Factors Controlling Decomposition Rates of Needle Litter Across a Chronosequence of Chinese Pine (Pinus tabuliformis Carr.) Forests

We investigated how factors underlying local spatial variations controlled needle litter decomposition across a chronosequence of Chinese pine (Pinus tabuliformis Carr.) forests. Litterbag methods were used to measure changes in litter chemistry and the mass loss of leaf litter, as well as selective biotic and abiotic factors during the growing seasons (May-October) in 2013 and 2014 in a set of fully replicated P. tabuliformis Carr. secondary forest stands that differ in age in northern China. During the two growing seasons the path analysis identified the litter lignin/N ratio, soil microbial metabolic quotient (qCO(2)), soil diversity of fungal assemblages (SFD), and soil-water content (SWC) as dominant controlling factors in needle litter decomposition, collectively explaining 76.9% of the total variation in mass loss across the entire age sequence. Litter lignin/N and soil qCO(2) had the greatest negative effects on the k value, followed by weaker positive effects of SFD and SWC. Our findings indicate that forest stand age has a great influence on needle litter decomposition by determining litter quality, with soil microbial activity and local environmental factors being secondary drivers in needle litter decomposition across a chronosequence of Chinese pine (Pinus tabuliformis Carr.) forests.