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Berkshire Valley Wildlife Management Area Forest Management Activities
1991 - 2011

by Miriam Dunne, Northern Region Habitat Biologist
Bureau of Land Management
April 30, 2011

Wildlife Management Areas (WMAs) in the northern part of the state provide nearly 50,000 acres of woodland wildlife habitat, much of it in mid to later stages of succession. It is important to have both early successional forest and older growth forest on the landscape. To that end, forest management activities have been undertaken at Berkshire Valley WMA, located in Roxbury Twp., Morris County, since the early 1990s to increase the amount of early successional forest present for species like ruffed grouse, chestnut-sided warbler and prairie warbler.

A cooperative effort was undertaken between the NJ Division of Fish and Wildlife's Bureau of Land Management, the Ruffed Grouse Society, and the NJ Division of Parks and Forestry to diversify age classes of forest stands. Management activities were intended to set back succession in patches in the 80 - 120 year old oak-hickory forest. In the course of 20 years, approximately 70 acres of forest patches have been harvested and have regrown, producing a high stem density cover type that is valued by many species of wildlife.

Berkshire Valley WMA is more than 2000 mostly forested acres. Like all of New Jersey, Berkshire Valley was cut over extensively during the mid to late 1800s for sawlogs, fuel and charcoal production. Numerous wetlands are scattered throughout including vernal pools and depressions associated with the Rockaway River which cuts through the center of the WMA. A few gravel "borrow pits" are interspersed throughout the eastern edge of the property, and power line rights-of-way intersect the southern and eastern edges of the WMA. Low density housing surrounds the area. Route 80 bounds the WMA to the south.

The Management Plan

In the early 1990s, the Ruffed Grouse Society funded the development of a management plan by a consulting forester which was approved and implemented by the NJ Forest Service. The plan was designed to produce a mosaic of forest stands in 4 blocks over a 20 year period so that a checkerboard pattern of various stand ages would be produced. Over the course of 20 years, the plan called for 4 harvests of about 23 acres, for a total of 92 acres of early successional habitat being created over time.

Twenty year old stand of oak, birch and maple
Twenty year old stand of oak, birch and maple
Click to enlarge
Unevern age stand
Older, uneven age stand in foreground with younger, dense stand in background
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In 1991, firewood and timber were harvested on 22 acres in 5 blocks. The blocks ranged in size from 1 to 12 acres. This harvest was done in September resulting in good regeneration of oak, black birch, red maple, shrubs, forbs and grasses. These blocks, now 20 years old, have reached the stem exclusion phase of development and are almost at the end of their prime as early successional habitat.

A second round of harvesting was done in 1996 through 1997. As with the initial cuts, these blocks ranged from 1.5 to 7 acres. Good regeneration of hardwoods was the result with acceptable levels of deer browse and few invasives in the understory.

The next round of harvesting was not done until the winter of 2008. Care was taken to leave adequate mast trees (those producing acorns and other nuts) on the periphery of the cuts to enable oaks to seed in. Tree tops left in the blocks provide coarse woody debris which is beneficial to a number of insects (and animals that eat insects). They also form a temporary barrier to deer to discourage browsing on tree seedlings. Cavity trees and some mast trees were left standing in the middle of the even-aged blocks.

Harvesting done in the winter reduces run-off and minimizes the spread of invasives through mud on equipment. Even so, some invasive exotic vegetation is present in the newly cut blocks (as it is everywhere in New Jersey). Some invasive plant experts believe that Japanese stiltgrass can become shaded-out of the developing understory. Other invasives like garlic mustard and Japanese barberry tolerate shade well and are much more persistent.

At the end of 3 growing seasons, the blocks appear scrubby or brushy. While this might be considered unsightly to some, these areas contain a great diversity of young trees, shrubs, brambles, vines, forbs, grasses and sedges. Small deer exclosures (75' x 75') were installed in two of the blocks to look at vegetation diversity in and out of the blocks, as well as the total height of tree species. The vegetation diversity study was started in 2010 and data will be collected for comparison in 2015 and 2020.

