This long-term study examines how nitrogen fertilization affects plant species and soil microbial communities at the ecotone of Plains and Chihuahuan Desert grassland. The project at the Sevilleta LTER began in spring 1995 with funding from an NSF special competition for cross-site research. LTER funds now maintain treatments and data collection.


This is one of the longest running dryland nitrogen fertilization experiments, contributing to our general understanding of the effects of terrestrial eutrophication, and providing an important dryland representative for cross-site studies of N limitation in grasslands and other plant communities. Over the long-term, we can evaluate the potential for interactions between eutrophication and increases in both aridity and interannual precipitation variability because fertilization treatments occur over a highly variable and drying background climate. For example, nitrogen addition may alleviate a saturating relationship between plant biomass and precipitation and reduce the sensitivity of biomass to variability in climate.


Fertilizer is applied yearly prior to the summer monsoon rainy season as granular NH4NO3 at the rate of 100 kg N ha-1 yr-1. The twenty 10 m X 5 m plots include 10 fertilized and 10 control plots. This site was burned in a management fire in June 2003. A management fire in September 2019 burned around, but not in, this experiment.


Plant species composition and the cover and height of individuals to estimate biomass, were sampled twice yearly (spring and fall) within four permanent 1 m x 1 m quadrats until 2019, and afterwards two quadrats per plot. Belowground plant biomass (NPP) is measured in root in-growth donuts annually.

Supporting Documents:

Nitrogen Fertilization Experiment (NFert): Seasonal Biomass and Seasonal and Annual NPP Data at the Sevilleta National Wildlife Refuge, New Mexico. https://portal.edirepository.org/nis/mapbrowse?scope=knb-lter-sev&identifier=186

Related Publications:

Zeglin, L.H., M. Stursova, R.L. Sinsabaugh & S.L. Collins. 2007. Microbial responses to nitrogen addition in three contrasting grassland ecosystems. Oecologia 154:349-359. https://doi.org/10.1007/s00442-007-0836-6

Stursova, M., C.L. Crenshaw & R.L. Sinsabaugh. 2006. Microbial responses to long-term N deposition in a semi-arid grassland. Microbial Ecology 51:90-98. https://doi.org/10.1007/s00248-005-5156-y

Ladwig, L.M., S.L. Collins, A.L. Swann, Y. Xia, M.F. Allen and E.B. Allen. 2012. Above- and belowground responses to nitrogen addition in a Chihuahuan Desert grassland. Oecologia 169: 177-185. https://doi.org/10.1007/s00442-011-2173-z

Porras-Alfaro, A., J. Herrera, R.L. Sinsabaugh, K.J. Odenbauch, T. Lowrey & D.O. Natvig. 2008. Novel root fungal consortium associated with a dominant desert grass. Applied and Environmental Microbiology 74:2805-2813. https://doi.org/10.1128/AEM.02769-07

Porras-Alfaro, A., J. Herrera, D. O. Natvig, and R. L. Sinsabaugh. 2007. Effect of long-term nitrogen fertilization on mycorrhizal fungi associated with a dominant grass in a semiarid grassland. Plant and Soil 296:65–75. https://doi.org/10.1007/s11104-007-9290-9