Aim The biotic resistance hypothesis posits that greater native species richness limits invasions of exotic species. However, negative native‐exotic richness relationships (NERRs) may reverse with increasing spatial scale, seemingly refuting the hypothesis. Here, we explore the effects of species competitive interactions, environmental factors, habitat heterogeneity and vertical vegetation tiers on the NERRs across spatial scales in native forests. Location New Zealand. Methods We combined vegetation, land cover and climate data to predict exotic richness from native richness at different vertical tiers (ground to canopy), land cover, plant competition (tree basal area, native ground cover), mean annual temperature and total rainfall. We considered four spatial scales, from single 20 × 20 m plots on an 8‐km grid to groups of plots across grids up to 128 km. Habitat heterogeneity was measured using the variance of climatic conditions among plots within a group. Results A negative native tree‐exotic richness relationship (NTERR) was observed at plot level but reversed with increasing spatial scale. Species competitive interactions showed a negative relationship with exotic richness at small/intermediate scales (≤32 km). Rainfall and temperature heterogeneity contributed to the positive NTERR at the largest scale. Adjacent exotic grassland cover had a positive relationship with exotic richness across all scales but did not prevent the NTERR from reversing. Main conclusions Our analysis shows the importance of considering vegetation structure and adjacent land covers, along with spatial heterogeneity and climatic factors, when testing the biotic resistance hypothesis in forest ecosystems. There is a clear indication that biotic resistance is primarily driven by native trees in the overstorey, probably by limiting resources available to ground tier plants. The results support the notion that the NERR is driven by competitive interspecific interactions at small spatial scales and by habitat heterogeneity at larger scales.
Managing invasive species requires knowledge of their ecology, including distribution, habitat use, and home range. In particular, understanding how biotic and abiotic factors influence home range can help with pest management decision-making, as well as informing native species management. Feral cats, self-sustaining cat populations that live independently of people, have caused numerous extinctions and continue to adversely affect native species globally. Managing feral cat populations requires spatially explicit knowledge to enable strategic deployment of management or monitoring devices, understand where native species are most likely to be at risk, and to mitigate the spread of cat-vectored diseases such as toxoplasmosis. Here, we present a meta-analysis of factors that influence feral cat home range size including land use types, differing levels of land use heterogeneity, and numbers of competitors. Male feral cats had larger home ranges than females, but effects of season, competitors, habitat heterogeneity, or land use on feral cat home range were not statistically significant, possibly due to high variability (male cat home range: 22.1 to 3232 ha; female cat home range: 9.6 to 2078 ha). This may reflect the fact that cats are generalists and are able to exploit any opportunity. Thus, we recommend that these factors and others, such as prey availability and composition, should be included in future research, so that the variability in home range size can be better understood. Improved understanding is vital for improving feral cat management in ecosystems where cats have been introduced.
Many New Zealand native bird species are threatened by introduced mammalian predators, and pest management programs are common in the country. Despite that, measuring the efficacy of such programs is often limited by resources, and thus the long-term population status of many native birds is not well documented. Here, we examined long-term population trends of forest bird species and changes in the bird community structure at Craigieburn Forest Park, where there was intermittent control of stoats (Mustela erminea). We analyzed 10,938 5-min bird point counts covering the periods 1978-1982, 1999-2004, and 2019-2020 in an oldgrowth Nothofagus (southern beech) forest. We assessed trends over time in the counts of each bird species with season, elevation, and site as co-variables. We also tested for a relationship with variable seed crops of the mast-seeding canopy tree, N. solandri var. cliffortioides. Bellbird (Anthornis melanura) was the only native species showing a continuous increase over time. In the first 25 years of the study, stoat control was intermittent, and more native birds decreased than increased. In later years, stoat control was continuous, and more native species increased than decreased. Large Nothofagus seed crops were associated with significant increases in all six exotic bird species tested, but only one of nine native bird species. These findings suggest that long-term trends of bird populations are influenced by the interactions of species vulnerability to stoat predation and the consistency of pest control efforts. Unfortunately, ship rats (Rattus rattus), which were absent at Craigieburn before 2010, are now common and may pose a new threat to native birds. Our results show that systematic long-term bird and seedfall monitoring, including careful archiving of sampling information, is helpful to guide conservation of the remaining native birds of New Zealand. Tendances de dénombrements d'oiseaux 1978-2020 dans une forêt de Nothofagus de Nouvelle-Zélande sous divers régimes de contrôle des prédateurs mammaliensRÉSUMÉ. De nombreuses espèces d'oiseaux indigènes de la Nouvelle-Zélande sont menacées par des prédateurs mammaliens introduits, et les programmes de lutte contre ces prédateurs y sont courants. Malgré ce fait, la mesure de l'efficacité de ces programmes est souvent limitée par les ressources et, par conséquent, le statut des populations de nombreux oiseaux indigènes sur un long horizon n'est pas bien documenté. Nous avons examiné les tendances de longue date d'espèces d'oiseaux forestiers et les changements dans la structure de la communauté d'oiseaux au parc Craigieburn Forest, où un contrôle intermittent d'hermines (Mustela erminea) a été effectué. Nous avons analysé 10 938 points d'écoute d'oiseaux de 5 minutes couvrant les périodes 1978-1982, 1999-2004 et 2019-2020 dans une forêt ancienne de Nothofagus (Hêtre austral). Nous avons évalué les tendances temporelles des dénombrements de chaque espèce d'oiseau, en utilisant la saison, l'altitude et le site comme covariables. Nous av...
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.