title: Tree-climbing capabilities of Norway and ship rats

authors: Foster, Stacey Patricia

subjects: invasive rats

abstract: Norway and ship rats (Rattus norvegicus and Rattus rattus) have invaded many habitats of conservation value worldwide, but Norway rats are widely assumed to be less of a threat to tree-nesting biota than are ship rats because they are less adept at climbing. We tested this assumption by measuring the capabilities of wild-caught captive rats of both species in reaching food rewards above ground, placed at fixed sites of increasingly difficult access. We confirmed that Norway rats were much slower and less agile than ship rats, but could in fact, given enough time, reach the same height above ground, run across the same thin ropes fixed at both ends and climb a real tree. However, they were more easily defeated by obstacles, more dependent on the availability of footholds, more vulnerable to falls, and those of >200 g body weight were significantly less likely to reach food rewards at the unsupported ends of small branches. We conclude that Norway rats seldom forage above ground, not because they cannot climb but because arboreal foraging is more risky and less likely to be rewarding for them.

text: Tree-climbing capabilities of Norway and ship rats Norway and ship rats (Rattus norvegicus and Rattus rattus) have invaded many habitats of conservation value worldwide, but Norway rats are widely assumed to be less of a threat to tree-nesting biota than are ship rats because they are less adept at climbing. We tested this assumption by measuring the capabilities of wild-caught captive rats of both species in reaching food rewards above ground, placed at fixed sites of increasingly difficult access. We confirmed that Norway rats were much slower and less agile than ship rats, but could in fact, given enough time, reach the same height above ground, run across the same thin ropes fixed at both ends and climb a real tree. However, they were more easily defeated by obstacles, more dependent on the availability of footholds, more vulnerable to falls, and those of >200 g body weight were significantly less likely to reach food rewards at the unsupported ends of small branches. We conclude that Norway rats seldom forage above ground, not because they cannot climb but because arboreal foraging is more risky and less likely to be rewarding for them.

year: 2011

title: Diverse and highly active diazotrophic assemblages inhabit ephemerally wetted soils of the Antarctic Dry Valleys

authors: Niederberger, Thomas D.

subjects: diazotrophs

abstract: Eolian transport of biomass from ephemerally wetted soils, associated with summer glacial meltwater runoffs and lake edges, to low-productivity areas of the Antarctic Dry Valleys (DV) has been postulated to be an important source of organic matter (fixed nitrogen and fixed carbon) to the entire DV ecosystem. However, descriptions and identification of the microbial members responsible for N₂ fixation within these wetted sites are limited. In this study, N₂ fixers from wetted soils were identified by direct nifH gene sequencing and their in situ N₂ fixation activities documented via acetylene reduction and RNA-based quantitative PCR assays. Shannon-index nifH diversity levels ranged between 1.8 and 2.6 and included the expected cyanobacterial signatures and a large number of phylotypes related to the gamma-, beta-, alpha-, and delta-proteobacteria. N₂ fixation rates ranged between approximately 0.5 and 6 nmol N cm⁻³ h⁻¹ with measurements indicating that approximately 50% of this activity was linked with sulfate reduction at some sites. Comparisons with proximal dry soils also suggested that these communities are not ubiquitously distributed, and conditions unrelated to moisture content may define the composition, diversity, or habitat suitability of the microbial communities within wetted soils of the DVs.

text: Diverse and highly active diazotrophic assemblages inhabit ephemerally wetted soils of the Antarctic Dry Valleys Eolian transport of biomass from ephemerally wetted soils, associated with summer glacial meltwater runoffs and lake edges, to low-productivity areas of the Antarctic Dry Valleys (DV) has been postulated to be an important source of organic matter (fixed nitrogen and fixed carbon) to the entire DV ecosystem. However, descriptions and identification of the microbial members responsible for N₂ fixation within these wetted sites are limited. In this study, N₂ fixers from wetted soils were identified by direct nifH gene sequencing and their in situ N₂ fixation activities documented via acetylene reduction and RNA-based quantitative PCR assays. Shannon-index nifH diversity levels ranged between 1.8 and 2.6 and included the expected cyanobacterial signatures and a large number of phylotypes related to the gamma-, beta-, alpha-, and delta-proteobacteria. N₂ fixation rates ranged between approximately 0.5 and 6 nmol N cm⁻³ h⁻¹ with measurements indicating that approximately 50% of this activity was linked with sulfate reduction at some sites. Comparisons with proximal dry soils also suggested that these communities are not ubiquitously distributed, and conditions unrelated to moisture content may define the composition, diversity, or habitat suitability of the microbial communities within wetted soils of the DVs.

year: 2012

title: Dendroarchaeology in New Zealand: extending the range of archaeologically useful species beyond kauri (Agathis australis)

authors: Boswijk, Gretel

abstract: Accurately establishing calendar dates for Māori wooden objects would place them in a secure temporal context and enable aspects of manufacturing and use to be explored within and between sites, and across time. Dendrochronology has the potential to produce accurate and precise calendar dates for wooden artefacts but in New Zealand application of this technique to Māori cultural material is limited as there is almost no overlap between wood species found in archaeological contexts and tree-species with proven suitability for tree-ring dating. Here we identify five archaeologically-useful species – kahikatea (Dacrycarpus dacrydioides), matai (Prumnopitys taxifolia), miro (Prumnopitys ferruginea), rimu (Dacrydium cupressinum) and totara (Podocarpus totara) – and assess their potential for dendrochronology. Of these, matai, miro and totara are identified as species that should be the subject of further comprehensive dendrochronological investigation.

text: Dendroarchaeology in New Zealand: extending the range of archaeologically useful species beyond kauri (Agathis australis) Accurately establishing calendar dates for Māori wooden objects would place them in a secure temporal context and enable aspects of manufacturing and use to be explored within and between sites, and across time. Dendrochronology has the potential to produce accurate and precise calendar dates for wooden artefacts but in New Zealand application of this technique to Māori cultural material is limited as there is almost no overlap between wood species found in archaeological contexts and tree-species with proven suitability for tree-ring dating. Here we identify five archaeologically-useful species – kahikatea (Dacrycarpus dacrydioides), matai (Prumnopitys taxifolia), miro (Prumnopitys ferruginea), rimu (Dacrydium cupressinum) and totara (Podocarpus totara) – and assess their potential for dendrochronology. Of these, matai, miro and totara are identified as species that should be the subject of further comprehensive dendrochronological investigation.

year: 2019