Life Sciences Commons^™

Sources Of Variability In Agronomic Weed Seed Predation: Time, Space, Habitat, And Hyperpredation, Sonja K. Birthisel

Electronic Theses and Dissertations

Weed seed predation is an ecosystem service that benefits farmers by decreasing seedbank inputs, thereby reducing weed pressure in subsequent growing seasons. Seed predation can be considerable, but is highly variable. Sources of variability may include time, space, habitat, and trophic interactions such as hyperpredation. Two experiments were conducted to measure the impacts of these sources of variability on weed seed predation rates in Maine mixed vegetable agroecosystems.

Chapter One of this thesis describes a series of landscape-level field experiments conducted to quantify the effects of time, space, and habitat on seed predation rates. Seed assays, with and without vertebrate …

Production Ecology And Stand Dynamics Of Young Acadian Forest Stands In Response To Silvicultural Intensity And Compositional Objectives, Andrew S. Nelson

Electronic Theses and Dissertations

Early successional stands are common across the Acadian forests of eastern Canada and the Northeastern US. However, productivity and dynamics of these stands, as well as the underlying mechanisms influencing these processes, under different management scenarios are poorly understood. To address this need, I used a factorial experiment that controlled silvicultural intensity and species composition to quantify the effects of varying treatments on early stand dynamics, and the physiological and morphological factors influencing tree performance . Specifically, I studied: 1) species differences in aboveground allometrics, 2) light capture, light-use efficiency (LUE; growth/light capture), and foliar carbon isotope composition (δ13C) of …