Prediction of total organic matter in marsh sediments: integrating reflectance clustering, spectral subranges, and color coefficients
摘要
Total organic matter (TOM) in lake and marsh sediments is an important indicator of ecosystem function, carbon storage, and environmental changes. This study evaluated whether reflectance spectroscopy and color coefficients can provide accurate, rapid, and cost-effective alternatives to conventional TOM quantification in sediment cores.
Materials and methodsA total of 350 samples from 10 sediment cores were collected in Netley Marsh, a freshwater coastal wetland at the southern end of Lake Winnipeg, Manitoba, Canada. Reflectance spectra were obtained across the visible (VIS; 350–700 nm), near-infrared (NIR; 700–1000 nm), short-wave infrared (SWIR; 1000–2500 nm), and full-spectrum (350–2500 nm) ranges. Fifteen color coefficients were derived from the visible range. Partitioning Around Medoids (PAM) clustering was used to explore spectral shape variation, while Partial Least Squares Regression (PLSR), Random Forest (RF), and Cubist models were trained using 10-fold cross-validation and validated on an independent test set.
ResultsAll models achieved strong predictive performance (R² > 0.80, RPD > 2.2). Cubist consistently outperformed the other models, with the visible range yielding the most accurate results (R² = 0.95, RMSE = 1.7%, RPD = 4.32). Models based on color coefficients performed comparably to full-spectrum inputs.
ConclusionVisible-range reflectance and derived color metrics provide robust, rapid, and cost-efficient prediction of TOM in sediment cores. This approach offers a practical tool for reconstructing carbon dynamics and supporting sediment and wetland management in aquatic ecosystems.