Assessing Carbon Stock and Sequestration Capacity of Phragmites australis Using Integrated Destructive Sampling and Remote Sensing Approaches in Arid Environments

Phragmites australis (common reed) delivers key ecosystem services, including carbon sequestration, yet its carbon storage potential in hyper-arid environments remains insufficiently quantified. This study combines destructive sampling, laboratory carbon analysis, and satellite-derived vegetation indices to establish a rigorously validated baseline for aboveground biomass (AGB) and carbon stocks in a constructed wetland in Oman (n = 12 plots). Using leave-one-out cross-validation, this study tested whether biomass-prediction approaches commonly applied in wetland carbon research, namely height-based allometric equations and satellite vegetation indices, generalize beyond the data used to build them. The results show that the height-based equations achieve a near-perfect statistical fit by mathematical construction rather than genuine predictive validity, and that satellite vegetation indices require a larger, independent sample than used here to achieve validated accuracy; together, these findings establish a concrete, quantitative benchmark for sampling design and model validation in data-limited hyper-arid systems. The corrected destructive-sampling dataset places carbon stock at this site between 0.19 and 1.95 kg/m2, depending on the measurement method used. Together, these results support P. australis-dominated constructed wetlands as measurable, nature-based carbon reservoirs and chart a clear, evidence-based path toward reliable, remote sensing-based carbon monitoring across the Gulf Cooperation Council region and other water-stressed environments.