Evaluating Scaling Relationships of Branching Structure and Biomass Partitioning in Managed Orchard Fruit Species

Tests of the Metabolic Theory of Ecology for plant species are largely limited to naturally occurring species and minimally managed plantation species. My study explores if scaling relationships described for natural systems are conserved in domesticated and highly manipulated (i.e., pruned) orchard systems. I measured diameter, length, and stem biomass at a branch level for five 24 year-old minimally managed tart cherry (Prunus cerasus, P. mahaleb rootstock) trees and 19 eight year-old highly managed apple (Malus x domestica) trees with various growth controlling rootstocks at the Utah State University Kaysville Experimental Orchard. In addition to branch-level measurements, I calculated canopy volume and other tree-level architecture descriptors like branching ratio and branching path fraction. Preliminary results suggest that scaling predictions are highly conserved in orchard species independent of management intensity. For instance, trunk diameter and total stem biomass are highly correlated on a log-log scale with a nearly parallel slope to the 8/3 scaling prediction. This work also includes a strong applied component for orchard management. Canopy shape and structure models will be fitted to yield data in commercial orchards to include a constraints-based approach to horticulture where tree architecture and growth is manipulated to maximize fruit yield per resource input. The selected model will use a scaling approach influenced by the Metabolic Theory of Ecology to simulate various horticultural management strategies on tree fruit physiology.