Exploring underlying drivers of coarse above- and below-ground carbon sequestration in China's plantations

Abstract

A significant proportion of the Earth's natural forests has been continuously degraded each year as a result of human activities and global environmental changes. Meanwhile, there has been a rise in the establishment of plantations through numerous planting trees initiatives, including those recently spearheaded by the United Nations (UN) Decade (2021–2030). Yet, considerable global uncertainty remains on drivers of carbon (C) sequestration (defined by C stocks and annualized accumulation rates) in plantations. By using the meta-data from 257 plantation plots in China, we quantified above- and below-ground C stocks and annualized C accumulation rates in tree organs, i.e., stems, branches, leaves, and roots, based on biomass allometric equations and scaling rules. Multiple linear regression models were used to explore the drivers (i.e., stand age, climate and soil factors) of plantation above- and below-ground C stocks and accumulation rates. We show that above- and below-ground C stocks increased with stand age (β = 0.55 to 0.66; P < 0.001) followed by temperature (β = 0.29 to 0.36; P = 0.001 to < 0.001), precipitation seasonality (β = 0.23 to 0.41; P = 0.013 to < 0.001), and somehow by climatic humidity (β = 0.17 to 0.35; P = 0.105 to 0.002), but decreased with isothermality (β = -0.14 to -0.16; P = 0.024 to 0.019). Soil clay content increased stem C stock (β = 0.15; P = 0.016) whereas soil cation exchange capacity increased branch C stock (β = 0.23; P = 0.003), even though soil factors did not significantly affect annualized C accumulation rates (β = -0.12 to 0.14; P = 0.908 to 0.078). This coarse-scale study suggests that C sequestration in China’s plantations increases over time with increasing climatic temperature and soil fertility, thereby sustaining environmental conditions by capturing C from the atmosphere and storing it in tree organs. Thus, conserving environment-friendly plantations, having no disruption to native biodiversity, as land resources can reduce pressures on natural forest resources while improving environmental integrity through feedback.