Kīpuka Food Web Project Design and Timeline
This Kīpuka Food Web Project has selected a total of 34 kīpuka (0.07 – 10.2 ha), from 17 of which rats have been “removed” and continue to be controlled through trapping, and half that serve as controls and where rats continue to thrive. In the treated kīpuka, lethal snap traps are checked and reset on a regular basis. Ground and tree tracking tunnels are used to periodically to confirm the efficacy of the treatments and detect the presence of any rats despite control.
Plots have been established at the center and edge of each kīpuka for litter, plant and arthropod measurements. Litterfall is collected regularly from litter traps at each plot as an index of net primary production. A fraction of collected specimens and leaves of Metrosideros polymorpha are being analyzed for δ13C and δ15N. A before- and-after seedbank study will inform us about the impact of rats on forest seeds and regeneration.
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Light Detection And Ranging (LiDAR, 1.2 m-resolution) remote
sensing measures of total area, maximum canopy height, canopy height heterogeneity, topographic ground heterogeneity, and total volume are helping to estimate kīpuka habitat complexity. LiDAR is an optical remote sensing technology that can measure the distance or other properties of a target by illuminating the target with laser pulses. Our approach will make use of fine-grained natural variations within and between kīpuka in habitat complexity as covariates in statistical analyses. |
Branch clipping and malaise traps will yield information about arboreal arthropod communities. The data for species composition, abundance and stable isotopes of arboreal arthropods and plants will be used to estimate food chain length, trophic niche width and functional diversity, community-wide compositional similarity, diversity, density and biomass within trophic groups, and the distribution of total biomass among trophic groups.
We will measure bird density and diversity before as well as after two and four years of initial rat treatment. Nesting success will be monitored in a subset of larger kīpuka (>1 ha) where sufficient sample sizes of common species are found. Bird community differences derived from kīpuka size and rat treatment may also have indirect effects on arthropod communities. We plan to construct bird exclosures to estimate arthropod densities and composition, and track bird movement and range using radio telemetry to explore these possibilities.
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Timeline
Year 1~Pre-rat-removal measurements are taken
~Rat removal begins ~ avian radio telemetry studies ~Litterfall collection |
Year 2~rat maintenance continues
~avian radio telemetry studies |
Year 3~rat maintenance continues
~post-rat-removal measurements are taken ~ Bird exclusions established during peak of bird breeding season (April- July) ~ Litterfall Collection |
Year 4~rat maintenance continues
~avian radio telemetry studies |
Year 5~rat maintenance continues
~ post-rat-removal measurements are taken ~Bird exclusions established during peak of bird breeding season ~Litterfall Collection |