ecology

Monsoon Rainfall Manipulation Experiment (MRME): Soil Nitrogen Data from the Sevilleta National Wildlife Refuge, New Mexico (2007 - present)

Abstract: 

The Monsoon Rainfall Manipulation Experiment (MRME) is designed to understand changes in ecosystem structure and function of a semiarid grassland caused by increased precipitation variability, by altering rainfall pulses, and thus soil moisture, that drive primary productivity, community composition, and ecosystem functioning. The overarching hypothesis being tested is that changes in event size and frequency will alter grassland productivity, ecosystem processes, and plant community dynamics. Treatments include (1) a monthly addition of 20 mm of rain in addition to ambient, and a weekly addition of 5 mm of rain in addition to ambient during the months of July, August and September. We predict that soil N availability with interact with rainfall event size to alter net primary productivity during the summer monsoon. Specifically, productivity will be higher on fertilized relative to control plots, and productivity will be highest on N addition plots in treatments with a small number of large events because these events infiltrate deeper and soil moisture is available longer following large compared to small events.

Data set ID: 

309

Core Areas: 

Keywords: 

Data sources: 

sev309_MRMEsoilnitrogendata_20160727.csv

Methods: 

Experimental Design

MRME contains three ambient precipitation plots and five replicates of the following treatments:
1) ambient plus a weekly addition of 5 mm rainfall, 2) ambient plus a monthly addition of 20 mm rainfall.

Rainfall is added during the monsoon season (July-Sept) by an overhead (7 m) system fitted with sprinkler heads that deliver rainfall quality droplets. At the end of the summer, each treatment has received the same total amount of added precipitation, delivered in different sized events.

Each plot (9x14 m) includes subplots (2x2 m) that receive 50 kg N ha-1 y-1. Each year we measure: (1) seasonal (July, August, September, and October) soil N, (2) plant species composition and ANPP, (3) annual belowground production in permanently located root ingrowth cores, and (4) soil temperature, moisture and CO2 fluxes (using in situ solid state CO2 sensors).

Soil Measurements: We use plant root simulator probes (PRS® Probes, Western Ag Innovations, Saskatoon, Saskatchewan, Canada https://www.westernag.ca/innov).

Instrumentation: Plant root simulator probes

On August 4th, 2009, lightning ignited a ~3300 ha wildfire that burned through the entire experiment and its surroundings allowing us to assess experimentally the effects of interactions among rainfall pulse dynamics and wildfire on post-fire grassland dynamics and ecosystem processes.

Additional information: 

Data was not collected in 2011.

Additional Study Area Information

Study Area Name: Monsoon site
Study Area Location: Monsoon site is located just North of the grassland Drought plots
Vegetation: dominated by black grama (Bouteloua eriopoda), and other highly prevalent grasses include Sporabolus contractus, S.cryptandrus, S. lexuosus, Muhlenbergia aernicola and Bouteloua gracilis.

North Coordinate:34.20143
South Coordinate:34.20143
East Coordinate:-106.41489
West Coordinate:-106.41489

Extreme Drought in Grassland Ecosystems (EDGE) Seasonal Biomass and Seasonal and Annual NPP Data at the Sevilleta National Wildlife Refuge, New Mexico (2013- present)

Abstract: 

Net primary production is a fundamental ecological variable that quantifies rates of carbon consumption and fixation. Estimates of NPP are important in understanding energy flow at a community level as well as spatial and temporal responses to a range of ecological processes.  While measures of both below- and above-ground biomass are important in estimating total NPP, this study focuses on above-ground net primary production (ANPP). Above-ground net primary production is the change in plant biomass, including loss to death and decomposition, over a given period of time. Volumetric measurements are made using vegetation data from permanent plots collected in SEV297, "Extreme Drought in Grassland Ecosystems (EDGE) Net Primary Production Quadrat Data" and regressions correlating biomass and volume constructed using seasonal harvest weights from SEV157, "Net Primary Productivity (NPP) Weight Data."

Data set ID: 

298

Core Areas: 

Additional Project roles: 

469

Keywords: 

Methods: 

Derivation of Biomass and Net primary Production:

Data from SEV297 and SEV157 are used to calculate the seasonal and annual production (i.e., biomass) of each species in each quadrat for a given year. Allometric equations derived from harvested samples of each species for each season are applied to the measured cover, height, and count of each species in each quadrat. This provides seasonal biomass for winter, spring, and fall.

Seasonal net primary production (NPP) is derived by subtracting the previous season's biomass from the biomass for the current season. For example, spring NPP is calculated by subtracting the winter weight from the spring weight for each species in a given quadrat. Negative differences are considered to be 0. Likewise, fall production is computed by subtracting spring biomass from fall biomass. Annual biomass is taken as the sum of spring and fall NPP.

Data sources: 

sev298_edgebiomass_20150818

Additional information: 

The bounding box coordinates for the corners of the polygon which encompasses the full EDGE black site are:NW: -106.729227  34.337913 Decimal DegreesNE: -106.728434  34.337937 Decimal DegreesSW: -106.729144  34.337298 Decimal DegreesSE: -106.728392  34.337310 Decimal DegreesEDGE blue:NW: -106.622610  34.342141 Decimal DegreesNE: -106.621689  34.342079 Decimal DegreesSW: -106.623365  34.341518 Decimal DegreesSE: -106.622711  34.341015 Decimal Degrees

Core Site Grid Quadrat Data for the Net Primary Production Study at the Sevilleta National Wildlife Refuge, New Mexico (2013- present)

Abstract: 

Begun in spring 2013, this project is part of a long-term study at the Sevilleta LTER measuring net primary production (NPP) across three distinct ecosystems: creosote-dominant shrubland (Site C), black grama-dominant grassland (Site G), and blue grama-dominant grassland (Site B). Net primary production is a fundamental ecological variable that quantifies rates of carbon consumption and fixation. Estimates of NPP are important in understanding energy flow at a community level as well as spatial and temporal responses to a range of ecological processes.

