United States

Department of

Agriculture

Forest

Service

Northern

Research Station

Research Paper 

NRS-17

Ten-year Results from the 

Long-term Soil Productivity Study 

in Aspen Ecosystems of the 

Northern Great Lakes Region 

Richard Voldseth

Brian Palik

John Elioff
Abstract

Impacts of organic matter removal and compaction on soil physical and 

chemical properties and forest productivity are reported from the fi rst 10 years 

of the Long-Term Soil Productivity Study in Great Lakes aspen ecosystems. 

Organic matter removal treatments included main bole, total tree harvest, and 

total tree harvest with forest fl oor removal. Compaction treatments included 

no compaction beyond normal levels from harvest, moderate compaction, and 

heavy compaction. Main bole harvest with no additional compaction served as 

the control against which other treatments were compared. Study treatments 

were replicated in three locations on a clay loam, silt loam, and loamy sand 

soil. All compaction treatments on all three soil types increased bulk density 

above preharvest levels. In most cases, bulk density at year 10 had decreased 

signifi cantly compared to year 0, but was still generally above preharvest levels. 

Total carbon and nitrogen showed no impact from treatment at year 10. In 

general, soil cations were little affected by organic matter removal. The major 

exceptions were lower near-surface calcium in the loamy sand soil with total 

tree harvest plus forest fl oor removal, and lower potassium at 10-20 cm depth 

in the loam soil for both total tree harvest with and without forest fl oor removal. 

Compaction and organic matter removal treatments impacted aboveground 

forest productivity, however the effects were not universal across the soil types. 

Aboveground biomass production declined on the loam soil with moderate and 

heavy compaction. Production increased with moderate compaction on the loamy 

sand and clay loam soils, but signifi cantly decreased with heavy compaction on 

the clay loam soil. Total tree harvest with forest fl oor removal reduced production 

on the loamy sand and loam soils, while it increased production on the clay loam 

soil. Results from this study suggest that heavy compaction and/or high organic 

matter removals (e.g., total tree harvest plus forest fl oor removal) are generally 

detrimental to sustaining forest productivity across soil types. Total tree harvest 

with limited compaction may be sustainable, at least as refl ected in 10 year 

results, after one harvest entry. Managers should be cautious of approaches 

involving whole-tree harvests, or even bole-only harvests, on short rotations 

(~10 years), as such approaches will limit the potential for recovery to preharvest 

bulk densities and may have the potential to increase compaction to levels seen 

with heavy compaction.

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Manuscript received for publication January 2011
INTRODUCTION

In the face of increased interest in utilization of wood fi ber for biofuels, 

sustaining long-term site productivity is a fundamental issue confronting 

forest management (Hendrickson et al. 1989, Powers et al. 1990a, 

Walmsley et al. 2009). Site productivity, that we here defi ne as sustained 

capacity to capture carbon and produce plant biomass, is affected by 

environmental drivers, such as climate. Within the limits of climate, 

the potential net primary productivity of a site is regulated by biotic, 

chemical, and physical soil properties and processes, which, in turn, can 

be altered by human-caused disturbances (Powers et al. 2004). How soil 

disturbances affect productivity of forests is still not well understood 

(Powers et al. 2005). 

Soil properties directly affected by disturbance include porosity and 

organic matter content (Powers et al. 1990b). Porosity and organic 

matter regulate fundamental ecosystem processes through their infl uence 

on water and gas exchange, physical restrictions on rooting, microbial 

activity, soil aggregate stability, and resource availability. Forest 

harvesting can reduce porosity through compaction by machinery 

traffi c. Soil porosity refl ects a continuum of void sizes that vary with the 

mineral nature and degree of weathering of the parent material (Powers 

1999). The mechanism by which soil compaction impacts productivity 

is through the breakdown of surface aggregates causing decreased 

macropore volume and increased soil bulk density (Powers 1999, 

Pritchett and Fisher 1987). This can impede both root growth and water 

infi ltration, and can alter the balance of oxygen and carbon dioxide in 

the soil profi le and gas exchange with the atmosphere which, in turn, can 

alter soil pH and nutrient regimes (Ballard 2000, Powers 1999).

