Applied nucleation facilitates tropical forest recovery: Lessons learned from a 15‐year study

Abstract

1. Applied nucleation, mostly based upon planting tree islands, has been proposed as a cost-effective strategy to meet ambitious global forest and landscape restoration targets. 2. We review results from a 15-year study, replicated at 15 sites in southern Costa Rica, that compares applied nucleation to natural regeneration and mixed-species tree plantations as strategies to restore tropical forest. We have collected data on planted tree survival and growth, woody vegetation recruitment and structure, seed rain, litterfall, epiphytes, birds, bats and leaf litter arthropods.

Drivers of oak establishment in Mediterranean old fields from 25-year-old woodland islets planted to assist natural regeneration

“…The differences and similarities among these various studies may depend on distances between the forest edge and open old fields, as well as on abundances of predators and acorn dispersers. Regardless of these variations across studies of forest regeneration, they make clear that such regeneration in Mediterranean climates is a multi-decade process, even when assisted by woodland islets especially when compared with forests of high primary productivity, such as tropical forests, which show recruitment rates of 100 seedlings ha −1 yr −1 (Holl et al 2017(Holl et al , 2020.…”

“…Later researchers have referred to this approach as "tree islands" or "applied nucleation" (Corbin and Holl 2012;Zahawi et al 2013;Piiroinen et al 2015), "dispersion and attraction nuclei" (García-Martí and Ferrer 2013) or "tree clumps" (Stanturf et al 2014). This approach has been implemented in various restoration actions (Robinson and Handel 2000;Dendy et al 2015;Corbin et al 2016;Ramírez-Soto et al 2018;Shaw et al 2020), yet few studies have addressed the long-term effectiveness of woodland islets for facilitating forest restoration or the factors that may compromise that effectiveness (Rey- Rey-Benayas and Bullock 2015;Corbin et al 2016;Holl et al 2020).…”

“…The woodland creates a heterogeneous environment for new plants beyond the woodland itself, and factors and processes controlling plant recruitment may operate differently at locations near or far from islets (Rey- Benítez-Malvido et al 2018;Holl et al 2020). For example, seeds produced by islets can be dispersed at a wide range of distances from them (Corbin et al 2016).…”

Functional robustness of seed dispersal by a remnant frugivore population on a defaunated tropical island

“…Harnessing this phenomenon for restoration has been proposed as an alternative to traditional plantation‐design reforestation approaches (Corbin & Holl, 2012). Notable advantages of disperser‐induced nucleation over plantation‐based approaches are that the former method is substantially cheaper and can produce a more heterogeneous landscape (Holl et al, 2020). Furthermore, our results support evidence that generalist, omnivorous bird species, possibly due to their propensity to forage or roost in open habitat, may be ideal dispersers within applied nucleation scenarios (Carlo & Morales, 2016; González‐Varo et al, 2017; Wunderle, 1997).…”

Large canopy and animal‐dispersed species facilitate natural regeneration in tropical forest restoration

“…Persistence of ecosystems under restoration is challenging because drivers of degradation are sometimes beyond practitioners' control (Reid et al 2017). Alternatively, other drivers of restoration fate, such as planted species composition and traits, can be more easily manipulated in restoration projects and influence restoration success (Fink et al 2009; Martínez‐Garza et al 2013; Schweizer et al 2015; Holl et al 2020). Planted species' traits affect light interception (Almeida & Viani 2019), native tree recruitment and development (De Pena‐Domene et al 2016; Galindo et al 2017; Li et al 2018), seed dispersal visitation (Fink et al 2009), and community resilience (Timpane‐Padgham et al 2017).…”