Production systems based on reduced-tillage practices account for over 60% of the cropped land on the Canadian Prairies. Concerns have been expressed regarding potential shifts in weed communities as a result of changing tillage practices. Study objectives were to (1) determine the feasibility of combining and analyzing weed abundance data from 10 medium- to long-term studies on the Canadian Prairies that compared conventional-, reduced-, and zero-tillage systems, (2) identify species that are associated with specific tillage systems, and (3) place species into plant response groups according to the similarity of their tillage system response. Conventional-tillage systems were defined as including both a fall and spring sweep-plow operation before seeding spring crops, whereas reduced tillage consisted of only one sweep-plow operation shortly before seeding. Crops within zero-tillage systems were planted directly into the previous crop's stubble. The association between weed species and tillage systems was investigated using indicator species analysis. Species were assigned to tillage response groups on the basis of the results of the analysis and the expertise of the project scientists. Perennial species such as Canada thistle and perennial sowthistle were associated with reduced- and zero-tillage systems, but annual species were associated with a range of tillage systems. Field pennycress was placed in the conventional-tillage response group, Russian thistle in the zero-tillage group, and wild buckwheat and common lambsquarters were equally abundant in all tillage systems. The goal of classifying weed species based on common functional traits in relation to responses to tillage systems was not realized, in part, because the required information on species biology and ecology was either unavailable or not applicable to local conditions.

Quantitative analyses of the factors driving the distribution of bryophytes in the phyllosphere of tropical rain forests are rare. In this study we sampled epiphyllous bryophytes on two leaves of each of 57 individuals belonging to four phorophyte species (Asplundia pittieri, Carludovica drudei, Costus laevis and Dieffenbachia concinna) at three adjacent, but microclimatically varied sites in the Esquinas forest, Costa Rica. Microclimatic parameters and phorophyte identities were correlated to differences in cover, diversity and species composition of bryophyte assemblages by means of Kruskal–Wallis tests, non-metric multidimensional scaling and indicator species analysis. High relative humidity and in particular daily fluctuations in relative humidity proved to be the most important factors for epiphyll distribution suggesting severe constraints of epiphyll colonisation by pronounced humidity fluctuations. Differences in air temperature and light availability as well as phorophyte identity were only weakly correlated with bryophyte cover and diversity. However, species composition of epiphyllous assemblages was related to all microclimatic variables as well as to phorophyte identity. The strong response of epiphyllous bryophytes to even subtle microclimatic variations suggests that undisturbed forest canopies and their control on microclimate may be essential for the development of epiphyll communities.

Species are identified as bioindicators when their presence or abundance within sites of a particular habitat or a conservation area are high. Dufrêne and Legendre (1997), Ecological Monographs 67: 345–366, proposed the use of a flexible asymmetrical approach to detect indicator species and species assemblages characterizing groups of sites, the indicator value for each species being subsequently tested by randomization. Although the advantages of these methods in comparison to other multivariate or two-way indicator species analyses have been demonstrated, relatively few ecological studies have made use of them. The aim of the present study was to demonstrate the advantages of the indicator species test using a data set generated by traditional fisheries activities at four areas in the Bonifacio Strait Marine Reserve, Corsica, France. ANOVA, Kruskal-Wallis and another randomization test were also performed on the same data set. Of the 54 species caught in the fishing nets, the indicator species analyses identified 19 species for which the indicator value was significant for a given area, whereas the a posteriori Tukey test for ANOVA detected only 12 species for which the mass capture per unit effort was significantly greater for a given area. The efficiency of this new approach within the framework of conservation and marine reserve studies is demonstrated by focusing on three species (Sciaena umbra, Palinurus elephas and Maja verrucosa).