ALBERT

Beschreibung: Predicting the effects of fire on biota is important for biodiversity conservation in fire-prone landscapes. Time since fire is often used to predict the occurrence of fauna, yet for many species, it is a surrogate variable and it is temporal change in resource availability to which animals actually respond. Therefore prediction of fire–fauna relationships will be uncertain if time since fire is not strongly related to resources. In this study, we used a space-for-time substitution across a large diverse landscape to investigate interrelationships between the occurrence of ground-dwelling mammals, time since fire, and structural resources. We predicted that much variation in habitat structure would remain unexplained by time since fire and that habitat structure would predict species' occurrence better than time since fire. In line with predictions, we found that time since fire was moderately correlated with habitat structure yet was a poor surrogate for mammal occurrence. Variables representing habitat structure were better predictors of occurrence than time since fire for all species considered. Our results suggest that time since fire is unlikely to be a useful surrogate for ground-dwelling mammals in heterogeneous landscapes. Faunal conservation in fire-prone landscapes will benefit from a combined understanding of fauna–resource relationships and the ways in which fire (including planned fires and wildfires) alters the spatial and temporal distribution of faunal resources.

Beschreibung: Animal species diversity is often associated with time since disturbance, but the effects of disturbances such as fire on functional diversity are unknown. Functional diversity measures the range, abundance, and distribution of trait values in a community, and links changes in species composition with the consequences for ecosystem function. Improved understanding of the relationship between time since fire (TSF) and functional diversity is critical given that the frequency of both prescribed fire and wildfire is expected to increase. To address this knowledge gap, we examined responses of avian functional diversity to TSF and two direct measures of environmental heterogeneity, plant diversity, and structural heterogeneity. We surveyed birds across a 70-year chronosequence spanning four vegetation types in southeast Australia. Six bird functional traits were used to derive four functional diversity indices (richness, evenness, divergence, and dispersion) and the effects of TSF, plant diversity and structural heterogeneity on species richness and the functional diversity indices were examined using mixed models. We used a regression tree method to identify traits associated with species more common in young vegetation. Functional richness and dispersion were negatively associated with TSF in all vegetation types, suggesting that recent prescribed fire generates heterogeneous vegetation and provides greater opportunities for resource partitioning. Species richness was not significantly associated with TSF, and is probably an unreliable surrogate for functional diversity in fire-prone systems. A positive relationship between functional evenness and structural heterogeneity was common to all vegetation types, suggesting that fine-scale (tens of meters) structural variation can enhance ecosystem function. Species more common in young vegetation were primarily linked by their specialist diets, indicating that ecosystem services such as seed dispersal and insect control are enhanced in more recently burnt vegetation. We suggest that patchy prescribed fire sustains functional diversity, and that controlled use of patchy fire to break up large expanses of mature vegetation will enhance ecosystem function.

Beschreibung: A recently theoretically deduced rill flow resistance equation, based on a power‐velocity profile, was tested experimentally on plots of varying slopes (ranging from 9% to 26%) in which mobile and fixed bed rills were incised. The measurements carried out in both conditions confirmed that the Darcy–Weisbach friction factor can be accurately estimated using the proposed theoretical approach. For the investigated conditions, the effect of sediment transport on the flow resistance law is negligible respect to the grain roughness effect. Abstract Rills caused by run‐off concentration on erodible hillslopes have very irregular profiles and cross‐section shapes. Rill erosion directly depends on the hydraulics of flow in the rills, which may differ greatly from hydraulics of flow in larger and regular channels. In this paper, a recently theoretically deduced rill flow resistance equation, based on a power–velocity profile, was tested experimentally on plots of varying slopes (ranging from 9% to 26%) in which mobile and fixed bed rills were incised. Initially, measurements of flow velocity, water depth, cross‐section area, wetted perimeter, and bed slope, carried out in 320 reaches of mobile bed rills and in 165 reaches of fixed rills, were used for calibrating the theoretical flow resistance equation. Then the relationship between the velocity profile parameter Γ, the channel slope, and the flow Froude number was separately calibrated for the mobile bed rills and for the fixed ones. The measurements carried out in both conditions (fixed and mobile bed rills) confirmed that the Darcy–Weisbach friction factor can be accurately estimated using the proposed theoretical approach. For mobile bed rills, the data were supportive of the slope independence hypothesis of velocity, due to the feedback mechanism, stated by Govers. The feedback mechanism was able to produce quasicritical flow conditions. For fixed bed rills, obtained by fixing the rill channel, by a glue, at the end of the experimental run with a mobile bed rill, the slope independence of the flow velocity measurements was also detected. Therefore, an experimental run carried out by a rill bed fixed after modelling flow action is useful to detect the feedback mechanism. Finally, the analysis showed that, for the investigated conditions, the effect of sediment transport on the flow resistance law can be considered negligible respect to the grain roughness effect.

