This dataset includes every pin-hit recorded from 19 1m x 1m point frame plots of tall Betula nana and Salix pulchra canopies sampled at the Toolik Field Station, AK the summer of 2012. Twenty-five evenly spaced holes within the plot were sampled for each point frame for which the height and species was recorded for each leaf, stem, or plant that intersected the pin when lowered perpendicular to the ground. Non-woody species were grouped into functional groups (e.g. forb, graminoid, moss) and not identified to species. Stem diameter and the length of gramminoid blades were also recorded.
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We preferentially selected tall shrub canopies dominated either by Betula nana or Salix pulchra, that is canopies that were greater than 75 cm height. Care was taken to select fairly uniform canopies, that is avoiding the edge of a shrub stand or areas where the canopy had a large gaps, suggesting the area may have been disturbed.
We used point frames constructed from a 1.1 m x 1.1 m aluminum square with holes in each corner to accomodate steel rod posts used as the legs of the point frame. In this way, the frame could rest upon the four leg posts that had been hammered into the ground and remain adjustable in each corner. The frame had a level on each side, and great care was taken to ensure that the frame was (a) unable to be pushed deeper into the ground and, (b) level on all four sides prior to taking measurements. These factors were important to the measurement to have accurate data regarding the distance from the frame and the overall height of each point sampled in the canopy.
The aluminum frame had numbered, regularly spaced holes on two opposite sides in order to accomodate a metal bar that could be placed across the frame and locked into place. [These holes on the frame are the row numbers.] The bar that was placed across the frame similarly had numbered, evenly spaced holes in order to accomodate a pin--a long (100-200cm) metal rod with a diameter of ~3.175 mm. [The holes on this bar are the pin hole numbers.] Measurements were only ever taken from odd row numbers, and alternated even/odd pin hole numbers with each row; in this way, for every plot 25 evenly spaced locations were sampled covering an area of one square meter.
The length of the pin was marked every half-centimeter so that the distance could be read easily. Measurements were made by lowering the pin through a pin hole and, once encountering a leaf or stem, recording the following: row#, pin hole#, hit#, and the species hit. If the object hit was not a leaf, the plant tissue was noted; the diameter of each stem hit was estimated in millimeters, and the length of every graminoid blade hit was recorded from the point at which it was hit to the tip. As the primary species of interest for this project were for a select number of species (B. nana, S. pulchra, S. glauca, S. reticulata, V. uliginosum, V. vitis, L. palustre), species that were not the target of interest were classified as functional groups--e.g. graminoid spp., forb, moss.
The last pin-hit recorded for each pin hole was always at the "soil" which was considered to be the transition between the green and brown plant material, often in a mossy layer.
These data can be used in conjunction with the other data collected from these same plots--leaf area index, light and A-Ci response curves of shoots taken at different segments of the canopy.
This was a season-long project, though it followed similar methods to ITEX projects performed starting in 2003 that are likely to be replicated in the future for reasearch at the Toolik Field Station, AK.
Version 2: Missing values changed to #N/A. CH 28Jan2013
Version 3: Metadata updated to newer form (with sites sheet). CH April 2013.
Version 4: Corrected eml excel file name wrong extension. JimL 16May13
Version 5: Corrected Distrubution URL. It had xlsfiles in the path. Jim L 19Jun14
Version 6: Changed Distrubution URL since the LTER network DAS system is being discontinued. JimL 9Apr2015
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