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N and P fertilization experiment plant phenology data for South of saddle, 1993-1994

The effects of nitrogen, phosphorus, and nitrogen+phosphorus fertilization on phenology of alpine plants was examined. This was a preliminary study to determine if the phenologies of dry meadow plants were affected by nutrient amendments, and if they were, which species responded most to the treatments. Times of emergence, senescence, and other key vegetative and reproductive "events" were recorded.

openCC (other)Oct 2019View details →

Aboveground biomass N and P content data for South of saddle, 1991.

To determine whether there are differences in the relative capacity of communities to accumulate nutrients N and P standing crops were measured following fertilization in two alpine tundra communities. Dry meadow had greater increases in aboveground N standing crop and tissue N concentration in response to N fertilization than the wet meadow. The wet meadow had a greater P accumulation response to P fertilization than the dry meadow.

openCC (other)Jan 2022View details →

Ground water well elevation for Niwot Ridge Saddle, 2012 - 2018.

Water level of Saddle Ground Water Wells. Ground Water Well locations, depths, and design were determined by Niwot Ridge LTER lead researchers, Mark Williams and Nel Caine, to monitor groundwater chemistry and water levels. Well locations were selected based on proximity to the headwater region of the Saddle stream channel. Ground Water Wells are located along an east-west transect at the Saddle site, each pair consisting of a deep well to a depth between 6.3 and 8.8 m, and a shallow well to a depth of 1.5 m. Ground surface elevations at the Saddle wells range from about 3522 m at the eastern wells to 3532 m at the western wells. The transect is roughly 170 m from east to west, has an average slope of 0.06, and is perpendicular to the Saddle stream. Saddle pair 3 was installed very close to the channel. Saddle pairs 2 and 4 were installed on opposite sides of the channel. Saddle pair 1 was installed furthest from the channel (King, 2012). Ground water wells were installed in October 2005 by Bandimere Geothermal Drilling Systems. Wells are cased with 2-inch nominal pipe size, Schedule 40 polyvinyl chloride (PVC), flush-threaded pipe. Well screens were constructed from 0.020-inch continuous slot PVC and installed in 5-ft (1.52 m) intervals. All of the wells have 1.52 m screens at the bottom of the well. The bottoms of the wells were capped with a PVC flush-threaded point cap. The annular space around each screen and pipe was backfilled with #10-20 silica sand to act as a filter (King, 2012). The Niwot Ridge LTER monitoring of these Ground Water Wells has varied over the years since the wells were installed. Prior to 2014, all wells were sampled weekly in summer and monthly in winter for chemistry, and alternating wells were monitored for water level with pressure transducers and a weighted tape measure. From 2015 through present, Saddle Deep 3 (SD3) and Saddle Deep 4 (SD4)- those located closest to the Saddle Stream headwaters- are being monitored for water level, wat

openCC (other)May 2022View details →

Saddle catchment Distributed Hydrology Soil Vegetation Model Simulation (DHSVM) surface variable outputs (SWE, snowmelt, streamflow, soil moisture), 2 meter, 2000-2019.

The Saddle Catchment of the Niwot Ridge LTER is a densely observed, high elevation site that is ideal for hydrological model simulation and calibration. The files produced are the result of a calibration of the Distributed Hydrology Soil Vegetation model (DHSVM) using observationally based states and forcings. Input state files of vegetation, soil properties, shading, and elevation were generated using ground and satellite observations, which, in the case of coarse-resolution or point scale observations, were then interpolated to match the high resolution of the model (2-meter grid cells). Temporally continuous meteorological forcings at the hourly time-step were used to force the model to produce an hourly simulation of the surface and subsurface hydrology within the Saddle catchment. DHSVM was calibrated to effectively reproduce the annual cycle (r^2) and total volume (percent bias) of observed runoff using observations of streamflow at the outflow pour point of the Saddle Catchment from 2001-2019. Calibrated parameters include the lateral conductivity of soil types, exponential decrease of soil conductivity, snow roughness, the snow melting temperature threshold, and the vertical conductivity of the soils. The resulting simulation generated spatially distributed time series of the snow water equivalent, snow melt, precipitation, total evapotranspiration, potential evapotranspiration, and a time-series of the total runoff generated at the outflow pour-point of the Saddle catchment. This data package contains the spatially distributed time series of snow water equivalent, snow melt, and runoff, as well as the model configuration file. Outputs of precipitation, total evapotranspiration, actual evapotranspiration, as well as model inputs are archived separately on the Environmental Data Initiative.

openCC (other)Apr 2023View details →

Streamflow data for Saddle Stream 16, 2020 - ongoing.

