Objectives. Desertification is hypothesized to have altered the spatial and temporal availability of resources required by the biota. Results of desertification on the Jornada include changes to shrub dominated communities and major soil changes. We hypothesize that these shifts in vegetation have changed resources temporally for many of the consumers. If grassland systems respond to rainfall without significant lags, but shrub systems do not, then consumer species should reflect these differences. In addition, shifts from grassland to shrubland results in greater structural heterogeneity of the habitats. We have hypothesized that consumer populations, diversity, and densities of some consumers will be higher in grasslands than in shrublands. Diversity and/or densities are hypothesized to be related to the NPP of the sites.  Data for arthropods captured in pitfall traps on LTER III consumer plots at 2 month intervals. Data includes order, family, genus, species, and number. This data collection has been completed.

Stocking rates for cattle, horses, and sheep are provided for the Jornada Experimental Range beginning in 1916. Goats were few and are included as part of the sheep category and not differentiated.

   OBJECTIVE:  The purpose of the study is to investigate how pulses of precipitation translate into
   pulses of plant above ground 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 (i.e.:  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.

   Variables include rodent species, sex, reproductive status, weight, and maturity status were recorded.

Changes in plant composition have the potential to cause disturbances in both structure and function throughout the ecosystem. One element of the ecosystem that can be affected is bird diversity and behavior. Certain species of birds depend more, or entirely, on habitats containing specific functional groups or species of vegetation. Habitat preferences in birds develop because of factors such as availability of food, nesting and perching locations, and cover.  Certain species of birds may be generalists while others use a small variety of plants due to strict habitat requirements. In this study we examine how different growth types of plants affect bird abundance, bird species diversity, and bird activity on the Jornada Basin. The experiment took place on the Biodiversity plots (25m X 25m)at the New Mexico State University Chihuahuan Desert Rangeland Research Center from June through August 1997. The site contained 6 blocks, each containing 8 treatments, including: control, perennial grass removal, reduced Larrea cover, reduced Prosopis cover, shrub removal, only a single dominant species of each growth form remaining, subshrubs removal, and succulents removal. The following data were recorded in each plot: species type, time spent in plot, type of vegetation utilized, presence of a pair or family group, and behavior. Behaviors recorded included perching, singing, calling, foraging on the ground, foraging in the vegetation, nesting , and preening. Birds were observed in each plot for periods of 35 minutes with a 10 minute acclimation period prior to the start of the observation period. The replications were done according to a predetermined schedule which was developed in such a manner so as to reduce sampling error as much as possible. This study is complete.