Above-ground net primary production is the change in plant biomass, represented by stems, flowers, fruit and and foliage, over time and incoporates growth as well as loss to death and decomposition. To measure this change the vegetation variables in this dataset, including species composition and the cover and height of individuals, are sampled twice yearly (spring and fall) at permanent 1m x 1m plots within each site. A third sampling at Site C is performed in the winter. The data from these plots is used to build regressions correlating biomass and volume via weights of select harvested species obtained in SEV999, "Net Primary Productivity (NPP) Weight Data." This biomass data is included in SEV999, "Seasonal Biomass and Seasonal and Annual NPP for Core Grid Research Sites."

Data set ID: 

289

Additional Project roles: 

450
451
452
453

Keywords: 

Methods: 

Sampling Quadrats:

Each sampling grid contains 40 1x1m quadrats in a 5x8 array. However, only 30 quadrats are sampled at each. These are quadrats 1-15 and 26-40. Thus, the middle two rows (i.e., 10 quadrats) are not sampled. Locating the Sampling Quadrats: Three core sites (B, G, and C) contain five rodent trapping and vegetation sampling webs. The vegetation grids are near these webs at each core site. At the blue grama site, the grid is located at the southern end of web 5, between webs 2 and 4. At the creosote site, the grid is east of web 3, near the road. At the black grama site, the grid is just northeast of web 5.

Collecting the Data:

Net primary production data is collected twice each year, spring and fall, for all sites. The Five Points Creosote Core Site is also sampled in winter. Spring measurements are taken in April or May when shrubs and spring annuals have reached peak biomass. Fall measurements are taken in either September or October when summer annuals have reached peak biomass but prior to killing frosts. Winter measurements are taken in February before the onset of spring growth.

Vegetation data is collected on a palm top computer. A 1-m2 PVC-frame is placed over the fiberglass stakes that mark the diagonal corners of each quadrat. When measuring cover it is important to stay centered over the vegetation in the quadrat to prevent errors caused by angle of view (parallax). Each PVC-frame is divided into 100 squares with nylon string. The dimensions of each square are 10cm x 10cm and represent 1 percent of the total area.

The cover (area) and height of each individual live (green) vegetative unit that falls within the one square meter quadrat is measured. A vegetative unit consists of an individual size class (as defined by a unique cover and height) of a particular species within a quadrat. Cover is quantified by counting the number of 10cm x 10cm squares filled by each vegetative unit.

Niners and plexidecs are additional tools that help accurately determine the cover a vegetative unit. A niner is a small, hand-held PVC frame that can be used to measure canopies. Like the larger PVC frame it is divided into 10cm x 10cm squares, each square representing 1% of the total cover. However, there are only nine squares within the frame, hence the name “niner.” A plexidec can help determine the cover of vegetative units with covers less than 1%. Plexidecs are clear plastic squares that are held above vegetation. Each plexidec represents a cover of 0.5% and has smaller dimensions etched onto the surface that correspond to 0.01%, 0.05%, 0.1%, and 0.25% cover.

It is extremely important that cover and height measurements remain consistent over time to ensure that regressions based on this data remain valid. Field crew members should calibrate with each other to ensure that observer bias does not influence data collection.

Cover Measurements:

Grasses-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 foliage is frequently mixed with dead foliage in grass clumps and this must be kept in mind during measurement as our goal is to measure only plant biomass for the current season. In general, recently dead foliage is yellow and dead foliage is gray. Within reason, try to include only yellow or green portions of the plant in cover measurement while excluding portions of the plant that are gray. This is particularly important for measurements made in the winter when there is little or no green foliage present. In winter, sometimes measurements will be based mainly on yellow foliage. Stoloniferous stems of grasses that are not rooted should be ignored. If a stem is rooted it should be recorded as a separate observation from the parent plant.

Forbs, shrubs and sub-shrubs (non-creosote)-The cover of forbs, shrubs and sub-shrubs is measured as the horizontal area of the plant. If the species is an annual it is acceptable to include the inflorescence in this measurement if it increases cover. If the species is a perennial, do not include the inflorescence as part of the cover measurement. Measure all foliage that was produced during the current season, including any recently dead (yellow) foliage. Avoid measuring gray foliage that died in a previous season.

Cacti-For cacti that consist of a series of pads or jointed stems (Opuntia phaecanthaOpuntia imbricata) measure the length and width of each pad to the nearest cm instead of cover and height. Cacti that occur as a dense ball/clump of stems (Opuntia leptocaulis) are measured using the same protocol as shrubs. Pincushion or hedgehog cacti (Escobaria viviparaSchlerocactus intertextusEchinocereus fendleri) that occur as single (or clustered) cylindrical stems are measured as a single cover.

Yuccas-Make separate observations for the leaves and caudex (thick basal stem). Break the observations into sections of leaves that are approximately the same height and record the cover as the perimeter around this group of leaf blades. The caudex is measured as a single cover. The thick leaves of yuccas make it difficult to make a cover measurement by centering yourself over the caudex of the plant. The cover of the caudex may be estimated by holding a niner next to it or using a tape measure to measure to approximate the area.

Height Measurements:

Height is recorded as a whole number in centimeters. All heights are vertical heights but they are not necessarily perpendicular to the ground if the ground is sloping.

Annual grasses and all forbs-Measure the height from the base of the plant to the top of the inflorescence (if present). Otherwise, measure to the top of the green foliage.

Perennial grasses-Measure the height from the base of the plant to the top of the live green foliage. Do not include the inflorescence in the height measurement. The presence of live green foliage may be difficult to see in the winter. Check carefully at the base of the plant for the presence of green foliage. If none is found it may be necessary to pull the leaf sheaths off of several plants outside the quadrat. From this you may be able to make some observations about where green foliage is likely to occur.

Perennial shrubs and sub-shrubs (non-creosote)-Measure the height from the base of the green foliage to the top of the green foliage, ignoring all bare stems. Do not measure to the ground unless the foliage reaches the ground.

