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Database for Landscape-scale Carbon Monitoring Sites

Niwot Ridge Long-Term Ecological Research Site

[photo:] NIWOT, September 2008.  (Photo by Brianna Miles)The Niwot Ridge Long-Term Ecological Research Site (NIWOT) was established in 1980 as an alpine study area that is entirely above 3000 m in elevation.  

Station Description


NIWOT is located in the Front Range Mountains, at 3000-3500 m elevation, in the southern Rocky Mountains.  The site (40° 03'N, 105° 36'W) is about 35 km west of Boulder, CO.  The research area is bounded to the west by the Continental Divide.


NIWOT vegetation is characteristic of subalpine forests.  Subalpine fir (Abies lasiocarpa) and Engelmann spruce (Picea engelmannii) are the dominant tree species at higher elevations, and Lodgepole pine (Pinus contorta) at lower elevations, with some minor occurrence of Limber pine (Pinus flexilis) and Trembling Aspen (Populus tremuloides).  In measured plots, maximum tree age is 133 years, tree density is 1,726 stems per hectare, tree height is 10.3 m, and LAI is 3.6 m2/m-2.  Understory vegetation is generally herbaceous annuals or perennials, vaccinium species or willow (Salix spp.) shrubs.


The NIWOT climate is characterized by cold and relatively long winters, with a mean annual temperature of 1.5 °C, and mean annual precipitation of 800 mm.  Freezing temperatures may be observed at any time of year.  Most precipitation falls as snow, and snow cover lasts from as early as October through June.  Summer precipitation occurs primarily as afternoon thunderstorms. 

Relevant Land Management Area

The NIWOT was established in 1980.  The LTER program, based from the University of Colorado-Boulder, is administered through the Institute of Arctic and Alpine Research (INSTAAR) in cooperation with the Mountain Research Station, with special use permits from the USDA Forest Service.  NIWOT is located within the Roosevelt National Forest and is designated as an Experimental Ecology Reserve (USDA Forest Service) as well as a Biosphere Reserve (United Nations Educational, Scientific and Cultural Organization, UNESCO).

Management and Disturbance History

Disturbances in this region of the southern Rocky Mountains are typically characterized by infrequent, extensive stand-replacing fires, episodic insect outbreaks, and occasional wind damage.  NIWOT was clearcut between 1900 and 1910, and fire history for the area is unknown, but remnant stumps and the logging itself suggest the forest was mature and possibly 200 years old at that time.

Research - Past and Present

Current Research

Several ongoing studies are conducted at NIWOT involving global change, and specifically climate change and nitrogen deposition.  Interactions between climate and ecosystems with complex topography which generate unique source and sink environments for water and nutrients, are examined at these high elevation sites in the Colorado Front Range.

More information at:

NACP Biometric Data

Plot layout of the NRAT intensive landscape research and monitoring site overlaid on National Agriculture Imagery Program (NAIP) 2008 imagery.

NIWOT has one NACP intensive landscape research and monitoring site with 12 FIA style plots (4 subplots per plot) and 13 single radius plots.  Nine FIA style plots were established in 2004 within a 1km2 area and 3 additional FIA style plots established in 2005 outside the 1 km2.   Thirteen additional single radius plots were established in 2008-09 within the 1 km2.

NIWOT intensively monitored site:

- Niwot Ridge AmeriFlux Tower (NRAT)

Biometric Data

Tree, sapling, seedling

Tree (>=10cm dbh) and sapling (2.5 – 10 cm dbh) species, status (live or dead), dbh, total height, live upper and lower crown height, live crown width, crown class (indicates amount of sunlight received) and decay of standing dead.  Seedling count by species (< 2.5 cm dbh).  Collection 2004–05, and 2008–09.

Tree, sapling, seedling biomass

Estimated using species specific and Jenkins et. al. (2004) allometric equations.

Down woody material

Including coarse and fine woody debris estimated.  Collection 2004–05, and 2008–09.

Forest Floor

Mass collected and C:N ratio analysis.  Collection 2004–05, and 2008–09.


Mass collected and C:N ratio analysis.  Collection 2004–05, and 2008–09.


Mass collected and C:N ratio analysis in 2004–09 .


Sampled in 3 m x 3 m plot.  Plots established in 2006, collection and C:N ratio analysis in 2008–09.


Additional Data Sets


Remote Sensing and Spatial Data

MODIS Land Subsets

Niwot Ridge MODIS subset

Site characterization data

Niwot Ridge AmeriFlux site characterization; elevation, geology, land cover and soils.

LiDAR – first and last return

Discrete LiDAR data was collected in 2005 by Airborne 1 (El Segundo, Calif.) using an Optech ALTM 2025/2050.

LiDAR indices

Derived from discrete LiDAR data (25 m resolution) collected in 2005 by Airborne 1 (Sherrill et al. 2008).

  • Number of returns
  • Minimum elevation
  • Maximum height
  • Mean height
  • Quadratic height
  • Ground threshold, height below which returns were considered ground
  • Canopy point density, % of points above 1m
  • Coefficient of height variation, ratio of the standard deviation and mean height
  • Height at which % of points are below (10% increments from 0 -100%)
  • % of points in 2 meter bins (from 0-100m)


EO-1 collected in 2005.


