象灾害对主要作物产量影响的灰色关联分析

利用1978-2014年洪涝、旱灾、风雹灾及低温冷冻四种农业气象灾害受灾面积、同期粮食平均单产及粮食作物单产有关统计数据，采用线性和灰色关联分析方法，对新疆37a的主要农业气象灾害特征及其对主要粮食作物、主要经济作物单产的影响进行分析。新疆农业气象灾害灾情总体呈受灾面积大、成灾率高、波动幅度大的特点。旱灾和雹灾对新疆的粮食生产危害较大，低温冷冻灾害和洪涝灾害其次。从作物种类来看，不同作物与旱灾受灾面积关联度最大，冬小麦、春小麦和玉米与低温冷冻灾害受灾面积的关联度最小，而棉花和甜菜与洪涝灾受灾面积的关联度最小。旱灾和雹灾是影响新疆农业生产的主要气象灾害。     

Comparison of three remotely sensed drought indices for assessing the impact of drought on winter wheat yield

ABSTRACT

Agricultural drought threatens food security. Numerous remote-sensing drought indices have been developed, but their different principles, assumptions and physical quantities make it necessary to compare their suitability for drought monitoring over large areas. Here, we analyzed the performance of three typical remote sensing-based drought indices for monitoring agricultural drought in two major agricultural production regions in Shaanxi and Henan provinces, northern China (predominantly rain-fed and irrigated agriculture, respectively): vegetation health index (VHI), temperature vegetation dryness index (TVDI) and drought severity index (DSI). We compared the agreement between these indices and the standardized precipitation index (SPI), soil moisture, winter wheat yield and National Meteorological Drought Monitoring (NMDM) maps. On average, DSI outperformed the other indices, with stronger correlations with SPI and soil moisture. DSI also corresponded better with soil moisture and NMDM maps. The jointing and grain-filling stages of winter wheat are more sensitive to water stress, indicating that winter wheat required more water during these stages. Moreover, the correlations between the drought indices and SPI, soil moisture, and winter wheat yield were generally stronger in Shaanxi province than in Henan province, suggesting that remote-sensing drought indices provide more accurate predictions of the impacts of drought in predominantly rain-fed agricultural areas.     

给水度测定方法研究

本文对影响给水度的因素进行了综合分析．对给水度研究方法予以评价．结合试验研究．提出了在生产实际中精确测定变值给水度的方法。     

广东冬季寒害对香蕉产量的影响

广东丰富的气候资源有利于香蕉生产的发展，但冬季寒害仍可使香蕉生产遭受重大损失，即使冬季最温暖的粤西南亦难幸免。阐述了广东香蕉寒害发生的情况，对几次突出的冬季寒害及其危害进行分析。严重影响广东香蕉主产区的寒害虽然平均约5年左右一遇，但是20世纪90年代寒害出现较频繁，加上反季节种植的春夏蕉由于经济效益较高，种植面积迅速扩大，使得其抽蕾或花芽分化在冬季，造成香蕉遭受寒害的几率增大，对香蕉产量影响很大。为此，广东香蕉生产的发展要重视寒害、风害及市场变化带来的风险，必须因地因时制宜，合理布局，搞好防灾减灾。     

SEDIMENT BUDGET OF THE ILLINOIS RIVER

1 BACKGROUND The Illinois River is the most significant river in the state of Illinois. The river drains nearly half of the state and has a drainage area of 28,906 mi2 (74,867 km2). Except for about a 4,000 mi2 (10,360 km2) area in Indiana and Wisconsin, the watershed is located in Illinois (see Fig. 1). The watershed contains the drainage basins of several of the state's significant rivers such as the Sangamon, LaMoine, Spoon, Mackinaw, Vermilion, Fox, Kankakee, and Des Plaines Ri…     

Sustaining productive ecosystems in face of risk

Ecosystems lacking human induced energy input from outside are in danger to degrade if man requires any sustainable yield. The risk of failure strongly depends on the amount of exploitation. This is shown by a simple one dimensional analytical feed-back model. Natural fluctuations determine the degradation probability of productive ecosystems. The stability behaviour of the latter is demonstrated by an analytical model in the two dimensional phase space. Full quantitative evaluation of the risk needs simulation experiments. One is carried out in the thorn shrub savannah rangelands at a site in Namibia where a fully calibrated simulation model shows that the less a sustainable yield is required, the more the breakdown is delayed. In this case of highly fluctuating rainfall any sustainability sensu strictu does not exist. This revised version was published online in August 2006 with corrections to the Cover Date.