Leaf litter decomposition rates in degraded and fragmented tropical rain forests of Borneo

Abstract

Previously extensive tracts of primary rain forest have been degraded by human activities, and we examined how the effects of forest disturbance arising from habitat fragmentation and commercial selective logging affected ecosystem functioning in these habitats by studying leaf litter decomposition rates in litter bags placed on the forest floor. The rain forests of Borneo are dominated by trees from the family Dipterocarpaceae, and we compared leaf litter decomposition rates of three dipterocarp species at eight forest fragment sites (area 3-3529 ha) that had different histories of disturbance pre-fragmentation: four fragments had been selectively logged prior to fragmentation and four had been formed from previously undisturbed forest. We compared these logged and unlogged forest fragments with sites in continuous forest that had been selectively logged (two sites) and fully protected and undisturbed (two sites). After 120 d, undisturbed continuous forest sites had the fastest rates of decomposition (52% mass loss). Forest fragments formed from unlogged forest (32% mass loss) had faster decomposition rates than logged forest fragments (28% mass loss), but slower rates than continuous logged forest (39% mass loss). Leaves of a light-demanding species (Parashorea malaanonan) decomposed faster than those of a shade-tolerant species (Hopea nervosa), but decomposition of all three dipterocarp species that we studied responded similarly to logging and fragmentation effects. Reduced decomposition rates in logged and fragmented forest sites may affect nutrient cycling and thus have detrimental consequences for forest regeneration. Conservation management to improve forest quality should be a priority, particularly in logged forest fragments.Abstract in Malay is available with online material.

Land use not litter quality is a stronger driver of decomposition in hyperdiverse tropical forest

“…Our study shows that a major driver of litter decomposition was land-use change and that substantial differences in litter quality associated with selectively logged and old-growth forest had no significant effect. We also discovered faster decomposition rates in undisturbed forest compared to selectively logged forest, which supports both our first hypothesis and previous work in a similar system (Yeong, Reynolds, & Hill, 2016). In general, decomposition was slow compared to other studies in tropical forests (Hättenschwiler, Coq, Barantal, & Handa, 2011;Powers et al, 2009) but comparable to mass loss reported by Mayor and Henkel (2006).…”

Tropical forests are thermally buffered despite intensive selective logging

“…This is contrary to expectations from previous studies (Ball, Lindenmayer, & Possingham, ; Blakely & Didham, ). However, high volumes of deadwood could be maintained in logged forest by lower decomposition rates (Ewers et al., ; Yeong, Reynolds, & Hill, ; but see Hérault et al., ), and large remnant pieces from harvest operations. In undisturbed forests, tree holes tend to be associated with larger, older trees (Blakely & Didham, ; Lindenmayer, Cunningham, Pope, Gibbons, & Donnelly, ).…”

“…This is contrary to expectations from previous studies (Ball, Lindenmayer, & Possingham, 1999;Blakely & Didham, 2008). However, high volumes of deadwood could be maintained in logged forest by lower decomposition rates Yeong, Reynolds, & Hill, 2016; (Edwards, Tobias et al, 2014), increased wind in gaps (Chen, Franklin, & Spies, 1995) and remnant large trees that were specifically avoided by logging companies because of hollow boles. In addition, we assessed tree holes in the understorey only, and differences may well manifest at higher forest strata.…”

Strong but taxon‐specific responses of termites and wood‐nesting ants to forest regeneration in Borneo

“…The research showing this is scanty, but there is evidence that decomposition rates are slower in disturbed (Didham ) and logged forest fragments (Yeong et al . ) compared with old growth forest. Furthermore, dead wood is proportionally more important for carbon storage in logged forest areas than in old growth areas (Pfeifer et al .…”

“…Longer deadwood residence times may mean that there is more unsuitable wood for termites and fungi, but also more suitable wood for generalist ants, which could lead to indirect competition for dead wood. The research showing this is scanty, but there is evidence that decomposition rates are slower in disturbed (Didham 1998) and logged forest fragments (Yeong et al 2016) compared with old growth forest. Furthermore, dead wood is proportionally more important for carbon storage in logged forest areas than in old growth areas (Pfeifer et al 2015).…”