Forest Service 

Northeastern Forest 

Experiment Station 

Research Paper NE-688 

Migration of Tree Species 

in ~ew England I 

Based on Elevational 

and Regional Analyses 

Bale S. Solomon 

William B. Leak 
Abstract 

Concerns over possible increases in global temperature have renewed interest in 

the detection, measurement, and analysis of tree-species migration. Previous work 

has consisted mostly of computer simulations of changes in species ranges. In this 

study, two complementary approaches were used to examine movements of tree 

species in New England, where there is a documented increase (at Hanover, New 

Hampshire) in mean annual and summer temperatures of about 2OC since 1835. We 

used advancing-front theory to examine age trends over distance and elevation in 

undisturbed stands on Haystack Mountain in New Hampshire. Then we examined 

changes in species occurrence over a 24-year period on USDA Forest Service 

survey plots throughout Maine. On Haystack Mountain, well-defined stationary fronts 

(no movement) were identified for red spruce (Picea rubens Sarg.) and beech 

(Fagus grandifolia Ehrh.); these occurred at the borders of distinct changes in site 

conditions, which serve as temporary obstacles to species' movements. A 

catastrophic front was depicted for sugar maple (Acer saccharum Marsh.): no 

established understory stems less than about 100 years old were evident at 

elevations above 720 m on a site complex composed of shallow bedrock 

interspersed with deeper till. A constant, very slowly moving advancing front was 

exhibited by hemlock (Tsuga canadensis (L.) Carr.). In Maine, white pine (Pinus 

strobus L.), and balsam fir (Abies balsamea (L.) (Mill.) decreased significantly in 

average latitude and elevation over the 24-year period; average species' elevations 

decreased by only 16 and 7 m, respectively, while latitudes decreased (southerly) by 

about 0.1 and 0.04 degrees (1 1.3 to 4.5 km). The other significant change was an 

increase (westerly) in longitude of sugar maple by about 0.1 degree (6.9 km). 

Succession--not climatic shifts--following land use changes or cutting probably was 

responsible for these trends for sugar maple. Forest managers should be aware that 

natural succession as influenced by disturbance, land use, and site currently is the 

dominant influence affecting species changes in New England forests. At present, 

potential ranges of the major species in terms of elevation and regional position 

appear stable and in alignment with known site requirements. 

The Authors 

DALE S.SOLOMON is Project Leader of a work unit engaged in research on 

methods for measurement, analysis, and modeling of forest growth and structure at 

the Northeastern Forest Experiment Station in Durham, New Hampshire. He 

received a B.S. degree in forestry from Pennsylvania State University and joined the 

U.S. Department of Agriculture in 1962 after receiving an M.S. degree in 

mensuration and statistics from Yale School of Forestry, and a Ph.D. degree in 

forest growth modeling from the University of Maine. He is currently conducting 

research on forest ecosystem modeling for forest types in the Northeastern United 

States. 

WILLIAM B. LEAK, research forester with the Northeastern Forest Experiment 

Station at Durham, received B.S. and M.F. degrees from the State University of New 

York at Syracuse. He ioined the Northeastern Station in 1956 and is conducting 

research on site evaluktion, silviculture, and ecology of northern hardwoods. .- 

Manuscript received for publication 9 November 1993 

USDA FOREST SERVICE 

5 RADNOR CORP CTR STE 200 

P.O.BOX 6775 

RADNOR, PA 19087-8775 

July 1994 
Introduction 

Concerns over global climate change have led to renewed 

interest in the detection and analysis of tree-species 

migration. Most previous work and most inferences on the 

projected effects of climate change have been concerned 

with historical movements based on the pollen record and 

computer models of climatic change coupled with 

hypothesized species responses (Brubaker 1986; Davis and 

Zabinski 1989; Gajewski 1987; Peters 1990; Pastor and Post 

1988; Solomon and West 1987). Average increases in 

temperature of 1.5Oto 4.5'~ in Eastern North America have 

been predicted, resulting in simulated tree-species range 

shifts of 500 to 1,000 krn within periods of 200 years 

(Overpeck et al. 1991) or even as short as 50 to 100 years 

(Peters 1990). There is one documented increase of 1.7' and 

2.2OC in mean annual and mean summer temperature, 

respectively, since 1835 in Hanover, New Hampshire. This 

change was hypothesized as being responsible for the 

elimination of midslope red spruce (Picea rubens Sarg.) in 

northern New England and an upward displacement of the 

coniferous/deciduous elevational boundary by about 400 m 

(Hamburg and Cogbill 1988). 

