A 2-year experiment with ambient, reduced, and enhanced precipitation as well as nitrogen additions was designed to compare the performance of the  encroaching C3 shrub (honey mesquite Prosopis glandulosa) to the dominant C4 grass (black grama Bouteloua eriopoda) in terms of photosynthetic rates and leaf water status. Precipitation manipulations dramatically enhanced natural variability and generated a range of rainfall scenarios that could have only been studied only after a multi-decade effort using natural conditions.We use vegetation cover as a proxy for plant biomass to avoid confounding spatial and temporal variability or confounding the impact of harvesting.  Individual cover of plant species was measured  using three parallel transects per plot. This study is complete.

This ongoing dataset contains monthly precipitation measurements from a network of standard can rain gauges at the Jornada Experimental Range in Dona Ana County, New Mexico, USA. Precipitation physically collects within gauges during the month and is manually measured with a graduated cylinder at the end of each month. This network is maintained by USDA Agicultural Research Service personnel. This dataset includes 39 different locations but only 29 of them are currently sampled. Other precipitation data exist for this area, including event-based tipping bucket data with timestamps, but do not go as far back in time as this dataset.

Monthly summary of precipitation and air temperature data collected daily from standard U.S. climatological service instruments located at USDA Jornada Experimental Range Headquarters.

In 1933 and 1935, two transects were established in the Natural Revegetation Exclosure and Pasture 8b, respectively, to measure long-term soil movement in areas undergoing mesquite invasion. These two transects, established in a Prosopis-Bouteloua ecotone, were to: "measure any future changes in the extent or succession of three contiguous zones of vegetation, Bouteloua eriopoda, Gutierrezia, and Prosopis glandulosa dunes. Thus, future chartings of this transect should show whether, under the range management practiced, the succession is progressing toward the black grama climax or whether it is retrogressing toward mesquite sandhills." (E.L. Little, 1935, unpublished report) Soil movement at these transects was measured by the distance between the soil surface and a notch in 50 cm t-posts located every 15.2 m (50 ft). The 1731-m Natural Revegetation Exclosure tranect runs north-south through the center of the exclosure and extends 61 m (200ft) beyond the boundary fence on either end. It is located in primarily deep, loamy sand soils. The 457-m Pasture 8b transect is oriented WSW-ENE, and is located in shallower soils. These transects were measured in 1950 (8b only), 1955 (8b only), every five years from 1980-2000, and most recently in 2011. Most steel posts were remeasured at these intervals, but some were lost due to excavation or burial. These were for the most part replaced, with a new baseline notch height initiated on the posts. Data fields correspond to each year of collection, as well as measures of soil deposition or deflation during the intervals. Spatial data include post locations and identifiers.

   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
   sub-shrub.

   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
   population dynamics.

   HYPOTHESES:

   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.