Stand Dynamics of Reference Plots 

in the West Virginia Long-Term Soil 

Productivity Studies

Mary Beth Adams, Brian Simpson, Charlene Kelly, 

Jamie L. Schuler, and John Juracko

United States Department of Agriculture

Forest Service Northern Research Station General Technical Report NRS-192 January 2020
Abstract

Tree death is a natural part of forest dynamics, yet is not often studied over long periods, 

particularly in temperate mixed-species hardwood stands. In this study, we evaluated stand 

dynamics of four reference plots on each of the West Virginia Long-term Soil Productivity (LTSP) 

Studies. The Fork Mountain LTSP Study was initiated in 1996 and the Middle Mountain LTSP Study 

in 1997. The two locations represent distinct stand types (mixed mesophytic and cherry-maple) 

and site conditions (elevation, parent material, aspect). We found that after 20 years, there were 

differences in patterns of mortality and ingrowth between the two sites. Mortality rates ranged 

from 1.5 to almost 5 percent for a 5-year period on Fork Mountain to 1 to 1.5 percent on Middle 

Mountain. Generally, ingrowth exceeded mortality on Fork Mountain, while the reverse was 

observed on Middle Mountain. Possible reasons for differences in mortality and ingrowth between 

the two sites include differences in species composition related to soil and site characteristics and 

differences in past disturbance that have created different stages of stand development.

The Authors

MARY BETH ADAMS is a research soil scientist and BRIAN SIMPSON is a forester with the Northern 

Research Station, 180 Canfield Street, Morgantown, WV 26505.

CHARLENE KELLY is a teaching assistant professor and JAMIE L. SCHULER is an associate professor 

with West Virginia University, Division of Forestry and Natural Resources, 1145 Evansdale Drive, 

Morgantown, WV 26505.

JOHN JURACKO is a forester in Marianna, PA.

Cover Photos

Fork Mountain Long-term Soil Productivity Study plot and sign over two decades, looking 

southeast toward McGowan Mountain. Clockwise from top left: winter 1997, summer 1998, winter 

Manuscript received for publication 12 September 2019

2009, and winter 2020. Photos by Mary Beth Adams, USDA Forest Service.

Published by

USDA FOREST SERVICE

ONE GIFFORD PINCHOT DRIVE

MADISON, WI 53726

January 2020
1

INTRODUCTION

Tree death is a natural part of forest dynamics. It is generally accepted that much of the 

historic mortality in forest stands results from self-thinning (Johnson et al. 2002). As trees 

grow larger, they require more resources and growing space to survive, with the result that 

some individuals are periodically crowded out and die. However, disturbances such as 

wildfire, drought, extreme weather, and insect and disease epidemics also result in pulses of 

tree mortality (Johnson et al. 2002). As extreme weather events, wildfires, and infestations are 

expected to increase across most of the globe due to climate change (Easterling et al. 2000), 

tree mortality may be expected to increase and become more widespread as well (Allen et 

al. 2010, Anderegg et al. 2013). For example, widespread tree mortality has recently been 

documented in ponderosa pine (Pinus ponderosa) forests in western United States (Fettig 

et al. 2019), correlated with drought and interactions with other stressors, such as insects. 

Background (non-event) mortality rates also have increased in recent decades (Peng et al. 

2011, van Mantgem et al. 2009). These changes and the likelihood for increased tree mortality 

are important because increases in mortality have the potential to change forest structure, 

species composition, and productivity, and because healthy forests with live trees are a carbon 

sink. In addition, live trees provide a variety of ecosystem services that can be impaired or lost 

with increased tree mortality (Allen et al. 2010).

Stand development of hardwood forests has been studied extensively, yet mortality of these 

important forest types over long periods of time is rarely quantified because it is highly 

variable and difficult to predict (Monserud 1976). Elliott and Swank (1994) reported mortality 

rates resulting from a severe multiyear drought ranging from about 12 percent (1.7 percent 

yr-1) for oak-pine communities within the Coweeta Basin, North Carolina, USA, to 20 

percent (2.8 percent yr-1) for cove hardwoods, and 23 percent (3.4 percent yr-1) for mixedoak communities. Others have reported typical background mortality rates for temperate 

forests from 1-2 percent per year (Brown and Schroeder 1999). Kabrick et al. (2004) reported 

mortality among oak-dominated forests in Missouri, USA, to be 13.9 percent per decade, or 

1.5 percent per year.

A major concern related to forest productivity and soil processes in the central Appalachians 

and globally is the issue of acidic deposition (particularly elevated deposition of nitrogen 

[N] and sulfur [S]), with resulting soil acidification, base cation depletion, N saturation 

and leaching, and implications for the productivity, diversity, and sustainability of central 

Appalachian hardwood forests (Adams 1999).

In these studies, we evaluate the stand dynamics, including the mortality rate, of two distinct 

hardwood forest types in the central Appalachians of West Virginia: mixed mesophytic 

and cherry-maple forests. These stands are part of experiments evaluating effects of acidic 

deposition on forests in the central Appalachians; this report uses only the information from 

the untreated reference plots. In particular, information will be used to document baseline 

“natural” mortality rates over a 20-year period and will also be used to inform growth and 

succession models being developed to forecast forest dynamics in a changing climate.

