阿克苏地区农业生态系统的物质与能量流动

以阿克苏地区为对象研究了该区农业生态系统中能量流动和物质循环的一般特征。结果显示,在能流方面,阿克苏地区农田生态系统的能量产出水平和效率都处于较低水平;在物流方面,农田肥料投入单一,主要以化肥为主,并且化肥使用量已超出最适施肥量范围,造成土壤养分严重失衡。今后应改善投能结构,优化种植业结构,促进系统持续、稳定、高效的发展。     

Habitat relations of Rhea americana in an agroecosystem of Buenos Aires Province, Argentina

The maintenance of wild populations of Greater Rhea (Rhea americana) through effective management requires an understanding of their habitat requirements in terms of vegetation composition and field configuration. We studied the relative influence of some anthropogenic variables (presence of route, house and fences) and resource variables (presence of water source, composition and coverage of plant species, vegetation height and bare soil), on the habitat use by a population of rheas in a cattle ranch of Buenos Aires Province, Argentina. Habitat use was determined indirectly by documenting the number of faeces in summer, autumn-winter and spring 1999. The presence or absence of faeces was related to the measured variables through discriminant analysis that allowed the elaboration of predictive models of habitat use by this species. Contrary to what was expected, those variables related to human activity showed a low predictive value on the habitat use by rheas when compared with resource variables. Rheas preferentially selected the stream area in all seasons and sites with great percent cover of Bupleurum sp., Phyla canescens, Sida leprosa, Plantago lanceolata, Trifolium repens, Lolium multiflorum, Stipa spp., and Stenotaphrum secundatum. Low vegetation height was another important component of rhea's habitat in summer and autumn-winter. The high accuracy level obtained by validation tests of this model supports its utility for the management of rhea populations in other cattle ranches of the region, and to analyze the suitability of other ranches for reintroduction programs.     

太行山前平原高产区典型农业生态系统数量特征和持续发展对策

本文选取太行山前平原高产区具有一定代表性的聂家庄农业生态系统为典型研究对象，从分析系统能物流数量特征入手，对资源转化效率和资源持续支持力进行了深入探讨，在剖析系统结构功能存在的薄弱环节和问题的基础上，提出了系统持续发展的主要对策。     

农业生态系统健康及其管理研究进展

生态系统健康是生态系统管理的目标。阐述了农业生态系统健康的概念、评价指标和评价方法,指出农业生态系统健康评价指标与标准的选择应根据其结构和功能将社会经济指标及资源环境指标有机结合,以客观评价农业环境资源承载力及农业生产发展方向,并科学管理农业生态系统。     

Cropping Systems and Integrated Pest Management: Examples from Selected Crops

SUMMARY

Cropping systems have been central to managing associated pests for centuries. This treatment focuses on the history, concepts, and the integration of available Integrated Pest Management (IPM) tools/strategies into cropping systems. Pest assessments/diagnoses, IPM-decision-making aids, and examples of pest management in selected crops/cropping systems (wheat, soybean, corn, cotton, potato, and strawberry) as well as emerging opportunities and challenges are discussed. The evolving philosophy of IPM and the recently renewed emphasis on ecologically based pest management address the fact that significant levels of predation and/or parasitism are desirable insofar as they promote diversity and sustainability of agroecosystems. Thus, cropping systems are beginning to focus on soil and crop health as well as specific IPM and production goals. Although extensive efforts have been directed toward modeling the many interactions between crops, associated pests and the environment, the general implementation of a systems approach to integrated crop and pest management remains to be accomplished.     

Redesigning Industrial Agroecosystems

Summary

The development and mixed benefits of high-input industrial agriculture are reviewed, then illustrated with findings from a Georgia landscape study. As a basis for considering ways to reduce the serious negative aspects of industrial agriculture, we compared the basic ecological energetics and processes of natural ecosystems with pre-industrial, industrial, and reduced-input conservation tillage agroecosystems. We also reviewed our 20-year comparison of conventional tillage with no-till systems. The conclusion is that current trends to redesign industrial agriculture along the lines of reduced-input conservation tillage systems should be accelerated in order to maintain and restore soil quality, and to reduce pollution and soil erosion at the landscape scale.     