Plants rooted outside but hanging into a quadrat-Do not measure the height from the ground. Measure only the height of the portion of the plant that is within the quadrat.

Creosote Measurements till 2013:

To measure creosote (i.e., Larrea tridenta) break the observations into two categories:

1.)Small, individual clusters of foliage on a branch (i.e., branch systems): Measure the horizontal cover of each live (i.e., green) foliage cluster, ignoring small open spaces (keeping in mind the 15% guideline stated above). Then measure the vertical "height" of each cluster from the top of the foliage to a plane created by extending a line horizontally from the bottom of the foliage. Each individual foliage cluster within a bush is considered a separate observation.

2.) Stems: Measure the length of each stem from the base to the beginning of live (i.e., green) foliage. Calculate the cumulative total of all stem measurements. This value is entered under "height" with the species as "stem" for each quadrat containing creosote. All other variable receive a default entry of "1" for creosote stem measurements. Do not measure dead stems or areas of dead foliage. If in doubt about whether a stem is alive, scrape the stem with your fingernail and check for the presence of green cambium.

Creosote Measurements 2013 and after:

Each creosote is only measured as one total cover. Each quad that contains creosote will have one cover observation for each creosote canopy in quad.

Recording the Data:

Excel spreadsheets are used for data entry and file names should begin with the overall study (npp), followed by the date (mm.dd.yy) and the initials of the recorder (.abc). Finally, "g" for "grid," along with the site abbreviation, should be added (i.e., gc, gg, gb). The final format for sites B, G, and C should be as follows: npp_core.mm.dd.yy.abgg.xls. File names should be in lowercase.

Data sources: 

sev289_nppgridquadrat_20161214.csv

Additional information: 

Other researchers involved with collecting samples/data: Chandra Tucker (CAT; 04/2014-present), Megan McClung (MAM; 04/2013-present), Stephanie Baker (SRB; 2013-present), John Mulhouse (JMM; 08/2009-06/2013).

Response of Vegetation and Microbial Communities to Monsoon Precipitation Manipulation in a Mixed Blue and Black Grama Grassland at the Sevilleta National Wildlife Refuge, New Mexico

Abstract: 

The purpose of this project is to test the hypothesis that the smallest 50% of precipitation events during the monsoon season affect microbial functioning and grassland productivity in mixed grasslands of B.eriopoda and B. gracilis at the SNWR. At the SNWR, the summer monsoon season accounts for 60% of total annual precipitation and drives the majority of vegetation productivity during the year; the largest 25% of precipitation events account for the majority of this precipitation. I predict that important ecological variables such as nutrient and soil moisture availability are disproportionately influenced by smaller events. The proposed project will help tease apart the importance of precipitation event classes on nutrient availability and grassland aboveground net primary production (ANPP). This research will also provide a basis for understanding how increased aridity in the U.S. southwest due to increasing global surface temperature and altered precipitation could affect grassland communities at the SNWR.

Additional Project roles: 

34
35

Data set ID: 

286

Core Areas: 

Keywords: 

Methods: 

We will implement 10 open plots (control) and 10 precipitation exclosure plots(treatment; 20 total plots) at a mixed blue and black grama grassland site at the SNWR. In this experiment, treatment plots will only receive the largest 50% of precipitation events. This will maintain statistically similar total precipitation between control and treatment plots because the smallest 50% of events have an insignificant effect on total seasonal precipitation. How these small events are linked to microbial activity and vegetation productivity is still very much unknown. I predict that soil microbial activity and nutrient availability will differ between control and treatment plots and will result in differing vegetation ANPP between them. These effects may become more distinct as time progresses, which is the reason for conducting this research for a series of monsoon seasons.

Existing precipitation exclosures (2.45 m x 2.45 m) will be employed at the mixed grassland site. We will implement 20 total plots (10 control, 10 treatment; approx. 500 m2 total area). Temporary site infrastructure will include 10 precipitation exclosures, a water tank (1100 gal.) and soil moisture probes. This infrastructure currently exists at the mixed grassland site and will be adopted from Michell Thomey's project entitled, "Soil moisture extremes and soil water dynamics across a semiarid grassland ecotone."

Precipitation is the only independent variable in this experiment. Using precipitation exclosures, I will remove all ambient precipitation from treatment plots from DOY 182-273. Ambient daily precipitation thatexceeds the estimated 50% threshold will be delivered to the plots within 24 hours of an event. Delivered precipitation will be adjusted for atmospheric demand differences. 

Dependent variables in this experiment are vegetation ANPP, soil nitrogen content, soil enzymatic activityand soil moisture content. Vegetation biomass will be collected from the sites on DOY 181 and 274. Soil enzymatic activity will be determined approximately 4 times per monsoon season using plot soil samples. Soil nitrogen content will be measured under vegetation using nitrogen probes. Volumetric soil moisture content [m3 m-3] will be measured continuously using soil moisture probes (30 cm depth). 

Water Potential Data From Pinyon-Juniper Forest at Sevilleta National Wildlife Refuge, New Mexico

Abstract: 

This dataset consists of profiles of soil water potential measured via in situ thermocouple psychrometers located within a rainfall manipulation experiment in a piñon-juniper woodland. The sensors are centrally located within 40 m x 40 m water addition, water removal, infrastructure control, and ambient control plots. The profiles are installed under each of ten target piñon and juniper trees (five of each species) which were also used for other physiological measurements, as well as at five intercanopy areas. The raw sensor output (in μV) has been temperature-corrected and individual calibration equations applied.

Background: This sensor array is part of a larger experiment investigating the mechanisms of drought-related mortality in the piñon-juniper woodland. Briefly, one hypothesis is that, during periods of extended, very-negative, soil water potential (“drought”) trees experience xylem tensions greater than their threshold for cavitation, lose their hydraulic connection to the soil, dessicate and die. A second hypothesis is that in order to avoid this hydraulic failure, trees restrict water loss via reduction in stomatal conductance which also limits the diffusion of CO2 for photosynthesis, and eventually may starve to death depending on the drought duration. 

