Abstract
Understanding the driving factors of forest biomass are critical for further understanding the forest carbon cycle and carbon storage management in karst forests. This study aimed to investigate the distribution of forest aboveground biomass (AGB) and the effects of stand structural and abiotic factors on AGB in karst forests in Southwest China. We established a 25 ha plot and sampled all trees (≥1 cm diameter) in a subtropical mixed evergreen–deciduous broadleaf forest. We mapped the forest biomass distribution and applied a variation of partitioning analysis to examine the topographic, stand structural, and spatial factors. Furthermore, we used structural equation models (SEM) to test how these variables directly and/or indirectly affect AGB. The average AGB of the 25 ha plot was 73.92 Mg/ha, but that varied from 3.22 to 198.11 Mg/ha in the 20 m × 20 m quadrats. Topographic, stand structural, and spatial factors together explained 67.7% of the variation in AGB distribution. The structural variables (including tree density and the diameter at breast height (DBH) diversity) and topographic factors (including elevation, VDCN (vertical distance to channel network), convexity, and slope) were the most crucial driving factors of AGB in the karst forests. Structural equation models indicated that elevation, tree density, and DBH diversity directly affected AGB, and elevation also indirectly affected AGB through tree density and DBH diversity. Meanwhile, AGB was indirectly influenced by VDCN, convexity, and slope. The evaluation of stand structural and abiotic drivers of AGB provides better insights into the mechanisms that play a role in carbon storage in karst forests, which may assist in improving forest carbon management.
Highlights
Forests account for 30% of the earth’s total land area, and contribute to 75% of the terrestrial gross primary production and 80% of the total global plant biomass [1,2]
We investigated a karst forest biomass and examined stand structural and abiotic factors driving
We found that the mean forest aboveground biomass (AGB) was 73.92 ± 23.51 Mg/ha
Summary
Forests account for 30% of the earth’s total land area, and contribute to 75% of the terrestrial gross primary production and 80% of the total global plant biomass [1,2]. Southwest China has the second largest forest region in China [6]. This region contains the largest karst forest region in China, with an extremely fragile geological background, small environmental carrying capacity, and low tolerance to disturbance [7]. A large part of the karst region in southwest China was severely degraded following the destruction of natural vegetation due to human disturbance. Most of the degraded land has been undergoing ecological restoration, either through natural regeneration or afforestation, attributed to Forests 2020, 11, 443; doi:10.3390/f11040443 www.mdpi.com/journal/forests
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