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The sustainability of agro-bioenergy systems is dependent on many factors, some local or regional in implementation, some others global in nature. This study assessed the effects of often ignored local and regional factors (e.g. alternative agronomic factor options, alternative agricultural production systems, alternative biomass flows, alternative conversion technologies etc. The results from this study suggests that key to enhancing the energy efficiency (and by extension the sustainability) of agro-bioenergy systems is paying attention to local and regional factors such as biomass conversion technology, alternative agronomic factor options, alternative agricultural production systems and available biomass flows.
The Alborz range of N Iran provides key information on the spatiotemporal evolution and characteristics of the Arabia-Eurasia continental collision zone. The southwestern Alborz range constitutes a transpressional duplex, which accommodates oblique shortening between Central Iran and the South Caspian Basin. The duplex comprises NW-striking frontal ramps that are kinematically linked to inherited E-W-striking, right-stepping lateral to obliquely oriented ramps. New zircon and apatite (U-Th)/He data provide a high-resolution framework to unravel the evolution of collisional tectonics in this region. Our data record two pulses of fast cooling associated with SW-directed thrusting across the frontal ramps at similar to 18-14 and 9.5-7.5 Ma, resulting in the tectonic repetition of a fossil zircon partial retention zone and a cooling pattern with a half U-shaped geometry. Uniform cooling ages of similar to 7-6 Ma along the southernmost E-W striking oblique ramp and across its associated NW-striking frontal ramps suggests that the ramp was reactivated as a master throughgoing, N-dipping thrust. We interpret this major change in fault kinematics and deformation style to be related to a change in the shortening direction from NE to N/NNE. The reduction in the obliquity of thrusting may indicate the termination of strike-slip faulting (and possibly thrusting) across the Iranian Plateau, which could have been triggered by an increase in elevation. Furthermore, we suggest that similar to 7-6-m.y.-old S-directed thrusting predated inception of the westward motion of the South Caspian Basin. Citation: Ballato, P., D. F. Stockli, M. R. Ghassemi, A. Landgraf, M. R. Strecker, J. Hassanzadeh, A. Friedrich, and S. H. Tabatabaei (2012), Accommodation of transpressional strain in the Arabia-Eurasia collision zone: new constraints from (U-Th)/He thermochronology in the Alborz mountains.
Soils play a crucial role in biogeochemical cycles as spatially distributed sources and sinks of nutrients. Any spatial patterns depend on soil forming processes, our understanding of which is still limited, especially in regards to tropical rainforests. The objective of our study was to investigate the effects of landscape properties, with an emphasis on the geometry of the land surface, on the spatial heterogeneity of soil chemical properties, and to test the suitability of soil-landscape modeling as an appropriate technique to predict the spatial variability of exchangeable K and Mg in a humid tropical forest in Panama. We used a design-based, stratified sampling scheme to collect soil samples at 108 sites on Barro Colorado Island, Panama. Stratifying variables are lithology, vegetation and topography. Topographic variables were generated from high-resolution digital elevation models with a grid size of 5 m. We took samples from five depths down to I m, and analyzed for total and exchangeable K and Mg. We used simple explorative data analysis techniques to elucidate the importance of lithology for soil total and exchangeable K and Mg. Classification and Regression Trees (CART) were adopted to investigate importance of topography, lithology and vegetation for the spatial distribution of exchangeable K and Mg and with the intention to develop models that regionalize the point observations using digital terrain data as explanatory variables. Our results suggest that topography and vegetation do not control the spatial distribution of the selected soil chemical properties at a landscape scale and lithology is important to some degree. Exchangeable K is distributed equally across the study area indicating that other than landscape processes, e.g. biogeochemical processes, are responsible for its spatial distribution. Lithology contributes to the spatial variation of exchangeable Mg but controlling variables could not be detected. The spatial variation of soil total K and Mg is mainly influenced by lithology.
