Canadian Forest Service Publications
Quantification of nitrogen reductase and nitrite reductase gene abundance in soil of thinned and clear-cut Douglas-fir stands using real-time PCR. 2010. Levy-Booth, D.J.; Winder, R.S. Applied and Environmental Microbiology 76(21): 7116-7125.
Issued by: Pacific Forestry Centre
Catalog ID: 31908
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The abundance of nifH, nirS and nirK gene fragments involved in nitrogen (N) fixation and denitrification in thinned second-growth Douglas-fir (Pseudotsuga menziesii ssp. menziesii (Mirb.) Franco) forest soil was investigated using quantitative real-time PCR (qPCR). Prokaryotic N cycling is an important aspect of N availability in forest soil. The abundance of universal nifH, Azotobacter sp. specific nifH (nifH-g1), nirS and nirK gene fragments in unthinned control, 30%, 90% and 100% thinning treatments were compared at two long-term research sites on Vancouver Island, Canada. Soil was analyzed for organic matter (OM), total carbon (C), total N, NH4-N, NO3-N and phosphorus (P). Soil horizon accounted for the greatest variation in nutrient status, followed by site location. The 30% thinning treatment was associated with significantly greater nifH-g1 abundance than the control treatment in one site; at the same site, nirS in the mineral soil horizon was significantly reduced by thinning. The abundance of nirS genes significantly correlated with the abundance of nirK genes. Additionally, significant correlations were observed between nifH-g1 abundance and C and N in the organic horizon, and between nirS and nirK and N in the mineral horizon. Overall, no clear influence of tree thinning on nifH, nirS and nirK was observed. However, soil OM, C and N were found to significantly influence N-cycling gene abundance.