Regeneration of Oak and Northern Hardwood Forests in Northwestern Lower Michigan

School of Natural Resources & Environment

McIntire-Stennis Program

B. V. Barnes, D.R. Zak

Graduate Student: Anna T. Williams

October 28, 2002

Rationale• Oaks. Upland oaks evolved in relatively dry, fire-prone

ecosystems. • In presettlement time mixed oak and pine forests

dominated many of the dry and dry-mesic ecosystems of northern Lower Michigan.

• Although oak overstory trees are present today, their regeneration is at risk due to a combination of fire exclusion and herbivory by deer.

• Northern Hardwoods. Northern hardwood forests do not require fire for persistence, but high deer populations may significantly limit their regeneration as well.

Objective

To assess the current regeneration of oak and northern hardwood forests in three

experimental areas as the basis for

management recommendations.

Approach

• Oak regeneration was examined in a USFS administrative study on two ecosystems (four sites per ecosystem) where seven silvicultural treatments were applied.

• Northern hardwood regeneration was studied in two ecosystems where small clearcuts and control treatments had been established in 1991.

• Baseline plots were established in a 90-ha stand that had been patch-cut in 2001-2002.

Results: Oak• The study of treatments to secure oak regeneration

revealed that despite deer browsing, black and white oak regeneration was occurring in many areas of high light intensity due to natural gaps and small clearcuts.

• Thinning was too light to be effective, and a single burn not only failed to promote oak regeneration but often set back existing regeneration.

• Herbicide treatment changed the vegetation markedly and is totally undesirable.

• The poorest site, with the most open canopy, exhibited the most abundant oak regeneration.

Oak Regeneration in Gap

Results: Northern Hardwoods• The parent Northern Hardwood stand resulted from sprouting of

cut trees at a time when deer populations were very low.

• In contrast, 10 years after clearcutting, little northern hardwood regeneration (beech, sugar maple, basswood) is present in either ecosystem due to severe deer browsing.

• Tree species reaching sapling size are mainly opportunistic species, Prunus serotina and Ostrya virginiana.

• Differences were observed among ecosystems in tree species composition and herbaceous (Rubus) cover.

Uncut Northern Hardwood Forest

Clearcut Northern Hardwood Forest:Rubus spp. and Ostrya virginiana

Species CompositionUncut Northern Hardwood Forest

Relative Density (%)

0

10

20

30

40

50

60

70

80

90

100

Rich EcosystemsDominant Overstory

Moderate Ecosystems Rich EcosystemsSubdominant Overstory

Moderate Ecosystems Rich EcosystemsUnderstory

Moderate Ecosystems

Acsa

Osva

Fagr

Prse

Fram

Tiam

Quru

Ulam

Acru

Amel

Species CompositionClearcut Northern Hardwood Forest

Relative Density (%)

0

10

20

30

40

50

60

70

80

90

100

Rich EcosystemsDominant Overstory

Moderate Ecosystems Rich EcosystemsSubdominant Overstory

Moderate Ecosystems Rich EcosystemsUnderstory

Moderate Ecosystems

Acsa

Osva

Fagr

Prse

Fram

Tiam

Acru

Prpe

Results: Northern Hardwoods Patch Cutting

• Although large patch cutting provides openings for new seedlings of northern hardwood species, opportunistic species are likely to dominate these areas for decades.

• Advanced northern hardwood regeneration is unlikely to play a role in regeneration in the patches or in the smaller uncut areas.

Large Patches Cut in Northern Hardwood Forest

Conclusions

• Oak: Although broad prescriptions failed, keen attention to species-site relationships of these ecosystems could have secured adequate

regeneration in many places.

• Northern Hardwoods: Due to today's high deer populations, clearcutting fails to provide timely regeneration of northern hardwood stands. It favors opportunistic species that will preclude acceptable stocking of northern hardwoods for decades.

Overall Conclusions

• Evidence from these experimental studies illustrates the severe effects of fire exclusion and high deer populations on forest regeneration. Conventional vegetation management is unlikely, under current conditions, to provide an easy, short-term resolution to these problems. Better ecological understanding of site-species interactions, coupled with local deer herd control, can be expected to yield more encouraging results.