Abstract: . Manipulation of soil biota, such as soil sterilization, may have complex effects as they alter soil properties as well as microorganism communities. To assess the effects of such manipulation, we conducted an experiment using three sterilizing approaches, two soil types, and two plant species to identify the problems that may occur when different sterilizing approaches are used. The sterilizing treatments decreased growth of plants and resulted in large changes in soil nutrients and pH. Such effects varied with the approach followed. Our data suggest that studied effects on soil biota may be misleading if we fail to consider such changes in the soil.

Abstract: . This study assesses whether the afforestation approach consisting in the introduction of woodland islets in “agricultural seas” can reconcile the restoration of woody vegetation and the persistence of open-habitat bird populations, providing further opportunities for other forest species to enrich bird diversity at the landscape level. We compared the species richness and abundance of bird communities in a field with 16 introduced woodland islets and in a nearby abandoned field located in central Spain during spring and winter time. The woodland islets presented higher accumulated species richness as well as a higher probability of finding new species if sampling effort were increased only in winter time. These trends were the opposite during spring time. Mean species richness and mean bird abundance were lower at the woodland islets than at the abandoned field in both seasons. We found a higher abundance of open-habitat specialist species in the abandoned field. Woodland islets favoured the wintering of chiffchaff Phylloscopus collybita. We did not find any effects on the only forest specialist species (blue tit Parus caeruleus) in spring. Bird richness and abundance were higher in edge islets than in inner islets. The introduction of larger and mixed plantations connected by hedgerows and a management that favoured the development of big trees, a lower tree density and a diverse shrub layer could promote bird diversity, allowing forest specialists and open-habitat species to coexist at the landscape scale.

Abstract: . Competition and facilitation are extensively studied in plant ecology and are central to ecological theory. However, these processes do not occur in isolation from each other and should be studied concurrently and synthetically. Here, we compare the relative citation success of studies that focus on either side of the same interaction coin in terms of number of publications and citations per publication in six of the following major themes in plant ecology: biogeography, populations, communities, ecosystems, evolution and conservation. There were eight times more publications on plant competition than on facilitation but this is not surprising given its long history of comprehensive and relatively exclusive study in plant ecology. Although studies of facilitation comprised a smaller body of literature, the mean citation rate for each publication was equivalent to that of competition studies. Thus, facilitation studies are being used as much as competition. These patterns of use by the ecological community clearly indicate that both aspects of plant interactions address broad themes and that studies on plant interactions should now strive to either test both simultaneously or at the very minimum include interpretations and relevant literature from both sets of ideas. Importantly, these broad trends illustrate the old axiom that quality and not quantity of studies may be a consideration in the success of a sub-discipline.

Abstract: . Multivariable regression models have been used extensively as spatial modelling tools. However, other regression approaches are emerging as more efficient techniques. This paper attempts to present a synthesis of Generalised Regression Models (Generalized Linear Models, GLMs, Generalized Additive Models, GAMs), and a Geographically Weighted Regression, GWR, implemented in a GAM, explaining their statistical formulations and assessing improvements in predictive accuracy compared with linear regressions. The problems associated with these approaches are also discussed. A digital database developed with Geographic Information Systems (GIS), including environmental maps and bird species richness distribution in northern Spain, is used for comparison of the techniques. GWR using splines has shown the highest improvement in accounted deviance when compared with traditional linear regression approach, followed by GAM and GLM.

Abstract: . Occupancy frequency distributions are commonly used as an approach to describe and analyse interspecific distribution patterns. However, the relative importance of biological versus artefactual mechanisms in shaping occupancy distributions is still largely undetermined. We evaluated the importance of different and interacting artefactual effects on the shape of occupancy distributions in local plant communities. The effects of sampling protocol parameters (i.e. size and number of sample units, sample extent, coverage, and intensity) on the shape of the occupancy distributions were examined separately. We identified the mechanisms that cause the effects by tracking the shifts of individual species between occupancy classes with varying parameters. Furthermore, the impact of different species abundance distributions and increasing levels of intraspecific aggregation on occupancy distributions was investigated by means of artificial assemblages. We show the following results: 1) increases in the number of sample units, sample extent, coverage, and intensity all result in a unimodal occupancy distribution with the mode in the lowest occupancy class; 2) an increase in sample unit size leads to a bimodal distribution; 3) changes that occur in the shape of the occupancy distributions with varying sampling protocol parameters can be explained by the movements of the species between occupancy classes; 4) different species abundance distributions may cause occupancy distributions with a left-hand mode or a bimodal distribution; and 5) the number of species in the highest occupancy class decreases with increasing degree of aggregation. The mode that almost always occurs in the lowest occupancy class is most likely due to the high number of rare species existing in most communities; the mode in the highest class emerges as a pure artefact that occurs when the sample unit size is relatively large compared to the sample extent. Consequently, the exclusion or separation of concurrent artefactual mechanisms is crucial when investigating the biological causes for the shape of occupancy distributions.

