Short‐term responses in a secondary tropical forest after a severe windstorm event

Abstract

Questions:How do abiotic conditions, forest structure, as well as taxonomic and functional diversities and composition recover after wind-generated treefalls? Do young and old-growth secondary forests differ in their responses?Location: Mandai region of the Central Catchment Nature Reserve, Singapore, where extensive treefalls occurred during an unusually powerful windstorm in 2011. Southeast Asia.Methods: Soil nitrogen, phosphorous, potassium, canopy cover, leaf litter depth, coarse woody debris, and woody stems ≥1-cm diameter were measured and identified in 10 × 10 m plots. Twenty-six plots were located in treefall areas and 14 plots were located in relatively unaffected areas, with equal numbers in young and old-growth secondary forest types. The first round of surveys took place within 3-6 months of the windstorm event and yearly re-surveys were conducted until 2015. Specific leaf area, leaf dry matter content, leaf thickness, woody density, maximum plant height, and seed dry mass were measured or derived from various sources. Results:There was a pulse of soil nutrient availability in both affected and unaffected areas 1 year after the wind event. Canopy cover and basal area in the affected areas recovered to similar levels as unaffected areas by the second year, and coarse woody debris by the fourth year. In affected plots, taxonomic and functional diversities increased and overshot that of-and taxonomic composition diverged from-unaffected plots after the second year. Young and old-growth secondary forest types mainly differed in the taxonomic composition of new recruits. However, there was no evidence of changes in functional composition towards resource-acquisitive strategies such as lower wood density or higher specific leaf area. Conclusions:Abiotic conditions and basal area recovered rapidly within 2-4 years after the windstorm. Taxonomic composition in young and old-growth affected forests both diverged from unaffected forests but also from each other over time. K E Y W O R D Sblowdown, community composition, edaphic conditions, extreme weather, longitudinal study, plant functional traits, regeneration trajectory, tropical forest, wind disturbance, windthrow | 721 N. (2014). Seven-year responses of trees to experimental hurricane effects in a tropical rainforest, Puerto Rico. Forest Ecology and Management, 332,[64][65][66][67][68][69][70][71][72][73][74]. https ://doi.

Functional traits that moderate tropical tree recruitment during post‐windstorm secondary succession

“…On 11 February 2011, strong winds of >60 km/hr damaged an estimated forest area of 40 ha, causing high levels of tree fall, canopy openings, and increased fluxes in coarse woody debris (CWD), leaf litter and soil nutrients (Yee et al, 2019). Within 3 months following the windstorm, we established twenty eight 10 × 10 m plots that were randomly located in blowdown areas delimited by the National Parks Board from an aerial survey ( Figure S1; Yee et al, 2019). The minimum distance between plots was 40 m. Five annual censuses were carried out between April and August in 2011-2015.…”

“…Canopy gaps and debris deposition following the wind disturbance generated high spatial and temporal heterogeneity in light and edaphic resources, which allowed the rapid seedling and sapling recruitment from a diverse number of species (Yee et al, 2019).…”

“…We specifically focus on recruitment instead of total abundance because abundance changes in a longitudinal study also includes mortality, which may be moderated by a different set of traits than recruitment. In addition, during the first 5 years of succession post-disturbance, recruitment was the main driver of abundance (Yee et al, 2019).…”

Non-additive biotic interactions improve predictions of tropical tree growth and impact community size structure

“…We assumed all recruits to begin at DBH = 1 cm and then calculated both A j and A k as the initial neighbourhood densities. We then used parameters inferred from both the 'direct-interaction-only' model (Equation 5) and the 'HOI-inclusive' model (Equation 6) to simulate individual diameter growth of focal species under the three recruitment scenarios at daily timesteps over two years-the time taken for canopy closure in our study site (Yee et al 2019).…”

“…Tropical tree communities naturally meet these conditions under which HOIs are predicted to prevail, yet studies that test for HOIs remain scarce in this system. Tropical forests are known for their high primary productivity (Gillman et al 2015) and biomass accumulation rate during succession (Poorter et al 2016), which lead to rapid canopy closure that imposes strong light limitation to the understorey (van Breugel et al 2013;Yee et al 2019). While HOIs can already arise from the nonlinear size-growth response of tree individuals to light extinction due to increasing neighbour densities, the fact that size itself also determines how much light is depleted through shading allows even more room for intermediary species to modify pairwise interactions and give rise to HOIs.…”