Abstract

Globally, belowground biomass (BGB) accounts for 20–26% of total biomass, and as such it is an important carbon (C) pool for many vegetation types. However, large uncertainty exists for belowground biomass C compared to aboveground stocks. Using data from 108 destructively harvested trees belonging to 36 miombo species, we estimated root to shoot ratios, and developed models for estimation of aboveground biomass (AGB), BGB and total biomass C stocks in the Copperbelt province of Zambia. We also validated our models using independent datasets from elsewhere in Zambia and Malawi. The C fractions in wood ranged between 51.9 and 58.9%, which was higher than the IPCC default value. The root to shoot ratio was found to be 0.303. The analysis also demonstrated isometric scaling of BGB with AGB. According to cross-validation results, the model that incorporated wood density (ρ), diameter at breast height (D) and total stem height (H) formulated as AGB =0.093(ρD²H)^0.97 *1.08 outperformed existing models developed for the miombo woodlands in Zambia. The best model for BGB was BGB = 0.476(AGB)^0.88*1.126. Using the top-ranked models, the stand-level AGB stocks were estimated at 222.2 Mg ha⁻¹, while BGB stocks were estimated at 52.4 Mg ha⁻¹. Aboveground and belowground C stocks were 125.3 Mg ha⁻¹ and 29.5 Mg ha⁻¹, respectively. Total biomass C stocks were estimated at 152.1 Mg ha⁻¹ or 558.3 Mg ha⁻¹ CO₂ equivalent sequestered in tree biomass. These estimates may be used as baseline data for future carbon management and for emerging payment for ecosystem services projects in miombo woodlands.

摘要

在全球范围内，地下生物量 (BGB) 占总生物量的 20-26%，因此它是许多植被类型的重要碳 (C) 库。然而，与地上储量相比，地下生物量 C 存在很大的不确定性。使用来自属于 36 个 miombo 物种的 108 棵破坏性采伐树的数据，我们估计了根茎比，并开发了用于估计赞比亚铜带省地上生物量 (AGB)、BGB 和总生物量碳储量的模型。我们还使用来自赞比亚和马拉维其他地方的独立数据集验证了我们的模型。木材中的碳含量介于 51.9% 和 58.9% 之间，高于 IPCC 的默认值。发现根茎比为 0.303。该分析还展示了 BGB 与 AGB 的等距缩放。根据交叉验证结果，AGB =0.093(ρD ² H) ^0.97 *1.08优于为赞比亚 miombo 林地开发的现有模型。BGB 的最佳模型是BGB = 0.476(AGB) ^0.88 *1.126。使用排名靠前的模型，标准 AGB 存量估计为 222.2 Mg ha ^-1，而 BGB 存量估计为 52.4 Mg ha ^-1。地上和地下碳储量分别为 125.3 Mg ha ^-1和 29.5 Mg ha ^-1。总生物量碳库估计为 152.1 Mg ha ^-1或 558.3 Mg ha ^-1 CO ₂等效隔离在树木生物量中。这些估计值可用作未来碳管理的基线数据，以及为 miombo 林地生态系统服务项目的新兴支付。