EFFECTS OF SCHIMA SUPERBA PLANTATIONS ON SOIL CHEMICAL PROPERTIES IN THE ACID RAIN REGION OF CHONGQING, SOUTHWESTERN CHINA

Aims In recent decades, frequent fires have destroyed large areas of coniferous Pinus massoniana forests in Chongqing, Southwestern China. Schima superba, a fire-resistant broadleaved tree species, has been widely planted on the burned areas. S. superba is thought to improve soil properties; however, little information is available from plantations exposed to acid deposition. Our objective was to examine the effects of S. superba plantations on soil chemical properties in the acid rain region.Methods We investigated soil chemical properties of a pure S. superba plantation planted on a burned area of a former pure P. massoniana plantation in the Tieshanping Forest Farm of Chongqing City using a soil core method. Results were compared with those from an adjacent unburned pure P. massoniana plantation, which was planted at the same time as the burned pure P. massoniana plantation.Important findings For 0-20 and 20-60 cm soil layers in the S. superba plantation, average pH values were 3.61 and 3.77 and average base saturation (BS) values were 4.68% and 7.92%, respectively. For these two soil layers in the P. massoniana plantation, average pH values were 3.78 and 3.88 and average BS values were 9.25% and 16.32%, respectively. Compared with the P. massoniana plantation, contents of exchangeable base cations (K+, Na+, Ca2+ and Mg2+) and total P were generally lower in the soil of the S. superba plantation, but contents of exchangeable Al3+, Fe3+ and H+ were significantly higher (p<0.05). This study suggested that the S. superba plantation accelerated soil acidification. Therefore, in the acid rain region of Chongqing, large areas of pure S. superba plantations should be avoided when using S. superba for establishment of fire-resistant forest belts or for regeneration and transformation of pure P. massoniana plantations.