Allometric Models for Estimating Aboveground Biomass, Carbon and Nitrogen Stocks in Temperate Avicennia marina Forests

Estuarine ecosystems are changing rapidly in response to anthropogenic impacts. Mangrove expansion in New Zealand is mainly attributed to favourable climatic conditions and increased sedimentation due to land use change. This expansion is associated with large scale shifts in ecosystem structure and function, with significant potential impacts on coastal carbon and nitrogen storage. A fundamental aspect of understanding these impacts is accurately estimating storage within above ground biomass. We developed allometric equations to estimate above ground biomass, carbon and nitrogen stocks for temperate Avicennia marina subsp. Australasica growing near the southern limit of the species distribution range in New Zealand. We compare these equations with existing equations for Avicennia spp. Tree height, trunk circumference, tree canopy volume and tree canopy area were strong predictors of total above ground biomass, carbon, and nitrogen stocks. Carbon and nitrogen stocks accounted for 41.23 +/- 0.40 % and 1.28 +/- 0.03 %, respectively, of total above ground biomass. This study is the first to develop allometric equations to estimate biomass, carbon and nitrogen stocks in temperate Avicennia marina. These equations can be used to improve assessments of the impact of changes on mangrove forest structure and function, in particular carbon and nitrogen storage.