Spatially and temporally explicit estimates of above- and below-ground biomass allocation in China’s forests

Abstract Understanding the above- and below-ground biomass allocation is crucial for accurately predicting the impacts of vegetation on carbon cycling. However, the spatial and temporal patterns of above- and below-ground biomass allocation in China’s forests remain largely unknown. We conducted a comprehensive estimation of above- and below-ground biomass allocation in China’s forests using the above- and below-ground biomass carbon pool dataset (with a spatial resolution of 1 km grid) from 2002 to 2021. Our results demonstrate for the first time that, within China’s forest ecosystems, the root-to-shoot (R/S) ratio (usually defined as the ratio of below-ground biomass (BGB) to above-ground biomass (AGB)) was higher in the northern regions compared to the southern regions, suggesting a greater allocation of carbon to below-ground components in plants from the northern areas. Temporally, we observed a significant decline in R/S ratios. The relative importance ranking from random forest analysis reveals that the Mean Diurnal Range (TDR) was the most critical factor regulating the spatial and temporal variability of above- and below-ground biomass allocation. These findings provide a foundational understanding of forest ecosystem carbon dynamics, shedding light on the complex interplay between above- and below-ground components.