 

Open canopy allows sunlight to forest floor
Opening the canopy to sunlight stimulates the growth of seedlings present before the harvest (like oak and beech) and releases shade-intolerant species like birch and ash.
Click to enlarge
Regenerating stump sprouts
Stands cut in 1996 are regenerating from stump sprouts (American chestnut shown above), from seedlings present in the stand before harvest, and from seeds that have germinated after harvest.
Click to enlarge
Deer Management

 

Deer management is an important component of forest health and regeneration. Berkshire Valley WMA is located within Deer Management Zone (DMZ) 6, Regulation Set 3A, which allows more than 120 days of deer hunting throughout six deer seasons (seethe Hunting Digest for details). Habitat and land use varies greatly within this zone, from highly populated suburban areas along the Route 80 corridor on its southern boundary to the forested uplands along its northwestern boundary.

The estimated density of the huntable portion of the herd in Zone 6 was 31 deer per square mile in 2007. This is considerably lower than the estimated densities in the highly productive agricultural DMZs where 40+ deer per square mile are thought to be present. It is also considerably more than the single digit density estimates for the nutrient-poor habitat of a Pinelands zone.

The average deer harvest for the past five years in Zone 6 was 5 deer per square mile, compared with an average harvest of 26 deer per sq mile in agricultural areas, and a harvest density of less than 2 deer per sq mile in a Pinelands zone. Hunting regulations have been consistent throughout this time period, but Zone 6 has been proposed to be added to a new regulation set which would add three more weeks of hunting to the Fall Bow season and increase antlerless bag limits for all bow seasons to unlimited from 2 deer. Even so, existing deer hunting pressure at Berkshire Valley in combination with opening the forest canopy has resulted in the successful regrowth of trees producing a matrix of stand ages.

Deer exclosure show deer impacts
Two deer exclosures were installed to look at deer impacts on regenerating stands.
Click to enlarge

 

Breeding Birds

Breeding bird diversity in and around these harvest areas is typical of this area. A breeding bird survey was conducted during June of 2008 and found 18 species, including representatives that prefer "interior forest" for nesting (like wood thrush and scarlet tanager), those which require scrub/shrub (prairie warbler), and species which need a well developed understory (worm eating warbler, black-billed cuckoo). Though many birds that nest in "interior forest" will not nest in the regenerating cuts, this habitat is important to them for foraging after the young fledge as well as during migration. The great abundance of berries and insects on the plants in the cuts makes them a desirable habitat type.

Grouse surveys done during April and May of the last 2 years have not been fruitful. At one time grouse were fairly common on Berkshire. It is possible that there are not sufficient source populations in close proximity to expand into available habitat. It could be that there is not yet enough early successional habitat in this area. Localized predation from cats, raccoons, and other predators may have an impact. Disturbance from illegal ATV and dirt bike activity could thwart nesting. It likely is a combination of factors.

The Future

Two more rounds of timber harvests are planned under the current management plan. These cuts are scheduled to take place in 2013 and 2018. There seems to be adequate deer hunting pressure based on the amount of browse observed in the understory, and the types of plants that can be found there, despite the fact that they are preferred by deer (e.g. maple leaf viburnum). Spreading invasives are a concern, but winter harvesting and greater attention paid to washing equipment prior to entering the WMA will be tried. Spot herbiciding in stands prior to harvest to kill plants like Japanese barberry will be done as needed as a preventative measure.

Berkshire Valley provides an example of how professional forest management is used successfully as a tool to create wildlife habitat. The "no-action" alternative (no management activity) will not change the fact that invasives are likely to be present in the future stand. The result of no action will be little regeneration of trees like oak that need an open canopy and sunlight reaching the forest floor in order to thrive. Without oaks in future stands the outlook for wildlife that depend on oak is bleak. Tolerating some invasives may be necessary in order to achieve a diversity of forest successional stages that is so crucial to forest health and wildlife diversity

Area of regrowth
Regrowth in areas cut in 2008 has resulted in dense, diverse assemblages of plants.
Click to enlarge

* Data on deer populations and harvest from Carole Stanko, Deer Research Project Leader, NJDFW.

MORE INFORMATION

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Last Updated: April 30, 2011