However, since there have been no attempts to directly 

measure species migration in New England, we conducted a 

study of tree-species movement based on two approaches: 

advancing-front theory (Leak and Graber 1974; Solomon et 

al. 1990) in stands on Haystack Mountain, New Hampshire, 

and remeasurement analysis of USDq Forest Service 

inventory plots throughout Maine. The objectives of this study 

were to search for incipient migration of species and to 

determine the methodology, including the effects of site and 

the influence of managed versus unmanaged forest 

conditions. 

Under the first approach, age trends were measured in old, 

uncut stands along a transect up Haystack Mountain in New 

Hampshire. The objective was to search for relationships of 

maximum and minimum tree age over'elevation or distance 

that would reflect species movement, an approach referred to 

as advancing-front theory. The second approach was to 

analyze changes in species occurrence over an average 

period of 24 years on Forest Service survey plot records 

taken throughout Maine, an area of 89 percent forestland that 

has been mostly managed or cutover in the past. If there has 

been a rise in mean New England temperatures of 2OC, and 

if the previous computerized range changes are accurate, a 

remeasurement period of 24 years should detect incipient 

movement, especially since the management disturbance 

could hasten migrational trends by reducing competition for 

space and light. The first approach provides a means for 

examining the details of species migration, including the 

influence of site, without complications from cutting and past 

land-use influences. The second approach deals with overall 

regional implications. 

Advancing-Front Theory 

It has been suggested that species movement will be 

reflected by an advancing front, that is, where seedlings and 

young trees are positioned in a sequential pattern away from 

a stand of mature trees (Leak and Graber 1974; Solomon et 

al. 1990). The concept of "front" applies to the main 

population of a species, ignoring isolated individuals. The 

best places to search for these fronts are in essentially 

undisturbed stands of tolerant species near the climatic limits 

of the type, or, better, on mountain slopes where the cover 

type or any of its component species is limited in elevation by 

climatic factors. If regular movement of a species is taking 

place at a constant rate, maximum age of the species plotted 

over distance from the mature stand (or elevation) should 

form a straight descending trend line or front (Fig. 1A). The 

rate of movement would equal llslope of age regressed over 

distance. Likewise, increasing or decreasing rates of 

movement would be evidenced by concave- upward (Fig. 1 B) 

or concave-downward (Fig. 1 C) trends; the rate of movement 

would equal the inverse of the tangent at any point on these 

curves. Retreating fronts would be similarly defined (Figs. 

1 D-F) using the minimum age of the species. Incipient fronts 

(Fig. IG), the very early stages of species movement, would 

be indicated by an ageldistance trend line that spans a short 

period. Where environmental change triggers a massive 

disappearance (or appearance) of regenerating stems, a 

catastrophic type of front (Fig.1 H) seems likely. Figure 1 H 

represents a sudden areawide cessation of regeneration. 

Continued repetition of this process would produce a 

sequential step-like pattern that could be used for predictive 

purposes. 

Where no movement is taking place, a stationary front would 

occur (Fig. 1 I) where maximum and minimum ages occur and 

end at the same point on the landscape. The relationships in 

Figure 1 seem fairly logical, but there are many questions 

about the acquisition and interpretation of data, including 

sampling methods, variability, site relationships, and factors 

influencing species longevity. 

Methods 

Haystack Mountain 

Haystack Mountain borders the Bartlett Experimental Forest 

in the White Mountain National Forest, New Hampshire. A 

series of plots was taken on the south-facing slope of the 

mountain along the marked boundary of the Experimental 

Forest. Beginning at an elevation of 543 m, plot locations 

were established every 30.5 m in horizontal distance, moving 

upslope to an elevation of 738 m, and then every 15.2 m, 

moving upslope to an elevation of 823 m--the base of the last 

steep incline to the mountaintop at 913 m. Substantial stand 

disturbance was evident above this point. At each plot 

location, all stems between the size of 1 m tall to 12.7 cm 

d.b.h. were recorded on a 23- by 1.5-m strip along the 

contour. At each end of the stri , a prism tally was made of E all larger stems using a 4.59 m /ha (20 $/acre) prism. The 

presence or absence of seedlings smaller than 1 m tall was 

recorded by species. 

