Annual mean estimates of aboveground net primary production (NPP) at 15 sites at Jornada Basin LTER, 1989-ongoing

This package contains values of mean annual aboveground net primary production (NPP, in grams per square meter per year) at 15 NPP study sites on Jornada Experimental Range (JER) and Chihuahuan Desert Rangeland Research Center (CDRRC) lands. Sites were selected to represent the 5 major ecosystem types in the Chihuahuan Desert (upland grasslands, playa grasslands, mesquite-dominated shrublands, creosotebush-dominated shrublands, tarbush-dominated shrublands). For each ecosystem type, three sites were selected to represent the range in variability in production and plant diversity; thus the locations are not replicates. At each site, a 1 hectare area was fenced in 1988 and a grid of 49 (48 at one playa location) 1m x 1m replicate quadrats was laid out when sampling began in 1989. In fall, winter, and spring periods aboveground biomass was calculated for each species and quadrat at each NPP site. These calculations rely on two data sources: 1) non-destructive horizontal cover and vertical height measurements of individual plants, or plant parts, within each quadrat, and 2) linear regression coefficients for each plant species derived from off-quadrat cover, height, and harvested biomass measurements. NPP is then calculated as the positive biomass increment between seasons. The annual totals in this dataset are derived by summing mean site NPP values for winter (October - February), spring (February - May), and fall (May - October) increments for a single calendar year. Data collection is ongoing with new annual NPP values calculated after the conclusion of each growing season. Attention: 1) Calculated values in this data package have changed over time as the methodology for estimating biomass has changed. 2) Relating long-term NPP in this package with long-term precipitation is problematic given the importance of wet and dry periods and their effect on production in these ecosystems. 3) Data from 2013 and later are currently in provisional status and subject to change as we review the allometric equations used for estimating biomass. See Notes in the methods element for further details.