Data set ID:
We use vegetation cover as a proxy for plant biomass to avoid confounding spatial and temporal variability or confounding the impact of harvesting.
The rate of biomass change is Aboveground net primary production, a key variable that will respond to our PPT and nutrient manipulations. Measured variables: individual cover of plant species measured as cm of green biomass that intercepts a 250cm long line, then averaged for 3 lines/plot.
field data sheets and digital voice recorder
We measure vegetation cover in the fall (maximum biomass) in 132 2.5m x 2.5m plots. There are three parallel lines per plot, each of 250 cm length, and 60 cm apart, which beginning and end are marked with rebar. There, we record green interception per species for all plants present in the plot, and use existing regressions to obtain an estimate of biomass by species. ANPP will be calculated as the positive increment of biomass in a plot between dates.
QA/QC: Visual verification of data. Preliminary treatment of data: Calculations performed in Microsoft Excel: Individual cover of plant species measured as cm of green biomass that intercepts 3 250cm long lines, then averaged for 3 lines/plot.
Exclosures 1, 2, and 3 within Pasture 13 (Study Area West) of USDA-ARS Jornada Experimental Range. See attached file "Study278sheltertable.xls" for plot GPS coordinates. The coordinates are UTM Zone13 WGS84.
yearly every fall beginning 2006