Seventy-five stems of the following four species were aged: 

beech (Fagus grandifolia Ehrh.), sugar maple (Acer 
A. Advancing: constant B. Advancing: accelerating C. Advancing: decelerating 

AAAAAAAAAAAD 

2 0 m 

Y 

% 

w D. Retreating: constant 

G. Incipient 

E. Retreating: accelerating 

H. Catastrophic 

. . . . . . . . . . . I 

AAAAAA 

DISTANCE 

F. Retreating: decelerating 

AAAAAAA 

0 

0 

I. Stationary 

II Maximum A Minimum 

Figure 1 .--Schematic examples of types of fronts: Advancing (A-C), Retreating (D-F), 

Incipient (G), Catastrophic (H), and Stationary (I). 

saccharum Marsh.), red spruce (Picea rubens Sarg.), and 

eastern hemlock (Tsuga canadensis (L.) Carr.). These were 

the four most abundant shade-tolerant species in the cover 

types along the transect, which included lower elevation 

hemlock-spruce, mid-elevation northern hardwoods, and 

higher elevation sprucehardwood and spruce-fir. All stands 

were mature and either uncut or lightly cut in the past. At 

each plot location, the site or habitat (Leak 1982) was 

recorded. The predominant conditions were: (1) gravely 

outwash combined with loose rock supporting coniferous 

stands; (2) well-drained pan soils supporting coniferous 

stands; (3) fine till soils supporting northern hardwoods; (4) 

an association of fine till supporting northern hardwoods with 

shallow bedrock supporting coniferous stands; and (5) 

shallow bedrock with conifers. 

Elevations of the plot locations were established from 

detailed contour maps of the Experimental Forest. Numbers 

of understory stems (21 m tall and s 12.7 cm d.b.h.) and 

basal areas of overstory stems were summarized by plot 

location for the four major tolerant species. Statistics on 

balsam fir (Abies balsamea L.) were included for descriptive 

purposes, though this species was not sufficiently abundant 

for an analysis of age distribution. Maximum age of overstory 

and minimum age of understory (or smallest overstory stem) 

was determined by age1d.b.h. regressions developed for 

each species (Table 1). The regression for red spruce was 

ageAog d.b.h. The regressions for the other species were 

age/d.b.h.+(d.b.h.12. The regression fit was good in the small 

size classes; most of the variability was in the large sizes and 

old trees. 
Table !.--Sample numbers and regression statistics for 

age1d.b.h. and ageliog d.b.h. (red spruce) equations 

No. of Adjusted SD about 

Species samples R square regression 

Red spruce 19 .401 48 

Sugar maple 19 .953 13 

Beech 23 ,787 32 

Hemlock 14 .846 54 

Maine Survey Plots 

Records were available from more than 500 plots that were 

first measured in the 1950's and 1960's and finally 

remeasured in the early 1980's with one intermediate 

remeasurement, an average total period of 24 years. Each 

' plot consisted of a 0.08-ha (0.2-acre) circular plot where trees 

larger than 25 cm d.b.h. were recorded, and an enclosed 

0.04-ha plot for trees between 10 and 25 cm d.b.h. Plots 

were included in the analysis if they contained trees at any 

time during the measurement period and if the plot was not 

eliminated by land-use change. Latitude, longitude, and 

elevation were available for each plot. To assist in both the 

visual and quantitative analysis, the state was sectioned into 

locations, defined as 1 - by 1 - minute rectangles of land area. 

Initial numbers of locations per major species ranged from 

239 for balsam fir to 31 for red oak (Quercus rubra L.); plot 

numbers ranged from 483 to 36 (Table 2). The basic 

analytical approach was to compare the latitudes, longitudes, 

and elevations of plots and locations initially occupied by live 

trees of each major species with those newly occupied by the 

species (live trees or cut stumps) over the measurement 

period. Group t-tests were used to determine significant 

differences. 

Results 

Haystack Mountain 

Species Distribution 

Overstory basal areas of beech and sugar maple were 10 to 

20 m2/ha throughout most of the elevation range of the study 

up to 800 or 820 m (Fig. 2). Basal area of sugar maple is 

slightly lower than average on the dry pan and gravellloose 

rock sites below 600 m, but neither of these deciduous 

species is excluded by lower elevation site conditions. 

