Allometric equations coupled with remotely sensed variables to estimate carbon stocks in date palms

Abstract

This study aims at developing specific allometric biomass equations that can be integrated into a remote sensing (RS) based model for assessing carbon sequestered in date palms. Assessing the potential of date palms to improve soil carbon sequestration was another objective. In a previous study, the authors demonstrated that combinations of visible and short wave single bands (Red, SWIR1, SWIR2) besides vegetation indices (DVI, NDI and RVI) derived from Landsat imagery correlated significantly with date palms’ biomass. Here and based on field and lab work, relevant structural variables were identified and used in the development of allometric equations. Results showed that the crown area (CA) best estimated both crown biomass (CB) and soil organic carbon (SOC). Likewise, the trunk height (Ht) was the best estimator of trunk biomass (TB). Using these variables, allometric equations were developed for date palms at different age stages and were used to estimate CB, TB and SOC with coefficients of determination (R2) of: 0.884, 0.835 and 0.952, respectively. Furthermore, the average ratios of below ground biomass (BGB) to above ground biomass (AGB) varied with palm maturity stages averaging 0.332, 0.925 and 0.496 for young, medium and mature palms, respectively. Moreover, the present study demonstrated that the amounts of organic carbon (OC) stored in date palms were considerable with values of: 15.88 kg/palm for young, 96.62 kg/palm for medium, and 225.58 kg/palm for mature palms. Substantially higher amounts of SOC were measured compared to other local plants with values of: 18.092 kg/palm, 62.594 kg/palm, and 92.908 kg/palm under young, medium and mature palms, respectively. The main achievement of the current study was the development of new and unprecedented allometric equations for date palm species in arid land. Such equations allow the development and calibration of a RS-based model for estimating biomass and Carbon Sequestration (CS) of date palms in the region with high accuracy.