Beschreibung: 〈span〉〈div〉SUMMARY〈/div〉Time-series of 〈span〉VP〈/span〉/〈span〉VS〈/span〉 ratio have been used to track local changes in elastic properties of rock volumes. Identifying such variations can provide information on the geophysical processes taking place inside a rock volume during the seismic cycle. A value of 〈span〉VP〈/span〉/〈span〉VS〈/span〉 ratio can be computed from traveltime of 〈span〉P〈/span〉 and 〈span〉S〈/span〉 waves generated from a single local event and it is representative of the value of the 〈span〉VP〈/span〉/〈span〉VS〈/span〉 ratio for the rocks traversed by the seismic ray, between the source and the receiver. It is straightforward, during a seismic sequence, to generate time-series of 〈span〉VP〈/span〉/〈span〉VS〈/span〉 ratio for events located close together and a single station. Such time-series should be able to monitor temporal variations of elastic parameters in the rock volume. Due to the very small nature of the expected changes in 〈span〉P〈/span〉- and 〈span〉S〈/span〉-wave velocity, the evaluation of 〈span〉VP〈/span〉/〈span〉VS〈/span〉 ratio time-series has been problematic in the past, and subjective choices about, for example the time-averaging scheme applied or event selection for constructing the time-series, have been proven to strongly affect the outcomes of the analysis. In this contribution, we present the application of a new methodology for a statistical evaluation of changes in 〈span〉VP〈/span〉/〈span〉VS〈/span〉 ratio time-series. The new methodology belongs to the wide class of ‘change-point analysis’ algorithms and is developed in the framework of Bayesian inference. The posterior probability distribution (PPD) of the change-point locations is obtained using a trans-dimensional Markov chain Monte Carlo (trans-D McMC) algorithm, where the existence and number of change-points is directly dictated by the data themselves. We apply the new algorithm to the seismic catalogue produced by the Alto Tiberina Near Fault Observatory seismic network (Northern Apennines, Italy). Here the high rate of background seismic release and the dense seismic network allow for a robust statistical analysis. The occurrence of change-points in 〈span〉VP〈/span〉/〈span〉VS〈/span〉 time-series identified with the proposed procedure is represented in space and time. The space–time distributions of change-points in the study area shows a clear peak of change-points following the occurrence of local main events, clustered along the main fault system activated. The robustness of the proposed approach makes it appropriate as an automatic, real-time tool for monitoring rock property changes related to seismic activity.〈/span〉

Beschreibung: We report on the discovery of a new X-ray pulsator, Swift J201424.9+152930 (Sw J2014). Owing to its X-ray modulation at 491 s, it was discovered in a systematic search for coherent signals in the archival data of the Swift X-ray Telescope. To investigate the nature of Sw J2014, we performed multiwavelength follow-up observations with space-borne ( Swift and XMM–Newton ) and ground-based (the 1.5-m Loiano Telescope and the 3.6-m Telescopio Nazionale Galileo) instruments. The X-ray spectrum of Sw J2014 can be described by a hard and highly absorbed ( N H  ~ 5 10 22  cm –2 ) power law ( ~ 1). The optical observations made it possible to single out the optical counterpart to this source, which displays several variable emission lines and total eclipses lasting 20 min. Total eclipses of similar length were observed also in X-rays. The study of the eclipses, allowed us to infer a second periodicity of 3.44 h, which we interpret as the orbital period of a close binary system. We also found that the period has not significantly changed over a ~7 yr timespan. Based on the timing signatures of Sw J2014, and its optical and X-ray spectral properties, we suggest that it is a close binary hosting an accreting magnetic white dwarf. The system is therefore a cataclysmic variable of the intermediate polar type and one of the very few showing deep eclipses.

Beschreibung: [1]  We studied the anatomy of the fault system where the 2009 L'Aquila earthquake (M W 6.1) nucleated by means of ~64 k high-precision earthquake locations spanning one year. Data were analyzed by combining an automatic picking procedure for P- and S-waves, together with cross-correlation and double-difference location methods reaching a completeness magnitude for the catalogue equal to 0.7 including 425 clusters of similar earthquakes. [2]  The fault system is composed by two major faults: the high angle L'Aquila fault and the listric Campotosto fault, both located in the first 10 km of the upper crust. We detect an extraordinary degree of detail in the anatomy of the single fault segments resembling the degree of complexity observed by field geologists on fault outcrops. We observe multiple antithetic and synthetic fault segments tens of meters long in both the hanging-wall and footwall along with bends and cross fault intersections along the main fault and fault splays. [3]  The width of the L'Aquila fault zone varies along strike from 0.3 km where the fault exhibits the simplest geometry and experienced peaks in the slip distribution, up to 1.5 km at the fault tips with an increase in the geometrical complexity. These characteristics, similar to damage zone properties of natural faults, underline the key role of aftershocks in fault growth and coseismic rupture propagation processes. Additionally, we interpret the persistent nucleation of similar events at the seismicity cut-off depth as the presence of a rheological (i.e. creeping) discontinuity explaining how normal faults detach at depth.