OBJECTIVES

1) Describe 20 years of stand dynamics (mortality, ingrowth, and species composition) 

on the reference plots of two Long-term Soil Productivity (LTSP) Studies located in 

West Virginia.

2) Compare and contrast mortality rates over time between the two forest types.
2

SITE DESCRIPTIONS AND METHODS

This study utilizes the uncut, untreated reference plots for the West Virginia Long-Term Soil 

Productivity Studies (Fig. 1), initiated in West Virginia (Adams et al. 2004) as an affiliate 

of the North American Long-Term Soil Productivity (LTSP) Study (Powers 2005). The first 

LTSP Study site in West Virginia, known as the Fork Mountain LTSP, is situated in a mesic 

mixed hardwood forest (Fig. 1). A second site is located on the Loop Road Research Area of 

the Monongahela National Forest in a cherry-maple stand (Fig. 1) (for scientific names of 

trees, see appendix 1). The research design, objectives, and hypotheses are the same for both 

LTSP West Virginia locations. The treatments include whole-tree harvesting and application 

of fertilizer and lime alone and in combinations; there are also unharvested, untreated 

reference plots. At both locations, there are four replicate blocks, designed to account for 

spatial variation and gradients across the site. For a detailed description of the study design, 

objectives, and pretreatment conditions, along with plot and treatment maps, see Adams et al. 

(2004) and Adams (2018). (See appendix 2 for aerial images of both sites obtained after the 

whole-tree harvests had been implemented. The reference plots are indicated on the photos). 

The reference plots are located randomly among the treatment plots with one reference plot 

per block. Both sites lie within the area classified as the Allegheny Mountain Section of the 

Central Appalachian Broadleaf Forest Province (McNab and Avers 1994). More detailed site 

descriptions are provided below.

Figure 1.—Location of the Fork Mountain and Middle Mountain Long–term Soil Productivity Studies in 

West Virginia.
3

Fork Mountain

These plots (reference plots 4, 8, 11, 16) are located on the Fernow Experimental Forest in 

Tucker County, West Virginia (latitude 39o 04 ́ N, longitude 79o 41 ́ W) on Fork Mountain 

and were established in 1996 (Adams et al. 2004). The site has a southeast aspect, with slopes 

ranging from 15 to 31 percent. Elevation ranges from 798 m to 847 m, and dominant parent 

materials include the sandstones and shales of the Hampshire Formation (Adams et al. 

2012). Soils are mapped as Calvin/DeKalb channery silt loam (loamy-skeletal, mixed, active, 

mesic Typic Dystrudepts). Annual average precipitation is 146 cm and is relatively evenly 

distributed between the growing and dormant seasons (Adams et al. 2012). Mean annual air 

temperature is 9.3 °C. At the initiation of this study, trees were approximately 85 years old and 

were typical of a relatively high-productivity central Appalachian mixed-hardwood forest (red 

oak site index = 24 m at age 50). With the exception of a small part of the most easterly plots 

(including reference plot 8), which was included in a strip clearcut in July 1977, this site was 

last harvested around 1910.

Middle Mountain

These plots (reference plots 17, 24, 28, 35) are located on the Loop Road Research Area on 

Middle Mountain, in Pocahontas County, West Virginia (38°38 ́15 ́N, 79°42 ́30 ̋ W) (Fig. 1) 

and were established in the summer and autumn of 1997. The Loop Road Research Area was 

initially set aside for research use in 1980. Elevations range from 1072 to 1129 m. Landforms 

include mostly convex ridgetops and side slopes. Aspect is generally southern, although 

most of the plots are located on or near the ridge tops, and slopes are generally less than 20 

percent. The dominant parent material is the hard sandstone of the Pocono formation (Adams 

2018). Soils are mapped as the Mandy series (loamy-skeletal, mixed, active, frigid, Spodic 

Dystrudepts). Average annual precipitation is 138 cm, distributed evenly throughout the year, 

with 241 cm average annual snowfall. Mean annual air temperature was 7.55 °C (U.S. Climate 

Data). At the initiation of the study, trees were approximately 75 years old. These stands 

originated following heavy timber cutting around 1920 (Miller 1997) and were typical of a 

black cherry-maple forest type (Society of American Foresters forest cover type 28; Eyre 1980). 

The overstory includes black cherry, American beech, red maple, sugar maple, and striped 

maple. Site index for black cherry in the study area is 23 m at base age 50 years, typical of a 

moderately productive site in the region.

Methods

Within the twenty 0.4047-ha measurement plots, all trees >2.54 cm in diameter were 

identified to species and tagged with metal tags in spring 1996 (Fork Mountain) and spring 

1997 (Middle Mountain). The diameter at breast height (d.b.h.; 1.37 m above ground) was 

measured to the nearest 0.25 cm. All trees within the plots were remeasured every 5 years 

during the dormant season, and their status (live, dead) was recorded. As new trees reached 

2.54 cm diameter, they were tagged and added to the tree list, representing ingrowth.1 There 

were 657 tagged trees on the Fork Mountain reference plots, and 1250 tagged trees on the 

Middle Mountain reference plots at the start of the studies. Over the intervening 20 years, 

almost 1200 additional trees were tagged as ingrowth and monitored.

