rain

Warming-El Nino-Nitrogen Deposition Experiment (WENNDEx): Soil Temperature, Moisture, and Carbon Dioxide Data from the Sevilleta National Wildlife Refuge, New Mexico (2011 - present)

Abstract: 

Humans are creating significant global environmental change, including shifts in climate, increased nitrogen (N) deposition, and the facilitation of species invasions. A multi-factorial field experiment is being performed in an arid grassland within the Sevilleta National Wildlife Refuge (NWR) to simulate increased nighttime temperature, higher N deposition, and heightened El Niño frequency (which increases winter precipitation by an average of 50%). The purpose of the experiment is to better understand the potential effects of environmental drivers on grassland community composition, aboveground net primary production and soil respiration. The focus is on the response of two dominant grasses (Bouteloua gracilis and B eriopoda), in an ecotone near their range margins and thus these species may be particularly susceptible to global environmental change.

It is hypothesized that warmer summer temperatures and increased evaporation will favor growth of black grama (Bouteloua eriopoda), a desert grass, but that increased winter precipitation and/or available nitrogen will favor the growth of blue grama (Bouteloua gracilis), a shortgrass prairie species. Treatment effects on limiting resources (soil moisture, nitrogen availability, species abundance, and net primary production (NPP) are all being measured to determine the interactive effects of key global change drivers on arid grassland plant community dynamics and ecosystem processes. This dataset shows values of soil moisture, soil temperature, and the CO2 flux of the amount of CO2 that has moved from soil to air.

On 4 August 2009 lightning ignited a ~3300 ha wildfire that burned through the experiment and its surroundings. Because desert grassland fires are patchy, not all of the replicate plots burned in the wildfire. Therefore, seven days after the wildfire was extinguished, the Sevilleta NWR Fire Crew thoroughly burned the remaining plots allowing us to assess experimentally the effects of interactions among multiple global change presses and a pulse disturbance on post-fire grassland dynamics.

Core Areas: 

Data set ID: 

305

Keywords: 

Methods: 

Experimental Design

Our experimental design consists of three fully crossed factors (warming, increased winter precipitation, and N addition) in a completely randomized design, for a total of eight treatment combinations, with five replicates of each treatment combination, for a total of 40 plots. Each plot is 3 x 3.5 m. All plots contain B. eriopoda, B. gracilis and G. sarothrae. Our nighttime warming treatment is imposed using lightweight aluminum fabric shelters (mounted on rollers similar to a window shade) that are drawn across the warming plots each night to trap outgoing longwave radiation. The dataloggers controlling shelter movements are programmed to retract the shelters on nights when wind speeds exceed a threshold value (to prevent damage to shelters) and when rain is detected by a rain gauge or snow is detected by a leaf wetness sensor (to prevent an unintended rainout effect).

Each winter we impose an El Nino-like rainfall regime (50% increase over long-term average for non-El Nino years) using an irrigation system and RO water. El Nino rains are added in 6 experimental storm events that mimic actual El Nino winter-storm event size and frequency. During El Nino years we use ambient rainfall and do not impose experimental rainfall events. For N deposition, we add 2.0 g m-2 y-1 of N in the form of NH4NO3 because NH4 and NO3 contribute approximately equally to N deposition at SNWR (57% NH4 and 43% NO3; Bez et al., 2007). The NH4NO3 is dissolved in 12 liters of deionized water, equivalent to a 1 mm rainfall event, and applied with a backpack sprayer prior to the summer monsoon. Control plots receive the same amount of deionized water.

Soil Measurements

Soil temperature is measured with Campbell Scientific CS107 temperature probes buried at 2 and 8 cm In the soil. Soil volume water content, measured with Campbell Scientific CS616 TDR probes is an integrated measure of soil water availability from 0-15 cm deep in the soil. Soil CO2 is measured with Vaisala GM222 solid state CO2 sensors. For each plot, soil sensors are placed under the canopy of B. eriopoda at three depths: 2, 8, and 16 cm. Measurements are recorded every 15 minutes.

CO2 fluxes are calculated using the CO2, temperature, and moisture data, along with ancillary variables following the methods of Vargas et al (2012) Global Change Biology

Values of CO2 concentration are corrected for temperature and pressure using the ideal gas law according to the manufacturer (Vaisala). We calculate soil respiration using the flux-gradient method (Vargas et al. 2010) based on Fick’s law of diffusion where the diffusivity of CO2 is corrected for temperature and pressure (Jones 1992) and calculated as a function of soil moisture, porosity and texture (Moldrup et al. 1999).

