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Warming and snow experiment plant reproductive and growth data for Saddle, 1993 - 1996.

The International Tundra Experiment (ITEX) is a consortium of research sites seeking to understand the response of tundra plant populations to changes in growing season temperatures through a simple temperature manipulation and transplant experiment. The research goal is to examine the phenologic and reproductive responses of a set of species to experimentally-induced warming at a network of sites. The ITEX design is hierarchical, with sites participating at whatever level they are able. At the minimum, participation in ITEX requires climate monitoring (using the LTER MSR standards), a temperature manipulation using one of three possible designs, and monitoring phenologic and reproductive variables for at least one designated ITEX species or two other species. The temperature manipulation is achieved through use of conical or hexagonal open-top chambers of solar fiberglass, which have been shown to increase the air temperature at the surface approximately 3 degrees C. ITEX studies at Niwot Ridge, a logical outgrowth of the long-term phenology studies there, uses a factorial design based around the long-term snowfence experiment. Twenty cones are placed behind the snowfence, distributed at 10, 25, 45, and 75 m from the fence; each cone is paired with an adjacent plot. Beginning with the 1995 season, 24 additional plots were implemented outside of the snowfence influence. Twelve cones are distributed beyond both the north and south edges of the snowfence area, at 10, 25, 45, and 75 m behind the line of the snowfence; each cone is paired with an adjacent plot. This results in the following treatments: increased winter snow, increased summer temperature, increased snow and increased temperature, and control. Key phenologic, growth, and reproductive traits are being followed on marked individuals of Acomastylis (Geum) rossii and Bistorta (Polygonum) bistortoides, and complete species composition is being monitored.

openCC (other)Feb 2019View details →

Groundwater well chemistry data for Niwot Saddle, C1 and Martinelli, 2005 - ongoing.

This is a summary of major ion concentrations and chemistry data for groundwater samples collected at groundwater wells on the Niwot saddle, C1 site and Martinelli site.

openCC (other)Apr 2021View details →

Infilled climate data for C1, Saddle, and D1, 1990 - 2019, hourly.

This serially complete dataset includes hourly, quality-controlled, infilled meteorological data for three sites at the Niwot Ridge LTER: C1, Saddle, and D1, representing subalpine, alpine, and high-alpine environments, respectively. Raw observations of air temperature, relative humidity, wind speed, and incoming shortwave radiation were subjected to a rigorous hierarchical quality control and infilling protocol to make a robust, continuous dataset. Incoming longwave radiation was estimated using air temperature, relative humidity, and incoming shortwave radiation. Precipitation data were accessed from the Niwot Ridge LTER quality controlled datasets and Kittel et al. (2015). Precipitation values from C1 and Saddle were then corrected for gage undercatch (C1) and overcatch (Saddle) based on observations of snow accumulation at the Niwot SNOTEL station and snow pits located near the met stations (D1 precipitation data were not corrected as there were no available observation of snow accumulation). Daily precipitation values were temporally disaggregated to the hourly time step of the dataset. This dataset was originally created to force a physics-base snow model and is suitable for use in other research models that require hourly forcing data. Please contact the dataset's creators or the LTER data manager if you have any questions regarding the data or its applicability/suitability to your project. Disclaimer: These data come as-is with no warranty. The user must decide whether or not to use different variables and time periods within the dataset and whether further processing is warranted. In general, the data quality is higher and there are fewer infilled values from 2000 to 2013. The higher number of infilled entries before 2000 may preclude the 1990–1999 period from being used in a given analysis. This is particularly true for relative humidity and incoming solar radiation. The Niwot Ridge LTER is not responsible for the methodological choices made by those using

openCC (other)Apr 2019View details →

N fertilization experiment plant species composition data for north of the saddle from 2011 to ongoing, yearly

In August 2010, N fertilization plots were established over a gradient of Geum rossii (Aco) and Deschampsia caespitosa (Des) cover in an area of moist-wet meadow alpine tundra north of the Saddle on Niwot Ridge. A total of 20 plots were set up, with 1X-10X being control plots where no nitrogen (N) was added, and 1N-10N being fertilization plots where N was added. Control and fertilized plots were paired so that pairs had the same percent cover of Aco and Des. Initially in 2010, N addition plots were fertilized at a rate of 28.8 g N x m^2 x yr^-1 (72 g of slow-release Osmocote (40-0-0)). In 2011 fertilization rate was reduced to N x m^2 x yr^-1 (25 g Osmocote (2011-2013), Duration Urea 120, 40-0-0, SGN 150 (2014-on).

openCC (other)May 2019View details →

Microclimate data for Saddle grid, 1993, daily.