Soil organic matter content is directly related to the amount of organic 

matter entering the soil from plant tissue. Forest fl oor organic matter 

constitutes an energy source for soil fauna and microbes and is a 

reservoir of nutrients supplied to the soil through pulses in litterfall 

and root sloughage. Direct removal of plant and plant-derived organic 

matter, including the forest fl oor, as well as reduced capacity to produce 

new organic matter, can lead to reductions in soil organic matter 

concentrations. Moreover, the loss of forest fl oor can result in increased 

soil temperatures and a reduction of decomposition products that aid in 

the development of soil structural aggregates (Powers 1999). Soil organic 

matter loss can also lead to decreases in soil water-holding capacity and 

can alter soil ion exchange and nutrient capital (Powers 1999, Zabowski 

et al. 1994).

The Authors

RICHARD VOLDSETH is a 

research associate with the 

Department of Soil Science, 

North Dakota State University, 

Fargo, ND.

BRIAN PALIK is a research 

ecologist with the Center for 

Research on Ecosystem Change, 

Northern Research Station, 

Grand Rapids, MN.

JOHN ELIOFF is a forestry 

technician (retired) with 

the Center for Research 

on Ecosystem Change, 

Northern Research Station, 

Grand Rapids, MN.

1
2

The North American Long-Term Soil Productivity 

(LTSP) Study was conceived to address the 

consequences of pulse soil disturbance on forest 

productivity, as impacted by reductions in soil 

porosity, through compaction, and soil organic matter 

content, through organic matter removal. The U.S. 

Department of Agriculture - Forest Service is legally 

bound by the National Forest Management Act of 

1976 to manage land in such a way that its long-term 

productivity is not impaired (Powers et al. 1990a, 

Powers et al. 1990b, Powers 1999, Powers et al. 

2005, Powers 2006, Tiarks et al. 1997). In response, 

the Forest Service has charged each region with the 

National Forest System (NFS) with developing soil 

quality monitoring standards that can detect losses in 

productive potential of the land over a rotation (PageDumroese et al. 2000, Powers et al. 1990a, Powers et 

al. 1990b). In 1989, as a result of these concerns and 

mandates, Forest Service research scientists and NFS 

managers set the foundation for the LTSP program 

(Powers 2006, Tiarks et al. 1997). Today, the LTSP 

program is an international endeavor with identical 

experimental designs and study questions being 

addressed at multiple sites. 

The LTSP experiment specifi cally targeted soil 

porosity and organic matter for manipulation in 

large-scale, long-term experiments. The LTSP 

experiment was designed to address the following 

primary question: do pulse reductions in site organic 

matter and/or soil porosity reduce the sustained 

productive potential of a site? Treatments include 

three levels of soil compaction factored with three 

levels of aboveground organic matter removal. The 

ranges of treatments were chosen to encompass the 

range of possibilities occurring under contemporary 

management. 

The Lake States installations of the LTSP Study 

are located in forests dominated by trembling and 

bigtooth aspen (Populus tremuloides Michx., Populus 

grandidentata Michx.). These forests are the dominant 

early successional forest type in the region (Schulte et 

al. 2007) and as such are of tremendous economic and 

ecological importance. Trembling aspen dominated 

forests are early successional across a range of site and 

soil conditions and develop with relatively uniform 

tree sizes with culmination of mean annual increment 

occurring around 30 to 40 years of age. They lend 

themselves to intense mechanized harvesting regimes 

and whole (total) tree utilization (Alban 1991) for 

wood products and, more recently, feedstocks for 

wood-based biofuels. The long-term productivity 

impacts of intensive harvesting and biomass removal 

for energy feedstocks are not well understood (Grigal 

2000). 

