The role of stand history in assessing forest impacts

Air pollution, harvesting practices, and natural disturbances can affect the growth of trees and forest development. To make predictions about anthropogenic impacts on forests, we need to understand how these factors affect tree growth. In this study the effect of disturbance history on tree growth and stand structure was examined by using a computer model of forest development. The model was run under the climatic conditions of east Tennessee, USA, and the results compared to stand structure and tree growth data from a yellow poplar-white oak forest. Basal area growth and forest biomass were more accurately projected when rough approximations of the thinning and fire history typical of the measured plots were included in the simulation model. Stand history can influence tree growth rates and forest structure and should be included in any attempt to assess forest impacts.     

Lower thermal capacity limits of the common brown shrimp (Crangon crangon,L.)

Brown shrimp (Crangon crangon, L.) are subjected to a huge annual temperature range, and certain thermal conditions during winter have been identified to affect the brown shrimp population. Despite that, little is known about its thermal biology with regard to critically low temperatures. In the present study, we determined the critical thermal minima (CT_min) and the critical lethal minima (CL_min) of male and female brown shrimp of different body sizes in laboratory-based experiments. For the CT_min trials, shrimp were acclimated to 4.0, 9.0, and 14.0 °C and exposed to a cooling rate of ?0.2 °C min^?1. In the CL_min trials, brown shrimp were exposed to a cooling rate of ?1.0 °C day^?1 without prior thermal acclimation. Acclimation temperature significantly affected the temperature tolerance of brown shrimp (p < 0.001). CT_min among the experimental groups just varied slightly, and no clear effect of gender or body size was observed. In the CL_min trials, brown shrimp even tolerated the coldest temperature of ?1.7 °C that could be established in the experimental setup. However, we observed a negative relationship between temperature and reactivity within the range of 7.0 and 1.0 °C that was determined by means of the flicking response. This relationship suddenly broke between 1.0 and 0.0 °C where an abrupt drop in the reactivity of the shrimp became apparent. The results of this study revealed that brown shrimp hold a wider thermal range as originally reported and that it can cope with subzero temperatures. Implications of low-temperature tolerance are discussed in the context of the brown shrimp’s ecology as well as stock assessment.     

Factors influencing movement probabilities of big brown bats (Eptesicus fuscus) in buildings.

We investigated movements of female big brown bats (Eptesicus fuscus) roosting in maternity colonies in buildings in Fort Collins, Colorado (USA), during the summers of 2002, 2003, and 2005. This behavior can be of public health concern where bats that may carry diseases (e.g., rabies) move among buildings occupied by people. We used passive integrated transponders (PIT tags) to mark individual bats and hoop PIT readers at emergence points to passively monitor the use of building roosts by marked adult females on a daily basis during the lactation phase of reproduction. Multi-strata models were used to examine movements among roosts in relation to ambient temperatures and ectoparasite loads. Our results suggest that high ambient temperatures influence movements. Numbers of mites (Steatonyssus occidentalis) did not appear to influence movements of female bats among building roosts. In an urban landscape, periods with unusually hot conditions are accompanied by shifting of bats to different buildings or segments of buildings, and this behavior may increase the potential for contact with people in settings where, in comparison to their more regularly used buildings, the bats may be more likely to be of public concern as nuisances or health risks.     

Influence of test conditions on solubility controlled leaching predictions from air-pollution-control residues.

Leaching of Al, Ca, Mg, Si, S, Ba, Sr, Mo, Zn, Cd, Pb, and Cu from waste incineration air-pollution-control (APC) residues was investigated. Real-life conditions, i.e. removal of readily soluble compounds and longer equilibration time, were considered. Three different pH-static leaching experiments evaluating the importance of salt level and equilibration time were performed: (i) 48-h test on untreated APC residue samples, (ii) 48-h test on washed residue samples, and finally (iii) a 172-h test on washed residue samples. Experimental data were evaluated by geochemical modelling to identify potential solubility controlling minerals. For some elements (Al, Ca, Mg, Si, S, Mo, Zn, Cd, and Cu) the same controlling minerals were suggested regardless of the equilibration period or untreated/washed character of the tested material, whereas leaching of other elements (Ba, Sr) was far better described by considering a longer equilibration time, thereby pointing out the kinetic effects. Finally, a significant fraction of total lead (57%) was found to be rather mobile in the initial stage of leaching. Both pre-washing of the residues and longer equilibration times were shown to be simple yet useful methods to identify mineral phases that could control the release of constituents after the removal of readily soluble compounds in the initial stage of leaching.     

Noise susceptibility: A comparison of two naval aviator populations

The identification of characteristics of noise-susceptible (S) or noise-resistant (R) individuals is necessary for the development of noise-susceptibility risk profiles. Fifty-six naval aviators, categorized as having either incurred a hearing loss, i.e., hearing threshold levels (HTLs) > 40 dB at 4–8 kHz or retained normal hearing, i.e., HTLs ≤ 25 dB at 125 Hz-8 kHz, after thousands of flight hours were compared along several auditory and non-auditory dimensions. A number of variables occurred differentially in the two groups: Minimal Auditory Intensity Differential (MAID) scores at 2 kHz (p < 0.01) and 4 kHz (p < 0.001); iris pigmentation (blue eyes were over-represented in the S group; p < 0.05); systolic blood pressure (sitting; S group was higher; p < 0.05); calcium, albumin, and LDH levels (higher in the R group; p < 0.05); and present tobacco usage (more S aviators were currently smokers; p < 0.05). The S population also tended (p < 0.10) to exhibit elevated cholesterol and triglyceride levels as well as higher contralateral acoustic reflexes, and to have fewer individuals who had never smoked. Although no classic profile of the S or R individual definitely emerged, results suggested that at least one measurement device (MAID test) may serve as an “early warning” of imminent noise-induced damage. Further research, however, is required to test this possibility.