Wetland soil carbon storage exceeds uplands in an urban natural area (Florida, USA)

Abstract

Context . Urban greenspaces and natural areas are often recognised for their cultural services, but may also provide ecological services, including carbon (C) sequestration and storage. Aims . This study investigated the strength of the relationship between easily discernable ecosystem characteristics (e.g. topographic position, vegetation, and soil type) and soil C storage, and evaluated common conversion factors and methodologies used in soil C inventories. Methods . Sixty-seven full-depth (up to 5 m) soil cores were collected across nine community types in University of Central Florida ’ s Arboretum (Orlando, Florida, USA) and were analysed for bulk density, organic matter (OM) content, total C, and total nitrogen (N). Key results . Wetlands stored an average of 16 times more C than uplands and C density increased with soil depth. A 70% underestimation of soil C stocks would have occurred if sampling stopped at 50 cm. A strong linear relationship between soil C and OM supports the use of a 0.56 (C:OM) conversion factor for estimating soil organic C. Conclusions . The presence of wetlands is the key predictor of soil C and N storage, but the magnitude of storage varies widely among wetlands. Overall, the 225-ha study area stored 85 482 ± 3365 Mg of soil C. Implications . Urban natural areas should be evaluated for their ecosystem servicesseparately from their surroundingdevelopedlanduse/land cover with consideration for C storage potential. Leveraging topographic position, a site-speci fi c soil OM conversion factor, and depth to refusal testing can increase the accuracy and cost-effectiveness of soil C inventories.