However, red spruce is abundant only on the dry pan and 

gravel sites below 600 m and on the bedrockltill and bedrock 

sites above 720 m. Hemlock is found only on dry pan and 

gravel at about 590 m and below. Understory stems (Fig. 3) 

follow a pattern similar to overstory basal areas. The 

noticeable exception is the lack of sugar maple understory 

above 720 m. 

Examination of Figures 2 and 3 indicate that there are 

several breaks in species' populations where we might look 

for moving fronts: beech and sugar maple at about 800 m 

elevation, hemlock and spruce at 600 m, spruce at 720 m, 

and the lack of sugar maple understory above 720 m--a 

condition that might suggest a retreating front. Both spruce 

and fir were evident in the disturbed stands on shallow 

bedrock above 823 m, but beech and sugar maple were not. 

Site apparently is an influential factor that currently limits the 

occurrence of a species, thus serving as a temporary barrier 

to species movement. However, it has been shown that the 

same soil will support different species in different climatic 

zones (Leak 1982). So, as the climate changes, we would 

anticipate that species will be able to cross previous site 

boundaries due to changes in their competitive position. 

Age Distribution 

The concept of vegetative stability is suggested by graphs of 

predicted maximum and minimum ages over horizontal 

distance for the four important tolerant species (Fig. 4). 

Typical stationary fronts, where maximum- and minimum-age 

trees occur and end at the same position, are evident for red 

spruce at about 500 and 975 m distances, and for beech at 

about 1,250 m distance. (In developing the graph for beech, 

several maximum-age trees just outside the prism plots were 

incorporated into the data.) Apparently, climatic change has 

not been sufficient to enable these species to cross site 

boundaries and invade other communities. The concept of 

"front" applies to the main population of a species, since we 

nearly find scattered, isolated trees of any species on most 

sites at most elevations. By contrast, hemlock exhibits a 

declining trend of maximum age over distance; note that this 

front does not yet cross the boundary into another site 

condition. Linear regression fits the points with an adjusted R 

Table 2.--Summary of initial numbers of Maine plots, 1- by 1-minute locations by major species, and appearance and 

disappearance of locations during a 24-year average period 

Item Red spruce Hemlock Balsam fir White pine Sugar maple Beech Red oak 

............................................................ Number ............................................................ 

Initial plotsa 442 159 483 154 1 74 1 63 36 

Initial locations 234 115 239 117 126 119 31 

Appearance 10 (4.31~ 14 (1 2.2) 23 (9.6) 20 (1 6.4) 21 (1 6.7) 21 (1 7.6) 14 (45.2) 

Disappearance 9 (3.8) 4 (3.5) 7 (2.9) 14 (12.1) 7 (5.6) 9 (7.6) 1 (3.2) 

aTotal number of plots within locations. 

b~ercent in parenthesis. 
20 Red Spruce 

Sugar Maple 

Beech 

0. 

0 .. 0 

0 0 .. 

o.0 0 

0 

.. 

0 .. ..a 

0 0 

0 

0 0 

201 Hemlock 

20i Balsam Fir 

GravellLoose Rock / x / Fine Till I Bedrocmll Bedrock 

ELEVATION (meters) 

Figure 2.--Live basal area of overstory trees larger than 10 cm d.b.h. by elevation and site 

for the major species on Haystack Mountain in New Hampshire. 

square of 0.62, significant at the 0.05 level, so the trend is 

indicative of a constant advancing front. However, the graph 

indicates that a concave-upward regression might provide a 

better fit if we had more points; this would reflect an 

accelerating advancing front. An incipient front is another 

possible interpretation. The inverse of the'linear regression 

coefficient provides an estimated migration rate of.0.6 m per 

year--very slow compared to the rates of over 100 m per year 

suggested by Davis and Zabinski (1 989) for species 

movement during the early postglacial period. Does the 

hemlock trend simply reflect a change in longevity over 

distance or elevation? Probably not. The site has not 

changed, and only moderate changes in elevation have 

occurred. 
Red Spruce 

A 

Sugar Maple 

A 

Beech 

Hemlock 

Balsam Fir 

A I 

GravelILoose Rock Fine Till Bedrockrlill Bedroek I 

ELEVATION (meters) 

Figure 3.--Number of stems more than 1 m tall and less than 10 cm d.b.h. by elevation 

and site for the major species on Haystack Mountain in New Hampshire. 

