Does grassland introduction into cropping cycles affect carbon dynamics through changes of allocation of soil organic matter within aggregate fractions?

Implementation of ley grassland into crop rotation could have positive influence in soil ecosystem services such as C storage. The periodical changes of land-use plus the in situ labelling given by the introduction of maize crops under ley grassland induce differences in soil organic matter (SOM) that could be traced either by stable isotopes or by the characterization of plant biomarkers such as lignin derived phenols. Evaluation of SOM dynamics is often limited by the complexity of soil matrix. To override these limitations, a hierarchical approach to decompose the soil mosaic into aggregates has been proposed in this study. Soil and plant samples were collected from a long-term experimental area in Lusignan (western France). Soils from four different treatments (bare fallow, permanent maize, permanent grassland, and ley grassland based on 6years of grassland followed by 3years of maize) were sampled, fractionated into water stable aggregates, and finally analysed for carbon, nitrogen, and lignin contents, as well as for 13C isotopic signature. Soils under ley and permanent grassland stored higher amount of SOM in larger aggregates and preserved more efficiently the lignin stocks than the corresponding samples under permanent maize. Contemporary, finer fraction of ley grassland showed higher mean residence time of organic carbon, probably due to a legacy effect of the previous years under grassland. Even if maize derived SOM was identified, the grassland footprint was still dominating the ley grassland soils, as described by the principal component analysis. Strong correlation between these results and the quality and stoichiometry of the vegetal litter returned to soil were found, evidencing the needs for a comprehensive evaluation at a molecular level of all the parameters modified by land-use changes, including tillage, to understand the potential for carbon storage of different agroecosystems.

A nursing intervention to ensure a safe playground environment.

Unintentional injuries sustained on school playgrounds are a continual problem not only for children but also for the school nurses who are concerned with their safety. A group of school nurses organized by the local health department's pediatric nurse practitioner responded proactively to this problem by enlisting both school officials and students to accept joint responsibility for a safe play environment. The school nurses assisted the staff in providing a safe play environment and encouraged the students to behave in a safe and acceptable manner on the playground. The nurses developed (a) a Playground Safety Assessment Guide for the school staff to establish and maintain a safe play environment, (b) an in-service session for playground monitors to learn how to supervise children at recess, and (c) a student-oriented program for the children to improve behavior on the playground based on a program conceived by Utah State University (Daug & Fukui, 1988). School nurses and pediatric nurse practitioners can use this program as a model for other schools to improve the physical play environment and behavior of the children at recess.