The goal of the project is to apply drought stress on an area significantly larger than the scale of individual trees to determine whether hydraulic failure or carbon starvation is a more likely mechanism for mortality under drought conditions. The cover control treatment replicates the microenvironment created under the plastic rainfall removal troughs (slightly elevated soil and air temperatures and relative humidity) without removing ambient precipitation. The water addition treatment is intended to simulate 150% of the 30-yr average rainfall via n = 6 19-mm super-canopy applications during the growing season (April-October). More details on the experiment can be found in Pangle et al. 2012 Ecosphere 3(4) 28 (http://dx.doi.org/10.1890/ES11-00369.1). These three treatments, in addition to an ambient control with no infrastructure, are applied to three replicated blocks, one on relatively level terrain, one on a southeast-facing slope, and one on a north-facing slope. The soil psychrometers were installed in the southeast-facing block only, to measure the effectiveness of the treatments on plant-available soil moisture.

For the purposes of comparing soil water potential under various cover types (piñon, juniper, intercanopy), it should be noted that significant tree mortality has occurred on Plot 10. As described below, on 5 August 2008 the site was struck by lightening and many of the soil psychrometers were rendered inoperable. At approximately the same time, four of the five target piñon trees in the southeast-facing drought plot (Plot 10) started browning and it was discovered that they had bark beetle (Ips confusus) galleries and were infected with Ophiostoma fungi. By October 2008 those trees (T1, T2, T4, and T5) had dropped all their needles. Therefore the psychrometers buried under them were no longer located “under trees” after that time. By June 2009 the remaining target piñon (T3) died. By March 2010, one of the target juniper trees (T10) had died. At the time of this writing (April 2011) it is anticipated that more of the juniper trees on P10 will die during this year. 

Data set ID: 

285

Additional Project roles: 

30

Core Areas: 

Keywords: 

Methods: 


Methods:  Within Plots 9-12 of the larger PJ rainfall manipulation experiment, thermocouple psychrometers (Wescor Inc., Logan, UT, USA) were installed. Soil psychrometers profiles were placed under each of the initial ten target trees in each plot, and at the same five intercanopy areas that were instrumented to measure soil and air temperature and soil volumetric water at 5 cm depth. Each profile consisted of sensors at (1) 15 cm; (20) cm; and (3) as deep as could be augered and installed by hand, generally 50-100 cm depth. Sensors were calibrated with four NaCl solutions of known water potential before field deployment.

Sensors are controlled via a Campbell Scientific CR-7 datalogger (Campbell Scientific, Logan, UT, USA). The datalogger takes measurements every 3 h but soil water potential does not change that fast and the daytime measurements are generally unusable because of thermal gradients between the datalogger and the sensors, therefore the data presented here are only the 3:00 AM timepoints.

Note that on 5 August 2008 the site was struck by lightening. Many of the soil psychrometers were destroyed by ground current, with the worst damage on the drought and cover control plots where the metal support posts for the infrastructure may have helped to propagate ground current. Some of those sensors were eventually replaced but in the case of the infrastructure plots we were limited to installing new sensors between the plastic troughs because it was impossible to auger under the plastic. Therefore, while the original installation was random with regard to the pattern of plastic domes and troughs, the replacement installation was exclusively outside the plastic and the data may therefore be biased towards wetter microsites.

Instrumentation: 


Instrument Name: thermocouple psychrometer with stainless steel screen

Manufacturer: Wescor, Inc, Logan, UT, USA

Model Number: PST-55

Stress Response from Male-Male Competition in Varying Thermal Environments at the Sevilleta National Wildlife Refuge, New Mexico

Abstract: 

Environmental temperature influences virtually all aspects of organismal performance, including fitness. And since temperature varies throughout space and time, organisms must regularly compete for optimal thermal habitats, much as they do for other resources (e.g. territory, food, or females). However, competition for thermal resources imposes costs, often in the form of a stress response (i.e. increased corticosterone production). Elevated corticosterone promotes physiological and behavioral responses that can increase an organism’s chance of survival, but if left in an organism’s system for too long, it will reduce immunity, degenerate neurons, and lower fitness. Previous theoretical and empirical work indicates that, all else being equal, patchy thermal landscapes reduce the energetic cost of thermoregulation. Therefore, I hypothesize that lizards exposed to patchy distributions of preferred temperatures will have less stress (and thus lower levels of corticosterone) than those exposed to clumped distributions. Furthermore, patchily distributed resources are more difficult for territorial males to monopolize, and thus, subordinate males in patchy thermal landscapes should experience less stress than subordinate males in clumped thermal landscapes.

Additional Project roles: 

32
33

Data set ID: 

284

Core Areas: 

Keywords: 

Methods: 

Experimental design: Starting in the July of 2012, I will initiate this project as part of a continuing large-scale field study at Sevilleta LTER site in collaboration with PI Michael Angilletta’s Spatially Explicit Theory of Thermoregulation project. As in past research conducted in 2008, 2009 and 2011, I will use male Yarrow’s spiny lizard. This lizard thermoregulates accurately in the absence of predators14,15 and aggressively defends resources from conspecific males14,16.

