Crown biomass response of 7 year old Pinus radiata D. Don to fertilisation and thinning
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
Within-crown and total tree biomass of 7 year old Pinus radiata D. Don was followed for two years in response to thinning and N fertilisation in a 2² factorial. A non-destructive biomass estimation procedure is described whereby individual tree crown biomass components are predicted from total enumeration of branch diameters of sample trees and independently calculated regressions of biomass components on branch diameter. Estimates of regression coefficients from whole-tree biomass data and from branch data sampled from individual trees in the field are comprehensively analysed. Green crowns were stratified into zones for sampling and predictive purposes; the strata were biologically defined by year of branch initiation and branch cycle number. The effectiveness of crown stratification is evaluated. Non-destructively predicted foliar weights are compared with known weights to gauge accuracy and precision. Within-crown foliar biomass response was closely related to branch diameter response. Over bark volume increments were measured on the same trees for which foliar biomass estimates were made. Annual volume response 1 year after treatment was successfully predicted as a function of tree foliar weight and foliar efficiency. Mean tree volume increment (1978-1979), of the fertilised plus thinned treatment, after adjustment for initial volume differences, was 73% greater than control. The difference predicted from 1978 tree foliar weight estimates and foliar efficiency was 63%: 38% associated with increased tree foliar weight and 25% with increased foliar efficiency. This last result is examined in the light of other findings.