Allegheny River Islands Wilderness - Random Thoughts   Edward Frank
  Sep 19, 2007 17:36 PDT 

Some random thoughts considering the distribution of species we found on
the various islands of the Allegheny Islands Wilderness.

Edward Frank, September 19, 2007


Islands in rivers are by nature ephemeral. They come and go. Rivers
are dynamic. This can be seen in rivers like the Mississippi where
remains of paddlewheel boats are found in fields miles from the present
river course. In rivers like the Allegheny the situation is somewhat
different. It isn’t just that the river is much smaller in scale, but
it is incised into the landscape and not free to wander about a broad
floodplain. Thompson Island is known from historical accounts dating
from the Revolutionary War. The age of these islands can be seen
reflected in the age of the trees found growing on them Some of the
bark and physical characteristics of individual specimens speak of great
individual age. The ancient slippery elm and red oak on Thompson Island
and Butternut on Baker jump out in that regard. The sycamore and silver
maple have reached immense size. The hawthorns normally are regarded a
small shrub while here they reach tree size comparable in size to those
found anywhere in the nation. Who knows how old they may be?

 Air Photo of R. Thompson Island

The islands do show signs of the dynamic nature of their environment.
Along the shores bank erosion can be seen. Sand bars are building in
the river channels. In the islands themselves are the remnants of water
channels that still flow during high water cutting the larger island
mass into smaller segments. In drier times these channels contain
inlets and isolated oxbow lakes and swamps. I am sure that some of the
smaller island fragments occasionally rejoin and separate from the
larger islands during the larger course of time as separating channels
infill and are opened again. The longer term effects of the Kinzua
Reservoir on the stability of the islands in the wilderness is unknown.

If we assume the islands in the Allegheny Islands National Wilderness
are all old and similar in age then we can expect certain patterns in
the species diversity found on the islands: 1) Larger islands would be
expected to have more species diversity than smaller islands; 2) Islands
with greater elevations would be expected to have a higher diversity; 3)
Islands with signs of greater stability would be expected to have a
greater diversity. The second factor that will dramatically affect the
diversity noted is the thoroughness with which the islands are examined
for different species. Those islands that were only visited for short
scout trips or for just measuring tall trees will likely reflect a lower
diversity than those examined in more detail. This artifact does not
reflect true diversity, just that observed by visitors.


Major islands included in the wilderness include: 

Seven islands in the Allegheny River, totalling 368 acres, are part of
the Allegheny Islands Wilderness. All are alluvial in origin, which
means they were formed by water-carried deposits of sand, mud and clay.
They are characterized by river bottom forest trees such as willow,
sycamore and silver maple. The islands are located between Buckaloons
Recreation Area and Tionesta, PA. They are:
· Crull's Island (96 acres) has large old river bottom trees.
· Thompson/s Island (67 acres) The only Revolutionary War battle in
northwestern Pennsylvania occurred on this island. It has an
exceptionally fine riverine forest.
· R. Thompson's Island (30 acres)
· Courson Island (62 acres) The island may be viewed from the Tidioute
· King Island (36 acres) has good riverine forest with many trees 35-50
inches in diameter.
· Baker Island (67 acres) stood in the path of one of the two tornadoes
which crossed the Forest on May 31, 1985. Most of the trees were blown
over in the storm.
· No Name Island (10 acres) is about half river-bottom trees and half
dense undergrowth.