Monitoring of the LTSP Study is to be conducted over 

one full rotation or about 50 years. This report presents 

fi ndings from the fi rst 10 years of monitoring in the 

Lake States LTSP installations. Several tenth-year 

syntheses from the national effort have been published 

previously (Powers et al. 2004, 2005). Mirroring 

the national program, our primary objective for this 

project is to understand how organic matter removal 

and changes in soil porosity due to compaction affect 

a site’s productive carrying capacity and, ultimately, 

sustainability of biomass production in aspen 

ecosystems. We asked the following questions: Is there 

an effect of organic matter removal or soil compaction 

on soil physical and chemical variables that may 

account for productivity responses? Is there an effect 

of organic matter removal or compaction treatments on 

vegetation productivity and abundance after 10 years? 

At what level of organic matter removal or compaction 

are effects evident? 

METHODS

Study Areas

This study is based in three geographically separate 

locations, with each site representing a distinctly 

different soil texture. All sites were established in 

fully stocked evenaged stands of the aspen (Populus 

tremuloides Michx. and Populus grandidentata

Michx.) (Stone 2001). The three sites were established 

in consecutive years for ease in establishment and fi eld 

sampling logistics.

The fi rst site, established in 1992, is on a clay loam 

soil located on the Ottawa National Forest in the upper 

peninsula of Michigan, USA (Fig. 1). Soils at this 

location were classifi ed as Frigid Vertic Glossudalfs 

formed in lacustrine clays. This site occurs in the 

boreal moist Holdridge life zone (Lugo et al. 1999), 
3

at an approximate elevation of 350 m.a.s.l. Mean 

annual precipitation is about 77 cm. Stand age at 

time of establishment was 60 years, with a site index 

for aspen at age 50 years estimated at 17 m (Stone 

2001). Trees were harvested in late January and early 

February 1992. Snow depth averaged approximately 

80 cm over unfrozen soils (Stone 2001).

The second site, established in 1993, is on a silt 

loam soil located on the Chippewa National Forest 

in northern Minnesota, USA (Fig. 1). Soils were 

classifi ed as Frigid Haplic Glossudalfs formed in loess 

and till. This site occurs in the boreal moist Holdridge 

life zone at an approximate elevation of 410 m.a.s.l. 

Mean annual precipitation is about 64 cm. Stand 

age at time of study establishment was 70 years, with 

a site index for aspen at age 50 years estimated at 

23 m (Stone 2001). Trees were harvested in January 

and February 1993. Average snow depth increased 

over the period of harvest from approximately 

30 cm to 46 cm over discontinuously frozen soils; 

frost ranged in depth from 5 to 10 cm by end of 

harvest (Stone 2001).

Figure 1.—LTSP core and affi liate sites relative to the approximate range of commercial forest in the United States and 

portions of Canada (after Powers et al. 2005). Open circles indicate sites that had at least 10 years of data by 2005. The 

approximate locations of the Chippewa, Ottawa, and Huron National Forest LTSP sites are indicated.
4

The third site, established in 1994, is on a loamy sand 

soil on the Huron National Forest in eastern Michigan, 

USA (Fig. 1). Soils were classifi ed as Frigid Typic 

Udipsamments and Frigid Entic Haplorthods formed in 

outwash sands. This site occurs in the cool temperate 

moist Holdridge life zone at an approximate elevation 

of 240 m.a.s.l. Mean annual precipitation is about 

75 cm. Stand age at time of establishment was 

35 years, with a site index for aspen at age 50 years 

estimated at 19 m (Stone 2001). Trees were harvested 

in late January 1994. Average snow depth was 

approximately 37 cm over frozen soils; depth of 

frost averaged nearly 22 cm (Stone 2001).

Experimental Design

This research is based on a conceptual model (Fig. 2) 

developed by the National LTSP Program (Powers 

et al. 1990b, Powers et al. 2005) and applied to the 

northern Great Lakes aspen ecosystem study. 

The experimental design includes three factors 

(compaction, organic matter removal, year), with 

treatments arranged in a randomized complete block 

(replicates). There were three levels of soil compaction 

(C) and three levels of organic matter removal 

(OM), for a total of nine core treatments (Table 1). 

