We studied the diversity of arbuscular mycorrhizal fungi (AMF) in a semiarid grassland and the effect of long-term nitrogen (N) fertilization on this fungal community. Root samples of Bouteloua gracilis were collected at the Sevilleta National Wildlife Refuge (New Mexico, USA) from control and N-amended plots that have been fertilized since 1995. Small subunit rDNA was amplified using AMF specific primers NS31 and AM1. The diversity of AMF was low in comparison with other ecosystems, only seven operational taxonomic units (OTU) were found in B. gracilis and all belong to the genus Glomus. The dominant OTU was closely related to the ubiquitous G. intraradices/G. fasciculatum group. N-amended plots showed a reduction in the abundance of the dominant OTU and an increase in AMF diversity. The greater AMF diversity in roots from N-amended plots may have been the result of displacement of the dominant OTU, which facilitated detection of uncommon AMF. The long-term implications of AMF responses to N enrichment for plant carbon allocation and plant community structure remain unclear.
Knowledge Network for Biocomplexity (KNB) Identifier
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Location: Deep Well is located on McKenzie Flats and is site of the longest running SEV LTER met station, number 40, which has been active since 1988. In addition to studies of meteorological variables, core line-intercept vegetation transects and line-intercept transects from the 1995 and 2001 Deep Well fires are sampled here. The mini-rhizotron study, blue and black grama compositional comparison, blue and black grama patch dynamics investigation, and kangaroo rat population assessement are all ongoing here. Deep Well Blue/Black Grama Mixed is also the location of the warming and monsoon experiments, as well as portions of the line-intercept and vegetation removal studies. On August 4, 2009, a lightning-initiated fire began on the Sevilleta National Wildlife Refuge. By August 5, 2009, the fire had reached the area of Deep Well Blue/Black Grama Mixed. While portions of this site were burned, the entirety was not. See individual projects for further information on the effects of the fire.Vegetation: The vegetation of Deep Well Blue/Black Grama Mixed is Chihuahuan Desert Grassland, dominated by black grama (Bouteloua eriopoda) and blue grama (B. gracilis). Other grasses found at the site include dropseeds (Sporobolus spp.) and threeawns (Aristida spp.). Shrubs are uncommon but those that occur include Yucca glauca, Ephedra torreyi, and four-wing saltbush (Atriplex canescens). Herbaceous plants include Plantago purshii, Hymenopappus filifolius, and globe mallows (Sphaeralcea spp.).
Porras-Alfaro, Andrea; Sinsabaugh, Robert; Natvig, Don (2010): Effect of Long-Term Nitrogen Fertilization on Mycorrhizal Fungi Associated with a Dominant Grass in a Chihuahuan Desert Grassland at the Sevilleta National Wildlife Refuge, New Mexico (2005). Long Term Ecological Research Network. http://dx.doi.org/10.6073/pasta/96bdb12750c52056f7c91a14ebd105da