The objective of this field campaign was to measure microclimatic variables within a mid-latitude alpine tundra zone during the growing season (June - August), and to relate those observations to ecosystem processes and landscape patterns. Microclimatic data were recorded using a Campbell CR21X micrologger on or near the Niwot Ridge Saddle grid. Five sites were chosen (2 of which were snow covered and the remaining 3 being snowfree tundra). Measurements were made at 60-second intervals and averaged on the half hour. These half-hourly data were subsequently averaged for the day. All meteorological instruments on the tower were oriented parallel to the surface at the tower location. The anemometer was located at the top of the meteorological station tower (i.e., 3 m above the surface). The air temperature and relative humidity probe were 2 m above the surface. The pyranometer used for the calculation of incoming solar radiation was 1.5 m above the surface. The pyranometer used for the calculation of outgoing solar radiation was 1.25 m above the surface. The net radiometer was situated between 0.75 and 1 m above the surface. The heat flux transducer was located 5 cm below the surface of the vegetation canopy. The soil temperature probe was located between 0 and 10 cm below the ground surface.

Microclimate data for Saddle grid, 1993, half-hourly.

Spectral radiation data for Saddle grid, 1994.

During the summer of 1992 10-m transects were established at each of the Niwot Ridge Saddle grid points, with the exception of grid points 1, 13, 30A, 37, 41, 42, 63, and 71. No transects were set up at those locations because they were essentially barren of vegetation or, in the case of grid point 37, were covered with a willow shrub thicket. Transect locations were chosen so that the vegetation along the transect would be consistent with that in the 1x1-m plot used to characterize the species composition at the corresponding Saddle grid point. These transects were established as part of a study designed to quantify any relationship between spectral emissivity and net primary productivity. Spectral measurements were made, using a PS-II (Analytical Spectral Devices) spectrometer, of approximately 50- x 20-cm plots along a transect immediately prior to it being clip harvested for aboveground biomass determinations. Photographs were taken at the same time that the spectral measurements were made in 1994, but at different times in 1993. The photographs were subsequently used to quantify various cover classes for the harvested portion of the transect. The relationships between these cover classes and vegetation indices derived from the spectral data were explored.

Cover class data for Saddle grid, 1993 - 1994.

During the summer of 1992 10-m transects were established at each of the Niwot Ridge Saddle grid points, except grid points 1, 5, 13, 15, 25, 30A, 35, 37, 41, 42, 45, 46, 55, 63, 65, and 71. No transects were set up at locations 1, 13, 30A, 41, 42, 63, and 71 because they were essentially barren of vegetation or, in the case of grid point 37, were covered with a willow shrub thicket. Transect locations were chosen so that the vegetation along the transect would be consistent with that in the 1x1-m plot used to characterize the species composition at the corresponding Saddle grid point. These transects were established as part of a study designed to quantify any relationship between spectral emissivity and net primary productivity. Spectral measurements were made, using a PS-II (Analytical Spectral Devices) spectrometer, of approximately 50- x 20-cm plots along a transect immediately prior to it being clip harvested for aboveground biomass determinations. Photographs were taken at the same time that the spectral measurements were made in 1994, but at different times in 1993. The photographs were subsequently used to quantify various cover classes for the harvested portion of the transect.

Normalized difference vegetation index data for Saddle snowfence, 1994.

A snowfence was built in 1993 on the Niwot Ridge Saddle grid to determine the effects of changes in snowpack on a number of variables, one of which was vegetation greenness (measured through the normalized difference vegetation index). The study area of the snowfence was 60m x 125m. Spectral data in the red and near infra- red bands were recorded at sixty plots (points) in four rows located approximately at 10, 25, 45, and 75 meters east of the fence (the drift area). The plots were marked with thin wire stakes put into the ground and flagged (for visibility) and given aluminum tags with their plot identification code. All the plots were located in Kobresia myosuroides communities. In each row there were ten plots located in control areas just to the north and south of the area affected by the snowfence -- five to the north and five to the south -- and five plots located in the drift area of the snowfence. The individual plots were broken into groups of five according to their location (i.e., their distance from the fence (row), and location within their row (north, south, or within the snowfence area)). Within each of these groups, the plots were given a number starting with one and going to five. The plots were then given unique codes made up of plot type (c for control and sf for snowfence), location within a row (for the control plots only - n for north and s for south), the distance in meters of the row from the snowfence (10, 25, 45, or 75), and the number that uniquely identifies each plot within a group (one through five). For example, the code cn10_1 represents plot number one of the group of control plots north of the snowfence and 10 meters east of the snowfence. The location of each plot was measured as set of coordinates within the snowfence area. The southern terminus of the snowfence was used as the origin, with the y-axis running along the snowfence and the x-axis running perpendicular to the snowfence at it's southern end. The first coordinate was t

Soil temperature data for Saddle snowfence, 1992 - 1995.