The levels of compaction were: C0

, no additional 

compaction above that due to harvesting; C1

, moderate 

compaction; and C2

, heavy compaction. The levels of 

organic matter removal were: OM0

, main bole only 

harvest; OM1

, aboveground total tree harvest; and 

OM2

, aboveground total tree harvest plus removal of 

forest fl oor. 

Figure 2.—Conceptual model used to guide the LTSP experimental design, indicating the overriding infl uence of soil porosity 

and site organic matter on fundamental processes that regulate primary productivity within climatic constraints (after Powers 

et al. 1998, Powers et al. 2005).
5

Each set of nine treatments was replicated three 

times at each geographic location on 50 m x 50 m 

treatment plot. Plots were established prior to logging 

and treatments were randomly assigned to the plots. 

After harvesting, the forest fl oor on the OM2

 treatment 

was removed by hand raking down to the top of the 

mineral soil and removing the material from the site 

prior to applying compaction treatments. Compaction 

treatments were applied during early spring with one 

or more passes using a Caterpillar tractor or frontend loader. Additional detail on the study areas and 

the equipment used to apply treatments can be found 

in Stone (2001). After treatment installation, all 

plots regenerated naturally to aspen and associated 

species, with the exception of the Chippewa National 

Forest site. At this site, some new aspen suckers 

were damaged from late application of compaction 

treatments; in these plots, additional aspen seedlings 

were planted to offset any potential losses in initial 

low stocking.

Field Measurements

Soil was collected and vegetation measurements were 

made prior to harvest, prior to compaction treatment 

(post-organic matter removal), post-compaction (i.e. 

post-treatment at end of the same growing season in 

which compaction was applied or year 0), in year 1, 

year 5, and year 10. Year 5 results are not presented 

in this report as earlier results have been reported 

elsewhere (Stone 2001, 2002). All sampling and 

measurements were conducted within the interior 40 m 

x 40 m of each plot, allowing a 5-m buffer around the 

target sample area. Initially, fi ve sample points were 

established systematically and uniformly within each 

treatment plot. In year 5, the number of points was 

expanded to eight, and in year 10 to nine points. 

Soil 

In each measurement year, a random azimuth and a 

distance (range of 1 to 3 m) from a sample point center 

was determined and used to locate a sampling area for 

soil. New sampling locations were constrained to be 

at least 1 m from the previous sample location. Soil 

samples were collected using a 30 cm deep by 6.35 cm 

diameter (190.5 cm3

) stainless steel core fi tted with a 

plastic tube. Tubes were removed and taken to the lab 

for processing. 

Vegetation 

In each treatment plot, aboveground herbaceous 

vegetation was collected at fi ve sample points in 1-m2

clip plots during late July to early August. Clip plot 

locations were determined similar to soil samples 

points, as described above. Woody shrub and tree 

vegetation was sampled in mid-September to October 

in 10-m2

 subplots centered on the sample points. All 

woody stems > 15 cm tall were measured and recorded 

by 2-mm diameter classes, with diameters measured at 

stem heights of 25 cm for individuals < 1.4 m tall and 

at 1.4 m for individuals reaching this height. 

Organic Matter Removal

Compaction OM0 OM1 OM2

C0

Main bole harvest, 

no additional compaction 

(C0

, OM0)

Total tree harvest, 

no additional compaction 

(C0, OM1)

Total tree harvest + forest 

fl oor removal, no additional 

compaction (C0, OM2)

C1

Main bole harvest, 

moderate compaction 

(C1

, OM0)

Total tree harvest, 

moderate compaction 

(C1, OM1)

Total tree harvest + forest fl oor 

removal, moderate compaction 

(C1, OM2)

C2

Main bole harvest, 

heavy compaction 

(C2, OM0)

Total tree harvest, 

heavy compaction 

(C2, OM1)

Total tree harvest 

+ forest fl oor removal, 

heavy compaction (C2, OM2)

Table 1.—Description of compaction and organic matter removal treatments.
6

Sample Preparation 

and Data Summarization

Plant material from the clip plots was oven dried at 

60 °C for 48 hours, and weighed to determine dry 

weight biomass. Allometric equations developed 

for this study (Perala and Alban 1993) were used to 

estimate aboveground biomass (Mg ha-1) of all woody 

species. Stem counts were used to determine densities 

of woody species (number ha-1). Estimates of biomass 

and densities were determined for aspen alone, as well 

as the total for all woody vegetation combined. 

