973 resultados para Microbial ecology
Resumo:
Fossil pollen, stomata and charcoal were examined from a lake sedimentary sequence in the Glen Affric National Nature Reserve, one of the largest areas of remnant native pine woodland in Scotland, in order to assess ecosystem dynamics over the last 11 000 years. Results reveal that pinewood communities have been continuously present in East Glen Affric for the last 8300 years. Pinus sylvestris fi rst arrived in the area around 9900 cal. BP, but occurred in only low abundance for the subsequent 1600 years. Pine populations expanded around 8300 cal. BP and remained in relatively constant abundance throughout the remainder of the Holocene. There is no evidence of a hypothesized regional mid-Holocene ‘ pine decline ’ at the site. Charcoal results reveal that pinewood communities in East Glen Affric do not appear to have been dependent on fire for either their establishment or their maintenance as has previously been suggested.
Resumo:
The amphipod Gammarus pulex is an intermediate host to the acanthocephalan fish parasite Echinorhynchus truttae. Gammarus pulex has a wide trophic repertoire, feeding as a herbivore, detritivore and predator. In this study an examination was made of the effects of E. truttae parasitism on components of the G. pulex diet: stream-conditioned leaves, dead chironomids and live juvenile isopods Asellus aquaticus. Over 21 days, parasitism had no effect on daily feeding rates or wet weights of G. pulex fed on leaves or chironomids. Parasitism had a significant effect on the number of A. aquaticus killed by G. pulex, with parasitized individuals killing significantly fewer than their unparasitized counterparts. In addition, unparasitized amphipods killed all size classes of A. aquaticus indiscriminately, whereas parasitized animals tended to kill the smaller size classes. The impacts of the parasitism of G. pulex throughout the wider freshwater community are discussed.
