Contribution of nucleation techniques to plant establishment in restoration projects: an integrative review and meta‐analysis

Abstract

Nucleation practices combine several techniques that use small nuclei of vegetation as starting points of vegetation regeneration and serve as an integrated approach to improve environmental conditions and promote the establishment of species in degraded lands. We performed an integrative review and a meta‐analysis to test which nucleation techniques better improve plant establishment in restoration projects. We compared the efficiency of single and combined nucleation techniques including topsoil or litter transposition, bird perches, island planting (nuclei), and brushwood. A total of 374 studies published between 1993 and 2021 were evaluated; 73 studies were included in the integrative review and 35 studies enabled effect size calculation. The most common metrics used to measure restoration outcomes were the evaluation of seedling richness, density and abundance, topsoil transposition techniques, transposition of litter or seed bank (41% of the studies), and bird perches (35% of the studies). Among the sources of disturbance, agriculture for food production was the most frequent activity reported. Overall, we detected strong and positive effects of nucleation techniques on seedling parameters, with increased seedling richness and seedling survivorship compared to control areas. Stronger effects on plant richness were found for tropical compared to temperate forests. Restoration techniques differed in their ability to improve seedling richness, but the combination of topsoil transposition and bird perches enhanced seedling richness the most. Our results suggest that the use of nucleation techniques in ecosystem restoration is an efficient tool to increase the richness and establishment of plants (seedlings) in areas under restoration.