Streamflow dynamics in mountainous environments are controlled by runoff generation processes in the basin upstream. Runoff generation processes are thus a major control of the terrestrial part of the water cycle, influencing both, water quality and water quantity as well as their dynamics. The understanding of these processes becomes especially important for the prediction of floods, erosion, and dangerous mass movements, in particular as hydrological systems often show threshold behavior. In case of extensive environmental changes, be it in climate or in landuse, the understanding of runoff generation processes will allow us to better anticipate the consequences and can thus lead to a more responsible management of resources as well as risks. In this study the runoff generation processes in a small undisturbed catchment in the Chilean Andes were investigated. The research area is characterized by steep hillslopes, volcanic ash soils, undisturbed old growth forest and high rainfall amounts. The investigation of runoff generation processes in this data scarce area is of special interest as a) little is known on the hydrological functioning of the young volcanic ash soils, which are characterized by extremely high porosities and hydraulic conductivities, b) no process studies have been carried out in this area at either slope or catchment scale, and c) understanding the hydrological processes in undisturbed catchments will provide a basis to improve our understanding of disturbed systems, the shift in processes that followed the disturbance and maybe also future process evolution necessary for the achievement of a new steady state. The here studied catchment has thus the potential to serve as a reference catchment for future investigations. As no long term data of rainfall and runoff exists, it was necessary to replace long time series of data with a multitude of experimental methods, using the so called "multi-method approach". These methods cover as many aspects of runoff generation as possible and include not only the measurement of time series such as discharge, rainfall, soil water dynamics and groundwater dynamics, but also various short term measurements and experiments such as determination of throughfall amounts and variability, water chemistry, soil physical parameters, soil mineralogy, geo-electrical soundings and tracer techniques. Assembling the results like pieces of a puzzle produces a maybe not complete but nevertheless useful picture of the dynamic ensemble of runoff generation processes in this catchment. The employed methods were then evaluated for their usefulness vs. expenditures (labour and financial costs). Finally, the hypotheses - the perceptual model of runoff generation generated from the experimental findings - were tested with the physically based model Catflow. Additionally the process-based model Wasim-ETH was used to investigate the influence of landuse on runoff generation at the catchment scale. An initial assessment of hydrologic response of the catchment was achieved with a linear statistical model for the prediction of event runoff coefficients. The parameters identified as best predictors give a first indication of important processes. Various results acquired with the "multi-method approach" show that response to rainfall is generally fast. Preferential vertical flow is of major importance and is reinforced by hydrophobicity during the summer months. Rapid lateral water transport is necessary to produce the fast response signal, however, while lateral subsurface flow was observed at several soil moisture profiles, the location and type of structures causing fast lateral flow on the hillslope scale is still not clear and needs to be investigated in more detail. Surface runoff has not been observed and is unlikely due to the high hydraulic conductivities of the volcanic ash soils. Additionally, a large subsurface storage retains most of the incident rainfall amount during events (>90%, often even >95%) and produces streamflow even after several weeks of drought. Several findings suggest a shift in processes from summer to winter causing changes in flow patterns, changes in response of stream chemistry to rainfall events and also in groundwater-surface water interactions. The results of the modelling study confirm the importance of rapid and preferential flow processes. However, due to the limited knowledge on subsurface structures the model still does not fully capture runoff response. Investigating the importance of landuse on runoff generation showed that while peak runoff generally increased with deforested area, the location of these areas also had an effect. Overall, the "multi-method approach" of replacing long time series with a multitude of experimental methods was successful in the identification of dominant hydrological processes and thus proved its applicability for data scarce catchments under the constraint of limited resources.
One of the mechanisms for sudden particle release is a decrease in groundwater salt concentration to below the critical salt concentration (CSC), where repulsion forces between fine particles and matrix surfaces exceed binding forces. In this paper, an attempt was made to determine the CSC with both batch and column experiments. Two types of sediments were tested: (a) homogeneous quartz sand and (b) mineralogically heterogeneous sediment, taken from the Hanford formation in southeast Washington. Stepwise decreasing concentrations of NaNO3 solution were applied until fine particles were released from the sediments and the CSC was determined. Two methods were used to minimize the interference of particle release due to physical forces (shear stress) in the batch experiments: (a) postexperimental correction for mechanical effects, and (b) minimization of shear stress on the sediments during the experiment. CSCs from batch experiments were compared to those obtained from column experiments. It was found that both the amount of particles released and the CSC were an order of magnitude higher for the Hanford sediment than for the Sand. Moreover, particle detachment above the CSC was observed for the Hanford sediment. This suggests that the concept of sharp CSCs could be problematic in natural heterogeneous sediments where fine particles may mobilize at salt concentrations significantly above the CSC, thus unexpectedly enhancing colloid-facilitated transport of contaminants. (C) 2004 Elsevier B.V. All rights reserved
Spatial patterns as well as temporal dynamics of soil moisture have a major influence on runoff generation. The investigation of these dynamics and patterns can thus yield valuable information on hydrological processes, especially in data scarce or previously ungauged catchments. The combination of spatially scarce but temporally high resolution soil moisture profiles with episodic and thus temporally scarce moisture profiles at additional locations provides information on spatial as well as temporal patterns of soil moisture at the hillslope transect scale. This approach is better suited to difficult terrain (dense forest, steep slopes) than geophysical techniques and at the same time less cost-intensive than a high resolution grid of continuously measuring sensors. Rainfall simulation experiments with dye tracers while continuously monitoring soil moisture response allows for visualization of flow processes in the unsaturated zone at these locations. Data was analyzed at different spacio-temporal scales using various graphical methods, such as space-time colour maps (for the event and plot scale) and binary indicator maps (for the long-term and hillslope scale). Annual dynamics of soil moisture and decimeterscale variability were also investigated. The proposed approach proved to be successful in the investigation of flow processes in the unsaturated zone and showed the importance of preferential flow in the Malalcahuello Catchment, a datascarce catchment in the Andes of Southern Chile. Fast response times of stream flow indicate that preferential flow observed at the plot scale might also be of importance at the hillslope or catchment scale. Flow patterns were highly variable in space but persistent in time. The most likely explanation for preferential flow in this catchment is a combination of hydrophobicity, small scale heterogeneity in rainfall due to redistribution in the canopy and strong gradients in unsaturated conductivities leading to self-reinforcing flow paths.