Last semester I visited Elizabeth de la Reguera’s study sites on the Eastern Shore of Maryland. We prepared and planted small research plots with switchgrass, barley and wheat. Elizabeth is studying the effects of saltwater intrusion on crop productivity and survival. Over winter break, I continued to work on this research by gathering data on how well the different plant species were growing in each plot. The AgroEcoLab manager, Cullen McAskill, gave me hundreds of pictures from the site, and I got to work! Cullen had placed a quadrat on the plots in the fall, so that we could determine the species of different plants within a grid. Imagine trying to count each plant individually in each plot! Instead, the quadrat is placed at each plot in random so that it isolates an area that can then be used to represent how much of that plant species is in that plot. My job was to take each picture individually with the quadrats and set a scale in which we would tell the program, SamplePoint, to count how many plants were within those quadrats. Gathering all this data will not only tell us what species is doing the best or worst in salty conditions, but it will also provide us with the information we need to improve any management techniques in the future.
-By Karla Rosales Lobos
On Tuesday, 9 Jan, the AgroEcoLab's work on saltwater intrusion was featured in Maryland Public Television's weekly show, Maryland Farm and Harvest.
Check out the full video here.
A few weeks ago, I visited the experiment that Elizabeth de la Reguera has established for her Master’s degree at the University of Maryland. The question for her experiment is, what is the effect of saltwater intrusion on the productivity and survival of different plant species? We travelled to Eastern Shore of Maryland to till her plots and plant switchgrass, barley, and wheat. We used rakes to till the plots because we did not want to till too deeply, which would degrade the soil. We only needed to ensure good seed-to-soil contact, to help the plants germinate and prevent them from being blown away by the wind (grass seeds are REALLY small). Then, each type of seed was assigned to one person to disperse on the plots. The purpose of this is to have some kind of uniformity when it came to the dispersion of the seeds. While we were there we took water samples from the lysimeters that Elizabeth had already installed. When we came back from field, I started to measured the porewater conductivity and pH. The soils and porewater have high electrical conductivity, which is likely due to the high levels of chloride and sulfate moving into the plots with saltwater.
- By Karla Rosales Lobos
It is important to remember that agricultural systems are ecosystems themselves, albeit human-created, and are not closed to the surrounding environment. This is fundamental to understanding why agroecology is so important, as it addresses the balance between human well-being and
environmental health. Excessive nutrient application to agricultural fields poses serious risk to the surrounding aquatic ecosystems in the watershed, for too much nutrient runoff into water bodies can trigger a cascade of events that eventually depletes all or most of the oxygen in the water. This process is called eutrophication, and not only is it is toxic to fish and all oxygen- requiring life present in the water, it is also harmful to humans who depend on these ecosystems for harvesting food (Howarth 2008). By understanding how to best manage the balance between nutrient application and cover crop usage, farmers can make the most sustainable choices to both protect the environment and preserve their own livelihoods as well as those of future generations.
- By Alexis Boytim
Howarth, Robert W. 2008. Coastal nitrogen pollution: A review of sources and trends globally and regionally. Harmful Algae, (8): 14-20.
Di, H. J., K. C. Cameron. 2002. Nitrate leaching in temperate agroecosystems: sources, factors, and mitigation strategies. Nutrient Cycling in Agroecosystems, (46): 237-256.
A couple weeks ago, I went on a field trip for my Wetlands Ecology class to learn about different types of wetland ecosystems. We followed the Patuxent River along a salinity gradient from freshwater (less than 0.5 parts per thousand (ppt) salinity) near the head of the river to salt water towards the mouth of the river, which drains into the Chesapeake Bay. The first stop was at Patuxent Wetland Park, a freshwater wetland. We saw firsthand the ways that wetland plants adapt to the stresses of a low oxygen environment. Soil is a mixture of particles separated by spaces called pores. In many ecosystems, these pores are filled with a mixture of water and air. In wetlands, these pores are frequently or permanently filled with water and plant roots cannot acquire oxygen through them. Therefore, they have special adaptations to fill their oxygen needs. For example, the water lily uses aerenchyma, or spongy tissue with air channels to pipe oxygen from above the water table down to its roots. Our second stop was at the Clyde Watson Boating area where the salinity ranged from about 5 to 7.5 ppt. We noticed salt buildup on the leaves of many of the plant species here. These plants adapt to saline conditions by extruding salt through specialized glands. It was a hot day and everyone decided to cool off in the river in their full chest-wader getups. The third stop was a salt marsh at Island Creek Marina where the salinity ranged from about 10 to 12.5 ppt. Here I spoke to the class a bit about my work in these ecosystems. We passed around a soil sample for everyone to smell the hydrogen sulfide produced by the specialized microbes that colonize salt marsh soil. I knew the rotten egg smell well from this past summer’s research and I felt right at home as I excitedly nerded-out to the class about redox conditions. At each of these sites, we split into groups and took a vegetation survey using a PVC quadrat. This allowed us to determine the dominant plant species present in each wetland type. We noticed how dramatically the plant species composition shifted with these salinity changes. Specifically, plant biodiversity dropped sharply as salinity increased from site to site. As an impromptu final stop, the group decided to check out Battle Creek Cypress Swamp, which contains one of the northernmost stands of Cypress trees in the United States. We noticed the stubby cypress “knees,” or part of the roots that sit above the water line. Though their function is not entirely confirmed, researchers think that the knees help to bring air down to the lower parts of the plant roots. We took a walk across the swamp on a beautiful newly build boardwalk. I also got to collect some edible fruits from the native Pawpaw tree as we strolled along. Despite being completely covered in mud at the end of the day, I was so happy to spend my Saturday outside learning about these very unique ecosystems!
