Growth and nutrient relations in black cottonwood in South-Coastal British Columbia

Donald S. McLennan
Initially, the study examined within and among site temporal and spatial variation of foliar nutrients, and spatial variation of soil nutrients to assess the sampling methods employed, and to provide background for the interpretation of nutrient-site index interactions. The study then examined relationships between the growth of black cottonwood, expressed as site index, and site units, under story vegetation, soil nutrient contents, and foliar nutrient concentrations in29 black cottonwood
more » ... ack cottonwood stands in south-coastal British Columbia. The final phase of the study was a fertilizer trial in three juvenile black cottonwood stands, with treatments based on used DRIS diagnosis of limiting nutrients. Significant levels of variability in foliar nutrient concentrations were identified within tree canopies, and from tree-to-tree within stands. A protocol was suggested to standardize sampling procedures to reduce spatial variability. Sample size requirements for different levels of accuracy and precision were presented. Important variation in foliar nutrient concentrations was also recorded seasonally, and from year to year, in foliage samples collected according to the same protocol. It was shown that the temporal variability was sufficient to alter the interpretation of foliar nutrient concentrations for the stands. Spatial variation in soil nutrient concentrations was high and was attributed to order-of-magnitude concentration differences between soil strata in each pedon. Spatial variation of soil nutrient contents (expressed in kg/ha over a 1 m sampling depth) was generally higher than soil nutrient concentrations, because of factors such as bulk density and percent coarse fragments that were used to calculate soil contents, and that are themselves subject to variation. It was shown that the compositing procedure used to reduce costs approximately doubled the variability seen in the intensively sampled sites, and alterations to the compositing procedure were suggested. It was also argued that sampling over a depth of 1 m [...]
doi:10.14288/1.0075152 fatcat:nhtcipgkazbrhajuvcd7ekdeom