1 Ingrowth is defined as trees that during a specified time period have grown to an arbitrary 

minimum diameter or height. 
4

Tree inventory data were used to calculate basal area and stand density. To evaluate changes in 

species composition, relative density (RD) and relative basal area (RBA) were used to calculate 

a relative importance value (RIV) for each tree species, where

RIV

RD RBA

2

(Jenkins and Parker 1997). Ingrowth was calculated as the number of new trees > 2.5 cm 

recorded in each 5-year period. Mortality was defined as the “newly dead” trees in each 

5-year period (trees that died during that 5-year period only). The percentage mortality was 

calculated as 

density of newly dead trees

total density

100

for each 5-year period. The total density of trees was the sum of the ingrowth for that 5-year 

period, the number of newly dead trees in that 5-year period, and the number of live trees. 

Data were summarized for the whole site and by plot, and by measurement date. Where 

appropriate, means and standard errors were calculated across the four plots at each site.

Fork Mountain LTSP reference plot 4, January 2020, 

showing large down trees from storms. Photos by Mary 

Beth Adams, USDA Forest Service.
5

RESULTS

Fork Mountain

At study initiation, these plots represented a diverse stand of mature trees (Table 1). Average 

basal area was 36.9 m2 ha-1 (std. error=1.6) and there were 811 stems ha-1 (std. error=85) . 

The pretreatment stand was dominated by sugar maple, red maple, northern red oak, and 

yellow-poplar. Black cherry and striped maple also were present in substantial proportions. 

The largest tree was a northern red oak measuring 102 cm d.b.h. Twenty-four species were 

recorded during the 20-year period but two species (white oak and pin cherry) were no longer 

present in the stand by the 2017 measurement period. Pin cherry was not a component of the 

pretreatment stand in 1996, but it was measured in 2007 and 2012, before disappearing again 

in the 2017 measurement. In addition, sourwood was not present in 1996, and first appeared 

in the 2002 census. American hornbeam was only recorded in 2012 and 2017.

Over 20 years, sugar maple importance decreased from 33.7 to 22.2 percent, and black cherry 

decreased from 7.6 to 3.4 percent (Fig. 2). Sweet birch increased from 1.4 to 18.9 percent, 

(increasing from 10 trees ha-1 to 233 tree ha-1) between the 2002 and 2007 censuses (Table 1), 

reflecting a large number of ingrowth trees (Table 2).

Both basal area and stem density increased over time (Table 1). The number of ingrowth 

trees peaked in 2007 and decreased only slightly in 2012, before returning to approximately 

pretreatment rates in 2017 (Table 2). Ingrowth on the Fork Mountain reference plots was 

dominated by sweet birch, striped maple, and yellow-poplar, with sugar maple showing the 

largest increase during the first 5 years of the study. Mean diameter for sweet birch and yellowpoplar decreased as the number of trees increased (Table 1).

The highest average mortality rates were observed between 1996 and 2002 and between 2012 

and 2017 (3.09 and 4.95 percent, respectively) (Table 3). Mortality rates of several species, 

particularly black locust and white oak, were notably high during these time periods, although 

these were represented by few, relatively large trees (Table 1). Most of the dead stems were in 

the 2.5 cm to 9.9 cm diameter class (Fig. 3).

Left: Middle Mountain, LTSP reference plot 35, October 

2018. Right: Middle Mountain LTSP reference plot 17, 

October 2018. Photos by Mary Beth Adams, USDA 

Forest Service. 
6

Fork Mountain 1996 2002 2007 2012 2017Species

Average 

BA

(m2/ha)

Average 

Trees/ha

Average 

d.b.h.

(cm) RIV

Average 

BA

(m2/ha)

Average 

Trees/ha

Average 

d.b.h.

(cm) RIV

Average 

BA

(m2/ha)

Average 

Trees/ha

Average 

d.b.h.

(cm) RIV

Average 

BA

(m2/ha)

Average 

Trees/ha

Average 

d.b.h.

(cm) RIV

Average 

BA

(m2/ha)

Average 

Trees/ha

Average 

d.b.h.

