LTER Core Area: Disturbance
Collections of airborne sand are obtained at the 15 NPP sites and the Geomet site. The collections are taken using BSNE collectors. The collectors are turned into the wind with wind vanes. The amount of material collected corresponds to the horizontal flux at the height of the collector and the opening area of the collector and the duration of the sampling time. The five heights of the BSNE collectors above the soil surface are 5, 10, 20, 50, and 100 centimeters for every location where samples are taken. The hypothesis of the experiment is that the vertical flux of the particles smaller than 10 micrometers is a constant ratio of the horizontal sand flux. The objectives of the experiment are to find patterns of sand flux rates as affected by soil and vegetation.
This ongoing data set contains percent canopy cover estimates of perennial plant species from transects that cross a grazed/ungrazed boundary fenceline of a single exclosure on the New Mexico State University Chihuahuan Desert Rangeland Research Center in Dona Ana County, New Mexico, USA. In the spring of 1982, as part of the establishment of the Jornada Long-Term Ecological Research site in southern New Mexico, a 135 ha portion of a 1500 ha, internally drained, watershed was exclosed from grazing by domestic livestock. Prior to exclosure the watershed, as well as the rest of the Jornada basin, had been moderately to heavily grazed for the past 100 years. Concurrent with grazing, the vegetation had undergone a dramatic change from desert grassland, with an almost continuous cover of C4 perennial grasses, to isolated patches of the original grassland in a mosaic with desert shrub dominated plant communities (Buffington and Herbel, 1965). The exclosure lies along a northeast facing piedmont slope at the base of a steep isolated mountain peak, and covers a variety of component landforms from the foot of the mountain to the basin floor. This provided the opportunity to investigate the response of vegetation with respect to landscape characteristics as well as release from grazing. This summary data set consists of percent canopy cover of all perennial plant species from the plant line intercept measurements on either side of the LTER-I exclosure East and West boundary fence. Sampling occurs approximately every five years; it was last conducted in November 2015 and will take place again in 2020.
Boxplots at canopy cover by form: https://jornada.nmsu.edu/sites/jornada.nmsu.edu/files/files/data/Canopy_cover_boxplots_1.jpg
Location on EDI: https://portal.edirepository.org/nis/metadataviewer?packageid=knb-lter-jrn.210120001
t: The goal of this Master’s thesis project, which was carried out in July and August of 2016, was to assess the effect of inferred grazing intensity on 1) vegetation cover type and 2) soil organic carbon (SOC) at the Jornada Experimental Range in southern New Mexico. A sampling transect was established at each of 3 long term cattle water sources (85-106 years old), beginning 5m from the water source and continuing 1500m outward. Soil bulk density, soil organic carbon, soil organic nitrogen, and dominant plant cover type (shrub, grass, and bare soil) were sampled at 20 locations on each transect. Two hypotheses evaluated in this study are: 1) higher grazing pressure near the water source will lead to reduced vegetation cover and C inputs into the soil, leading to higher SOC stocks in soil with far proximity to the water source; and 2) Grazing very close to the water source will exert high disturbance and deposit SOC via defecation, leading to higher SOC stocks in soil with close proximity to the water source.
A figure of the data in this package: https://jornada.nmsu.edu/sites/jornada.nmsu.edu/files/files/data/Cattle_soil_carbon_figure.jpg
Location on EDI: https://portal.edirepository.org/nis/metadataviewer?packageid=knb-lter-jrn.210472001.1
Repeat digital groundbased photos are taken once to twice a year to document plant litter and
soil deposition or removal by wind and water transport on ten microplots located on each of the
8 plots at each of the Aeolian, Dona Ana, and Gravelly Ridges sites. Five photos are taken of
each microplot: One overhead (from directly over the microplot) and 4 lateral views at ground
level of the microplot from each cardinal direction.
Digital filenames are fully descriptive of the site, plot, microplot, photo view, and date taken.