Nine outdoor arenas (20 x 20 m), consisting of sheet metal walls and a canopy of shade cloth, will be used to manipulate the thermal environments. Among the arenas, three patterns of shade patches will be replicated three times each to generate distinct thermal landscapes (see Figure 1).  Lizards will be paired by size: large dominant (22-30 g) with a small subordinate (15-21 g). Each pair (n = 12) will be randomly assigned one of the thermal environments. Prior to each trial, males will be habituated to their arenas for 10 days. During this period, each male will be exposed to the thermal arena every other day (for a 24-h period) in the absence of a competitor (total of 5 days per animal). After the habituation period, males will be placed in arenas for a 4-day testing period. Males will spend two of these days in isolation and the other two in competition. Half the pairs will start the trial in isolation (solitary treatment), and the other half of the pairs will start the trial in competition (social treatment). A matched pair of lizards will be placed together in one arena, and the other two arenas will each have one individual (either small or large) placed into it.  After two days, all lizards will be captured and blood samples will be collected within three minutes (speed of collection is necessary to prevent handling stress from affecting plasma corticosterone levels17). Blood will be taken from the orbital sinus with a glass capillary tube and then taken back to the lab where the plasma will be obtained through centrifugation. Plasma will be stored at -80˚C for hormone assays18. After bleeding, solitary lizards will be placed together in one arena, and the previously paired individuals will be separated and split between the two remaining arenas. Thus, a completed habituation and observation set for six pairs (two pairs per type of thermal environment) will take 14 days. And 3 sets will be conducted per season giving a total of 18 pairs per season in each thermal environment (54 pairs in isolation and competition per season). Mixed modeling procedures in the statistical software R will be used to quantify the effects of competition and thermal patchiness on the corticosterone levels of lizards19.


 Fig. 1. Patterns of shade patches for arenas (each replicated 3x).

Konza Species Composition: Fire by Nitrogen Project

Abstract: 

The distribution, structure and function of mesic savanna grasslands are strongly driven by fire regimes, grazing by large herbivores, and their interactions. This research addresses a general question about our understanding of savanna grasslands globally: Is our knowledge of fire and grazing sufficiently general to enable us to make accurate predictions of how these ecosystems will respond to changes in these drivers over time? Some evidence suggests that fire and grazing influence savanna grassland structure and function differently in South Africa (SA) compared to North America (NA). These differences have been attributed to the contingent factors of greater biome age, longer evolutionary history with fire and grazing, reduced soil fertility, and greater diversity of plants and large herbivores in SA. An alternative hypothesis is that differences in methods and approaches used to study these systems have led to differing perspectives on the role of these drivers. If the impacts of shared ecosystem drivers truly differ between NA and SA, this calls into question the generality of our understanding of these ecosystems and our ability to forecast how changes in key drivers will affect savanna grasslands globally. Since 2006, an explicitly comparative research program has been conducted to determine the degree of convergence in ecosystem (productivity, N and C cycling) and plant community (composition, diversity, dynamics) responses to fire and grazing in SA and NA.

Thus far, initial support has been found for convergence at the ecosystem level and divergence at the community level in response to alterations in both fire regimes and grazing. However, there have also been two unexpected findings (1) the ways in which fire and grazing interact differed between NA and SA, and (2) the rate of change in communities when grazers were removed was much greater in NA than in SA. These unexpected findings raise a number of important new questions: (Q1) Will exclusion of grazing eventually affect community structure and composition across all fire regimes in SA? (Q2) Will these effects differ from those observed in NA? (Q3) What are the determinants of the different rates of community change? (Q4) How will these determinants influence future trajectories of change? (Q5) Will the different rates and trajectories of community change be mirrored by responses in ecosystem function over time? This project is based on a large herbivore exclusion study established within the context of long-term (25-50+ yr) experimental manipulations of fire frequency at the Konza Prairie Biological Station (KPBS) in NA and the Kruger National Park (KNP) in SA. The suite of core studies and measurements include plant community composition, ANPP, and herbivore abundance and distribution at both study sites to answer these research questions.

Data set ID: 

268

Core Areas: 

Keywords: 

Methods: 

We used comparable experimental designs and sampling procedures at both URF and KPBS. At URF we used three replicate plots (not hayed or mowed) that have been burned every 1 and 3 years in the spring, and those left unburned (N=9 plots). At KPBS, we established replicate plots in experimental watersheds burned every 1 and 4 years in the spring, and those left unburned (N=9 plots). Thus, the only difference in design between NA and SA was the intermediate burn frequency. In 2005 at both sites we established four 2x2m areas in each replicate of the 1-yr, 3-4 yr burned, and unburned plots (N=36 subplots). We then randomly selected two of the subplots for the fertilization treatment and the other two subplots served as controls (Fig. 1). Starting in 2006 at KPBS and 2007 at URF, we began adding 10 gN/m2/yr as NH4+NO3- to assess the interactive effects of fire frequency and nitrogen limitation on plant community composition, structure and dynamics.

Fig. 1. Experimental design and sampling for the proposed studies: A) the role of long-term fire regimes (without megaherbivores), B) the importance of grazing and grazing/fire interactions, and C) the role of megaherbivore diversity. Moveable exclosures (3/plot) will be used to estimate ANPP in the grazed plots.  N addition subplots (2 x 2 m) will be divided into 4 1 x 1 plots, with two designated for plant species composition sampling and the other two for destructive sampling. Soil samples will be collected from areas not designated for ANPP or plant composition sampling. Note that the same annually and infrequently burned plots at Kruger and Konza will be used in (B) and (C). In addition, similar plots will be established minus the N addition subplots in the 1-yr and 4-yr burned blocks of the Buffalo enclosure for (C). 

Each of the 2x2m subplots was divided into four 1x1m quadrats. Annually since 2005 (prior to nitrogen addition) canopy cover of each species rooted in each quadrat was visually estimated twice during the growing season to sample early and late season species. As a surrogate for aboveground production, we measured light availability at the end of the growing season above the canopy at the ground surface in each quadrat (N=4 per subplot) using a Decagon ceptometer. 

Net primary production measurements: Prior to the 2005 growing season we established plots (13.7 m by 18.3 m) in ungrazed areas burned annually, at 3–4-year intervals, and unburned (n  = 3 per fire treatment) at both KBPS and URF. Areas with trees or large shrubs were avoided as our main goal was to evaluate responses in the herbaceous plant community. ANPP was estimated from end-of-season harvests starting in 2005 (September for KBPS, April for URF). In 10, 0.1-m2 (20 cm by 50 cm) quadrats randomly located in each plot (n  = 30/treatment/site), we harvested the vegetation at ground level and separated it into grass, forb, and previous year’s dead biomass. Samples were dried at 60C to a constant weight. For annually burned plots, total biomass harvested represents ANPP. For the intermediate and unburned sites, we calculated ANPP by summing all but the previous year’s dead component.

