Integrating Soil, Microbial, and Plant Biogeochemical Measurements within the National Ecological Observatory Network (NEON) to Understand Long-Term Ecological Change.

The goal of the NEON Terrestrial Observation System is to conduct co-located measurements of key environmental and organismal taxa at the continental scale in order to understand their responses to changes in climate, land use/land cover, and invasive species.  With respect to ecosystem biogeochemistry, one major objective is to link measurements of the soil, microbial, and plant components in order to discern the storage, transformations, and movement of nutrients and other materials within landscapes.  The proposed NEON approach includes measuring carbon (C) to nitrogen (N) ratios and the stable isotopes of C and N in above- and belowground plant tissues (foliar tissues, coarse and fine roots, woody debris, and litter) and near-surface (i.e., < 0.3 m) soils.  These data will allow researchers to assess whether and where ecosystems are gaining or losing nutrients, and, using the isotopes, create a picture of the integrated ecosystem processes affecting C and N cycling.  Additionally, we are exploring whether measurement of microbial mRNA can be used to link biogeochemical processes with microbial communities.  Our science design approach includes using available historical datasets and a Bayesian statistical model to create a spatially-balanced, stratified random sampling scheme.  This coarse approach will enable researchers to evaluate differences among dominant soil and vegetation types, and can be used to guide further research into biogeochemical dynamics occurring at higher resolutions (e.g., biogeochemical hotspots within landscapes).  Sample locations, extent, and frequency will be determined by the local biogeochemical questions within each domain.  Engaging the soil science community now, as the NEON observatory begins construction, is critical to ensure that high-quality, standardized, and useful data are not only available to, but inspire further research by the diverse range of environmental researchers addressing problems and patterns at the continental scale.