Atmospheric deposition as found in dryfall (dust) and wetfall precipitation has been collected and analyzed since 1983 using an Aerochem Metrics wetfall/dryfall collector located at the Jornada LTER weather station north of Las Cruces, NM, USA. Wetfall occurring as precipitation is collected after each event with a sample size large enough to analyze. Each sample is analyzed for Br, Ca, Cl, F, HPO4, K, Mg, Na, NH4, NO3/NO2, SO4, Total N, and Total P. Analysis of Sr and Dissolved Organic Nitrogen was discontinued in 2003. Dryfall data are available as a separate data package.
This completed dataset, collected in 2001, contains soil particle size analysis (PSA) and sand fractionation data from soil cores collected at 116 quadrat locations that are part of the Jornada Experimental Range's long-term Permanent Quadrats study. The goal of this effort was to help characterize plant-scale factors related to vegetation dynamics observed in the Permanent Quadrats. At each quadrat location, 4 cores were collected at 2 depths (0-5cm and 5-20cm) and assessed for percent sand, silt and clay. The sand fraction, if large enough, was then separated into 5 sand size classes (53-106 micrometers, 106-250 micrometers, 250-500 micrometers, 500-1000 micrometers, 1000-2000 micrometers) to measure the percent fraction of each.
Monthly soil water content measurements are made at 10 depths (where
possible) at each of 10 access tubes at each of the 15 LTER-II NPP
sites using a neutron probe (CPN Model 503DR Hydroprobe). The counts
of thermalized neutrons are adjusted for the decay rate of Americium
241, then converted to soil water content using individual site
regressions. Soil water content is a volume/volume relationship and
represent cm3 water/cm3 soil. Data are provided at 30cm intervals from
30cm to a maximum of 270cm soil depth, shallower when an impenetrable
caliche layer is reached. Field readings may include one at 300cm;
however, the value for the deepest depth of each access tube is removed
from the calculated soil water content data because of the effect of
measuring greater soil volume directly below the probe than that of the
more shallow depths.
This data set is comprised of daily precipitation totals, in inches, measured by Belfort
Instruments weighing rain gauges at 58 locations on the Jornada Experimental Range.
Locations and the dates during which data were collected at them were generally project-oriented.
See comment section (#20) for start and end dates for each location.
Days on which data could not be obtained (due to equipment failure, user error, and/or
other reasons) are flagged as missing within this dataset. As of 31 December 2008 they
comprised 1,270 of the total 291,465 records, which is less than 0.44% of the data set.
A 2-year experiment with ambient, reduced, and enhanced precipitation 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. Responses were highly asymmetric, with precipitation (PPT) additions generally influencing volumetric water content (vwc) to a greater extent than PPT reductions. Desert soils are usually close to their minimum water content and thus when soils were dry, the effects of reducing PPT were relatively minor compared to the effects of adding PPT. Volumetric soil water content was, on average, lower and more variable at the shallower (0–5 cm) depth (mean 9.3 ± 0.14%; range 5.7–14.3%) than at the deeper (30–50 cm) depth (mean 14.4 ± 0.12%; range 10.8–18.1%. This study is complete. For further information and results, see:
Throop, H., L. G. Reichmann, Os. Sala, and S. Archer. 2012. Response of dominant grass and shrub species to water manipulation: an ecophysical basis for shrub invasion in a Chihuahuan desert grassland. Oecologia 169: 373-383.
Wet atmospheric fallout (wetfall occurring as precipitation) 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.
Increases in woody vegetation and declines in grasses in arid and semi-arid ecosystems have occurred globally since the 1800s, but the mechanisms driving this major land-cover change remain uncertain and controversial. Working in a shrub-encroached grassland in the northern Chihuahuan Desert where grasses and shrubs typically differ in leaf-level nitrogen allocation, photosynthetic pathway, and root distribution, we asked if differences in leaf level ecophysiology could help explain shrub proliferation. We predicted that the relative performance of grasses and shrubs would vary with soil moisture due to the different morphological and physiological characteristics of the two life-forms. In a 2-year experiment with ambient, reduced,and enhanced precipitation during the monsoon season, respectively, the encroaching C3 shrub (honey mesquite Prosopis glandulosa) consistently and substantially outperformed the historically dominant C4 grass (black grama Bouteloua eriopoda) in terms of photosynthetic rates while also maintaining a more favorable leaf water status. This data set includes leaf water potential for each leaf measured while data on photosynthetic rates can be found in package 210409001. This study is complete. Please refer to: Throop, H., Archer, S. R. , and L. G. Reichmann. 2011. Response of dominant grass and shrub species to water manipulation: an ecophysiological basis for shrub invasion in a Chihuahuan Desert Grassland. Oecologia 169: 373-383.
Increases in woody vegetation and declines in grasses in arid and semi-arid ecosystems have occurred globally since the 1800s, but the mechanisms driving this major land-cover change remain uncertain and controversial. Working in a shrub-encroached grassland in the northern Chihuahuan Desert where grasses and shrubs typically differ in leaf-level nitrogen allocation, photosynthetic pathway, and root distribution, we asked if differences in leaf level ecophysiology could help explain shrub proliferation. We predicted that the relative performance of grasses and shrubs would vary with soil moisture due to the different morphological and physiological characteristics of the two life-forms. In a 2-year experiment with ambient, reduced,and enhanced precipitation during the monsoon season, respectively, the encroaching C3 shrub (honey mesquite Prosopis glandulosa) consistently and substantially outperformed the historically dominant C4 grass (black grama Bouteloua eriopoda) in terms of photosynthetic rates while also maintaining a more favorable leaf water status. This study is complete.
Please refer to:
Throop, H., Archer, S. R. , and L. G. Reichmann. 2011. Response of dominant grass and shrub species to water manipulation: an ecophysiological basis for shrub invasion in a Chihuahuan Desert Grassland. Oecologia 169: 373-383.
This data set was collected to provide data for comparison of the losses of dissolved nitrogen and phosphorus in the runoff from grass- and shrub- dominated plots in the Jornada Basin of southern New Mexico. This summary dataset contains the following columns for the shrub plots: Plot: the identification number for the 6 grassland plots. Q: the mean rate of discharge during the entire experiment, obtained by dividing the total runoff by l800 sec. The units are cubic centimeters per second. Total N yield: the total yield of dissolved nitrogen discharged from the plot during the duration of the experiment. The units are grams per square meter per l800 sec. This yield has been adjusted, by subtracting the content of total dissolved N applied in the simulated rainfall. Organic N yield: the yield of dissolved organic N, as above. Inorganic N yield: the yield of NH4-N plus NO3-N discharged from the plot during the duration of the experiment, as above. Total P yield: the yield of total dissolved P discharged from the plot during the duration of the experiment. The units are grams per square meter, per l800 sec. Organic P yield: the yield of dissolved organic P, as above. Inorganic P yield: the yield of PO4-P discharged from the plot during the duration of the experiment. Fines: the percent of the plot surface covered by materials < 2.0 mm diameter Gravel: the percent of the plot surface covered by materials > 2.0 mm diameter Vegetation: the percent of the plot surface covered by vegetation. Litter: the percent of the plot surface covered by plant litter. Slope: it was not possible to measure slope in plots with a shrub in them, since the mound dominated the slope in the plot.
