To what extent can management variables explain species assemblages? A study of carabid beetles in forests

Studies concerning the influence of forest management on invertebrate communities often focus on a limited set of chosen variables and rarely quantify the importance of management as opposed to other influences. We aimed at: 1) comparing the importance for species assemblages of habitat variables defined by management with those independent of it; 2) understanding the ecological significance of the variation remaining when both management and non-management variables are used. We caught carabid beetles according to a stratified pitfall sampling based on forest structure, tree composition and stand age. Forty-nine habitat variables were measured using three spatial scales. We decomposed the variation of species assemblages with successive constrained ordinations based on sets of variables, and studied the life traits of the species least and best explained by the model including all of the variables. Forest structure, composition and stand age showed important effects but explained a relatively small part of the overall variation in species assemblages. Management accounted for ca 30% of the variation, but non-management variables had a significant impact and the interaction between management and non-management sets resulted in significant influences. Most species for which the variation was highly explained by the model were generally large and with inefficient wings, while the least explained species were small. Our study suggests that: 1) even with highly controlled samples, the influence of management on species assemblages should not be studied by a limited set of categorical variables; 2) management variables may interact with factors outside of the manager's control; 3) a significant part of the variation cannot be explained by habitat variables and needs taking ecological processes into account; 4) rules to optimise constrained ordination techniques applied to species-habitat studies can be proposed.     

10. REVIEWS

Winterbottom, J. M. 1974. The Cape Teal. Ostrich 45:110-132.     

Location of respiration activity in filamentous bacteria by image analysis

Respiration activity was located in Streptomyces ambofaciens using formazan crystals and image analysis. The technique was validated by comparing it to a global respiration rate measurement method. A uniform distribution of formazan crystals along the hyphae was found in cultivations in flasks and fermenter, throughout the cultures, although respiration is globally decreased when cultures age.     

The effect of mixtures of acetic acid and D-xylose on the growth rate of Candida blankii

Summary The growth rate of the yeastCandida blankii in carbon-limited chemostat culture on a mixture of D-xylose and acetic acid as carbon sources was determined not only by the acetic acid concentration in the feed, but also by the ratio of xylose to acetic acid. The hypothesis is put forward that the inhibitory effect of acetic acid on the growth rate is determined, in part, by the specific rate of acetic acid metabolism.     

Estradiol and catecholestradiols as possible genotoxic carcinogens

Estradiol and other estrogens are not classified as genotoxic carcinogens, but rather as tumor promoters in the multistage process of carcinogenesis. This study is a reexamination of the carcinogenic status of estradiol and the catecholestradiols (2-OHE2 and 4-OHE2) with the recently developed bacterial assays for genotoxic carcinogens, the Chromotest. The bacterial kits revealed estradiol and catecholestradiols as biphasic and potential genotoxic carcinogens with the following SOS inducing potency values: E2 43,265 (SD 8,300); 2-OHE2 30,153 (SD 2,500), and 4-OHE2 68,939 (SD 4,500). The differences between these values are statistically highly significant (p less than 0.0005). These results were confirmed by studies on Escherichia coli, which showed an increase in cell number and a stimulation of DNA content in the presence of the estrogens. It is therefore concluded that estradiol and the catecholestradiols are possible genotoxic carcinogens which probably act as tumor inducers rather than tumor promoters.     

Quantitative characterization of cellular differentiation of Streptomyces ambofaciensin submerged culture by image analysis

Image analysis methods were developed for light and epifluorescence microscopy of Streptomyces ambofaciens undergoing differentiation in submerged culture. Grey level images were obtained with an integration controlled CCD camera and allowed three parameters to be measured: occurence of empty zones in mycelium, number of septations, mycelium thickness.