Soil property and management effects on grassland microbial communities across a latitudinal gradient in Germany

There is much interest in the identification of the main drivers controlling changes in the microbial community that may be related to sustainable land use. We examined the influence of soil properties and land-use intensity (N fertilization, mowing, grazing) on total phospholipid fatty acid (PLFA) biomass, microbial community composition (PLFA profiles) and activities of enzymes involved in the C, N, and P cycle. These relationships were examined in the topsoil of grasslands from three German regions (Schorfheide-Chorin (SCH), Hainich-Dun (HAI), Schwabische Alb (ALB)) with different parent material. Differences in soil properties explained 60% of variation in PLFA data and 81% of variation in enzyme activities across regions and land-use intensities. Degraded peat soils in the lowland areas of the SCH with high organic carbon (OC) concentrations and sand content contained lower PLFA biomass, lower concentrations of bacterial, fungal, and arbuscular mycorrhizal PLFAs, but greater enzyme activities, and specific enzyme activities (per unit microbial biomass) than mineral soils in the upland areas of the HAI and ALB, which are finer textured, drier, and have smaller OC concentrations. After extraction of variation that originated from large-scale differences among regions and differences in land-use intensities between plots, soil properties still explained a significant amount of variation in PLFA data (34%) and enzyme activities (60%). Total PLFA biomass and all enzyme activities were mainly related to OC concentration, while relative abundance of fungi and fungal to bacterial ratio were mainly related to soil moisture. Land-use intensity (LUI) significantly decreased the soil C:N ratio. There was no direct effect of LUI on total PLFA biomass, microbial community composition, N and P cycling enzyme activities independent of study region and soil properties. In contrast, the activities and specific activities of enzymes involved in the C cycle increased significantly with LUI independent of study region and soil properties, which can have impact on soil organic matter decomposition and nutrient cycling. Our findings demonstrate that microbial biomass and community composition as well as enzyme activities are more controlled by soil properties than by grassland management at the regional scale. (C) 2013 Elsevier B.V: All rights reserved.

Experimental Validation of Finite Element Analysis of Human Vertebral Collapse Under Large Compressive Strains

Osteoporosis-related vertebral fractures represent a major health problem in elderly populations. Such fractures can often only be diagnosed after a substantial deformation history of the vertebral body. Therefore, it remains a challenge for clinicians to distinguish between stable and progressive potentially harmful fractures. Accordingly, novel criteria for selection of the appropriate conservative or surgical treatment are urgently needed. Computer tomography-based finite element analysis is an increasingly accepted method to predict the quasi-static vertebral strength and to follow up this small strain property longitudinally in time. A recent development in constitutive modeling allows us to simulate strain localization and densification in trabecular bone under large compressive strains without mesh dependence. The aim of this work was to validate this recently developed constitutive model of trabecular bone for the prediction of strain localization and densification in the human vertebral body subjected to large compressive deformation. A custom-made stepwise loading device mounted in a high resolution peripheral computer tomography system was used to describe the progressive collapse of 13 human vertebrae under axial compression. Continuum finite element analyses of the 13 compression tests were realized and the zones of high volumetric strain were compared with the experiments. A fair qualitative correspondence of the strain localization zone between the experiment and finite element analysis was achieved in 9 out of 13 tests and significant correlations of the volumetric strains were obtained throughout the range of applied axial compression. Interestingly, the stepwise propagating localization zones in trabecular bone converged to the buckling locations in the cortical shell. While the adopted continuum finite element approach still suffers from several limitations, these encouraging preliminary results towardsthe prediction of extended vertebral collapse may help in assessing fracture stability in future work.

Large-scale land acquisitions in Peru: Land (re)-concentration, agrarian change and reactions from rural communities

More than 40 years after the agrarian reform, Peru is experiencing a renewed process of concentration of land ownership in the hands of large-scale investors, favoring the development of a sugar cane production cluster along the northern coast. The expansion of the agricultural frontier by means of large irrigation projects – originally developed to benefit medium- and small-scale farmers – is carried out today in order to be sold to large-scale investors for the production of export crops. In the region of Piura the increasing presence of large-scale biofuel investors puts substantial pressure on land and water resources, not only changing the use of and access to land for local communities, but also generating water shortages vis-à-vis the multiple water demands of local food producers. The changes in land relations and the agro-ecosystem, the altering food production regime as well as the increasing proletarization of smallholders, is driving many locals – even those which (initially) welcomed the investment – into resistance activities against the increasing control of land, water and other natural resources in the hands of agribusinesses. The aim of this presentation is to discuss the contemporary political, social and cultural dynamics of agrarian change along the northern Peruvian coast as well as the «reactions from below» emanating from campesino communities, landless laborers, brick producers, pastoralists as well as other marginalized groups. The different strategies, forms and practices of resistance with the goal of the «protection of the territory» shall be explored as well as the reasons for their rather scattered occurrence and the lack of alliances on the land issue. This input shall make a contribution to the on-going debate on individual and communal property rights and the question of what is best in terms of collective defense against land grabbing.