Seedling diversity in actively and passively restored tropical forest understories.

Abstract

Alternative methods for restoring tropical forests influence the ecological processes that shape recruitment of understory species. In turn, the traits of species recruited will influence the ecological processes the forests provide now and over the long term. We assess the phylogenetic and functional structure of seedlings beneath monoculture plantations, mixed-species plantations (both active restoration) and regenerating selectively logged native forests (passive restoration), considering traits of specific leaf area (SLA, including within-species variation), leaf nitrogen and phosphorus content, life-form, potential plant height, and dispersal type. Monoculture plantations comprised seedlings that were more closely related then would be expected by chance (i.e., phylogenetically clustered), and regenerating forest contained species more distantly related then would be expected by chance (i.e., phylogenetically overdispersed). This suggests that seedlings beneath monocultures assemble through environmental filtering and through the dispersal limitation of predictable functional guilds. However, dispersal limitation is frequently overcome by human-assisted dispersal, increasing trait diversity. Comparing SLA values revealed that regenerating forests recruit seedlings with both high and low mean and variation of SLA, leading to higher overall diversity. Regenerating forest seedlings showed signs of environmental filtering, only based on within-species variation of SLA. Regenerating forest understories appear to favor species that show a high intraspecific variation in SLA values (e.g., Pterocarpus indicus Willd.) and at the same time provided habitat for later successional seedlings that show a lower intraspecific variation in SLA (e.g., Canarium luzonicum (Blume) A.Gray). This trait diversity suggests limiting similarity or competitive exclusion may be reduced because of niche differences, allowing species with different traits to coexist. Phylogenetic and functionally distinct species are restricted in their regeneration capacity, many of which are of conservation significance (under the IUCN Red List). Reforestation projects should maximize desired ecological services (including conservation value) by actively managing for the recruitment of species that are phylogenetically and functionally (including intraspecifically) distinct. This management aim will increase the probability of fulfilling a wider array of niche spaces and potentially increase the diversity of ecosystem services provided.

Seedling diversity in actively and passively restored tropical forest understories

“…Additional supporting information may be found online at: http://onlinelibrary.wiley.com/doi/10.1002/eap.2286/full DATA AVAILABILITY Data used in the manuscript are available from The University of Queensland Repository UQ eSpace (Wills 2020) Vol. 31,No.…”

“…Data used in the manuscript are available from The University of Queensland Repository UQ eSpace (Wills 2020) at: https://doi.org/10.14264/uql.2020.999…”

Canopy cover and ecological restoration increase natural regeneration of rainforest trees in the Western Ghats, India

“…Previous studies have shown that both mixed‐native species plantations and monocultures of native or non‐native species can facilitate natural regeneration to different levels (Harikrishnan et al 2012; Onyekwelu & Olabiwonnu 2016; Nerlekar et al 2019; Trujillo‐Miranda et al 2021; Wills et al 2021). However, studies assessing patterns and drivers of natural regeneration across different types of tree plantations are rare (but see Farwig et al 2009; Jayawardhane & Gunaratne 2020; Wills et al 2021). If facilitation of natural regeneration is primarily through abiotic changes due to increased shade, then regeneration would be expected to increase with canopy cover both within and across plantation types.…”