Author Archives: rqthomas

Annual Lab retreat

On Thursday August 21 we had a 1st annual retreat to the metropolis of Dugspur, VA.  We welcomed Annika to the group and set our goals for the upcoming year.  It was great to see a bunch of modelers identifying the trees around the cabin.  The highlight was a massive summer thunderstorm rolling in during a hike up Buffalo Mountain.  We were all soaked!  There is a great year ahead for the research group.

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Trip to the University of Michigan Biological Station

Just returned from the University of Michigan Biological Station where I was invited to give the Bennett Resarch Seminar.  Many thanks to the folk at UMBS including my hosts Chris Gough and Knute Nadelhoffer for an intellectually stimulating and enjoyable few days at “Bug Camp”.  While at UMBS Knute and Chris showed me the AmeriFlux tower, the FASET Study, the burn chronosequence, the nitrogen addition experiment, and a 200+ year “old-growth” forest.  Some pictures from the trip are below. IMG_2189 IMG_2190 IMG_2184 IMG_2181 IMG_2177 IMG_2175 IMG_2174

Welcome Dr. Horn!

We welcome Dr. Kevin Horn to the EPICS Research Group!  Kevin is a post-doctoral scientist and a USGS Powell Center Fellow.  He joined the group in April as part of a USGS-funded synthesis project to study how nitrogen deposition is altering forest growth and mortality across the continental U.S.  Prior to arriving to Virginia Tech, Kevin completed his Ph.D. in ecology at BYU in Utah.

New flux tower up and running

We have been spending the spring and summer setting up a new eddy-covariance tower to measure the carbon and water dynamics of a floodplain near campus.  The 3-m tall tower includes high frequency measurements of carbon dioxide, water, wind speed, air and soil temperature, humidity, radiation, soil moisture, and soil heat flux.  We are going to use it to study how the hydrologic dynamics at the site influence the carbon balance of the ecosystem and for general instruction in ecosystem-climate interactions.  The system is a collaboration with the Department of Biological Systems Engineering and their STREAM Lab.  Below are pictures from the last few months as we set the system up.IMG_2126

 

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Trip to the German Alps to teach a climate-carbon course

I just returned from a brief trip to Garmisch-Partenkirchen, Germany, where I was an instructor in the Mechanisms and Interactions of Climate Change in Mountain Regions Summer School, based at the Institute of Meteorology and Climate Research (KIT/IMK-IFU) .  This summer’s topic was “Examining Mountain Ecosystems in Regional to Global Environments of Carbon-cycling and Climate (EMERGE-CC)”.  My colleague Ankur Desai at the University of Wisconsin and a visiting scientist at KIT/IMK-IFU during his sabbatical was an excellent organizer and host.  Thanks to the students and KIT/IMK-IFU for a fun and productive visit.  What a beautiful place (see the view from my hotel below)!

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Synthesis project funded to forecast the impact of N deposition on trees

We have recently been selected by the USGS John Wesley Powell Center for Analysis and Synthesis to co-lead a 2-year synthesis project to study the impacts of N deposition on tree growth and mortality! The other co-leads are Linda Pardo at the US Forest Service, Erica Smithwick at Penn State, and Gregory Lawrence at the USGS.  We look forward to stimulating working group meetings in Fort Collins, CO.

Project summary: Nitrogen deposition is altering forest dynamics, terrestrial carbon storage, and biodiversity. However, our ability to forecast how different tree species will respond to N deposition, especially key response thresholds, is limited by a lack of synthesis across spatial scales and research approaches. To develop our best understanding of N deposition impact on tree growth and survival, we will integrate plot level studies describing plant growth and survival responses to N inputs and plant available soil nutrients with a continental scale analysis across a N deposition gradient. Our primary outcome will be estimates of tree response to N deposition with explicit representation of uncertainty and the identification of thresholds that will directly inform critical load estimates used in management and policy by many government agencies. The proposed work is timely as critical loads were recently incorporated into the USFS Forest Plan process and, most significantly, critical loads will be utilized by EPA in evaluating the merits of setting a secondary standard to protect ecosystem health as part of the new NOx/Sox review cycle which began earlier in 2013.

New paper evaluating nitrogen limitation in global models

A new paper came out in this month’s issue of the journal Global Change Biology.  An increasing number of global models that include a representation of how nitrogen limits production of carbon and biomass in forests, grasslands, and crops are being used to predict global climate and help inform climate policy.  We evaluated how well two widely-used global models with carbon and nitrogen cycles represent nitrogen limitation by comparing model simulations to data from forests and grasslands.  The model response to simulated nitrogen fertilization differed drastically between models but the average of the two models compared well to observations.  In the paper we explore why they are different and how to potentially advance the models.  This was the first study to systematically evaluate multiple global models that include the nitrogen cycle and will hopefully help guide the improvement of models and collection of additional observational data.

Thomas, R. Q., S. Zaehle, P.H. Templer, and C.L. Goodale. Global patterns of nitrogen limitation: Confronting two global biogeochemical models with observations. Global Change Biology 19, 2986–2998

 

New paper from Hawaiian field course

A new paper came out this week from a field course that I was involved in while a Ph.D. student at Cornell University.  My department took ~20 graduate students to the Big Island of Hawaii where we explored the diverse ecosystems and developed group projects.  Of course we also spent plenty of time on the beach!  One of the most memorable experiences on the course was listening to local elders talk about their relationship with the land.  It was moving to hear them explain how the trees were more than plants growing out of soil and an extension of their ancestry and heritage.

My group decided to study an invasive wasp that is killing the beautiful Wiliwili trees on the island (see picture).  Numerous techniques have been used to kill the wasp, including the release of a predator of the wasp as a biocontrol.  We measured the health of Wiliwili trees before the biocontrol release and the field course 2-years later remeasured the health after the release.  We found that the recovery depended on where the tree was located across the landscape.

 

New paper studying how we mathematically represent the impact of nitrogen deposition on carbon storage

The deposition of nitrogen from the atmosphere to forests can increase the amount of carbon stored in forest ecosystems.  This reduces carbon dioxide in the atmosphere and helps cool climate.  Therefore it is important to include nitrogen deposition and its impact on forest carbon storage in climate models that are used to predict how human emissions of greenhouse gases lead to a changing climate.  In a recently published paper in the journal Biogeosciences, we investigated how different mathematical representations of carbon and nitrogen cycles led to better or worse predictions of how nitrogen deposition alters carbon storage. The paper advances our understanding of how to test and evaluate models while presenting a new modeling approach in important climate model.