Influence of conservation tillage on winter bird use of arable fields in Hungary

Bird use of conservation tillage-established (CT—seedbed preparation without soil inversion) crops was assessed at two adjacent sites in western Hungary, in comparison with conventionally established (mouldboard ploughed—P) fields. Bird abundance was assessed in a typical rotation of spring-sown maize and winter wheat in three consecutive winters. In the first winter, several species and the guild of seed-eating passerines were significantly more abundant on CT established plots, in both crop types. In the second winter, only starlings were more abundant on CT plots. In the third winter, only skylarks favoured CT over P plots. In combination with agri-environment scheme measures designed to provide resources for biodiversity, conservation tillage could play a role in softening the impact of agriculture on farmland birds in Hungary and elsewhere in Eastern Europe, in addition to its potential for reducing soil erosion and diffuse pollution.     

THE ECONOMICS OF GEOTHERMAL POWER

This article, based on a rapporteur's report, is a synthesis of papers read before the United Nations Symposium on the Development and Utilization of Geothermal Resources, held at Pisa, Italy, in 1970. It covers a broad cross-section of experience in exploiting geothermal energy, especially in Hungary, Iceland, Italy, Japan, New Zealand, the Union of Soviet Socialist Republics and the United States of America     

Dispersion of displaying male sage grouse

Summary The degree to which male sage grouse select lek sites and females select nesting sites to maximize proximity to the other sex was examined by contrasting male dispersions with the dispersions and movements of females in the months preceeding incubation. Wintering females exhibit highly overlapping ranges due to shared use of central refuging areas. In late winter and early spring, females move an average 9 km from wintering areas to select nest sites and males begin occupying leks. Pooled evidence suggests that females select nest sites independently of male dispersion whereas males adjust lek occupation so as to maximize proximity to females. Relevant observations include females visiting nest sites before leks, moving further to select a nest site than to select a lek, and increasing their distance to leks as a result of selecting nest sites. In addition, males avoid leks until females have moved to within 5 km of the arenas, abandon early season leks as local female densities drop, and exhibit dispersions in which mean ratios of females/male are similar across leks. Contrasts between predicted and observed dispersions of males showed that hotspot settlement models are adequate to explain male dispersions on very coarse scales (2 km or greater); on finer scales, habitat preferences of males and tendencies for males to cluster tightly must be invoked in addition to hotspots to explain specific lek sitings.     

Differences in acoustic directionality among vocalizations of the male red-winged blackbird (<Emphasis Type="Italic">Agelaius pheoniceus</Emphasis>) are related to function in communication

Studies of animal acoustic communication have found that the frequency and temporal structure of acoustic signals can be shaped by selection for efficient communication. The directionality of acoustic radiation may also be adapted for communication, but we know relatively little about how directionality varies with signal function, sender morphology, and the environment in which the sound is transmitted. We tested the hypothesis that the directionality of a vocalization is adapted to its function in communication. This hypothesis predicts that vocalizations that are directed to multiple conspecifics (e.g., advertisements and alarms) will be relatively omnidirectional because this will maximize the number of neighbors and mates that receive the signal, and that vocalizations directed to particular individuals will be relatively directional because this will maximize detection of the signal by the targeted receiver and minimize eavesdropping. To test these predictions, we measured the directionality and amplitude of red-winged blackbird (Agelaius pheoniceus) vocalizations in the field by recording vocalizations simultaneously on eight calibrated microphones encircling the bird. We found significant variation in directionality among vocalizations. Supporting our predictions, we found that the most omnidirectional vocalizations were those used to alert conspecifics to danger, and the most directional vocalizations are those used during courtship and solicitation of copulation, when the costs of eavesdropping are likely to be high. These results suggest that the directionality of red-winged blackbird vocalizations is shaped by selection for effective communication. This study is the first to provide statistical support for the hypothesis that directionality is related to the function of a signal in communication.     

Diffusion of HTO, Cl and I in Opalinus Clay samples from Mont Terri: Effect of confining pressure

Diffusion coefficients (T=23±2 °C) and accessible porosities for HTO, ³⁶Cl⁻ and ¹²⁵I⁻ were measured on Opalinus Clay (OPA) samples from the Mont Terri Underground Rock Laboratory (URL) using the through-diffusion technique. The direction of transport (diffusion) was perpendicular to bedding. Special cells that allowed the application of confining pressure were designed and constructed. The pressures ranged from 1 to 5 MPa, the latter value simulating the overburden at the Mont Terri URL (about 200 m). The test solution used in the experiments was a synthetic version of the Opalinus Clay pore water, which has Na⁺ and Cl⁻ as the main components (I=0.42 M).The measured values of the effective diffusion coefficients (D_e) and rock capacity factors (α) are: D_e=1.2–1.5×10⁻¹¹ m² s⁻¹ and α=0.09–0.11 for HTO, D_e=4.0–5.5×10⁻¹² m² s⁻¹ and α=0.05 for ³⁶Cl⁻ and D_e=3.2–4.6×10⁻¹² m² s⁻¹ and α=0.07–0.10 for ¹²⁵I⁻. For non-sorbing tracers (HTO, ³⁶Cl) the rock capacity factor α is equal to the diffusion-accessible porosity . The experimental results showed that pressure only had a small effect on the value of the diffusion coefficients. Increasing the pressure from 1 to 5 MPa resulted in a decrease of the diffusion coefficient of 17% for HTO, 28% for ³⁶Cl⁻ and 30% for ¹²⁵I⁻. Moreover, the diffusion coefficients for ³⁶Cl⁻ and ¹²⁵I⁻ are smaller than for HTO, which is consistent with an effect arising from anion exclusion.The diffusion coefficients of HTO and ¹²⁵I⁻ measured in this study are in good agreement with recent measurements at three other laboratories performed within the framework of a laboratory comparison exercise. The values of the diffusion-accessible porosities show a larger degree of scatter.     

Porewater chemistry in compacted re-saturated MX-80 bentonite

Bentonites of various types are being investigated in many countries as backfill materials in high-level radioactive waste disposal concepts. Being able to understand the chemistry of the porewater in compacted bentonite is very important since it is critical to predicting radionuclide solubilities and to the synthesis of sorption data bases, and hence to repository safety studies. In this paper, porewater compositions in compacted bentonites are calculated, taking into consideration such factors as montmorillonite swelling, semi-permeable membrane effects, very low "free water" volumes, and the highly effective buffering characteristics of the exchangeable cations and the amphoteric edge sites. The former buffer the cation concentrations and the latter fix the pH in the porewater of a re-saturated bentonite. The above considerations are used in conjunction with previously measured physico-chemical characterisation data on MX-80 powder to calculate porewater compositions in compacted bentonites. For the MX-80 material specified, the porewaters calculated for initial dry densities between 1200 and 1600 kg m(-3) had relatively high ionic strengths (I approximately 0.3 M), similar cation concentrations and a pH equal to 8.0. The porewaters changed from being Na(2)SO(4)-rich at 1200 kg m(-3) to a NaCl/Na(2)SO(4) type water at 1600 kg m(-3).