Data sources: 

sev305_wenndex_soiltemp_moisture_co2_2011
sev305_wenndex_soiltemp_moisture_co2_2012
sev305_wenndex_soiltemp_moisture_co2_2013
sev305_wenndex_soiltemp_moisture_co2_2014
sev305_wenndex_soiltemp_moisture_co2_2015

Instrumentation: 

Instrument Name: Solid State Soil CO2 sensor
Manufacturer: Vaisala
Model Number: GM222

Instrument Name: Temperature Probe
Manufacturer: Campbell Scientific
Model Number: CS107

Instrument Name: Water Content Reflectometer Probe
Manufacturer: Campbell Scientific
Model Number: CS616

Monsoon Rainfall Manipulation Experiment (MRME) Soil Temperature, Moisture and Carbon Dioxide Data from the Sevilleta National Wildlife Refuge, New Mexico (2012- 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. It is predicted that changes in event size and variability will alter grassland productivity, ecosystem processes, and plant community dynamics. In particular, we predict that many small events will increase soil CO2 effluxes by stimulating microbial processes but not plant growth, whereas a small number of large events will increase aboveground NPP and soil respiration by providing sufficient deep soil moisture to sustain plant growth for longer periods of time during the summer monsoon.

Core Areas: 

Data set ID: 

304

Keywords: 

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

Soil temperature is measured with Campbell Scientific CS107 temperature probes buried at 2 and 8 cm In the soil. Soil volume water content, measured with Campbell Scientific CS616 TDR probes is an integrated measure of soil water availability from 0-15 cm deep in the soil. Soil CO2 is measured with Vaisala GM222 solid state CO2 sensors. For each plot, soil sensors are placed under the canopy of B. eriopoda at three depths: 2, 8, and 16 cm. Measurements are recorded every 15 minutes.

CO2 fluxes are calculated using the CO2, temperature, and moisture data, along with ancillary variables following the methods of Vargas et al (2012) Global Change Biology

Values of CO2 concentration are corrected for temperature and pressure using the ideal gas law according to the manufacturer (Vaisala). We calculate soil respiration using the flux-gradient method (Vargas et al. 2010) based on Fick’s law of diffusion where the diffusivity of CO2 is corrected for temperature and pressure (Jones 1992) and calculated as a function of soil moisture, porosity and texture (Moldrup et al. 1999).

Data sources: 

sev304_mrme_soiltemp_moisture_co2_2012
sev304_mrme_soiltemp_moisture_co2_2013
sev304_mrme_soiltemp_moisture_co2_2014
sev304_mrme_soiltemp_moisture_co2_2015

Instrumentation: 

Instrument Name: Solid State Soil CO2 sensor
Manufacturer: Vaisala
Model Number: GM222

Instrument Name: Temperature Probe
Manufacturer: Campbell Scientific
Model Number: CS107

Instrument Name: Water Content Reflectometer Probe
Manufacturer: Campbell Scientific
Model Number: CS616

Additional information: 

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

Mega-Monsoon Experiment (MegaME) Vegetation Sampling Data from the Sevilleta National Wildlife Refuge, New Mexico (2014 - present)

Abstract: 

Shrub encroachment is a global phenomenon. Both the causes and consequences of shrub encroachment vary regionally and globally. In the southwestern US a common native C3 shrub species, creosotebush, has invaded millions of hectares of arid and semi-arid C4-dominated grassland. At the Sevilleta LTER site, it appears that the grassland-shrubland ecotone is relatively stable, but infill by creosotebush continues to occur.  The consequences of shrub encroachment have been and continue to be carefully documented, but the ecological drivers of shrub encroachment in the southwestern US are not well known.

