Sediment properties and CO2 efflux from intact and cleared temperate mangrove forests

[摘要] Temperate mangrove forests in New Zealand have increased in area over recentdecades. Expansion of temperate mangroves in New Zealand is associated withperceived loss of other estuarine habitats, and decreased recreational andamenity values, resulting in clearing of mangrove forests. In the tropics,changes in sediment characteristics and carbon efflux have been reportedfollowing mangrove clearance. This is the first study in temperate mangrove(Avicennia marina) forests investigating the impact of clearing on sediment CO₂ effluxand associated biotic and abiotic factors.

Sediment CO₂ efflux rates from intact (168.5 ± 45.8 mmol m⁻² d⁻¹) and cleared (133.9 ± 37.2 mmol m⁻² d⁻¹) mangroveforests in New Zealand are comparable to rates measured in tropical mangroveforests. We did not find a significant difference in sediment CO₂efflux rates between intact and cleared temperate mangrove forests.Pre-shading the sediment for more than 30 min prior to dark chambermeasurements was found to have no significant effect on sediment CO₂efflux. This suggests that the continuation of photosynthetic CO₂uptake by biofilm communities was not occurring after placement of darkchambers. Rather, above-ground mangrove biomass, sediment temperature andchlorophyll a concentration were the main factors explaining the variabilityin sediment CO₂ efflux in intact mangrove forests. The main factorsinfluencing sediment CO₂ efflux in cleared mangrove forest sites weresediment organic carbon concentration, nitrogen concentration and sedimentgrain size. Our results show that greater consideration should be givenregarding the rate of carbon released from mangrove forest followingclearance and the relative contribution to global carbon emissions.

[学科分类] 地球化学与岩石