These methods, instrumentation and/or protocols apply to all data in this dataset:| Methods and protocols used in the collection of this data package |
|---|
| Description: | Site: The mapped macroplot is within a much larger tract (ca. 5000 ha) of old-growth forest in the Huron Mountains region of northern Marquette County, Michigan. This area is within a larger, protected area under private ownership since ca. 1880, and has experienced no logging and only minimal disturbance associated with access tracks and trails. The study site is within a complex landscape with both xeric, fire-influenced areas and mesic forests. The hemlock-northern hardwood stand including the macroplot has experienced no stand-initiating disturbance for at least 400 years (from dendrochronological and forest dynamics studies: http://hdl.handle.net/2027/spo.0497763.0058.304; DOI 10.7717/peerj.598). The macroplot and surrounding forests are dominated by sugar maple (Acer saccharum) and eastern hemlock (Tsuga canadensis). Among secondary species, yellow birch (Betula alleghaniensis) and basswood (Tilia americana) are most common. Soils (identified as Kalkaska series) are developed on deep sandy glacial outwash.
|
| | Description: | Initial layout of macroplot: At initial mapping and measurement in 1993, a mapping baseline was established beginning at the center of a pre-existing 0.2-acre forest inventory plot (Bourdo plot #7100; DOI 10.7717/peerj.598), and running at 70° east (magnetic) of north to pass through the center of Bourdo plots #7101 and 7102. Position along this line was defined as the "Long" coordinate in a within-plot rectilinear system. The "Long" dimension baseline was originally 160 m long, and was extended to 200 m in 1995, and to 240 m in 1999. Perpendicular lines were established, using a surveyor's transit crossing the baseline at 10-m intervals and reaching 50 m in both directions from the "Long" dimension baseline. Position along these lines was defined as the "Short" coordinate, with negative values to left of the baseline (to the NNW), and positive values to the right (SSE). In 1995, 'Short' dimension lines were extended to 70 m in the 'negative' direction. Stakes (PVC pipe about 50 cm tall) were placed at 10-m intervals along all lines establishing a grid throughout the large plot.
|
| | Description: | Initial mapping and measurement: Trees were mapped and measured in 20x20 m sub-plots or 'cells' defined by the grid of stakes. Mapping cells were centered at 10m 'Long', and 0m 'Short', and every 20 m from that point all directions (i.e., centers at 10,0; 30,0; 50,0; etc. and at 10,-10; 10,-30,… , 10,10; 10,30, etc.). All woody stems > 2 cm diameter breast height (DBH) were identified to species, measured, and mapped. DBH measurement was by diameter tape. Initial stem mapping used polar coordinates taken from the center point of each mapping cell. Azimuth was measured using Suunto KB-20 'sight-through' compass or similar, without correction for declination, in degrees east of magnetic north. Radial distance to approximate center of tree-base was initially measured with Sonin ultrasonic range finders with targets; in 2014-2019, laser range-finders of several makes and models were used in mapping new stems. In initial measurement years (1993-1999), stems greater than about 8 cm dbh were also tagged with numbered aluminum tags nailed at breast height; subsequent measurements were taken above tags unless otherwise noted.
Initial establishment of mapped sub-plots was in 1993 (from 'origin' to mapping cell centered at 90,0); 1994 (mapping cells from 90,20 through 150,40); 1995 (all cells with center 'Long' coordinates of 170 and 190, and cells with 'Short' coordinate of -60 from 0,-60 through 190,-60; and 1999 for all cells with 'Long' coordinates of 210, 230. Cells centered at 190,40; 210,40; 230,20; and 230,40 were not established because of proximity to a traveled woods-road.
At initial measurement all dead stems, including long-dead and downed stems with recognizable base and bole, were mapped. Dead stems were described by a 2 or 3 character code. The first character was a numerical index of degree of deterioration (0=leaves present; 1=fine twigs still in place; 2=only coarse twigs/small branches (<2 cm diam) still present; 3=only large branches (>5cm) present, bark mostly intact; 4=substantial loss of bark on bole; 5=outer wood partially decayed (to 1-2 cm depth); 6=deep decay, but trunk retains shape; 7=deep decay and trunk beginning to loose shape/integrity; 8=trunk identifiable only as mound. The second code character was one of three letters: t = tipped-up; s (or 'standing' = standing snag; b = main trunk broken, at least 2/3 of crown down. For broken stems, a third code is height of break. Thus, "4-B-2" indicates a stem broken at 2 m with substantial bark loss on remaining bole; "3-t" indicates tip-up with small branches lost; etc. Some individuals with higher decay codes were not identifiable to species.
|
| | Description: | Remeasurements: From 1999 through 2019, all stems on the macroplot were remeasured for dbh at 5-year intervals. New recruits (stems reaching 2 cm dbh since the previous measurement) were measured and mapped by methods described above. Mortality since previous measurement was noted and described by the codes defined above. Other notes describe tree condition (partial loss of crown, apparent decline, etc.) or anomalies (e.g., burls or forks at breast height). Tags were not added to stems after initial measurements. Beginning in 2009, all stems were assigned unique stem-identifier numbers that have been retained subsequently.
|
|
|
|
