Exploring Chemistry in the Reserve, By Marilyn Fogel

(Oct. 26, 2013) About once a week since the dead heat of summer, I’ve been heading out to the Vernal Pool and Grassland Reserve with Chris Swarth and my research assistant David Araiza. In July and August, as temperatures soared to over 100°F, we started out at 7 am when the landscape was still cool. Our mission was to collect dried grasses for residual dry matter (RDM) measurements, which entailed scissors and a balance for weighing the samples back in the Lab. As a new faculty member with a laboratory barely getting off the ground, we had the “technology” for RDM measurements. As we ventured out each week, we grew to know the roads, the cattle stock ponds, the hills, and the landscape in general. Chris obtained the gate key to the northern boundary road, and we were treated to a largely untouched rolling grassy vista with the Sierras in the distance and the campus seemingly far, far away. We snipped our dried plants, and at each location throughout the Reserve we scooped up some near surface soils. As a Biogeochemist, I'm interested in nitrogen cycling in ecosystems, a topic that has received little attention in vernal pool environments. As my lab developed, I started analyzing simple nutrients in the soils; we ground up the plants in a colleague’s lab; then we analyzed carbon and nitrogen contents of both dried plants and soils at UC Merced’s Environmental Analytical Laboratory (EAL).

The amounts of nitrogen-containing nutrients far exceeded anything that I’ve ever measured and were unexpected. The methods and standards were tested, retested, and what stands is that surface soils all over the Reserve have extremely high levels of both ammonium and nitrate. Reviewing the literature for California ecosystems, it is little wonder that this ecosystem, which has never been plowed, has collected all of the fertilizers, dairy emanations, and airborne particles that have been deposited from the atmosphere, probably since the end of World War II when agriculture in the San Joaquin Valley kicked into high gear. Vernal pools, the home of many unusual and rare species, have been impacted not just by the relatively benign grazing of cows, but by the addition of copious nutrients from environmental activities that blow in from the west.

We now have many questions to ponder. What difference does this make to the plants and animals that live in the Reserve? Does the nitrogen stimulate more productivity? Does it cause eutrophic conditions in the pools? Are there unusual metals, like selenium, in the soils that might affect the distribution of plants or animals? Are there changes in the food web structure that might be affected? We don’t know the answers, of course, but we’re onto the next steps.

David Araiza is working with Liying Zhao at the EAL to measure the concentrations of about 20 interesting chemical elements in the soils. Samples are also being analyzed for their stable isotopic compositions, natural tracers of the source and processing of the nitrogen that we found in soils. And, this spring I plan to use the Reserve to introduce my Ecology students to the natural world. Where ever we go with this work, as the fall rains begin and the pools fill, we’ll learn many new things. That is, indeed, one of the beauties of science. We may not discover a breakthrough into the cause and treatment of cancer, but we’re asking relevant ecosystem questions, and we're discovering and building a study site that hopes to have many scientists of all stripes coming here in years to come.

Date 
October 26, 2013