One key factor that may promote shrub encroachment is grazing by domestic livestock. However, multiple environmental drivers have changed over the 150 years during which shrub expansion has occurred through the southwestern US. Temperatures are warmer, atmospheric CO2 has increased, drought and rainy cycles have occurred, and grazing pressure has decreased. From our prior research we know that prolonged drought greatly reduces the abundance of native grasses while having limited impact on the abundance of creosotebush in the grass-shrub ecotone. So once established, creosotebush populations are persistent and resistant to climate cycles. We also know that creosotebush seedlings tend to appear primarily when rainfall during the summer monsoon is well above average. However, high rainfall years also stimulate the growth of the dominant grasses creating a competitive environment that may not favor seedling establishment and survival. The purpose of the Mega-Monsoon Experiment (MegaME) is twofold. First, this experiment will determine if high rainfall years coupled with (simulated) grazing promote the establishment and growth of creosotebush seedlings in the grassland-shrubland ecotone at Sevilleta, thus promoting infill and expansion of creosotebush into native grassland. Second, MegaME will determine if a sequence of wet summer monsoons will promote the establishment and growth of native C4 grasses in areas where creosotebush is now dominant, thus demonstrating that high rainfall and dispersal limitation prevent grassland expansion into creosotebush shrubland. 

Data set ID: 

259

Core Areas: 

Additional Project roles: 

499
500
501
502

Keywords: 

Methods: 

Data Collection 

Vegetation and soil measurements are taken in the spring and fall each year. Spring measurements are taken in May when spring annuals have reached peak biomass for the growing season. Fall measurements are taken in either September or October when summer annuals and all perennial species have reached peak biomass for the growing season, but prior to killing frosts. Vegetation cover is measured to assess growth and survival of grasses and shrubs. Bare soil and litter covers are also measured to monitor substrate changes that occur within the plots.

One meter2 vegetation quadrats are used to measure the cover of all plants present in each m2.   There are 10 quads in each plot, checkered along on side of the plot.  There is a tag on one rebar of each quad with the representative quad number.  


General vegetation measurements 

The cover is recorded for each species of live plant material inside the quadrat.  Vegetation measurements are taken in two layers: a ground level layer that includes all grasses, forbs, sub-shrubs, and a litter 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 dead plant covers are not included in the measurement, thus the total amount may not equal 100%.  It is assumed that the remaining cover missing from the 100% is a combination of dead plant material.

 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%.


Vegetation cover measurements 

Cover measurements are made by summing the live 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% and 10.00% should be rounded to increments of 1.0, and values > 10.00% are rounded to increments of 5.

Creosote 

Larrea tridentata canopy  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).  ForLarrea seedlings the code LSEED is used and is a separate measurement from the Larrea canopy measurements. The cover measurement for LSEED is simply a count of individuals, not actual cover, as it is assumed that they would have a cover of < 1.00%.

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. 

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.

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 a seedling’s cover is less, round up to 0.1%.


Non-Vegetation cover measurements 

Materials other than vegetation that are measured in the drought plots include soil and litter.  

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.  Cover values < 10.00% should be rounded to increments of  and cover values > 10.00% 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 “0” for cover.

Litter 

Measure the cover of the area occupied by litter, which is unattached dead plant material.  Cover is quantified by summing the number of 10cm x 10cm squares intercepted by abiotic substrates. Cover values < 10.00% should be rounded to increments of 1 and cover values > 10.00% should be recorded in increments of 5.  If there is no litter in the quadrat, record “LITT” in the species column for that quadrat and record a “0” for cover.


Clipping grass at Ecotone Site 

After measurements are taken at the Ecotone Site, grass is clipped down to the soil and removed from half of the quads in each plot. The goal is to assess the impact of competition on successful creosote seedling germination. The following quads, # 2, 4, 6, 7, and 10, get clipped in every plot at the ecotone site.


Water Addition 

The watering schedule varies based on seasonal rainfall. Our goal is to increase average monsoon precipitation (150mm) by 50%, so we shoot for a total of 225mm on the plots during the summer monsoon.

Data sources: 

sev259_megame_20161222.csv

Additional information: 

Additional Information on the personnel associated with the Data Collection:

Stephanie Baker 2014-present

Megan McClung 2014-present

Chandra Tucker 2014-present

Ecosystem-Scale Rainfall Manipulation in a Piñon-Juniper Forest at the Sevilleta National Wildlife Refuge, New Mexico: Meteorological Data (2006-2013)

Abstract: 

