Home About us Contact
|
Home About us Contact | ||
|
|
||
Marion Island (marion + island)
Selected AbstractsFINE SCALE VARIABILITY IN SOIL FROST DYNAMICS SURROUNDING CUSHIONS OF THE DOMINANT VASCULAR PLANT SPECIES (AZORELLA SELAGO) ON SUB-ANTARCTIC MARION ISLANDGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 4 2009NATALIE S. HAUSSMANN ABSTRACT. Through changing soil thermal regimes, soil moisture and affecting weathering and erosion processes plants can have an important effect on the physical properties and structure of soils. Such physical soil changes can in turn lead to biological facilitation, such as vegetation-banked terrace formation or differential seedling establishment. We studied the fine scale variability in soil temperature and moisture parameters, specifically focusing on frost cycle characteristics around cushions of the dominant, vascular plant species, Azorella selago, on sub-Antarctic Marion Island. The frost season was characterised by numerous low intensity and very shallow frost cycles. Soils on eastern cushion sides were found to have lower mean and maximum temperatures in winterthan soils on western cushion sides. In addition, lower variability in temperature was found on eastern cushion sides in winterthan on western cushion sides, probably as a result of higher wind speeds on western cushion sides and/or eastern, lee-side snow accumulation. Despite the mild frost climate, extensive frost heave occurred in the study area, indicating that needle ice forms at temperatures above ,2°C. Our results demonstrate the effectiveness of frost pull as a heave mechanism under shallow frost conditions. The results highlight the importance of Azorella cushions in modifying site microclimates and of understanding the consequences of these modifications, such as potentially providing microhabitats. Such potential microhabitats are particularly important in light of current climate change trends on the island, as continued warming and drying will undoubtedly increase the need for thermal and moisture refugia. [source] A Review of Feral Cat Eradication on IslandsCONSERVATION BIOLOGY, Issue 2 2004MANUEL NOGALES efecto de depredación; erradicación; Felis catus; gato asilvestrado; islas Abstract:,Feral cats are directly responsible for a large percentage of global extinctions, particularly on islands. We reviewed feral cat eradication programs with the intent of providing information for future island conservation actions. Most insular cat introductions date from the nineteenth and twentieth centuries, whereas successful eradication programs have been carried out in the last 30 years, most in the last decade. Globally, feral cats have been removed from at least 48 islands: 16 in Baja California (Mexico), 10 in New Zealand, 5 in Australia, 4 in the Pacific Ocean, 4 in Seychelles, 3 in the sub-Antarctic, 3 in Macaronesia (Atlantic Ocean), 2 in Mauritius, and 1 in the Caribbean. The majority of these islands (75%; n= 36) are small (,5 km2). The largest successful eradication campaign took place on Marion Island (290 km2), but cats have been successfully removed from only 10 islands (21%) of ,10 km2. On Cousine Island (Seychelles) cat density reached 243 cats/km2, but on most islands densities did not exceed 79.2 cats/km2 (n= 22; 81%). The most common methods in successful eradication programs were trapping and hunting (often with dogs; 91% from a total of 43 islands). Frequently, these methods were used together. Other methods included poisoning (1080; monofluoracetate in fish baits; n= 13; 31%), secondary poisoning from poisoned rats (n= 4; 10%), and introduction of viral disease (feline panleucopaenia; n= 2; 5%). Impacts from cat predation and, more recently, the benefits of cat eradications have been increasingly documented. These impacts and benefits, combined with the continued success of eradication campaigns on larger islands, show the value and role of feral cat eradications in biodiversity conservation. However, new and more efficient techniques used in combination with current techniques will likely be needed for success on larger islands. Resumen:,Los gatos asilvestrados han sido responsables directos de un gran número de extinciones, particularmente en islas. En este estudio, se revisan los programas de erradicación de este felino con el fin de ofrecer información de utilidad en futuras acciones de conservación en islas. La mayor parte de las introducciones datan de los siglos diecinueve y veinte, mientras que las erradicaciones han sido realizadas básicamente durante los últimos 30 años, y sobre todo en la última década. Los gatos asilvestrados han sido erradicados de al menos 48 islas: 16 de ellas en Baja California (México), 10 en Nueva Zelanda, 5 en Australia, 4 en el Océano Pacífico, 4 en Seychelles, 