Soil cores were sectioned into 0-10 cm, 10-20 cm and 

20-30 cm depth segments. Mineral soil samples from 

these sections were sieved to the 2-mm fraction to 

remove coarse fragments and root material. Samples 

were then oven-dried at 105 °C until no further loss 

of moisture could be detected after several repeated 

weighings. The following soil measures were 

determined from these samples: soil bulk density (Db, 

g cm-3); total soil carbon storage (Mg ha-1); total soil 

nitrogen storage (Mg ha-1); calcium (Ca, cmol kg-1); 

potasium (K, cmol kg-1); magnesium (Mg, cmol kg-1); 

sodium (Na, cmol kg-1); and effective cation exchange 

capacity (CECe, cmol kg-1). 

Fine fraction Db was determined as the mass of the 

< 2 mm diameter material, from each depth category, 

divided by the volume occupied by that material. Soil 

samples used in the Db determinations were combined 

within a treatment plot by depth category, thoroughly 

mixed, and subsampled for chemical analysis. Total 

C and N determinations were made on a Carlo Erba 

Model NA 1500 series 2 nitrogen/carbon/sulphur 

analyzer (CE Elantech, Inc., Lakewood, NJ). Cations 

were extracted using Mehlich 3 solution with detection 

by inductively coupled plasma analysis (Wolf and 

Beegle 1995). Total CECe was determined by 

summing Ca, Mg, K, and Na (Ross 1995).

Statistical Analysis

Each location in the study was analyzed separately 

due to large differences in climate and soil type. At 

each location, subplot data were averaged to derive 

treatment plot means for n=three replicates for 

treatment combinations, with the following exceptions: 

an error at the time of treatment installation at the 

Ottawa site resulted in only one replicate for the heavy 

compaction + main bole harvest treatment (C2

OM0), 

two replicates for the moderate compaction + main 

bole harvest treatment (C1

OM0), and fi ve replicates for 

the moderate compaction + total aboveground organic 

matter removal treatment (C1

OM2). For the Ottawa 

analyses, the mixed procedure in SAS (see below) was 

used to account for the unbalanced design (Littell et al. 

1996). 

All response variables were found to meet or nearly 

meet assumptions of normality. Covariance structures 

available within SAS were evaluated for each data 

set, with an autoregressive model determined as best 

fi t (smallest variance) for this mixed-model approach. 

The autoregressive structure has homogeneous 

variances and correlations that decline exponentially 

with time.

Repeated measures analyses were conducted on each 

response variable using the “proc mixed” procedure 

in SAS (SAS Institute Inc. 1999) with replications 

considered as random effects. The mixed effects model 

used was:

Yjklm = μY + αj

 + βk + γl + ρm + (αβ)jk + (αγ)jl

+ (αρ)jm + (βγ)

kl + (βρ)km + (γρ)lm + (αβγ)jkl

+ (αβρ)jkm + (αγρ)jlm + (βγρ)

klm + Єjklm

where 

Yjklm is the measured response for the mth replication 

of the lth year for the kth organic matter removal 

treatment and the jth compaction treatment, 

μY is the overall mean of Yjklm, 

αj

 is the fi xed effect due to jth compaction treatment, 

βk

 is the fi xed effect due to kth organic matter removal 

treatment, 

γl

 is the fi xed effect due to lth year, 

ρm is the random effect or block due to the mth

replication, 

(αβ)jk is the interaction fi xed effect due to the kth

organic matter removal treatment and the jth

compaction treatment, 
7

(αγ)jl is the interaction fi xed effect due to the lth year 

for the jth compaction treatment, 

(αρ)jm is the random effect due to the mth replication 

for the jth compaction treatment, 

(βγ)kl is the interaction fi xed effect due to the lth year 

for the kth organic matter removal treatment, 

(βρ)

