A severe natural windstorm followed by a high intensity forest fire caused significant increases in runoff and in losses of nitrogen, phosphorus, and potassium from two small Precambrian watersheds. Both the windstorm and the fire had significant effects on water and chemical yields. Water yields in the two basins were 1.6 and 1.8 times the pre-impact means, respectively, in the year after the burn. Maximum chemical losses were observed for nitrate, with values of 3.4 and 9 times the pre-impact means for the two basins in the year after the burn. Increases in annual yields of most chemical parameters were 1.1 to 2.9 times the background. Both increased concentrations and increased flow volumes appear to be responsible for the increased nutrient losses.Key words: forest fire, windstorm, stream water quality, phosphorus, nitrogen, potassium losses, water yield

Results of a 4-yr study of the hydrology of the Rawson Lake watershed, as well as the chemistry of precipitation, streamflow, and the lake are presented. Inputs of water and most chemicals varied by as much as 2 times from one year to the next, illustrating that several years’ data are necessary to determine accurately average nutrient inputs and losses from an ecosystem. Precipitation appeared to be almost the sole source of P and N to lake and terrestrial ecosystems, although N2 fixation cannot be dismissed in the latter case. Significant proportions of Ca, Mg, Na, K, Cl, and SO4 were supplied directly from precipitation. The lake also received substantial quantities of these elements as well as silicon, from weathering of terrestrial geological materials. Although far from any major industrial sources of SO2, the pH of precipitation averaged < 5 for the years studied. Both terrestrial and lake systems retained a high proportion of entering P and N, and smaller proportions of other nutrients. Interpretation of relative retentions of nutrients revealed that the terrestrial ecosystem has well-balanced P and N supplies, while the lake was P limited. Rates of loss of chemicals from the terrestrial watershed of Rawson Lake are comparable to other sites in the Precambrian Shield, but lower than values from other geological settings.

No abstract

1. Movements and habitat use by Atlantic salmon parr in Catamaran Brook, New Brunswick, were studied using Passive Integrated Transponder technology. The fish were tagged in the summer of 1999, and a portable reading system was used to collect data on individual positions within a riffle-pool sequence in the early winter of 1999. Two major freezing events occurred on November 11-12 (Ice 1) and November 18-19 (Ice 2) that generated significant accumulations of anchor ice in the riffle. 2. Individually tagged parr (fork length 8.4-12.6 cm, n ¼ 15) were tracked from 8 to 24 November 1999. Over this period, emigration (40%) was higher from the pool than from the riffle. Of the nine parr that were consistently located, seven parr moved <5 m up-or downstream, and two parr moved more than 10 m (maximum 23 m). Parr moved significantly more by night than by day, and diel habitat shifts were more pronounced in the pool with some of the fish moving closer to the bank at night. 3. During Ice 2, there was relatively little movement by most of the parr in the riffle beneath anchor ice up to 10 cm in thickness. Water temperature was 0.16°C above the freezing point beneath anchor ice, suggesting the existence of suitable habitats where salmon parr can avoid supercooling conditions and where they can have access to low velocity shelters. To our knowledge, these are the first data on habitat use by Atlantic salmon parr under anchor ice.

1987. Experimental acidification of a Sphagnum-dominated peatland: first year results. Can. J. Fish. Aquat. Sci. 44(Suppl. 1): 194-205.A poor fen (3.6 ha) in northwestern Ontario was experimentally acidified with H N 0 3 and H2S04 to study the effects sf acid precipitation on the dominant Sphagnum species and on the chemistry of the surface waters and pore waters. The nitrate concentration in the surface waters sf the fen increased from < 0.07 pseq-L-' NO; -N to between 20-70 peq-L-' during or just after each acidification event. Subsurface NO; -N concentrations remained unchanged and surface NO.; -N concentrations returned to background levels within a day. The mire as a whole retained over 99% sf the added NO; -N, probably due to nitrate assimilation by the Sphagnum. Sulfate concentrations in the surface pools increased from 5 p.eq*L-' to 130 y e q -l -' with acidification and gradually decreased in the fsllswing 7 to 14 days. Pore water concentrations of SO6 decreased and H2S increased indicating sulfate reduction even in the highly acidic environment (pH 4). The decrease in concentration sf SO; in the surface pools due to SO4 reduction and assimilation was not as rapid as the decrease in NO; concentration due to plant assimilation. The dominant Sphagnum species increased in growth with the added NO; -N and SOT , particularly in the sligotrophic areas of the mire. In the minerstrophic area, only those species isolated From the water table showed increased growth due to acidification. Results here indicate that in the early stages sf acidification the mire is capable of taking up the added NO; and SO: , probably in an assimilatory reduction process which generated additional alkalinity in the mire.O n a artificiellernent acidifi6 un markcage irnproductif (3,6 ha) du nord-suest de llOntario 5 l'aide de H N 0 3 et de H2SO4 afin d'etudier Ifincidence des pr6occupations acides sur la principale espece de Sphagnum et sur la chirnie des eaux superficielles et interstitielles. Pendant ou juste apr&s I'apport d'acides, la concentration de nitrate dans les eaux supedicielies a augment6 de 0,07 ~e q 0 L ' ' NO; -N jusqu'& un niveau situe entre 20 et 70 peg-L-'. Les concentrations de NO; -N dans les eaux sous la surface n'ont pas chang6 tandis que les concentrations superficielles ssnt revenues 3 la concentration ambiante en moins d'une journke. Plus de 99 % du NO; -N &ranger a 6t6 retenu dans le marecage, probablernent 3 cause de l'assimilation du nitrate par Sphagnum. Les concentrations de sulfate dans les mares sont passees de 5 peq-L-' 3 130 ~e q * L ' -' & la suite de I'acidification et ont graduellement dirninu6 au cours des journees 7 3 14. Les concentrations de SO: dans les eaux interstitielles ont dirninuk tawdis qe celle de H2S snt augmente, ce qui rev&le une reduction du sulfate meme en milieu fortement acide (pH 4). Dans les mares superficielles, la baisse de la concentration de SOT due 2 la rkduction et 3 l'assimilation der SOT n'etait pas aussi rapide que la baisse de la concentration de NO; 3 la suite de l'...