Possible changes in longevity might be illustrated in Figure 4 

by the slightly lowered curves for beech and sugar maple at 

about 900 to 950 m distance, near the change from till to 

bedrock/till. With a larger age sample, variables such as site 

and elevation should be incorporated into the age1d.b.h. 

regressions to better isolate changes in longevity. Does the 

hemlock front simply reflect cutting history? Probably not. 

Hemlock is the least valuable of all the species, and the 

downward trend occurs farthest from the road (an old logging 

railroad bed). We conclude that the hemlock front represents 

a very slowly moving, somewhat irregular migrational 

change. It is interesting to note that overstory basal area of 

hemlock and understory density both decline within the 

advancing front (Figs. 2-3), a characteristic of fronts noted 

previously (Solomon et al. 1990). 

Maximum and minimum ages of sugar maple beyond 1,000 

m distance (Fig. 4) illustrate a typical catastrophic front; a 
I 

I Red Spruce 

Sugar Maple 

Beech 

Hemlock 

Gravellloose Rock Dry Pan Fine Till BedrockT!ll 

I 

Bedrock 

DISTANCE (meters) 

Figure 4.--Predicted maximum and minimum ages (stems more than 1 m tall) over 

horizontal distance for the major species on Haystack Mountain. 

retreating front would have exhibited a declining trend beech even on the best site (fine till) (Fig. 3) while overstories 

between minimum age and distance. Regeneration are comparable (Fig. 2), implying that some reduction in 

establishment ceased about 100 years, ago on bedrockhill, sugar maple regenerative potential may be occurring 

though young seedlings still are observed. There is no throughout the study area. No explanation can be offered for 

indication of a similar collapse at other locations or sites at the presence of a sugar maple catastrophic front; climatic 

the same time or at a later date. However, it is interesting to warming does not seem a logical explanation. 

note that sugar maple understories are minimal compared to 
Maine 

The percentage of new locations occupied by each major 

species over the 24-year period ranged from 4 to 45 while the 

percentage of lost locations ranged from 3 to 12 (Table 2). 

These initial percentages indicated that movement of species 

was substantial. The next step was to determine whether 

there were directional or elevational trends. Tests in 

elevation, latitude, and longitude between the initially 

occupied and newly occupied plots showed that white pine 

(Pinus strobus L.) and balsam fir were moving slightly ker 

in both elevation and latitude (Table 3, Fig. 5). Average 

elevations of the two species declined by only 16 and 7 m, 

respectively, while average latitudes changed by 0.1 and 

0.04 degrees, about 11.3 and 4.5 km. The other significant 

change was an increase in the average longitude of sugar 

maple by 0.1 degree (6.9 km); the species also increased 

slightly though insignificantly in elevation. Hemlock, which 

showed a tendency toward movement on Haystack 

Mountain, remained stable in elevational and regional 

position; it is doubtful whether the small amount of movement 

indicated by the Haystack transect would be detected by the 

regional analysis in Maine. Red oak, which exhibited a high 

percentage of new locations, showed a slight but insignificant 

tendency toward a southerly and westerly movement. There 

is no indication of a pronounced upward or northerly trend in 

species ranges as might be expected if incipient global 

warming were occurring; in fact, the opposite seems to be the 

case. 

Discussion 

The elevation and regional analyses reported in this paper 

provide a fairly consistent picture of vegetative change. The 

transect on Haystack Mountain provided clear examples of 

stationary fronts for beech and red spruce coinciding with site 

changes that appeared to provide a temporary obstacle to 

species movement. Sugar maple exhibited a one-step 

catastrophic front at higher elevations where established 

understory trees less than about 100 years old were missing; 

this appears to be a specific site-related phenomenon that 

cannot be explained at present. Hemlock had a well-defined 

but slowly moving advancing front. The plot survey in Maine 

substantiated to some degree the results on Haystack 

Mountain by reinforcing the concept of stability in elevation 

and position of most species. The primary exception was the 

apparent southerly movement in the range of white pine and 

balsam fir as reflected by a decrease in average latitude of 

0.1 and 0.04 degrees. This movement is contrary to what 

might be expected under a scenario of global warming. We 

interpret this trend as a natural successional change on lands 

disturbed by cutting andlor agriculture. This points to one 

drawback in the use of regional survey plots to analyze 

species movements: it wilt be difficult to separate out slight or 

incipient change due to climatic trends or environmental 

impact from natural succession following earlier disturbance. 

