Clearcut harvesting effects on soil and creek inorganic nitrogen in high elevation forests of southern interior British Columbia

Abstract

Hope, G. D. 2009. Clearcut harvesting effects on soil and creek inorganic nitrogen in high elevation forests of southern interior British Columbia. Can. J. Soil Sci. 89: 35Á44. Responses of both soil and stream inorganic nitrogen (N) after operational clearcut harvesting were explored in two high elevation British Columbia Engelmann spruceÁSubalpine fir (ESSF) forests. At one study site, net N mineralization was measured between 1 and 11 yr after harvest. At a second site, for 3 yr after harvesting, available soil ammonium and nitrate were measured using ion exchange resins, and drainage losses of N were estimated using tension lysimeters and soil water balance models. Stream water N concentrations were also measured in one unlogged, and two logged watersheds at the second study area for 12 yr, both pre-and post-clearcut harvesting. Growing season as well as over-winter increases in post-harvest soil nitrate were detected after 3 yr, and the increases were apparent for up to 11 yr. Seasonal losses of N in drainage were greater in clearcut soils than in the forest soils in year 2 for ammonium and in years 2 and 3 for nitrate. A high proportion of the N was lost in drainage during snowmelt. Stream water ammonium in all three streams and nitrate in the unlogged and one harvested creek remained at or below the detection level. In the third creek, the frequency of detection and concentrations of nitrate peaked 2 to 3 yr after 30 to 57% of the watershed was harvested. The annual peak in NO 3 -N concentrations occurred immediately before the snowmeltdriven stream flow peak. Drainage losses and stream N fluxes were both small, relative to the total soil N content. esure´e 12 anne´es durant dans un bassin hydrographique inexploite´et deux bassins exploite´s au deuxie`me site, avant et apre`s la coupe a`blanc. Au bout de trois ans, on de´ce`le une hausse de la concentration de nitrate dans le sol apre`s l'exploitation forestie`re, durant la pe´riode ve´ge´tative et apre`s l'hiver; ces hausses sont manifestes jusque pendant 11 ans. Les pertes saisonnie`res de N dues au drainage e´taient plus importantes dans le sol des coupes a`blanc que dans le sol forestier, la deuxie`me anne´e pour l'ammonium et les deuxie`me et troisie`me anne´es pour le nitrate. Une forte quantite´de N disparaıˆt lors du drainage, a`la fonte des neiges. La concentration d'ammonium e´tait identique ou infe´rieure au seuil de de´tection dans les trois cours d'eau; il en allait autant pour le nitrate dans le ruisseau du lot inexploite´et dans un des deux cours d'eau du site exploite´. Dans le troisie`me cours d'eau, la fre´quence de de´tection et la concentration du nitrate a atteint un pic deux ou trois ans apre`s exploitation de 30 a`57 % du bassin. La concentration de N-NO 3 atteint un pic annuel imme´diatement avant que les cours d'eau connaissent leur crue printanie`re. Les pertes dues au drainage et la fluctuation de la concentration de N dans les cours d'eau sont relativement faibles, comparativement a`la quantite´totale de N pre´sente dans le sol.

Long-term soil response to variable-retention harvesting in the EMEND (Ecosystem Management Emulating Natural Disturbance) experiment, northwestern Alberta

“…The observed decline in forest floor NH 4 -N concentrations with increasing levels of forest cover removal is inconsistent with other studies, which have shown no change (Jerabkova et al 2006a(Jerabkova et al , 2011 or an increase in forest floor NH 4 -N after clearcut harvesting (Hope 2009). Coupled with the lack of response in NO 3 -N, it is evident that the effect of harvesting of these forests on soil inorganic N concentrations is small and short-lived, compared with responses in other forest types (Prescott et al 2003;Jerabkova et al 2011).…”

Approaching four decades of forest watershed research at Upper Penticton Creek, British Columbia: A synthesis

“…Soils are derived from morainal and glaciofluvial sediments, and coarse‐grained granitic bedrock. They are sandy loams with a high coarse fragment content and are generally 0.5–0.6 m deep (Hope, 2009). All soil horizons have a low water holding capacity and are well‐ or rapidly drained.…”

Three years of increased soil temperature and atmospheric N deposition have no effect on the N status and growth of a mature balsam fir forest

“…The limited effect of the soil heating on inorganic N availability could be due to the site condition. The levels of available N at the site were compared with published data from boreal forest soils of Canada sampled with identical ion-exchange membranes (PRS-probes) including studies spanning over one to 11 growing seasons, monitoring unmanaged plots in a black spruce forest of Alberta (Jerabkova and Prescott, 2007), a wet spruce-fir forest of British-Columbia (Hope, 2009), and another wet mixed-conifer forest in British-Columbia (Bengtson et al, 2007). On a daily basis, the organic soil horizon sampled in the current study displayed 46 % less available NH 4 (range 15-67 %) and 62 % less NO 3 (range 30-77 %) than the other three sites.…”