Next‐generation tropical forests: reforestation type affects recruitment of species and functional diversity in a human‐dominated landscape

Abstract

Summary In tropical countries where little natural forest remains, such as the Philippines, small‐holder monocultures and mixed‐species plantations potentially provide conservation values by providing habitat for local fauna and recruiting diverse understorey species. However, little information exists as to whether monocultures offer a framework to kick‐start understorey species recruitment and how this compares to mixtures. In this study, species and trait diversity were measured within the understories of three different forest types on the Island of Leyte, Philippines: mixed‐species forests (known as ‘Rainforestation Farming’), Swietenia macrophylla monocultures and regenerating selectively logged forests. All plants less than 2 m in height were identified, and dispersal type, fruit type, seed and fruit size were extracted from literature and online data bases. We found that overall seedling richness and diversity were lower within the monoculture forests compared with the regenerating selectively logged forests, with the Rainforestation forests showing intermediate seedling diversity, including trait diversity. Monoculture understories had a higher proportion of large fruited domesticated species that are likely dispersed by people and significantly lower wind‐dispersed native seedlings than the other forest types. Higher understorey diversity was generally negatively correlated with soil nutrients and positively correlated with increased leaf area index, that is more canopy cover. Our results confirm that mixed‐species plantations and regenerating selectively logged forests recruit higher species diversity, but we also found evidence that monocultures can recruit diverse species in the understorey. However, monoculture understories were depauperate of native wind‐dispersed traits that are often important emergent species in tropical rain forests. Synthesis and applications. Overall, our results show that just having trees in a cleared landscape provides conservation value, but if monocultures are used as less costly and technically simpler solutions for initiating recruitment, then wind‐dispersed native species (e.g. species from the Dipterocarpaceae family) in addition to other limited functional traits (e.g. large‐seeded species) should be planted to enhance long‐term survival of ecologically significant native tree populations.

Effects of restoration on tree communities and carbon storage in rainforest fragments of the Western Ghats, India

“…First, our results suggest that while active restoration could drive consistent recovery of indicators directly related to specific interventions, the recovery of indicators not directly related to the interventions may be weaker and more variable. For example, planting native trees in AR plots had a strong direct effect on tree density (69% recovery toward BM targets), but indirect effects on indicators that might be influenced by changes in tree density and diversity, such as height-diameter ratios (Osuri et al 2014) and regeneration of late-successional species (Wills et al 2017), were weaker and more variable. Estimates of recovery in restored forests, and of the efficacy of active versus passive restoration interventions, can therefore vary markedly depending on what types of indicators are prioritized in assessments of restoration success.…”

Incorporating natural regeneration in forest landscape restoration in tropical regions: synthesis and key research gaps

“…Remnant forest patches do not need to be pristine to host many important generalist seed dispersers (Wills et al . ). For example, in large regenerating areas in Kibale National Park, Uganda, mammal communities, including a number of primate species, recovered within 20 years of agricultural abandonment.…”

Restoration of soil microbes and organic matter through tropical reforestation

“…As such, we speculate that dispersal of ECM fungi into plantation sites is necessary but restricted and limits the capacity for complete soil microbial restoration if tree planting is not accompanied by ECM inoculation of plantation seedlings (Aggangan et al, 2012). As the rainforestation plantations were established with some Dipterocarp trees, such that 11 out of 77 canopy species were Dipterocarps in 2006 , and had since recruited more in the understory (Wills et al, 2016), a lack of ECM inocula may be a major constraint to their capacity to restore soil microbial function and composition.…”

“…Typic Paleudults). In total, 25 sites were sampled, distributed across 15 locations spanning approximately 100 km from north to south, each at least 2 km from its nearest neighbour, with sufficient interspersion among plantation types to mitigate spatial autocorrelation effects (Wills et al, 2016). …”

“…Understory plant community For a subset of sites (4 of 5 sites for each of mahogany and rainforestation plantations and all 5 reference forest sites), understory plant traits were also assessed as described by Wills et al (2016), using methods based on those established by Herbohn et al (2014 were collected following standard protocols (Pérez-Harguindeguy et al, 2013). LNC and LPC were determined using a single digestion method, which used a colorimetric determination of LNC, using the salicylate-hypochlorite method (Baethgen and Alley, 1989), and LPC using an adaptation of a single solution method (Anderson and Ingram, 1989) used by Murphy and Riley (1962).…”