Soil vulnerability to logging-associated compaction in forest ecosystems across global climatic zones

Soil compaction caused by mechanized wood harvesting can have long-lasting negative impacts on forest soils and impair forest ecosystem functioning and productivity for decades. However, soil compaction in forest ecosystems cannot be resolved by tillage. Thus, it is of paramount importance to prevent or minimize soil compaction in forest ecosystems. A primary step to achieve this goal is to determine the vulnerability of forest soils to compaction in different climatic zones. In this study, we performed a meta-analysis with 996 observations or 498 pairs of observations (effect sizes; compacted versus not compacted) of soil bulk density (BD) extracted from 57 peer-reviewed publications to assess the effects of climate and initial soil conditions on soil vulnerability to compaction. Forest soils of tropical and temperate zones were most vulnerable to compaction (14.9% and 12.7% increase in BD, respectively), while forest soils of cold and arid zones were less vulnerable (5.2% and 6.4% increase in BD, respectively). Climatic zones with high (> 1000 mm) and moderate (400 ─ 1000 mm) effective precipitation had the most vulnerable soil conditions to compaction (approximately 12% increase in BD) and the soils of climatic zones with low (< 400 mm) effective precipitation were less vulnerable (3.5% increase in BD). Our analyses indicated that the soils of climatic zones with high effective precipitation (tropical and temperate) are characterized by high soil organic carbon and are often wet, leading to low soil bulk densities and high vulnerability to compaction. Finally, we developed maps to illustrate the global pattern of soil vulnerability to compaction in forest ecosystems.