Allometric equations for below-ground biomass of four key woody species in West African savanna-woodlands

Abstract

Highlights• Species-specific equations for belowground biomass (BGB) predicted biomass with less bias than generic equations.• All the generic equations underestimated BGB.• For accurate estimation of BGB in savanna-woodlands, species-specific equations are needed for more species. AbstractAccurate estimates of both above-ground biomass (AGB) and below-ground biomass (BGB) are essential for estimating carbon (C) balances at various geographical scales and formulating effective climate change mitigation programs. However, estimating BGB is challenging, particularly for forest ecosystems, so robust allometric equations are needed. To obtain such equations for savanna-woodlands of the West African north sudanian zone, we selected four common native woody species (Anogeissus leiocarpa (DC.) Guill. & Perr., Detarium microcarpum Guill. & Perr., Piliostigma thonningii (Schumach.) Milne-Redh. and Vitellaria paradoxa C.F. Gaertn.). At two sites in Burkina Faso, we determined the BGB of 30 trees of each of these species by excavation, and measured various above-ground dimensional variables. The root:shoot ratio varied widely among the species, from 0.1 to 3.4. Depending on the species, allometric equations based on stem basal area at 20 cm height, basal area at breast height and tree height explained 50-95% of the variation in BGB. The best generic equation we obtained, based on basal area at 20 cm, explained 60% of the variation in BGB across the species. Three previously published generic allometric equations underestimated BGB by 8 to 63%. The presented equations should significantly improve the accuracy of BGB estimates in savanna-woodlands and help avoid costly needs to excavate root systems.

Site-Specific Allometric Models for Prediction of Above-and Belowground Biomass of Subtropical Forests in Guangzhou, Southern China

“…The root-shoot ratio measured as 0.221 was between the value of subtropical humid forest with above-ground biomass <125 tons ha −1 (0.20) and with above-ground biomass >125 tons ha −1 (0.24) documented by the IPCC [44]. The between-species difference in root proportion may be explained by differences in tree species rooting structures, with, e.g., Koala et al (2017) reporting root-shoot ratios ranging from 0.3 to 2.9, depending on tree species [45]. The finding in this study that root proportion has a negative correlation with tree size is consistent with those reported in other studies [15,46].…”

Agroforestry systems for mitigating climate change and reducing Carbon Footprints of land-use systems in Southern Africa

“…For example, Nair et al noted that the ability of roots to store large quantities of C in the soil makes them an essential component of soil C stocks [13] . However, BGB and C stocks are poorly estimated for many forest formations; hence, their potential to mitigate the effects of climate change remains a major knowledge gap [67] . However, understanding root biomass dynamics, root profiles and architecture, and rooting depth is important for improving our understanding of the allocation and storage of C in AFS.…”

Non-Conventional Methods as a New Alternative for the Estimation of Terrestrial Biomass and Carbon Sequestered

“…Therefore, nondestructive methods through allometric relationships are increasingly used. Such equations have also been proven to be fast, inexpensive, and more suitable for largescale estimation of forest carbon stocks [6]. Allometric models are commonly used in forest inventories and ecological studies [18].…”

“…The total carbon stock in any terrestrial ecosystem is the sum of carbon in living biomass, dead biomass and soil [6]. Eggleston et al [7] has listed five terrestrial ecosystem carbon pools involving biomass: above-ground biomass (AGB), below-ground biomass (BGB), litter, woody debris and soil organic matter [7].…”