Johannes M.H. Knops
Date of this Version
Funk, K.A. 2017. Resource allocation for acorn production: A comparison across species pairs of oaks with contrasting acorn production patterns and water use strategies. Ph.D. dissertation. University of Nebraska - Lincoln.
Mast seeding, or masting, is a phenomenon where inter-annual seed production by individuals is synchronized across a population of plants. Masting is hypothesized to confer a selective advantage to plants by increasing rates of pollination or by decreasing rates of seed predation. Masting can also play a crucial role in ecosystem functioning as fluctuations in annual seed crops correspond with fluctuations in seed predator populations, which in turn have consequences that ripple throughout food webs. The mechanism(s) that causes masting is unresolved, but the high variability in seed production of masting plants is hypothesized to be caused, in part, by resource limitation. One hypothesized mechanism for masting that has gained support in recent years is known as the resource budget model (RBM). The RBM hypothesizes that plants store up resources across years until a threshold is reached, after which they flower and set seed, which depletes resources. It is still unknown how common the RBM is in masting species, and it is unknown whether the RBM describes a pattern of resource allocation that is distinctive of masting species, or if non-masting plants exhibit similar patterns. In this dissertation, we seek to resolve some of this uncertainty by comparing patterns of resource allocation and seed production among four species of California oak trees and shrubs. In Chapter 1, we test predictions of the RBM in two shrub species, one masting and one non-masting, in the Klamath Mountains of northern California. In chapter 2, we explore the carbon demands for acorn development of the masting species used in Chapter 1, in order to learn more about whether carbohydrates are limiting for seed production in this species. In Chapter 3, we use two masting tree species in central coastal California with contrasting water use strategies to test for resource limitation to flowering and seed production, and to compare which nutrients are the most important for each species. Overall, we found evidence for resource-limited reproduction in all three masting species. Furthermore, differences in patterns of seed production and in species traits matter for how resources are used for seed production.
Advisor: Johannes M. H. Knops