Data for: Invasive Phragmites increases blue carbon stock and soil volume in a St. Lawrence estuary marsh
Our study of a St. Lawrence Estuary marsh reveals that, compared to the native Spartina patens-dominated vegetation, invasive Phragmites australis makes a greater contribution to soil volume and carbon stock (referred to as blue carbon). Phragmites contributions to soil volume enhances marsh sustainability in the face of sea level rise and its greater contribution to soil carbon helps to reduce the atmospheric concentration of CO2. An invasive genetic strain, introduced from Europe or Asia, has expanded extensively along the St. Lawrence River in the last few decades, but has been little studied on the estuarine portion of the St. Lawrence River. We collected soil cores from Phragmites stand and S. patens-dominated stand in a St. Lawrence Estuary salt marsh near la Pocatiere, Quebec. We measured the bulk density, carbon content, volume and mass of belowground organic matter in 2-cm thick soil layers of 3 cores at each Phragmites site. Only bulk density and carbon content were measured in 5-cm thick soil layers of 3 cores at S. patens site. Results showed that soil in the Phragmites stands held 37-77% more blue carbon than in the S. patens-dominated marsh. Based upon their diameter size, Phragmites rhizomes could be contributing 7.4-10.2 cm to the thickness in the upper 20 cm of soil. We suggest that any management of invasive Phragmites include consideration of its role in increasing blue carbon stocks and marsh resilience along with other ecosystem services. This dataset includes soil carbon and belowground biomass composition data in a St. Lawrence estuary marsh invaded by Phragmites australis. Data were collected in 3 Phragmites sites in 2019 and 1 Spartina patens site in 2014. There are no data in belowgroud biomass composition in S. patens site. Data were collected to estimate the invasive Phragmites contribution to blue carbon stock and soil volume. This dataset contains one Excel file with two sheets ("main data" and "diameter"). These data are from field samples and lab analysis. Dry bulk density is calculated by dividing the dry weight by the initial volume. The organic matter content of the ground samples was measured through loss-on-ignition (LOI) with the equation developed by Craft et al. (1991): % organic carbon = 0.40×%LOI + 0.0025(%LOI)2. As much as possible, rhizomes and roots were identified to species using the key of Niering et al. (1977). We used the color and turgor of rhizomes and roots to discern live from dead. Live material is usually light in color and turgid. Dead tissue is dark and flaccid. Unidentified material (mostly roots) was grouped together as “other”. The volume of each species was determined by placing the entire sample of a species in a graduated cylinder with a known amount of water and measuring the volume of water displaced. The sorted groups of belowground biomass were oven dried at 60°C to constant weight.