Data on overstory and understory trees in aspen-dominated boreal mixedwood stands over 20 years after partial harvesting

Growing demand for non-timber forest ecosystem services has resulted in increased use of partial harvesting in boreal forests. Since the 1990s, multiple studies have yielded short-term responses to partial harvesting. Here we present an inventory of longer-term (20 years) responses of overstory and understory trees to partial harvesting in aspen-dominated boreal mixedwood stands. Pre- and post-harvesting overstory trees were mapped and measured for total height and diameter at breast height (DBH); understory trees were measured for total height. Codes identify tree species, treatments, and years since harvest. Data are stored in separate Microsoft Excel spreadsheets: overstory trees, understory trees, and years after harvesting.


a b s t r a c t
Growing demand for non-timber forest ecosystem services has resulted in increased use of partial harvesting in boreal forests. Since the 1990s, multiple studies have yielded short-term responses to partial harvesting. Here we present an inventory of longer-term (20 years) responses of overstory and understory trees to partial harvesting in aspen-dominated boreal mixedwood stands. Pre-and post-harvesting overstory trees were mapped and measured for total height and diameter at breast height (DBH); understory trees were measured for total height. Codes identify tree species, treatments, and years since harvest. Data

Subject area
Forest ecology More specific subject area

Tree inventory data
Type of data

Value of the data
Overstory and understory tree data assessed at 0, 1, 3, 5, 11, and 20 years post-harvesting. Potential to analyze long-term dynamics of boreal forests following partial harvesting and forest tent caterpillar outbreaks.
Opportunity to link short and long-term responses and assist resource managers in projecting long-term stand density, composition, and yield.
Opportunity to study stand-scale mortality and ingrowth processes using mapped tree locations.

Data
The overstory and understory tree data presented here were the basis for the research article by Yang and Man [1] and the method documented by Man and Yang [2]. The raw data analyzed by Yang and Man [1] are available as Microsoft Excel spreadsheets in the Supplementary Material. An excerpt of the overstory data (Partial cut_Overstory) is shown in Table 1 and the understory data (Partial cut_Understory) in Table 2. Note: Each year's data is stored in a separate worksheet. Previously reported post-harvesting data includes 5-and 11-year regeneration analyses [3,4] and 11-year responses of overstory trembling aspen to harvesting and forest tent caterpillar defoliation that occurred 3 to 5 years after harvesting [5].

Experimental design, materials and methods
Data presented here is from a partial harvesting experiment established in the early 1990s. The initial design was a randomized complete block with 4 harvesting treatments replicated 4 times. The study was originally designed to remove 0 (unharvested), 36 and 68% (partially harvested), and 100% (clearcut) of the merchantable overstory basal area (BA) of all trees Z10 cm DBH. During application, however, the design was adjusted with the actual basal area removal approaching 40% for the partial harvesting treatments. Adjustments were necessary because of limiting operational site characteristics and the overarching need to protect advance conifer regeneration, resulting in 8 replications of 40% partial harvesting [3,6]. During January-February 1995, the 100 m×100 m harvesting plots were full-tree logged with a feller-buncher and a grapple skidder. To achieve the 40% harvesting level, 20% of the overstory was removed, focusing on large trembling aspen and balsam fir in 16-m-wide leave strips plus 5-m-wide skid trails that were clear cut. To minimize machinery damage to residual trees, harvesting was done using careful logging techniques [6]. After harvesting, overstory plots, with a 25 m radius (0.2 ha) divided into 12 sections of 30 degree segments, were established in the centre of the 1-ha harvested area. Pre-and post-harvesting measurements included DBH and height for all tree species Z4.0 m, survival status (live¼ 1 and dead¼ 2), as well as the location, distance and azimuth, of individual stems in relation to plot centre. On the circumference of the overstory plots, 12 equally spaced 2 m×2 m understory plots were established. Within the understory plots, all tree species o 4.0 m were identified and measured for total height.