Climate models predict that water limited regions around the world will become drier and warmer in the near future, including southwestern North America. We developed a large-scale experimental system that allows testing of the ecosystem impacts of precipitation changes. Four treatments were applied to 1600 m2 plots (40 m × 40 m), each with three replicates in a piñon pine (Pinus edulis) and juniper (Juniper monosperma) ecosystem. These species have extensive root systems, requiring large-scale manipulation to effectively alter soil water availability.  Treatments consisted of: 1) irrigation plots that receive supplemental water additions, 2) drought plots that receive 55% of ambient rainfall, 3) cover-control plots that receive ambient precipitation, but allow determination of treatment infrastructure artifacts, and 4) ambient control plots. Our drought structures effectively reduced soil water potential and volumetric water content compared to the ambient, cover-control, and water addition plots. Drought and cover control plots experienced an average increase in maximum soil and air temperature at ground level of 1-4° C during the growing season compared to ambient plots, and concurrent short-term diurnal increases in maximum air temperature were also observed directly above and below plastic structures. Our drought and irrigation treatments significantly influenced tree predawn water potential, sap-flow, and net photosynthesis, with drought treatment trees exhibiting significant decreases in physiological function compared to ambient and irrigated trees. Supplemental irrigation resulted in a significant increase in both plant water potential and xylem sap-flow compared to trees in the other treatments. This experimental design effectively allows manipulation of plant water stress at the ecosystem scale, permits a wide range of drought conditions, and provides prolonged drought conditions comparable to historical droughts in the past – drought events for which wide-spread mortality in both these species was observed.

A micrometeorological station was used to document the climatic conditions at the study site.  Monitoring the ambient environment in this way allowed us to more easily determine which tree growth responses were driven by changes in the native climate as opposed to those resulting from the rainfall manipulation treatments.  Environmental factors such as temperature, relative humidity, and photosynthetically active radiation (PAR) have a huge impact on the physiological processes that are being explored in this project.  The data collected by the station created a local climatic record which was needed to provide the context in which the treatment effects can be examined and sensor readings can be interpreted.

Data set ID: 

273

Additional Project roles: 

367

Core Areas: 

Keywords: 

Methods: 

A CR-10X datalogger was used to record data from a micrometeorological tower centrally located in an open intercanopy area of the study site. This tower recorded precipitation with a Series 525 rain gauge (Texas Electronics, Dallas, TX), net radiation with a Kipp and Zonen NK-LITE net radiometer (Campbell Scientific, Logan, UT), photosynthetically active radiation (PAR) with a LI-190SA sensor (Li-Cor, Lincoln, NE), windspeed and direction monitored with a 05103-L R.M. Young wind monitor (Campbell Scientific, Logan, UT), and air temperature and RH% with a Vaisala HMP45C sensor. During winter months the rain gauge was fitted with a snow adaptor to thaw snow and record the total amount in mm rain. All met-station measurements were made at a height of 1-3 m above ground depending on the sensor array in question. 

Data sources: 

sev273_pjmet_20130508.csv

Developing an understanding of vegetation change and fluvial carbon fluxes in semi-arid environments: Soil moisture data

Abstract: 

Dryland environments are estimated to cover around 40% of the global land surface, and are home to approximately 2.4 billion people. Many of these areas have recently experienced extensive land degradation. This study focuses on semi-arid areas in the US Southwest, where degradation over the past 150 years has been characterized by the invasion of woody vegetation into areas previously dominated by grasslands. This vegetation change has been associated with increases in soil erosion and water quality problems, including the loss of key nutrients such as carbon from the soil to adjacent fluvial systems. Such loss of resources may impact heavily upon the amount of carbon that is lost as the land becomes more heavily degraded. 

Therefore, understanding these vegetation transitions is significant both for sustainable land use and global biogeochemical cycling. This study uses an ecohydrological approach to develop an understanding of the relationship between structure and function across these transitions. This is done via the monitoring of rainfall-runoff events across instrumented runoff plots with different vegetation characteristics to investigate fluvial sediment fluxes during intense summer monsoon season rainfall events.

Data set ID: 

252

Core Areas: 

Additional Project roles: 

49

Keywords: 

Methods: 

Experimental design:

Each study area consisted of a 10m wide, 30m long, downslope runoff plot, bound at the top and sides with aluminum flashing and fitted with water collecting guttering at the bottom so inputs and outputs could be quantified. The guttering fed water into a flume fixed into the ground at 4⁰ allowing water leaving the plot as runoff to be quantified.

The flumes were instrumented with a pump sampler to collect runoff samples leaving the plot and a bubbler module to measure discharge. In addition all runoff and associated sediment was collected in a covered stock tank (560 gallons for study area 1&2, 1000 gallons for study are 3). Rainfall onto the plot was measured using tipping-bucket rain gauges connected to the pump sampler. Following rainfall events all data was downloaded from the sampler using Flowlink v3.2 software.

