How does agricultural intensification modulate changes in plant community composition?

Agricultural intensification, at local and landscape scales, has caused a decrease in plant diversity and changes in species composition in cereal fields. To better understand the role of landscape complexity and farming systems in shaping plant assemblages, it is of interest to focus on functional traits rather than on floristic composition, which may help to highlight trends in vegetation patterns. We analysed the relative abundance of various functional attributes (different life forms, growth forms, wind-pollinated species and wind-dispersed species) at three contrasted field positions (boundary, edge and centre) of 29 organic and 29 conventional cereal fields distributed in 15 agrarian localities of NE Spain. Agricultural intensification affected the biological attributes of the vegetation in dryland Mediterranean cereal fields; local factors (farming system and position) had a more prominent role in affecting plant functional composition than the surrounding landscape. Local factors were important for life form distribution, growth form and pollination type, whereas landscape complexity mainly affected the proportion of wind-dispersed species. Therefore, depending on the objective of the study, it is important to select functional attributes sensitive to the different scales of agricultural intensification, especially because landscape complexity and land-use intensity are commonly related.     

利用农业土壤固定有机碳——缓解全球变暖与提高土壤生产力

大气CO     

Understanding the Scope of Farmer Perceptions of Risk: Considering Farmer Opinions on the Use of Genetically Modified (GM) Crops as a Stakeholder Voice in Policy

In the beginning, policy debates between critics and advocates of genetically modified (GM) crops focused on scientifically determined risks. Ten years later, the argument between environmentalists or consumers and regulators or industry has changed into a discussion about the implementation of more democratic policymaking about GM farming. A notable omission from the political debate about food biotechnology in the United States, however, is the opinion of farmers who cultivate the GM crops. Policymakers should value practical knowledge based on experiences from farmers, not only scientific industry reports or consumer product opinions. This project uses in-depth interviews to create an original mail survey that uses the practical discourse of farmers in order to explore the relationship of farmer attitudes and GM agriculture. Although national research indicates that larger yields are the most common reason for GM adoption, qualitative information suggest that the potential of GM crops to increase revenue per acre does not truly reflect all the concerns of modern farmers. For example, farmers who use GM seeds indicate that they constantly question the social impacts of their agricultural practices. As such, GM policies should be restructured as a political rationalization of both economic modeling and political theory because this research suggests that farmers’ business decisions are utility calucations that consider economics without ignoring environmental and political contexts. Farmers’ concerns about non-economic risks suggest that they need more information about GM crops and that governmental policies should respond to their interests, as they are more democratic or pluralistic than industry or consumer arguments.     

Combination of multispectral remote sensing, variable rate technology and environmental modeling for citrus pest management

The Lower Rio Grande Valley (LRGV) of south Texas is an agriculturally rich area supporting intensive production of vegetables, fruits, grain sorghum, and cotton. Modern agricultural practices involve the combined use of irrigation with the application of large amounts of agrochemicals to maximize crop yields. Intensive agricultural activities in past decades might have caused potential contamination of soil, surface water, and groundwater due to leaching of pesticides in the vadose zone. In an effort to promote precision farming in citrus production, this paper aims at developing an airborne multispectral technique for identifying tree health problems in a citrus grove that can be combined with variable rate technology (VRT) for required pesticide application and environmental modeling for assessment of pollution prevention. An unsupervised linear unmixing method was applied to classify the image for the grove and quantify the symptom severity for appropriate infection control. The PRZM-3 model was used to estimate environmental impacts that contribute to nonpoint source pollution with and without the use of multispectral remote sensing and VRT. Research findings using site-specific environmental assessment clearly indicate that combination of remote sensing and VRT may result in benefit to the environment by reducing the nonpoint source pollution by 92.15%. Overall, this study demonstrates the potential of precision farming for citrus production in the nexus of industrial ecology and agricultural sustainability.     

