Lose biodiversity, gain disease McCallum, Hamish Ian
Proceedings of the National Academy of Sciences,
07/2015, Letnik:
112, Številka:
28
Journal Article
Apex predators are important in protecting biodiversity through top‐down influence on food webs. Their loss is linked with competitive release of invasive mesopredators and species extinctions. The ...Tasmanian devil (Sarcophilus harrisii) has experienced severe declines over a 15‐yr period as a novel transmissible cancer has spread across its current geographic range. We surveyed the mammalian community, using hair traps, across the spatial extent of the devil's progressive population decline. We found increased activity of alien invasive species (feral cats, black rats), and reduced small and medium‐sized native prey species in response to the timing of the decline. In areas of long‐term devil decline, invasive species comprised a significantly larger proportion of the community. The results provide evidence that the devil plays a keystone role in Tasmania's ecosystem with their decline linked to a shift toward an invasive state and biodiversity loss in one of Australia's most intact faunal communities.
Six species of trees located in the dry sclerophyll forests of southeast Queensland were studied to ascertain which was most suitable to be retained as hollow-bearing trees for nesting and denning by ...arboreal marsupials. Generally for all tree species, the number of entrances to hollows was positively correlated with the diameter at breast height (DBH) and the growth stage, and entrance diameters also increased in trees with a larger DBH. However, there were differences between the species;
Corymbia citriodora had few hollows until the individuals were very large while
Eucalyptus crebra had low numbers of hollows throughout its entire size range. It was concluded that a mixture of tree species provided a range of hollow sizes and positions that would be suitable for nesting and denning by arboreal marsupials in those forests. There were large differences between tree species in the relationship between tree size and estimated age. Five of the tree species took between 186 and 230 years to begin to produce hollows while
E. crebra took up to 324 years. This suggests that tree species other than
E. crebra may be the most preferred for retention in areas where hollow-bearing tree densities are lower than the prescribed level. Other data also suggests there are likely to be enough trees in larger size classes that would begin to form hollows within the next 50 years to compensate for an expected loss of hollow-bearing stags during that same period. In terms of forest operation, the retention of six hollow-bearing trees/ha would represent an estimated loss of 7.3–15% wood production.
Abstract The species richness and abundance of arboreal marsupials are positively related to the proportion of total stand basal area occupied by Corymbia citriodora ssp. variegata and tree height in ...South-East Queensland and have been related to nutrient availability and productivity in other parts of Australia. The objectives of this study were to assess the relationships of stand basal area occupied by C. citriodora and tree height, and the available nutrients and productivity in the dry sclerophyll forests of South-East Queensland. Leaf nutrient analysis of seven species of trees in South-East Queensland showed that the percentage by weight of phosphorus in leaves increased with the proportion of the total stand basal area of C. citriodora. This rate of increase was greater for C. citriodora than other species, indicating that C. citriodora may be more competitive on soils with greater available phosphorus. C. citriodora leaves also contained higher concentrations of nitrogen and potassium than the other tree species on multispecies sites. Timber productivity was greater at the sites where trees were taller, and tree height was positively correlated to the proportion of total stand basal area of C. citriodora and rainfall but was negatively correlated to the slope. These findings indicate that the most used habitat by arboreal marsupials in the dry sclerophyll forests of South-East Queensland (i.e., taller forests with a high proportion of the stand basal area occupied by C. citriodora) had higher concentrations of foliar nutrients and were more productive than less used habitats.
Abstract The habitat requirements of arboreal marsupials were investigated in the dry sclerophyll forests of southeast Queensland, Australia. Species richness and abundance of arboreal marsupials was ...correlated to the proportion of total stand basal area occupied by lemon-scented gum (Corymbia citriodora), the height of the tallest trees, and density of hollow-bearing trees. The first two factors suggested that the most productive forests were also the most suitable habitats for arboreal marsupials. Importantly, the number of hollow-bearing trees was a significant factor in determining species richness and abundance of arboreal marsupials in this study, with the maximum number of species reached at sites containing≥4 hollow-bearing trees/ha, and maximum abundance occurring at sites with≥6 hollow-bearing trees/ha. The proportion of C. citriodora was significant for the presence of the common brushtail possum (Trichosurus vulpecula), greater glider (Petauroides volans), and the yellow-bellied glider (Petaurus australis), while understory Acacia sp. density was important for the presence of the sugar glider (Petaurus breviceps). The yellow-bellied glider was also affected by two other variables: the density of hollow-bearing trees >50 cm diameter at breast height (dbh), and the time since the last logging. Current “Codes of Practice” regulating the density of hollow-bearing trees and silvicultural practices in state-owned timber production forests appear to provide adequate protection for arboreal marsupials, but the recently introduced increase in timber extraction rates within state forests may be detrimental to the animals. Also, protective prescriptions do not apply to the privately owned and leasehold estates, which contain the majority of the dry sclerophyll forests in southeast Queensland. FOR. SCI. 48(2):217–227.
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