Premium
Stream Canopy and Its Relationship to Salmonid Biomass in the Intermountain West
Author(s) -
Platts William S.,
Nelson Rodger L.
Publication year - 1989
Publication title -
north american journal of fisheries management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.587
H-Index - 72
eISSN - 1548-8675
pISSN - 0275-5947
DOI - 10.1577/1548-8675(1989)009<0446:scairt>2.3.co;2
Subject(s) - canopy , riparian zone , biomass (ecology) , environmental science , habitat , hydrology (agriculture) , tree canopy , streams , ecology , structural basin , geology , biology , geomorphology , computer network , geotechnical engineering , computer science
To assess prevailing stream canopy (riparian overstory) conditions on representative streams in the northern Rocky Mountains and the Great Basin of the western USA, we measured several riparian habitat components, including canopy density, light intensity, unobstructed sun arc, and average potential daily thermal input in grazed and ungrazed (rested) portions of each stream. We also determined to what extent, if any, these habitat components were correlated with salmonid biomass and whether either they or salmonid biomass differed significantly between geographic regions or between grazed or rested pastures. Unobstructed sun arc was significantly and positively correlated with thermal input ( P < 0.01), and it was the best overall predictor of salmonid biomass per unit volume ( r 2 = 0.58). Thermal input was a better predictor of salmonid biomass per unit volume in the Great Basin ( r 2 = 0.92) than in the Rocky Mountains ( r 2 = 0.50), where thermal regime may exert more influence on fish populations. Mean estimates of fish biomass per unit volume differed significantly ( P < 0.05) between the Great Basin (55.9 g/m 3 ) and Rocky Mountain (13.1 g/m 3 ) study areas and were better related to stream canopy attributes than biomass estimates based on stream surface area; in the Great Basin study areas, the two types of biomass estimates were only weakly correlated with each other. In the Rocky Mountains, ungrazed sites generally had more canopy cover than grazed sites. In the Great Basin study areas, however, differences in canopy were unimportant and were probably related to local management practices in several cases.