Systems In Organic Dairy Production

The aim of this study was to explore stakeholder perceptions of the contribution of an Automatic Milking System (AMS) to sustainable development of organic dairy production in Denmark and the Netherlands. In addition, reasons for the current difference in AMS use on organic dairy farms between both countries were explored. To answer above mentioned aims, farmers and advisors in both countries were interviewed using a focus group approach. Questions of the interviews were based on a literature review on sustainability issues affected by introduction of AMS. Participants expressed no moral problems regarding AMS use. They, however, pointed out uncertainty about the economic gain, difficulties with grazing, adaptation problems to technology, and image problems towards consumers. The latter results from a reduction in grazing time affecting both animal welfare and product quality. The participants did not recognize eutrophication, as result of high stocking density on farmstead lots, as a problem caused by AMS. The milk quality problem related to AMS use, although acknowledged as crucial towards consumers, was not prioritized very highly, especially not by the farmers in both countries. All groups were, however, unanimous in their perception of how important image was as far as the consumers are concerned. The perception analysis revealed that Dutch participants were more concerned about the economic payoff of AMS use, and showed more reluctance towards enlargement than Danish ones. In addition, they acknowledged the small-scale naturalness of organic production. These differences in perception could possibly explain observed differences in AMS use in organic dairy production between Denmark and the Netherlands.     

城郊稻田生态系统高效生产模式的研究与评价

根据天津市宝坻区的自然条件、区位优势和现有的农业种植结构,提出了稻藕轮作与稻鱼蟹混养相结合的高效生产模式并分析其生态优势。借助Ecopath软件,从系统可持续性和净产值角度,比较分析了稻鱼蟹混养与稻藕轮作相结合生产模式与稻田养鱼、稻田养蟹、稻鱼蟹混养、单一种稻4种稻田生产模式的优劣。结果表明:5种稻田生产模式F inn′s指数值从大到小依次为稻鱼蟹混养与稻藕轮作相结合、稻田养鱼、稻田养蟹、稻鱼蟹混养和单一种稻;稻鱼蟹混养与稻藕轮作相结合生产模式的可持续性指标优于其他3种生态种植模式,其净生产力、生物量/输出量、输出量/输入量和稳定性指标分别是单一种稻模式的2.63、4.25、2.03和3.56倍;与其他4种稻田生产模式相比,稻鱼蟹混养与稻藕轮作相结合模式的净产值很高,是适合于在北方推广的最优生态种植模式。     

不同栽培模式下耕层土壤盐分演变规律研究

通过定位试验对有机栽培、无公害栽培和常规栽培模式下土壤盐分动态进行了研究。结果表明,有机栽培和无公害栽培模式中土壤盐分差异不显著,常规与无公害栽培模式中土壤盐分差异显著(F0.05=9.04),常规与有机栽培模式下的土壤盐分差异也极显著(F0.01=9.37)。常规栽培与无公害栽培环境中,全年土壤全盐量变化表现为两个积盐期:春季和秋季,以春季积盐最明显;有机栽培环境中,从7月份即出现了积盐过程,并且土壤全盐量变化趋势与气温变化基本一致。     

骆马湖水体氮污染特征分析

通过对骆马湖2005年水质监测,并结合近几年的监测资料,对结果进行了分析。结果表明,氮是骆马湖水体的主要污染指标之一,主要是总氮、氨氮和硝酸盐氮污染,其主要污染特征是入湖河流、降水、围网养殖和点源带来的污染。针对实际提出了骆马湖整治的建议。     

黄土高原主要农作物水分盈亏与雨养农业问题

黄土高原在气候上属亚湿润向半干旱的过渡地区。水分缺乏是农业生产的重要限制因素。本文围绕降水和蒸发,主要作物的需水和降水间的相互关系,农田干湿状况和水分盈亏额进行了分析讨论。认为,发展雨养农业应该是黄土高原农业生产的一条基本方针;在雨养农业作物的选择上,除谷子可以在全区种植外,其他作物受地区局限性很大;发挥雨养农业生产潜力的基本途径应该是增加土壤水分含量和提高土壤有效水分的利用系数,为达到这一目的宜采用平整土地、增施肥料等一系列农业措施。     

Complexity,continuity and change: livelihood resilience in the Darfur region of Sudan

Darfur farming and pastoralist livelihoods are both adaptations to the environmental variability that characterises the region. This article describes this adaptation and the longer‐term transformation of these specialised livelihoods from the perspective of local communities. Over several decades farmers and herders have experienced a continuous stream of climate, conflict and other shocks, which, combined with wider processes of change, have transformed livelihoods and undermined livelihood institutions. Their well‐rehearsed specialist strategies are now combined with new strategies to cope. These responses help people get by in the short term but risk antagonising not only their specialist strategies but also those of others. A combination of factors has undermined the former integration between farming and pastoralism and their livelihood institutions. Efforts to build resilience in similar contexts must take a long‐term view of livelihood adaptation as a specialisation, and consider the implications of new strategies for the continuity and integration of livelihood specialisations.