Study ID 239

Pinon Juniper Net Primary Production Quadrat Data from the Sevilleta National Wildlife Refuge New Mexico 1999-2001

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Realm: Terrestrial
Climate: Temperate
Biome: Deserts and xeric shrublands
Central latitude: 34.350000
Central longitude: -106.880000
Duration: 3 years, from 1999 to 2001

5288 records

123 distinct species

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


Muldavin, E. “Pinon Juniper Net Primary Production Quadrat Data from the Sevilleta National Wildlife Refuge, New Mexico: 1999-2001.” Sevilleta Long Term Ecological Research Program. Available at:, accessed 2013.


Collecting the Data:Vegetation data is collected on a palm top computer. 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 should be as follows: File names should be in lowercase.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-The cover of forbs is measured as the perimeter of the densest portion of the plant. If the forb is an annual it is acceptable to include the inflorescence in this measurement. If the forb 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 shrub and sub-shrubs-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.Foliage canopy cover:Cover and height are recorded for all separate vegetative units that fall within an infinite vertical column that is defined by the inside edge of the PVC-frame. A vegetative unit consists of an individual species with a unique cover and height. This includes vegetation that is rooted outside of the frame but has foliage that extends into the vertical column defined by the PVC-frame.As mentioned above cover is quantified by counting the number or fraction of 10 cm x 10 cm squares intercepted by each vegetative unit. It is possible to obtain a total percent cover greater than 100 for a quadrat because vegetative units often overlap (especially in shrubs and succulents). For perennial plants cover is based only on the vegetative portion of the plant (stem and leaf). For annual plants cover is based on both vegetative and reproductive (inflorescence) portions of the plant.If the cover of a vegetative unit is less than 1 the increments used are as follows: 0.01 0.05 0.1 0.25 0.5 and 0.75. If cover is between 1 and 5 increments of 0.5 are used and if greater than 5 increments of 1 are used. Finally if the cover is greater than 15 the total canopy cover is divided into smaller units and the cover and heights of each observation measured separately. This reduces the size of harvest samples. Vegetation data collected in two distinct ecosystems: pinon/juniper woodland (P) and juniper savannah woodland (J) Unit of abundance = IndCountInt, Unit of biomass = Cover