Collections of airborne sand are obtained at the 15 NPP sites and the Geomet site. The collections are taken using BSNE collectors. The collectors are turned into the wind with wind vanes. The amount of material collected corresponds to the horizontal flux at the height of the collector and the opening area of the collector and the duration of the sampling time. The five heights of the BSNE collectors above the soil surface are 5, 10, 20, 50, and 100 centimeters for every location where samples are taken. The hypothesis of the experiment is that the vertical flux of the particles smaller than 10 micrometers is a constant ratio of the horizontal sand flux. The objectives of the experiment are to find patterns of sand flux rates as affected by soil and vegetation.
Dataset consists of the annual aboveground net primary production (ANPP) across 3
habitats grouped by plant form and total ANPP. The habitats are grassland, mesquite
shrubland, and the ecotone between the 2. The plant forms are winter annual forb,
annual forb, bi-annual forb, perennial forb, annual grass, perennial grass, shrub, and
OBJECTIVE: The purpose of the study is to investigate how pulses of precipitation
translate into pulses of plant aboveground net primary productivity (NPP) and how the
small mammal community responds to such changes also in relation to shrub gradient
across the landscape. Particularly we are interested in how the energy flows through
the ecosystem in response to pulses of rain, how the small mammal community partition
resources (in terms of C3 (forbs and shrubs) and C4 (grasses) plants) and how the
genetic structure of some species (e.g., Dipodomys spp.) is affected by their
1) Small mammal abundance should respond positively to precipitation and NPP.
2) On a temporal scale, the small mammal energy use should show parallel fluxes along
the shrub gradient.
3) The small mammal community should consume C3 and C4 plants according to their
availability (or NPP).
4) At low population density, dispersal should be limited and the genetic variance will
be distributed among populations rather than within (i.e., Fst will trend towards
higher values). After pulses of rain and NPP, population densities will be greater,
dispersal prevalent, and the genetic variance of populations will be distributed within
populations (i.e., Fst will approach zero) as dispersal homogenizes populations.
Total aboveground annual net primary productivty is calculated for winter annual forb,
annual forb, bi-annual forb, perennial forb, annual grass, perennial grass, shrub,
sub-shrub, and the total of these.
This is the reference harvest biomass data of plants near, but outside the grid of permanent NPP quadrats that was harvested for each of 15 sites. Height and cover are recorded in the field. Live biomass is weighed in the lab and all measurements are recorded as reference harvest data. The NPP sites are grids of permanent 1 square meter quadrats established in 15 sites: three sites in each of 5 community zones (grama grassland, creosotebush scrub, tarbush flats, mesquite dunes and playa). Grids consist of 49 quadrats arranged in a square 7 x 7 pattern, with quadrats 10 m apart (P-COLL has 48 quadrats in a 3 x 16 pattern).
Standing biomass is sampled three times a year: in winter (February - March), before shrubs begin spring growth; in spring (May), when shrubs and spring annuals have reached peak biomass; in fall (late summer; October), when summer annuals have reached peak biomass but before killing frosts. At each sample date, each site is visited (order of sampling may vary, according to phenological stage of sites) and the dimensions of each plant on each quadrat are measured and recorded. Recorded for each observation are: date, zone, plot, quadrat #, species (4 letter acronym), observation # (one for each measurement of that species in that quadrat), cover (percentage of quadrat covered by canopy of that individual or species), height (vertical extent of that individual or species), count (if multiple individuals with the same dimensions are present), and phenological stage (Flowering/fruiting or Vegetative). 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.
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.
Please refer to these publications to evaluate the appropriateness of these data for your intended use prior to contacting Debra Peters, Responsible Investigator, with a data request.