Assisted natural regeneration accelerates recovery of highly disturbed rainforest

Abstract

Summary Large areas of rainforests in Australia and other tropical regions have been extensively cleared since the mid‐19th century. As abandoned agro‐pastoral land becomes increasingly prominent, there is an ongoing need to identify cost‐effective approaches to reinstate forest on these landscapes. Assisted regeneration is a potentially lower cost restoration approach which aims to accelerate forest recovery by removing barriers to natural regeneration. However, despite being widely used its ecological benefits are poorly quantified, particularly on long cleared and grazed land. This study quantified the benefits of assisted regeneration on previously cleared land in a subtropical rainforest ecosystem within eastern Australia. Three different site types were used (grazed, grazing excluded and grazing excluded plus assisted regeneration, each with a maximum distance of 120 m to remnant forest) to compare forest recovery up to 10 years after grazing was relieved with and without 4–6 years of assisted regeneration. Assisted regeneration sites showed a threefold increase in canopy cover, fourfold increase in native tree and shrub species richness and over 40 times greater native stem density compared to nonassisted regeneration sites. Stimulation of native recruitment appears dependent on the simultaneous removal of multiple barriers to regeneration, with the exclusion of grazing alone insufficient. This demonstrates the additional ecological benefits arising from investment in assisted regeneration. It offers considerable promise as a cost‐effective tool for accelerating and improving reinstatement of forest on retired agro‐pastoral land in the humid subtropics.

Recovery of decomposition rates and decomposer invertebrates during rain forest restoration on disused pasture

“…Nevertheless, the lack of difference in outcomes of passive and active restoration in our study was consistent with these suggestions. Uebel et al (2017) found that ANR accelerated the early recovery of physical vegetation structure in the same study location as our study. However, we found no effect of differing age of ANR sites (1-3 versus 5-10 years) on the return of either decomposition rates or invertebrate decomposer communities.…”

“…At the time of the present study, the woody vegetation types were a mix of old‐growth forest (both rain forest and eucalypt forest) unmanaged successional (regrowth) vegetation, and areas of this regrowth which additionally had been targeted for assisted natural regeneration (ANR) during the previous decade, by the managers of the Numinbah Conservation Area. The unmanaged regrowth was characterized by relatively short trees and shrubs that provided a sparse canopy cover, with a high proportion of non‐native species, most notably the shrub Lantana camara (Uebel et al., ). The ANR interventions aimed to accelerate regeneration of native trees, mainly by suppressing L. camara and other non‐native plants using various cutting and herbicide applications, until seedlings and saplings of native trees had grown to close the canopy (Uebel et al., ).…”

“…In such instances, a passive restoration approach of simply excluding livestock to allow unassisted recovery may not be sufficient, and active restoration may be needed to assist natural regeneration (Chazdon, ). Assisted natural regeneration (ANR) approaches aim to accelerate recovery by removing barriers to forest redevelopment such as seedling predation by livestock or competition from invasive plants (Elliott, Blakesley & Hardwick, ; Uebel, Wilson & Shoo, ).…”

The Long-Term Survival and Growth of Enrichment Plantings in Logged Tropical Rainforest in North Queensland, Australia

“…On degraded sites, the basic principle of ANR is to protect and facilitate the growth of parent trees and regeneration [45]. In Australia, controlling non-native weeds and eliminating grazing has proved successful in regenerating highly disturbed rainforest [46]. Protecting roots and suckers also proved successful in rehabilitating slash-and-burn agricultural sites in the Democratic Republic of the Congo [47].…”

Disentangling effects of local and landscape variables on attractiveness of restored gravel‐sand pits for bat foraging activities

“…Some authors highlight expensive costs associated with active restoration (Catteral and Harrison Catterall & Harrison, 2006), while others suggest that passive restoration is laden with unrecognised costs and only slowly reaches its objectives (Zahawi, Holl, & Reid, 2014). The debate is still ongoing, but Prach and del Moral (2015) suggest that criteria to choose between passive, intermediate (Uebel, Wilson, & Shoo, 2017) and active restoration may depend on the landscape. Yet, relatively few studies have simultaneously considered within site (i.e., local variables such as habitat, age, etc.)…”