Austral Ecology最新文献

The rise in atmospheric carbon dioxide (CO2) and its potential to alter the climate are currently major global concerns. Forest plants and soil may absorb and retain carbon from the atmosphere, forming significant terrestrial carbon storage. The aims of this study were to estimate the carbon storage variance of Eucalyptus globulus and Cupressus lusitanica species in community and small-scale plantation forests under different management practices in the study area. A systematic sampling technique was used to collect field data. The transect line and the sample plot were positioned at 100 and 50 m, respectively, between them. The diameter at breast height (DBH) and total tree height were measured using a total of 60 plots (10 m × 10 m) from community plantation forests and 30 plots from small-scale plantation forests. The total mean carbon storage of C. lusitanica was 312.2 ± 97.9 t C/ha, and that of E. globulus was 356.1 ± 117.6 t C/ha. This was equivalent to 1146.4 ± 359.2 t C/ha CO2 (g) of C. lusitanica and 1306.9 ± 431.8 t C/ha CO2 (g) of E. globulus. The total mean carbon storage of E. globulus was higher than that of C. lusitanica in all carbon pools, except for litterfall biomass. From the management practices in small-scale plantations, the total mean carbon storage of C. lusitanica and E. globulus was 120.5 ± 37.5 t C/ha and 130.5 ± 40.8 t C/ha, respectively. This was equivalent to 442.2 ± 137.5 and 478.9 ± 149.7 t C/ha of CO2 (g), C. lusitanica and E. globulus, respectively. The results of this study will identify research gaps for future investigations and assist in addressing knowledge gaps for forest managers and organisations committed to providing enough attention to forest conservation.

Interspecific interactions are a common occurrence in nature, and, in some instances, two species form very close associations. Such symbiotic relationships vary, though, in terms of the relative advantages and disadvantages accrued by both species during interspecific interactions. Symbiotic relationships whereby both species benefit are thought to occur between oxpeckers and large mammals in Africa because while oxpeckers benefit by preying upon ticks and blood-sucking flies on the mammal's bodies, the mammals also benefit from the removal of ticks and flies. However, there is also evidence that the interactions between oxpeckers and mammals may not benefit both species because oxpeckers may not significantly reduce the abundance of ticks and may also deliberately keep wounds open, making such interactions harmful for mammals. Here, we respond to calls for further observations to help clarify the nature of such interactions by reporting a newly discovered symbiotic relationship between giant cowbirds (Molothrus oryzivorus) and South American tapirs (Tapirus terrestris) in Suriname. The cowbirds were observed feeding on ticks on the bodies of the tapirs and while it appeared that the tapirs were generally tolerant of the cowbirds, we did observe the tapirs attempting to repel the cowbirds when they appeared to target wounds on their bodies. The interactions we observed therefore appeared to benefit the cowbirds by providing them with prey and while the tapirs benefit from a reduction in tick abundance, the cowbirds did appear to target wounds on their bodies. Consequently, we tentatively conclude that the relationship between giant cowbirds and South American tapirs that we observed was beneficial to the birds and yet potentially harmful to the mammals and so further observations are needed to confirm if such interactions are context dependent. The interactions between giant cowbirds and South American tapirs provide an interesting opportunity to examine the nature of the evolutionary causes and ecological consequences of symbiotic interactions between birds and mammals.

Natural ecotones between forest and lake-swamp succession impose severe environmental filters for ant fauna, compared to adjacent forest habitats. This filter effect may be more severe for soil than canopy fauna. We tested this hypothesis by investigating the patterns of species occurrence, richness and composition of soil and canopy ants in forest and lake-swamp ecotones in a tropical river basin. We established two transects (250 m) at each site, one placed in the ecotone (i.e., flood zone) and the other inside the adjacent forest. Although upper and lower river basin had totally different ant species composition, the species occurrence, richness and composition distribution between habitats followed a similar pattern for both altitudes. Occurrence of soil ants and species richness was similar between interior and ecotone. The occurrence and species richness of canopy ants were both higher in the ecotones than in the forest interior. Ant species composition was similar between the ecotone and adjacent forest, for both soil and canopy fauna, and the ant species composition was different between seasons (dry and rainy) and between canopy and soil fauna. Most importantly, the environmental filter imposed by the ecotone and its unpredictable habitat conditions favoured fewer but opportunistic species, which drove the higher occurrence in these habitats. The years we studied were particularly dry and had a substantial decrease in lake depth. Hence, the abilities of species to best use unpredictable resources from the natural succession on the new dry grounds might have been defined by omnivorous, opportunistic and numerically dominant ants. The abiotic particularities of forest-water ecotones are important in the temporal dynamics of ant species assemblages. Fluctuations in water dynamics can restrict soil assemblages, but subtle changes in soil flooding also affect canopy fauna and can have unpredictable effects due to intensified variations in seasonal dynamics.

Alongside gradual changes in climate, extreme events such as droughts and heatwaves have increased in frequency globally. Together, chronic change and extreme events have been linked to forest die-off, as well as larger, more severe wildfires. Increased disturbance frequency inevitably increases the likelihood of compounding effects, highlighting the importance of understanding forest responses and recovery. This study investigated physiological characteristics of the dominant canopy tree species, Eucalyptus marginata, on sites affected by a drought/heatwave event (2011) and five years later by a wildfire (2016) in southwestern Australia. Using a factorial design of drought vulnerability (sites with high and low vulnerability to drought), and sites that had experienced moderate and high fire severity, physiological measurements including pre-dawn leaf water potential, stomatal conductance, chlorophyll fluorescence, leaf temperature, specific leaf area, and live foliar moisture content were quantified to reveal impacts and potential compound effects on tree function. Measurements were taken during a summer heatwave and typical wet-winter conditions to span periods of high and low stress. High drought vulnerability/ high severity wildfire sites had significantly lower pre-dawn leaf water potentials, and stomatal conductance. Although E. marginata is known to be drought and fire tolerant, this forest stand had visible tree death and canopy contractions (via leaf drop) between summer and winter measurements, suggesting low plant available water in summer approached E. marginata's threshold for survival in high severity fire sites. Trees on high drought vulnerability sites experienced significantly more stress, but fire severity effects primarily manifested within these sites, measured via decreased specific leaf area and chlorophyll fluorescence. These results reveal interactive, contingent nature of multiple disturbances and their implications for future forest recovery. Monitoring forest health and function is central to developing predictive capacity of forest dynamics and tree responses as extreme events increase in frequency, severity, and scale.

Arboreality in macropods ranges from fully terrestrial to fully arboreal species, with some functionally arboreal species. Potoroos (Tribe Potoroini) are assumed to be fully terrestrial; however, we document sightings and images of climbing and tree use in long-nosed potoroo (Potorous tridactylus trisulcatus) on French Island, Victoria. Ordination of body mass, head plus body length and tail length of macropods revealed some body forms occurred only in terrestrial species, that overlapped with a zone which also included facultatively arboreal macropods and potoroos, suggesting some degree of arboreality in potoroos could not be excluded based on body form. We conclude that long-nosed potoroos may, in at least some circumstances, climb and forage in trees and propose this could be a foraging strategy, niche exploitation or a predator-avoidance strategy.