Permanent forest plot data from 1982-2017 at Niwot Ridge, Colorado

The permanent forest plots at Niwot Ridge were installed in subalpine forests in the Colorado Front Range by Dr. Thomas T. Veblen in the early 1980s. The goal was to establish a set of long-term forest plots to monitor tree populations and stand dynamics over time. Ten large permanent plots (i.e., from 21 x 54m to 54 m x 54 m) were installed to monitor on average less than 400 trees per plot. An additional thirty smaller ‘gap’ plots (i.e. approximately 10 m x 10 m) were installed in canopy openings adjacent to three of the large permanent plots to monitor gap dynamics (c. 40 trees per plot). The plots are located across gradients in elevation and moisture and include the following subalpine tree species: lodgepole pine (“Pinus contorta”), limber pine (“Pinus flexilis”), Engelmann spruce (“Picea engelmannii”), subalpine fir (“Abies lasiocarpa”), and aspen (“Populous tremuloides”). When the plots were installed, all living and standing dead trees (over 6,000) were permanently tagged, and the following was measured for all live and dead trees less than 4 cm dbh: species, diameter at breast height (1.4 m), height class, and status (live or dead). Censuses of tree mortality were conducted roughly every three years and a complete re-measurement (e.g. dbh measurements) was conducted in 2016 (see methods for details). Counts of juvenile trees (less than 4 cm dbh) by species were conducted when the plots were installed and in 2017. This database includes three datasets: 1) description of plots (e.g. elevation, aspect, size), 2) tree data (e.g. dbh, height class, status) for all trees (greater than 4 cm dbh) monitored from early 1980s to 2016, and 3) counts of juvenile trees (less than 4 cm) by species in early 1980s and 2016.