Biochar application during reforestation alters species present and soil chemistry

Reforestation of landscapes is being used as a method for tackling climate change through carbon sequestration and land restoration, as well as increasing biodiversity and improving the provision of ecosystem services. The success of reforestation activities can be reduced by adverse field conditions, including those that reduce germination and survival of plants. One method for improving success is biochar addition to soil, which is not only known to improve soil carbon sequestration, but is also known to improve growth, health, germination and survival of plants. In this study, biochar was applied to soil at rates of 0, 1, 3 and 6 t ha− 1 along with a direct-seed forest species mix at three sites in western Victoria, Australia. Changes in soil chemistry, including total carbon, and germination and survival of species were measured over an 18 month period. Biochar was found to significantly increase total carbon by up to 15.6% on soils low in carbon, as well as alter electrical conductivity, Colwell phosphorous and nitrate- and ammonium-nitrogen. Biochar also increased the number of species present, and stem counts of Eucalyptus species whilst decreasing stem counts of Acacia species. Biochar has the potential to positively benefit reforestation activities, but site specific and plant-soil-biochar responses require targeted research.