(cm) RIV

Bitternut hickory 0.4 6 25.9 0.9 0.4 6 26.8 0.9 0.4 6 27.6 0.8 0.5 6 28.3 0.8 0.5 5 34.0 0.7American hornbeam 0.001 1 3.6 0.0 0.002 1 4.3 0.0Eastern hophornbeam 0.1 16 6.3 1.1 0.1 19 6.9 1.2 0.1 17 7.9 0.8 0.1 11 10.7 0.5 0.1 9 11.4 0.4Sweet birch 0.4 14 17.9 1.4 0.4 10 21.6 1.2 0.5 233 3.8 9.6 0.8 472 4.2 15.5 1.3 494 4.9 18.9American beech 0.045 12 5.8 0.8 0.1 14 7.5 0.9 0.1 16 8.2 0.8 0.1 19 8.7 0.7 0.2 17 10.6 0.8White oak 0.1 1 34.5 0.2Chestnut oak 1.1 7 43.4 2.0 1.2 7 45.3 2.2 1.4 7 47.5 2.1 1.5 7 49.5 2.1 1.7 7 52.2 2.2Northern red oak 7.5 28 54.5 11.9 7.9 27 57.6 12.9 8.8 27 60.8 12.7 9.2 26 63.7 12.4 10.1 26 66.6 13.0Cucumbertree 0.6 10 25.4 1.4 0.7 10 27.7 1.5 0.8 12 24.2 1.5 0.8 15 20.3 1.4 0.9 16 20.6 1.6Fraser magnolia 1.3 35 17.9 3.9 1.2 41 14.1 4.0 1.2 59 10.9 3.8 1.3 59 12.1 3.4 1.4 62 12.6 3.8Yellow-poplar 6.5 43 41.0 11.5 7.2 41 44.9 12.5 7.3 90 22.4 13.0 8.0 172 14.3 15.3 8.0 154 16.0 15.1Downy serviceberry 0.044 4 11.4 0.3 0.1 4 12.7 0.3 0.1 4 13.5 0.2 0.026 2 11.6 0.1 0.028 2 12.1 0.1Pin cherry 0.005 2 4.8 0.1 0.006 2 5.3 0.1Black cherry 4.3 30 36.4 7.6 2.8 20 37.1 5.1 3.0 21 36.1 4.7 2.3 19 31.1 3.5 2.4 16 36.4 3.4Black locust 0.2 2 33.7 0.4 0.001 1 2.8 0.1 0.026 14 4.8 0.6 0.039 15 5.5 0.5 0.002 2 3.4 0.1Sugar maple 7.5 383 10.7 33.7 6.4 409 9.9 32.7 7.2 406 10.8 25.1 7.8 398 11.4 22.0 8.3 346 13.0 22.2Striped maple 0.1 85 3.9 5.4 0.2 128 4.1 7.7 0.3 238 3.9 9.6 0.3 244 4.0 7.9 0.2 120 4.2 4.4Red maple 4.5 99 20.9 12.1 4.6 90 22.3 11.8 5.1 105 20.7 10.8 5.0 115 18.6 9.8 4.8 101 20.0 9.3American basswood 0.7 15 20.5 1.8 0.8 17 19.6 2.1 0.8 15 22.7 1.6 0.8 14 24.9 1.5 0.9 12 27.9 1.5Blackgum 0.2 1 41.9 0.3 0.2 1 42.4 0.3 0.2 1 42.2 0.3 0.2 1 41.9 0.3 0.2 1 42.9 0.3Sourwood 0.001 2 2.5 0.1 0.003 4 3.1 0.1 0.004 2 4.3 0.1 0.008 2 6.6 0.1White ash 1.5 10 39.8 2.6 1.0 9 35.6 1.9 0.8 7 30.1 1.3 0.8 14 17.0 1.4 0.8 11 18.9 1.3Spicebush 0.003 4 3.0 0.2 0.003 2 3.9 0.1 0.005 2 4.8 0.1 0.006 2 5.5 0.1 0.006 2 5.5 0.1Witch hazel 0.007 6 3.8 0.4 0.009 9 3.5 0.5 0.015 14 3.7 0.5 0.022 20 3.7 0.6 0.015 11 4.1 0.4Total 36.9 811 35.2 867 37.9 1302 39.7 1636 41.7 1420Std. error 1.6 85 3.0 120 3.4 230 3.7 248 4.0 228Table 1.—Stand data for Fork Mountain LTSP Study reference plots pretreatment and at 5-year measurement intervals. Values are averages of four plots.
7

Figure 2.—Average tree species composition on the Fork Mountain LTSP Study reference plots, expressed as relative 

importance (percent), at five measurement dates.

Sweet Birch

1%

Yellow-Poplar

12%

Black Cherry

8%

Sugar Maple

34%

Striped Maple

5%

Red Maple

12%

Other Species

16%

Fork Mountain LTSP Relative Importance Value 1997

Northern Red Oak

12%

Northern Red Oak 

13%

Yellow-Poplar 

12%

Black Cherry 

5%

Sugar Maple 

33%

Striped Maple 

8%

Red Maple 

12%

Other Species 

16%

Fork Mountain LTSP Relative Importance Value 2002

Sweet Birch 

1%

Sweet Birch

9%

Northern Red Oak

13%

Yellow-Poplar

13%

Black Cherry

5%

Sugar Maple

25%

Striped Maple

9%

Red Maple

11%

Other Species

15%

Fork Mountain LTSP Relative Importance Value 2007

Sweet Birch

15%

Northern Red Oak

12%

Yellow-Poplar

15%

Black Cherry

4%

Sugar Maple

22%

Striped Maple

8%

Red Maple

10%

Other 

Species 14%

Fork Mountain LTSP Relative Importance Value 2012

Sweet Birch

19%

Northern Red Oak

13%

Yellow-Poplar

15%

Black Cherry

3%

Sugar Maple

22%

Striped Maple

5%

Red Maple

9%

Other Species

14%

Fork Mountain LTSP Relative Importance Value 2017
8

Table 2.—Ingrowth of trees during 5-year measurement period, by species, 

across Fork Mountain LTSP Study reference plots

Number of ingrowth trees across four plots

Species 2002 2007 2012 2017

American hornbeam 0 0 1 0

Eastern hophornbeam 2 0 0 0

Sweet birch 0 185 210 69

American beech 1 2 2 0

Cucumber magnolia 0 2 3 2

Fraser magnolia 12 18 4 3

Yellow-poplar 0 41 67 11

Pin cherry 0 2 0 0

Black cherry 0 1 3 0

Black locust 1 10 2 1

Sugar maple 61 19 13 4

Striped maple 58 122 62 17

Red maple 1 12 16 1

American basswood 2 0 0 0

Sourwood 2 1 0 0

White ash 0 1 7 0

Witch hazel 3 4 8 1

Total number of ingrowth trees 143 420 398 109

Average number of ingrowth trees 

per hectare 88.4 259.4 245.9 67.3

Table 3.—Average percentage mortality by species and measurement period, for 

four Fork Mountain LTSP Study reference plots, based on number of trees per hectare

