Geochemistry of three contrasting British peatlands: Complex patterns of cation availability and implications for microbial metabolism

ISTO = present addressInternational audienceCation availability in peat may limit CH4 production and microbial activity and thereby impact on rates of organic matter accumulation and the chemical character of the peat. We quantify total, soluble, and exchangeable cation concentrations, Exchange Site Saturation Levels (ESSLs) and organic fractions in bog-peat profiles and compare these with fen peat. Total and soluble cation concentrations are not correlated and these and exchangeable cation concentrations are lower in bog than fen peat. In all sites these vary with depth and the distribution patterns of individual cations are unique. This is explained by variation in ESSL, which is negatively correlated with Cation Exchange Capacity (CEC). Total cation concentrations in bog peat are higher in the top and bottom fractions than in the middle. Soluble concentrations in surface bog peat are low, because cations are trapped due to low ESSL. This does not occur in fen peat, with lower CEC and higher ESSL. CEC is related to total organic matter content, not just to Sphagnum, which has been invoked as the explanatory variable of high CEC in peat bogs. There is a complexity in the mechanisms controlling cation availability in peat and we suggest that total, soluble and exchangeable cation fractions need to be taken into account in studies of cation limitation of microbial activity in organic soils. CEC may also chelate exo-enzymes, further inhibiting decay processes

NICOLAS, Jean-Hervé, o.p., Contemplation et vie contemplative

The habitat is the basic unit for developments in life history, population dynamics, landscape ecology and conservation of organisms. It is frequently treated as a particulate, invariant and homogeneous entity (a patch). Here we examine the implications of using this concept of habitat in butterfly biology. In doing so, we suggest the alternative approach of applying a functional resource-based concept of habitat. This recognises the fundamental requirements of organisms, consumables and utilities, the latter describing suitable environmental conditions as well as essential substrates. We argue that a resource-based concept is critical for butterfly conservation and call for the development of a resource database on butterfly biology

The effects of visual apparency on bias butterfly recording and monitoring

A basic assumption in conservation is that comparable data are available for species to facilitate risk assessment of extinction. However, the capacity for carrying out cross-species comparisons for abundances and distributions among butterflies depends on the absence of bias in recording and monitoring or the existence of appropriate techniques for removing bias. Here, we investigate potential bias in cross-species comparisons for the apparency of butterfly adults (wing colour, size and behaviour) in three pivotal UK datasets: dates of discovery, Butterfly Monitoring Scheme (BMS) transect measures of abundance and Butterflies for the New Millennium (BNM) national recording scheme. Bias is found in all three datasets. Discovery date is affected by wing colour and size, BNM recording by adult behaviour and wing colour and BMS monitoring by adult behaviour. The nature and degree of bias differs between uncorrected cross-species comparisons and those with the application of phylogenetic contrasts. The findings urge caution in using these datasets for cross-species analysis without improvements and standardisation of recording and monitoring and the development of techniques to adjust for biases, in particular the use of suitable comparative techniques. The latter requires the construction of a molecular phylogeny for butterflies