Title Description Research Sites Related Links
Douglas Lake Water Profiles

Water temperature and dissolved oxygen profiles for various parts of Douglas Lake. These profiles span a number of investigators, time periods and locations within Douglas Lake so pay attention to the Dataset details.

Food availability and adult mortality in house sparrow populations

I will be collecting an invasive bird species, the House Sparrow, from farms located off of UMBS property. I will examine two historically important hypotheses of avian clutch size patterns, 1) the food availability hypothesis and 2) the adult mortality hypothesis. I will test these hypotheses in a single species, the House Sparrow, at three sites that differ in clutch size and latitude. The House Sparrow is a suitable model organism for studying avian clutch size patterns because House Sparrow clutch sizes have changed as House Sparrows have spread across North and Central America. This change in range and clutch size has resulted in a latitudinal clutch size pattern that parallels the latitudinal gradient seen in other bird species. Moreover, this change is relatively recent, occurring only in the last 150 generations. I also will examine potential proximate mechanisms controlling avian clutch size. I will study two hormones, 1) plasma prolactin and 2) the hypothalamic neuropeptide vasoactive intestinal polypeptide, which are known to control incubation onset and cessation of laying in turkeys. I will characterize how these hormones vary across the laying cycle, and use this information to make informed pharmacological manipulations in House Sparrows and look for a concomitant change in clutch size. It is only by understanding the proximate and ultimate mechanisms of clutch size differences in birds that researchers can develop and test hypotheses to solve a long unanswered question in life history research and uncover how and why birds vary reproductive effort across latitude.

Atmospheric modeling directly above the forest canopy

Current atmospheric modeling represents both the biosphere and the atmosphere directly above the forest canopy as coarse boundary conditions. The biosphere is expressed as a 2-D surface that does not take into account specific qualities of the forest canopy (i.e. canopy height and crown size). Directly above the forest canopy, it is assumed that mixing allows us to ignore canopy heterogeneity. Present research suggests that a more high-resolution 3-D canopy is needed for a more accurate representation of the interaction between biosphere and atmosphere.

This research will utilize the UMBS FASET and AmeriFlux sites to study the canopy structure and to further develop the RAFLES atmospheric modeling software developed by Dr. Bohrer. This software simulates the interactions among these canopy structures and wind, as well as fluxes of water vapor, heat, and CO2 using a biosphere-atmosphere high resolution large eddy simulation model that resolves 3-D explicit forest canopies. My hypothesis is that by taking the explicit 3D canopy structure into account, we will be able to model phenomena such as increased fluxes over gaps, tree-scale patterns of soil moisture, and modifications to the effective aerorodynamic roughness length of the forest. These phenomena, with strong effects on both the forest ecology and the atmosphere, cannot be resolved with a coarse model that does not resolve tree-scale structures at the biosphere-atmosphere interface. Along with atmospheric modeling, closed system automated chambers previously installed at the FASET and AmeriFlux sites at UMBS will be used to quantify links between soil respiration and the turbulent dynamics of the canopy.

The effects of the neuromodulator serotonin on orientation behavior in crayfishes

I will be running 2 research projects this summer. I will have at least one undergraduate student attending the station with me. The student and I will be examing the effects of the neuromodulator serotonin on orientation behavior in the flume at the Stream Research Facility. I will also be continuing work with Dr. Paul Moore on Douglas Lake, examing population and social structure of the crayfish, Orconectes rusticus, in Douglas Lake.

Freshwater Benthic Algal Response to Elevated Carbon Dioxide

The effects of elevated atmospheric carbon dioxide on freshwater algae are relatively understudied, though terrestrial plants grown under elevated atmospheric carbon dioxide concentrations have been shown to produce increased biomass, structural compounds and chemical defenses. If similar effects occur for freshwater algae, impacts would propagate through other trophic levels of aquatic ecosystems. In this study, flow-through systems will be used to simulate a temperate stream. Benthic algae will be grown under ambient (380 ppm CO2) and elevated (1,000 ppm CO2, a worst-case scenario under a fossil fuel-intensive future world) CO2 conditions. Changes in biomass, community dynamics, pigment production, and chemical defenses will be quantified. The study will improve understanding of elevated CO2 effects on a freshwater ecosystem and contribute towards understanding of the role of freshwater algae in carbon capture and storage and in the future global carbon cycle.

