Tree encroachment in North American grasslands
Over the past century, the composition and structure of grasslands and prairies in North America and around the world has changed due to the encroachment of woody species. These species have not been introduced from other regions or countries. They are native species but started encroaching in new areas due to changes in abiotic factors such as climate and land-use management (i.e. grazing and fire). Numerous studies have observed the decrease in natural biodiversity consequent to the progressive colonization of such species. Other studies have examined optimal management strategies to reduce the spread of such woody plants. However, we still lack a mechanistic understanding of the conditions that are most favorable to successful establishment of tree seedlings and how these vary across different climates. To this end, we are setting up a multi-site experiment along a snow gradient that will evaluate the effects of inter- and intraspecific competition, grazing and fire on the growth, survival, and establishment of the eastern red cedar Juniperus virginiana, one of the most tenacious encroachers in the northeastern and midwestern United States.
Main Investigators: Samia Hamati, David Ward, Juliana Meideros |
White-tailed deer browsing pressure
This project focuses on the issue of carrying capacities in white-tailed deer populations in the surrounding metro parks. Many wildlife biologists and land managers in park systems believe there are too many deer for the amount of forage available. However, determining the optimal number of deer per unit of space has proved difficult. We are using a combination of approaches to determine how many deer these areas can support. First, we are examining deer habitat preferences using giving-up densities (GUDs). Next, we are assessing the preference and avoidance of different plant species to ascertain principal food items (principal is a function of the preference and the number of dietary items available). Lastly, we are measuring the nutritional quality of these dietary items by determining their crude protein, neutral detergent fiber, acid detergent fiber and digestibility, as well as the concentration of plant secondary metabolites (which deter herbivores). Ultimately, we will use this information in a modified version of the well-known Hobbs and Swift model to estimate a carrying capacity for deer in the areas surrounding Kent State.
Main Investigators: Matt Wuensch, David Ward |
Combined effects of deer and insect herbivory on local vegetation
This project aims at examining the relative importance of insects and large mammalian herbivores on the forests of eastern North America. We will focus on a genus of plants with a well-established phylogeny, such as Quercus (the oaks). In this way, we will be able to establish whether these trees have constitutive (fixed) or inducible defenses (variable; increase after herbivory). Differences in the heights of investment of defensive compounds in trees, such as tannins, will indicate whether these trees are focusing on defense against large mammals, such as deer, or insects. If these defensive compounds are concentrated close to the ground and below the browse line, the trees are likely defending themselves against large mammalian herbivores. However, if the defenses are evenly distributed across the entire tree, this indicates that insect herbivory is the key issue. Comparing the response of oaks grown in the greenhouse under the same conditions, but differing in the level of simulated herbivory, will help assess how these plants invest in chemical defenses.
Main investigators: Cindy Perkovich, David Ward |
Effects of nutrient fertilization and physical disturbance on biological soil crusts
This project aims to investigate biological soil crusts (biocrusts), which are abundant in many deserts around the world. Biological soil crusts occur in the open spaces between plants and consist of cyanobacteria, lichens and mosses. These biocrusts (specifically, the cyanobacteria component) are capable of fixing nitrogen, which is an important limiting nutrient for many plants in desert systems. We will utilize plots established by the Nutrient Network Global Research Cooperative at the Sevilleta LTER near Albuquerque, NM to examine the effects of nutrient fertilization (N, P, & K) on the overall abundance and nitrogen-fixing ability of these biocrusts.
A number of factors reduce the success of biocrusts, most commonly the negative impact of domestic livestock, which trample and destroy the biocrusts. Recent studies suggest that biocrust communities may take several decades to fully recover from damage. We plan to address these concerns of disturbance by conducting a piosphere study. Examining the intensity of disturbance as well as regrowth patterns in the zone of influence of grazing will allow us to better understand recovery time frames and to develop conservation strategies for biocrusts in the future. Main investigators: Lauren Baldarelli, David Ward, Heather Throop |
Our research greenhouse!
In August 2017, we were blessed with the construction of a new research greenhouse for our lab. Previously, we set up our greenhouse experiments at the KSU Geauga campus - about 45 minutes north of the Kent main campus. Equipped with high-powered grow lights and efficient heating and cooling systems, this new facility provides our lab ample space to conduct future research at just a stone's throw away from our building.