全球气候变化对我国干旱区影响分析

<正> 全球变暖问题已经是全世界关注的焦点,不仅各国科学家们进行了大量的研究,各国政府也耗费巨资组成了政府间专家组(IPCC,Intergovernmental panel on ClimateChange研究气候变化的影响。IPCC包括3个工作组,Ⅰ.科学分析工作组(Working     

THE INFLUENCE OF HUMAN BEING ON THE DESERTIFICATION OF ORDOS AND THE POSSIBLE COUNTERMEASURES IN THE FUTURE

<正> The Ordos Plateau is a unified geographical region demarcated by the Yellow River's elbow section on the north and the Great Wall on the south, administratively comprisingthe whole Ih-Ju League of Inner Mongolia, part of Yulin Prefecture of Shaanxi Province,and part of Yanchi County of Ningxia. The unique sandy and denuded landscape of the pla-     

巢湖市“五早”作物生产可持续发展的思考

针对巢湖市"五早"作物生产的实施成效和面临的形势与问题,从优质高产、市场流通、配套服务等多方面提出了可持续发展的"三大"转变措施.     

The use of herders’ accounts to map livestock activities across agropastoral landscapes in Semi-Arid Africa

Improved understandings of the agricultural and range ecologies ofsemi-arid Africa require better information on the spatiotemporal distributionof domestic livestock across agropastoral landscapes. An empirical GIS-basedapproach was developed for estimating distributions of herded livestock acrossthree agropastoral territories (around 100 km² each)over a two-year period. Algorithms developed from regression analyses of herdtracking data (with R²s 0.67) are used to transform a morecomprehensive but incomplete set of data generated from herders accounts oftheir herds grazing itineraries (400 herds following 6500 itineraries). Theresulting characterization registers 40 000 days of livestock activitiesacross694 land units (averaging 70 ha) over the study period. This studydemonstrates that rural producers knowledge of their daily extractionpracticescan be translated to fine-grained characterizations of extraction densitiesacross mixed landscapes. The spatiotemporal distribution of livestock that isrevealed by this approach diverges strongly from that predicted bycommonly-usedpoint-diffusion estimation procedures. Instead, the distribution reflects localpatterns of land use, topography, vegetation, settlements, and water points.Grazing and nongrazing times spent in land units are not spatially correlatedand the seasonality of grazing pressure is spatially variable. Therefore, theecological impacts of livestock grazing are spatially variable at fine scalesand there is a significant potential for livestock-mediated nutrient transfersacross agropastoral landscapes. The georeferenced data produced by thisapproachnot only will help evaluate the impact and sustainability of differentmanagement practices but also provides a strong empirical base for improvedspatial modeling of herded livestock.This revised version was published online in May 2005 with corrections to the Cover Date.     

Introduction

The realization of strategies for sustainable land use assumes specificresearch concepts from the local to the global scale (micro-, meso- andmacroscale). Therefore, landscape ecological science has to provideinvestigation methods for all these different scales. By combiningtop-down and bottom-up approaches in addition tocoupled GIS-model applications and traditional methods, the investigation oflandscape ecological structures and processes seems to be possible. Thepresented studies show this approach on examples of two study areas in EasternGermany: A watershed of 400 km² and an administrativedistrict of about 4000 km². The scale-specificapplicability of several models and methods were tested for theseinvestigations, and the validation of the calculated results are presented. Animportant outcome of the project should be the prevention of conflicts betweenagriculture, water management and soil, and water and nature conservation;based onrecommendations for land use variants with decreased pollutant loading withinagricultural areas. The scale specific investigations can be considered as abase for establishing sustainable land use.This revised version was published online in May 2005 with corrections to the Cover Date.     

