NPP Study: Quadrat biomass data

These data sets contain calculated aboveground biomass values,
by species, for each quadrat in each site for a given season.
They are constructed (as outlined below) from the field data which
are measurements of the physical dimensions (horizontal cover,
vertical height) of plants or plant parts in the quadrats.
Objective is to monitor patterns (both temporal and spatial) of
aboveground biomass across a range of ecosystem types; to allow
the estimation of net primary production and its variability in
those ecosystems; and to provide a quantitative description of
plant community structure over time in those ecosystems.
Attention: These data are not appropriate for estimates of percentage cover. NPP-associated percent cover measurements were developed for and are used solely to provide the best estimate of biomass production. Becuase the methodology results in measurements of overlapping subcanopy systems and canopies of adjacent individuals, NPP percent cover measurements are not an appropriate measure of actual aerial plant cover. Doing so will result in inflated numbers for the "actual" vegetative cover.
Attention: Data through 2003 was replaced online per below on 9/22/2011. Analyses and results for ANPP differ from previous uses of the data from 1989-1998 (Huenneke et al., 2002) in three ways: (1) Yucca elata was removed prior to analysis because its growth form results in large errors in biomass estimates from year-to-year, (2) regressions between biomass and plant volume used an intercept equal to 0 to be consistent with a recent study in a similar system (Muldavin et al., 2008), and (3) reference harvests obtained in extreme years resulted in adjusted regression coefficents through time that reflect year-to-year variation in ANPP. These changes result in ANPP values that are smaller compared (Peters et al. submitted) with previous studies (Huenneke et al., 2002).