Inorganic Nutrient Concentrations in Forested Headwater Streams at Harvard Forest since 2017

For the past 8000 years hemlock has been the foundation species throughout the northeast. The unique functional characteristics of Hemlock have dictated biogeochemical fluxes from terrestrial to aquatic ecosystems (Ellison et al. 2005). Unfortunately, it is currently in an irreversible decline due to the Hemlock Wooly Adelgid and the consequences on riparian ecology are unknown but likely profound (Adams et al. 2012). Red maple, black birch, and northern red oak are some of the most abundant trees in southern New England and are poised to replace hemlock across the landscape (Orwig et al. 2012). Decline and loss of hemlock, and its replacement with hardwood species containing different functional traits are expected to lead to changes in litterfall inputs, forest evapotranspiration, surface water hydrology, including seasonal streamflow/stormflow dynamics, stream temperature, decomposition, and nutrient release (Ellison et al. 2005; Ford and Vose 2007; Guswa and Spence 2011;Brantley et al. 2014). This anticipated shift to hardwoods has far reaching effects as it will significantly alter receiving water primary productivity and food web structure (Humborg et al. 2000, Garnier et al. 2010) by changing watershed N:P:Si export ratios and nutrient availability downstream (e.g., Currie et al. 1996, Fulweiler and Nixon 2005, Carey and Fulweiler 2013). The goal of this ongoing project is to quantify watershed export of inorganic nutrients overtime from the three gauged forested streams at Harvard Forest. To do this we aim to collect samples weekly and then we will calculate monthly, seasonal, and annual changes in inorganic nutrient export. Further we are investigating inorganic nutrient concentration as well as flux vs. stream discharge patterns to better understand the role of physical vs. biological processes in driving watershed nutrient export.