Field history and dissipation of atrazine and metolachlor in Colorado

Farmers in eastern Colorado have commented that atrazine does not provide the length of weed control that they expected in fields that have received multiple applications of the herbicide. Multiple laboratory studies suggest that atrazine dissipates more rapidly in soils with a history of atrazine use compared with soils that had not been treated with the herbicide and this could be related to the above observation. Field and laboratory studies were conducted to determine the rate of dissipation of atrazine and metolachlor in fields in Colorado. The published half-lives of atrazine and metolachlor are 60 and 56 d, respectively. In the field studies, the half-lives of atrazine and metolachlor in the top 15 cm of the soil ranged between 3.5 and 7.2 d and 17.9 and 18.8 d, respectively. In laboratory studies, the half-life of atrazine varied from 1.4 to 19.8 d with the shortest half-life occurring in soils which had been treated with atrazine for at least 5 yr. The longest half-life was in a soil that had never received atrazine. The half-life of metolachlor in these same soils varied from 10.6 to 28.2 d. There was no apparent relationship between the half-life of metolachlor and the half-life of atrazine in the laboratory studies. These results confirm farmers' observation of the shorter residual activity of atrazine in Colorado fields receiving atrazine over multiple years.     

Assessing slope stability in unplanned settlements in developing countries

Unplanned housing in developing countries is often located on steep slopes. Frequently no building code is enforced for such housing and mains water is provided with no drainage provision. Both of these factors can be particularly significant in terms of landslide risk if, as is so often the case, such slopes lack any planned drainage provision. There is thus a need to develop a model that facilitates the assessment of slope stability in an holistic context, incorporating a wide range of factors (including surface cover, soil water topographic convergence, slope loading and point source water leakage) in order that appropriate advice can be given as to the general controls on slope stability in such circumstances. This paper outlines a model configured for this specific purpose and describes an application to a site in St. Lucia, West Indies, where there is active slope movement in an unplanned housing development on relatively steep topography. The model findings are in accord with the nature of the current failure at the site, provide guidance as to the significance of slope drainage and correspond to inferences drawn from an application of resistance envelope methods to the site. In being able to scenario test a uniquely wide range of combinations of factors, the model structure is shown to be highly valuable in assessing dominant slope stability process controls in such complex environments.     

Sampling and Mapping a Soil Erosion Cover Factor by Integrating Stratification,Model Updating and Cokriging with Images

Cost-efficient sample designs for collection of ground data and accurate mapping of variables are required to monitor natural resources and environmental and ecological systems. In this study, a sample design and mapping method was developed by integrating stratification, model updating, and cokriging with Landsat Thematic Mapper (TM) imagery. This method is based on the spatial autocorrelation of variables and the spatial cross-correlation among them. It can lead to sample designs with variable grid spacing, where sampling distances between plots vary depending on spatial variability of the variables from location to location. This has potential cost-efficiencies in terms of sample design and mapping. This method is also applicable for mapping in the case in which no ground data can be collected in some parts of a study area because of the high cost. The method was validated in a case study in which a ground and vegetation cover factor was sampled and mapped for monitoring soil erosion. The results showed that when the sample obtained with three strata using the developed method was used for sampling and mapping the cover factor, the sampling cost was greatly decreased, although the error of the map was slightly increased compared to that without stratification; that is, the sample cost-efficiency quantified by the product of cost and error was greatly increased. The increase of cost-efficiency was more obvious when the cover factor values of the plots within the no-significant-change stratum were updated by a model developed using the previous observations instead of remeasuring them in the field.     

Social entrepreneurship,co-production,and post-disaster recovery

Post-disaster recovery requires co-production; that is, the inputs of citizens are essential for successful community recovery to occur. Citizens contribute to post-disaster recovery by volunteering, taking on consultative and decision-making roles within their communities, and directly participating in post-disaster reconstruction efforts. Without meaning ful contributions from citizens—the intended beneficiaries—unilateral efforts by public officials and authorities will inevitably fail. This study shows that social entrepreneurs can thus play a critical role in spurring post-disaster recovery by facilitating co-production. It focuses on the role of social entrepreneurs after disasters and centres on one rural village, Giranchaur Namuna Basti in the Sindhupalchowk District of Nepal. Specifically, the study uses the case of the Dhurmus Suntali Foundation's Namuna village project in Giranchaur following the 7.8-magnitude earthquake that struck on 25 April 2015 to examine the pivotal role that social entrepreneurs assume in promoting voluntary activities, community engagement, and participation in post-disaster recovery efforts.     

Creating False Images: Stream Restoration in an Urban Setting

Stream restoration has become a multibillion dollar business with mixed results as to its efficacy. This case study utilizes pre‐ and post‐monitoring data from restoration projects on an urban stream to assess how well stream conditions, publicly stated project goals, and project implementation align. Our research confirms previous studies showing little communication among academic researchers and restoration practitioners as well as provides further evidence that restoration efforts tend to focus on small‐scale, specific sites without considering broader land use patterns. This study advances our understanding of restoration by documenting that although improving ecological conditions is a stated goal for restoration projects, the implemented measures are not always focused on those issues that are the most ecologically salient. What these projects have accomplished is to protect the built environment and promote positive public perception. We argue that these disconnects among publicized goals for restoration, the implemented features, and actual stream conditions may create a false image of what an ecologically stable stream looks like and therefore perpetuate a false sense of optimism about the feasibility of restoring urban streams.     

Assimilation of symbiont-derived photosynthates in some solitary and colonial radiolaria

Evidence for host assimilation of ¹⁴C-labeled symbiont photosynthates is presented from laboratory studies of the solitary radiolarian Thalassicolla nucleata and the colonial species Collosphaera huxleyi. The amount of ¹⁴C-labeled product assimilated in the central capsule of T. nucleata is directly related to the amount of ¹⁴C incorporated by the symbionts. In C. huxleyi central capsules, the percentage of ¹⁴C-label occurring in the water-soluble fraction is 38% and in the lipid-soluble fraction is 20%, the remainder being in insoluble products. Within the lipid-soluble fraction, a substantial percentage of the ¹⁴C activity is associated with the triglyceride and wax ester fractions. The significance of these findings is discussed in relation to the possible physiological role of symbionts in sustaining the host and stabilizing the host-symbiont association.