2.1. Sample collection
Soil and biochar feedstockwere investigated in April 2012, in the
hilly redsoil regionof southern China.Atypical degraded quaternary
red soil (plinthudults, 0–30 cm, sampled from two soil profiles) and
bark of a local typical tree species (Pinus massoniana) were collected
in Qianhong Village, Jinhua City, Zhejiang Province, which is located
at 27020–31110N, 118010–123250E. The study area has a mean
annual precipitation of 1300mm, 70% of which is concentrated
between May and September. The average annual temperature is
15–19 C. Numerous P. massoniana bark charcoals which had not
undergonesoil processingand whichwere created froman accident
forest fire occurring on 22 December 2011 were collected from
different charred trees on top of nearby hills. Thus, the charcoalwas
an aged biochar (PBa) that has been naturally oxidized for
approximately 4 months. Soil properties are shown in Table 1.