Forest fire induces short-term shifts in soil food webs with consequences for carbon cycling.

We tested for fire-induced (5-6 years post-fire) changes in the structure and functioning of the soil food web along a 3000-km north-south transect across European Russia, spanning all major forest types in the northern hemisphere outside the tropics. The total biomass of the detrital food web, including microbes and invertebrates, was not affected by fire. However, fire reduced the biomass of microfauna and mites, but had no impact on mesofauna or macrofauna. Fire also reduced rates of carbon (C) mobilisation by soil biota. Our results demonstrate that fire-induced shifts in soil food webs have significant short-term effects on forest soil C cycling, but that these effects vary across forest types and geographic locations.

Deep drilling reveals massive shifts in evolutionary dynamics after formation of ancient ecosystem.

The scarcity of high-resolution empirical data directly tracking diversity over time limits our understanding of speciation and extinction dynamics and the drivers of rate changes. Here, we analyze a continuous species-level fossil record of endemic diatoms from ancient Lake Ohrid, along with environmental and climate indicator time series since lake formation 1.36 million years (Ma) ago. We show that speciation and extinction rates nearly simultaneously decreased in the environmentally dynamic phase after ecosystem formation and stabilized after deep-water conditions established in Lake Ohrid. As the lake deepens, we also see a switch in the macroevolutionary trade-off, resulting in a transition from a volatile assemblage of short-lived endemic species to a stable community of long-lived species. Our results emphasize the importance of the interplay between environmental/climate change, ecosystem stability, and environmental limits to diversity for diversification processes. The study also provides a new understanding of evolutionary dynamics in long-lived ecosystems.

Reduction of metal exposure of Daubenton's bats (Myotis daubentonii) following remediation of pond sediment as evidenced by metal concentrations in hair.

Transfer of contaminants from freshwater sediments via aquatic insects to terrestrial predators is well documented in spiders and birds. Here, we analyzed the metal exposure of Myotis daubentonii using an urban pond as their preferred foraging area before and after a remediation measure (sediment dredging) at this pond. Six metal elements (Zn, Cu, Cr, Cd, Pb and Ni) were measured in the sediment of the pond, in EDTA extracts of the sediment and in hair samples of M. daubentonii foraging at the pond. Samples were taken before remediation in 2011 and after remediation in 2013. Metal concentrations were quantified by ICP-OES after miniaturized microwave assisted extraction. In 2011, the pond sediment exhibited a high contamination with nickel, a moderate contamination with copper and chromium and low contents of zinc, cadmium and lead. While sediment metal contents declined only weakly after remediation, a much more pronounced reduction in the concentrations of zinc, copper, chromium and lead concentrations was observed in bat hair. Our results suggest a marked decline in metal exposure of the bats foraging at the pond as a consequence of the remediation measure. It is concluded that Daubenton's bats are suitable bioindicators of metal contamination in aquatic environments, integrating metal exposure via prey insects over their entire foraging area. We further suggest that bat hair is a useful monitoring unit, allowing a non-destructive and non-invasive assessment of metal exposure in bats.

Variability of higher trophic level stable isotope data in space and time--a case study in a marine ecosystem.

RATIONALE: 1In shelf and coastal ecosystems, planktonic and benthic trophic pathways differ in their carbon stable isotope ratios (δ(13)C values) and nitrogen stable isotope ratios (δ(15)N values) and they increase predictably with trophic level. Stable isotope data are therefore used as a tool to study food webs in shelf and coastal ecosystems, and to assess the diets and foraging behaviour of predators. However, spatial differences and temporal changes in prevailing environmental conditions and prey abundance may lead to considerable heterogeneity in stable isotope values measured in focal animal species. METHODS: Here we assess spatial and temporal variability of δ(13)C and δ(15)N values in tissue samples of fish, squid and crustacean species captured over three years during research cruises close to the Falkland Islands, Southwest Atlantic. RESULTS: Both in δ(15)N values and especially in δ(13)C values, intra-species differences were large and often exceeded inter-species differences. Spatial patterns were weak, albeit statistically significant. The distribution of δ(13)C values was related to latitude, while the δ(15)N values varied with longitude. The distance from the coast and depth of catch influenced both δ(13)C and δ(15)N values. However, the importance of temporal variability greatly exceeded that of spatial variability. In addition to a moderate overall seasonal effect, we found that species differed strongly in their specific seasonal changes. CONCLUSIONS: Seasonal differences in the relative position of species or species groups in the C-N isotope space suggest changes in the utilisation of planktonic vs. benthic trophic pathways, indicating flexible foraging strategies in response to variable environmental conditions. These seasonal differences should be taken into account when analysing higher trophic level feeding ecology with stable isotope analysis.

Nematodes as sentinels of heavy metals and organic toxicants in the soil.

Field and laboratory research has repeatedly shown that free-living soil nematodes differ in their sensitivity to soil pollution. In this paper, we analyze whether nematode genera proved sensitive or tolerant toward heavy metals and organic pollutants in six long-term field experiments. We discuss overlaps between nematode physiological responses to heavy metals and to organic pollutants, which may explain why nematodes can exhibit co-tolerance toward several contaminants. We propose a simple method for separating direct effects of soil contamination on nematode populations from indirect effects mediated through the food chain. Finally, we analyze the extent to which nematodes exhibited consistent responses across the experiments analyzed. Our results show that (a) indirect effects of pollution were generally strong; (b) fewer nematode genera were tolerant than sensitive; (c) many genera, including practically all Adenophorea, exhibited a common response pattern to contaminants; and (d) several genera of the Secernentea exhibited differential tolerance toward particular pollutants. We conclude that bioindication of soil contamination should preferentially be based on tolerant, and less on sensitive, nematodes. We provide a list of nematode genera that may potentially serve as differential bioindicators for specific soil contaminants.