Abstract
AbstractCarbon dioxide (CO2) flux is a critical component of the global C budget. While CO2 flux has been increasingly studied in mangroves, better partitioning of components contributing to the overall flux will be useful in constraining C budgets. Little information is available on how CO2 flux may vary with forest age and conditions. We used a combination of 13C stable isotope labeling and closed chambers to partition CO2 efflux from the seedlings of the widespread mangrove Avicennia marina in laboratory microcosms, with a focus on sediment CO2 efflux in establishing forests. We showed that (1) above‐ground part of plants were the chief component of overall CO2 efflux; and (2) the degradation of sediment organic matter was the major component of sediment CO2 efflux, followed by root respiration and litter decomposition, as determined using isotope mixing models. There was a significant relationship between C isotope values of CO2 released at the sediment–air interface and both root respiration and sediment organic matter decomposition. These relative contributions of different components to overall and sediment CO2 efflux can be used in partitioning of the sources of overall respiration and sediment C mineralization in establishing mangroves.
Highlights
Mangroves contain variably thick organic sediments and are the most carbon (C) rich forests (Donato et al 2011; Sanders et al 2016)
There was no significant difference between Es and ESOM (Tukey’s HSD test, p > 0.05)
Ec is the main component of ecosystem respiration (Ee), generally in agreement with the global synthesis of mangrove C flow (Ec : Es 5 10 : 1)
Summary
Mangroves contain variably thick organic sediments and are the most carbon (C) rich forests (Donato et al 2011; Sanders et al 2016). CO2 flux in mangroves may originate from the canopy, woody debris, root, litter and sediment organic matter (SOM), and is collectively called ecosystem respiration (Ee), which has been usually studied separately as canopy (above-ground parts, Ec) and sediment respiration (the other components, Es). Mangrove organic material such as leaf litter, if not exported, becomes incorporated in the sediment through decay and chemically modified by microbes inhabiting the aPresent address: Simon S.F. Li Marine Science Laboratory, School of Life Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong SAR. The study expands the horizon of current studies (e.g., Lovelock et al 2015), which measure the portions of Ee in mature mangroves and do not completely partition Es
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