Deriving hillslope sediment budgets in wildfire-affected forests using fallout radionuclide tracers

Information on post-fire sediment and nutrient redistribution is required to underpin post-fire catchment management decisions. Fallout radionuclide budgets (²¹⁰Pb_xs, ¹³⁷Cs and ⁷Be) were derived to quantify soil redistribution and sediment yield in forested terrain following a moderately severe wildfire in a small (89 ha) water supply catchment in SE Australia. Application of these techniques in burnt terrain requires careful consideration of the partitioning of radionuclides between organic and mineral soil components. Beryllium-7 and ²¹⁰Pb_xs were shown to be closely associated with ash, litter and soil organic matter whereas ¹³⁷Cs was more closely associated with subsurface coarse mineral soil. Comparison of the three tracer budgets indicated that the dominant sediment source areas were ridgetops and steep valley sideslopes, from which burnt surface material was conveyed to the stream network via pre-existing gullies. Erosion was predominantly driven by sheetwash, enhanced by soil water repellency, and modified by bioturbation which both supplies subsurface sediment and provides sinks for erosive overland flow. Footslope and riparian zones were not important sediment source areas. The estimated event-based (wildfire and subsequent rainfall) sediment yield is 58 ± 25 t km^− 2, based on fallout ⁷Be measurements. The upper estimate of total particulate phosphorus yield (0.70 kg ha^− 1) is more than 10 times that at equivalent unburnt sites. This illustrates that, soon after fire, burnt eucalypt forest can produce nutrient loads similar to those of agricultural catchments. The tracer budgets indicate that wildfire is an important control on sediment and phosphorus inputs to the stream network over the decadal timeframe and the pulsed nature of this release is an important concern for water quality management.     

Accommodation of ecological and economic interests in placer gold mining

An attempt is made to find the answer to the question as to why the measures of the environmental institutions of Russia are ineffective for the avoidance and prevention of the degradation of aquatic ecosystems in placer gold mining. It is established that the size of payments to be made by companies engaged in placer gold mining are such that they almost cannot stimulate any nature conservation initiatives. Moreover, they even cannot be the argument for observance of environmental legislation. It is shown that the high transaction costs borne by the State, with minor expenditures of nature resource users connected with the protection of environmental natural systems fail to achieve the objectives imposed upon the supervising institutions. It is established that local authorities are directly interested in increasing placer gold mining as well as in gaining the loyalty of artels implying registration of the enterprise in this region, because these tax proceeds are exceptionally important for municipal formations facing a chronic financial deficit, a budgetary uncertainty and a dependence on regional and federal subsidies and transfers. Finance flows were calculated and analyzed to show that a very important problem for Russia’s eastern regions that involves reconciling the economic and ecological interests in placer gold mining is not resolved through “cosmetic changes” in organs of state supervision. It is concluded that there is a need for new institutional solutions in order to create and increase incentives for users of mineral resources and local authorities for observance of environmental regulations, the preservation and restoration of disturbed ecosystems, and for the ecologization of production processes.     

A spatial analysis of factors relating to family planning in Thailand

This paper focuses on whether there is an organized structural pattern in the spatial distribution of oral contraceptive usage in rural Thailand and, if so, how this spatial pattern is linked to other related socioeconomic variables. The data concern the year 1975. The results suggest that the location of the health services infrastructure seems to have the most significant effect on the differences in level of oral contraceptive use observed.     

Listric extensional fault systems - results of analogue model experiments

Abstract Analogue models are a powerful tool for investigating progressive deformation in extensional fault systems. This paper presents exciting new insights into the progressive evolution of hanging wall structures in listric extensional terranes. Analogue models, scaled to simulate deformation in a sedimentary sequence, were constructed for simple listric and ramp/flat listric extensional detachments. For each detachment geometry homogeneous sand, sand/mica and sand/clay models were used to simulate respectively, deformation of isotropic sediments, of anisotropic sediments and of sedimentary sequences with competency contrasts. Roll-over anticlines with geometrically necessary crestal collapse graben structures are characteristic of the steepening-upwards segments of listric extensional fault systems in all of our models. With progressive deformation, crestal collapse grabens show hanging wall nucleation of new faults. Variations in graben size, amount of fault rotation and throw, are dependent on detachment curvature and amount of extension. Individual faults and associated fault blocks may significantly change shape during extension. Complex and apparently conjugate fault arrays are the result of superposition of successive crestal collapse grabens. Ramp/flat listric extensional fault systems are characterized by a roll-over anticline and a crestal collapse graben system associated with each steepening-upwards segment of the detachment and a ramp zone consisting of a hanging wall syncline and a complex deformation zone with local reverse faults. The roll-over anticlines and crestal collapse graben are similar in geometry to those formed in simple listric extensional systems. The models demonstrate that the geometry of the detachments exerts a fundamental control on the evolution of hanging wall structures. Analysis of particle displacement paths for these experiments provides new insights into the mechanical development of roll-over anticlines. Two general models for deformation above simple listric and ramp/flat listric extensional detachments have been erected.     

Evaluating the fitness for use of spatial data sets to promote quality in ecological assessment and monitoring

This article proposes and illustrates a practical methodological framework to evaluate the fitness for use of spatial data sets for environmental and ecological applications, focusing on user requirements for specified application contexts. The methodology is based on the use of metadata to analyze similarity between the data characteristics and the user’s needs or expectations for several quality indicators. Additionally, the concept of ‘critical factors’ is introduced in this framework, allowing users to define which quality indicators have greater importance given their own requirements or expectations and the specified application contexts. The proposed methodology further allows integrating and interconnecting the spatial data quality (SDQ) evaluation methodology with metadata geoportals in WebGIS platforms, facilitating its operation by users from non-spatial disciplines and with often limited expertise on this subject. Examples of the evaluation of fitness for use for specific application contexts within the project BIO_SOS (‘Biodiversity Multi-SOurce Monitoring System: From Space To Species’ FP7 project) are presented. By providing a prompt and straightforward evaluation tool, the proposed methodology can encourage the implementation of SDQ evaluation routines in ecological assessment and monitoring programs, promoting a more adequate use of geospatial data and ultimately contributing to well-supported policy and management decisions.     

Paleolimnological assessment of human impacts in Lake Blanca, SE Uruguay

Paleolimnological techniques were used to assess human impacts onLake Blanca, a small (0.6 km²), coastal fresh waterbodyin southern Uruguay, which is the drinking water source for 100,000 localresidents. We retrieved a core that extends to about 1100 ¹⁴Cyr BP. ²¹⁰Pb ages, organic mater, CO₃, totalcarbon, nutrients, fossil pigments and diatoms allowed us to establishlimnological conditions before and after cultural impacts. Soil removal(1880–1960) and intensive cattle and sheep grazing (1943–1966) ledto gully formation in the catchment. This watershed erosion resulted inincreased sedimentation rates. The aquatic system appeared to be mesotrophicwith dominance of epibenthic diatoms until 1966, at which timeeutrophication intensified with forestry activities. Increases in nutrients, aswell as blooms of planktonic diatoms, were observed. During the last decade,tourist/urban development as well as high drinking water demand caused areduction in lake area. Subsequent marked increases in rainfall led to furtherphytoplankton blooms and macrophyte proliferation.