Do global change variables alter mangrove decomposition? A systematic review

Abstract

AimGlobal change is expected to modify the magnitude and trajectory of organic matter decomposition in mangrove ecosystems. Yet, the degree and direction of that change is unknown, especially considering the large C storage potential that mangroves provide. We performed a systematic review of primary literature to examine the relationships between genus‐specific litter quality, latitude or other global change proxies and decomposition of mangrove litter fractions.LocationGlobal.Time Period1976–2021.TaxonMangroves.MethodsWe compiled a dataset of 480 decomposition rates, including species, litter fraction, latitude, and relevant biophysical data. We investigated the influence of genera, tissue type, latitude, and global change proxies on decomposition rates using linear models and qualitative approaches. We also performed calculations to determine the potential importance of the decomposition process on the root litter biomass C pool in the context of blue C significance.ResultsCollectively, latitudinal relationships suggest that factors other than temperature, such as tissue type and genus, may regulate decay rates within mangroves' distributional range. Decay rates of leaf litter, roots, and wood converged on a value of 0.009 ± 0.0005, 0.002 ± 0.0001, and 0.001 ± 0.0003, respectively, across continents and geomorphological settings. Our calculations suggest that small changes in decomposition rate will not elicit large changes in blue C storage potential.ConclusionsThe main drivers behind variability in mangrove biomass decay rates detected across the distributional range remain uncertain. However, the small latitudinal range that mangroves inhabit and the submerged environment within which litter decomposes suggest that decay depends on species‐specific responses or biotic interactions among species to global change drivers. Few studies have examined global change impacts directly, and variability in decay and lack of representation of some mangrove groups in the literature suggest that implications for blue C are important to consider.

Deconstructing the mangrove carbon cycle: Gains, transformation, and losses

“…Decomposition is measured as the difference in biomass of a known quantity of plant material over time. The plant material can be left on site on the soil surface, submerged or buried (Middleton & McKee, 2001; Simpson et al, 2023). Studies of decomposition in mangroves have been conducted in leaves, roots, and downed wood, with leaves decomposing the fastest, especially when they are not buried (Simpson et al, 2023).…”

“…The plant material can be left on site on the soil surface, submerged or buried (Middleton & McKee, 2001; Simpson et al, 2023). Studies of decomposition in mangroves have been conducted in leaves, roots, and downed wood, with leaves decomposing the fastest, especially when they are not buried (Simpson et al, 2023). Although poorly studied, leaf decomposition appears not to be influenced by latitude but by leaf composition (Simpson et al, 2023).…”

“…For leaf decomposition, rates are difficult to calculate as most of the litter in mangroves is likely to be exported or consumed and the proportion of leaves remaining on the forest floor to decompose is unknown. Nevertheless, mean decay roots of leaf litter are estimated at 0.009 ± 0.0005 (Simpson et al, 2023).…”