Neighbour identity hardly affects litter-mixture effects on decomposition rates of New Zealand forest species.

The mass loss of litter mixtures is often different than expected based on the mass loss of the component species. We investigated if the identity of neighbour species affects these litter-mixing effects. To achieve this, we compared decomposition rates in monoculture and in all possible two-species combinations of eight tree species, widely differing in litter chemistry, set out in two contrasting New Zealand forest types. Litter from the mixed-species litter bags was separated into its component species, which allowed us to quantify the importance of litter-mixing effects and neighbour identity, relative to the effects of species identity, litter chemistry and litter incubation environment. Controlling factors on litter decomposition rate decreased in importance in the order: species identity (litter quality) >> forest type >> neighbour species. Species identity had the strongest influence on decomposition rate. Interspecific differences in initial litter lignin concentration explained a large proportion of the interspecific differences in litter decomposition rate. Litter mass loss was higher and litter-mixture effects were stronger on the younger, more fertile alluvial soils than on the older, less-fertile marine terrace soils. Litter-mixture effects only shifted percentage mass loss within the range of 1.5%. There was no evidence that certain litter mixtures consistently showed interactive effects. Contrary to common theory, adding a relatively fast-decomposing species generally slowed down the decomposition of the slower decomposing species in the mixture. This study shows that: (1) species identity, litter chemistry and forest type are quantitatively the most important drivers of litter decomposition in a New Zealand rain forest; (2) litter-mixture effects—although statistically significant—are far less important and hardly depend on the identity and the chemical characteristics of the neighbour species; (3) additive effects predominate in this ecosystem, so that mass dynamics of the mixtures can be predicted from the monocultures

Iron Behaving Badly: Inappropriate Iron Chelation as a Major Contributor to the Aetiology of Vascular and Other Progressive Inflammatory and Degenerative Diseases

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular "reactive oxygen species" (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation. We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation). The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible. This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, etc...Comment: 159 pages, including 9 Figs and 2184 reference

No effects of experimental warming but contrasting seasonal patterns for soil peptidase and glycosidase enzymes in a sub-arctic peat bog

The nature of linkages between soil C and N cycling is important in the context of terrestrial ecosystem responses to global environmental change. Extracellular enzymes produced by soil microorganisms drive organic matter decomposition, and are considered sensitive indicators of soil responses to environmental variation. We investigated the response of eight hydrolytic soil enzymes (four peptidases and four glycosidases) to experimental warming in a long-term climate manipulation experiment in a sub-arctic peat bog, to determine to what extent the response of these two functional groups are similar. We found no significant effect of experimental spring and summer warming and/or winter snow addition on either the potential activity or the temperature sensitivity (of Vmax) of any of the enzymes. However, strong and contrasting seasonal patterns in both variables were observed. All of the peptidases, as well as alpha-glucosidase, had lower potential activity at the end of summer (August) compared to the beginning (June). Conversely, beta-glucosidase had significantly higher potential activity in August. Peptidases had consistently higher temperature sensitivities in June compared to August, while all four glycosidases showed the opposite pattern. Our results suggest that warming effects on soil enzymes are small compared to seasonal differences, which are most likely mediated by the seasonality of substrate supply and microbial nutrient demand. Furthermore the contrasting seasonal patterns for glycosidases and peptidases suggest that enzyme-based models of soil processes need to allow for potential divergence between the production and activity of these two enzyme functional groups.

The impacts of climate change on circumpolar biodiversity

Some of the most rapidly changing ecosystems on our planet are located in the polar regions (IPCC 2007; Turner et al. 2009; SWIPA 2011). In some areas of the Arctic and Antarctic, atmospheric temperatures are rising at rates more than double the global average. In addition, there are other direct human impacts on polar regions such as pollution, exploitation and development. Polar ecosystems and the biodiversity they support are already responding to this change and it is expected that even more profound impacts will occur this century. Compounding the risk to polar biodiversity is the fact that many polar ecosystems have limited functional redundancy; in the event of the loss of a single keystone species, they may potentially be exposed to cascading effects and complete ecosystem restructuring (Post et al. 2009). Rapid climate change affecting the polar regions will also have profound physical and ecological consequences for the rest of the planet since the ice-covered Arctic Ocean, the Antarctic continent, and the globally significant Antarctic Circumpolar Current (ACC) serve a key role in regulating the Earth’s climate and ocean systems. This special issue is intended to provide an overview of circumpolar change that crosses disciplines, systems, taxonomic groups and regions, and integrates papers that address a range of topics including: the monitoring of freshwater, marine, and terrestrial organisms in both the northern and southern polar regions, the role of protected areas in monitoring change in a warming world, polar resource management and development, impacts on northern indigenous peoples, case studies of the biodiversity of selected polar organisms, impacts of sea ice loss on terrestrial and marine organisms and ecosystems, interconnections with lower latitudes, and the influence of historical processes that have impacted polar diversity. This keynote paper is intended to provide background and insight into the issue by comparing and contrasting the Arctic and Antarctic regions in terms of their physical environment, human influences, indications of climate change and impacts on their biodiversity