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Beetle’s responses to edges in fragmented landscapes are driven by adjacent farmland use, season and cross-habitat movement

- Ng, Katherine, Barton, Philip, Macfadyen, Sarina, Lindenmayer, David, Driscoll, Don

  • Authors: Ng, Katherine , Barton, Philip , Macfadyen, Sarina , Lindenmayer, David , Driscoll, Don
  • Date: 2018
  • Type: Text , Journal article
  • Relation: Landscape Ecology Vol. 33, no. 1 (2018), p. 109-125
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  • Description: Context: Farming practices influence the degree of contrast between adjoining habitats, with consequences for biodiversity and species movement. Little is known, however, on insect community responses to different kinds of edges over time, and the extent of cross-habitat movement in agricultural landscapes. Objective: To determine temporal changes in beetle responses to different farmland-woodland edges, and document cross-habitat movement. Methods: We examined species richness, abundance, and movement across edges between remnant woodlands and four farmland uses (plantings, fallow, annual crops, woody debris applied over crops post-harvest) in southeastern Australia. We used directional pitfall traps to infer movement, and sampled at edges, and 20 and 200 m on both sides of edges, during spring and summer. Results: Detritivore and predator abundance varied between seasons across the edge between woodlands and all farmlands, but seasonal differences were weaker for fallow-woodland and woody debris-woodland edges. Detritivores moved from farmlands towards woodlands, but not across fallow-woodlands and woody debris-woodlands edges during summer. During summer, predators showed short-range movement towards edges from all farmlands except plantings, and towards woody debris from woodlands. Edges showed temporally stable predator richness and higher herbivore richness than adjoining habitats. Conclusions: Farmland use and season interactively affect beetle abundance across farmland-woodland edges. Woody debris can reduce seasonal fluctuations in beetle edge responses and increase permeability for cross-habitat movement, while plantings provide habitat during summer. Edges provide important resources for beetles in adjoining habitats, however, seasonal movement of predators specifically into edges may affect prey assemblages—a link requiring further study. © 2017, Springer Science+Business Media B.V.

Dynamic effects of ground-layer plant communities on beetles in a fragmented farming landscape

- Ng, Katherina, McIntyre, Sue, Macfadyen, Sarina, Barton, Philip, Driscoll, Don, Lindenmayer, David

  • Authors: Ng, Katherina , McIntyre, Sue , Macfadyen, Sarina , Barton, Philip , Driscoll, Don , Lindenmayer, David
  • Date: 2018
  • Type: Text , Journal article
  • Relation: Biodiversity and Conservation Vol. 27, no. 9 (2018), p. 2131-2153
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  • Description: Vegetation effects on arthropods are well recognized, but it is unclear how different vegetation attributes might influence arthropod assemblages across mixed-agricultural landscapes. Understanding how plant communities influence arthropods under different habitat and seasonal contexts can identify vegetation management options for arthropod biodiversity. We examined relationships between vegetation structure, plant species richness and plant species composition, and the diversity and composition of beetles in different habitats and time periods. We asked: (1) What is the relative importance of plant species richness, vegetation structure and plant composition in explaining beetle species richness, activity-density and composition? (2) How do plant-beetle relationships vary between different habitats over time? We sampled beetles using pitfall traps and surveyed vegetation in three habitats (woodland, farmland, their edges) during peak crop growth in spring and post-harvest in summer. Plant composition better predicted beetle composition than vegetation structure. Both plant richness and vegetation structure significantly and positively affected beetle activity-density. The influence of all vegetation attributes often varied in strength and direction between habitats and seasons for all trophic groups. The variable nature of plant-beetle relationships suggests that vegetation management could be targeted at specific habitats and time periods to maximize positive outcomes for beetle diversity. In particular, management that promotes plant richness at edges, and promotes herbaceous cover during summer, can support beetle diversity. Conserving ground cover in all habitats may improve activity-density of all beetle trophic groups. The impacts of existing weed control strategies in Australian crop margins on arthropod biodiversity require further study. © 2018, Springer Science+Business Media B.V., part of Springer Nature.
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