To assess the impacts of fire on ANPP in grazed areas, we established herbivore exclusion treatments in KBPS in North America and KNP in South Africa. Herbivore exclosures in grazed areas in KPBS and KNP were erected prior to the 2006 growing season. The exclosures were 7 m in diameter, 2 m tall, and constructed of diamond mesh (5-cm diameter). Seven exclosures were established in each of three blocks of the three fire treatments— annually burned, intermediate burn (3- years for KNP or 4-years for KPBS), and unburned (n = 21 exclosures/treatment/site). As our focus was on ANPP responses of the herbaceous layer, exclosures were not located beneath trees or where dense shrub patches were present. Additionally, in the Satara region of KNP is a 900-ha permanent enclosure containing 80–90 adult African buffalo (S. caffer). This enclosure was erected in 2000 and was divided into six areas (100–200 ha each), with these burned on a rotational basis including plots burned annually and plots that were unburned. We used the unburned and annually burned areas in the buffalo enclosure to provide a direct comparison for determining the effects of a single-species large grazer in KNP and KPBS, and to assess the effects of large herbivore diversity at adjacent sites in KNP. Similar exclosures were built in the African buffalo enclosure at KNP. We placed 7 exclosures in the three blocks of each fire treatment (annually burned and unburned) resulting in 21 exclosures/treatment. We sampled ANPP by harvesting plant biomass from three 0.1 m2 quadrats per herbivore exclosure at the end of the growing season starting in 2006. 

Additional information: 

Data are collected twice each year at each site. Sample periods are equivalent to spring and late summer at each study site (December/January and March/April in South Africa, May and September in North America.

Where the Data were Collected: 

Ukulinga Research Farm, Pietermaritzburg, South Africa; Satara Region of Kruger National Park, South Africa; Konza Prairie Biological Station, North America

Additional Geographic Metadata:  

Ukulinga Research Farm (URF), South Africa. The URF of the University of KwaZulu-Natal is located in Pietermaritzburg, in southeastern South Africa (30o 24’ S, 29o 24’ E). The site is dominated by native perennial C4 grasses, such as Themeda triandra and Heteropogon contortus, that account for much of the herbaceous aboveground net primary production (ANPP). Mean annual precipitation is 790 mm, coming mostly as convective storms during summer (Oct-Apr). Summers are warm with a mean monthly maximum of 26.4oC in February, and winters are mild with occasional frost. Soils are fine-textured and derived from shales. There has been no grazing at this site for >60 years. Long-term experimental plots were established at URF in 1950 with the objective of determining the optimal fire and/or summer cutting regime to maximize hay production. The experiment is a randomized block (three replicates) split-plot design with four whole-plot haying treatments and 11 subplot fire or mowing treatments. Subplot sizes are 13.7 x 18.3 m. 

Kruger National Park (KNP), South Africa. The KNP is a 2 million ha protected area of savanna grassland that includes many of the large herbivores common to southern Africa (22º 25' to 25º 2 32' S, 30º 50' to 32º 2' E). The extant abundance and grazing intensity of herbivores in KNP is considered moderate for regional savanna grasslands. In the south-central region of KNP where our research takes place, average rainfall is 537 mm with most falling during the growing season (Oct-Apr). The dormant season is mild, dry and frost free, and summers are warm with mean monthly maximum air temperature of 28.9oC in January. Because of the importance of fire in savanna grassland ecosystems, the Experimental Burn Plot (EBP) experiment was initiated in 1954 to examine the effects of fire frequency (control-no fire, 1-, 2-, 3-, 4- and 6-yr return interval) and season [early spring (Aug), spring (Oct), mid-summer (Dec), late summer (Feb), and fall (Apr)] on vegetation communities in the park. Four blocks of 12 plots (two were later split for the 4- and 6-yr trts), each ~7 ha (370 x 180 m) in size, were established in four primary vegetation types covering the two major soil types (granites and basalts) and spanning the precipitation gradient in the park. Each plot has 50+ years of known fire history, and native herbivores have had unrestricted access, thus fire and grazing effects are combined. This research focuses on the EBPs located near Satara where precipitation, soil type, and the mix of herbaceous and woody plants are similar to KPBS. Vegetation on the blocks is co-dominated by C4 grasses, such as Bothriochloa radicans, Panicum coloratum and Digiteria eriantha, and woody plants, such as Acacia nigrescens and Sclerocarya birrea.  Soils are fine-textured and derived from basalts. Adjacent to one of the Satara blocks is the Cape buffalo enclosure, erected in 2000 for veterinary purposes. The 200 ha permanent enclosure contains 65-80 animals and is divided into 4 blocks burned on a rotational basis. The grazing intensity inside is comparable to the moderate levels imposed in the park and at KPBS. Two blocks are burned annually while others are burned infrequently (approximately once every 4-yr). 

Konza Prairie Biological Station (KPBS), North America. The KPBS is a 3,487 ha savanna grassland in northeastern Kansas, USA (39o 05’ N, 96o 35’ W) dominated by native perennial C4 grasses such as Andropogon gerardii and Sorghastrum nutans that account for the majority of ANPP. Scattered shrub and tree species include Cornus drummondii, Gleditsia triacanthos, and Prunus spp. Numerous sub-dominant grasses and forbs contribute to the floristic diversity of the site. The climate is continental, with mean July air temperature of 27°C. Annual precipitation is ca. 820 mm/year, with 75% falling as rain during the Apr-Oct growing season. Soils are fine textured, silty clay loams derived from limestone and shales. KPBS includes fully replicated watershed-level fire and fire/grazing treatments, in place since 1977 and 1987, respectively.  Replicate watersheds (mean size ~60ha) are burned at 1-, 2-, 4-, 10- and 20-yr intervals, mainly in April, to encompass a range of likely natural fire frequencies and management practices. A subset of watersheds has not been grazed for more than 30 years. To address the role of native grazers and fire/grazing interactions, bison (~260 individuals) were reintroduced to KPBS in a 1000-ha fenced area that includes replicate watersheds burned in the spring at 1-, 2-, 4- and 20-year intervals. The overall grazing intensity is considered moderate.

