Traits or habitat? Disentangling predictors of leaf‐litter decomposition in Amazonian soils and streams

Abstract

Quantifying the relative contributions of plant physicochemical traits and environmental conditions to leaf decomposition is essential to increase our understanding of ecosystem processes in forested terrestrial and aquatic habitats. This is particularly crucial in tropical rainforests that display high levels of tree diversity and environmental heterogeneity over relatively small spatial scales. For example, in Amazonia, detritus from hundreds of tree species fuels carbon cycling in watersheds, but much remains to be learned about how species traits interact with environmental conditions to mediate decomposition. We investigated the leaf‐litter decomposition of 17 tree species with contrasting traits in soil and stream habitats in Yasuní National Park, Ecuador. We hypothesized that (1) habitat type would be the major determinant of leaf decomposition (faster in stream than soil systems), (2) species would be ranked similarly in terms of leaf decomposition rates, according to decomposability traits (i.e., litter quality), within each habitat, and (3) the variability of leaf decomposition within habitats would be greater for soil than for stream systems. Contrary to our first hypothesis, we found that leaf‐litter decomposition rates for any given tree species were similar in stream and soil systems. However, we found that the relative importance of litter traits for decomposition such as concentrations of micronutrients (Mn and Cu, in particular) was consistent across habitats. Finally, we found that decomposition was equally highly variable in both terrestrial and aquatic systems. This variability was explained by differences in microhabitat within soils, but appeared to be more stochastic in streams. Overall, we found that plant traits had an overwhelming effect on the decomposition process in the intertwined aquatic and terrestrial matrices of the Yasuní rainforest, with significant effects of microhabitat features. This study sheds light on the fate of the pool of dead organic matter in tropical rainforests and highlights the need for further studies of the mechanisms underlying microhabitat variability.

Average leaf litter quality drives the decomposition of single-species, mixed-species and transplanted leaf litters for two contrasting tropical forest types in the Congo Basin (DRC)

“…However, the diversity of litter (Gartner and Cardon 2004;Hättenschwiler et al 2005;Oliveira et al 2019) and the local decomposition environment (Jewell et al 2015;Joly et al 2017) both have been shown to further impact the decomposition process, yet their relative contribution remains poorly documented. Most studies addressing the drivers behind the variability in litter decomposition under tropical rainforests have been carried out in the Amazon Basin (Hättenschwiler et al 2011;Nottingham et al 2018;Oliveira et al 2019;Four et al 2019). Several decomposition studies have been conducted in Central Africa (Bernhard-Reversat and Schwartz 1997;Torti et al 2001;Chuyong et al 2002;Peh 2009;Peh et al 2012), yet we still have a limited understanding of the decomposition process and its drivers for major African rainforest types, especially in the Democratic Republic of the Congo.…”

Leaf Decomposition in an Intermittent Stream: Channel vs. Riparian Area

“…low lignin contents are generally expected to exhibit fast decomposition rates, both in aquatic [22][23][24] and terrestrial systems [24][25][26]. The visible, although non-significant, trend in fungal biomass (alder > chestnut > oak) in the riparian area seems to express such intrinsic litter quality differences.…”

Litter mixture effects on decomposition change with forest succession and are influenced by time and soil fauna in tropical mountain Andes

“…This latter was done by opening 6 mm diameter holes in each corner of the bag, thus ensuring the access of macrofaunal decomposers but preventing losses of litter caused by the holes (Salinas et al, 2011). The All the litter material was collected in the study sites from freshly fallen senescent leaves, discarding those with conspicuous damages such as fungal infections, insect galls or high herbivory (>30%), as well as very bright young leaves and highly rooted leaves with extended necrotic area (Cardenas et al, 2017;Four et al, 2019). The collected litter material was oven-dried at 60 °C during 72 h and weighted using a 0.1 mg precision scale (LX 220A scs) to measure the initial and final weights.…”