Eroded sediment was collected from stock tank following rainfall events, coarse organic matter was removed via flotation, samples were oven dried at 60⁰C, weighed and sieved for particle size analysis using US. standard sieves at the Sevilleta LTER field station.

Setting up plots:

Plots were selected on comparable planar slopes in areas believed to be representative of endmember vegetation habitats.

Instrumentation: 

Instrument Name: Pump samplers fitted with bubbler modules

Manufacturer: ISCO

Model Number: Model 6700 pump samplers and attached model 730 bubbler modules

Instrument Name: Tipping-bucket rain gauges

Manufacturer: ISCO

Model Number: 674

Instrument Name: Flowlink software

Manufacturer: ISCO

Model Number: Version 3.2

Instrument Name: Sieve set and shaker

Manufacturer: unknown/various (from Sevilleta LTER field station)

Model Number: US. Standard: 12mm, 4mm, 2mm, 1mm, 0.5mm, 0.063mm

Additional information: 

This data was collected and analyzed by Alan Puttock as part of the PhD project: ‘Developing an understanding of vegetation change and fluvial carbon fluxes in semi-arid environments’. This project is supervised by Dr Richard Brazier, Dr Jenifer Dungait and Dr Kit Macleod. Analysis of samples/data is being carried out at the University of Exeter and North Wyke Research, United Kingdom.

This data was collected under USFWS permit number: 22522 10-026

 
Study Area 1:  
Study Area Name: Grass Endmember Plot
Study Area Location: Five Points Grass core site (exact point location of plot provided below)
Single Point:  
North Coordinate: 34.339186     
West Coordinate: -106.728303
Study Area 2:  
Study Area Name: Creosote Endmember plot
Study Area Location: Five Points Creosote core site (exact point location of plot provided below)
Single Point:  
North Coordinate: 34.338443
West Coordinate: -106.738020
Study Area 3:  
Study Area Name: Piñon-Juniper Endmember Plot
Study Area Location: Cerro Montoso core site (exact point location of plot provided below)
Single Point:  
North Coordinate: 34.231197
West Coordinate: -106.313741

Comparative Hydraulic Performance of Piñon and Juniper in a Rainfall Manipulation Experiment at the Sevilleta National Wildlife Refuge, New Mexico

Abstract: 

From 2000-2003, extreme drought  across the Southwestern US resulted in widespread tree mortality: piñon pine (Pinus edulis) experienced up to 95% mortality while juniper (Juniperus monosperma) mortality was 25% or less at surveyed sites.  Field data have shown repeatedly that piñon typically exhibits isohydric regulation of leaf water potential, maintaining relatively constant leaf water potentials even as soil water potentials fluctuate, while juniper is anisohydric, allowing leaf water potential to decline during drought.  The goal of this study was to elucidate functional consequences of these two contrasting hydraulic strategies.  The study was conducted in the context of a rainfall manipulation experiment in piñon-juniper woodland at the Sevilleta National Wildlife Refuge and LTER in central New Mexico, USA, sampling trees in irrigation (~150% ambient rainfall), drought (50% ambient), cover control (ambient rainfall with similar drought infrastructure) and ambient control plots.  To quantify tissue and shoot level hydraulic performances we measured sapwood area-specific (KS, kg•m-1•s-1•MPa-1) and leaf area-specific (KL, g•m-1•s-1•MPa-1) hydraulic conductivity in similar sized distal branches, and we calculated AS:AL (sapwood area to leaf area ratio) to compare shoot level allocation.

Samples collected at predawn and midday both exhibited significant trends between species and across treatments.  Between species, juniper possessed significantly higher KS compared to piñon in all plots except irrigation, and higher KL than piñon in all plots.  Across treatments, irrigated juniper exhibited higher KS and KL relative to ambient and droughted plants, while irrigated piñon exhibited higher KS relative to ambient, drought and cover control plants, and irrigated and ambient piñon had higher KL than droughted and cover control plants.  Junipers did not modify AS:AL across treatments, while irrigated piñon had significantly lower AS:AL compared to all other plots.  Thus, under current climatic conditions in the Sevilleta, piñon and juniper achieve similar shoot hydraulic performances, but through different strategies: juniper maximizes xylem conductivity, while piñon maximizes xylem supply to leaves.  If climate change in the Southwest results in increased aridity, piñon could be vulnerable to extirpation from its current distribution in lower elevation PJ woodlands, as juniper demonstrates superior hydraulic capability at both the tissue and shoot level under drought conditions.