- By Dani Weissman
In early August, Bri and I attended and presented our research at the national Ecological Society of America conference. This was a great opportunity for us to present our research to ecologists throughout the country. From Monday through Friday of the conference, there were talks scheduled throughout the entire conference center. I was amazed by the wide array of topics; there was everything from biogeochemistry to conservation management to population and community dynamics. We used the very handy ESA program app to sort through the talks and find the ones that best fit our interests. Consequently, we also found ourselves running laps through the convention center to try to see everything! I also jumped outside of my familiar realm of soil science and nutrient cycling to attend a symposium on trophic cascades as they relate to the reintroduction of wolves in Yellowstone. It was very fun to explore a different facet of ecology. There were also some very interesting exhibitors at the conference as well. We stopped by the Union of Concerned Scientists table and learned about how science can be better promoted and used to drive policy.
On Tuesday, August 8, I spoke on my work on saltwater intrusion and nutrient cycling in coastal agricultural areas. Later that week, Bri presented her work on cover crops and nitrogen leaching in agricultural systems. On Friday of that week, I moderated a session organized by Kate on sea level rise and ecosystems services. The session was comprised of five very short (<5 minute) talks from different researchers followed by a lengthy discussion period. The speakers gave a lighthearted bend to a very serious topic by dotting their talks with silly limericks and jokes. I think we all may have been a little worn out by the end of the week!
As we were bustling about the convention center, everyone couldn’t help but notice the layer of smog that hung over the city of Portland for the entire week and obscured our view of the beautiful mountains. This was due to smoke traveling south from forest fires raging in nearby British Columbia. I made the immediate connection between the environment outside and the work presented at the conference. Ecological research has such a pressing importance in our daily lives. Climate change and human activities will most certainly alter the range, frequency, and intensity of these fires, as well as many other earth processes. I left the conference with a sense of encouragement—it was wonderful to see so many dedicated researchers working towards an overarching goal.
- By Dani Weissman
As we set out on our last porewater sampling trip of the 2017 summer, I get a bittersweet feeling. I’m happy about all the progress we’ve made on Dani’s saltwater intrusion project, and proud of all I have contributed to the study, but I know I’ll miss spending every other week on Maryland’s beautiful Eastern Shore. Over the summer I have met some awesome people, and I’m grateful that half the time “another day at the office” meant knee-high boots and a machete, but I think I’ll miss the marsh wildlife the most.
Growing up I was always outside looking for snakes, frogs, and bugs, and when I had to be inside I was watching animal planet or reading National Geographic. I left no stone unturned…literally. Instead of growing out of this fascination with life, I only became more interested as I got older, and now I own field guides for just about any critter in North America. The marsh and forests on the shore are rich with animals, and participating in this study was a perfect opportunity to pursue my love for environmental science, and to get up close and personal with the fauna. I must say the mosquitos, deer flies, and chiggers got a little too up-close and personal at times, but it was all worth it. After four water sampling trips and a soil sampling “campaign,” I think we all were starting to feel like marsh wildlife ourselves.
Working with the AgroEcoLab has been an amazing experience, and I look forward to continuing our work into the fall semester, but I will miss the wildlife of the Eastern Shore. In all we’ve rescued four turtles in the middle of the road, hopefully that’s enough good karma to last us until we can get back down there.
- by John Dietrich
I have been working in the Agroecology Lab for almost a year now researching the movement of nitrogen through the soil profile and into cover crops. In this time, I have installed instrumentation in the field, processed data using a combination of R and excel, and collected over a thousand soil and plant samples.
Our instrumentation includes lysimeters and Time-Domain Reflectometers (TDR). Lysimeters are used to collect porewater samples, which we use to quantify nitrate and ammonia concentrations 60 cm down the soil profile. This will give us an idea of how much nitrate-N is leaching out of the system. Our TDR’s are used to measure soil temperature, volumetric water content, bulk relative permittivity, electrical conductivity, and soil pore water electrical conductivity at 0-10 cm, 20-30 cm, and 50-60 cm down the soil profile. The TDR’s were installed for approximately 4 months and collecting data every 10 minutes yielding 252, 870 data points. This forced me to quit using excel all together and familiarize myself with R Studio. Data processing in R Studio has been a wonderful, rewarding experience.
Over 900 soil samples sounds quite intimidating. However, we processed all of our soils shortly after the collection date, so it was quite manageable. Unfortunately, some sources of contamination are entirely unexpected and are left undiscovered until the data processing stage. Four of our sampling dates had unusually high levels of ammonia. Contamination is part of working in a lab and is something we are all very careful about. After a while we discovered the potential source of contamination: our filter papers. I rummaged through my archived soils and began the process all over again. Luckily, with the help of our amazing lab crew: Cullen, John, Gabe, and Tony we were able to complete all 900+ extraction in seven days!
- By Josh Gaimaro
Dr. Kate Tully
Kate is an Assistant Professor of Agroecology at the University of Maryland.
Dani is a PhD student in the AgroEcoLab and studies the effects of sea level rise on coastal farming communities and estuarine biogeochemistry.
Resham is a PhD student in the AgroEcoLab and studies how to improve water and nutrient use efficiency in cover crop systems.