Thinning enhances success of enrichment planting with selected tree species under a pure stand of Leucaena leucocephala

Abstract

Increasing the biodiversity of Leucaena leucocephala (hereafter leucaena) stands without losing the benefits provided by the forest structure is a challenge for adaptive management. Here, we report the survival and growth (height, stem, and canopy diameter) of five Atlantic Forest tree species planted underneath a pure stand of the exotic leucaena, which was broadcast sown 35 years before in a 0.6 ha area. Two treatments were compared: thinning (cutting all leucaena trees in 4‐m wide rows, where seedlings were planted) and control (seedlings planted under leucaena canopy), with four replicates each (20 seedlings per plot, four per species, 2‐m spaced). The five species selected were long‐lived emergent trees from seasonal forests, with broad canopy, evergreen, and shade‐tolerant. These traits were expected to allow their survival and growth, and, later on, to shade out the leucaena trees. Seven years after planting, survival was high for all species (around 80%), not differing between treatments or species. On average, stem diameter, height, and crown diameter were, respectively, 69, 44, and 36% higher in thinned than in control plots. Response to thinning differed between species in growth, with Gallesia integrifolia and Luehea divaricata standing out. Our results demonstrate that the species used for enrichment planting, selected by their suitable functional traits, can successfully survive under leucaena stands. Reducing competition by thinning, however, is crucial to enhance their growth. Despite the benefits from thinning, enrichment success strongly depends, therefore, on the abilities of the species selected to face the ecological filters acting on the target ecosystem.

Chemical Thinning and Fisheye Clip for Managing Light Intensity in the Understory of Forest Restoration

“…Alternatively, chemical thinning can be applied to suppress invasive or unwanted trees in forest management [28,29] leading to standing death in most cases. Chemical thinning consists of applying herbicide in a cut made in the main stem [29,30], aiming to remove target trees by standing death [31]. Less impact is created in the understory, and the managed individuals might either resprout or temporarily continue to serve as shelter for the fauna, such as birds, insects, and small mammals, as they fall gradually [32].…”

Allelopathic potential of Leucaena leucocephala (Lam.) de Wit leaf extracts on native species

“…Leucaena leucocephala (Lam.) de Wit (leucaena) is a small tree species belonging to the Fabaceae family and native to Central America (Oliveira et al, 2023b). The species was used in Brazil for the reforestation of degraded areas, animal feeding, and green manure (Prates et al, 2000).…”

“…Since the introduction processes began, leucaena has been presenting problems worldwide, including in Brazil (Silva and Silva-Forsberg, 2015). The species overlap with native species, presenting rapid development and high reproduction capacity (Oliveira et al, 2023b), including successive regrowths after cutting (Costa and Durigan, 2010). Considering that leucaena has become invasive of fragments of native areas, the study of this species' allelopathic effects on native tree plants becomes essential.…”