After 2 full months plus one week the Sevilleta finally got some real
moisture. A storm on April 8th brought a significant amount of
moisture to all of the Sevilleta rain gauges. Rainfall amounts varied
from 14.3 mm (0.55") at Bronco Well to 4.5 mm (0.18") at Blue Grama.
A second storm four days later delivered greater or equal amounts.
These 2 storms combined to surpass the refuge's usual April quota. An
extendqed series of storms later in the month were predicted to provide
The Monsoon Rainfall Manipulation Experiment (MRME) is to understand changes in ecosystem structure and function of a semiarid grassland caused by increased precipitation variability, which alters the pulses of soil moisture that drive primary productivity, community composition, and ecosystem functioning. The overarching hypothesis being tested is 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. These data were collected at a meteorological station at the Monsoon Site.
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.
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).
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 change on grassland community composition and the growth of introduced creosote seeds and seedlings. The focus is on the response of three dominant species, all of which are near their range margins and thus may be particularly susceptible to 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 mineralization, precipitation), species growth (photosynthetic rates, creosote shoot elongation), 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.
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.
This file contains hourly meteorological data that were collected from a network of 10 permanent weather stations on the Sevilleta National Wildlife Refuge.
To monitor meteorological conditions across the Sevilleta and surrounding areas through time.
Stations were located across the Sevilleta and surrounding areas to cover the entire spatial and elevational extent of the refuge. They were also generally located adjacent to other pertinent study locations such as plant and animal monitoring studies.
Automated weather stations
Each weather station includes a 3 m tripod tower, on which is mounted most of the monitoring equipment. This equipment includes an enclosure housing a datalogger and power supply. On the tripod are mounted an anemometer and wind vane, a pyranometer, and a solar radiation shield that encloses a combination temperature and relative humidity sensor. Other attached sensors include: a precipitation gauge, soil temperature sensors and soil moisture potential sensors.
* Manufacturer: Campbell Scientific Inc.* Component: Datalogger - Measurement and Control Module* Model Number CR10* Reference Manuals: CR10 Measurement and Control Module Campbell Scientific Inc.* Manufacturer: Campbell Scientific Inc.Measurement Techniques: Automated weather stations Each weather station includes a 3 m tripod tower, on which is mounted most of the monitoring equipment. This equipment includes an enclosure housing a datalogger and power supply. On the tripod are mounted an anemometer and wind vane, a pyranometer, and a solar radiation shield that encloses a combination temperature and relative humidity sensor. Other attached sensors include: a precipitation gauge, soil temperature sensors and soil moisture potential sensors.* Component: Temperature/Relative Humidity Sensor* Model Number 207* Reference Manuals: * Manufacturer: Campbell Scientific Inc.* Component: Temperature/Relative Humidity Sensor* Model Number HMP45C* Reference Manuals:* Manufacturer: MET-ONE* Component: Cup Anemometer* Model Number 14A* Reference Manuals:* Manufacturer: MET-ONE* Component: Wind Vane* Model Number 24A* Reference Manuals:* Manufacturer: LI-COR* Component: Pyranometer* Model Number 200SZ* Reference Manuals:* Manufacturer: Texas Electronics* Component: Rain Gauge* Model Number TE525 mm* Reference Manuals:* Manufacturer: Campbell Scientific Inc.* Component: Soil Temperature Probe* Model Number 108* Reference Manuals: * Manufacturer: Campbell Scientific Inc.* Component: Soil Temperature Probe* Model Number 107* Reference Manuals: * Manufacturer: Campbell Scientific Inc.* Component: Soil Moisture Block * Model Number 227* Reference Manuals: * Manufacturer: Vaisala* Component: Barometer* Model PTB101B* Reference Manuals:
These data were collected from a network of 10 permanent weather stations on the Sevilleta National Wildlife Refuge. Station 40 has been in operation since the middle of 1987; Stations 41-44 were installed in the early part of 1989; Station 45 was put into operation on 26 Jan 1990 (hour 15); Station 46 was put into operation on 31 Aug 1990 (hour 17); and Station 1 was put into test operation on 29 Dec 1991 (hr 12) and official data recording started on 01 Jan 92 (hr 01). A new station (#48) was established during 1998 (on Oct 1 1998) at a site designated as Savana (initially called Blue Springs. Station 49 was installed in the Five Points area in 1999 and named Five Points. Another new station was established in 2001 at a new core study site designated as Blue Grama and given a station ID number of 50. These data have been run through a filtering program which replaces all obviously out-of-range values with -999.000's and flags questionable values for checking by data manager.
Precipitation is recognized as the most spatially variable abiotic variable in arid ecosystems such as the Sevilleta National Wildlife Refuge (NWR). Water is also usually the limiting factor in such environments so the accurate measurement of precipitation in both space and time is vital to understanding ecosystem dynamics. In 2008, the acquisition of a number of tipping-bucket rain gauges with Hobo dataloggers permitted the deployment of gauges into an increased number of locations on the Sevilleta NWR. Most dataloggers were installed in the greater Five Points area and primarily placed around the site of the 2003 burn study. A few additional dataloggers were installed throughout the entire Sevilleta NWR to expand overall coverage.
Datalogger specifications - Onset Tipping Bucket Rain gauge (8" opening); each tip records 0.01" (0.254 mm).
Data downloading - Data is collected from Hobo dataloggers using a Hobo shuttle. The data is then downloaded onto a PC computer using Boxcar Software.
01/19/11-Data and metadata compiled and updated through 2010. (JMM)03/19/10-Data and metadata compiled and updated through 2010. SEV project number assigned (SEV234) in Navicat and all data and metadata uploaded for public access. (JMM)