Soil Microbial and Enzymatic Activities Across a Chronosequence of Chinese Pine Plantation Development on the Loess Plateau of China

Successional and seasonal effects on soil microbial and enzymatic properties were studied in Chinese pine (Pinus tabu- laeformis) plantations in an age sequence of 3-, 7-, 13-, 21- and 28-year-old in northern Ziwuling region in the middle of Loess Plateau, China. The results indicated that plantation age and season affected soil microbial and enzymatic parameters significantly. Soil organic C, total N, microbial biomass C, microbial quotient, basal respiration, dehydrogenase, N-α-benzoyl-L-argininamide (BAA)-protease, urease and β-glucosidase increased quickly and tended to be highest at PF21 (21-year plantation), thereafter they remained nearly at a constant level, whereas the metabolic quotient (qCO 2 ) showed an initial increase and then decreased gradually. Measures of these soil properties showed significant seasonal fluctuations except for organic C and total N, which were found to be relatively stable throughout the study period, and the seasonal distributions were autumn > spring > summer > winter for microbial biomass C, microbial quotient, dehydrogenase, and β-glucosidase; autumn > summer > spring > winter for BAA-protease and urease; and summer > autumn > spring > winter for basal respiration and qCO 2 . Significant season × age interaction was observed for biomass C, basal respiration, dehydrogenase and BAA-protease.