Study ID 240

Pinon-Juniper (Core Site) Quadrat Data for the Net Primary Production Study at the Sevilleta National Wildlife Refuge New Mexico (2003-present )

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Realm: Terrestrial
Climate: Temperate
Biome: Deserts and xeric shrublands
Central latitude: 34.350000
Central longitude: -106.880000
Duration: 13 years, from 2003 to 2015

15561 records

167 distinct species

Across the time series Bouteloua gracilis is the most frequently occurring species


Muldavin, E. “Pinon-Juniper (Core Site) Quadrat Data for the Net Primary Production Study at the Sevilleta National Wildlife Refuge, New Mexico (2003-Present).” Sevilleta Long Term Ecological Research Program. Available at:, accessed 2013.


Abstract: This dataset contains pinon-juniper woodland quadrat data and is part of a long-term study at the Sevilleta LTER measuring net primary production (NPP) across four distinct ecosystems: creosote-dominant shrubland (Site C est. winter 1999) black grama-dominant grassland (Site G est. winter 1999) blue grama-dominant grassland (Site B est. winter 2002) and pinon-juniper woodland (Site P est. winter 2003). Net primary production is a fundamental ecological variable that quantifies 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.Above-ground net primary production is the change in plant biomass represented by stems flowers fruit and and foliage over time and incoporates growth as well as loss to death and decomposition. To measure this change the vegetation variables in this dataset including species composition and the cover and height of individuals are sampled twice yearly (spring and fall) at permanent 1m x 1m plots within each site. A third sampling at Site C is performed in the winter. The data from these plots is used to build regressions correlating biomass and volume via weights of select harvested species obtained in SEV157 Net Primary Productivity (NPP) Weight Data. This biomass data is included in SEV182 Seasonal Biomass and Seasonal and Annual NPP for Core Research Sites.Methods: Locating the Sampling Quadrats: Site P the pinon-juniper woodland site (Cerro Montosa) is set-up differently than the other core sites. In order to accommodate the different habitat types groups of transects (i.e. plots) were set up along north (N) and south (S) facing slopes as well as along vegas (V) and ridges (R). Transects on the first two plots consist of 40 quads each (10 quadrants for each of four habitat types). Plot one is slightly west of plot three and plot two is slightly west of the weather station. Plot three is located on a wide piedmont which consists of four transects with five quadrats on each.Collecting the Data: Net primary production data is collected twice each year spring and fall for all sites. The Five Points Creosote Core Site is also sampled in winter. Spring measurements are taken in April or May when shrubs and spring annuals have reached peak biomass. Fall measurements are taken in either September or October when summer annuals have reached peak biomass but prior to killing frosts. Winter measurements are taken in February before the onset of spring growth.Vegetation data is collected on a palm top computer. A 1-m2 PVC-frame is placed over the fiberglass stakes that mark the diagonal corners of each quadrat. When measuring cover it is important to stay centered over the vegetation in the quadrat to prevent errors caused by angle of view (parallax). Each PVC-frame is divided into 100 squares with nylon string. The dimensions of each square are 10cm x 10cm and represent 1 percent of the total area.The cover (area) and height of each individual live (green) vegetative unit that falls within the one square meter quadrat is measured. A vegetative unit consists of an individual size class (as defined by a unique cover and height) of a particular species within a quadrat. Cover is quantified by counting the number of 10cm x 10cm squares filled by each vegetative unit.Niners and plexidecs are additional tools that help accurately determine the cover a vegetative unit. A niner is a small hand-held PVC frame that can be used to measure canopies. Like the larger PVC frame it is divided into 10cm x 10cm squares each square representing 1% of the total cover. However there are only nine squares within the frame hence the name ?niner.? A plexidec can help determine the cover of vegetative units with covers less than 1%. Plexidecs are clear plastic squares that are held above vegetation. Each plexidec represents a cover of 0.5% and has smaller dimensions etched onto the surface that correspond to 0.01% 0.05% 0.1% and 0.25% cover.It is extremely important that cover and height measurements remain consistent over time to ensure that regressions based on this data remain valid. Field crew members should calibrate with each other to ensure that observer bias does not influence data collection.Cover Measurements: Grasses-To determine the cover of a grass clump envision a perimeter around the central mass or densest portion of the plant excluding individual long leaves wispy ends or more open upper regions of the plant. Live foliage is