Data on the effects of shading tundra vegetation from the sun when it is low in on the horizon in the north. If light quality was altered through shading, phenology might be affected. Senescence (color change) was measured for the common tundra species.
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Three replicate shade experiments were set up at CF, TL and SG, approximately 50 m from the main transplant gardens to the SE at CF, E at TL and NW at SG. Each experiment was arranged in 5 blocks, each with three treatments. Blocks were approximately 15 m apart and treatments were 1-2 m apart. Each treatment was as follows. A 1 m wide, 30 sheet of plastic held up right by two steaks on either side and 1 piece of rebar at the center was positioned 0.5 m to the north (true north) of a study tussock. The walls were either black (Shade, SH treatment) or clear with (Clear, CL treatment) or no wall at all (control, CT treatment). At TL an additional treatment was added that consisted of A shade wall but with enhanced far-red light between the hours of 11 pm and 3 am. (Far red, FR treatment). This was achieved with a 15W LED bulb that produced FR light in a water-proof case. The light was located at the base of the end of the wall and directed at the tussock of study at each plot.
Shade walls set up on:
CF = 6/30/2016
SG = 7/1/2016
TL = 7/1/2016?
One tiller on one tussock per plot was tagged at its base using a plastic zip tie. The dead, brown leaves were clipped from the tiller and the total length and the green length of each live leaf was measured to the closest 0.5 cm approximately weekly. This was done by placing the ruler as far into the tussock as possible and measuring from that point to the end of the leaves.
A Vegetation senescence survey plot (0.25m x 1m) was setup 0.25m away from the shade wall and the 4 corners of the plot were marked. The survey was done on the most commonly found species in moist acidic tundra in order to get good replication. A visual number scale applied to each individual species was used to gauge the plants greenness (evaluated the entire .25m x 1m plot) and was created from 10 to 0, 10 being Green with no signs of senescence and 0 being no green left.
Each species senesces a different way:
SP leaves go from green to yellow and then either drop or turn brown. LP is an evergreen, but its leaves go from vibrant green to very dull green/brown. VU leaves turn red and purple before falling off. VVI leaves go from green to a dull green/brown. Note that VVI, an evergreen, has young leaves that are typically red and that in the assessment we conducted, adult leaves were the ones used to gauge senescence. RC is vibrant green and then the edges start turning purple and move toward the midrib until the leaf withers. CT is another evergreen that goes from lime green to dull green/brown. PB is deep green and starts to turn purple/red before it withers. CB turns from a light green to various shades of yellow green before finally turning brown. PF is a vibrant green that turns purple/red and withers completely.
TL Veg survey: Such bad issue with map that data from 7.8.16 was copy and pasted into 7.2.16 and all given 10 because our notes show no senescence, but not which plot was the right one.
Data is separated into two sheets: 'All leaves' contains leaves that were already partly senesced at the beginning of the season and leaves that were initialized but for growth in the next season
Active leaves only' only include leaves that have no senesced portions and/or are actively elongating in that year
Version 1: uploaded to data portal
Version 2: corrected author listing.