驸马庄复合农业生态系统功能的评价

本文对地处北亚热带丘陵的驸马庄村以土地持续利用为目标的复合农业生态系统进行了综合的功能评价。系统的总体生产特性以粮食生产及农业总产值的持续性、稳定性为定量指标，以协调性（多样性）作为农业各部门协调发展的指标，较满意地反映了实际情况。对系统的能量、氮、磷、钾养分及资金的投入产出分析表明以上各项要素的总流通量在近10年中都有较大增长，系统的开放度相应提高。农田亚系统的光能利用率提高，能量产投比下降。磷、钾的产投比远大于1，导致土壤磷、钾的严重亏缺。畜牧亚系统各项效率明显增长。土地的人口负载力在动物产品大幅度增长条件下，从每公顷13.8人提高至15.5人，食物生产能力可负载两倍于现有的人口。     

信息技术:走向农业生态系统的可持续管理

21世纪信息科学及其工程技术将加速生态学、分子生物学等现代生物科学的两个前沿学科及其工程技术的发展，在解决人类生存的环境问题和探寻生命本原问题中起推波助澜作用。农业的终极目标是实现对农业生态系统的可持续管理，现代信息工程技术是实现这个目标的核心技术，其中地理信息系统（GIS）、全球定位系统（GPS）和遥感（RS）等3S技术为实现农业生态系统的可持续管理提供了综合的、多维的、动态的，因而也是通晓的和精确的信息资源和技术控制方案，将促进农业真正通向可持续发展之路。     

The influence of field shape, area and surrounding landscape on plant species richness in grazed ex-fields

Over the past 100 years species-rich semi-natural grasslands have decreased dramatically in Western Europe, where former arable fields (ex-fields) are used instead as pasture. The disappearance of semi-natural grasslands has caused a threat to the biodiversity in agricultural landscapes. Many typical grassland plants are dispersal limited, thus grazed ex-fields can be used to investigate if species spontaneously colonise these new grassland habitats. We examined the relationship between surrounding landscape, field area, shape, distance between edge and centre, and plant species diversity in ex-fields that had been grazed for 15-18 years. The results showed that there were 35% more plant species in fields surrounded by commercial forestry production compared to those surrounded by open agricultural landscape. Area and shape did not influence species richness, although there was increasing number of species in the centre with decreasing distance from the edge. Twenty-five percent of the species where typical grassland species, and ex-fields surrounded by forest had 91% more grassland species compared to those in the open landscape. It is possible to increase grassland plant occurrences by grazing ex-fields surrounded by forest or other grassland remnant habitats, particularly in landscapes where grazed semi-natural grasslands are scarce.     

Floristic structure and sequestration potential of cashew agroecosystems in Africa: A case study from Cameroon

Agroecosystems are not only recognized by their high capacity of carbon storage and sequestration, they could also offer an opportunity of financial benefits in the event of payment for environmental services. The present study aimed to evaluate the carbon storage and describe the structure of cashew nut plantation. Three types of cashew stand were selected according to the age of plantations; we also used savannah as a treatment witness. Carbon stocks varied according to the age of plantations; 14.51 ± 0.306 t C/ha for plantations aged 0–10 yr; 34.78 ± 0.331 t C/ha for plantations aged 10–20 yr, and 40.02 ± 0.381 t C/ha for plantations aged over 20 yr. In the witness, we found 13.05 ± 0.177 t C/ha. These values were significantly different between the studied sites (p < 0.05). The mean values of the service of carbon sequestration also varied with the age of stands; $53.5/ha/yr (0–10 yr); $63.35/ha/yr (10–20 yr); $73.95/ha/yr (over 20 yr). In regard to carbon storage, $3279 are stored in these stands. These agroecosystems are also true carbon sinks. A development plan of such agroecosystems should be considered for the conservation of the species already endangered by anthropogenic activities on natural ecosystems.