"超级杂草"伴随着转基因作物而出现

最初的转基因大豆被基因工程业誉为“万金油”。它们能够在有除草剂的环境下生长，从理论上说，这将导致田地里那些不受欢迎的植物(比如杂草)的末日。这也将减少种植费用和除草剂的使用量。然而，多年来转基因技术的反对者们的预言现在已经变成了事实：随着时间的推移，“杂草”与转基因植物一样也具备了耐除草剂的特性。这便意味着必须应用其它除草剂，带来更多的花费。     

High-temperature tolerance of photosynthesis in the red alga Chondrus crispus

Chondrus crispus (Stackhouse) is a perennial red seaweed, common in intertidal and shallow sublittoral communities throughout the North Atlantic Ocean. In the intertidal zone, C. crispus may experience rapid temperature changes of 10 to 20C° during a single immerison-emerision cycle, and may be exposed to temperatures that exceed the thermal limits for long-term survival. C. crispus collected year-round at Long Cove Point, Chamberlain, Maine, USA, during 1989 and 1990, underwent phenotypic acclimation to growth temperature in the laboratory. This phenotypic acclimation enhanced its ability to withstand brief exposure to extreme temperature. Plants grown at summer seawater temperature (20°C) were able to maintain constant rates of lightsaturated photosynthesis at 30°C for 9 h. In contrast, light-saturated photosynthetic rates of plants grown at winter seawater temperature (5°C) declined rapidly following exposure to 30°C, reached 20 to 25% of initial values within 10 min, and then remained constant at this level for 9 h. The degree of inhibition of photosynthesis at 30°C was also dependent upon light intensity. Inhibition was greatest in plants exposed to 30°C in darkness or high light (600 mol photons m^-2s^-1) than in plants maintained under moderate light levels (70 to 100 mol photons m^-2s^-1). Photosynthesis of 20°C-acclimated plants was inhibited by exposure to 30°C in darkness or high light, but the degree of inhibition was less than that exhibited by 5°C-grown plants. Not only was light-saturated photosynthesis of 20°C plants less severely inhibited by exposure to 30°C than that of 5°C plants, but the former also recovered faster when they were returned to growth conditions. The mechanistic basis of this acclimation to growth temperature is not clear. Our results indicate that there were no differences between 5 and 20°C-grown plants in the thermal stability of respiration, electron transport associated with Photosystems I or II, Rubisco or energy transfer between the phycobilisomes and Photosystem II. Overall, our results suggest that phenotypic acclimation to seawater temperature allows plants to tolerate higher temperatures, and may play an important role in the success of C. crispus in the intertidal environment.     

A MULTI-TIER APPROACH FOR AGRICULTURAL WATERSHED MANAGEMENT1

A multi-tier approach for agricultural watershed management has been proposed. The approach involves identification of a watershed management issue/problem, selection or development of simple conceptual model suitable for the exploration of the issue/problem identified and appropriate to the database available, and application of the model the address the identified issue/problem. The procedure is repeated by increasing the complexity in the conceptual model until the identified issue/problem has been addressed satisfactorily. An application of the procedure to an example watershed in southern Ontario conditions is shown. The application example has revealed that for identification of temporal pattern of runoff and sediment loads a simple conceptual model is adequate. For identification of spatial location of the sediment source areas and for the development of a monitoring program for the evaluation of remedial strategies a more complex distributed agricultural watershed model is necessary.     

Micronutrient deficiencies in maternity and child health: a review of environmental and social context and implications for Malawi

It is well documented that micronutrient malnutrition is of increasing concern in the developing world, resulting in poor health and high rates of mortality and morbidity. During pregnancy, deficiency of iron and zinc can produce cognitive and growth impairment of the foetus, which may continue into infancy. Iron and zinc are essential micronutrients for both plant growth and human nutrition. Despite significant work in the areas of soil fertility, crop biofortification and dietary interventions, the problems of micronutrient deficiencies persist in Africa. There is a need to examine why communities have not embraced intervention strategies which may offer health benefits. Bottom-up, interdisciplinary approaches are required to effectively study the relationships between local communities and their environment, and to assess the impact their behaviour has on the cycling of micronutrients within the soil–plant–human system. From a detailed consideration of diverse influencing factors, a methodological model is suggested for studying the barriers to improving micronutrient uptake within rural communities. It combines environmental understanding with health and social factors, emphasising the need for and potential benefits of understanding and coherence in true interdisciplinary working.     

