Establishment of tree seedlings in the understory of restoration plantations: natural regeneration and enrichment plantings

Abstract

Little is known about the potential of restoration plantations to provide appropriate understory conditions to support the establishment of seeds arriving from neighboring native forests. In this article, we investigated how seedling establishment is affected in the understory of restoration sites of different ages and assessed some of the potential environmental factors controlling this ecological process. We first compared the density and richness of native tree seedlings among 10‐, 22‐, and 55‐year‐old restoration plantations within the Atlantic Forest region of southeastern Brazil. Then, we undertook a seed addition experiment in each study site, during the wet season, and compared seedling emergence, survival, and biomass on local versus old‐growth forest soil (transferred from a reference ecosystem), in order to test whether local substrate could hamper seedling establishment. As expected, the oldest restoration site had higher density and richness of spontaneously regenerating seedlings. However, seedling establishment was less successful both in the oldest restoration planting and using substrate transferred from a reference ecosystem, where emergence and survival were lower, but surviving seedlings grew better. We attribute these results to lower light availability for seedlings in the understory of the oldest site and speculate that higher incidence of pathogens on old‐growth forest soil may have increased seedling mortality. We conclude that the understory of young restoration plantations provides suitable microsite conditions at the early establishment phases for the spontaneous regeneration or enrichment planting of native trees.

Evaluating climber cutting as a strategy to restore degraded tropical forests

“…Enrichment planting has long been suggested as a method to reintroduce tree species in remnant forests for commercial timber production (Lamb et al, 2005), but is yet poorly tested in restoration (Bertacchi et al, 2016). In our study, enrichment planting resulted in low survival rates (b20%), which may be a direct consequence of the high canopy cover (N70%) in both climber cutting and control plots.…”

“…This benefit was only obtained, however, when enrichment planting was implemented right after climber cutting. These results suggest that for enrichment planting to be successful, plantings should be concentrated in large gaps where light levels are higher or ongoing overstory clearing will be necessary (Bertacchi et al, 2016;Martínez-Izquierdo et al, 2016).…”

“…Nevertheless, restoration projects usually focus on planting trees in completely deforested areas, despite the fact that active restoration is expensive and rarely reaches biodiversity levels of reference sites (Suganuma and Durigan, 2015;Shoo et al, 2016). In contrast, few resources are directed to improve existing forest remnants through management and enrichment plantings (Bertacchi et al, 2016).…”

Phenotypic plasticity and local adaptation favor range expansion of a Neotropical palm

“…We observed in the field that seedlings from the Semideciduous population were more subjected to damping off than seedlings of the local provenance. Soil pathogens exert a substantial impact on tree seedling survival (Bertacchi et al., 2016; Mangan et al., 2010), so differential tolerance to pathogens may also be related to local adaptations (Thrall, Burdon, & Bever, 2002). The aforementioned speculations were presented here to contextualize the results of reciprocal transplants in relation to the regeneration conditions of the ecosystems we studied, but need to be experimentally tested to infer the mechanistic ecological processes driving the observed results.…”

Excessive Accumulation of Chinese Fir Litter Inhibits Its Own Seedling Emergence and Early Growth—A Greenhouse Perspective

“…Following this trend, one major aim of sustainable forest management is to convert forest plantations into naturally regenerating, and diverse ecosystems [5][6][7][8]. Natural regeneration is considered the backbone for sustainable forestry, and failure to establish natural regeneration hampers the efforts toward sustainable forest management [9,10]. Therefore, understanding the factors that control tree regeneration is a major research priority for forest managers worldwide [11,12].…”