3 en la Región Subantártica, 3 en Macaronesia (Océano Atlántico), 2 en Mauricio, y una en el Caribe. La mayoría de éstas (75%; n= 36) son de reducidas dimensiones (,5 km2), mientras que la más extensa es Marion Island (290 km2). En tan sólo 10 islas (21%) , 10 km2 se ha podido erradicar este depredador. En Cousine Island (Seychelles) la densidad de gatos alcanzó 243 individuos/km2; sin embargo, en la mayoría de las islas, las densidades no excedieron los 79,2 individuos/km2 (n= 22; 81%). Los métodos más comúnmente empleados fueron el trampeo y la caza, a menudo con perros (91% de un total de 43 islas). Con frecuencia dichas prácticas fueron empleadas conjuntamente. Otros métodos incluyeron venenos (1080, monofluoracetato de sodio en cebos de pescado: n= 13; 31%), envenenamiento secundario con ratas envenenadas (n= 4; 10%) y el virus de la leucemia felina (n= 2; 5%). La información sobre el efecto negativo de los gatos en islas y, más recientemente, el beneficio de su erradicación, se ha ido dando a conocer paulatinamente, poniendo de manifiesto su importancia en la conservación de la biodiversidad insular. No obstante, la combinación de técnicas nuevas y más eficientes junto con las habituales, será necesaria para el éxito de la erradicación de los gatos en islas de grandes dimensiones. [source] FINE SCALE VARIABILITY IN SOIL FROST DYNAMICS SURROUNDING CUSHIONS OF THE DOMINANT VASCULAR PLANT SPECIES (AZORELLA SELAGO) ON SUB-ANTARCTIC MARION ISLANDGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 4 2009NATALIE S. HAUSSMANN ABSTRACT. Through changing soil thermal regimes, soil moisture and affecting weathering and erosion processes plants can have an important effect on the physical properties and structure of soils. Such physical soil changes can in turn lead to biological facilitation, such as vegetation-banked terrace formation or differential seedling establishment. We studied the fine scale variability in soil temperature and moisture parameters, specifically focusing on frost cycle characteristics around cushions of the dominant, vascular plant species, Azorella selago, on sub-Antarctic Marion Island. The frost season was characterised by numerous low intensity and very shallow frost cycles. Soils on eastern cushion sides were found to have lower mean and maximum temperatures in winterthan soils on western cushion sides. In addition, lower variability in temperature was found on eastern cushion sides in winterthan on western cushion sides, probably as a result of higher wind speeds on western cushion sides and/or eastern, lee-side snow accumulation. Despite the mild frost climate, extensive frost heave occurred in the study area, indicating that needle ice forms at temperatures above ,2°C. Our results demonstrate the effectiveness of frost pull as a heave mechanism under shallow frost conditions. The results highlight the importance of Azorella cushions in modifying site microclimates and of understanding the consequences of these modifications, such as potentially providing microhabitats. Such potential microhabitats are particularly important in light of current climate change trends on the island, as continued warming and drying will undoubtedly increase the need for thermal and moisture refugia. [source] Assemblage level variation in springtail lower lethal temperature: the role of invasive species on sub-Antarctic Marion IslandPHYSIOLOGICAL ENTOMOLOGY, Issue 3 2009CHARLENE JANION Abstract. It is widely held both in the physiological literature, and more generally, that the average characteristics of species within an assemblage differ among sites. Such generalizations should be based on investigations of whole assemblages at sites, but this is rarely done. Here, such a study is undertaken for virtually the full assemblage of springtails found at sub-Antarctic Marion Island, by investigating supercooling points (SCPs) of 12 of the 16 species that occur there. Assemblage level variation tends to be less than that documented for assemblages across northern hemisphere sites but similar to that found at some Antarctic locations. Across this set of species, the mean SCPs of the indigenous species (mean ± SE =,17.2 ± 0.4 °C) do not differ significantly from that of the invasive species (,16.3 ± 0.7 °C). Overall, the introduction of several species to the island does not appear to have led to functional homogenization (for this trait). By combining the assemblage-level SCP data with information on the abundances of the species in each of four major habitats, it is also shown that severe but uncommon low temperature events could substantially alter species relative abundances. By resetting assemblage trajectories, such events could play an important role in the terrestrial system at the island. [source] | ||||||||||