Impact of forest soil compaction on growth and survival of tree saplings

The use of heavy machinery to perform logging operations in forests has increased worldwide during the last decades in order to improve efficiency and safety and to reduce the physical stress for the forest worker. However, these machines may influence the soil ecosystem as they induce soil compaction, next to rutting and churning of the upper soil layers. This affects among other things soil porosity, pore continuity, soil aeration, hydraulic characteristics and penetration resistance. Heavy soil damage due to mechanized harvesting operations may therefore impose a serious threat to several parts of the soil ecosystem such as regeneration. We performed a meta‐analysis to quantify the impact of soil compaction on survival, height and diameter growth of tree saplings. In contrast with the expectations, the unweighted impact of soil compaction on these three variables was predominantly insignificant, varied strongly and was thus not always negative. A small influence emanated from the soil texture. The impact of soil compaction on growth and survival of tree saplings on relatively finetextured soils (silt, clay) was slightly negative. This contrasted with the coarser textures (loam, sand) where compaction had no or even a slight, positive effect. A weighted analysis, based on a subset of the data, revealed an overall decrease of height growth on the compacted area, but this result should be interpreted with caution due to the limited number of observations. Although results were less serious than expected, the biotic impact of soil compaction was negative in several cases. Harvesting activities should therefore focus on minimizing soil compaction degree and extent to prevent a decrease of soil productivity. From a methodological point of view we suggest providing more basic statistics in the articles and to include more shade tolerant tree species in future experimental designs. These species were rarely considered in this meta‐analysis