Effects of site preparation treatments before afforestation on soil carbon release

Site preparation, as an important procedure before afforestation, can affect soil C release. However, the effect of site preparation on soil C release has not been sufficiently investigated. Two site clearing treatments (brush clearing and controlled burning) followed by three soil preparation treatments (overall soil preparation, spot soil preparation, and no soil preparation (control)) were carried out in subtropical China. Soil basal respiration (RS) and C release of biomass burning were measured as soil C release on an area basis from March 2011 to March 2013. The site preparations changed the soil C release in the first year but had no effects in the second year. Compared with brush clearing (control), controlled burning (control) significantly increased the annual soil C release (decreased RS but increased C release of biomass burning) during the first year. Within the brush clearing plots, overall soil preparation significantly increased the RS rate over eight months and resulted in an increase in annual soil C release during the first year compared to the no soil preparation. In contrast, spot soil preparation increased the RS rate only for three months and did not affect the annual soil C release during the first year relative to the no soil preparation. In the controlled burning plots, both overall and spot soil preparation increased the RS rate across six months, but only overall soil preparation caused a significant increase in the annual soil C release. Our study suggests that minimizing the disturbance of the site preparation would decrease soil C release. Concluding, the spot soil preparation followed brush clearing is a good choice for site preparation in term of soil C storage.