 

Core Areas: 

Data set ID: 

255

Keywords: 

Methods: 

Shoot ΨW

One shoot from each target tree was harvested between 0430-0545h and between 1200-1400h, to get predawn and midday water potential (referred to hereafter as ΨPD and ΨMD, respectively). Samples were placed in plastic bags containing a small segment of moist paper towel to prevent further dessication, which were placed in coolers out of direct sunlight in the interim time between collection and processing (between 15-60 minutes). Water potential (ΨW) [u1]was measured using a pressure chamber (PMS, Corvallis, OR).

Stem Hydraulics

After ΨW was measured, shoots were placed in humid plastic bags and allowed to equilibrate for 24 hours in a refrigerator.  Shoots were then trimmed underwater to remove peripheral embolized tissue and inserted into a steady state flow meter to measure hydraulic conductivity, Kh, kg•m-1•s-1•MPa-1 (see Hudson et al. 2010 for a full explanation of method).  In brief, the steady state flowmeter operates on the Ohm’s Law analogy of hydraulic transport (Tyree 1997), and solves for Kh by knowing the pressure gradient and the flow rate of sap surrogate (20 mM KCl, Zwieniecki et al. 2001) through the flowmeter, and measuring the pressure drop across the sample stem segment.  Hydraulic conductivity was calculated as flow through the sample segment divided by the pressure gradient across the sample segment. Sapwood cross-sections and distal leaf areas were measured for each sample to normalize Kh at tissue level (KS, sapwood area specific hydraulic conductivity, kg•m-1•s-1•MPa-1) and shoot level (KL, leaf area specific hydraulic conductivity, g•m-1•s-1•MPa-1). AS:AL was calculated for each species by dividing each sample’s sapwood area by distal leaf area.


Instrumentation: 

Instrument Name: Pressure Chamber    

Manufacturer: PMS Instrument Company    

Model Number: 1505D    


Instrument Name:  Gage model pressure transducer (0-15 psig range)    

Manufacturer:  Omega Engineering, INC.

Model number: PX26-015GV

Effects of Rainfall Manipulation on the Lizard Community in a Piñon-Juniper Woodland at the Sevilleta National Wildlife Refuge, New Mexico

Abstract: 

We surveyed lizards in the pinon-juniper rainfall manipulation plots to investigate whether altered rainfall has an influence on lizard abundance. 

Data set ID: 

249

Core Areas: 

Keywords: 

Methods: 

We conducted visual encounter surveys within Dr. Pockman’s rainfall manipulation plots.  This method involved walking through the plots and scanning the ground for lizards.  We used a pair of binoculars to observe lizards at a distance and for species identification.  We then marked a GPS waypoint for each lizard observed and recorded the animals behavior.  For each survey we recorded time and distance walked during each plot we surveyed.

Developing an Understanding of Vegetation Change and Fluvial Carbon Fluxes in Semi-Arid Environments at the Sevilleta National Wildlife Refuge, New Mexico: Characterization Data

Abstract: 

Dryland environments are estimated to cover around 40% of the global land surface, and are home to approximately 2.4 billion people. Many of these areas have recently experienced extensive land degradation. This study focuses on semi-arid areas in the US Southwest, where degradation over the past 150 years has been characterized by the invasion of woody vegetation into areas previously dominated by grasslands. This vegetation change has been associated with increases in soil erosion and water quality problems, including the loss of key nutrients such as carbon from the soil to adjacent fluvial systems. Such loss of resources may impact heavily upon the amount of carbon that is lost as the land becomes more heavily degraded.

Therefore, understanding these vegetation transitions is significant both for sustainable land use and global biogeochemical cycling. This study uses an ecohydrological approach to develop an understanding of the relationship between structure and function across these transitions. This is done via the monitoring of rainfall-runoff events across instrumented runoff plots with different vegetation characteristics to investigate fluvial sediment fluxes during intense summer monsoon season rainfall events.

Data set ID: 

251

Core Areas: 

Additional Project roles: 

48

Keywords: 

Methods: 

Experimental design: 

Each study area consisted of a 10m wide, 30m long, downslope runoff plot, bound at the top and sides with aluminum flashing and fitted with water collecting guttering at the bottom so inputs and outputs could be quantified. The guttering fed water into a flume fixed into the ground at 4⁰ allowing water leaving the plot as runoff to be quantified.