Percent mortality

Species 2002 2007 2012 2017

Bitternut hickory 5.00

Eastern hophornbeam 1.67 8.93 5.56

Sweet birch 6.82 0.52 1.07 2.83

American beech 1.67

White oak 25.00

Northern red oak 1.09 1.14

Cucumber magnolia 1.92 1.79

Fraser magnolia 4.38 1.47 1.92 0.49

Yellow-poplar 1.43 0.34 0.18 4.17

Downy serviceberry 8.33

Pin cherry 25.00

Black cherry 8.33 6.25 3.33

Black locust 16.67 1.92 21.15

Sugar maple 2.76 1.50 1.46 3.53

Striped maple 4.53 3.65 5.59 13.72

Red maple 2.47 1.98 3.19

American basswood 3.57 2.08 2.27

Sourwood 8.33

White ash 3.13 6.25 3.85 4.55

Spicebush 8.33

Witch hazel 3.13 3.95 11.76

Average percent mortality across all species 3.09 1.49 2.20 4.95

Std. error 3.83 0.93 1.63 3.29
9

Middle Mountain

At the beginning of the study, the Middle Mountain stand had high stem density (1543 stems 

ha-1, std. error=270.2), with almost twice the number of trees as Fork Mountain. The Middle 

Mountain stand also had lower species richness, with 12 tree species, and just four species 

made up 90 percent of the species richness (Table 4). The reference plots were dominated by 

red maple (approx. 40 percent RIV), black cherry (29 percent), American beech (19 percent), 

and about 7 percent red spruce. Basal area was 43.1 m2 ha-1 (std. error=2.3) and the trees were 

generally smaller in diameter than at Fork Mountain. The largest tree on Middle Mountain 

was a black cherry measuring 53.6 cm d.b.h. The relative proportions of species did not change 

over time (Fig. 4), nor were any species added or lost from the stand during the 20 years. 

One plot (plot 35) had almost twice the number of live trees per hectare than the other three 

reference plots (Fig. 5); otherwise the four plots were similar.

Although Middle Mountain stem density was originally higher than Fork Mountain (1543 

trees ha-1compared to 811 trees ha-1on Fork Mountain), density declined slightly over 

time, and after 20 years was approximately the same as Fork Mountain (~1400 trees ha-1). 

Black cherry, sweet birch, and red maple density decreased over time and average diameter 

increased, while American beech density increased over time with a slight increase in average 

diameter. Basal area increased over the 20 years (Table 4). Ingrowth was limited to a few 

species and was dominated by American beech (Table 5), occurring mostly by sprout origin 

(M.B. Adams, unpublished data). The number of ingrowth stems was considerably fewer than 

on Fork Mountain. There were no large changes in mortality either among plots or overall 

on Middle Mountain, and mortality was generally slightly above 1 percent over each 5-year 

period (Table 6). The number of dead trees was more evenly distributed across the size classes 

on Middle Mountain reference plots than on Fork Mountain reference plots, but the total 

number of dead trees was low (data not shown).

Figure 3.—Total number of newly dead trees, across four reference plots, by measurement date and diameter 

class, Fork Mountain LTSP reference plots.

0

50

100

150

200

250

300

2.5 - 9.9 10.0 - 14.9 25.0 - 37.9 >38

Mortality (no. of Trees)

15.0 - 24.9

Diameter Class (cm)

2002 2007 2012 2017
10

Middle Mountain 1997 2003 2007 2013 2018Species

Average

BA

(m2/ha)

Average

Trees/ha

Average

d.b.h.

(cm) RIV

Average

BA

(m2/ha)

Average

Trees/ha

Average

d.b.h.

(cm) RIV

Average

BA

(m2/ha)

Average

Trees/ha

Average

d.b.h.

(cm) RIV

Average

BA

(m2/ha)

Average

Trees/ha

Average

d.b.h.

(cm) RIV

Average

BA

(m2/ha)

Average

Trees/ha

Average

d.b.h.

