Austral Ecology最新文献

Pre-industrial forests are largely absent from environments long modified by humans, such as the Mediterranean region of central Chile. Around the capital, Santiago (33° S), the dominant vegetation is the “matorral,” characterised by shrubs, small trees, and succulents. However, colonial records indicate the presence of forests in this area. Here, we document for the first time the age, composition, and diameter distribution of a small remnant patch of primeval forest within the Río Clarillo National Park (RCNP), 45 km from Santiago. In this patch and in five surrounding matorral areas, we established 50 × 20 m plots, where we measured all trees with the diameter at breast height (DBH) > 5 cm. In the forest plot, we aged 36 trees using increment borers. The DBH showed an inverted J-distribution, dominated by the shade-tolerant Cryptocarya alba and Persea lingue (both Lauraceae) with individuals up to 1 m dbh and between 15 and 20 m tall. The basal area was 64 m²/ha, with 1140 trees/ha, and minimum ages ranged from 75 to 145 years. The matorral plots' trees were concentrated in smaller diameter classes (< 30 cm DBH), with an average basal area of 16.7 m² ± 6.5 m². The forest exhibited characteristics of late-successional stands and differed markedly from the surrounding matorral. The RCNP was first logged for charcoal in the mid-20th century, much more recently than many other areas of central Chile. The physiognomy of this patch resembles descriptions from 19th and early 20th century scholars. We hypothesise that forests like this were once much more common in the landscape than previously thought, and that present-day matorral represents an early successional forest maintained by recurrent human use. This patch represents a biological legacy from the past, provides a reference for long-term ecological restoration, and is unique, irreplaceable, and of immense value for conservation.

Large, severe wildfires are a major threat to biodiversity. Land managers often use prescribed fire to mitigate wildfire risks; however the impact of this strategy on many species remains poorly understood. We used a control-impact study to quantify the population response of the long-nosed potoroo (Potorous tridactylus) to prescribed fire. Live trapping was conducted at one unburnt control site and two burnt sites 12- and 24-months after small, patchy winter prescribed fires in a heathy woodland ecosystem, in south-eastern Australia. We estimated population density using spatially explicit capture-recapture analysis, and derived a relative abundance index which we compared to density using linear regression. At 12-months post-fire, estimated mean potoroo densities were 107 individuals per km² at the control site, 49 at Burn 1 and 119 at Burn 2. Compared to the control, densities were 54% lower at Burn 1 and 11% higher at Burn 2. At 24-months post-fire, densities were 176 potoroos per km² at the control, 76 at Burn 1 (57% lower than the control) and 137 at Burn 2 (22% lower than the control). There was no evidence that increases in density over time differed among sites. Despite substantial spatial and temporal variation in density, potoroos appeared resilient to patchy winter burns at these sites 2 years post-fire, although a fire-driven decline could not be ruled out due to the absence of pre-fire data. Density and relative abundance were positively correlated (R² = 0.90), and the relationship remained strong under a reduced sampling effort of at least four trap nights. These findings suggest that relative abundance may serve as a reliable proxy for potoroo density under certain conditions. This study improves our understanding of how a vulnerable Australian mammal responds to patchy winter burns, and shows that biodiversity conservation and fuel reduction may be compatible goals in some landscapes.

Members of the Pteropus genus (flying-foxes; fruit bats) occur predominantly on tropical islands, where they fulfil critical ecological roles as pollinators and seed dispersers; however, most of these species are under threat and sound population monitoring is an urgent requirement. Pteropus natalis (Christmas Island flying-fox) is classified as critically endangered and is the sole remaining endemic mammal on Christmas Island. The conservation management of this species has been hindered by difficulties in reliably monitoring its population due to challenging terrain and the species' behaviour. In this study, we used nocturnal drone-acquired thermal video imagery to detect P. natalis while foraging. Using a stratified random sampling method, we surveyed 43 5-ha plots across six vegetation types on Christmas Island. Pteropus natalis were detected most frequently in perennial wetlands, aligning with known habitat preferences. Extrapolating detections across the total area of each habitat type yielded a population estimate of 4441 (±64.0 SE), aligning with recent estimates obtained from a range of more labour-intensive methods. Our findings highlight the potential utility of nocturnal thermal drone surveys for monitoring population sizes and habitat use of island endemic flying-foxes, offering a scalable and efficient alternative to traditional survey methods for this ecologically important group.