Study Area 1:  

Study Area Name:  Ukulinga Research Farm

Study Area Location: Near Pietermaritzburg, South Africa 

Elevation: 840 m above sea level

Landform: Colluvium fan

Geology: Marine shales and dolerite colluvium

Soils: Dystric leptosols, Chromic luvisols, Haplic plinthisols

Vegetation: Native grassland

Climate: Mean annual precipitation is 844 mm, Mean annual temperature 17.6C

Site history: Ungrazed since 1950

Single Point: 29o 40’ S / 30o 20’ E

Study Area 2:  Kruger National Park, South Africa

Study Area Name: Satara Experimental Burn Plots and Cape Buffalo Exclosure

Study Area Location: Near Satara rest camp

Elevation:  240-320 meters above sea level

Landform:  Level Upland

Geology: Basalts

Soils: Rhodic nitisols, Haplic luvisols, Leptic phaeozems

Vegetation: Native grassland

Climate: Mean annual precipitation 544 mm; mean annual temperature 21.2–23.3C

Site history: Grazed by native herbivores

Single Point: 23–25o S /30-31o E

   

Study Area 3:  Konza Prairie Biological Station

Study Area Name: Konza Prairie

Study Area Location: Watersheds N20B, N4D, N1B, N4B; 1D, 4F, 20B

Elevation: 320-444 meters above sea level

Landform: Alluvial terrace

Geology: Cherty limestone and shale

Soils: Udic argiustolls

Vegetation: Native grassland

Climate: Mean annual precipitation 835 mm; mean annual temperature 12.7C

Site history: Ungrazed watersheds (since 1971), watersheds grazed by native herbivores (since 1987)

Single Point: 39o 05.48’ N / 96o 34.12’ W

Gunnison’s Prairie Dog Use of Resource Pulses in a Chihuahuan Desert Grassland at the Sevilleta National Wildlife Refuge, New Mexico: Re-sight Scan Data

Abstract: 

Seasonal environments experience cyclical or unpredictable pulses in plant growth that provide important resources for animal populations, and may affect the diversity and persistence of animal communities that utilize these resources. The timing of breeding cycles and other biological activities must be compatible with the availability of critical resources for animal species to exploit these resource pulses; failure to match animal needs with available energy can cause population declines. Adult Gunnison’s prairie dogs emerge from hibernation and breed in early spring, when plant growth is linked to cool-season precipitation and is primarily represented by the more nutritious and digestible plants that utilize the C3 photosynthetic pathway. In contrast, summer rainfall stimulates growth of less nutritious plants using the C4 photosynthetic pathway. Prairie dogs should therefore produce young during times of increased productivity from C3 plants, while pre-hibernation accumulation of body fat should rely more heavily upon C4 plants.  If seasonal availability of high-quality food sources is important to Gunnison’s prairie dog population growth, projected changes in climate that alter the intensity or timing of these resource pulses could result in loss or decline of prairie dog populations.  This project will test the hypothesis that population characteristics of Gunnison's prairie dog, an imperiled grassland herbivore, are associated with climate-based influences on pulses of plant growth.

Data set ID: 

242

Core Areas: 

Additional Project roles: 

40
41

Keywords: 

Methods: 

Gunnison’s prairie dogs will be monitored at 6 colonies, with 3 colonies each occurring with the range of prairie and montane populations. Colonies for study within the prairie populations occur at Sevilleta National Wildlife Refuge (n = 3 prairie populations) and at Vermejo Park Ranch (n = 3 montane populations).  Live-trapping of prairie dogs will be conducted during 3 periods of the active seasons—following emergence (April), after juveniles have risen to the surface (mid-to-late June), and pre-immergence (beginning in August).  Trapping will occur for 3-day periods, following pre-baiting with open traps.  At capture, sex and body mass of each individual will be recorded.  Blood and subcutaneous body fat samples will be collected nondestructively for analysis of isotopic composition.  Prairie dogs will be marked with dye, and released on site immediately following processing.  After trapping periods at each site have concluded, population counts will be conducted during 2-3 re-sighting (or recapture) periods for each prairie dog colony.  Resighting observation periods will be ~3 hours in length, and consist of 2-6 systematic scans of the entire colony, beginning and ending from marked points outside of the colony boundary.  During each observation period, prairie dogs will be counted, recorded as marked or unmarked, and location on the colony noted.  

Vegetation cover and composition measurements will be collected (or obtained at Sevilleta, where such data is already being collected) during pre- and post-monsoon periods of the active season.  Total cover will be measured by plant species (or to genus if species is indeterminable). Total cover will be measured at 12 grid points per colony using Daubenmire frames (0.5 m x 0.5 m), and at 12 grid locations 200-800 m outside of each colony boundary.  Adjacent to each Daubenmire frame, a 20 cm x 30 cm sample of vegetation will be clipped and dried for determination of volumetric moisture content of vegetation.  

Primary productivity variables (cover, moisture content) will be tested for correlations to individual and population-level condition indicators in prairie dogs.  Carbon isotope ratios (δ13C) from prairie dog blood and fat samples will be analyzed on a continuous flow isotope ratio mass spectrometer.  The relative contribution of C3 and C4 plants to the diet of each individual will be determined based upon δ13C ratios for C3 and C4 plants in the study area and a 2-endpiont mixing model, and will be calculated for each individual animal, population and season.  Population estimates will be calculated using mark-resight estimates, and compared to maximum above-ground counts.  The influence of resource pulses on prairie dog population parameters will be tested by comparing the vegetation cover, moisture content, and ratio of total C3:C4 plant cover to the ratio of C3:C4 plants in prairie dog diets, population estimates, and juvenile:adult ratios as an index to population recruitment.   

