Changes in Leaf Litter Quality During Its Decomposition in a Tropical Planted Mangrove Forest (Can Gio, Vietnam)

Abstract

Mangroves are highly productive ecosystems, being key components of trophic food chains along tropical coastlines. In Southern Vietnam, planted Rhizophora apiculata develops in the upper intertidal zone, while Avicennia alba naturally colonizes areas at lower elevation along tidal creeks. The main objective of this study was to quantify the seasonal variability of leaf litter decomposition rates considering that in previous studies we observed a strong influence of the monsoon on C and nutrients cycling within the mangrove and in adjacent creeks. We were also interested in changes in the quality of the leaf litter during its decomposition, focusing on nutrients, δ 13 C, and trace metals. To reach our goals, we used the litterbag technique. During the monsoon, leaf litter decay rates were increased in the Avicennia stand, most probably because of enhanced leaching resulting from a higher level of the river due to heavy rainfall. In addition, the enhanced decay rates measured in the Avicennia stand during the rainy season resulted in a strong 13 C depletion, while 13 C enrichment was measured in the other conditions. Elemental concentrations changes during decay were not clearly influenced by season, but depended on the element considered. K, Mg, Na, and Ca had t 50 values lower than the one of the bulk material. P and S contents also rapidly decreased during the first decomposition stages, but these elements had longer t 50 values than the bulk leaves. Conversely, an enrichment in most trace metals was observed during leaf litter decomposition whatever the season. We suggest that these metals were either trapped from the water column and the forest floor by organic molecules composing the litter, or subjected to litter decomposers uptake. Consequently, this study shows that the release or the uptake of elements during mangrove leaf litter decomposition varied with different parameters, which may have ecological implications on the nature of the elements exported toward adjacent ecosystems, and on their primary productivity.

Potassium Control of Plant Functions: Ecological and Agricultural Implications

“…The sophisticated mechanisms in which K + is involved are pivotal for water- and nutrient-use efficiency, stress avoidance, and general plant homeostasis controls that imply several ecosystem-ecological consequences, such as species replacement or water- and nutrient-cycle variations in global change scenarios. As observed in several forests, such as temperate and tropical forests, K + is rapidly released during litter decomposition [ 204 , 205 , 206 ]. However, more than 70% of the initial K + content can be released during the first week of the decomposition process [ 207 ].…”

Trace Metal Dynamics in a Tropical Mangrove Tidal Creek: Influence of Porewater Seepage (Can Gio, Vietnam)

“…These results may suggest a greater contribution of mangrove porewaters to the tidal creek during the rainy season because of the larger volume of water exchanged between mangrove soils and mangrove creek, and because of a larger mangrove area immerged resulting from the higher water level. In addition, higher temperature during summer may also be involved, inducing enhanced processes of organic matter decomposition in mangrove soils as suggested in other studies (Taillardat et al, 2019;Vinh et al, 2020). Mangrove soils are most of the time anoxic (Kristensen et al, 2017), which is also the case for Can Gio (Thanh-Nho et al, 2019b;Vinh et al, 2019).…”

“…We suggest that these higher concentrations were related to higher Mn D concentrations in porewaters ( Table 2). Vinh et al (2020) showed that during the rainy season, the elevated temperature and the high rainfall induced enhanced mineralization rates of leaf litter, which may have resulted in higher Mn D production in mangrove soils. In addition, during the rainy season, the water level of the river and thus of the tidal creek was higher.…”

Methodology for assessing the role of mangroves in trace metal(loid) filtration to develop a mechanism of payments for environmental services for mangroves in Vietnam

“…Previous literature has used mangrove plants and their sediments as reliable biological indicators to assess metal(loid) contamination and pollution (Defew et al 2005). Also, trace metal(loid)s are enriched during the decomposition of organic matter and can be absorbed in the water column at high tide and in surface sediments by organic molecules or decomposing litterfall (Vinh et al 2020).…”