Impact of Simulated Changes in Water Table Depth on Ex Situ Decomposition of Leaf Litter from a Neotropical Peatland

Abstract

Although water table depth is commonly regarded as the primary determinant of litter decomposition rate in tropical peatlands, this has rarely been tested experimentally. This study explored the influence of flooding on decomposition of litter from three dominant plant species in a neotropical peatland. The non-flooded treatment reduced the mass remaining after 14 months from 84 to 81 % for Raphia taedigera, 65 to 58 % for Campnosperma panamensis, and 69 to 58 % for Cyperus sp. The proportions of carbon, nitrogen and phosphorus in the labile, semi-labile and recalcitrant carbon pools, did not reliably predict differences among species in the mass loss rate of litter. Phosphorus was rapidly lost from litter, while carbon losses, including soluble carbon, were slower, but significant for all fractions. The nonflooded treatment substantially reduced the quantity of C remaining in the residue fraction of leaf litter after 12 weeks, with 31, 19 and 6 % less remaining in the non-flooded treatment for R. taedigera, C. panamensis and Cyperus sp. This suggests that lower water table depth on litter decay increase degradation of mainly aliphatic and aromatic carbon in the residual fraction. Thus, although lowering the water table increased decomposition, the chemical composition of litter clearly influences peat accumulation.

Root oxygen loss from Raphia taedigera palms mediates greenhouse gas emissions in lowland neotropical peatlands

“…The magnitude of this effect is difficult to assess, as forest clearance would also dramatically reduce root exudation, which would limit substrate supply (Bhullar et al 2014;Ding et al 2005). In addition, litter and roots decay slowly under waterlogged conditions (Hoyos-Santillan et al 2015;Wright et al 2013a), suggesting that the strong immediate effect on CH 4 and N 2 O emissions following the palm forest clearance is linked to the lower oxygen levels in the peat matrix in the deforested area.…”

Interaction between litter quality and simulated water depth on decomposition of two emergent macrophytes

“…For the 0 cm treatment, the sand in tray was wetted with pond water completely but with no surface pooling. For the 5 cm and 80 cm treatments, the trays were emerged at 5 cm and 80 cm depth above the sand surface, respectively (Wright et al, 2013). Water depths in the trays were adjusted weekly.…”

“…In deep water ecosystems, both temperature and dissolved oxygen content are usually low limiting litter decomposition as an effect of reduced microbial activity (Torremorell and Gantes, 2010;Fonseca et al, 2013). Though many direct measurements of macrophyte decomposition rates in response to increase water depth have shown positive effects on decomposition process and nutrient release efficiency, also neutral or even negative results were reported (Cai et al, 2006;Wright et al, 2013;Arroita et al, 2015). The inconsistent effects of water depth on litter decomposition may be caused by differences in litter quality, since litter tissues (including roots, leaves, twigs and stems) used in the above-mentioned experiments differed in quality and type (Trinder et al, 2008).…”

Root-derived CO2 flux from a tropical peatland

“…In addition, plants release root exudates comprising species-specific combinations of sugars, organic acids and amino acids, which represent an additional significant substrate for heterotrophic microbial respiration (Smith 1976;Hanson et al 2000;Girkin et al 2018). A third significant source of CO 2 from anoxic wetlands is the oxidation of CH 4 driven by radial oxygen loss from root systems (Hoyos-Santillan et al 2016a) and aerobic surface peat (Jauhiainen 2005;Wright et al 2013a). Terms applied to describe this combination of processes include ''root-rhizosphere respiration'' (Sayer and Tanner 2010), ''root respiration'' (Andrews et al 1999), ''rhizosphere respiration'', and ''root-derived CO 2 '' (Kuzyakov and Larionova 2005).…”