LTER

Hourly summary values of averages of readings of the following parameters are made which are based on data recorded on a Campbell CR10(X) data logger: maximum, minimum, and average air temperature; maximum and minimum relative humidity; total precipitation; average wind speed; maximum wind speed; average wind direction; total incoming solar radiation; average soil temperature at 5cm and 20cm; mean dew temperature. From 1983 - 5 June 1991, readings on which hourly averages are based were made at 12 second intervals. From 6 June 1991 to present, readings on which hourly averages are based are made at 10 second intervals.

Arid and semi‐arid ecosystems often exhibit diverse plant growth forms in water‐limited environments, but it is unclear whether resource competition (interference) is actually important in structuring communities. We chose a diverse Chihuahuan desert shrubland to examine the response of the plant community to experimental removals of selected perennial plant species or groups of species. Four treatments involved the removal of all individuals of all species of a single functional group (functional group removals: shrub removal, succulent removal, subshrub removal, perennial grass removal). Three other treatments involved removing species within functional groups. These seven treatments plus a control (no plants removed) were replicated six times each in 25×25 m experimental plots, in summer 1995. Permanent belt transects were surveyed for number and sizes of all vascular plants in spring and fall in 1997, 1999, 2000, and 2001. Those plots from which the dominant shrub, Larrea tridentata, was removed had not recovered in total plant cover or volume by 2001, but cover and volume in all other treatments were similar to those in control plots. Relatively few species demonstrated a positive response to the removal of other species or functional groups. The perennial grass group and forbs were the most responsive; perennial grass cover increased in the shrub removal treatment relative to the control but treatment differences diminished after dry growing seasons in 2000 and 2001. Results over the first five years suggest that either environmental conditions or intrinsic biological characteristics limit the ability of most plant species to respond to the removal of substantial fractions of community biomass and composition in the short term. Such slow response by both dominant and less abundant components of the community has implications for the recovery of semi‐arid systems after human disturbance or other events leading to the reduction of biological diversity. This study is complete.

For more information, see:

Buonopane, M., Huenneke L., and Remmenga, M. 2005. Community reponses to removals of plant functional groups and species from a Chihuahuan Desert shrubland. Oikos 110:67-80.

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.

Pilot study to examine feasibility of measuring individual species response to competing vegetation removal

These data are collected to provide a measurement of rainfall at the Biodiversity site. They are detailed records providing a time stamp of month/day/year hour:minute:second for each tip of the tipping bucket rain gauge (equal to 0.1 mm of precipitation).