In addition to these islands as part of this initial examination
Stewards Island, owned by U. S. Forest Service and part of Allegheny
National Forest, and Fuelhart Island. Apparently privately owned were
included in the survey. We landed on Stewards Island and measured
several trees. Some trees on Fuelhart Island were noted as we floated
past in a canoe, but we did not land. located

Background Information

Crull Island was explored by Dale Luthringer in September 7, 2004. He
wrote of his trip (Sept 27, 2004)
The report read in part: “Decent sized sycamores jumped into view
almost immediately. Most ranged from 7-9ft CBH with heights that maxed
in the upper 120's. I was also delighted to measure my first naturally
grown silver maples in the state. I continued downriver in the middle of
the island and soon found
a very nice sycamore (13.4ft CBH x 123.7ft high) and some respectable
sugar maples. There was a small section of old trees showing old growth
characters: (staghead branching, balding and deep fissured bark
characters, some large CWD). There was a slippery elm here that had such
deep furrows that I first that it was a cottonwood. I'd put some of the
hackberry and slippery elm here to over 100 years. Select N. red oak,
white ash, sycamore, and sugar maples probably went over 150, They
appeared to be growing fast in such rich depositional soils. The
surprise of the day were the hackberry that were located on the island.
It is the oddest bark character I've seen to date and also my first
hackberry in the field since my dendrology days in college.” The full
report is available at the link above.

King Island was previously visited by Dale Luthringer in June 21, 2005. The
report reads in part: “The peninsula and King Island both have a nice
river bottom forest that would be characteristic of much of the
Allegheny River watershed directly along its banks. The most abundant
and canopy dominant tree was silver maple, followed closely by sycamore,
along with a scattering of white ash, American basswood, bitternut
hickory, and black locust that occasionally made it to the upper canopy
level. Slippery elm, and Crateagus sp. could be found sporadically under
the canopy dominants, with butternut out in open field like settings.”
The full report is available at the link above. 
(G. Whitney 8/28/01) Only two surveys of the Allegheny River’s islands
have been reported (Whitbeck, Hartman, and Brenner 1997; Walters and
Williams, 1999). King’s Island is fringed with canary reed grass
(Phalaris arundinacea) and black willow (Salix nigra). The interior of
the island can best be characterized as a savanna of large silver maple
and sycamore (Platanus occidentalis) and several other bottomland
species interspersed with glades of various composites Importance values
(rel. density + rel. frequency + rel. basal area/3 for the large (10+ cm
dbh) trees of the island are as follows: silver maple ( 56.2), sycamore
(18.2), white ash (5.1), bitternut hickory (2.8), black willow (5.2),
basswood (trace), red elm (3.3), peachleaf willow (2.4), black locust
(3.2), butternut (1.8), and hawthorn (1.6) (Walters and Williams, 1999).

Whitbeck, H.J., G.G. Hartman, and F.J. Brenner. 1997. Botanical survey
of two islands in the middle Allegheny River corridor. Journ. Penn.
Acad. Sci. 71(1): 3-9.

Williams, C.E., W.J. Moriarity, G.L. Walters, and L. Hill. 1999.
Influence of inundation potential and forest overstory on the
ground-layer vegetation of Allegheny Plateau riparian forests. Amer.
Midl. Nat. 141: 323-338.


The following table is a compilation of the trees reported from each of
the trips to Crull and King Island reported by Dale Luthringer from 2004
and 2005 respectively and the multi-day trips to the islands by Dale
Luthringer, Edward Frank, and Anthony Kelly from September 3-5, 2007.
From September 3 through 5, 2007 a series of trips to various islands in
the Allegheny Islands Wilderness was made to explore the islands
searching for large trees and to note the various tree species present.
On September 3, Dale Luthringer and Edward Frank visited Thompson island
via canoe from the west bank and spent several hours on the island
documenting the trees. They were joined that evening by Anthony Kelly.
On September 4th, Dale Luthringer, Edward Frank, and Anthony Kelly
started at Thompson Island and proceeded downstream to the boat access
at Tidioute. Islands were examined along the way including stops on R.
Thompson, Stewards, and Courson Island. A tall white pine was measured
from the canoe on Fuelhart Island, but a landing was not made. On
September 5th the same three people started at the West Hickory access
and proceeded downstream to the boat access at Tionesta. King was also
visited again and some of the original trees from Luthringer’s 2005
visit were remeasured and photographed and a few new trees species were
measured. Baker Island was the final stop for the day before proceeding
to Tionesta.