Apparently, the latter factor is the dominant current 

underlying cause of species movement in Maine and 

probably most other New England States. Currently, there is 

no evidence from our study that if a climatic change is 

occurring, it has not materially affected the occurrence or 

competitive position of tree species in New England. Forest 

managers should be concerned primarily with species 

changes resulting from normal successional trends following 

previous disturbance from agriculture, clearing, and cutting. 

However, they should expect greater changes in the long 

term. 

Advancing-front theory rests on the assumption that treespecies age structure over distance (or elevation) will reflect 

migrational trends: advancing fronts should be evidenced by 

a decreasing trend in maximum age over distance; retreating 

fronts will be reflected by an increasing trend in minimum age 

over distance; and stationary fronts exhibit no trend. The 

reasonable success that we achieved with this approach 

resulted from several factors: 

Table 3.--Average elevation, latitude, and longitude of Maine plots occupied by major species at three measurement 

periods spanning a 24-year average period from the 1950's and 60's to the 1980's 

Measurement Red spruce Hemlock Balsam fit White pine Sugar maple Beech Red oak 

period 

Elevation (m) 

1 242(7)a 1 36(8) 238(7) 1 50(9) 265(10) 243(11) 121 (1 6) 

2 240 (8) 1 35(8) 241 (7) 1 42(9) 273(10) 250(11) 1 17(16) 

3 237(7) 1 36(7) 231 (7)" 1 34(8)" 272(10) 245(11) 1 19(14) 

Latitude (degrees) 

1 45.66(.04) 44.98(.06) . 45.69(.04) 44.82(.07) 45.64(.07) 45.41 (-06) 44.1 5(.10) 

2 45.68(.04) 44.96(.06) 45.71 (.04) 44.73(.07) 45.62(.07) 45.42(.07) 44.1 2(.09) 

3 45.64(.04) 44.95(.06) 45.65(.04)* 44.72(.06)* 45.58(.06) 45.40(.06) 44,l 0(.07) 

Longitude (degrees) 

1 69.05(.04) 69.1 8(.08) 69.08G04) 69.50608) 69.30(.07) 69.25(.07) 70.00(.14) 

2 69.01 (.04) 69.20(.08) 69.09(.04) 69.53(.08) 69.36(.07) 69.27(.07) 70.01 (.14) 

3 69.02(.04) 69.23(.07) 69.07(.04) 69.44(.07) 69.39(.06)- 69.26(.07) 70.05(.12) 

a~tandard error in parenthesis; **Significant at 0.01 level; *Significant at 0.05 level. 
4361 xxx x xx. - I :I :i;:xe 1 

lnfflal Locations 4.32 NewLocatlonr 

431 XX - 

7371707070707070 686SW869888689886868 676767676767 

I0643210 643210 643210 543210 

LONGITUDE (degnsm. rnlnutea) 

Figure 5.--Initial locations in Maine with living white pine, new locations after an average 

24-year period, and locations without white pine at either point in time. 

(1) The stands were fairly mature and only lightly disturbed. 

(2) Several distinct cover types were present, and the types 

were clearly demarcated due to elevational and site-related 

restrictions on species occurrence. 

(3) The study concentrated on tolerant species (beech, sugar 

maple, red spruce, and hemlock), which can regenerate in 

shade under an existing forest cover. 

(4) Sampling was intensive: plot locations every 30.5 to 15.2 

m in horizontal distance up the slope, with two prism samples 

of the overstory ( which intensively samples the larger trees) 

and a strip sample (1.5 by 23 m) of the understory at each 

plot location. 

A second important phase in migrational studies of this type 

would be to relate rates of movement to climatic variables or 

other environmental factors. For well-developed, rapidly 

moving fronts, we have suggested that rates of movement in 

different portions or segments of the front could be correlated 

to historical weather variables or to surrogates such as 

diameter growth. This would provide the basis for modeling 

species movements in response to any given or chosen set 

of climatic variables (Solomon et al. 1990). Similarly, climatic 

variables could be correlated to species movements on 

remeasured plots such as the Maine survey plots used in this 

study. These approaches would provide the basis for relating 

climate to actual changes in species elevations and locations 

rather than to hypothesized changes based on computer 

simulations. 

Ideally, ages would be determined on each plot. In this study, 

age1d.b.h. regressions were used to estimate approximate 

maximum and minimum ages per species. 
Literature Cited 

Brubaker, L. B. 1986. Response of tree populations to 

climatic change. Vegetatio. 69: 1 19-130. 