Instrumentation: 

*Instrument Name: Continuous flow isotope ratio mass spectrometer

*Manufacturer: Thermo-Finnigan IRMS  Delta Plus 

*Instrument Name: Elemental Analyzer

*Manufacturer: Costech

*Model Number: ECS4010

Additional information: 

Other Field Crew Members: Talbot, William; Duran, Ricardo; Gilbert, Eliza; Donovan, Michael; Nichols, Erv; Sevilleta LTER prairie dog field crew led by Koontz, Terri; Sevilleta NWR prairie dog field crew led by Erz, Jon.

Tissue samples are analyzed for stable carbon isotope ratios in stable isotope laboratory operated by Dr. Zachary Sharp and Dr. Nicu-Viorel Atudorei of the Department of Earth and Planetary Sciences, University of New Mexico.

Gunnison's Prairie Dog Use of Resource Pulses in a Chihuahuan Desert Grassland at the Sevilleta National Wildlife Refuge, New Mexico: Capture Data

Abstract: 

Seasonal environments experience cyclical or unpredictable pulses in plant growth that provide important resources for animal populations, and may affect the diversity and persistence of animal communities that utilize these resources. The timing of breeding cycles and other biological activities must be compatible with the availability of critical resources for animal species to exploit these resource pulses; failure to match animal needs with available energy can cause population declines. Adult Gunnison’s prairie dogs emerge from hibernation and breed in early spring, when plant growth is linked to cool-season precipitation and is primarily represented by the more nutritious and digestible plants that utilize the C3 photosynthetic pathway. In contrast, summer rainfall stimulates growth of less nutritious plants using the C4 photosynthetic pathway. Prairie dogs should therefore produce young during times of increased productivity from C3 plants, while pre-hibernation accumulation of body fat should rely more heavily upon C4 plants. If seasonal availability of high-quality food sources is important to Gunnison’s prairie dog population growth, projected changes in climate that alter the intensity or timing of these resource pulses could result in loss or decline of prairie dog populations. This project will test the hypothesis that population characteristics of Gunnison's prairie dog, an imperiled grassland herbivore, are associated with climate-based influences on pulses of plant growth.

Data set ID: 

241

Core Areas: 

Additional Project roles: 

37
38
39

Keywords: 

Methods: 

Gunnison’s prairie dogs will be monitored at 6 colonies, with 3 colonies each occurring with the range of prairie and montane populations. Colonies for study within the prairie populations occur at Sevilleta National Wildlife Refuge (n = 3 prairie populations) and at Vermejo Park Ranch (n = 3 montane populations). Live-trapping of prairie dogs will be conducted during 3 periods of the active seasons—following emergence (April), after juveniles have risen to the surface (mid-to-late June), and pre-immergence (beginning in August). Trapping will occur for 3-day periods, following pre-baiting with open traps. At capture, sex and body mass of each individual will be recorded. Blood and subcutaneous body fat samples will be collected nondestructively for analysis of isotopic composition. Prairie dogs will be marked with dye, and released on site immediately following processing. After trapping periods at each site have concluded, population counts will be conducted during 2-3 re-sighting (or recapture) periods for each prairie dog colony. Resighting observation periods will be ~3 hours in length, and consist of 2-6 systematic scans of the entire colony, beginning and ending from marked points outside of the colony boundary. During each observation period, prairie dogs will be counted, recorded as marked or unmarked, and location on the colony noted. Vegetation cover and composition measurements will be collected (or obtained at Sevilleta, where such data is already being collected) during pre- and post-monsoon periods of the active season. Total cover will be measured by plant species (or to genus if species is indeterminable). Total cover will be measured at 12 grid points per colony using Daubenmire frames (0.5 m x 0.5 m), and at 12 grid locations 200-800 m outside of each colony boundary. Adjacent to each Daubenmire frame, a 20 cm x 30 cm sample of vegetation will be clipped and dried for determination of volumetric moisture content of vegetation. Primary productivity variables (cover, moisture content) will be tested for correlations to individual and population-level condition indicators in prairie dogs. Carbon isotope ratios (δ13C) from prairie dog blood and fat samples will be analyzed on a continuous flow isotope ratio mass spectrometer. The relative contribution of C3 and C4 plants to the diet of each individual will be determined based upon δ13C ratios for C3 and C4 plants in the study area and a 2-endpiont mixing model, and will be calculated for each individual animal, population and season. Population estimates will be calculated using mark-resight estimates, and compared to maximum above-ground counts. The influence of resource pulses on prairie dog population parameters will be tested by comparing the vegetation cover, moisture content, and ratio of total C3:C4 plant cover to the ratio of C3:C4 plants in prairie dog diets, population estimates, and juvenile:adult ratios as an index to population recruitment.

Instrumentation: 

Instrument Name: Continuous flow isotope ratio mass spectrometer Manufacturer: Thermo-Finnigan IRMS Delta Plus Model Number: Instrument Name: Elemental Analyzer Manufacturer: Costech Model Number: ECS4010

Additional information: 

Field Crew: Hayes, Chuck; Talbot, William; Duran, Ricardo; Gilbert, Eliza; Donovan, Michael; Nichols, Erv; Sevilleta LTER prairie dog field crew led by Koontz, Terri; Sevilleta NWR prairie dog field crew led by Erz, Jon.

Rainfall Manipulation Study Vegetation Data from the Chihuahuan Desert Grassland and Creosote Shrubland at the Sevilleta National Wildlife Refuge, New Mexico (2003-2011)

Abstract: 

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. 

Data set ID: 

147

Core Areas: 

Additional Project roles: 

336
337
338
339

Keywords: 

Methods: 

Quadrat measurements 

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.

Creosote:

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.

Grasses:

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.  

Forbs:

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.

Vines:

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.

Seedlings:

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 measurements

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.

Creosote:

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.  

Perennial grasses:

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 measurements

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.  

Creosote:

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.

Non-Vegetation Measurements

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:

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.     

Soil:

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.  

Rock:   

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.

Data sources: 

sev147_droughtveg_11142011

Maintenance: 

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

Additional information: 

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.

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