Response of mineral soil carbon storage to harvest residue retention depends on soil texture: A meta-analysis

Harvest residue retention or removal can influence soil carbon (C) sequestration during forest management. Many studies have explored the factors that affect the direction and extent of changes in soil C after different harvest residue management practices. However, the effect of soil properties, especially soil texture, on the difference in mineral soil C storage between harvest residue retention and removal treatment are still not fully understood. Using a meta-analysis approach, we investigated the factors that influence the change in mineral soil C stocks following stem-only harvest (SOH), when compared to whole-tree harvest (WTH). We found that the retention of harvest residues associated with the SOH treatment led to 8.2% greater soil C storage in 0-20 cm mineral soils, compared to the WTH treatment. Soil properties (soil clay content and C concentrations) were the most important factors mediating soil C response to residue retention. Relative to the WTH treatment, the SOH treatment showed smaller mineral soil C pools in some high clay content soils, possibly by increasing the mineralization of existing soil organic matter stocks via a priming mechanism. Climate was a poor predictor of differences in treatment effects, with no significant difference between temperate and tropical forests. There were no significant relationships between the treatment effect on mineral soil C and mean annual temperature or precipitation. Both coniferous and broadleaf forests exhibited a significantly higher mineral soil C storage in the 0-20 cm soil layer with the SOH relative to the WTH treatment. Compared to WTH treatment, the higher soil C contents in upper mineral soils after the SOH treatment appeared to last about one decade after harvesting. The findings of this analysis suggest that soil texture and C concentrations in mineral soils should be considered when assessing the impact of forest harvest residue management on soil C pools.