Realizing the potential of GIS in community-based management of protected areas

SUMMARY

This paper explores the roles GIS technology can play in support of land management, focusing in particular on its application in protected environments such as Biosphere Reserves. These ecologically significant areas present complex planning situations since, unlike areas set aside solely for conservation, they must continue to support human populations that depend on natural resources for their economic and social well being. In situations such as marginal tropical locations, land managers often face major economic and political disincentives to the conservation of precious natural resources. The necessity for community participation and local expertise in the planning process becomes increasingly critical as GIS evolves from a basic presentation aid for spatial data to a synthesizing problem-solving tool. Coupled with enhanced community participation is the opportunity for greater education of stakeholders; the potential for GIS to serve as a medium for information gathering and dissemination is discussed. A case study in the Sierra de Manantlán Biosphere Reserve (SMBR), México, is presented.     

SELECTION OF APPROPRIATE EVAPORATION ESTIMATION TECHNIQUE FOR CONTINUOUS MODELING1

ABSTRACT: The importance of evaporation in hydrologic modeling has been investigated by analysis of water budget at various scales and application of a water management model at plot scale. The data at all scales indicate that evaporation constitutes a major hydrological output. Accurate determination of watershed evapotranspiration depends upon appropriate accounting for the various components of evapotranspiration and their areal and temporal variability. An application of a water management model has revealed that the ranking of the sensitivity of input parameters depends upon the method of determination of evapotranspiration.     

Natural History Traits Associated with Detecting Mortality Within Residential Bird Communities: Can Citizen Science Provide Insights?

Cat predation of birds in residential landscapes is ephemeral, unpredictable, and spatially dispersed, and thus requires many person-hours to observe. We sought to identify whether specific behaviors, traits, or feeding ecologies of birds contribute to their probability of cat-caused mortality around residences across temperate North America. In addressing this question, we evaluated citizen science data with respect to peer-reviewed species accounts (Birds of North America, BNA). Using information on cat predation from the BNA, we found that species that glean their prey from the ground or breed in nest boxes were three times more likely to be depredated by cats, while birds that hawk were over two times less likely to become cat prey than would be predicted by random chance. Data from citizen science sources also showed that birds using nest boxes had increased susceptibility to cat predation, as did those that use feeders and that glean from foliage. We caution that observations of predation by citizen science volunteers may be biased towards detection at feeders. Future research should focus on developing volunteer survey techniques for improving estimates of bird mortality rates and sources.     

Mobility of metals and metalloids in a multi-element contaminated soil 20 years after cessation of the pollution source activity

Knowledge of trace element concentrations and mobility is important in the ecotoxicological assessment of contaminated soils. We analysed soil pore water under field conditions to provide new insights into the mobility of residual contaminants in the surface 50cm of a highly contaminated woodland soil. Cadmium and Zn were highly mobile in the acidic soil, concentrations increasing with depth in soil pore water, showing considerable downward mobility. High levels of surface organic matter restricted the solubility of Cu, Pb and Sb, with highest concentrations being found close to the surface. Dissolved organic carbon in pore water had a strong influence on mobility of Cu, Zn, Pb and Sb. Elevated As had moved from the organic surface horizons but was largely immobilised in deeper layers and associated with Fe and Al oxides. The measured differential mobility of pollutants in the present study is highly relevant to protection of groundwater and other receptors.     

Building disaster resilience using social messaging networks: the WeChat community in Houston,Texas, during Hurricane Harvey

Analyses of disaster resilience have focused increasingly on the role of social capital and online social networks in recovery. This study complements this field of work by investigating three key issues. First, it examines how a social messaging application, WeChat, helped individuals to access and to mobilise three types of social capital—bonding, bridging, and linking—during Hurricane Harvey, a Category 4 storm that made landfall in Louisiana and Texas in the United States in August 2017, resulting in significant flooding and loss of life. Second, it pinpoints and assesses quantitatively how individuals' WeChat group usage and social capital influenced their post-disaster well-being. Third, it demonstrates how a minority and immigrant community in Houston, Texas, overcame the disadvantages commonly observed in other disaster research through the utilisation of social media. The findings of this study should aid governmental and community efforts to foster resilience in the face of natural and human-induced hazards.