(cm) RIV

Red spruce 0.8 178 7.0 6.7 1.0 179 7.9 7.1 1.2 181 8.8 7.5 1.5 188 9.5 8.1 1.7 183 10.3 8.3Sweet birch 1.2 33 19.5 2.4 0.9 22 20.7 1.7 0.6 15 21.0 1.1 0.5 11 22.8 0.9 0.5 10 23.1 0.9Yellow birch 0.1 2 24.6 0.2 0.1 2 25.5 0.2 0.2 2 26.3 0.2 0.1 1 37.1 0.2 0.1 1 37.6 0.2American beech 2.0 516 6.2 19.0 2.2 516 6.5 19.7 2.5 530 6.8 20.9 2.8 551 7.0 22.1 3.0 562 7.2 23.4Cucumbertree 0.3 4 27.5 0.5 0.3 4 29.0 0.5 0.4 4 30.1 0.5 0.4 2 42.3 0.4 0.4 2 44.3 0.5Downy serviceberry 0.3 23 11.2 1.1 0.3 23 11.1 1.1 0.2 20 11.4 0.9 0.2 19 11.2 0.9 0.2 17 11.7 0.9Black cherry 19.2 209 33.5 29.0 20.2 201 35.1 28.5 20.3 186 36.6 27.6 20.1 174 37.7 26.5 19.4 154 39.1 25.0Sugar maple 0.3 16 13.3 0.9 0.3 14 13.9 0.8 0.3 11 15.4 0.7 0.3 11 15.5 0.7 0.3 11 15.9 0.7Striped maple 0.006 6 3.5 0.2 0.009 6 4.2 0.2 0.010 6 4.4 0.2 0.010 5 5.1 0.2 0.011 5 5.4 0.2Red maple 18.9 544 19.2 39.6 21.0 511 20.9 39.8 22.2 480 22.2 39.8 23.4 456 23.4 39.7 24.2 422 24.8 39.5Spicebush 0.008 10 3.2 0.3 0.009 11 3.2 0.4 0.011 12 3.3 0.4 0.011 11 3.4 0.4 0.012 11 3.6 0.4Witch hazel 0.001 1 3.6 0.0 0.001 1 3.8 0.0 0.002 1 4.1 0.0 0.002 1 4.1 0.0 0.002 1 4.6 0.0Total 43.1 1543 46.4 1491 47.9 1449 49.3 1430 50.0 1380Std. error 2.3 270.2 7.6 275.4 2.4 266.1 2.3 273.0 2.4 257

Table 4.—Stand data for Middle Mountain LTSP Study reference plots, pre-treatment and at 5- year measurement intervals. Values are averaged across four plots.
11

Figure 4.—Average tree species composition on the Middle Mountain LTSP Study reference plots, expressed as 

relative importance value (percent), at five measurement dates.

Red Spruce

7%

American Beech

19%

Black cherry

29%

Red Maple

39%

Other Species

6%

Middle Mountain LTSP Relative ImportanceValue 1997

Red Spruce

7%

American Beech

20%

Black cherry

28%

Red Maple

40%

Other Species

5%

Middle Mountain LTSP Relative Importance Value 2003

Red Spruce

7%

American Beech

21%

Black cherry

28%

Red Maple

40%

Other Species

4%

Middle Mountain LTSP Relative Importance Value 2007

Red Spruce

8%

American Beech

22%

Black cherry

26%

Red Maple

40%

Other Species

4%

Middle Mountain LTSP Relative Importance Value 2013

Red Spruce

8%

American Beech

23%

Black cherry

25%

Red Maple

40%

Other Species

4%

Middle Mountain LTSP Relative Importance Value 2018
12

Table 5.—Ingrowth of trees during 5-year measurement period, by species, across 

four Middle Mountain LTSP reference plots

Number of trees across four plots

Species 2003 2007 2013 2018

Red spruce 3 2 5 1

American beech 16 26 31 29

Downy serviceberry 1 0 0 0

Red maple 1 1 1 1

Spicebush 1 3 1

Total 22 32 37 32

Average number of ingrowth trees per hectare 13.6 19.8 22.9 19.8

0

500

1000

1500

2000

2500

1997 2003 2007 2013 2018

Trees per Hectare

Year

Plot 17 Plot 24 Plot 28 Plot 35

Figure 5.—Total number of live trees per hectare on the Middle Mountain LTSP Study reference plots, 

at five measurement dates.

Table 6.—Average percent mortality by species and measurement period, for four 

Middle Mountain LTSP Study reference plots

Species 2003 2007 2013 2018

Red spruce 0.34 0.82

Sweet birch 8.33 8.33 6.25 2.78

Yellow birch 12.50

American beech 0.92 0.84 0.71 1.05

Cucumber magnolia 8.33

Downy serviceberry 1.25 3.95 1.56 1.67

Black cherry 0.89 1.84 1.66 2.84

Sugar maple 3.85 4.55

Striped maple 5.00

Red maple 1.58 1.57 1.35 1.83

Spicebush 4.17 2.50 2.50

Average percent mortality across all species 1.26 1.33 1.07 1.49

Std. error 1.18 0.64 0.32 0.61
13

DISCUSSION

These reference plots align well with the pretreatment measurements of the entire study areas, 

as described in Adams et al. (2004) and Adams (2018), which suggests they are representative 

of the entire study areas. The differences observed between the two sites are also the same as 

described at study initiation (Adams et al. 2004, Adams 2018). These stands are similar in age, 

but differ in structure, diversity, and productivity. Generally, Middle Mountain had greater 

stem density and basal area, but smaller diameter trees, than the Fork Mountain site. The Fork 

Mountain site also had a greater number of tree species.

The stand dynamics also differed between the two sites during the 20 years. Mortality was 

generally greater at the Fork Mountain site (Table 3) than at Middle Mountain (Table 6) and 

was more variable among the measurement periods. Likewise, ingrowth was less on Middle 

Mountain (15 to 20 trees ha-1), and more consistent over the 20 years. Also, the number of 

ingrowth stems at Middle Mountain represented 35 to 70 percent of the newly dead trees 

during a 5-year period, indicating a decline in stem density with time. By contrast, ingrowth 

on Fork Mountain exceeded the number of newly dead trees, except in 2017, and was 10 times 

greater or more than Middle Mountain (Fig. 6).