Trophic interactions between birds, arthropods and plants are expected to be altered by anthropogenic factors, particularly in tropical mountain agroecosystems, where fragmentation affects ecological networks. However, little is known about how changes in forest cover influence insectivorous bird diversity and, in turn, affect arthropod communities and coffee crop productivity. In this study, we investigated how the extent of natural and semi-natural forest cover impacts bird-arthropod interactions and coffee plant traits in the Colombian Andes by combining bird and arthropod censuses, diet analysis and exclusion experiments. For 6 months, we conducted standardised mist-net bird sampling and faecal analyses to assess bird diets in coffee plantations, and we implemented bird exclusion treatments in four farms with varying forest cover. We assessed arthropod communities and vegetative and reproductive traits of Coffea arabica (Castillo variety) in both control and bird-excluded plants. We recorded 56 insectivorous bird species, with higher diversity and food web functionality in farms with greater forest cover. Key insectivorous birds, such as the Spot-breasted Woodpecker (Colaptes punctigula) and the Golden-crowned Warbler (Basileuterus culicivorus), primarily consumed arthropods from the orders Hymenoptera and Coleoptera. Bird exclusion increased arthropod biomass by 330%, species diversity by 33.4%, and abundance by 78.7% compared to control plants. Reproductive traits of coffee plants, such as fruit number, seed weight, fruit diameter and sugar content, were negatively associated with arthropod biomass and abundance but positively correlated with the abundance of predatory arthropods. These results supported the hypothesis that the greater the extent of forest cover, the greater the diversity of birds forming the insectivory network, and that coffee plants from which birds are excluded exhibit higher abundance or biomass of phytophagous arthropods, thereby affecting foliar and reproductive traits. The study underscores the importance of preserving natural and semi-natural forest remnants as safe habitats for insectivorous birds in coffee plantations.

Following identification of rainforest tree species at imminent risk of extinction from the myrtle rust disease in Australia further field data is presented to provide an update of impacts. A recently described species Rhodamnia zombi is added to the list of 16 species classified as Category X, that is, potentially Critically Endangered according to Red Listing criteria as a result of decline from the impacts of myrtle rust. Monitoring data demonstrates that one of the last remaining wild populations of Rhodomyrtus psidioides of mature trees has collapsed. One of three suspected clonal clumps of Rhodamnia rubescens has declined and another two survive despite evidence of the disease on new growth. A conservation strategy to recover Category X species involves: (1) Searching for and propagating individuals from the wild displaying tolerance; (2) Establishing plants in sites where they are safe from myrtle rust; (3) Undergoing genetic analysis to ensure wild diversity is represented; (4) Maintaining plants to produce seed; (5) Nursery screening of seedlings for myrtle rust resistant genotypes; (6) Screening field plantings for verification of resistant genotypes; (7) Rewilding resistant strains; Examples of successful ex situ cultivation in myrtle rust free settings or with fungicide application are collated and engender hope that this intensive strategy can succeed.

Seed loss attributed to predation poses a significant barrier to effective seed-based revegetation efforts. Given that seed is an expensive and finite resource, optimising its inclusion in ecological restoration is essential toward meeting ambitious targets for nature repair. Pelletised seeding can help protect native seeds and improve germination and establishment; yet exploration of how pellets influence post-dispersal seed retention remains understudied. Here, we tested the efficacy of pelletised seeding on seed removal using Acacia decurrens as a model. Using a field trial replicated across three sites, we performed two experiments. First, we measured seed retention among seeds provided in a pellet compared to seeds without any modification. Second, we tested whether additional anti-predator amendments could be added to the pellets to further improve seed retention. Seed retention was 42% higher in pellets relative to untreated seed. However, the addition of anti-predator amendments demonstrated minimal added benefit. These results demonstrate that pelletised seed delivery methods may improve the efficacy of seed use in ecological restoration by improving seed retention at sites where revegetation is required.

Butiá palm forests in South America represent an emblematic system that contains a poorly known biodiversity. These ecosystems are very fragmented due to agricultural practices that prevent regeneration and limit access to these ecosystems for many species. The transport of seeds by birds can connect patches of palm forests, facilitating a spatial network of fruit consumers. In this work, we evaluate the role of bird traits, individual palm traits, density, and spatial connectivity on the taxonomic and functional diversity of birds visiting palm forests. Through the use of camera traps during the fruiting period (February 2019 to May 2019), the richness and interaction of birds were recorded following a stratified sampling according to connectivity and distance to other ecosystems. Twenty-seven species of birds use palm trees. Isolation, palm density, fruit abundance, palm height, and forest distance were associated with the richness and activity of bird species. These results indicate that landscape alterations can change the spatial pattern of fruit consumption by bird species and the source-sink dynamics among palm ecosystems. We also found that two different bird assemblages consume fruits on the ground or in the canopy, and that these assemblages are shaped by palm traits, landscape connectivity, and bird traits. Therefore, two different and complementary networks are involved in the consumption of palm fruits. These results advance our understanding of frugivorous networks in general and support the management of these threatened palm ecosystems.