This is a summary of discharges from the stream draining Niwot Ridge Saddle to the south and is based on stage records gauged at a timber weir with a 120-degree V-notch plate installed in the fall of 2019. The weir is located approximately 380 meters SW of the Tundra Lab, and 240 meters upstream of the saddle stream weir, which was installed in 1999. It consists of average daily flow volumes in m^3. LOCATION. 40.051473782595195, -105.59131521489772 The study site is the stream draining Niwot Saddle to the south, 380 meters downstream of the source of the stream on the Niwot Saddle (near the Tundra Lab) and 240 meters upstream of the existing saddle stream weir. It is gauged at a timber weir with a 120-degree V-notch plate. TIMING. Weir was installed in the fall of 2019 by Henry Brandes and Tyler Lampard. Flow measurements began in the summer of 2020, ongoing, daily during the field season (usually from late April to early September).

openCC (other)Feb 2023View details →

Supplemental soil moisture and temperature data from the saddle catchment sensor network, 2019 - 2021.

Hand-held soil moisture measurements were taken at 8 of 16 soil moisture sensors within the sensor network at Niwot Ridge to supplement the continuous measurement system at these locations. The hand-held measurements occur much less frequently than the 10 min sensor data, but they are important in determining the spatial variability of soil moisture in the alpine.

openCC (other)Apr 2022View details →

Water Tower Index for Saddle Catchment, 2000 - 2018.

The Saddle Catchment of the Niwot Ridge LTER experiences significant spatial variation regarding snow distribution and, in turn, the timing and amount and surface water input generation (i.e., rainfall and snowmelt). In winter months and in areas that receive a high amount of redistributed snow (via wind), snow accumulation is large and the snowpack persists until the snowmelt season, creating a lag between the timing of precipitation (as snow) and the timing of surface water inputs (as snowmelt). Alternatively, areas that are scoured of snow, retain little snow. In these areas, rain is the primary source of surface water inputs, and thus there is little/no lag in the timing of precipitation and surface water inputs (as rain). The lag in the timing of precipitation and surface water inputs in the wind deposition zones, however, is critical to providing water to the surrounding and downstream environments later in the year. The snow in these areas thus act as a natural water tower to retain water (as snow) until the snowmelt season. To capture the timing and magnitude of the delay between precipitation and surface water inputs, a Water Tower Index (WTI) was generated. The WTI uses equations (see Methods) to fit a sine curve to annual precipitation (P) and annual surface water inputs (SWI). A third equation then compares to the phase and amplitude of the two sine curves, generating a metric between -1 and 1. Positive WTI values signify P and SWI out of temporal alignment (where WTI = 1 indicates strong (i.e., high amplitude) temporal misalignment between P and SWI). Negative WTI values signify P and SWI in temporal alignment (where WTI = -1 indicates strong (i.e., high amplitude) temporal alignment between P and SWI). P and SWI data were taken from DHSVM output run by Nels Bjarke, which included 19 years of information (WY2000-WY2018). The methodology was applied, spatially, across the Saddle Catchment of the Niwot Ridge LTER. In turn, this dataset reveals, importantl

openCC (other)May 2022View details →

Saddle catchment Distributed Hydrology Soil Vegetation Model Simulation (DHSVM) precipitation and transpiration variable outputs (precipitation, total, potential and actual evapotranspiration), 2 meter, 2000-2019.

The Saddle Catchment of the Niwot Ridge LTER is a densely observed, high elevation site that is ideal for hydrological model simulation and calibration. The files produced are the result of a calibration of the Distributed Hydrology Soil Vegetation model (DHSVM) using observationally based states and forcings. Input state files of vegetation, soil properties, shading, and elevation were generated using ground and satellite observations, which, in the case of coarse-resolution or point scale observations, were then interpolated to match the high resolution of the model (2-meter grid cells). Temporally continuous meteorological forcings at the hourly time-step were used to force the model to produce an hourly simulation of the surface and subsurface hydrology within the Saddle catchment. DHSVM was calibrated to effectively reproduce the annual cycle (r^2) and total volume (percent bias) of observed runoff using observations of streamflow at the outflow pour point of the Saddle Catchment from 2001-2019. Calibrated parameters include the lateral conductivity of soil types, exponential decrease of soil conductivity, snow roughness, the snow melting temperature threshold, and the vertical conductivity of the soils. The resulting simulation generated spatially distributed time series of the snow water equivalent, snow melt, precipitation, total evapotranspiration, potential evapotranspiration, and a time-series of the total runoff generated at the outflow pour-point of the Saddle catchment. This data package contains the spatially distributed time series of precipitation, total evapotranspiration and actual evapotranspiration Outputs of snow water equivalent, snow melt, and runoff, as well as the model configuration file, as well as model inputs are archived separately on the Environmental Data Initiative.

openCC (other)Sep 2022View details →

Future hydrologic outputs using the Distributed Hydrology Soil Vegetation Model (DHSVM) for the Saddle Catchment, 2001 - 2100.

