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.     

Einfluß der Gezeitenstromturbulenz auf die hydrographische Schichtung der Nordsee

Zusammenfassung Es wird das kritische vertikale Dichtegefälle ermittelt, das die Gezeitenstromturbulenz, die vom Meeresboden ausgeht, zum Erliegen bringt (Abb. 2). Ihm wird jenes vertikale Dichtegefälle gegenübergestellt, das der tägliche Wärmestrom durch die Turbulenz der winderzeugten Oberflächenströmungen bewirkt (Abb. 3). In derjeningen Tiefe, in der beide Gefällswerte gleich werden, liegt die Obergrenze der bodennahen Mischungsschicht, deren Verteilung in der Nordsee auf zwei ozeanographischen Schnitten verfolgt wird, die mit dem Vermessungs- und Forschungsschiff Gauss im August 1953 ausgeführt wurden (Abb. 1). Der eine Schnitt verläuft vom Nordausgang der Nordsee zu den westfriesischen Inseln, der andere von der schottischen zur norwegischen Küste (Abb. 4). Durch diese Anordnung konnten alle charakteristischen sommerlichen Lagen in der Nordsee erfaßt werden: der Übergang von der unbedeutenden bodennahen Mischungsschicht in der nördlichen Nordsee zur mächtigen Mischungsschicht der mittleren Nordsee, die dort in den Gebieten mit höheren Gezeitenströmen die normale sommerliche Sprungschicht zu einer wenige Dezimeter dicken Schicht zusammendrängt und die in den Gebieten mit starken Gezeitenströmen in die oberflächennahe Mischungsschicht übergreift. Als Folge davon wird in ausgedehnten Gebieten Schichtungslosigkeit während des ganzen Jahres aufrechterhalten. Die weitreichenden, verschiedenartigen Einflüsse dieser Mischungsvorgänge machen sich unter anderem auf den Jahresgang der Oberflächentemperatur der Nordsee deutlich bemerkbar (Abb. 5 und 6).

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Summary The critical vertical density gradient for suppressing the tidal current turbulence which originates from the bottom of the sea is determined (fig. 2). It is compared with the vertical density gradient caused by the daily heat transport in consequence of the turbulence of the wind-produced surface currents (fig. 3). At the depth where the two gradients become equal there lies the upper limit of the mixed ground layer. Its distribution in the North Sea is shown by two oceanographic profiles on the basis of measurements carried out by the survey and research ship Gauss in April 1953 (fig. 1). One profile extends from the northern exit of the North Sea to the West-Frisian islands, the other one from the Scotch to the Norwegian coast (fig. 4). By this arrangement all characteristic summer situations in the North Sea could be included: the change from the small mixed ground layer in the northern North Sea to the mighty mixed ground layer of the central North Sea compressing there, in regions with higher tidal currents, the normal summer discontinuity layer to a few decimeters and, in regions with strong tidal currents, reaching into the mixed surface layer. As a consequence in vast regions a state without stratification is maintained during the whole year. The far-reaching and various influences of these mixing processes, e. g. on the annual variation of the surface temperature of the North Sea, are evident (fig. 5 and 6).

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Résumé On recherche le gradient vertical critique de densité capable d'annuller le remous dû à la marée au fond de la mer (fig. 2) et on le compare au même gradient produit par le réchauffement diurne combiné avec la turbulence des courants de surface dûs au vent (fig. 3). La profondeur à laquelle ces deux gradients sont identiques fixe la limite supérieure de la couche de mélange voisine du fond. La distribution de cette couche dans la Mer du Nord ressort de deux profils relevés par le navire océanographique Gauss en août 1953 (fig. 1). L'un des profils va de l'extrémité septentrionale de cette mer jusqu'aux îles occidentales de la Frise; l'autre s'étend de la côte écossaise à celle de la Norvège (fig. 4). De cette façon une étude de tous les caractères estivaux de la Mer du Nord met en évidence le passage de la faible couche de mélange dans le Nord à la couche très importante dans la région moyenne; cette dernière couche a pour effet de réduire à quelques décimètres la couche de transition estivale normale dans les régions à courants de marée profonds tandis qu'elle pénètre dans la couche de mélange de surface dans les régions à forts courants de marée. En vertu de ces processus, l'absence de stratification se maintient pendant toute l'année dans de vastes régions. Les effets variés et lointains de ces phénomènes de mélange se font nettement sentir, entre autres, sur la variation annuelle de la température de surface dans la Mer du Nord (fig. 5 et 6).