0

50

100

150

200

250

300

2002 2007 2012 2017

Number of stems/ha

FM-Ingrowth FM-Newly dead

Year

A

0

5

10

15

20

25

30

35

40

45

50

2002 2007 2012 2017

Number of stems/ha

Year

MM-Ingrowth MM-Newly dead

B

Figure 6.—Number of ingrowth trees 

and newly dead trees per hectare over 

each 5-year measurement period for 

Fork Mountain (A) and Middle Mountain 

(B) LTSP Study reference plots. Note 

the difference in scales for the y axes. 

Measurements started in 1996 at Fork 

Mountain and 1997 at Middle Mountain.
14

There are several possible reasons for the differences in mortality and ingrowth between 

the two sites, including differences in: 1) species composition, reflective of different site 

conditions; and 2) disturbance history, including experimental layout.

The species composition between the two sites is influenced particularly by climatic and soil 

parameters. While the soils are similar—relatively young soils with high coarse fragment 

content, low base saturation, and relatively low available water holding capacity—the soil 

processes have clearly been affected by climate. The presence of spodic characteristics at 

the higher elevation Middle Mountain site reflect the cooler annual temperature, as well as 

perhaps the influence of conifer vegetation historically. The less diverse stands at Middle 

Mountain reflect a cooler climate, and likely shallower, more acidic soils resulting from the 

influence of the more resistant hard sandstone parent material. In contrast, the Fork Mountain 

site is warmer, receives slightly more precipitation, and has deeper, less acidic soil, likely 

allowing for greater forest stand diversity. While there are species common to both sites, 

differences in species undoubtedly affected mortality rates, as has been reported elsewhere 

(Fien et al. 2019).

While these plots are uncut, untreated reference stands, some of the differences we see in 

stand processes could reflect the disturbance history of the experimental areas. For example, 

the position of the reference plots relative to the treated plots on the landscape. On Fork 

Mountain, the reference plots had whole-tree harvested plots on at least two sides (appendix 2, 

Fig. 9), and two of the reference plots (plots 8 and 11) had cut plots on three and four sides, 

respectively. Although there was a buffer (7.6 m wide) along each edge, given the taller trees 

on Fork Mountain (29.3 m on average, compared with 22.6 m for Middle Mountain) (Adams 

et. al. 2004, Adams 2018), it may be that the removal of surrounding trees from the treated 

plots increased the amount of light reaching the forest floor within the reference plots. The 

greater light incidence may have caused a pulse of ingrowth in the early measuring periods. 

Ingrowth was higher on plots 8 and 11, the more exposed plots, than on plots 4 and 8, 

providing some support for that hypothesis (Fig. 7). Reference plots on Middle Mountain, 

however, had “open” edges on, at most, two sides (appendix 2, Fig. 10), and the trees were 

generally shorter and smaller in diameter on Middle Mountain. Thus, the influence of 

harvesting adjacent plots on resulting light incidence was likely less substantial. This could 

explain the larger ingrowth at Fork Mountain.

However, the patterns of newly dead trees were not the same for the two sites (Fig. 6). On Fork 

Mountain, the number of newly dead trees per hectare decreased during the first 10 years, 

then increased during the second decade, with the greatest number of newly dead trees in the 

measurement period ending in 2017. This is also reflected in the mortality rate, which reached 

almost 5 percent on Fork Mountain in 2017. The mortality rate on the Middle Mountain site 

showed no trends and consistently remained between 1 and 1.5 percent.

We hypothesize that the patterns of mortality, and to a lesser extent ingrowth, observed on 

Fork Mountain may be mostly attributed to storm damage. There was a large pulse of newly 

dead trees in 2002, which corresponded with a decrease in live basal area between 1997 and 

2002 (Fig. 8). On January 2, 1999, a severe wind event directly impacted the Fork Mountain 

LTSP. Estimates at the time suggested that 50 percent of the basal area had blown down on 

plot 4 (M.B. Adams, personal communication). Later assessment documented that 34 trees 

had been blown over or severely damaged on plot 4, with an additional eight trees on plot 

8. Notably, the live basal area declined for plot 4 during the 5-year period from 1997–2002 

(from 40 m2 ha-1 to approximately 28 m2 ha-1) (Fig. 8) and the newly dead basal area also was 

greater on plot 4 in 2002 (15 m2 ha-1). The other reference plots were relatively less damaged 

by this storm. The large increase in ingrowth after 10 years (measurement date 2007) (Figure 
15

0

50

100

150

200

250

300

350

400

450

500

Plot 4 Plot 8 Plot 11 Plot 16

Ingrowth (no. of trees)

2002 2007 2012 2017

Figure 7.—Ingrowth of trees by plot and measurement date for Fork Mountain LTSP Study.

0.00

10.00

20.00

30.00

40.00

50.00

60.00

Live1997 Live 2002 Live 2007 Live 2012 Live 2017 Dead Dead Dead Dead 

2002 2007 2012 2017

Basal area (m2/ha)

Plot 4 Plot 8 Plot 11 Plot 16

Figure 8.—Basal area per hectare for live and dead trees for four reference plots on the Fork Mountain LTSP Study.
16

6) may reflect the flush of growth following the canopy-opening event of 1999, perhaps in 

combination with the differential impacts of implementing the experimental treatments. 

