A comparison of land-sharing and land-sparing strategies for plant richness conservation in agricultural landscapes

Strategies for conserving plant diversity in agroecosystems generally focus on either expanding land area in non-crop habitat or enhancing diversity within crop fields through changes in within-field management practices. In this study, we compare effects on landscape-scale species richness from such land-sharing or land-sparing strategies. We collected data in arable field, grassland, pasture, and forest habitat types (1.6 ha sampled per habitat type) across a 100-km2 region of farmland in Lancaster County, Pennsylvania, USA. We fitted species-area relationships (SARs) for each habitat type and then combined extrapolations from the curves with estimates of community overlap to estimate richness in a 314.5-ha landscape. We then modified these baseline estimates by adjusting parameters in the SAR models to compare potential effects of land-sharing and land-sparing conservation practices on landscape richness. We found that species richness of the habitat types showed a strong inverse relationship to the relative land area of each type in the region, with 89 species in arable fields (66.5% of total land area), 153 in pastures (6.7%), 196 in forests (5.2%), and 213 in grasslands (2.9%). Relative to the baseline scenario, major changes in the richness of arable fields produced gains in landscape-scale richness comparable to a conversion of 3.1% of arable field area into grassland habitat. Sensitivity analysis of our model indicated that relative gains from land sparing would be greatest in landscapes with a low amount of non-crop habitat in the baseline scenario, but that in more complex landscapes land sharing would provide greater gains. These results indicate that the majority of plant species in agroecosystems are found in small fragments of non-crop habitat and suggest that, especially in landscapes with little non-crop habitat, richness can be more readily conserved through land-sparing approaches.     

The rate of degradation of 1,1,1-trichloroethane in water by hydrolysis and dehydrochlorination

Degradation of 1,1,1-trichloroethane in water by hydrolysis and dehydrochlorination may conceivably be a significant sink for this compound in the environment. The kinetics of these reactions have therefore been investigated over a wide range of temperature. The half-life at 20 °C is found to be 1.7 years.     

Forced dispersal of juvenile guanacos (<Emphasis Type="Italic">Lama guanicoe</Emphasis>): causes,variation, and fates of individuals dispersing at different times

We examined adult-juvenile conflict in the guanaco (Lama guanicoe). During spring, territorial males become increasingly aggressive toward all juveniles born the previous year and begin expelling them from family groups. In an apparent effort to reduce aggression, juveniles display submissive crouches when being observed, approached, or attacked by the territorial male. Therefore, we assessed the influence of juvenile submissive behavior on the timing of dispersal and also examined if dispersal time was related to survival and reproductive performance as adults. We also evaluated hypotheses regarding the evolution of juvenile mammalian dispersal in the context of if and how each may favor the forced dispersal of juvenile guanacos by territorial males. Juveniles generally dispersed in late spring and early summer, and a nearly equal proportion of females (n=46; 48%) and males (n=49; 52%) dispersed. More-submissive animals generally dispersed later than less-submissive animals. Juvenile sex and dispersal time were not related to survival. In contrast, juvenile sex and dispersal time were related to reproductive performance. The probability of reproducing was highest when juveniles dispersed early and decreased with increasing time in family groups prior to dispersal. The largest proportion of juveniles was forced to disperse during a 2-week interval following the peak of the breeding season. Competition for food resources is likely very intense at this juncture and territorial males may force older juveniles to disperse in order to divert food resources to younger neonates. Additionally, juveniles may be forced to disperse after territorial males mate their mothers to prevent lost mating opportunities, because females leave territories when their offspring disperse and possibly prior to mating with males. We conclude that the forced dispersal of juvenile guanacos by territorial males is ultimately driven by competition for food resources on territories. The timing of dispersal, however, may be tempered by the chronology of matings between territorial males and particular adult females, and/or genetic relatedness between territorial males and juveniles.     

Assessment of groundwater quality in a region of endemic fluorosis in the northeast of Brazil

The aim of this study was to estimate the risk for caries and fluorosis in a desertification area, applying the calcium/fluoride concentration ratio of underground water and the quality of water in a selected geographical region. This study was performed in the municipality of São João do Rio do Peixe, located in the tropical semiarid lands of Brazil. A total of 111 groundwater samples were collected. Fluoride concentration varied from 0.11 to 9.33 mg/L. Thirty percent of all samples analyzed showed values above 1.5 mg/L, while 64 % were above the ideal limit of 0.7 mg/L. Mean calcium concentration was 47.6 mg/L, and 14.4 % of all samples presented values above the WHO acceptable limits. The proportional value of calcium/fluoride in water showed that only 12 % of the samples were suitable for dental caries prevention with minimal risk for dental fluorosis. Mapping of the fluoride distribution indicated that approximately 2,465 people could be affected by dental fluorosis and 1,057 people might be affected by skeletal fluorosis. It can be concluded that, in addition to fluoride, many water parameters were not suitable for the drinking water. Mapping out calcium/fluoride ratio may indicate areas of water suitability for caries control, whereas the fluoride concentration solely can indicate the areas with the risk for fluorosis. This approach can be relevant for health authorities for identifying communities where dental caries or dental fluorosis is prevalent.     

Effects of H2O2 on growth,metabolic activity and membrane integrity in three strains of Microcystis aeruginosa

Environmental Science and Pollution Research - The application of hydrogen peroxide (H2O2) as a management tool to control Microcystis blooms has become increasingly popular due to its short...     

An approach to partition the anthropogenic and natural components of heavy metal accumulations in roadside agricultural soil

This paper describes a new approach that allows us to partition the anthropogenic and natural contributions to heavy metal accumulations in roadside agricultural soils. This approach, combining trend analysis and multivariate statistical analysis, partitions total heavy metals into three components: anthropogenic, natural, and unexplained residual. The approach was applied in a case study in Yixing City, China, to determine the spatial distributions of heavy metal accumulations. The results show that anthropogenic components of Pb, Cu, Zn, and Cd account for 52.4%, 23.04%, 5.09%, and 10.9% of total content, respectively. Spatial distributions of anthropogenic components are characterized by decreasing accumulation with increasing distance from the road. Ranges of influence of traffic for Pb, Cu, and Cd are beyond 300 m, whereas the range of Zn is less than 200 m. The spatial distributions of the four elements?? natural components show relatively similar distribution patterns. Assessments of variable partition methods show that the predicted values of Pb, Cu, Zn, and Cd are consistent with their measured values. The anthropogenic components extracted from total contents of heavy metal will be useful for modeling heavy metal accumulations produced by human activities.