The overall goal of the rainfall manipulation project is to understand the coupled ecological and hydrological responses of a grassland, shrubland and a mixed grass-shrub vegetation community to extended periods of increased or decreased rainfall. Rainfall manipulation plots have been established in each of these three vegetation communities in the Five Points area of Sevilleta National Wildlife Refuge. In each vegetation community, three control plots, three drought treatment plots, and three water addition plots have been installed, each approximately 10 x 15 m in size. In each plot, vertical profiles of soil moisture probes have been installed under each cover type (canopy and interspace in grassland and shrubland; grass canopy, shrub canopy and interspace at the ecotone (mixed grass-shrub) site). The probes measure differences in infiltration and soil water content and potential associations with these different cover types. In addition, TDR probes have been installed diagonally in each cover type to integrate the water content of the top 15 cm of soil. Each plot contains 18, 1m2 quads made up of 6, 1m2 quads along each of the 3 transects located across each plot. Each spring and fall, the following parameters are measured in every quad: live plant cover, height, and abundance by species; dead plant cover; soil cover; litter cover; and rock cover. Data collection began in the drought and control plots in the spring of 2002. Data collection began in the water addition plots in the spring of 2004.In the grassland and shrubland communities, all nine currently established plots are located together. The three drought plots were located under a single large roof with a 0.5 m path separating each plot (drought treatments ended in 2006). The control plots and water addition plots are similarly grouped, but without the shelter structure. In the ecotone community, the plots are in three groups; each group is comprised of one drought plot, one water addition plot, and one control plot. Control plots received no experimental treatment, while the sliding roofs over the drought plots were used to divert precipitation, producing a long-term drought. The roofs covering the drought plots were lowered when there was no precipitation so that the amount of sunlight received by the drought plots was minimally affected. Water addition was intended to impose a complementary increase in water supply on the water addition plots.
One meter2 vegetation quadrats are used to measure the cover and abundance of all plants present along each of the three transects across each plot. These quadrats are also used to measure dead plant foliage, leaf litter, bare soil, and rock covers. One person works on each quad, recording the data into a palm top computer. Two technicians may work independently along the same transect and alternate quadrats.
To begin quadrat measurements, first locate the three pairs of rebar along the length (across the slope, perpendicular to the gutter edge) of each plot, which mark the endpoints of each transect. Once the transect has been located, run a string across the plot attaching it to the two transect endpoint rebar stakes to act as a guideline for measurements. Each transect is measured from the left to the right side of the plot (where left and right are from the perspective of a person standing at the bottom edge of the plot where the gutters are located).
Beginning at the left side of the transect, place the bottom edge of the quadrat along the guidline of the string with the quad pointing away from the gutter edge. After measuring the quadrat, advance the quadrat along the transect by moving the quadrat to the right so that the bottom left corner is moved to the position formerly occupied by the bottom right corner. Repeat this process until the entire width of the transect has been measured. *Note: Beginning in the spring of 2010 only quadrats 2-7 (or meters 2-7) were measured. Before the spring of 2010 there were a variable number of quadrats measured per transect. If the last quadrat did not lie completely within the boundaries of the plot (within the metal edging), the percentage of the plot that lied within the plot boundary was recorded in the comments column of the data sheet and the vegetation data was recorded in the same manner as for the other quadrats. If the last quadrat lied completely within the boundaries of the plot, 100% was recorded in the comments section of the data sheet. This was to ensure that the entire transect had been measured.
General vegetation measurements
The cover, height, and abundance (standing biomass) are recorded for each species of plant inside the quadrat. Vegetation measurements are taken in two layers: a ground level layer that includes all grasses, forbs, sub-shrubs, the bases of Larrea tridentata and bare soil and a “shrub” layer that includes the canopy of Larrea tridentata. The purpose of this approach is to include Larrea canopies, while allowing the cover values of the ground level layer to sum to approximately 100%.
The quadrat boundaries are delineated by the 1 m2 PVC-frame placed above the quadrat. Each PVC-frame is divided into 100 squares with nylon string. The dimensions of each square are 10cm x 10cm and represent 1 % of the total quadrat area or cover. The cover and height of all individual plants of a species that fall within the 1m2 quadrat are measured. Cover is quantified by counting the number of 10cm x 10cm squares intercepted by all individual plants of a particular species, and/or partial cover for individual plants < 1%.
When reading plant cover it is important to stay centered over the vegetation in the quadrat. If you are not directly centered over the vegetation, cover measurements can be over or underestimated by your angle of view (parallax). If the surrounding plants prohibit you from leaning directly over the plants, use a tape measure to delineate a vertical column of intercept. To do this, simply extend the tape measure vertically from the base of the plant up to the frame grid.
