In this issue

Abstract

IN THIS ISSUE Bruce Osborne Plant traits and soil processes Whilst soils are considered to be largely a consequence of the weathering of parent material, their ultimate characteristics and biological complexity are inextricably linked with the presence of vegetation. There is almost a symbiotic relationship between soil processes and the associated vegetation, with plants providing labile carbon, for instance, which supports microbial activity and the microbial populations , in turn, providing access to the essential nutrients required by plants. However, this is only one of many examples of the interactions that occur between vegetation and soils. Although many of these interactions are well known, much less is understood about how particular plant or vegetation characteristics or traits specifically impact on soil functioning, and this is the focus of a new Praeger Review, by Richard Bardgett, in this issue. There is now a significant body of evidence linking aboveground traits to soil microbial communities and soil carbon, but less is known about linkages with belowground traits. How do root traits, in particular, impact on soil processes and to what extent are variations in root traits linked to modifications in soil functioning? Whilst the development of new technologies has made these assessments more tractable, there are still major technical difficulties in measuring belowground traits, particularly in field settings. Identification of causal or functional links between shoot or root traits and soil processes is also a significant challenge. Not only is this information important for a fundamental understanding of the interrelationships between soil processes and vegetation , it could also provide potentially significant practical and environmental benefits through improved resource acquisition and greater nutrient retention in agro-ecosystems. Ain’t no barricade high (or wide) enough Enforcing any restriction on the movement of goods or organisms is beset by problems even when physical barriers are used. We have been lucky in Ireland that the movement of many unwanted organisms has been prevented because we are separated from both the UK and continental Europe by natural water barriers. Whilst natural barriers to free movement are important these can still be circumvented often through trade-related, humanassisted transportation. Remarkably, Ireland has no populations of non-indigenous crayfish, although the native white clawed crayfish is widespread. But, as Zen Faulkes points out in this issue, four non-indigenous crayfish species available through the pet trade in Ireland pose a significant risk if they are introduced into natural habitats. Although these risks of these crayfish have not been assessed, their success in the wild may be limited by low temperatures , although one, Cambarellus patzcuarensis, could still have an indirect impact on native populations because it is a potential vector for crayfish plague. Whilst legislation will limit the import of non-native crayfish into Ireland, there still seems to be a thriving crayfish trade within the country that should cause some concern. It is also possible that projected increases in temperature might also increase the chances of naturalised crayfish populations in the future. Perhaps there is a message here*that the implementation of any barrier to the movement of an unwanted species is always likely to be too late*and that such a move has to be combined with an appropriate follow-up management plan? Mealybugs Mealybugs are a group of plant-sucking insects with around 2,000 species, all of which are covered by a powdery wax material that resembles finely ground ‘meal’, hence their name. In many countries they are a common pest of greenhouses, where they can have a significant impact on the growth of plants, particularly ornamentals and succulents. Colonisation of the exudate produced by mealybugs by ascomycetes is also common, leading to secondary fungal infections. In some parts of the world, particularly the tropics and sub-tropics, where they are widely distributed, mealybugs can also be a common pest of fig and mango orchards. With increasing pressure to reduce pesticide use, alternative ways to controlling mealybugs are being examined. Moniruzzaman et al., in this issue, report on the effectiveness of two plant extracts, obtained from Jatropha ( Jatropha curcas) and neem (Azadirachta indica), together with conventional applications of the pesticide malathion, in controlling mealybugs in fig orchards. Their results indicate that both Jatropha and neem can...