The Saddle Catchment of the Niwot Ridge LTER is subject to warming in a future climate and thus changes in precipitation phase, precipitation redistribution, and timing and distribution of surface water inputs (the summation of rainfall and snowmelt) as well as changes in atmospheric demand (potential evapotranspiration, PET) and the amount of evapotranspiration (ET). The input warming data were developed to first force a future climate across the Saddle Catchment and evaluate resultant hydrologic outputs using the Distributed Hydrology Soil Vegetation Model (DHSVM). Future forcing data were generated by calculating and implementing delta values between daily average historical data and those generated from end-of-current-century Weather Research Forecasting model data. The variables perturbed in the warming DHSVM simulation were: precipitation, air temperature, relative humidity and longwave radiation. Target outputs included: daily spatially distributed precipitation (historical and future), daily spatially distributed surface water inputs (historical and future), total spatially distributed PET (historical and future), and total spatially distributed ET (historical and future). The precipitation and surface water inputs products are orthorectified (UTM projection) raster products, and the forcing data and PET and ET are CSV files. The forcing data represent catchment averages, which are distributed within DHSVM, and all other files are at the 2 m resolution.

openCC (other)Sep 2024View details →

Plant & lichen species composition data for Saddle Nodal Plots, 1971 - ongoing.

To study long-term changes in alpine tundra plant communities, thirty permanently marked plots were surveyed in 1971. These same plots were surveyed at twenty, thirty, forty and fifty year intervals from the initial sampling date; in 1991, 2001, 2011, and 2021. Due to covid and other events, data for the 50-year time point was collected over three summers, from 2021-2023. Plots are one by ten meters, divided into ten subplot quadrats, and marked with rebar. The presence or absence of each vascular plant species was recorded per plot. The cover was recorded for each species that appeared in a one meter by ten centimeter strip at the base of each quadrat within each plot. The cover of non-vascular plants, soil, rocks, and lichens was also recorded within the strip in most sampling years. Lichen were also surveyed in 1971 and 2021.These data have been used to study the changes in vascular plant and lichen communities and cover across habitats following a moisture gradient on the saddle portion of Niwot Ridge; these habitats include dry fellfield, dry meadow, moist meadow, wet meadow, snow bank, and shrub tundra. While we have observed some changes in species richness and cover in the plots, overall the plant communities seem fairly stable over time. Lichen species richness has increased in some habitats, while some lichen species have been disappearing from others.

0.5-meter elevation lattice grid, Saddle grid, Niwot Ridge LTER, Colorado

This is a 0.5m lattice/DEM derived using the TOPOGRID command. 1:500 scale. This dataset is part of the Saddle grid geographic information system (GIS). Additional information concerning the Niwot Ridge LTER hierarchical GIS can be found in Walker et al. (1993).

2-meter elevation contours, Saddle grid, Niwot Ridge LTER, Colorado

Coverage of 2-meter contours at Saddle grid. 1:500 scale. This dataset is part of the Saddle grid geographic information system (GIS). Additional information concerning the Niwot Ridge LTER hierarchical GIS can be found in Walker et al. (1993).

Geum and Kobresia soil inorganic and organic property data for Saddle and North of Tvan, 1993.

This study was initiated to examine bulk density and organic matter content differences between soils where Geum (Acomastylis) rossii and Kobresia myosuroides were present. A subset of samples were also measured for total C, N, and P. Paired plots were randomly selected in locations where Kobresia and Geum populations were adjacent to one another. Soil samples were collected from 35 plots, 22 and 13 of which had southerly and northerly aspects, respectively. Soil cores were removed with 3.5-cm interior diameter PVC pipe that was driven into the tundra by use of a rubber mallet. The minimum depth of individual cores was 9 cm, and these depths were recorded at the time of removal (15 July, 19 July, 22 July, and 9 August 1993).

Ranunculus adoneus mycorrhizal data for Saddle 1990 - 1991.