km is the random effect due to the mth replication 

for the kth organic matter removal treatment, 

(γρ)

lm is the random effect due to the mth replication for 

the lth year, 

(αβγ)

jkl is the interaction fi xed effect due to the lth year 

for the kth organic matter removal treatment and 

the jth compaction treatment, 

(αβρ)jkm is the random effect due to the mth replication 

for the kth organic matter removal treatment and 

the jth compaction treatment, 

(αγρ)jlm is the random effect due to the mth replication 

of the lth year for the jth compaction treatment, 

(βγρ)klm is the random effect due to the mth replication 

of the lth year for the kth organic matter removal 

treatment, 

Єjklm is the random error due to the mth replication 

of the lth year for the kth organic matter removal 

treatment and the jth compaction treatment. 

Five-year intervals were used for analyses. The 

Satterthwaite degrees of freedom approximation 

was utilized in SAS, which can produce non-integer 

denominator degrees of freedom (Littell et al. 1996).

Comparisons were conducted via least squares means 

(LSM) to test for rejection of the null hypotheses that 

no differences existed among treatment means. The 

differences of LSM were computed in SAS using the 

“pdiff” option. In the case of the unbalanced design 

at the Ottawa site, the results of the LSM may not 

equal the average of the data because LSM imposes 

the model structure on the calculated mean and these 

adjusted means guarantee an unbiased estimation of 

treatment means (Littell et al. 1996, Spilke 2005). 

Twenty-four response variables were evaluated for 

each site, including bulk density (Db), total carbon, 

and total nitrogen at three soil depths, CECe, Ca, K, 

Mg, Na at two soil depths, aboveground total plant 

biomass, aspen biomass, herbaceous biomass, total 

woody species stem density and aspen stem density. 

Statistical tests were considered signifi cant at p ≤ 0.05. 

Our analyses produced a large number of comparisons 

among treatments and over time, however the focus 

of this report is primarily on tenth year responses, 

with some comparisons to year 0 values for selected 

variables. By design, the no additional compaction + 

main bole harvest treatment (C0

OM0) served as the 

control for testing the effects of all other treatments 

in this experiment (Powers 1999). Additionally, some 

comparisons were made with preharvest data. 

RESULTS

Interactions between Compaction 

and Organic Matter Removal 

Very few statistically signifi cant interactions between 

soil compaction and organic matter removal were 

detected for most variables within the fi rst decade 

since treatment. Of 75 possible two-way interactions 

we examined, only seven were signifi cant at 

p ≤ 0.05. This indicates that for the most part, 

responses to increasing compaction or increasing 

removal of organic matter were independent of the 

level of the other variable. The majority of signifi cant 

interactions were at the Chippewa National Forest silt 

loam soil site: CECe at 0-10 cm, Ca at 0-10 cm, along 

with total biomass, aspen biomass, and total stem 

density. Also, interactions for total stem density and 

Na at 10-20 cm at Ottawa National Forest clay loam 

soil site were signifi cant. Due to the minimal number 

of statistically signifi cant interactions, hereafter we 

test for differences among levels of one main effect 

(e.g., soil compaction) at the control level of the 

second main effect (e.g., organic matter removal). 

