seedling recruitment

Globally, lowland forests have been depleted, fragmented, and degraded by land clearance and conversion by humans. Many remnants are also invaded by non-native plants and mammals, which can exacerbate biodiversity loss and impede ecosystem recovery. We examined the effects of non-native ground cover weeds and mammals on the seedling recruitment of native woody plants in lowland forests in northern New Zealand by following establishment over 2 years at sites experiencing different levels of weed cover, with or without supplemental seed addition, and with or without mammal exclusion.

Pinus contorta is a widespread and ecologically damaging invasive tree in the southern hemisphere. Land managers want control methods that limit reinvasion by P. contorta and promote the recovery of native plant communities and ecosystem functions. Recovery of native vegetation may be slow if native seed supply is limited and/or introduced mammals destroy seeds and seedlings. We investigated how tree control method (felling or poisoning), seed addition, and exclusion of introduced mammals affected subsequent seedling establishment in montane stands of invasive P.

Introduced rodents and possums in New Zealand eat flowers, fruits, seeds and seedlings, but little is known about their impact on forest regeneration. We investigated seedling establishment in exclosures with mesh of two different sizes to exclude (1) possums and (2) possums and rats, at two mainland forest sites (beech–podocarp–broadleaved and second-growth broadleaved–podocarp) near Dunedin. We recorded all new woody seedlings that established over the next 2 years.

Bone-seed, Chrysanthemoides monilifera ssp. monilifera (L.), is an environmental weed of coastal vegetation communities scattered throughout New Zealand. To assess the long-term implications for native forest regeneration in sites where bone-seed is present, we selected four study sites around Wellington, New Zealand, where bone-seed was abundant. We compared seed bank composition in bone-seed-invaded sites with nearby native forest patches, and monitored bone-seed and native seedling recruitment with and without control of mature bone-seed plants.

Norway rats (Rattus norvegicus) were eradicated from Ulva Island, Rakiura National Park, in 1996. The aim of our work was to determine if seedlings and saplings increased in density and/or species richness following this eradication. In 2003, we took advantage of eight permanent plots (5 × 5 m) that had been established on Ulva Island in 1991, by counting seedlings and saplings of woody species, including tree ferns. Over this period, total numbers of woody seedlings (< 30 cm tall), and saplings (30 cm – 2 m tall) did not increase significantly (P > 0.05).