Other wind events in 2009 and Superstorm Sandy in 2012 (Walter 2016) also likely impacted 

the Fork Mountain LTSP. While these events do not appear to affect the total live basal area 

(Fig. 8), they may have contributed to the slight increase in dead basal area in 2012 (plots 8 

and 11) (Fig. 8). Also, as the large number of ingrowth stems became competitive on the Fork 

Mountain plots over time, density-dependent mortality likely increased among these trees. 

Despite its higher elevation and greater snowfall, the plots on Middle Mountain were not 

exposed to these severe events.

We suggest that the two stands are at different stages of stand development due to both site 

differences and the disturbances described above. Fork Mountain was likely “reset” to the 

stand initiation stage while Middle Mountain has progressed to the stem exclusion stage. The 

differences in stage of stand development, along with the patterns of light availability and 

differences in species composition and shade tolerance, help elucidate the differences between 

mortality and ingrowth patterns documented between the two sites.

Finally, the mortality rates reflect severe disturbance on Fork Mountain (1.5 percent to almost 

5 percent over a 5-year period), which are comparable to those reported by Elliott and Swank 

(1994) in response to a severe multiyear drought. Mortality rates at the Middle Mountain site 

are lower, and represent the lower end of the spectrum for background mortality rates relative 

to other published values in the literature (Brown and Shroeder 1999, Kabrick et al 2004).

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D.M. 2005. The North American long-term soil productivity experiment: findings from 

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ACKNOWLEDGMENTS

These two research studies required an extraordinary effort to establish and maintain, and 

the work of many technicians, particularly Chris Cassidy and Doug Owens, and the Fernow 

logging crew are gratefully acknowledged. Debbie Page-Dumroese and John Kabrick provided 

helpful reviews early in the process. This project has received funding support from the 

National Science Foundation Long Term Research in Environmental Biology program (DEB0417678 and DEB-1019522).
19

APPENDIX 1

Table 7.—Common and scientific names of trees found on Fork Mountain 

and Middle Mountain LTSP Studies reference plots

Common Name Scientific Name

Red spruce Picea rubens

Sweet birch Betula lenta

Yellow birch Betula alleghaniensis

American beech Fagus grandifolia

Cucumber magnolia Magnolia acuminata

Downy serviceberry Amelanchier arborea

Black cherry Prunus serotina

Sugar maple Acer saccharum

Striped maple Acer pensylvanicum

Red maple Acer rubrum

Spicebush Lindera benzoin

Witch hazel Hamamelis virginiana

Bitternut hickory Carya cordiformis

American hornbeam Carpinus caroliniana

Eastern hophornbeam Ostrya virginiana

White oak Quercus alba

Chestnut oak Quercus montana

Northern red oak Quercus rubra

Frasier magnolia Magnolia fraseri

Yellow-poplar Liriodendron tulipifera

Downy serviceberry Amelanchier arborea

Pin cherry Prunus pensylvanica

Black locust Robinia pseudoacacia

American basswood Tilia americana

Blackgum Nyssa sylvatica

Sourwood Oxydendrum arboreum

White ash Fraxinus americana
20

APPENDIX 2

Figure 9.—Aerial photo of Fork 

Mountain LTSP Study plots, showing 

the location of reference (REF) plots; 

all other plots were whole-tree 

harvested. For details of study, see 

Adams et al. 2004.

Figure 10.—Aerial photo of the Middle 

Mountain LTSP Study plots, with 

the reference plots shown by black 

box outlines, adjacent to plots that 

had been whole-tree harvested. See 

Adams 2018 for details of treatment 

assignments.
Adams, Mary Beth; Simpson, Brian; Kelly, Charlene; Schuler, Jamie L.; Juracko, John. 2020. 

Stand dynamics of reference plots in the West Virginia long-term soil productivity 

studies. Gen. Tech. Rep. NRS-192. Madison, WI: U.S. Department of Agriculture, Forest 

Service, Northern Research Station. 20 p. https://doi.org/10.2737/NRS-GTR-192.

Tree death is a natural part of forest dynamics, yet is not often studied over long periods, 

particularly in temperate mixed-species hardwood stands. In this study, we evaluated stand 

dynamics of four reference plots on each of the West Virginia Long-term Soil Productivity 

(LTSP) Studies. The Fork Mountain LTSP Study was initiated in 1996 and the Middle Mountain 

LTSP Study in 1997. The two locations represent distinct stand types (mixed mesophytic 

and cherry-maple) and site conditions (elevation, parent material, aspect). We found that 

after 20 years, there were differences in patterns of mortality and ingrowth between the 

two sites. Mortality rates ranged from 1.5 to almost 5 percent for a 5-year period on Fork 

Mountain to 1 to 1.5 percent on Middle Mountain. Generally, ingrowth exceeded mortality 

on Fork Mountain, while the reverse was observed on Middle Mountain. Possible reasons for 

differences in mortality and ingrowth between the two sites include differences in species 

composition related to soil and site characteristics and differences in past disturbance that 

have created different stages of stand development.

KEY WORDS: tree mortality, forest stand dynamics, mixed hardwood forests, LTSP

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