Soil Bulk Density

Loamy Sand Soil

Immediately after treatment, both moderate (C1) and 

heavy (C2

) compaction, pooled across organic matter 

removal treatments, on the loamy sand soil, resulted 

in signifi cant (p < 0.05) increases in bulk density 

compared to C0

 (no additional compaction) except that 
8

no signifi cant difference was detected between C0 and 

C1

 at 20-30 cm (Fig. 3). Moreover, bulk density on all 

treatments at all depths was elevated above the mean 

preharvest values (Fig. 3). For comparison, when 

compaction treatments were compared within just 

OM0

 (main bole only treatment), bulk density for both 

C1

 and C2 were still signifi cantly greater than C0 at all 

depths, although C1

 and C2 did not differ signifi cantly 

from each other (data not shown). For all compaction 

treatments, bulk density at 0-10 cm had signifi cantly 

decreased by year 10, compared to year 0, and bulk 

density for C1

 and C2 were no longer signifi cantly 

higher than C0

 (Fig. 4). At the two deeper depths, 

bulk density values at year 10 remained signifi cantly 

greater (p < 0.05) than the control (C0

) for moderate 

compaction (C1

) at 10-20 cm, and heavy compaction 

(C2

) at 10-20 and 20-30 cm. Also, at year 10, bulk 

density of all treatments at all depths remained higher 

than the mean preharvest values. 

Figure 3.—Means and standard errors for bulk density 

immediately following application (year 0) of C1

 (medium) 

and C2 (heavy) compaction treatments, relative to C0 (no 

additional compaction), for three soil depths on loamy sand 

soil at the Huron National Forest. Mean values for each 

compaction treatment are pooled across all organic matter 

removal treatments. Bars with common letters indicate 

means were not signifi cantly different (p ≤ 0.05). Signifi cance 

tests of compaction treatments apply within each soil depth 

category only. Dashed horizontal lines are mean preharvest 

bulk density values, pooled across all treatments by depth.

a

a

a

b

b a

c

c

b

0

0.5

1

1.5

2

0-10 cm 10-20 cm 20-30 cm

Bulk Density (g cm-3)

Compaction Treatment by Soil Depth

C 0

C 1

C 2

Figure 4.—Means and standard errors for bulk density 

of compaction treatments at 0-10 cm immediately after 

treatment (yr 0) and 10 years after treatment (yr 10) for the 

loamy sand soil at the Huron National Forest. Bars with 

common letters indicate means are not signifi cantly different 

(p ≤ 0.05). Dashed horizontal line is the mean preharvest 

bulk density pooled across all treatment. Compaction 

treatments are constrained to OM0

. 

a

c

d

b ab ab

0

0.5

1

1.5

2

C0 C1 C2

Bulk Density (g cm-3)

Compaction Treatment Time Comparison

Year 0

Year 10

Silt Loam Soil

Immediately after treatment, both moderate (C1) and 

heavy (C2

) compaction treatments, pooled across 

all organic matter removal treatments, resulted in 

signifi cantly greater (p < 0.05) bulk density compared 

to C0

, but only at 0-10 cm (Fig. 5). However, bulk 

densities on all treatments at all depths were elevated 

above the mean preharvest values (Fig. 5). For 

comparison, when compaction treatments were 

compared within just OM0

, bulk density for both C1

and C2

 were no longer signifi cantly different from C0

at the 0-10 cm soil depth (data not shown). Only heavy 

compaction (C2

) at 0-10 cm had a signifi cant decrease 

in bulk density by year 10, compared to year 0 (Fig. 6). 

At the two deeper depths, there were no treatment 

differences (p > 0.05) in bulk density at year 10. 

However, at year 10, bulk density of all treatments at 

all depths remained substantially higher than the mean 

preharvest values. 
9

Figure 5.—Means and standard errors for bulk density 

immediately following application (year 0) of C1 (medium) 

and C2

 (heavy) compaction treatments, relative to C0 (no 

additional compaction), for three soil depths on silt loam 

soil at the Chippewa National Forest. Mean values for each 

compaction treatment are pooled across all organic matter 

removal treatments. Bars with common letters indicate 

means were not signifi cantly different (p ≤ 0.05). Signifi cance 

tests of compaction treatments apply within each soil depth 

category only. Dashed horizontal lines are mean preharvest 

bulk density values, pooled across all treatments by depth.

a

a

a

b

a

a

b

a a

0

0.5

1

1.5

2

0-10 cm 10-20 cm 20-30 cm

Bulk Density (g cm-3)