Vegetation cover measurements
Cover measurements are made by summing the cover values for all individual plants of a given species that fall within an infinite vertical column that is defined by the inside edge of the PVC-frame. This includes vegetation that is rooted outside of the frame but has foliage that extends into the vertical column defined by the PVC-frame. Again, cover is quantified by counting the number of 10cm x 10cm squares intercepted by each species. Do not duplicate overlapping canopies, just record the total canopy cover on a horizontal plane when looking down on the quadrat through the grid.
Larger cover values will vary but the smallest cover value recorded should never be below 0.1%. When dealing with individual plants that are < 1.00%, round the measurements to an increment of 0.1. Cover values between 1.00 - 5.00% should be rounded to an increment of 0.5 and values > 5.00% are rounded to an increment of 5.
Cover measurements should be calculated separately for living and dead individuals of each species. However, because these measurements are made infrequently, vegetation should be considered live if it represents the current year’s growth (green and yellow). This is particularly important for grasses that may have become senescent during the fall sampling of each year.
Two Larrea tridentata coverage measurements are taken (LATR2 for canopy and LATR2B for the basal cover). The canopy level layer is estimated using the portion of the canopy that falls within the quadrat. The canopy edge is defined by a straight gravity line from the canopy to the ground (i.e. imagine a piece of string with a weight on the end being moved around the canopy edge). A basal cover is taken at the base of the shrub and includes all woody vegetation that stems from the ground. The purpose of taking two measurements for Larrea is to assess changes in shrub canopy cover without confounding the percent cover estimates of other species obtained using the basal layer. For Larrea seedlings the code LSEED is used and is a separate measurement from the Larrea canopy and basal measurements.
To determine the cover of a grass clump, envision a perimeter around the central mass or densest portion of the plant excluding individual long leaves, wispy ends or more open upper regions of the plant. Live tissue is frequently mixed with dead tissue in grass clumps. Provide two sets of measurements for the dead and live foliage, if possible, especially for perennial grass species. In the case that both live and dead are difficult to separate, measure all of the foliage as live. Remember that vegetation should be considered live if it represents the current year’s growth. In general, recently dead foliage is yellow and long-dead foliage is gray.
The cover of forbs is the perimeter around the densest portion of the plant. Measure all foliage that was produced during the current season including any recently dead (yellow) foliage.
Cacti and Yucca:
The cover of cacti and yucca is made by estimating a perimeter around the densest portion of the plant and recorded as a single cover. For cacti that consist of a cluster of pads or jointed stems (i.e., Opuntia phaecantha, Opuntia imbricata), estimate an average perimeter around the series of plant parts and record a single coverage measurement.
Vine cover (and some forbs) is often convoluted. Rather than attempt to estimate cover directly, take a frequency count of 10X10X10cm cubes that the vine is present in.
As with other vegetation measurements, the smallest cover value for seedlings should never be <0.1. If the value of seedling cover is less than 0.1, round up to 0.1. In the comments write “SEEDLING.”
Height is measured with a tape measure as a whole number in centimeters. All heights are vertical heights that are defined as a line parallel to the pull of gravity; this is not necessarily perpendicular to the ground if the ground is sloping. Measure the maximum height of each species identified in the quadrat. Do not measure the heights of every individual plant for a particular species.
The height of Larrea is only taken only at the canopy level (LATR2). Measure the maximum height from the base of the woody vegetation that stems from the ground to the top of the green foliage. No height measurement is needed at the basal level (LATR2B).
Annual grasses and all forbs:
Measure the height from the base of the plant to the tallest part of foliage for that species in the quadrat. Include the height of the inflorescence, if present.
Measure the height from the base of the plant to the tallest part of green foliage for that species in the quadrat. Do not include the inflorescence in the height measurement..
Plants rooted outside but hanging into the quadrat:
Do not measure the height from the ground. Measure only the height of the portion of the plant that is within the quadrat. In the comments section of the data sheet, record “Hang Over.” or “HO”.
Abundance is recorded as the number of individual plants that comprise the cover measurement. For some species, individuals are hard to distinguish. If there is bare space between two units, they should be considered separate individuals.
At the basal level (LATR2B) count the number of Larrea bases present in the quadrat.
Dead plant foliage:
For plants that are dead, but still attached to the soil and standing, just record the cover. Do not measure height or abundance for dead plants. Instead, record “-888” in these spaces on the spreadsheet to signify a value that was intentionally not recorded and enter DEAD in the comments. Cover is quantified by counting the number of 10cm x 10cm squares intercepted by each species. As with live vegetation, plant measurements that are < 1.00% should be rounded to an increment of 0.1. Cover values between 1.00 - 5.00% should be rounded to an increment of 0.5 and values > 5.00% are rounded to an increment of 5.
Remember, if some of the individuals of a plant species, or if portions of the foliage of an individual plant on the quadrat are dead and some alive, provide two sets of measurements for the dead and living foliage. In the case that both live and dead foliage are intermixed and difficult to separate, as in some bunch grasses and shrubs, just record the foliage as live. Any dead plant foliage that is not still attached to the roots and standing is considered leaf litter.