Abstract: WEB ECOLOGY 9, 2009 A recent paper suggested that alcohol consumption might deal a blow to a very sacred cow – scientific productivity (Grim 2008). Great numbers of comments followed. As noted by Sheil et al. (2008), the ‘‘Grim’s study cleverly highlights a more general lesson. His analyses and presentation follow accepted practices in evolutionary ecology. These are too seldom challenged. It appears we only notice failings when we are motivated by finding ourselves in the study population.’’ [italics are mine in all cited text]. Indeed, this fulfils one of the aims of the Oikos ‘beer study’ – to serve as a mirror for ecological research. In this, the beer study parallels the famous Sokal’s ‘experiment with cultural studies’ paper that was a mirror to some areas of social studies and humanities (Sokal 2008). Elsewhere, I will provide detailed comments on issues that were discussed by the critics of the Oikos study. Here, I reply specifically to two comments published by Web Ecology. Both Moya-Laraño (2008) and Sheil et al. (2008) draw attention to some issues of general interest. At the same time, their papers provide examples of some weaknesses of ecological papers and fallacious arguments so commonly employed by laymen and scientists. Although I intended the Oikos study to be fun, my message here is serious. Focusing on the drawbacks is a crucial condition for progress in science. Survey bias: the problems of self-reported data

Abstract: . Gradient analysis is an important tool for describing patterns in ecology. Natural environmental gradients are complex combinations of factors, suggesting that gradientsshould, when possible, be analyzed in multi-factorial ways. We searched papers published in Ecology, Global Change Biology, Journal of Ecology, Oecologia, Oikos, and Journal of Vegetation Science from January 2001 to December 2005, and found 133 papers matching two keywords: “gradient analysis” and “environmental gradient”. Of these, 86 utilized single-factor correlation analyses between ecological entities and natural environmental gradients. Thus the use of single-factor correlations in studies of natural environmental gradients is widespread despite the potential of this approach to overemphasize the importance of the particular factor chosen. We reanalyzed a data set from the literature, provided a example of contrasting analyses, and analyzed our own data with both single- and multiple-factor analyses to demonstrate how single-factor correlation can result in correlations that provide incomplete analysis. Integrated multi-factor approaches to studying natural environmental gradients cannot solve all analytical problems when two or more important variables are correlated, but are likely to better test the relative importance of factors driving ecological patterns.

Abstract: . Rapoport’s rule states that species at high latitudes have broader ranges than species at low latitudes. This rule has been strongly disputed over the years, and the majority of current scientists think that this is mostly a local phenomenon. However, if Rapoport’s rule applies, it should be a priori expected that taxa occurring in equatorial and tropical regions should be more threatened than those at temperate regions. In this paper, we test 1) whether Rapoport’s rule applies to Sciuridae genera (Mammalia, Rodentia) and, if so, 2) whether the research efforts by scientists have been concentrated on those taxa that, because of their range size, may be predicted to be more threatened (i.e. equatorial and tropical taxa). Distribution data on Sciuridae came from literature and were transformed as maps according to World Map Program, and data about number of papers published by genus and by latitude were collected from the ISI Web of Knowledge. Our analysis verified the occurrence of a Rapoport’s effect in Sciuridae in both the hemispheres: mean range size increased significantly with latitude increases in both hemispheres. However, literature data inspection revealed that only a few genera accounted for the great majority of studies, and these genera were widely distributed and found at high latitudes. Thus, there is a potentially serious gap between current knowledge and threat expectations for Sciuridae worldwide. We therefore strongly urge scientists to give priority attention towards field studies of tropical Sciuridae genera.

Abstract: . Mediterranean oak savannas cover about 4 million ha in California (northwest America) and 3 million ha in Spain and Portugal (southwest Europe), and are ecologically and socio-economically important systems. Here we review literature on the interactions between the two dominant elements of savannas – the oak overstorey, the herbaceous understorey, and the surrounding grassland matrix. We focus on the main ecological factors affecting the oak understorey environment: shade, soil moisture, soil nutrients, and animal-mediated effects. We then review the main features of the herbaceous community in the oak understorey, as compared to the adjacent open grassland, in terms of species composition, biomass, diversity, and soil seed bank. We examine processes associated with oak regeneration and growth, and their relationships with the herbaceous layer and other woody plants cover. Finally, we discuss the complex facilitative and interference interactions that occur in oak-grassland systems and review models proposed to explain the dynamics and coexistence of oak trees and herbaceous plants in savannas.