USDA-ARS Long-Term Agroecosystem Research Network (https://www.tucson.ars.ag.gov/ltar)
Dry atmospheric fallout (dryfall) is collected monthly using an Aerochem Metrics wetfall/dryfall collector located at the LTER weather station. Each sample is analyzed for NO3, NH4, Cl, SO4, Ca, Mg, Na, K, Total N, & Total P.
Surface evaporation is measured weekly to twice weekly using an evaporation pan compatible with standard National Weather Service evaporation measurements. Measurements are made twice per week during hot periods because of high evaporation rate. The following data is collected: number of days between measurements, beginning and ending measurement period, current, minimum, and maximum water temperature; initial water level; final water level; rainfall since last evaporation measurement, and calculated evaporation (inches).
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.
This primary purpose of this data set is to validate the LTER Weather Station tipping bucket rain gauge data. The dipstick rain gauge (DSRG) data is measured at least weekly during scheduled maintenance trips to the LTER Weather Station to maintain the evaporation pan water levels. During the summer months this may be twice a week. Additionally, DSRG data is collected after any rain event that requires the collection of the Wetfall/Dryfall precipitation buckets which are located about 10 meters from the DSRG. This is usually any amount greater than 0.02". DSRG data is also collected after very small events when personnel are in the vicinity.
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.
[John Anderson added the following from info provided by Justin Van Zee and edited by Michelle Buonopane.] Overview: In semiarid ecosystems the diversity of plant functional types ( grasses, shrubs, succulents, and so on) and of species may interact with the severe stresses imposed by the desert environment to influence ecosystem processes. Erosion and transport of surface sediment by wind and water is one process that may be affected by the physical structure of the plant community. The Jornada plant diversity experiment, in which the diversity and structure of the plant community have been manipulated in large (25 m x 25 m) plots, offers the opportunity to examine the relative importance of vegetation characteristics and landscape position in determining rates of sediment movement within the plots. Soil erosion is also an important indicator of relative disturbance effects of the treatment manipulations. Each of the 48 plots of the plant diversity experiment contains 5 pans or trays on the downslope side; these accumulate sediments and plant litter that are moving within the plots (carried by wind or by water). Data have been collected on the amount of sediment accumulated in the pans during rainy and during dry seasons, with material sorted and weighed as fine (< 2 mm diameter) or coarse > 2 mm) mineral sediment, plant litter, or rabbit/jackrabbit pellets. Previous statistical analyses found that the mass of material collected per plot is explained only poorly by the treatment (plant community manipulation) of the plot and by block (a rough indication of location on the slope). Objectives: We will test the relative significance of the following variables in explaining plot-level accumulations of sediment and litter: treatment, block, position on slope (the row, from 1 (top of slope) to 10 (bottom), in which the plot is located), the treatment of the plot immediately upslope from the plot, and indices of plant cover and volume (total and by functional group) from the plot-level sampling of vegetation (using fall 1997 data). In addition, we will test the significance of the following variables in explaining the accumulation of sediment and litter in individual pans within a plot: all variables listed above for the plot, plus indices of the vegetative cover and volume located immediately upslope of the pan (weighted for distance from the pan itself).
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.
Sum of dry mass removed for each plant growth form from each plot of biodiversity experiment. Amount of plant material removed in initial establishment of plant diversity treatments was recorded for later use as covariate or measure of disturbance. Material was weighed in the field by species, and species-level data are available from Huenneke; however, this file summarizes plant material removed (dry mass) by growth form (shrub, subshrub, perennial grass, succulent) and by total live dry mass. Also provided are mass of dead material collected from plots (same species as live material removed for each treatment) and total dry mass, live plus dead.
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 Daily Summary data providing daily totals for those dates that precipitation occurred. Values are in millimeters (mm).