LANDFIRE Data Products

  • Existing Vegetation Cover (EVC)
  • Existing Vegetation Height (EVH)
  • Existing Vegetation Type (EVT)
  • Biophysical Settings (BPS)
  • Environmental Site Potential (ESP)


  • Fire Behavior Fuel Model13 (FBFM13)
  • Fire Behavior Fuel Model 40 (FBFM40)
  • Canadian Forest Fire Danger Rating
  • System (CFFDRS) (AK only)
  • Canopy Bulk Density (CBD)
  • Canopy Base Height (CBH)
  • Forest Canopy Cover (CC)
  • Forest Canopy Height (CH)
  • Fuel Characteristic Classification
  • System Fuelbeds (FCCS)
  • Fuel Loading Models (FLM)

Fire Regime

  • Fire Regime Groups (FRG)
  • Mean Fire Return Interval (MFRI)
  • Percent Low-severity Fire (PLS)
  • Percent Mixed-severity Fire (PMS)
  • Percent High-severity Fire (PRS)
  • Vegetation Condition Class (VCC)
  • Vegetation Departure (VDEP)
  • Succession Class (SCLASS)


AVIRIS data collected in 2005

Additional spatial data

Geospatial Data Layers



Niwot Ridge LTER Data Catalog

Niwot Ridge LTER Data Catalog

Stand age

Stand age (site age) calculated from site tree age.

Tree increment cores

Original cores collected in 2004-05; recorded in 2009.

Shrub, herbaceous biomass

Shrub (vaccinium spp.) foliage and aboveground herbaceous biomass, collected using destructive sampling methods, and C:N ratio analysis.  Collection 2004–05, and 2008–09.

Shrub, herbaceous cover

Shrub and herbaceous cover estimates.  Collection 2004–05, and 2008–09.


Ingrowth cores measured root biomass production.  Established 2005, harvested 2008.

Litter decomposition

Bags measured litter decomposition and C:N ratio analysis.  Established 2005, harvested 2009.

Soil CO2 respiration

Summer collection 2004–08. 

Soil moisture

Collected simultaneously with summer soil CO2 respiration 2004–08. 

Snow CO flux, density

Winter collection 2004-07.

[photo:] NIWOT SNOTEL site.

Meteorological and Atmospheric Data

Wet deposition, precipitation

National Atmospheric Deposition Program (NADP) data
National Trends Network (NTN) precipitation water chemistry

  • Niwot Saddle (CO02) data from 1984 – present
  • Niwot Ridge-Southeast (CO90) data from 2006 – present


SNOTEL data (1979 – present) from Niwot (663)

Snow report

Niwot LTER snow report

Meteorological Observations

Tower observations from meteorological sensors (1953-present)
Niwot Ridge LTER Data Catalog

Carbon and Halocarbon

NOAA Earth System Research Laboratory – Global Monitoring Division for Niwot Ridge, Colorado, United States (NWR)


National Weather Service precipitation gage

Weather station

NOAA Climate Research Network (CRN) weather station for CO Boulder 14 W

Models and Model Outputs

LiDAR models

Derived from discrete LiDAR data (25 m resolution) collected in 2006 by Airborne 1.

  • Canopy height model
  • Digital elevation model
  • Digital surface model
  • Mean forest height
  • Aboveground biomass
  • Log basal area total
  • Trees per hectare


[photo:] NIWOT flux tower

Flux Tower

The NIWOT flux tower is located in Subalpine mixed coniferous forest with very little understory and has been in operation since 1997. 


Site description and data


Site description and data

University of Colorado

5 and 30 minute data

Regional Reference Datasets and Products


Forest Inventory and Analysis National Program data and tools


National Aeronautics and Space Administration – Carnegie Ames Stanford Approach; Global CQUEST – Carbon Query and Evaluation Support Tools


Daily surface weather and Climatological Summaries

Phenology Web Camera


The phenology camera automates near-surface remote sensing to provide continuous, real-time monitoring of vegetation phenology across a range of ecosystems and climate zones.  The camera has been collecting data at Bartlett since 7/23/2009.



NIWOT publications from 1982 – present
NIWOT reports from 1993 – present


Bowling, D.R.; Massman, W.J.; Schaeffer, S.M.; Burns, S.P.; Monson, R.K.; Williams, M.V.  2009.  Biological and physical influences on the carbon isotope content of CO2 in a subalpine forest snowpack, Niwot Ridge, Colorado.  Biogeochemistry 95: 37-59.

Bradford J.B.; Weishampel, P.; Smith, M-L.; Kolka, R.; Birdsey, R.A.; Ollinger, S.V.; Ryan, M.G.  2009.  Detrital carbon pools in temperate forests: magnitude and potential for landscape-scale assessment.  Canadian Journal of Forest Research 39: 802-813.

Bradford, J.B.; Birdsey, R.A.; Joyce, L.A.; Ryan, M.G. 2008.  Tree age, disturbance history, and carbon stocks and fluxes in subalpine Rocky Mountain forestsGlobal Change Biology 14: 2882–2897.

Bradford, J.B.; Weishampel,P.; Smith, M-L.;  Kolka, R.K.; Hollinger, D.Y.; Birdsey, R.A.; Ollinger, S.; Ryan, M.G..  2008.  Landscape-Scale Carbon Sampling Strategy – Lessons Learned.  Pages 227-238 in CM Hoover, editor, Field measurements for forest carbon monitoring: A landscape-scale approach, Springer, New York, NY, USA. 

Bradford JB and MG Ryan.  2008c.  Quantifying soil respiration at landscape-scales.  Pages 143-162 in CM Hoover, editor, Field measurements for forest carbon monitoring: A landscape-scale approach, Springer, New York, NY, USA.

Sherrill, K. R.; Lefsky, M. A.; Bradford, J.B.; Ryan, M.G. 2008. Forest structure estimation and pattern exploration from discrete-return lidar in subalpine forests of the central Rockies. Canadian Journal of Forest Research, 38, 2081-2096.

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