frequently mixed with dead foliage in grass clumps and this must be kept in mind during measurement as our goal is to measure only plant biomass for the current season. In general recently dead foliage is yellow and dead foliage is gray. Within reason try to include only yellow or green portions of the plant in cover measurement while excluding portions of the plant that are gray. This is particularly important for measurements made in the winter when there is little or no green foliage present. In winter sometimes measurements will be based mainly on yellow foliage. Stoloniferous stems of grasses that are not rooted should be ignored. If a stem is rooted it should be recorded as a separate observation from the parent plant.Forbs shrubs and sub-shrubs (non-creosote)-The cover of forbs shrubs and sub-shrubs is measured as the horizontal area of the plant. If the species is an annual it is acceptable to include the inflorescence in this measurement if it increases cover. If the species is a perennial do not include the inflorescence as part of the cover measurement. Measure all foliage that was produced during the current season including any recently dead (yellow) foliage. Avoid measuring gray foliage that died in a previous season.Cacti-For cacti that consist of a series of pads or jointed stems (Opuntia phaecantha Opuntia imbricata) measure the length and width of each pad to the nearest cm instead of cover and height. Cacti that occur as a dense ball/clump of stems (Opuntia leptocaulis) are measured using the same protocol as shrubs. Pincushion or hedgehog cacti (Escobaria vivipara Schlerocactus intertextus Echinocereus fendleri) that occur as single (or clustered) cylindrical stems are measured as a single cover.Yuccas-Make separate observations for the leaves and caudex (thick basal stem). Break the observations into sections of leaves that are approximately the same height and record the cover as the perimeter around this group of leaf blades. The caudex is measured as a single cover. The thick leaves of yuccas make it difficult to make a cover measurement by centering yourself over the caudex of the plant. The cover of the caudex may be estimated by holding a niner next to it or using a tape measure to measure to approximate the area.Height Measurements: Height is recorded as a whole number in centimeters. All heights are vertical heights but they are not necessarily perpendicular to the ground if the ground is sloping.Annual grasses and all forbs-Measure the height from the base of the plant to the top of the inflorescence (if present). Otherwise measure to the top of the green foliage.Perennial grasses-Measure the height from the base of the plant to the top of the live green foliage. Do not include the inflorescence in the height measurement. The presence of live green foliage may be difficult to see in the winter. Check carefully at the base of the plant for the presence of green foliage. If none is found it may be necessary to pull the leaf sheaths off of several plants outside the quadrat. From this you may be able to make some observations about where green foliage is likely to occur.Perennial shrubs and sub-shrubs (non-creosote)-Measure the height from the base of the green foliage to the top of the green foliage ignoring all bare stems. Do not measure to the ground unless the foliage reaches the ground.Plants rooted outside but hanging into a quadrat-Do not measure the height from the ground. Measure only the height of the portion of the plant that is within the quadrat. Creosote Measurements: To measure creosote (i.e. Larrea tridenta) break the observations into two categories:1.) Small individual clusters of foliage on a branch (i.e. branch systems): Measure the horizontal cover of each live (i.e. green) foliage cluster ignoring small open spaces (keeping in mind the 15% guideline stated above). Then measure the vertical height of each cluster from the top of the foliage to a plane created by extending a line horizontally from the bottom of the foliage. Each individual foliage cluster within a bush is considered a separate observation.2.) Stems: Measure the length of each stem from the base to the beginning of live (i.e. green) foliage. Calculate the cumulative total of all stem measurements. This value is entered under height with the species as stem for each quadrat containing creosote. All other variable receive a default entry of 1 for creosote stem measurements.Do not measure dead stems or areas of dead foliage. If in doubt about whether a stem is alive scrape the stem with your fingernail and check for the presence of green cambium.Recording the Data: Excel spreadsheets are used for data entry and file names should begin with the overall study (npp) followed by the date (mm.dd.yy) and the initials of the recorder (.abc). Finally the site abbreviation should be added (i.e. c g b p). The final format for sites B G and C should be as follows: For site P the file format should be File names should be in lowercase. Vegetation data collected in plots in pinon-juniper woodland quadrats at the Sevilleta LTER Unit of abundance = IndCountInt, Unit of biomass = Cover