Long-term Experimental Networks for Stream Ecosystem Studies: the Lotic Intersite Nitrogen Experiment (LINX) and the Stream Experimental and Observatory Network (STREON) Component of the National Ecological Observatory Network
Abstract
LINX and STREON represent large experimental networks to understand the dynamics of stream ecosystems. These inter-site coordinated experiments represent a shift towards research whose goal is to understand how the drivers of ecosystem structure and function change across major continental-scale environmental gradients. LINX consisted of two consecutive, inter-site studies involving 15N-tracer additions to streams to determine rates and mechanisms of nitrogen cycling at the scale of entire stream reaches. The LINX studies, which lasted for a decade, were the first to use the 15N addition approach to determine gross rates of ammonium and nitrate uptake, nitrification, and denitrification under ambient conditions in stream ecosystems across several biomes and many types of land use. The LINX studies documented the important roles of stream hydrology (flow and transient storage zones), chemistry (N concentrations), and biology (in- stream gross primary production and respiration rates) in controlling N uptake and retention. Stream network models based on field results showed that streams are important sites for N retention in the landscape. Although LINX demonstrated the importance of experiments conducted across stream networks, these studies were limited in duration and could not address questions dealing with long-term impacts. STREON, the stream component of the planned National Ecological Observatory Network (NEON), is intended to use long-term observations and experimental nutrient and consumer organism manipulations to understand controls and forecast changes in stream ecosystems. The observations, to be conducted in a network of more than 20 streams across the U.S. and Puerto Rico over 30 years, will involving state-of-the- art in situ sensors and data communication devices as well as periodic sampling and analyses to determine hydrologic, geomorphologic, biogeochemical, and biological properties and processes. The experiments, to be conducted at about 10 sites over at least 10 years, will involve N and P additions and secondary consumer exclosures to provide a better understanding of how eutrophication and consumer extinction and extirpation, two of the most pervasive forms of environmental change, interact to affect stream ecosystems. Together, the STEON observational and experimental studies will provide critical information on effects of such stresses as climate change, land use change, invasive species, and N deposition on stream ecosystems.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.H12A..01M
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling (0412;
- 0793;
- 1615;
- 4805;
- 4912);
- 0470 Nutrients and nutrient cycling (4845;
- 4850);
- 1804 Catchment;
- 1848 Monitoring networks;
- 1871 Surface water quality