Marking Rules

When conducting a cutting-cycle harvest in an uneven-aged southern pine stand, the guidance given to field crews can be summarized by a simple rule: cut the worst trees and leave the best (Baker and others 1996; Farrar 1996; Farrar and others 1984, 1989; Guldin 1996; Reynolds 1959, 1969). When stands have developed an uneven-aged structure through time, tree size generally becomes correlated with age across the diameter distribution (Baker and others 1996). Marking a percentage of the poorest trees in each diameter class improves the average tree quality within each class, and over time only the best trees of highest quality attain the largest size. As a result, one attribute of the selection method is that over time, it produces large sawtimber that has high quality. 

In stands being converted from even-aged to uneven-aged structure, size is not correlated with age, because the smaller trees may be of the same age as the larger trees. This means that most trees in the left-hand tail of a normal bell-shaped diameter distribution may in fact be the worst trees in the stand. Strict adherence to the rule of cutting the worst and leaving the best may result in an effect similar to thinning from below, where most of the smaller trees are removed. This is preferable to retaining poorer trees in smaller size classes at the expense of better trees in larger classes simply to achieve a target structure. If the best trees are being retained below the maximum diameter and are retained in a manner that allows development of subordinate stems and newly established regeneration cohorts, a perfectly balanced stand structure is immaterial. 

Marking crews need guidance in judging whether an intermediate tree in the pulpwood size class can respond to release if it is allowed to remain in the stand. Reynolds (1959) noted that loblolly pine in the west gulf region could respond to release, even at advanced age. Baker and Shelton (1998b) observed that if a loblolly pine had a 20-percent live crown ratio and good apical dominance, it should satisfactorily respond to release, even if it developed in the lower crown classes of fully stocked, uneven-aged stands for up to 40 years; anecdotal evidence for longleaf pine is similar. Different standards would probably apply for other southern pine species and for trees from lower crown classes in even-aged stands. 

To a certain extent, the group selection approach to management of uneven-aged stands violates the rule of cutting the worst trees and leaving the best. Group selection usually prescribes cutting of all trees, best and worst, if they are within the group. The degree of conflict depends on how the groups are located. If groups are identified independently of density or stocking, for example, by systematically installing groups of similar size and shape according to a predetermined pattern, the opportunity to cut the worst and leave the best is seriously compromised. Conversely, if groups are established in understocked portions of the stand, without regard for size, shape, or pattern of group opening, the number of best trees that must be cut will be reduced. Group selection with reserves (Helms 1998) is probably the best, though least often prescribed, method to minimize conflicts with the “cut the worst and leave the best” axiom, provided that reserved trees within the group are the best trees and do not adversely affect regeneration establishment or development.