Contrasting Compaction Dynamics Of A Ferralsol After Alternative Mechanised Land Clearing In French Guiana

Changes in land uses and human impacts in tropical forest environments are steadily increasing in the Tropics, including in French Guiana. These changes often bring mechanised land clearing that cause soil compaction. Our aim was to monitor soil compaction in a 7-ha parcel of natural forest after mechanised clearing (using an alternative "chop and mulch" method with Stylosanthes guianensis cover) and replanting with four commercial timber species. Over this area, which in fact presented different types of soil cover (bare soil, mulch, herbaceous cover), we measured bulk density down to a depth of 30 cm and performed Beerkan's simplified infiltration test over three campaigns, before clearing, just after and nine months after. Before clearing, the soil had a high infiltration capacity (111 cm/h), density was low down to 5 cm (0.88 density) and higher in the 5-30 cm layer (1.19 to 1.40). Just after clearing, the soil's infiltration capacity was much reduced (2 cm/h), the surface layer had been highly compacted (1.28) but the deeper layers less so (1.41 to 1.49). Nine months after clearing, the soil's infiltration capacity had greatly improved (149 cm/h), especially under the S. guianensis herbaceous cover, and surface layer density was close to its initial condition (1.01), unlike the deeper layer (1.46 to 1.58). Further research is needed to explain the rapid return of the surface layer to its initial condition and to assess the relative contributions of the soil's macrofauna, plant roots and fissuring.