Facies distribution in CRP sediment cores from the Ross Sea, Antarctica

Clasts from the Cape Roberts Project cores CRP-2/2A and CRP-3 provide indications of glacially influenced depositional environments in Oligocene and Miocene strata in the western Victoria Land Basin, Antarctica. CRP-2/2A is interpreted to represent strongly glacially influenced, unconformity bound depositional sequences produced by repeated advance and retreat of floating and grounded ice across the shelf. A similar interpretation is extended to the upper 330 meters of the CRP-3 core, but the lower part of the core records shallow marine deposition with significantly less glacial influence. Clast shape analysis from selected coarse-grained facies throughout the cored interval indicates that most clasts are glacially sourced, with little distinction between diamictite and conglomeratic facies. Three dimensional clast fabric analysis from units immediately above sequence boundaries generally display weak or random fabrics and do not suggest that grounded ice actually reached the drillsite at these intervals. Striated and outsized clasts present in fine-grained lithofacies throughout the cores provide further evidence of sub-glacially transported sediment and iceberg rafting. The distribution of these striated and out-sized clasts indicate that a significant glacial influence persisted through most of the time represented by the cores with glaciers actively calving at sea-level introducing ice-berg rafted glacial debris even in the earliest Oligocene.

(Table 3) Collembola species density and diversity in control and OTC plots near Abisco Research Station

Ecosystems at high northern latitudes are subject to strong climate change. Soil processes, such as carbon and nutrient cycles, which determine the functioning of these ecosystems, are controlled by soil fauna. Thus assessing the responses of soil fauna communities to environmental change will improve the predictability of the climate change impacts on ecosystem functioning. For this purpose, trait assessment is a promising method compared to the traditional taxonomic approach, but it has not been applied earlier. In this study the response of a sub-arctic soil Collembola community to long-term (16 years) climate manipulation by open top chambers was assessed. The drought-susceptible Collembola community responded strongly to the climate manipulation, which substantially reduced soil moisture and slightly increased soil temperature. The total density of Collembola decreased by 51% and the average number of species was reduced from 14 to 12. Although community assessment showed species-specific responses, taxonomically based community indices, species diversity and evenness, were not affected. However, morphological and ecological trait assessments were more sensitive in revealing community responses. Drought-tolerant, larger-sized, epiedaphic species survived better under the climate manipulation than their counterparts, the meso-hydrophilic, smaller-sized and euedaphic species. Moreover it also explained the significant responses shown by four taxa. This study shows that trait analysis can both reveal responses in a soil fauna community to climate change and improve the understanding of the mechanisms behind them.

Soil characteristics and Collembola and Acari abundance in control and warming plots at Abisco Research Station

Extreme weather events can have negative impacts on species survival and community structure when surpassing lethal thresholds. Extreme winter warming events in the Arctic rapidly melt snow and expose ecosystems to unseasonably warm air (2-10 °C for 2-14 days), but returning to cold winter climate exposes the ecosystem to lower temperatures by the loss of insulating snow. Soil animals, which play an integral part in soil processes, may be very susceptible to such events depending on the intensity of soil warming and low temperatures following these events. We simulated week-long extreme winter warming events - using infrared heating lamps, alone or with soil warming cables - for two consecutive years in a sub-Arctic dwarf shrub heathland. Minimum temperatures were lower and freeze-thaw cycles were 2-11 times more frequent in treatment plots compared with control plots. Following the second event, Acari populations decreased by 39%; primarily driven by declines of Prostigmata (69%) and the Mesostigmatic nymphs (74%). A community-weighted vertical stratification shift occurred from smaller soil dwelling (eu-edaphic) Collembola species dominance to larger litter dwelling (hemi-edaphic) species dominance in the canopy-with-soil warming plots compared with controls. The most susceptible groups to these winter warming events were the smallest individuals (Prostigmata and eu-edaphic Collembola). This was not apparent from abundance data at the Collembola taxon level, indicating that life forms and species traits play a major role in community assembly following extreme events. The observed shift in soil community can cascade down to the micro-flora affecting plant productivity and mineralization rates. Short-term extreme weather events have the potential to shift community composition through trait composition with potentially large consequences for ecosystem development.

Effects of endophyte colonization of Vicia faba (Fabaceae) plants on the life

The effects of fungal endophytes Beauveria bassiana isolates ICIPE 279, G1LU3, S4SU1 and Hypocrea lixii isolate F3ST1 on the life-history of Phaedrotoma scabriventris and Diglyphus isaea, parasitoids of the pea leafminer Liriomyza huidobrensis, were studied in the laboratory. Parasitoids were allowed to parasitize 2nd-3rd L. huidobrensis larvae reared on endophytically-inoculated Vicia faba. In the control, parasitoids were reared on non-inoculated host plants. Parasitism, pupation, adult emergence and survival were recorded. No significant difference was observed between the control and the endophyte-inoculated plants in terms of parasitism rates of P. scabriventris (p = 0.68) and D. isaea (p = 0.45) and adult' survival times (p = 0.06). The survival period of the F1 progeny of P. scabriventris was reduced (p < 0.0001) in B. bassiana S4SU1 to 28 days as compared to more than 40 days for B. bassiana G1LU3, ICIPE 279 and H. lixii F3ST1. However, no significant difference (p = 0.54) was observed in the survival times of the F1 progeny of D. isaea. This study has therefore demonstrated the beneficial effects of both endophytes and parasitoids in L. huidobrensis population suppression.