17. Logging Effects on the Aquatic Ecosystem
349
occurred following harvesting and prescribed burning in the watershed
(Hartman & Scrivener, 1990). Average stream-water temperatures increased in the summer (by 3.2°C in August) and also in the winter (by
0.8°C in January), primarily as a result of removal of the streamside
forest canopy. Electrical conductivity (representing major cations and
anions) increased from 20 to 35 and 40 umho/cnr' during higher flows at B
and J weirs, respectively, with smaller changes at lower flows. The increases persisted for 2 to 5 years. Nitrate-N concentrations increased 2fold at B weir (40% dearcut) and 7-fold in a floodplain tributary (100%
dearcut and burned) from mean values of 0.18 mg/l. These changes
persisted up to 3 years. Phosphate-P concentrations remained unchanged
at very low levels (mean value 0.004mg/l), except for increases to a
maximum of 0.027mg/l in the floodplain tributary immediately after
burning. Forest soils tend to retain phosphorus and at Carnation Creek
the phosphorus concentrations in the stream water were only half those in
the incoming rain water (Scrivener, 1975). Phosphorus is the limiting
nutrient for algae growth at Carnation Creek and other coastal streams
(Stockner & Shortreed, 1978). Suspended sediment concentrations up to
1000mg/l were measured in small tributaries during road construction in
wet weather (Ottens & Rudd, 1977). However, suspended sediment levels
and yields in Carnation Creek remained low and changed little during and
after road construction and logging. At B weir, annual sediment yields
ranged from 17 to 44 t/km? prior to any disturbance, 13 to 33t/knr' during
logging, and 11 to 34 t/km? after logging (Hartman & Scrivener, 1990),
whereas peak suspended sediment concentrations during storm runoff
were mostly less than 75 mg/l with a maximum observed value of 560mg/l
(Tassone, 1988).
Fish production
The research has revealed a complex variety of both positive and negative
impacts on fish in relation to different life stages of the fish, different time
scales and differences among species (Hartman & Scrivener, 1990).
For example, salmon egg-to-fry survival rates were reduced by the
deterioration in spawning gravel quality. Lower densities of the very
young coho (fry) permit better survival rates. Warmer stream water
causes earlier emergence of the fry in the spring, which exposes the fry to
spring storms which can wash them out to sea but also lengthens the
growing season and permits the surviving fish to grow larger during their
first summer. Increased nutrient levels and warmer water also promote
higher growth rates and higher overwinter survival. The importance of
side-channels in the floodplain as overwinter habitat for young salmon
was a major finding (Bustard & Narver, 1975). Logging-related changes
in large organic debris, channel morphology, and streambed stability
depressed young fish survival and production .
349
occurred following harvesting and prescribed burning in the watershed
(Hartman & Scrivener, 1990). Average stream-water temperatures increased in the summer (by 3.2°C in August) and also in the winter (by
0.8°C in January), primarily as a result of removal of the streamside
forest canopy. Electrical conductivity (representing major cations and
anions) increased from 20 to 35 and 40 umho/cnr' during higher flows at B
and J weirs, respectively, with smaller changes at lower flows. The increases persisted for 2 to 5 years. Nitrate-N concentrations increased 2fold at B weir (40% dearcut) and 7-fold in a floodplain tributary (100%
dearcut and burned) from mean values of 0.18 mg/l. These changes
persisted up to 3 years. Phosphate-P concentrations remained unchanged
at very low levels (mean value 0.004mg/l), except for increases to a
maximum of 0.027mg/l in the floodplain tributary immediately after
burning. Forest soils tend to retain phosphorus and at Carnation Creek
the phosphorus concentrations in the stream water were only half those in
the incoming rain water (Scrivener, 1975). Phosphorus is the limiting
nutrient for algae growth at Carnation Creek and other coastal streams
(Stockner & Shortreed, 1978). Suspended sediment concentrations up to
1000mg/l were measured in small tributaries during road construction in
wet weather (Ottens & Rudd, 1977). However, suspended sediment levels
and yields in Carnation Creek remained low and changed little during and
after road construction and logging. At B weir, annual sediment yields
ranged from 17 to 44 t/km? prior to any disturbance, 13 to 33t/knr' during
logging, and 11 to 34 t/km? after logging (Hartman & Scrivener, 1990),
whereas peak suspended sediment concentrations during storm runoff
were mostly less than 75 mg/l with a maximum observed value of 560mg/l
(Tassone, 1988).
Fish production
The research has revealed a complex variety of both positive and negative
impacts on fish in relation to different life stages of the fish, different time
scales and differences among species (Hartman & Scrivener, 1990).
For example, salmon egg-to-fry survival rates were reduced by the
deterioration in spawning gravel quality. Lower densities of the very
young coho (fry) permit better survival rates. Warmer stream water
causes earlier emergence of the fry in the spring, which exposes the fry to
spring storms which can wash them out to sea but also lengthens the
growing season and permits the surviving fish to grow larger during their
first summer. Increased nutrient levels and warmer water also promote
higher growth rates and higher overwinter survival. The importance of
side-channels in the floodplain as overwinter habitat for young salmon
was a major finding (Bustard & Narver, 1975). Logging-related changes
in large organic debris, channel morphology, and streambed stability
depressed young fish survival and production .