Lodgepole Pine Bole Wood Density 1 and 11 Years after Felling in Central Montana

Climate Climate data recorded by the Onion Park SNOTEL site within the TCEF were accessed from the National Water and Climate Data Center and summarized for the period 2002–2009. Data prior to 2002 were incomplete. Average summer (April to September) and winter temperatures (October to March) were 8° C and 4° C, respectively. High temperatures during the warmest parts of summer were typically 20° C to 25° C while during the coldest parts of the winter temperatures often fell below 20° C. Average annual precipitation was 83 cm, about evenly split between the two seasons. Field Methods All wood samples in this study were cut from 46 live lodgepole pine trees felled in 1998. Trees were cut in nine groups. Group locations were not selected randomly, rather they were selected in stands across a range of structural characteristics representative of the TCEF (Barrett 1993). Each cutting group consisted of 7–13 felled trees. Trees were selected within each group such that the diameter breast height (dbh) frequency distribution of the sample would be similar to the diameter distribution of the surrounding stand, thus fewer sample trees were felled in stands with more homogeneous stand structure. The boles of felled trees were partitioned into 2-m “logs.” The entire bole was partitioned, thus there was no defined minimum diameter for the logs. Some logs were created by physically segmenting the tree bole with a chainsaw and the remaining boles had the 2-m logs marked using a small saw nick. Each log was given an identifier consisting of concatenated tree tag number and log number with the logs numbered sequentially starting at the base of the bole. The sample trees yielded 390 logs. After initial samples were collected in 1999, a sampling schedule of the remaining logs was created with random logs (without replacement) selected for sampling at 10-year intervals beginning in 2009. All wood samples were collected by cutting a 5–10-cm thick disk perpendicular to the central axis of the sample log using a chainsaw. The samples were cut from the ends of the logs in 1999—less than 10 months after felling—and from the middle of logs in 2009. The decay class of the log was recorded before removing the sample and piece diameter was measured using a flexible d-tape after it had been cut from the log. The 1999 sample included 45 wood samples from 12 trees and the 2009 sample included 25 samples from 16 trees. Two additional assessments were made for logs sampled in 2009: (1) we recorded the position of the log as either in contact with the ground or suspended above the ground by branches, vegetation, etc. and (2) we recorded if one or both of the log ends had been completely cut through (segmented) in 1998. Samples were stored in sealed plastic bags until lab work began. Log decay class was visually assessed using the classification described in Maser et al. (1979) (Table 1). The classification uses a condition criteria assessment of bark, twigs, texture, shape, color of wood, and portion of the log on the ground. An entire log rarely met all the criteria of a class but was assigned to the decay class of which it met the majority of criteria. Lab Methods Wood density for all samples collected in 1999 and 2009 was determined using the same procedure. All bark was removed as were pieces of dirt, debris, and any loose chips left over from cutting with the chainsaw. Piece volume was determined using water displacement by placing a tub of water on a scale and submersing the piece in the water bath using an apparatus where the submersed portion had a known volume (USDA Forest Products Laboratory 1956). Piece volume was calculated by assuming 1 g of water displacement was equal to 1 cm of wood volume. By substituting volume for displacement the volume of each sample was calculated using Equation 1, which accounted for any water absorbed by pieces during the short time they were submerged: