Residual Stand Problems after a Whole Tree Harvest

Sullivan County, NH
Private Land
Submitted by Ehrhard Forest, Forester, Full Circle Forestry

1. Name - Residual Stand Problems after a Whole Tree Harvest

Context | Objectives | Treatment Specifics | Utilization | Targets | Pre Treatment Data | Post Treatment Data | Links 

This case study highlights a potential downside to biomass harvest. Harvesting occurred in mixed white pine and eastern hemlock stand about 45 acres in size. The stand was even aged and initiated in about 1945. Most of the stand was dominated by white pine with very good to excellent timber quality. The white pine portion of the stand was overstocked (full or nearly full crown closure). The trees were in the pole and small sawlog size classes, so commercial thinning was not practical.

A 1993 forest management plan for the property recommended a thinning and improvement cut which would remove "low quality hardwood and hemlock," while "healthy, straight white pine" would be left to grow. The plan also suggested leaving "patches of thick hemlock for wildlife cover". The entire stand was marked for harvest, but only a portion was actually cut in 1999. The plan estimated that such a treatment would yield of 1,500 board feet per acre and 7 cords per acre, (26% and 33% of the volumes respectively). Based on this estimate, the post harvest volume per acre would be comprised of 38% sawlogs and 62% pulpwood. The proposed treatment results would result in a 5.5% increase in sawtimber volume and a 3.1% decrease in pulpwood volume. Unfortunately the 1999 whole tree harvest did not achieve even this minor improvement.

The stand was marked to remove 37% of the total basal area and about 30% of the basal area in the main crown canopy. However, a post harvest survey of the portion of the stand treated in the whole tree operation demonstrated that the treatment diminished stand quality and reduced stocking below optimum levels for timber production. The negative impact of the harvest was cause in part by cutting of unmarked trees and logging damaged to residual trees. Thirteen percent of the residual trees and 16% of the basal area in the main crown canopy were damaged.

Storm damage occurred in both the cut and uncut areas after the harvest. The wind damage in the untreated portions of the stand consists of small pockets of blowdown, while the harvested section experienced more extensive damage because of lower post harvest stocking levels. In the harvested portions of the stand, 29% of the residual basal area and 48% of the residual trees are in the suppressed crown class, which are unlikely to respond vigorously to release. Of 160 trees per acre that remain in the main crown canopy only 141 are considered acceptable growing stock from which timber can be produced. Of these remaining trees, only 84 currently contain board foot volume, so the ability of the stand to support periodic harvests and generate revenue has been severely compromised.

The harvest generated 2,470 board feet per acre and 29.5 tons of cord wood per acre. The gross stumpage for pulpwood and chip stumpage was $0.50 per ton. The net stumpage is calculated by deducting marking fees of $0.40 per ton and commission of 12% of the gross ($0.50), or $0.06 per ton, leaving $0.04 per ton net stumpage. The timber tax is the landowners' responsibility and ranges between $0.05 and $0.10 per ton. The landing cost attributable to the pulp and chip volume is about $0.80 per ton. This results in an approximate net stumpage of negative $0.8l per ton, or $24.30 per acre.

The stumpage received for the sawlogs on this chipping job was less than the stumpage that could have been realized by conducting a sawlog harvest. The reduction in sawlog stumpage could range from $15 to $25 per MBF, or a loss of $36 to $60 per acre. Additionally, estimates of the cost of logging damage to crop trees, the reduced of stocking levels below the optimum levels, and wind damage losses suggest the cost of the whole tree harvest operation ranges from $122 to $172 per acre. In contrast, sawtimber and cord wood sales generated $142 per acre income.

Alternative Recommendation for Treatment
Instead of a whole tree chipping operation, the stand could have been treated with a pre-commercial thinning that removed about 25% of the basal area per acre and retained between 170 and 175 square feet of basal area per acre. Under this scenario all trees that contained sawlogs would have been retained along with all trees with the potential to produce saw logs. The mean stand diameter would increase to 9.6 inches, a greater increase than achieved by the whole tree removal treatment. Additionally, tree species beside white pine would have been retained for diversity, wildlife habitat and structural integrity. The cost of pre-commercial weeding and thinning this type of stand would range from $180 to $220 per acre.

This case study shows the potential difference between written plans and harvest implementation. Moreover, the whole tree chipping operation had a detrimental impact on the residual stand. Physical damage to remaining trees and reductions in acceptable growing stock reduced the landowner’s options for commercial harvesting in the future. In this case, pre-commercial forest stand improvement may have been preferable to biomass removal.

• Post Harvest Evaluation Report