The Mortar Creek Fire burned 26 000 ha of mixed-conifer Rocky Mountain forest
in July–August 1979. Changes in burn stream conditions were examined
relative to reference streams for various ecological factors on two to six
occasions, from October 1979 to August 1980. Factors included major ions and
nutrients, suspended and benthic particulate matter, periphyton (algae), and
macroinvertebrates. Elevated levels of most dissolved chemicals in the burn
streams were evident soon after the fire and again during spring runoff.
However, there were no major disruptions in the relative composition of
cations (and presumably of anions also) in the burn streams during the study.
Concentration (mg/L) and load (g/s) of some constituents were higher
(e.g. NO 3 -N) and of others (e.g. Ca) were lower in the
burn than in the reference streams during spring runoff, depending on whether
they were normally under biological or geological control, respectively.
Suspended sediment and particulate organic matter generally were higher in
burn streams, especially during snow-melt runoff or following heavy rain
storms. Benthic organic matter was higher in burn streams and was mainly
charcoal, compared to the usual leaf litter found in the reference streams.
Fine sediments increased and periphyton decreased in the burn streams. The
fire increased the sensitivity of the burn streams to more routine
smaller-scale disturbances, such as rainstorms, which had major impacts on the
burn streams but not on the reference streams. The macroinvertebrate
assemblage showed little direct effect from the fire but was severely altered
in composition and abundance by the subsequent runoff, scouring, and channel
alteration initiated by spring runoff. The burn streams showed considerable
individuality in their response to fire depending on the particular set of
conditions to which they were exposed.
Aspen Increase Soil Moisture, Nutrients, Organic Matter and Respiration in Rocky Mountain Forest Communities