UMBS Stream Research Facility
Combining long-term (> 12 yrs) C cycling measurements and a novel large-scale experimental manipulation with modeling studies

At UMBS we are combining long-term (> 12 yrs) C cycling measurements and a novel large-scale experimental manipulation with modeling studies in an effort to improve regional projections of forest C storage. Our goal is to explain the physical, biological and ecological mechanisms by which forest C storage will change in response to disturbance and succession, and to current and long-term climate variation. The Forest Accelerated Succession ExperimenT (FASET), in which all aspen and birch trees (~35 % LAI) within a 39 ha study area were stem girdled, is testing the hypothesis that forest C storage across much of the upper Midwest will increase due to increasing structural and biological complexity of the emerging plant communities and because of a redistribution of nitrogen from senescing aspen and birch to the developing canopy.

Phenology shifts in northern forest ecosystems

Large-scale phenological shifts, or timing of key life events, have been observed across many ecosystems and are consistent with changes expected with climate change. With annual temperature increases of roughly 0.2 degrees C, advancement in the timing of budburst and flowering have been widely observed. Earlier budburst and therefore longer growing seasons may have significant implications for carbon storage. Previous research has shown that increases of only one day in growing season have significantly increased forest net ecosystem productivity (NEP). However, the relationship between earlier budburst and NEP is not well established. Kellen’s research will examine the connection between phenological events at the species levels and phenological timing at the stand scale.

In contrast with the more evident relationship among increased temperature, earlier onset of budburst, and increased NEP, the connections between phenology and local, boundary-layer meteorology are much less understood. Leaf-out has been correlated with a wide variety of meteorological components including temperature, vapor pressure, and relative humidity. Kellen’s research will use precise phenological and meteorological observations to develop climate-biosphere models and determine the effects of phenological shifts on the climate-biosphere linkage so these findings can be incorporated into climate models.

Changes in timing of autumnal senescence have also been widely observed, although changes are more variable between ecosystems and more poorly understood than budburst events. Delayed leaf abscission may cause incomplete resorbtion of nutrients to storage organs as well as less N.

1. Have shifts in the timing of spring phenology occurred at Wauseon, OH in comparison to legacy data sets from the 1880's-1913? 2. How will shifts in both spring and autumn phenology impact carbon storage dynamics in northern forest ecosystems with the shift from aspen and birch dominated canopies to more heterogeneous oak and maple forests? 3. How will shifts in timing of leaf fall impact nutrient resorption dynamics? 4. What are key meteorological drivers of phenological events?

Plant species release of biogenic volatile organic compounds (BVOC)

Many plant species are known to release biogenic volatile organic compounds (BVOC) into the atmosphere (Kesselmeier and Staudt, 1999). Specific volatile chemical species emitted include terpenoid (e.g., isoprene, monoterpenes, and sesquiterpenes) and non-terpenoid (e.g., methanol, acetaldehyde, acetone) volatile organic compounds. Reactive terpenoid emissions significantly impact regional air quality, global climate change, and other atmospheric processes. Specifically, they contribute to secondary organic aerosol formation (SOA), impact ozone concentration and nitrogen cycling, and serve as a carbon sink. (Bonn and Moortgat, 2003; Monson and Holland, 2001; VanReken et al., 2006; Atkinson and Arey, 2003). Current state-of-science models estimate BVOC emissions based on temperature, solar input, and soil moisture (Guenther et al., 2006). However, studies indicate that air pollutants and other stressors, such as ozone, nitrogen oxides, and methyl jasmonate (a plant signaling compound and proxy for herbivory), may significantly impact terpenoid emissions as well (Blande et al., 2007; Himanen et al., 2009; Martin et al., 2003; Pinto et al., 2007; Cape, 2008). Additionally, several recent studies suggest that the BVOC currently measured are insufficient for explaining observed oxidant removal rates or SOA concentrations and growth, leading to the possibility that atmospheric relevant emissions are as yet undetected. Determining the effects of pollutants and other stressors on BVOC emissions, and the subsequent impact on SOA formation, is crucial for improving model estimates and predicting the effects of climate change. The purpose of this investigation is to determine the effects of air pollutants and other stressors on terpenoid emissions from White Pine and Red Oak trees. H1: Increased pollutant exposure will result in a change in total BVOC emissions. H2: Branches treated with methyl jasmonate will display an increase in BVOC emissions. H3: Exposure to increased concentrations of ozone or methyl jasmonate will significantly alter the terpene emission profile.

