Transcript Regeneration of Oak and Northern Hardwood Forests in

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, fireprone 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 Composition
Uncut Northern Hardwood Forest
Relative Density (%)
100
90
80
Acsa
Osva
70
Fagr
Prse
60
Fram
Tiam
50
Quru
Ulam
Acru
40
30
Amel
20
10
0
Rich Ecosystems
Dominant Overstory
Moderate Ecosystems
Rich Ecosystems
Moderate Ecosystems
Subdominant Overstory
Rich Ecosystems
Understory
Moderate Ecosystems
Species Composition
Clearcut Northern Hardwood Forest
Relative Density (%)
100
90
80
Acsa
Osva
Fagr
Prse
Fram
Tiam
Acru
Prpe
70
60
50
40
30
20
10
0
Rich Ecosystems
Dominant Overstory
Moderate Ecosystems
Rich Ecosystems
Subdominant Overstory
Moderate Ecosystems
Rich Ecosystems
Understory
Moderate Ecosystems
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.