Table 1: Species by Island Compilation   

  Crull Thompson R. Thompson Stewards Fuelhart Courson King Baker
Sycamore x x x x x x x x
Silver Maple x x x x x x x x
Black Willow   x x x x x x x
White Ash x x x x   x x x
Bitternut Hckory x x x x   x x x
Basswood x x       x x x
Hawthorn (sp,)   x       x x x
Slippery Elm x x x x   x x  
Black Locust x x x x     x x
Hickory, Shagbark   x            
Sumac, Staghorn   x       x   x
Black Walnut   x   x        
Red Maple   x            
N. Red Oak x x            
Sugar Maple x x           x
Musclewood   x   x        
Black Cherry x x            
Hackberry x x           x
Black Birch       x        
White Pine         x      
Catalpa           x    
Silky Dogwood           x    
Cherry (sp.)           x    
Butternut           x x x
Pignut Hickory   x            
Yellow Birch               x


There are a number of species that found on virtually every island. In
the few islands these species were not found, I believe it is because
they were not documented rather than because they were not present.
These widespread species include:
Silver Maple
Black Willow
Slippery Elm
Black Locust
White Ash
Bitternut Hickory
Hawthorn (sp,)

 large mulit-trunked sycamore on Courson Island

Of these species several might be expected and are considered bottom or
wetland species. Sycamore, Silver Maple, and Black Willow are wet
loving species. In areas like these islands prone to flooding they are
the dominant species. Often as the trees are battered by floodwaters
and debris the stems are damaged. 

Multiple stem specimens of these
species are very common or even typical in the case of silver maple.
One large multi-stem silver maple included at least 7 trunks fused
together to form a basal mass 24 feet in girth. Slippery elm (Red elm),
Black locust, and 

thompson_silver1.JPG (142066 bytes)
 Multi-trunked Silver Maple

Basswood are also not totally unexpected. Basswood
does form multiple stems on occasion. One example on Baker island had a
small trunk snaking across the ground before curving upward to form an
upright trunk. 

baker08.JPG (80023 bytes) 
Basswood with top blown off by tornado - Baker Island

A large 10 foot plus circumference basswood was found to
be relatively short. When later viewed from the canoe it could be seen
that the tree was on the edge of the tornado damaged area and the top
had been blown off at a height of about 70 feet. I had not expected
that white ash, bitternut hickory, nor hawthorn would be a typical
species across all of these islands. 

Walter and Williams (1999) had cited Peachleaf willow as being present 
on these islands. It is difficult to distinguish from black willow. This area 
is on the very edge of the known range for the species. Normally it is 
found farther north and west of this area. There were a couple of unusual 
looking willows along the shore of the river noted while canoeing, but none 
were noted on the islands themselves. Perhaps a more detailed examination
would show that some of the willows encountered were peachleaf willow,
but for now the best identification is that of black willow. 

baker06.JPG (84241 bytes)
 Hawthorne on Baker Island

Dale Luthringer suggested some potential ages for the trees he first
encountered on Crull Island being in the 100 to 150 year range. It is
my impression that these trees may be significantly older than this
first impression. The only way to determine their age for sure will be
through dendrochronology. I am particularly interested in the ages of
some of the hawthorn trees on the islands. Some nondescript species
such as chokecherry and silky dogwood likely have a wider distribution
but were simply not noted on the other islands in the short visits.