Photo filename structure:
Where 1 = site: A=Aeolian: D=Dona Ana; G=Gravelly Ridges
2 = plot (1-8)
3 = microplot (1-10)
4= photo view (O=overview; E=looking east; N=looking north; S=looking south; W=looking west
5-6-7 = year month day of photo
8 = original image number assigned by camera
There are 3 sites for this study: Gravelly Ridges, Aeolian, and Dona Ana. Within each site,
there are 8 plots. The plots are 8x8 meters and have an 8x8 buffer zone on both sides of the
plot (up and down). There are four BSNE stands for each plot, 2 in each of the 2 buffer zones
(8 collectors per plot). Each stand contains 2 BSNE collectors with the collection opening at
10cm and 30cm height and an opening of 2 cm wide and 5 cm height. These BSNE collectors are in
a fixed position pointing into the direction of the prevailing wind, which corresponds to the
plot alignment. The collectors in the upwind buffer are facing away from the plot and the
collectors in the downwind buffer are facing into the plot. The idea is the upwind BSNEs
measure the amount of dust entering the plot, and the downwind BSNEs measure the amount of dust
moving off the plot. This provides a measure of the effectiveness of the plot obstructions to
wind blown dust. It is important the BSNEs are fixed in an orientation that points across the
full length of the plot.
Material moved from the overland flow of water resulting from precipitation is collected in
belowground containers to get an estimate of that material entering and exiting the plots.
Water and material collected in a container solely from a rain or wind event is not collected.
Bedload oven-dry weight is obtained and the percent Loss on Ignition is calculated.
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.
Mesquite litter mass loss from decomposition associated with soil-litter mixing.
Decomposition models typically under-predict decomposition relative to observed rates in drylands. This discrepancy indicates a significant gap in our mechanistic understanding of carbon and nutrient cycling in these systems. Recent research suggests that certain drivers of decomposition that are often not explicitly incorporated into models (e.g., photodegradation and soil-litter mixing; SLM) may be important in drylands, and their exclusion may, in part, be responsible for model under-predictions. To assess the role of SLM, litterbags were deployed in the Chihuahuan Desert and interrelationships between vegetation structure, SLM, and rates of decomposition were quantified. Vegetation structure was manipulated to simulate losses of grass cover from livestock grazing and shrub encroachment. I hypothesized that reductions in grass cover would promote SLM and accelerate mass loss by improving conditions for microbial decomposition. This study is complete.
For more see: Hewins, D. B., S. R. Archer, G. S. Okin, R. L. McCulley, and H. L. Throop. 2013. Soil-litter mixing accelerates decomposition in a Chihuahuan Desert grassland. Ecosystems 16:183-195
Decomposition models typically under-predict decomposition relative to observed rates in drylands. This discrepancy indicates a significant gap in our mechanistic understanding of carbon and nutrient cycling in these systems. Recent research suggests that certain drivers of decomposition that are often not explicitly incorporated into models (e.g., photodegradation and soil-litter mixing; SLM) may be important in drylands, and their exclusion may, in part, be responsible for model under-predictions. To assess the role of SLM, litterbags were deployed in the Chihuahuan Desert and interrelationships between vegetation structure, SLM, and rates of decomposition were quantified. Vegetation structure was manipulated to simulate losses of grass cover from livestock grazing and shrub encroachment.
We hypothesized that (i) reductions in grass cover would destabilize soils and promote SLM, and (ii) that SLM would enhance microbial abundance and alter microbial community composition in ways that accelerate decomposition. To test our hypotheses, we quantified mass loss, and chemistry of litter incubated on sites with experimental reductions in grass cover (0 to 100% removals) over a 12-month period. This dataset includes data pertaining to the percent carbon, percent nitrogen, and the carbon to nitrogen ratio. This study is complete.
The goal of this sampling effort is to describe the vegetation response to treatments. Data were collected following the line-point intercept method (Herrick et al. 2009). Although the original LPI data set was in multivariate form with separate columns for canopy layers and soil surface, this data set has been transposed into vertical form, implementing a “layer” variable, so that all species and soil surface codes appear in one column. Within each exclosure, 4837 points were sampled with the following exceptions: