| dc.description.abstract | This study examines some effects of clearcutting and
road-building on streams in the vicinity of Fundy National
Park, New Brunswick. Sixteen streams were selected for
sampling: four were reference streams located within mature
forest in the park, and twelve streams drained nearby
clearcuts 4-20-years old. Streams were selected on the basis
of similarities in stream order, size, and accessibility.
Along each stream, sampling was centred around a 25-m reach,
with at least one riffle, and with depth and width similar
across streams. From May to November, 1993, each stream was
sampled for temperature, dissolved oxygen, major ions,
sedimentation and bedload movement, substrate type and
concentration of organic carbon, 0 channel dimensions, riparian
vegetation, and invertebrates (the latter sampled using
gravel-filled rockballs, placed in sampling reaches for six
weeks).
Harvesting within the riparian zone reduced canopy
shading, reduced cover of aquatic bryophytes, removed large
trees and snags, and increased densities of shrubs (primarily
Alnus rugosa). Riparian buffer strips reduced these effects,
provided they were wide enough to ensure shading of the stream
channel and feeder springs, withstand windthrow of riparian
trees, and supply inputs of large woody debris. In general,
with or without a riparian buffer, streams draining harvested
areas had warmer water and greater temperature fluctuations,
and larger nutrient concentrations and sedimentation rates
than streams draining reference watersheds. Most of the
highest rates of sedimentation occurred downstream of logging
roads, while most of the lowest rates were recorded in
reference streams. Three of the reference streams had similar
properties and were fairly distinct from the cutover streams,
and from the fourth reference stream, which was logged in the
1920s.
Clearcutting appeared to have a negative influence on the
abundance of Chironomidae and Nymphomyiidae, and positive
influences on Plecoptera, Elmidae, and 01 igochaetes. The
overall abundance of invertebrates colonizing rockballs was
strongly correlated with age of stand, with the greatest
numbers occurring in reference and older cutover streams, and
the smallest numbers in the most recently cutover streams.
The numbers of invertebrates colonizing rockballs in the older
cutover streams were similar to those of undisturbed streams.
This occurred despite the slower recovery of stream energetic
processes in the older cutovers, as indicated by a principal
components analysis of physical, chemical, and biological
variables. | en_US |
