Unpalatable neighbours reduce browsing on woody seedlings

Abstract

High levels of browsing by mammalian herbivores can negatively affect the survival and growth of seedlings, and consequently revegetation and forest regeneration outcomes. Typical forms of protection (e.g. tree guards and fencing) are costly, particularly when used in large-scale projects, therefore, low-cost alternatives are needed. Based on associational refuge theory, we assessed the revegetation technique ‘cryptic planting’, whereby woody seedlings are planted within the foliage of unpalatable plants to deter browsing. We established a trial where 432 six-month-old tubestock of three woody species (Eucalyptus camphora, Melaleuca squarrosa and Leptospermum lanigerum) were cryptically (within the foliage perimeter of unpalatable plants) or non-cryptically planted across three wetland forest sites. The plants were left for four weeks before being scored for browsing damage based on an estimate of biomass removed. To further assess cryptic planting, we surveyed 352 plants of the same three woody species two years after they were planted cryptically or non-cryptically at the same three sites, and surveyed each plant for browsing damage. Overall, cryptic planting reduced browsing damage from 37% to 22%, and from 51% to 23%, in the trial and survey, respectively. E. camphora plants were particularly susceptible to browsing. These results suggest that cryptic planting provides an alternative to costly tree guards and fencing and can be used to reduce browsing on woody seedlings.