紫花苜蓿品种比较试验

通过对26个紫花苜蓿（Medicago sativa）品种的生育期、株高、产量、越冬率等指标的试验比较，结果表明：公农一号、保丰、陇东、德福等几个品种的表现优于其他参试品种，适宜在辽西北风沙地地区推广种植。     

Prediction of multinomial probability of land use change using a bisection decomposition and logistic regression

Land use change is an important research area in landscape ecology and urban development. Prediction of land use change (urban development) provides critical information for making the right policies and management plans in order to maintain and improve ecosystem and city functions. Logistic regression is a widely used method to predict binomial probabilities of land use change when just two responses (change and no-change) are considered. However, in practice, more than two types of change are encountered and multinomial probabilities are therefore needed. The existing methods for predicting multinomial probabilities have limits in building multinomial probability models and are often based on improper assumptions. This is due to the lack of proper methodology and inadequate software. In this study, a procedure has been developed for building models to predict the multinomial probabilities of land use change and urban development. The foundation of this procedure consists of a special bisection decomposition system for the decomposition of multiple-class systems to bi-class systems, conditional probability inference, and logistic regression for binomial probability models. A case study of urban development has been conducted to evaluate this procedure. The evaluation results demonstrated that different samples and bisection decomposition systems led to very similar quality and performance in the developed multinomial probability models, which indicates the high stability of the proposed procedure for this case study.     

Neutral models for testing landscape hypotheses

Neutral landscape models were originally developed to test the hypothesis that human-induced fragmentation produces patterns distinctly different from those associated with random processes. Other uses for neutral models have become apparent, including the development and testing of landscape metrics to characterize landscape pattern. Although metric development proved to be significant, the focus on metrics obscured the need for iterative hypothesis testing fundamental to the advancement of the discipline. We present here an example of an alternative neutral model and hypothesis designed to relate the process of landscape change to observed landscape patterns. The methods and program, QRULE, are described and options for statistical testing outlined. The results show that human fragmentation of landscapes results in a non-random association of land-cover types that can be describe by simple statistical methods. Options for additional landscape studies are discussed and access to QRULE described in the hope that these methods will be employed to advance our understanding of the processes that affect the structure and function in human dominated landscapes.     

Linking Land-use, Water Body Type and Water Quality in Southern New Zealand

Land-use and vegetation cover have been linked to the nutrient levels (nitrogen, phosphorus) of surface waters in several countries. However, the links generally relate to streams and rivers, or to specific types of standing water, for example shallow lakes in a geologically defined region. We measured physical variables and nutrient chemistry of 45 water bodies representative of the wide range of lentic wetland environments (swamps, riverine wetlands, estuaries, reservoirs, shallow lakes, deep lakes) in Otago, New Zealand, and related these to catchment variables and land-use in order to assess the potential influence of catchment modification on water quality of these diverse wetlands. Catchment boundaries and land cover were derived from maps using ArcView GIS software. Our predictions that concentrations of nutrients and other components of water quality would correlate positively with the nature and intensity of catchment modification were confirmed in multivariate analyses. Physical and chemical measures were positively related to the extent of modification in the catchment (percentage of the catchment in pasture, planted forest, scrub and urban areas), and negatively related to lack of catchment modification (more of the catchment in bare ground, tussock grassland and indigenous forest). The strong negative correlations between nutrient concentrations, suspended sediment, water colour and the percentage of tussock cover in the catchment imply that increased conversion of the␣native tussock grassland to pastoral farming in␣Otago will increase nutrient concentrations and␣reduce water quality of the diverse lentic ecosystems.     

科尔沁沙地翁牛特旗气温的非对称变化分析

分析科尔沁沙地内蒙古翁牛特旗1957年以来逐月平均气温、平均最低气温、平均最高气温.结果表明:翁牛特旗近50年平均气温、日最高气温、日最低气温随时间均呈增加态势;日最低气温的增加量是日最高气温的11倍;1月最低气温的线性增加率为8.77 ℃/100 a,7月最高气温的线性增加率为3.12 ℃/100 a,其结果导致日较差减少;20世纪80年代后期年平均气温、日最高气温、日最低气温显著升高.