A snowfence was built in 1993 on the Niwot Ridge Saddle grid to determine the effects of changes in snowpack on a number of variables, one of which was soil temperature. The study area was 60m x 125m. Soil temperatures were measured at two depths (0 and 15 cm) at each of 13 locations within the snowfence experiment area. Soil temperatures were measured at the same depths at each of 6 control locations outside of but near the snowfence experiment area. These measurements were made weekly to biweekly using fixed thermistors and data loggers. Sampling locations were each given a unique point identification number in order that these data could be incorporated into the Saddle GIS. The snowfence was oriented in a north/south direction and was 60m long. Each of the point identification numbers had a coordinate within the experiment area. The first number of the coordinate was the distance in m from the snowfence in an east/west direction, negative numbers being west of the snowfence and positive numbers being east of the fence. The second number in the coordinate was the distance in m from the southern terminus of the snowfence in a northerly direction. The point identification numbers and coordinates were: 203 (-40,30), 217 (-30,30), 231 (-20,30), 245 (-10,30), 252 (-5,30), 259 (5,30), 266 (10,30), 281 (20,30), 295 (30,30), 309 (40,30), 323 (50,30), 337 (60,30). Controls were located outside of the snowfence experiment area: 113 (approximately 10 m south of the -30,0 coordinate) in the Acomastylidetum rossii vegetation association, 114 (approximately 11 m south of the -25,0 coordinate) in the Acomastylidetum rossii vegetation association, 115 (approximately 8 m south of the 55,0 coordinate) in the Kobresietum myosuroidis vegetation association, 116 (approximately 5 m north of the 50,60 coordinate) in the Kobresietum myosuroidis vegetation association, 117 (approximately 3 m north of the -23,60 coordinate) in the Rhodiolo integrifoliae vegetation association, 118 (approxi

Individual plant phenology data for Saddle nodal plots, 1984 - 1992.

Phenological data were collected weekly for permanently tagged plants located in 14 permanent plots (refered to as the nodal plots) in the Niwot Ridge Saddle area. 12 of the plots represent the 6 plant communities or noda (two from each nodum) identified in the Saddle (May 1973). The two remaing plots were located adjacent to two temporary snowfences erected near Saddle grid stake 49. The plots were 1x10 m, and were further divided into 10, 1x1 m quadrats. Plant species studied include Acomastylis (Geum) rossii, Bistorta (Polygonum) bistortoides and Bistorta (Polygonum) vivipara. Ten individuals of each species present in a plot were randomly selected. Plants were tagged approximately two inches behind each plant with an aluminum tag labelled with the species abbreviation and plant number. Tagged plant locations were determined using a Cartesian coordinate system with the outside corner of quadrat 1 serving as the origin. These locations are on permanent file at INSTAAR. Data collection began on 1 June, or as plots became snow free, and continued until senescence. Missing tags were replaced during the first week of data collection. Missing plants were replaced by a new plant in immediate area and the new coordinates were recorded.

openCC (other)Dec 2018View details →

Snow depth data for saddle grid, 1982 - 1990.

The depth of snow was measured at 88 points on the Saddle grid. Depths were measured form fixed extendable poles on the western or accumulation portion of the 350 x 500 m grid, while depths were measured by probing on the eastern portion. Measurements during winter months varied from every 2 weeks to about monthly depending on weather conditions. Measurements during the summer were approximately weekly until all snow disappeared or snow accumulation began for the next winter. Meltout date can be determined from the last date snow was present at a grid point. The area of the study was 19.7 ha.

Plant biomass and N content data for South of saddle, 1990 - 1991.

The data set includes biomass and nitrogen concentration data for both roots and shoots of several alpine plant species, measured at intervals through the 1990 and 1991 growing seasons. In addition, plant N pools are calculated by multiplying N concentration times biomass for both roots and shoots. Total pool sizes can be calculated by pooling the root and shoot pools. The data provide a seasonal view of the N dynamics of the alpine species tested.

