Leveraging Disturbance Autocorrelation to Achieve Management Goals at Minimal Cost

Open Access
Garrison, Andrew James
Area of Honors:
Bachelor of Science
Document Type:
Thesis Supervisors:
  • Katriona Shea, Thesis Supervisor
  • Katriona Shea, Honors Advisor
  • Stephen Wade Schaeffer, Faculty Reader
  • Autocorrelation
  • Competition
  • Disturbance
  • Disturbance aspects
  • Reciprocal-Yield Law
  • Species coexistence
Ecologists have long studied the effects of disturbance on species diversity. More recently, there has been considerable interest in quantifying the various aspects of disturbance and manipulating them to influence community diversity. This thesis focuses on how disturbance autocorrelation may be leveraged to achieve management goals at a minimal cost. In the first chapter, we consider the interactions between temporal autocorrelation of disturbance occurrence and disturbance intensity at varying disturbance frequencies. Using an annual plant model, we show that when intensity and frequency are kept constant, changing the temporal autocorrelation of disturbance occurrence can also affect competitive outcomes. Additionally, we show that when species coexist, the degree of autocorrelation can affect which species reaches higher densities. We describe several examples (including prescribed burning, grazing and mowing) which outline how manipulation of temporal autocorrelation may be used to achieve conservation and eradication goals at no additional cost. Our results provide important insights for, and have potential application to, land management and conservation. While changing the intensity and frequency of human-induced disturbances can be costly, adjusting the temporal autocorrelation of disturbance occurrence may be considered a “no-cost manipulation”. In instances where a land manager lacks the funds or resources to manipulate other aspects of disturbance, such as intensity and frequency, changing the temporal autocorrelation may provide an effective, economical alternative. In the second chapter, we describe how autocorrelation of disturbance may be applied in a crop rotation setting. Crop rotation has long been considered one of the simplest and most effective tools for managing weeds. In this paper, we demonstrate how crop rotations can be strategically arranged to harness a novel mechanism of weed suppression, weed-weed competition. Specifically, we consider how crop stacking, or increasing the number of consecutive plantings of a single crop within a rotation, can decrease the size of the weed seed bank. Using an annual plant model, we investigate the theoretical effects of stacked crop rotations on weeds that have different life-history strategies and phenology. Our results show that when weeds compete within a season, stacking can reduce the weed seed bank compared to rotations without stacked crops. Although more research is needed to fully understand the effects of crop stacking on other pests and nutrient cycles, our research suggests that crop stacking has the potential to improve weed suppression without additional inputs, and their associated costs and externalities. Moreover, improving management by changing the sequence of tactics applied (the disturbance autocorrelation) is a novel, process-based approach that could likely be applied to other weed management practices, such as mowing and herbicide application, and which could involve mechanisms other than weed-weed competition. Leveraging this new and existing ecological theory to improve weed management strategies holds great promise.