Linking Heterogeneity of Above-Ground and Subsurface Processes at the Gap-Canopy Patch Scales to Ecosystem Level Dynamics

Trees control soil moisture by drawing water through the roots and transpiring them to the air. They also lead to an opposite effect of reducing evaporation from the soil to the air by shading the ground and reducing the wind speed near the surface. Current watershed models simulate soil moisture at regional scales (tens to hundreds of km) and use extremely simplified representations of the interactions between vegetation and soil moisture. The differences between individual crowns and the effects of the canopy structure are not represented in these models. This project aims to improve our understanding of the relationships between evaporation, transpiration and soil moisture in heterogeneous forest canopies, and how these relationships affect soil moisture heterogeneity from the tree scale to the ecosystem and regional scales.

A combination of detailed observations and state-of-the-art high-resolution modeling tools will be used. A modeling system will be developed, which will include two models: (1) a canopy-resolving atmospheric large eddy simulation (RAFLES) to simulate the wind, humidity and temperature of the air at a resolution smaller than individual tree crowns. This model will also simulate the transpiration of individual trees; and (2) a physically-based watershed hydrology model (tRIBS-VEGGIE), also capable of operating at a resolution of a few meters. Novel radar-based volumetric observation of soil moisture, and in and above canopy micrometeorological measurements will be used to evaluate the models results.

The project will capitalize on the existing wealth of data and on-going diverse observations at the University of Michigan Biological Station (UMBS). Specifically, the coupled modeling system will be used to simulate two forest patches within the experimental and control plots of the Forest Accelerated Succession ExperimenT (FASET), a DOE-NICER funded study, in which manipulations of the canopy structure simulate a shift from mid- to late-successional tree community. The proposed project will lead to new understanding of how the small-scale structure of forests affects the atmosphere and soil moisture heterogeneity at larger scales, which will advance our capability to predict the effects of ecosystem structure at multiple scales on the exchanges of energy water and CO2 with the atmosphere, and on the functioning of the regional watershed. Such advancement is particularly important in conditions of changing climate and increased human disturbance to forests, which are expected to increase the spatial heterogeneity of forests and other important natural resources. Furthermore, the study will upscale, for the first time, a mechanistic model of fine-scale (few meters) canopy-structure to a regional scale (few km), using a hydrological model capable of resolving vegetation and topography in heterogeneous domain. This will create a tool that will have a truly transformative value in the hydrological and ecological sciences.

Modelling forest growth, succession, and biogeochemistry to study the effects of disturbances on forest carbon cycling

Due to heavy logging and intense fires at the beginning of the twentieth century, the forests at UMBS are characterized by an early successional state dominated by short-lived tree species such as aspens and birches. As these species approach the end of their life span, they are expected to die off and be replaced by longer-lived, more shade-tolerant species such as white pine and red oak. These successional changes happen over a long time scale that is difficult to resolve with field observations, and may have important impacts on carbon, nutrient, and water budgets in the forests at UMBS. I am using a combination of measurements and computer modeling to characterize the effects of succession on CO2 and volatile organic compound (VOC) fluxes to the atmosphere.

I am using the LANDIS-II computer model to develop predictions of future carbon budgets at UMBS. This model simulates tree growth, establishment, mortality, and succession. The model will be parameterized using CO2 flux measurements from the FASET and Ameriflux towers, as well as aboveground biomass measurements from a number of permanent plots. The historical data from these plots will help to constrain model predictions of long-term biomass accumulation. VOC flux predictions will be constrained using measurements from a relaxed eddy accumulation (REA) system. Measurements were conducted at both the FASET and PROPHET towers in order to measure the differences in VOC emissions between forest successional stages.