Increased temperature, N and snowpack experiment for north of saddle, 2006 - ongoing.

In 2006 we established a global change experiment in the Front Range
of the Rocky Mountains to investigate how manipulations of warmer
summer temperature, N deposition, and increased snowpack would
affect the growth of alpine plants. The experiment was implemented
on Niwot Ridge, where shrub cover has expanded by over 400% since
1946 (Formica et al. 2014). We established experimental plots north
of the Niwot Ridge saddle, in an area of moist meadow tundra where
willow shrub (Salix sp.) patches are present.

Within experimental plots, Salix glauca seedlings were transplanted
in 2006 and 2007 to test whether changing environmental conditions
facilitated shrub survival and growth. In 2007 and 2008,
phenological observations were recorded for all (2007) or abundant
(2008) species in experimental plots. Measurements of plant species
composition and aboveground net primary productivity (ANPP) are also
made annually or biennially (ANPP, 2017-onward). In 2021, canopy
height and NDVI began being measured annually.

In July of 2016, a community transplant experiment was implemented
to test whether changing environmental conditions support changes in
alpine tundra plant communities. Two species characteristic of (1)
dry meadow tundra (Tetraneuris acaulis, Erigeron pinnatisectus), (2)
snowbed tundra (Ranunculus adoneus, Saxifraga rhomboidea) and (3)
subalpine meadow (Trollius albiflorus, Polemonium pulcherrimum) were
transplanted into experimental plots. Survival and growth of
transplants was documented annually through 2021.