Beschreibung: Point measurement of soil properties allows to explain and simulate plot scale hydrological processes. An intensive sampling was carried out at the surface of an unsaturated clay soil to measure, on two adjacent plots of 4 × 11 m 2 and two different dates (May 2007 and February-March 2008), dry soil bulk density, ρ b , and antecedent soil water content, θ i , at 88 points. Field-saturated soil hydraulic conductivity, K fs , was also measured at 176 points by the transient Simplified Falling Head technique to determine the soil water permeability characteristics at the beginning of a possible rainfall event yielding measurable runoff. The ρ b values did not differ significantly between the two dates but wetter soil conditions (by 31%) and lower conductivities (1.95 times) were detected on the second date as compared with the first one. Significantly higher (by a factor of 1.8) K fs values were obtained with the 0.30-m-diam. ring than the 0.15-m-diam. one. A high K fs (〉 100 mm h -1 ) was generally obtained for low θ i values (〈 0.3 m 3 m -3 ) whereas a high θ i yielded an increased percentage of low K fs data (1–100 mm h -1 ). The median of K fs for each plot/sampling date combination was not lower than 600 mm h -1 and rainfall intensities rarely exceeded 100 mm h -1 at the site. Occurrence of runoff at the base of the plot needs a substantial reduction of the surface soil permeability characteristics during the event, probably promoted by a higher water content than the one of this investigation (saturation degree = 0.44 – 0.62) and some soil compaction due to rainfall impact. An intensive soil sampling reduces the risk of an erroneous interpretation of hydrological processes. In an unstable clay soil, changes in K fs during the event seem to have a noticeable impact on runoff generation and they should be considered for modeling hydrological processes. Copyright © 2012 John Wiley & Sons, Ltd.

Beschreibung: This article reports the results of a field investigation aimed to characterize the morphology of both rills monitored at Sparacia experimental area and two ephemeral gullies (EGs) located in the Tremamargi basin, Sicily, Italy. At first, the available literature data together with the measurements carried out in this investigation were used to show that the EG length is a key parameter for the estimation of the eroded volume. Then, the comparison among the pairs length and volume corresponding to measured rills, EGs and gullies showed that the exponent of the power relationship is independent of the channelized erosion type (rill, EG and gully), while a different scale factor has to be used for each erosion process. Finally, a single relationship applicable to all channelized erosion processes was deduced applying the dimensional analysis and the self-similarity theory. Copyright © 2011 John Wiley & Sons, Ltd.

Beschreibung: We have inverted P- and S-wave travel times from seismograms recorded by a dense local network to infer the velocity structure in the crustal volume where the April 6th 2009 main shock nucleated. The goal is to image local variations of P-wave velocity and Poisson ratio along the main shock fault zone for interpreting the complexity of the rupture history. The initial stages of the mainshock rupture are characterized by an emergent phase (EP) followed by an impulsive phase (IP) 0.87 s later. The EP phase is located in a very high VP and relatively low Poisson ratio (ν) region. The IP phase marks the beginning of the large moment release and is located outside the low ν volume. The comparison between the spatial variations of VP and Poisson ratio within the main shock nucleation volume inferred in this study with the rupture history imaged by inverting geophysical data allows us to interpret the delayed along-strike propagation in terms of heterogeneity of lithology and material properties.

Beschreibung: Abstract Planning soil conservation strategies requires predictive techniques at event scale because a large percentage of soil loss over a long‐time period is due to relatively few large storms. Considering runoff is expected to improve soil loss predictions and allows relation of the process‐oriented approach with the empirical one, furthermore, the effects of detachment and transport on soil erosion processes can be distinguished by a runoff component. In this paper, the empirical model USLE‐MB (USLE‐M based), including a rainfall‐runoff erosivity factor in which the event rainfall erosivity index EI30 of the Universal Soil Loss Equation (USLE) multiplies the runoff coefficient QR raised to an exponent b1 〉 1 is tested by the measurements carried out for the Masse (10 plots) and Sparacia (22 plots) experimental stations in Italy. For the Masse experimental station, an exponent b1 〉 1 was also estimated by tests carried out by a nozzle‐type rainfall simulator. For each experimental site in fallow conditions, the effect of the sample size of the plot soil loss measurements on the estimate of the b1 coefficient was also studied by the extraction of a fixed number N of randomly obtained pairs of the normalized soil loss and runoff coefficient. The analysis showed that the variability of b1 with N is low and that 350 pairs are sufficient to obtain a stable estimate of b1. A total of 1,262 soil loss data were used to parameterize the model both locally and considering the two sites simultaneously. The b1 exponent varied between the two sites (1.298–1.520), but using a common exponent (1.386) was possible. Using a common b1 exponent for the two experimental areas increases the practical interest for the model and allows the estimation of a baseline component of the soil erodibility factor, which is representative of the at‐site soil intrinsic and quasi‐static properties. Development of a single USLE‐MB model appears possible, and sampling other sites is advisable to develop a single USLE‐MB model for general use.