Degradation of mangrove tissues and implications for peat formation in Belizean island forests

Abstract

Summary 1Macrofaunal leaf consumption and degradation of leaves, woody twigs and roots were studied in mangrove island forests on a Belizean island. Factors influencing accumulation of organic matter deposited both above and below ground in this oligotrophic, autochothonous system were assessed. 2 Leaf degradation rates of Rhizophora mangle (red mangrove), Avicennia germinans (black mangrove) and Laguncularia racemosa (white mangrove) measured in mesh bags, were much faster in the lower than the upper intertidal zone. Mass loss was most rapid in A. germinans but zonal effects were much larger than species differences. 3 Exposure to invertebrates such as crabs and amphipods tripled overall rates of leaf litter breakdown. In the lower intertidal, crabs completely consumed some unbagged leaves within 23 days. Crabs also had an effect on some upper intertidal sites, where degradation of leaves placed in artificial burrows was 2.4 times faster than when placed on the soil surface. 4 In contrast to leaves (27 ± 5% remaining after 230 days), roots and woody twigs were highly refractory (40 ± 2% and 51 ± 6% remaining after 584 and 540 days, respectively). Root degradation did not vary by soil depth, zone or species. Twigs of R. mangle and A. germinans degraded faster on the ground than in the canopy, whereas those of L. racemosa were highly resistant to decay regardless of position. 5 Peat formation at Twin Cays has occurred primarily through deposition and slow turnover of mangrove roots, rather than above-ground tissues that are either less abundant (woody twigs) or more readily removed (leaves).

Including GHG emissions from mangrove forests LULUC in LCA: a case study on shrimp farming in the Mekong Delta, Vietnam

“…The rest of the harvest consists of a mix of other shrimps, mud crabs, and other aquaculture products (Vu et al 2013;Jonell and Henriksson 2014). The GHG emissions from mangrove LULUC from shrimp farming were subsequently estimated to be 184 t CO 2 -eq t −1 live shrimp at farm gate using mass allocation and 282 t CO 2 -eq t −1 live shrimp using economic allocation (see ESM 2 for details on the calculations and Twilley et al 1992;Eong 1993;Matsui 1998;Kauffman et al 2011;Donato et al 2011;Ray et al 2011;Donato et al 2012 b Komiyama et al 1987;Twilley et al 1992;Matsui 1998;Kauffman et al 2011;Ray et al 2011;Donato et al 2012c Eong 1993Matsui 1998;Kauffman et al 2011;Ray et al 2011;Donato et al 2012;Lundstrum and Chen 2014 d Twilley et al 1992;Amarasinghe and Balasubramaniam 1992;Eong 1993;Day et al 1996;Middleton and McKee 2001;Jennerjahn and Ittekkot 2004;Guzman et al 2005;Ray et al 2011 e Twilley et al 1992;Eong 1993;Duarte and Cabrián 1996;Chmura et al 2003;Alongi 2008;Sanders et al 2010;Ray et al 2011;Mcleod et al 2011 Rewetted land, previously vegetated by mangrove, salinity >18 ppm kg CH 4 ha −1 year −1 0 R a n g e=0 -40 (uniform) IPCC 2014 assumptions behind them). Noteworthy is that these LULUC emissions only apply to Bmixed mangrove concurren...…”

“…Sequestration rates have been estimated at between 228 and 766 t ha −1 year −1 Lundstrum and Chen 2014). Hypoxic conditions and the lack of other high-energy oxidants, in combination with a paucity of fungi, limit the opportunity for degradation, thereby providing good conditions for long-term storage of carbon (Middleton and McKee 2001). This, together with high biomass burial rates, the high potential age of mangrove trees, and a slow turnover rate, results in carbon storage rates relevant at global scales (Duarte et al 2005;FAO 2007).…”

Broad-scale modelling of coastal wetlands: what is required?

“…Whilst it is clear that below-ground processes play an important role in coastal wetland stability (Nyman et al, 1995), the volume of sediment accreting on a wetland surface is the primary determinant of system response within the model. Sediment supply from in situ accumulation of organic sediments (Cahoon & Reed, 1995;Middleton & McKee, 2001;Rooth et al, 2003) or from external, inorganic inputs (French & Spencer, 1993;Christiansen et al, 2000) or a combination of the two, are used to characterise the impact of the environmental forcing factor within the DIVA model.…”

Estimation of Regional Carbon Storage Potential in Mangrove Soils on Carmen Island, Campeche, Mexico

“…Latitude, climate, species diversity and other biological factors also affect carbon fluxes in forests [3]. It has been reported that degradation of fresh organic matter is slower in anaerobic environments (such as mangroves), which additionally involves oxidizing agents such as nitrate and microorganisms like bacteria and fungi [6], which only operate when the tannin concentrations are low, because they inhibit growth [7][8]. The presence and abundance of macro invertebrates such as amphipods (crabs) and isopods (cochineal) also accelerates the breakdown of tissues by direct consumption of leaves [6].…”