Researchers in the Multiple Element Limitation in Northern Hardwood Ecosystems (MELNHE) project are studying N and P acquisition and limitation through a series of nutrient manipulations in northern hardwood forests. This project is supported by the National Science Foundation, and builds upon the Northern Hardwood Forest Calcium Cycling Project, which established our sites at Bartlett. The project is also known as the Shoestring Project, for the long period of unfunded effort prior to renewal funding.
Although temperate forests are generally thought of as N-limited, resource optimization theory predicts that ecosystem productivity should be co-limited by multiple nutrients. These ideas are represented in the Multi-Element Limitation (MEL) model (Rastetter et al. 2012). To test the patterns of resource limitation predicted by MEL, we are conducting nutrient manipulations in three study sites in New Hampshire: Bartlett Experimental Forest, Hubbard Brook Experimental Forest, and Jeffers Brook in the White Mountain National Forest.
At Bartlett, we have three replicate stands of three ages, young (~20 y), mid-aged (30), and mature (>100 years). We have identified stands at Hubbard Brook and Jeffers Brook that corresponds to the mid-aged and mature stands at Bartlett, for 4 more stands. Each of the 13 stands has four 1/4 ha (50 m x 50 m) treatment plots, treated annually beginning in spring 2011, with N (30 kg N/ha/yr as NH4NO3), P (10 kg P/ha/yr as NaH2PO4), N+P, or nothing (an untreated control). Five stands also have a Ca treatment plot (1150 kg Ca/ha in the form of CaSiO3).
We are monitoring stem diameter, leaf area, sap flow, foliar chemistry, leaf litter production and chemistry, foliar nutrient resorption, root biomass and production, mycorrhizal associations, soil respiration, heterotrophic respiration, N and P availability, N mineralization, soil phosphatase activity, soil carbon and nitrogen, nutrient uptake capacity of roots, and mineral weathering. Although it is too early to see a response of forest productivity to the modest rates of N and P application, we have seen synergistic effects of P addition on soil N availability, and foliar resorption of P is highest at high N, which indicates nutrient co-limitation.
MELNHE is led by 6 principal investigators:
Ruth Yanai, SUNY College of Environmental Science and Forestry, Syracuse, NY; Melany Fisk, Miami University of Ohio, Oxford, OH; Tim Fahey and Christy Goodale, Cornell University, Ithaca, NY; Joel Blum, University of Michigan, Ann Arbor, MI, and Ed Rastetter, Marine Biological Laboratory, Woods Hole, MA; with a host of additional collaborators, including graduate students, technicians, undergraduate students, high school teachers and visiting scientists.
MELNHE featured at 2015 Central New York Science & Engineering Fair, Mar 22, 2015. Max Charlamb, a 9th grader at Manlius Pebble Hill School in Dewitt, NY, has been working with Dr. Ruth Yanai, through a Research Assistantship for High School Students supplement to analyze project data. His poster entitled "Is phosphorus more limiting than nitrogen to foliar production in Northern Hardwood Forests" earned High Honors in the Senior Division (grades 9-12). He concluded that data do not support the hypothesis that foliage production would increase with P application more than with N. At the older sites, litter production seemed limited by N availability. The CNYSEF accepts projects from students in grades 4-12 from public, private and independent schools and homeschooled students in Onondaga, Madison, Oswego, Cayuga and Cortland counties. The Fair is one of several annual STEM competitions administered through the Museum of Science and Technology, located in downtown Syracuse's historic Armory Square.
First Sign of Foliar Nutrient Response to Fertilization. Adam Wild provided a project update at the spring Hubbard Brook Committee of Scientists, April 22, 2014. Sugar maple foliage shows the effect of N and P addition at Jeffers Brook. The CaSiO3 addition resulted in higher Si but not higher Ca in foliage at all sites
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