Ryan Veryard

and 10 more

Old-growth forests in Southeast Asia are dominated by trees of the Dipterocarpaceae family which are targeted by selective logging. Their traits (supra-annual mast fruiting, limited dispersal, and recalcitrant seeds that form no seed bank) mean they can have poor natural regeneration rates in some selectively logged forests. Enrichment planting is commonly used to overcome recruitment limitation and increase restoration success. However, it is still unclear what factors influence the success rate of planted seedlings, including the characteristics of the surrounding tree matrix and local neighbourhood. Here, we examine the growth and survival of 721 enrichment line-planted seedlings within 24 plots of the selectively logged forest of the Sabah Biodiversity Experiment, in Malaysian Borneo, in relation to their species identity and local neighbourhoods. We mapped the spatial location, size, and identity of nearly 5,000 surrounding matrix trees (≥ 10 cm diameter at breast height (DBH)) within a 10 m radius of focal planted seedlings in 2012 and 2015. We analysed levels of tree density-dependence, asymmetric competition with naturally occurring trees, and confamilial density-dependence for each seedling. Survival and growth rates of enrichment planted seedlings were positively associated with canopy openness and total basal area of the surrounding tree matrix. These results were consistent between two planting cohorts. Increased survival and growth of enrichment planted seedlings in areas of the Sabah Biodiversity Experiment with higher canopy openness (up to around 40%) is consistent with understory light as a limiting resource. The unexpected higher survival and growth of enrichment planted seedlings in forest areas with higher basal area of unlogged remnant trees may be explained by the logging-induced creation of patches with varying local conditions, with those less heavily impacted by logging containing more naturally occurring trees, greater moderation of extreme high temperature and low humidity, more established mycorrhiza and reduced soil compaction.