Soil processes and microbial community structures in 45-and 135-year-old lodgepole pine stands

As forests develop, changes in soil organic matter quantity and quality affect both nutrient dynamics and microbial community structure. Litter decomposition and nitrogen mineralization in association with soil microbial communities were compared between 45- and 135-year-old lodgepole pine (Pinus contorta var. latifolia (Englem.)) stands in southeastern Wyoming, USA. Compared with the 45-year-old stand, the 135-year-old stand was found to have greater live-tree biomass, litter decomposition rates (264 versus 135 mg.(g litter)(-1).year(-1)). soil nitrification rates (0.38 versus 0.19 mu g NO3-.(g soil)(-1) after 265 days of field incubation), and total phospholipid fatty acid (PLFA) concentrations (25 versus 9.2 nmol.(g soil)(-1) at 0-5 cm depth). Canonical correspondence analysis indicated that variation of PLFA profiles within the 45-year-old stand was explained by soil pH and bulk density, whereas soil process rates explained the distributions of PLFA profiles within the 135-year-old stand. The results of these studies indicate that stand age influences live-tree biomass and soil properties that can lead to changes in litter decomposition rates and soil microbial communities in lodgepole pine forests.