In 2003, the U.S. Fish and Wildlife Service conducted a prescribed burn over a large part of the northeastern corner of the Sevilleta NWR. This study was designed to look at the effect of fire on above-ground net primary productivity (ANPP) within different vegetation types. Net primary production (NPP) is a fundamental ecological variable that measures rates of carbon consumption and fixation. Estimates of NPP are important in understanding energy flow at a community level as well as spatial and temporal responses to a range of ecological processes. While measures of both below- and above-ground biomass are important in estimating total NPP, this study focuses on above-ground net primary production (ANPP). Above-ground net primary production (ANPP) is equal to the change in plant mass, including loss to death and decomposition, over a given period of time. To measure this change, ANPP is sampled twice a year (spring and fall) for all species in each of three vegetation types. In addition, volumetric measurements are obtained from adjacent areas to build regressions correlating biomass and volume.
Three vegetation types were chosen for this study: mixed grass (MG), mixed shrub (MS) and black grama (G). Forty permanent 1m x 1m plots were installed in both burned and unburned sections of each habitat type. The core black grama site included in SEV129 was incorporated into this dataset as an unburned control, so an additional unburned G site was not created. The data for this site is noted as site=G and treatment=C (i.e., control). The original mixed-grass unburned plot caught fire unexpectedly in the fall of 2009 and was subsequently moved to the south.
Volumetric measurements are made using vegetation data from permanent plots collected in SEV156, "Burn Net Primary Productivity (NPP) Study" and regressions correlating biomass and volume constructed using seasonal harvest weights from SEV157, "Net Primary Productivity (NPP) Weight Data."
Derivation of Biomass and NPP:
Data from SEV156 and SEV157 are used used to calculate seasonal and annual production of each species in each quadrat for a given year. Allometric equations derived from harvested samples of each species for each season are applied to the measured cover, height, and count of each species in each quadrat. This provides seasonal biomass for winter, spring, and fall.
Seasonal NPP is derived by subtracting the previous season's biomass from the biomass for the current season. For example, spring NPP is calculated by subtracting the winter weight from the spring weight for each species in a given quadrat. Negative differences are considered to be 0. Likewise, fall production is computed by subtracting spring biomass from fall biomass. Annual biomass is taken as the sum of spring and fall NPP.
August 2009 Burn:
On August 4, 2009, a lightning-initiated fire began on the Sevilleta National Wildlife Refuge. The fire reached the Mixed-Grass Unburned plots on August 5, 2009, consuming them in their entirety. As a result, in the spring of 2010, the Mixed-Grass Unburned plots were moved to a different area within Deep Well, southwest of the Warming site.
Also, on August 4, 2009, some of the webs and quadrats within the unburned Black Grama site were impacted by the fire. Thus, webs 2 and 3 were abandoned and extra plots added to areas within webs 1, 4, and 5 that were not burned. Changes were as follows:
Webs 1, 4, and 5: A plot was added to the northeast to compensate for the loss of all plots at webs 2 and 3.
Web 4: A plot was added to the northwest to compensate for the northern plot, which was burned.
This update supercedes the description of plot layout provided above and is applicable to the Black Grama site only.
Other researchers involved with collecting samples/data: Megan McClun (MAM; 04/2013-present), Stephanie Baker (SRB; 09/2010-present), John Mulhouse (JMM; 08/2010-present), Amaris Swann (ALS; 08/2008-01/2013), Maya Kapoor (MLK; 08/2003-01/2005, 05/2010-03/2011), Terri Koontz (TLK; 02/2000-08/2003, 08/2006-08/2010), Yang Xia (YX; 01/2005-03/2010), Karen Wetherill (KRW; 02/2000-08/2009); Michell Thomey (MLT; 09/2005-08/2008); Seth Munson (SMM; 09/2002-06/2004), Jay McLeod (JRM; 01/2006-08/2006); Caleb Hickman (CRH; 09/2002-11/2004), Charity Hall (CLH; 01/2005-01/2006); Tessa Edelen (MTE, 08/2004-08/2005).