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Publication Title: Nitrogen dynamics in conifer-dominated forests with and without hardwoods
Year: 1987 Publication Type: Journal Article
H. J. Andrews Publication Number: 2163
Citation: Perry, D. A.; Choquette, C.; Schroeder, P. 1987. Nitrogen dynamics in conifer-dominated forests with and without hardwoods. Canadian Journal of Forest Research. 17(11): 1434-1441.
Online PDF: http://andrewsforest.oregonstate.edu/pubs/pdf/pub2163.pdf
Abstract: Nitrogen and carbon in the surface 12 cm of mineral soil, N in leaf litterfall, anaerobic N mineralization rates in the soil andforest floor, and root and N accretion to sand traps placed in surface soil layers were compared in forests with hardwoods eithercompletely or partially removed during a conifer thinning 3 years before. An adjacent unthinned conifer-hardwood stand wasalso included. Conifer stocking did not differ between thinned stands with and without hardwoods. Stands without hardwoodsaveraged 520 kg/ha more N in mineral soil (p < 0.001), 20% more N mineralized from soil during 7-day incubations (p <0.001), and lower soil C:N ratio (p = 0.02) than stands with hardwoods. These variables did not differ between thinned andunthinned mixed stands. Soil N did not correlate with the .number of hardwoods removed. Weight of forest floor and rate of Nmineralization from the forest floor did not differ between mixed and pure stands. However, stands with hardwoods returnedabout 10 kg • ha- • year- more N in leaf litter (due to higher N concentration in conifer litter as well as the presence of high-Nhardwood litter); stands without hardwoods accreted about 10 kg • ha-l• year more N in sand traps. Soil N mineralization inmixed stands correlated positively with N mineralization in the forest floor but not with N accretion to sand traps, while theopposite was true in pure conifer stands. Although pretreatment variability among stands cannot be ruled out, the replicatedtreatments within a relatively uniform area make it appear likely that differences were related to the presence or absence ofhardwoods. This was not a simple additive effect, however, but a community-level phenomenon, that is, conifers cycled Ndifferently when mixed with hardwoods than when in pure stands.
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