The flumes were instrumented with a pump sampler to collect runoff samples leaving the plot and a bubbler module to measure discharge. In addition all runoff and associated sediment was collected in a covered stock tank (560 gallons for study area 1&2, 1000 gallons for study are 3). Rainfall onto the plot was measured using tipping-bucket rain gauges connected to the pump sampler. Following rainfall events all data was downloaded from the sampler using Flowlink v3.2 software.

Eroded sediment was collected from stock tank following rainfall events, coarse organic matter was removed via flotation, samples were oven dried at 60⁰C, weighed and sieved for particle size analysis using US. standard sieves at the Sevilleta LTER field station.

Setting up plots: 

Plots were selected on comparable planar slopes in areas believed to be representative of endmember vegetation habitats.  

Instrumentation: 

Instrument Name: Pump samplers fitted with bubbler modules

Manufacturer: ISCO

Model Number: Model 6700 pump samplers and attached model 730 bubbler modules

Instrument Name: Tipping-bucket rain gauges

Manufacturer: ISCO

Model Number: 674

Instrument Name: Flowlink software

Manufacturer: ISCO

Model Number: Version 3.2

Instrument Name: Sieve set and shaker

Manufacturer: unknown/various (from Sevilleta LTER field station)

Model Number: US. Standard: 12mm, 4mm, 2mm, 1mm, 0.5mm, 0.063mm

Additional information: 

This data was collected and analyzed by Alan Puttock as part of the PhD project: ‘Developing an understanding of vegetation change and fluvial carbon fluxes in semi-arid environments’. This project is supervised by Dr Richard Brazier, Dr Jenifer Dungait and Dr Kit Macleod. Analysis of samples/data is being carried out at the University of Exeter and North Wyke Research, United Kingdom.

This data was collected under USFWS permit number: 22522 10-026


Study Area 1:  
Study Area Name: Grass Endmember Plot
Study Area Location: Five Points Grass core site (exact point location of plot provided below)
Single Point:  
North Coordinate: 34.339186     
West Coordinate: -106.728303
Study Area 2:  
Study Area Name: Creosote Endmember plot
Study Area Location: Five Points Creosote core site (exact point location of plot provided below)
Single Point:  
North Coordinate: 34.338443
West Coordinate: -106.738020
Study Area 3:  
Study Area Name: Piñon-Juniper Endmember Plot
Study Area Location: Cerro Montoso core site (exact point location of plot provided below)
Single Point:  
North Coordinate: 34.231197
West Coordinate: -106.313741

Developing an Understanding of Vegetation Change and Fluvial Carbon Fluxes in Semi-Arid Environments at the Sevilleta National Wildlife Refuge, New Mexico: Rainfall Runoff Events

Abstract: 

Dryland environments are estimated to cover around 40% of the global land surface, and are home to approximately 2.4 billion people. Many of these areas have recently experienced extensive land degradation. This study focuses on semi-arid areas in the US Southwest, where degradation over the past 150 years has been characterized by the invasion of woody vegetation into areas previously dominated by grasslands. This vegetation change has been associated with increases in soil erosion and water quality problems, including the loss of key nutrients such as carbon from the soil to adjacent fluvial systems. Such loss of resources may impact heavily upon the amount of carbon that is lost as the land becomes more heavily degraded.

Therefore, understanding these vegetation transitions is significant both for sustainable land use and global biogeochemical cycling. This study uses an ecohydrological approach to develop an understanding of the relationship between structure and function across these transitions. This is done via the monitoring of rainfall-runoff events across instrumented runoff plots with different vegetation characteristics to investigate fluvial sediment fluxes during intense summer monsoon season rainfall events.

Data set ID: 

247

Core Areas: 

Additional Project roles: 

47

Keywords: 

Methods: 

Experimental design: 

Each study area consisted of a 10m wide, 30m long, downslope runoff plot, bound at the top and sides with aluminum flashing and fitted with water collecting guttering at the bottom so inputs and outputs could be quantified. The guttering fed water into a flume fixed into the ground at 4⁰ allowing water leaving the plot as runoff to be quantified.

The flumes were instrumented with a pump sampler to collect runoff samples leaving the plot and a bubbler module to measure discharge. In addition all runoff and associated sediment was collected in a covered stock tank (560 gallons for study area 1&2, 1000 gallons for study are 3). Rainfall onto the plot was measured using tipping-bucket rain gauges connected to the pump sampler. Following rainfall events all data was downloaded from the sampler using Flowlink v3.2 software.

