Clover Hill Tree Farm

 

1. Name - Clover Hill Tree Farm

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

Land Use History
Northern hardwoods dominate the uplands of the Connecticut River watershed. Elevations on this property range from 1,200 to 1,700 feet above sea level. Sugar maple of above average quality is the principal species present. Soils are deep, well-drained, and formed from calcium-rich bedrock and glacial till. The area was nearly completely cleared for agriculture in the late 1700s, and heavily pastured for sheep until the mid-1800s, when some land reverted to forest. The remainder was used for subsistence dairy farming until the early 1970s, when agricultural use ceased in most places. Hillside pastures were abandoned and the forest began to re-establish. While soils are still rich, they are commonly depleted of surface organic matter and are somewhat diminished in quality from their pre-settlement condition.

General Pre-Harvest Forest Conditions
The area subject to this biomass harvest consisted of 50 to 60 acres of abandoned pasture that reverted to a mix of scattered, large, open-grown eastern white pine and sugar maple wolf trees over well-established sugar maple saplings and poles. The wolf trees were 50 to 200 years old, while hardwood regeneration was 20 to 35 years old. Two small areas of pasture were planted with Scots pine approximately 30 years ago. The white and Scots pine were repeatedly and heavily damaged by the white pine weevil, which resulted in most trees having multiple, misshapen, heavily-branched stems. Quality was extremely poor, and the potential for value growth was negligible. Pine stocking of this kind constituted approximately half of the total basal area.

Management Objectives and Options
The principal objective was to either convert the abandoned pasture to permanent woodland openings or to speed succession to a healthy and financially productive forest. In the areas designated to remain forested, objectives were rapid establishment of a native species mix, followed by long-term management to produce a sustainable supply of high-quality sugar maple sawlogs. To achieve these objectives, it was deemed necessary to largely remove the white and Scots pine from the site. However, the problem with removing the pine, which constituted approximately half of the above-ground biomass, was that it would constitute a loss of organic matter from an already depleted system. Such nutrient loss could have long-term negative impacts on site productivity. But if the pine, which was quite healthy despite being of low quality, was left on site, it was likely to dominate the forest for the foreseeable future, prolonging the transition to a native species mix and providing essentially no financial return during that period.

Silvicultural Treatments
Quality dictated that the pine would be too expensive to process as pulpwood, and the percentage of trees with logs of any grade was negligible. Large-scale girdling would be a safety issue, and trees were so large and numerous as to potentially be damaging to the hardwoods as they broke apart over the years. The options were ultimately narrowed down to either doing nothing or conducting a targeted biomass harvest in combination with as much girdling as was acceptable. Finally, the harvest/girdling option was decided upon. Pre-harvest pine stocking varied from 10 to 150 square feet per acre with two common situations: (1) total basal area less than 80 square feet per acre with a third to half of that consisting of a few large, very rough pines over dense, good quality, hardwood saplings and poles; or (2) areas of higher stocking (120 to 150 square feet per acre) dominated by low-quality pine. In the areas where pine and hardwoods were mixed, concentrations of pines were targeted for harvest, but individual pines or isolated groups were more commonly girdled. This silviculture treatment could be termed "release" or perhaps "species conversion," in which removal of heavily-weeviled, white pine overstory super dominants was intended to release well-established northern hardwoods in the sapling/pole size groups. In other areas, where regeneration was not well-established, group selection was chosen to remove unacceptable growing stock and provide space for natural regeneration. The contractor created nine openings, of approximately 1 to 3 acres each, for regeneration.

Implementation
Work was carried out by Limlaw Pulpwood, Inc., a local contractor. A feller-buncher cut the trees, and a single grapple skidder brought them to the landing, where the logs were sorted out, and chipwood was piled using a loader/slasher. Every few days, a chipper would be brought in to chip the pile, resulting in 12 to 15 chip vans per chipping entry. Four chip vans serviced the chipper, with all chips being sold to Ryegate Power Station, a wood-fired power plant in East Ryegate, Vermont. The Ryegate plant's maximum daily wood consumption was 700 green tons, and energy production of the steam turbines was 20 MWe (70 million Btu/h).*

Of the 50 to 60 acres that were worked, 17 acres were cleared as permanent woodland openings and the remainder were harvested and/or girdled. Total harvest volume consisted of about 2,100 tons of biomass chips and 9.3 MBF of white pine logs. Approximately 300 additional large trees were girdled. White pine logs were few and far between, and stumpage prices averaged about $60 per MBF across all grades. The total stumpage for biomass chips and logs was just under $3,000.

Post-Harvest Stand Condition
The post-harvest stand is dominated by young hardwoods of moderate to good quality with the basal area ranging from 30 to 60 square feet per acre in most areas. This is lower than the optimum, but represents nearly all of the hardwood that was present pre-harvest. Rapid growth response is expected, as is regeneration of a new age cohort of primarily sugar maple and white ash. Three group selection areas of approximately ¼ acre, ½ acre and 1 acre were created, where the basal area is near zero. Regeneration in the form of a mix of hardwood species dominated by sugar maple, white ash, eastern hop hornbeam, and American beech is expected to become established in these openings over the next 10 to 15 years.

* Note: Bergman, R., and J. Zerbe. 2008. Primer on Wood Biomass for Energy. USDA Forest Service, State and Private Forestry Technology Marketing Unit, Madison, WI.
http://www.fpl.fs.fed.us/tmu/resources/