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Mit 6 Textabbildungen.     

Spatial Pair-Copula Modeling of Grade in Ore Bodies: A Case Study

A real-world mining application of pair-copulas is presented to model the spatial distribution of metal grade in an ore body. Inaccurate estimation of metal grade in an ore reserve can lead to failure of a mining project. Conventional kriged models are the most commonly used models for estimating grade and other spatial variables. However, kriged models use the variogram or covariance function, which produces a single average value to represent the spatial dependence for a given distance. Kriged models also assume linear spatial dependence. In the application, spatial pair-copulas are used to appropriately model the non-linear spatial dependence present in the data. The spatial pair-copula model is adopted over other copula-based spatial models since it is better able to capture complex spatial dependence structures. The performance of the pair-copula model is shown to be favorable compared to a conventional lognormal kriged model.     

The ethnocultural component of tourism development in the Altai Republic

A characterization is provided for the recreation resources of the Altai Republic. The diversity of the national-ethnical composition of the population of the Altai Republic is determined as well as analyzing the spatial distribution of the ethnoses on its territory. The coefficients of ethnical diversity are calculated for all administrative districts. The territories with a different level of ethnical diversity and a different combination of ethnical groups are determined. The study revealed a connection of ethnical diversity and natural conditions of the territory and the concentration of separate ethnoses in definite landscapes. A characterization is provided for the ethnocultural tourism and recreation resources of the Altai Republic within the context of administrative districts. Information is provided concerning the territorial distribution of separate ethnical groups, traditional kinds of their nature management, religion, main national dishes, elements of national costume, national festivities and rites, etc. An analysis of the spatial distribution of the ethnocultural recreation resources identified promising clusters (nodes) or destinations for the arrangement of special ethnocultural tourist routes. Schematic maps are provided, which display the ethnical diversity in the districts of the region, and promising districts for the organization of ethnocultural tourist routes.     

Mobility and settlement system integration in the USSR

Recent Soviet research on commuting in the USSR is reviewed in the light of the General Strategy for a System of Settlement in the USSR, adopted in 1976. It is noted that rural-urban commuting to work has grown rapidly since 1975, particularly in the European parts of the USSR, and that most commuters prefer to live in rural or suburban areas within easy access of an urban center rather than in the central city itself.     

Forecasting off-road trafficability

Forecasting off-road trafficability represents an interesting problem in the earth science field, since variables ranging from solar insolation to soil shear strength are involved. However, existing trafficability models do not include precipitation-soil moisture deterministic submodels. Instead, they frequently commence with soil moisture and invoke empirical relationships to predict trafficability. This investigation couples a deterministic soil moisture submodel to a principal empirical soil moisture-trafficability model. Sensitivity analysis shows the impact cloud cover, as well as other variables, can have on the trafficability of three soil types, and the complexity of the post-storm trafficability response.     

Convective and conductive heat transfer in sedimentary basins

In the Earth's crust the temperature is largely controlled by heat conduction. However, under some circumstances, the thermal state is disturbed by advection of heat associated with groundwater flow. The corresponding thermal disturbance depends on the water flow velocity (modulus and direction) and therefore thermal data may be used to constrain the pattern of natural fluid flow. In this paper, some models of thermal disturbance induced by convective heat transfer are presented. They are based on the assumption that the water flow is concentrated in thin permeable structures such as aquifer or fault zones. The steady-state and transient thermal effects associated with such scenarios are computed using a somewhat idealized model which depends on a small number of parameters: flow rate, time, aquifer geometry and thermal parameters of surrounding rocks. In order to extract the conductive and convective components of heat transfer from temperature data and to estimate the corresponding fluid flow rate, it is first necessary to estimate the thermal conductivity field. The problem of the estimation of thermal conductivity in clay-rich rocks, based on laboratory and in-situ measurements, is emphasized. Then a method is proposed for the inversion of temperature data in terms of fluid flow. Vertical and lateral variations of thermal conductivity are taken into account and the fluid flow is assumed to be concentrated on a specified surface (2-D quasi-horizontal pattern). Thermal effects of the flow are simulated by a distribution of surface heat production which can be calculated and then inverted in terms of horizontal fluid flow pattern.