The Niwot Ridge (NWT) LTER site was one of the five original LTER sites established in 1980. The LTER program is based at the University of Colorado-Boulder and is administered through the Institute of Arctic and Alpine Research (INSTAAR) and in cooperation with the Mountain Research Station, with special use permits from the US Forest Service.

Spatial and temporal changes in alpine plant species composition were analyzed at the landscape, plant community, and individual species levels. We standardized field observations for 88 gridded vegetation plots sampled in 1990, 1997, and 2006 on Niwot Ridge, Colorado and developed spatial environmental data for the study area (snow cover, growing-degree days, time of meltout, and solar radiation). At the landscape scale, growing-degree days increased from 1990 to 2006, while the snow-covered period decreased and meltout occurred earlier.

A forest die-back caused by a beetle outbreak on lodgepole and limber pine was used to assess the relative importance of root inputs to the soil food web and chemistry of soils in the Colorado Front Range. We measured a suite of biological and chemical parameters at six sites containing both live and dead trees. We found an increase in amounts of soil inorganic N, decreased soil lable C, and thus a decreased soil labile C:N ratio.

Dissolved organic matter (DOM) dominates the material and energy fluxes within aquatic ecosystems. Carbon fuels the majority of microbial processes, including those that regulate in-stream nitrogen constituents. DOM sources and in situ transformations determine its chemical nature and lability within aquatic systems. Boulder Creek, which is located in the Colorado Front Range and spans an ecosystem gradient from the Continental Divide to the high plains, receives excess atmospheric nitrogen deposition due to its proximity to population centers and agricultural lands.

Ecosystems in topographically complex (mountainous) terrain are responsible for a majority of land-atmosphere CO2 exchange (net ecosystem exchange; NEE) across the western United States due to high inputs of winter precipitation as snowfall. NEE in these regions has been historically difficult to quantify using the eddy covariance (EC) method, however, due to complexities in surface terrain that lead to irregularities in streamline air flow, particularly advective fluxes during periods of low turbulent mixing.

Soil temperature is one of the key determinants of carbon flux, nutrient availability, decomposition rates, and primary productivity in high-elevation and high-latitude ecosystems. Global climate models predict that as air temperatures rise there will be a corresponding increase in soil temperature and a longer snow-free season.

Microorganisms have confounded biogeographers because of their high dispersal capability, small size, and vast diversity and abundance. Here we use pyrosequencing, bioinformatics tools, and geospatial modeling to reveal that the genetic relatedness of soil bacteria varies in a predictable pattern across a landscape. Microbial communities showed strong spatial autocorrelation to a distance of 240 meters and this pattern was driven by changes in the genetic relatedness and abundance of specific clades across the landscape.

 In areas containing seasonal snowpacks, snowmelt contributes significantly to the hydrological cycle. Thus, quantifying the spatial distribution of flow through a snowpack is essential to accurate hydrograph interpretation and representation in snowmelt runoff modeling. Movement of liquid water through snowpacks is generally recognized to occur in distinct flow paths rather than as uniform flow through a homogeneous porous medium.

An experimental system for sampling trace gas fluxes through seasonal snowpack was deployed at a subalpine site near treeline at Niwot Ridge, Colorado. The sampling manifold was in place throughout the entire snow-covered season for continuous air sampling with minimal disturbance to the snowpack. A series of gases (carbon dioxide, water vapor, nitrous oxide, nitric oxide, ozone, volatile organic compounds) was determined in interstitial air withdrawn at eight heights in and above the snowpack at ~hourly intervals.

An outstanding question for snowmelt-dominated watersheds of the western US is the response of stream flow to changes in climate. We know little about mountain aquifers because they commonly involve structurally complicated rocks, extreme head gradients (ground slope angles 10-40°), and dramatically fluctuating recharge due to seasonal snow-melt. In general, the western United States is predicted to face warmer temperatures and more frequent and prolonged droughts, and we can expect to see a decrease in annual snowpack, earlier onset of snowmelt, and increased evaporation.