Davis, M.; Zabinski, C. 1989. Changes in geographical 

range from greenhouse warming effects on 

biodiversity in forests. In: Peters, R. L.; Lovejoy, T. E., 

eds. Proceedings, World Wildlife Fund conference: 

consequences of global warming for biological diversity. 

New Haven, CT: Yale University Press. 

Gajewski, K. 1987. Climatic impact on the vegetation of 

eastern North America during the past 2000 years. 

Vegetatio. 68: 179-1 90. 

Hamburg, S. P.; Cogbill, C. V. 1988. Historical decline of 

red spruce populations and climatic warming. Nature. 

331 : 428-431 . 

Leak, W. B. 1982. Habitat mapping and interpretation in 

New England. Res. Pap. NE-496. Broomall, PA: U.S. 

Department of Agriculture, Forest Service, Northeastern 

Forest Experiment Station. 28 p. 

Leak, W. B.; Graber, R.E. 1974. A method for detecting 

migration of forest vegetation. Ecology. 55: 1425-1 427. 

Overpeck, J. T.; Bartlein, P. J.; Webb Ill, T. 1991. Potential 

magnitude of future vegetation change in eastern 

North America: comparisons with the past. Science. 

254: 692-695. 

Pastor, J.; Post, W. M. 1988. Response of northern forests 

to Con-induced climate change. Nature. 334: 55-58. 

Peters, R. L. 1990. Effects of global warming on forests. 

Forest Ecology and Management. 35: 13-33. 

Solomon, A. M.; West, D. C. 1987. Simulating forest 

ecosystem responses to expected climate change in 

eastern North America: applications to decision 

making in the forest industry. In: Shands, W. E.; 

Hoffman, J. S., eds. The greenhouse effect, climate 

change and US. forests. Washington, DC: Conservation 

Foundation: 189-21 8. 

Solomon, D. S.; Leak, W. B.; Hosmer, R. A. 1990. Detecting 

and modeling the migration of tree species in 

response to environmental change. In: Research in 

forest inventory, monitoring, growth, and yield. IUFRO 

Proceedings from section 54.01 ; 1990 August 5-1 1, 

Montreal, PQ. Publ. FWS-3-90. Blacksburg, VA: Virginia 

Polytechnic Institute and State University: 230-239. 

8 Printed on Recycled Paper 

*U. 5. GOVERNMENT PRINTING OFFICE: 1994-5 50- 1 121800 18 

9 
Solomon, Dale S.; Leak, William B. 1994. Migration of tree species in New 

England based on elevational and regional analyses. Res. Pap. 

NE-688. Radnor, PA: U.S. Department of Agriculture, Forest Service, 

Northeastern Forest Experiment Station. 9 p. 

With field measurements of migration patterns, we used two complementary 

approaches to examine tree-species movement after a documented increase 

in temperatures. The advancing-front theory was used to examine age trends 

over distance and elevation for both a mountain site in New Hampshire and a 

regional comparison across the State of Maine. Well-defined stationary fronts 

were identified for red spruce (Picea rubens Sarg.) and beech (Fagus 

grandifolia Ehrh.), while a catastrophic front was depicted for sugar maple 

(Acer saccharum Marsh.) and a constant slow-moving advancing front was 

exhibited by hemlock Tsuga canadensis (L.) Carr.). The regional analysis, in 

Maine, indicated that white pine (Pinus strobus 1.) and balsam fir (Abies 

balsamea (L.) (Mill.) decreased significantly in average latitude and elevation 

over a 24-year period. The potential ranges of the major species in terms of 

elevation and regional position appear stable. 

Keywords: modeling; climate change 
Headquarters of the Northeastern Forest Experiment Station is in Radnor, Pennsylvania. Field Baboratories are maintained at: 

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Burlington, Vermont, in cooperation with the University of Vermont 

Delaware, Ohio 

Hampshire, in cooperation with the University of New Hampshire 

Hamden, Connecticut, in cooperation with Yale University 

Morgantown, West Virginia, in cooperation with West Virginia University 

Orono, Maine, in coo eration with the University of Maine 

Syracuse, eration with the State University of New York, 

College of Environmental Sciences and Forestry at Syracuse University 

University Perk, Pennsylvania, in cooperation with The Pennsylvania State University 

arren, Pennsylvania 

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