PARENT SESSION
Poster Session 2: Forest Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Nitrogen immobilization by woodchip application: protecting water quality in a northern hardwood forest.
Homyak, Peter1, Burns, Douglas2, Germain, Rene1, Briggs, Russel1, Yanai, Ruth1, 1 SUNY College of Environmental Science and Forestry, Syracuse, NY, USA2 USGS, Troy, NY, USA
ABSTRACT- During peak leaf fall in northern hardwood forests, nitrate concentrations in streams have been reported to fall below detection limits. The immobilization of nitrate by material high in C:N suggests a means to mitigate the adverse effects of forest disturbance on stream water quality. We tested the potential of woodchips, which have an even higher C:N ratio than leaves, to immobilize N after forest harvesting, thus limiting NO3- export to stream water. We hypothesized that the addition of woodchips at the rate generated by logging slash would be sufficient to prevent elevated nitrate concentrations in soil solution. Five 0.2 ha patches were clearcut in August 2004 in the Frost Valley YMCA Model Forest, Catskill Mountains, NY. We applied three treatments to 9x9 m plots, with each treatment appearing in four of the clearcut patches. Treatment 1x involved the application of woodchips to the soil surface at the rate produced from slash smaller than eight inches in diameter, while 2x doubled that amount. A third treatment, 0x, did not receive chipped slash. In addition, three unharvested controls were located in forested areas between clearcut patches. Woodchips were primarily composed of sugar maple (Acer saccharum ), American beech (Fagus grandifolia ), and yellow birch (Betula alleghaniensis). Ion exchange resin bags (IONAC.NM-60H+/OH- form, Type I, Beads) were used to monitor soil N dynamics at each of the plots. In October 2004, seven weeks after harvesting, NO3- concentrations in the clearcut patches were 4 times greater than in control unharvested plots. The woodchip applications reduced NO3- concentrations to roughly 70% of the 0x treatment, but not down to the level of the uncut controls. Some N immobilization seems to be occurring in woodchip treated plots; further monitoring will prove whether woodchip application has potential as a management practice to protect water quality during forestry operations.
Key words: water quality, c:n ratio, nutrient cycling, forest disturbance