Other species

Occurred only infrequently or singly on the islands. One in particular
of interest is the Northern Red Oak. Large specimens were found on
Crull Island and on Thompson Island, but not on any of the islands
farther downstream At the same time large examples of the species could
be seen along the shore of the river. This suggests that perhaps the
trees were present at one time on the islands but had been logged at
some time in the past. Similarly only relatively young black walnut
trees were found on any of the islands.

king05.JPG (110118 bytes)
 Butternut on King Island

Butternut was noted in Walter and Williams (1999) as a major component 
of the flora of King Island and one of the other forest service islands they 
examined. The species however was absent from or not noted from any of 
the upper islands. It was first noted farthest upstream as a single old tree 
on Courson Island. Dale Luthinger noted its presence on King Island in 2005, 
and additional examples were found on the Sept 2007 trip. The largest was a
nearly branchless tree 66 feet high, a small mound of a younger tree in
a grassland. Much of the southern end of Baker Island had been hit by
two tornados in 1985. Trees had been blown down. Now this area is
covered by a similar grassland with patches of trees. In this grassy
area are mounds of younger butternut trees, very reminiscent in form to
sumac clumps. I am wondering if these are root sprouts from larger
trees downed by the tornados? Similarly I am wondering if this large
grassy area in the central east shore of King Island is a result of a
wind disturbance from the same time period? The smaller butternut trees
are similar in size and form to those on Baker Island. Another point
that seems to support this root resprout idea is that one of the clumps
of butternut on Baker Island had a broken thick butternut trunk
approximately 7 feet cbh at its base, but otherwise seemed to be younger

Other single specimens of note include the Eastern White Pine on
Fuelhart Island. This could be seen from the canoe. The canoe was held
steady, while I measured the height. Allowing 7 feet for the height of
the base above the river yielded a height of 115 feet. This tree could
potentially have been planted, rather than growing naturally on the
island. The Yellow Birch was found on the far downstream side of Baker
Island. It was a triple stemmed tree that had been broken off at a
height of around twenty feet. Each of the three stems were
approximately 1 foot in diameter. It was a legitimate tree species for
the island. There were several other single specimens – no additional

One of the questions that need to be answered is how the “wilderness” is
fairing with the building of the Kinzua Dam in 1965? With the normal
flooding cycles removed from the process are the species composition of
the islands changing? Are those species helped by periodic flooding-
such as willow, sycamore, silver maple being replaced by those species
less flood tolerant? Are willows, sycamores, and silver maples actively
reproducing on the islands? 

Japanese Knotweed on southern end of Thompson Island

Certainly the ecosystems of the islands are
drastically compromised by the massive invasions of Japanese knotweed,
multiflora rose, Japanese barberry, garlic mustard, and Tatarian
honeysuckle. Natural vegetation is not reproducing in areas dominated
by these species. It is clear that in the channels which are
occasionally flooded these invasives have not managed to obtained a
strong foothold. In addition they tend to be less dominant at the upper
ends of the islands which are also more prone to occasional flooding.
At this point it is politically unlikely that these islands could be
periodically flooded to remove the exotic species and allow the native
species to again flourish. Much of the shoreline of the river has since
the construction of the dam been built up with series of camps and some
small businesses. Many of these properties would likely be flooded also
in any attempt to flood the islands. I feel this is what needs to be
done to restore them and that some accommodation needs to be reached.

Ed Frank

Re: Allegheny River Islands Wilderness   Kirk Johnson
  Sep 20, 2007 23:24 PDT 

  Islands in rivers are by nature ephemeral. They come and go. Rivers
are dynamic.

  The longer term effects of the Kinzua Reservoir on the stability of the
islands in the wilderness is unknown.

As an aside, one of the effects of the Kinzua Dam on the islands downstream
is to make them less ephemeral. One of the purposes of the Kinzua Dam is
flood control, so the Army Corps of Engineers regulates the downstream flow
from the Allegheny Reservoir to keep it relatively constant.

Before the dam, there were very high flows associated with the spring thaw
and ice breakup on the river. The high water carrying large chunks of ice
would race down the Allegheny River, scouring the banks and the islands
clean of a lot of sediment and vegetation. These high flows/ice flows do not
occur anymore, so the islands have grown/are relatively stable. Also, the
lack of scouring effect has allowed non-native vegetation to more easily
gain a foothold on the islands in locations.