Soil and microbial N data for Saddle and South of saddle, 1992.

Net nitrogen mineralization, nitrification, and microbial nitrogen were measured in dry and moist meadow plots on Niwot Ridge from early June to mid-October 1992. Dry meadow plots in the City of Boulder Watershed had been fertilized with N during the two years prior to measurements, and both dry and moist meadow plots in the Saddle were being watered and fertilized concurrent to measurements.

Soil and microbial N data for Saddle, South of saddle, North of saddle, 1993.

Gross N mineralization, respiration, and microbial biomass N were measured using soil from dry, moist, and wet meadow sites on Niwot Ridge at 3 times during the year: immediately following snowmelt, at approximately peak plant biomass, and following aboveground senescence. Microbial biomass N was measured on replicate soil cores from plots of each community, using the chloroform fumigation-extraction technique. Those cores were subsequently composited and subsamples were incubated at 15 degrees Celsius in the laboratory for measurement of CO2 evolution and 15N pool dilution-based estimations of gross mineralization.

Soil water and microbial N data for Saddle, 1993.

The effects of water, carbon (glucose), or nitrogen ((NH4)2SO4) additions on N transformations and the chloroform-labile microbial N pool were assessed in laboratory incubations of moist meadow soil collected from the T1M trace gas study plot on Niwot Ridge. These incubations were conducted at monthly intervals during the snow-free season of 1993, to detect any seasonal changes in the microbial response to different amendments. Soil respiration was measured concurrently.

Moist meadow microbial respiration data for Saddle, 1993.

The effects of C, N, and water amendments on microbial respiration were assessed at monthly intervals throughout the 1993 snow-free season in laboratory incubations of moist meadow soils collected from the T1M trace gas study plot on Niwot Ridge. Total respiration was quantified at daily intervals throughout each 10- to 12-day incubation using a base trap method.

Fine root biomass and N content data for Saddle, South of saddle, North of saddle, 1994.

Root production was estimated in dry, moist, and wet meadow communities on Niwot Ridge using a root-ingrowth core method. Columns of root-free soil were established on 1 June 1994 and were re-cored on 10 August and 23 September 1994 for measurement of fine root mass and nitrogen content.

Climate data for Saddle data logger (CR21X), 1986-2000.

Climatological data were collected from a Niwot Ridge climate station (saddle) throughout the year using a Campbell Instruments CR21X data logger. Maximum and minimum values are recorded instantaneously, with the sampling interval being 30 seconds, until 4 February 1991 at which time the sampling interval was changed to 2 seconds. Daily means and totals were calculated from 2880 individual measurements until 4 February 1991 and 43200 after that date. This instrument was programmed to generate both hourly and daily output. Parameters measured include solar radiation, air temperature, relative humidity, barometric pressure, wind speed, wind vector, and wind direction.

Climate data for Saddle chart recorder, 1981 - 1982.

Climatological data were collected from a Niwot Ridge climate station (Saddle, 3525 m) throughout the year. Parameters measured were temperature, relative humidity, solar radiation, and precipitation. Although wind speed, wind direction, and barometric pressure were originally listed as parameters for this data set, no values were actually found to be present in the data and these columns were therefore removed from the data set. The station was instrumented with a thermohygrograph (regularly calibrated and checked with maximum and minimum thermometers and psychrometers), which was equipped with a Bourdon tube (to measure temperature) and a banjo-spread hair element (to measure relative humidity). The thermohygrograph was situated in a white, all wood, louvered Stevenson screen which is oriented with the door facing north. The station was instrumented with a recording precipitation gauge. Precipitation was caught in a bucket containing ethylene glycol (to melt snow) and light oil (to prevent evaporation). As the weight of the bucket increased, a pen moved up via a spring mechanism and recorded on a rotating chart. A snow fence was placed around the gauge to give more accurate precipitation measurements during windy conditions. Solar radiation was recorded on a bimetalic strip mechanical actinometer. Ninety percent of solar radiation from 360 to 2000 nm was transmitted through the instrument's glass dome. Wind speed (peak gust) was measured with a 3-cup, AC-generating anemometer that continuously recorded onto an Esterline Angus strip chart recorder. Wind direction was recorded as a pen position on a continuously recording strip chart. The thermohygrograph, rain gauge, and actinometer all used wind-up or battery-driven clock drives that rotated the recording chart on a right cylindrical drum with a fixed period between 24 h and 861 h depending on the gears used. These clock mechanisms were virtually identical and therefore completely interchangeable among the instrum