Allometric scaling and carbon sequestration in agroforestry species of the Western Himalayas: a model-based approach

Abstract

Agroforestry offers a huge potential for carbon sequestration, contributing to climate change mitigation and carbon trading. This study focuses on Bauhinia variegata and Celtis australis, two important agroforestry tree species in the Western Himalayas aiming to develop allometric models and biomass prediction ratios using empirical data collected through selective sampling and minimally destructive methods. Biomass components were categorized and weighed, and allometric equations were developed using diameter at breast height and height as independent variables. Model stability was validated using cross-validation techniques, and their predictive accuracy was assessed. Models, particularly based on diameter, has significant predictive ability for predicting the biomass components for both the species. B. variegata demonstrated a higher capacity for CO₂ absorption and carbon credit generation. The biomass expansion factor and root-to-shoot ratio for C. australis and B. variegata was estimated to be 1.39 and 1.40; and 0.24 and 0.17, respectively. The annual biomass of B. variegata and C. australis was 5.97 and 4.67 Mg ha⁻¹ yr⁻¹, respectively. The total carbon stock for both species varied from 23.80 to 30.47 Mg C ha⁻¹. In B. variegata and C. australis, carbon sequestration was 105.93 and 82.11 Mg ha⁻¹, respectively, and net oxygen release ranged from 59.72 to 77.04 Mg ha⁻¹. The carbon sequestration by B. variegata translates into generating US$ 2119 in total carbon credits, with an annual credit of US$ 193, while C. australis yields US$ 1642 in total credits and US$ 149 annually. These findings highlight the utility of B. variegata and C. australis for carbon sequestration and provide valuable allometric equations for carbon credit estimation. The study emphasizes the importance of agroforestry in meeting India’s Nationally Determined Contributions and addressing climate policy goals.