Here's a paper on the subject if anyone is interested:

Cowell, C.M. and R.T. Stoudt. 2002. Dam-induced modifications to upper
Allegheny River streamflow patterns and their biodiversity implications.
Journal of the American Water Resources Association, vol. 38, no1, pp.

This study evaluates the streamflow characteristics of the upper Allegheny
River during the periods preceding (1936 to 1965) and following (1966 to
1997) completion of the Kinzua Dam in northwestern Pennsylvania.
Inter-period trends in seasonal patterns of discharge and peak flow at three
downstream sites are compared to those at two upstream sites to determine
the influence of this large dam on surface water hydrology. Climatic records
indicate that significant changes in annual total and seasonal precipitation
occurred over the twentieth century. Increased runoff during the late summer
through early winter led to increased discharge both upstream and downstream
during these months, while slightly less early-year rainfall produced minor
reductions in spring flood peaks since 1966. The Kinzua Dam significantly
enhanced these trends downstream, creating large reductions in peak flow,
while greatly augmenting low flow during the growing season. This reduction
in streamflow variability, coupled with other dam-induced changes, has
important biodiversity implications. The downstream riparian zone contains
numerous threatened/endangered species, many of which are sensitive to the
type of habitat modifications produced by the dam. Flood dynamics under the
current post-dam conditions are likely to compound the difficulties of
maintaining their long-term viability.
Re: Allegheny River Islands Wilderness Floods/Stability  Edward Frank
 Sep 22, 2007 16:57 PDT 


There is no doubt that the change in the flood patterns have adversely
impacted the viability of the island ecosystem and allowed the invasive
species to take over such large portions of them. The dam also likely has
allowed less flood tolerant native species to gain footholds on the islands.
The idea that this makes the islands less ephemeral is a misconception. I
don't have any references here to cite, but someone with access the
geomorphology journals can surely find some.

In a typical flood there is a period during the rise of the flood where
there is a large amount of erosion. Channels are cut deeper, edges of banks
are eroded, upper ends of islands are cut into. As the flood passes and the
water recedes, the materials carried by the river is redeposited. The
channels that are deepened are filled to essentially the same depth as
before. Where banks were eroded before, now other areas a little farther
down get bar deposits. The upper end of islands get some deposits and the
lower ends are lengthened. So the islands slowly creep downstream, but are
not destroyed by the flood events. With the reservoir, the water in spring
is discharged at higher rates than in dry periods, so there is some erosion
taking place of the banks, and islands. When the flow is reduced however
there is not deposition because the water coming from the reservoir is not
carrying any sediment. The net effect is one of simple erosion in the area
immediately below the dam. It is not as dramatic as a spring flood, but it
is unidirectional.   The Allegheny Islands Wilderness Area is likely too far
downstream to be impacted by this first consideration. The water will have
ample time to pick up sediment before it reaches the islands. The size
distribution of the sediment will change because the peak flow velocities
will have changed... but the natural process should be functioning in the
Wilderness area.

More importantly for the Allegheny Islands is the fact that the floods
themselves are not taking place. It is these large floods that overwhelm
the capacity of the main channel to carry all of the water, and the capacity
of the river to transport all of the sediment, that causes multiple channels
to form, that causes the islands to form. It is the reworking of these
multiple channels every year by floods that keeps them open. In a steady
flow situation, like is artificially maintained by the reservoir, the
secondary channels will slowly infill, These will no longer be islands.
This process is slowed by floodwaters coming in from side tributaries, and I
hope this will be sufficient to keep these islands separate from the
shoreline. During the relatively low flow period Dale, Anthony, and I
canoed down the river, there isn't much water around several of these
islands and they seem to be almost on the verge of becoming just another
bump on the shoreline. Ironically a more dynamic flood regime results in a
longer term existence for midstream islands.

Ed Frank