Does urban land use decrease carbon sequestration? —A case study in Taizhou, China

Abstract

Aims Urban land use has dramatically changed ecosystem functions especially carbon sequestration and storage in the built-up area. Our objective was to assess carbon sequestration and storage by estimating the biomass and net primary productivity (NPP) of urban vegetation including trees,shrubs and lawns with consideration of the effects of garden management (pruning and mowing). Methods Biomass and NPP from all trees,shrubs and lawns were estimated from 346 random quadrats. Allometric equations were used to calculate tree biomass from diameter at breast height and total height. An increment borer was used to measure trunk increment. Biomass and NPP from shrubs and lawns were estimated by destructive sampling. Management activities were recorded through actual measurements and the records of gardeners. Important findings Trunk growth rate of individual urban trees is two times that in native forest. Pruning accounts for 30% of tree NPP. Carbon sequestration per unit of Taizhou built-up area is estimated to be 2.1 × 103 kg C.hm–2.a–1 (with trees,shrubs and lawns contributing 64%,9% and 27%,respectively),which is lower than native forest. We infer that the carbon sequestration ability of Taizhou built-up area could meet the level of native evergreen broad-leaved forest if vegetation coverage is increased from 23% to 46%.