Materials other than vegetation that are measured in the drought plots include leaf litter, soil, rocks, and buckets (see below). Other than buckets, which occur in very few plots, values should always be recorded for these materials. If they are not present in a given quad, put ”-888” for their cover values so that it is clear that these categories were not simply overlooked during data collection.
Heights and abundances are not recorded for any of these materials. Instead, record “-888” for height and abundance and a numerical value for cover, where applicable (see below). If not recorded in the field, the data manager will do so during the QA/QC process.
Leaf litter includes all detached dead plant material on the soil surface, including woody branches. Cover is quantified by summing the number of 10cm x 10cm squares intercepted by patches of leaf litter. Cover values < 5.00% should be rounded to increments of 1 and cover values > 5.00% should be recorded in increments of 5. If there is no leaf litter in the quadrat, record “LITT” in the “species “ column and record “-888” in the cover, height, and abundance columns.
Some leaf litter cover has distinctive margins and is easy to define and measure. However, leaf litter may occur in diffuse small patches that are separated by bare soil, and distributed throughout the quadrat. For such diffuse cover, determine the actual cover in one typical 10 by 10 cm square (e.g., 0.3), then count the number of squares with diffuse cover (e.g., 5), and multiply the number of squares by the actual cover for a typical square (e.g., 0.3 X 5 = 1.5, then round to 1.0 or 2.0, or if the value had been greater than 5, round to the nearest increment of 5.0) for the total leaf litter cover. All leaf litter measurements are pooled into one observation, and no height or abundance is measured. Only measure leaf litter that is in the open, do not attempt to measure within clumps of grass, etc.
Measure the cover of the area occupied by abiotic substrates. Cover is quantified by summing the number of 10cm x 10cm squares intercepted by abiotic substrates. As with leaf litter, cover values < 5.00% should be rounded to increments of 1 and cover values > 5.00% should be recorded in increments of 5. If there is no soil in the quadrat, record “SOIL” in the species column for that quadrat and record a “-888” for the height, cover, and abundance. Again, when soil is present, only the cover is recorded and “-888” should be entered for height and count.
As a separate entry, estimate the cover of rock (particles >1 cm) occurring within the bare ground. The rock cover estimate can be viewed as an index of how much of the soil surface is rocky or as a subset of the soil cover measurement. The rock cover should still be measured as a sum of the number of 10cm x 10cm squares intercepted by rock. Cover values < 5.00% should be rounded to increments of 1 and cover values > 5.00% should be recorded in increments of 5. Enter “-888” for the height and count. If there is no rock cover in the quadrat, record “ROCK” in the species column and enter “-888” for the height, count, and cover.
For Grass and for Creosote sites treatments are: Plots 1-4 Drought; plots 5-6 Control; Plots 7-9 Watered; For Mixed site treatments are: Plots 3,6,9 Drought; Plots 2,4,8 Control; Plots 1,5,7 Watered.
File created 3/2/2005. -- Kristin VanderbiltUpdated 12/11/2006 --Karen Wetherill Data appended to file on 7/25/2005 -- KLV Data compiled into one file. Metadata entered in EML access database. TK 6 February 2009 data qa/qc in navicat. Made NONE measurements in the following format Cover 0 Height -888 Count -888. Corrected typos and errors. TLK 10 February 2009
On Aug 4, 2009, a lightning strike ignited a fire in the area west of the road from Black Butte to Five-Points. The fire started around 3:30 PM on the 4th. The fire was initially concentrated in the Grassland Drought, SMES, and Monsoon study areas. The next day the fire carried north and east to the Deep Well Meteorological station, Warming, and Nut-Net plot areas. The fire was finally contained by the end of the 5th covering >7800 ha.
Starting in the spring of 2011, only the mixed shrub site will be measured in the spring and in the fall only the mixed shrub and creosote sites will be measured. Measurements at the drought grassland site was discontinued at this time.
Sevilleta Field Crew Employee History
Megan McClung, April 2013-present, Stephanie Baker, October 2010-Present, John Mulhouse, August 2009-Present, Amaris Swann, August 25, 2008-January 2013, Maya Kapoor, August 9, 2003-January 21, 2005 and April 2010-March 2011, Terri Koontz, February 2000-August 2003 and August 2006-August 2010, Yang Xia, January 31, 2005-April 2009, Karen Wetherill, February 7, 2000-August 2009, Michell Thomey, September 3, 2005-August 2008, Jay McLeod, January 2006-August 2006, Charity Hall, January 31, 2005-January 3, 2006, Tessa Edelen, August 15, 2004-August 15, 2005, Seth Munson, September 9, 2002-June 2004, Caleb Hickman, September 9, 2002-November 15, 2004, Heather Simpson, August 2000-August 2002, Chris Roberts, September 2001-August 2002, Mike Friggens, 1999-September 2001, Shana Penington, February 2000-August 2000.
See all Sevilleta Publications