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The Effect of Above and Belowground Herbivory by Invasive Weevils on Forest Dynamics: Effects on Individual Tree and Forest Community Survival, Growth, Biomass and Nutrient Partitioning, and ProductivityEPA Grant Number: F6F21418
Title: The Effect of Above and Belowground Herbivory by Invasive Weevils on Forest Dynamics: Effects on Individual Tree and Forest Community Survival, Growth, Biomass and Nutrient Partitioning, and Productivity
Investigators: Coyle, David R.
Institution: University of Wisconsin - Extension
EPA Project Officer: Jones, Brandon
Project Period: September 1, 2006 through September 1, 2009
Project Amount: $111,172
RFA: STAR Graduate Fellowships (2006) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Forest Entomology
This project will use manipulative field studies, supported by controlled experiments in an artificial setting (potted plants), to measure the impact of root herbivory by exotic weevils on yellow birch and sugar maple seedlings. Field experiments will be conducted in the southern Upper Peninsula of Michigan in areas with known weevil populations. We will augment or reduce larval densities in some treatments, and closely monitor seedling growth and fine root dynamics. We have chosen a study area for long-term monitoring, and we implemented treatments and began minirhizotron observations in 2005. Controlled experiments will be conducted at the University of Wisconsin-Madison. An assay using potted yellow birch trees was begun in 2005; this assay will allow multiple years of weevil infestation with yearly destructive harvests to determine the effects of root herbivory on seedling growth and biomass allocation.
The objective of this study is to determine the effects of herbivory (primarily root herbivory) by invasive weevils on individual seedling health, fine root dynamics, and forest community composition.
I will use two known systems to test the effects of root herbivory on tree health and growth. First, I will conduct a controlled assay using the invasive root weevil Polydrusus sericeus on potted yellow birch (Betula alleghaniensis Britt.) seedlings in greenhouse coldframes. Additionally, I will conduct a similar experiment in the Ottawa National Forest using natural populations of the invasive weevil Phyllobius oblongus in a sugar maple stand.
My work will quantify the effects of above, and especially belowground, feeding by two invasive weevil species on tree health and fine root dynamics in a natural forest system. Few studies have attempted to document belowground herbivory in forest ecosystems despite ample indirect evidence that substantial herbivory occurs both above and belowground. As a result, belowground herbivory may be undervalued as a mechanism for root turnover. Stevens et al. (2002) imaged minirhizotrons weekly and found a large number of roots that died or disappeared within days of being produced, some without a senescence period, suggesting belowground herbivory. However, they did not explicitly identify soil-feeding herbivores, and thus made only speculations regarding the fine root disappearance mechanisms. A broad-spectrum insecticidal soil drench significantly increased fine root lifespan and production in a peach orchard (Wells et al. 2002) and increased root biomass in a pine stand (Stevens & Jones 2003). Both of these studies sampled soil fauna, yet neither observed actual root herbivory taking place. While their studies provide strong circumstantial support for the negative impacts of belowground herbivory, I feel that using a known belowground herbivore and host plant will provide a more effective means to test these questions.