Eroded sediment was collected from stock tank following rainfall events, coarse organic matter was removed via flotation, samples were oven dried at 60⁰C, weighed and sieved for particle size analysis using US. standard sieves at the Sevilleta LTER field station.

Setting up plots: 

Plots were selected on comparable planar slopes in areas believed to be representative of endmember vegetation habitats.  

Instrumentation: 

Instrument Name: Pump samplers fitted with bubbler modules

Manufacturer: ISCO

Model Number: Model 6700 pump samplers and attached model 730 bubbler modules

Instrument Name: Tipping-bucket rain gauges

Manufacturer: ISCO

Model Number: 674

Instrument Name: Flowlink software

Manufacturer: ISCO

Model Number: Version 3.2

Instrument Name: Sieve set and shaker

Manufacturer: unknown/various (from Sevilleta LTER field station)

Model Number: US. Standard: 12mm, 4mm, 2mm, 1mm, 0.5mm, 0.063mm

Additional information: 

This data was collected and analyzed by Alan Puttock as part of the PhD project: ‘Developing an understanding of vegetation change and fluvial carbon fluxes in semi-arid environments’. This project is supervised by Dr Richard Brazier, Dr Jenifer Dungait and Dr Kit Macleod. Analysis of samples/data is being carried out at the University of Exeter and North Wyke Research, United Kingdom.

This data was collected under USFWS permit number: 22522 10-026

Study Area 1:  
Study Area Name: Grass Endmember Plot
Study Area Location: Five Points Grass core site (exact point location of plot provided below)
Single Point:  
North Coordinate: 34.339186     
West Coordinate: -106.728303
Study Area 2:  
Study Area Name: Creosote Endmember plot
Study Area Location: Five Points Creosote core site (exact point location of plot provided below)
Single Point:  
North Coordinate: 34.338443
West Coordinate: -106.738020 
Study Area 3:  
Study Area Name: Piñon-Juniper Endmember Plot
Study Area Location: Cerro Montoso core site (exact point location of plot provided below)
Single Point:  
North Coordinate: 34.231197
West Coordinate: -106.313741

Soil microbial response to altered precipitation regimes at the Sevilleta National Wildlife Refuge, New Mexico

Abstract: 

Microbes substantially control many biogeochemical processes in semiarid systems, including carbon and nitrogen fixation and carbon mineralization. Bacteria and fungi are osmotrophs that release enzymes into the environment to generate assimilable carbon and nutrients from organic particles. These enzymes are also the first agents to respond to pulses of soil moisture. The capacity to stabilize extracellular enzymes on soil particles preserves the utility of these nutrient-generating agents during extended dry periods. Enzyme stability can relate to environmental conditions and increase with clay mineral and humic compound concentrations. To better understand microbial response to precipitation variability, our objective was to determine the stability of extracellular enzymes under various monsoon precipitation regimes. During summer 2010, soil enzyme activity was measured in a rainfall manipulation study within a mixed-grass semiarid grassland in New Mexico, USA. Plots received either one large rain event or three evenly spaced small rain events per month. Before and after the first rain of each month, soil samples from the rhizosphere and from interspaces between plants were collected and analyzed for activity of four hydrolases; beta-glucosidase, beta-N-acetylglucosaminidase, leucine aminopeptidase, and alkaline phosphatase. 

Additional Project roles: 

303

Data set ID: 

245

Core Areas: 

Keywords: 

Methods: 

For experimental design and precipitation manipulations see SEV218.

Before the first rain of each month, soil samples were collected from the rhizosphere and interspaces between plants. Four soil cores (1cm wide, 3 cm deep) were taken across the plot, with rhizoshpere samples from under B. eriopoda and B. gracilis, and mixed together for each sample. Enzyme activity in the rhizosphere and interspace were analyzed separately. Two hours after the rain event, soil samples were again collected in the same manner. Microbial response to precipitation is quick therefore 2 hours was ample time to assess microbial response. Samples were refrigerated and processed within 48 hours of collection to prevent enzyme degradation. Soils were subsampled for organic matter and water content. Field soil moisture was calculated by comparing weights of freshly collected soil and soil dried at 60 °C. A subsample was also burned at 500 °C for 4 hours to determine percent organic matter. The potential activity levels of beta-glucosidase, beta-N-acetylglucosaminidase, leucine aminopeptidase, alkaline phosphatase, and phenol oxidase were measured in the lab following the methods of Stursova et al. (2006).

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