Effects of tree control method, seed addition, and introduced mammal exclusion on seedling establishment in an invasive Pinus contorta forest

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. contorta. Tree control method had a significant effect on seedling establishment: felling trees promoted establishment of P. contorta seedlings, whereas poisoning trees favoured establishment of native seedlings (provided seeds were available). Native seedling establishment was higher where seeds were sown, indicating native seed limitation at these sites. Excluding introduced mammals increased P. contorta seedling establishment, but did not have a significant effect on native seedling establishment. Our results indicate that poisoning P. contorta is a better management approach than felling where native seedling establishment is the desired outcome, and that this outcome can be enhanced by sowing native seed