Search for: All records

A plant species list was created for Niwot Ridge and Green Lakes Valley from species identified in those areas by NWT scientists, working primarily at the Saddle and Martinelli sites. Additions to this list included species identified by Komarkova (1979) in the Indian Peaks Wilderness area but not on Niwot Ridge or in the Green Lakes Valley because of the likelihood that those species might exist within the LTER research area. Additions to the list were also provided by Terry Theodose, Leeanne Lestak, Teresa Nettleton, Susan Sherrod, Laura Mujica-Crapanzano (2004), Hope Humphries (2006), and Jane G. Smith (2019-2025). The list was revised to remove duplicate entries, correct typos, and resolve synonymy problems. Species and non-species categories received USDA PLANTS database names and codes. 

Permanent 1 m^2 vegetation plots were established near each of the 88 Saddle grid stakes in 1989 by Marilyn Walker, who led the sampling effort until 1997. To estimate plant canopy cover, point quadrat measurements have been made at irregular intervals from 1989 to the present (1989, 1990, 1995, 1997, 2006, 2008 and yearly from 2010 onward). The point-quadrat technique used for sampling was described in Spasojevic et al. (2013) and Auerbach (1992). Auerbach, N. 1992. Effects of road and dust disturbance in minerotrophic and acidic tundra ecosystems, northern Alaska. University of Colorado, Boulder, Colorado, USA. Spasojevic, Marko J, William D Bowman, Hope C Humphries, Timothy R Seastedt, and Katharine N Suding. Changes in alpine vegetation over 21 years: Are patterns across a heterogeneous landscape consistent with predictions?” Ecosphere 4, no. 9 (2013): 1–18. https://doi.org/10.1890/es13-00133.1. 

Total aboveground live vascular biomass was clipped from 50x20 cm plots in areas near the saddle grid permanent plots on Niwot Ridge to measure net primary productivity. NDVI measurements were also included in some years. 

Abstract Rapid climate warming is altering Arctic and alpine tundra ecosystem structure and function, including shifts in plant phenology. While the advancement of green up and flowering are well-documented, it remains unclear whether all phenophases, particularly those later in the season, will shift in unison or respond divergently to warming. Here, we present the largest synthesis to our knowledge of experimental warming effects on tundra plant phenology from the International Tundra Experiment. We examine the effect of warming on a suite of season-wide plant phenophases. Results challenge the expectation that all phenophases will advance in unison to warming. Instead, we find that experimental warming caused: (1) larger phenological shifts in reproductive versus vegetative phenophases and (2) advanced reproductive phenophases and green up but delayed leaf senescence which translated to a lengthening of the growing season by approximately 3%. Patterns were consistent across sites, plant species and over time. The advancement of reproductive seasons and lengthening of growing seasons may have significant consequences for trophic interactions and ecosystem function across the tundra.