Ranunculus adoneus plants were collected bi-weekly from Niwot Ridge Saddle grid stake 34 during the 1990 and 1991 growing seasons. Development of mycorrhizal and other fungi within plant roots was quantified. Distinct patterns of mycorrhizal development were observed and corresponded with phosporus accumulation in R. adoneus. This accumulation occurred late in the growing season after seed set, when plants were producing new tissues for the next year and appears to allow the plants to bloom the next year when snowmelt begins.

Ranunculus adoneus nutrient, soil temperature, and soil moisture data for Saddle, 1990 - 1991.

Ranunculus adoneus plants were collected biweekly from Niwot Ridge Saddle grid stake 34 during the 1990 and 1991 growing seasons. Associated plant biomass, as well as nitrogen and phosphorus levels, were determined. Soil nitrogen, phosphorus, moisture, and temperature also were measured. The relationships between these factors and mycorrhizal development were examined. Mycorrhizal development corresponded with phosphorus accumulation in R. adoneus. This accumulation occurred late in the growing season after seed set, when plants were producing new tissues for the next year and appears to allow the plants to bloom the next year when snowmelt begins. Edaphic factors such as soil temperature, soil moisture, and soil N and P levels did not correlate with patterns in mycorrhizal development. In contrast to the pattern of P uptake, R. adoneus took up nitrogen (N) very early in the growing season during snowmelt, when availablitity was high, new roots had not yet formed, and old roots contained high levels of dark septate (DS) fungus.

Soil temperature data for Saddle, 1992 - 1993.

Trace gas samples were collected from 3 alpine tundra vegetation community types (dry meadow, moist meadow, wet meadow) on Niwot Ridge during the summer months of 1992 and 1993. In addition, samples were collected from a set of control and nitrogen amended plots in both dry and wet meadow community types. Soil temperatures were measured in conjunction with the trace gas sampling.

Baseline soil inorganic and organic property data for Saddle snowfence, 1993.

Soil cores were collected during the construction of the 100+year snowfence on the Niwot Ridge Saddle in the autumn of 1993. Organic matter determinations were made on the samples in January 1994. The samples were also measured for total phosphorus, nitrogen, and carbon. These 1993 samples were representative of the baseline (pre-snowfence) soil conditions.

Alpine tundra and krummholz soil temperature data for Saddle and North of Tvan, 1994 - 1999.

Growing season soil temperatures (typically at 2 depths in a given location) were measured (1) to quantify the soil temperature environment across the landscape mosaic of alpine tundra, and (2) to compare temperatures between tundra and adjacent krummholz vegetation. Measurements were made at sites differing in aspect (south-facing and north-facing) and moisture conditions (dry, mesic, and wet). In addition, soil temperature was measured at a site characterized by persistent snow cover, as well as at sites within and adjacent to a krummholz patch. Data are presently collected using an Omnidata DP212 datapod.

Krummholz island size, soil inorganic, and organic property data for Saddle, S slope of Niwot Ridge, 1994.

Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) tree islands modify the characteristics of surface soils in alpine tundra. Soil C content of the approximate A horizon (top 15 cm) of soil was measured during the summer of 1994 on windward, leeward, upslope and downslope sides, and interiors of tree islands on Niwot Ridge, Colorado, USA. A subset of samples from these sites were also used for CHN analysis and were measured for total phosphorus using persulfate digestions and colorimetric measurements. Results indicate significant (p<.0001) reductions of percent of dry mass represented by C in soil and significant (p<.04) declines in absolute C storage among soils on the windward sides of tree islands as compared to the upslope and downslope controls, and a tendency for reduced C on the leeward sides as well. Surface organic matter (O horizon) accumulations averaging 9.6 +/- 1.02 kg/m^2 are found in the interior of tree islands, but this material, in addition to roots, is not stabilized in the A horizons of soil. The movement of tree islands can therefore be regarded as disturbances to soil building processes in alpine tundra. Timberline forest and adjacent tundra patches of similar aspect and slope were also sampled for comparisons of soil C content. Results indicated similar C storage beneath trees and tundra at this lower elevation. The wind-induced movement of tree islands across the tundra creates enhanced snowpack within the trees and on their leeward sides. Shading and moisture conditions of the soil are altered, leading to C deposition and decomposition dynamics which differ from that of unimpacted tundra surface soils. However, at timberline, adjacent tundra lacks the ability to exhibit the enhanced C storage of alpine tundra at higher elevations. Snowpack within trees and adjacent tundra at timberline may be relatively constant such that biophysical factors affecting soil characteristics are relatively unchanged by plant life-form.