Compaction Treatment by Soil Depth

C 0

C 1

C 2

Figure 6.—Means and standard errors for bulk density 

of compaction treatments at 0-10 cm immediately after 

treatment (yr 0) and 10 years after treatment (yr 10) for 

silt loam soil at the Chippewa National Forest. Bars with 

common letters indicate means are not signifi cantly different 

(p ≤ 0.05). Dashed horizontal line is the mean preharvest 

bulk density pooled across all treatment. Compaction 

treatments are constrained to OM0. 

a

b b

a

ab

a

0

0.5

1

1.5

2

C0 C1 C2

Bulk Density (g cm-3)

Compaction Treatment Time Comparison

Year 0

Year 10

Clay Loam Soil

Immediately after treatment, both moderate (C1) and 

heavy (C2

) compaction treatments, pooled across all 

organic matter removal treatments, on the clay loam 

soil, resulted in signifi cantly greater (p < 0.05) bulk 

density compared to C0

, at all depths, except that C1

and C0

 did not differ at 20-30 cm (Fig. 7). Bulk density 

of all treatments was substantially elevated above the 

mean preharvest value only at 0-10 cm (Fig. 7). Bulk 

density was moderately elevated above the preharvest 

value at 10-20 cm and similar to the preharvest 

value at 20-30 cm (Fig. 7). For comparison, when 

compaction treatments were compared within just 

OM0, bulk densities were signifi cantly different for 

most comparisons with C0

, except C1 at 0-10 cm and 

C2

 at 20-30 cm (data not shown). For all treatments, 

bulk density in year 10 was not signifi cantly different 

than year 0 at 0-10 cm, but bulk density was 

signifi cantly greater for C2

 compared to both C0 and 

C1

 at year 10 (Fig. 8). At the two deeper depths in 

year 10, bulk density was not signifi cantly different 

than the control (C0

) for either medium (C1) or heavy 

compaction (C2

) (data not shown). At year 10, bulk 

density of all treatments at 0-10 cm remained higher 

than the mean preharvest values (Fig. 8), whereas bulk 

density at deeper depths was very similar to preharvest 

values (data not shown). 
10

Figure 8.—Means and standard errors for bulk density 

of compaction treatments at 0-10 cm immediately after 

treatment (yr 0) and 10 years after treatment (yr 10) for 

the clay loam soil at the Ottawa National Forest. Bars with 

common letters indicate means are not signifi cantly different 

(p ≤ 0.05). Dashed horizontal line is the mean preharvest 

bulk density pooled across all treatments. Compaction 

treatments are constrained to OM0. Note: comparisons for 

treatment C2 are approximated by the analysis because 

n=1 for this treatment; the value shown if not a true mean 

and the standard error used is the estimated value for the 

comparisons.

a

ab

b

a

a

b

0

0.5

1

1.5

2

C0 C1 C2

Bulk Density (g cm-3)

Compaction Treatment Time Comparison

Year 0

Year 10

Soil Chemical Characteristics

Loamy Sand Soil

At year 10, no signifi cant differences (p > 0.05) were 

detected in total carbon or total nitrogen between the 

control and any compaction or organic matter removal 

treatment at any depth (Table 2). For most other 

variables, no signifi cant differences were detected, 

except CECe and Ca were signifi cantly lower than 

control for the OM2

 treatment at 0-10 cm and Na was 

signifi cantly greater than control for the C2

 treatment 

at 10-20 cm (Table 2).

Silt Loam Soil

At year 10, no signifi cant differences were detected in 

total carbon or total nitrogen between the control and 

any compaction or organic matter removal treatment at 

any depth (Table 3). Moreover, CECe, Ca, and Na did 

Figure 7.—Means and standard errors for bulk density 

immediately following application (yr 0) of C1 (medium) 

and C2

 (heavy) compaction treatments, relative to C0 (no 

additional compaction), for three soil depths on clay loam 

soil at the Ottawa National Forest. Mean values for each 

compaction treatment are pooled across all organic matter 

removal treatments. Bars with common letters indicate 

means were not signifi cantly different (p ≤ 0.05). Signifi cance 

tests of compaction treatments apply within each soil depth 

category only. Dashed horizontal lines are mean preharvest 

bulk density values, pooled across all treatments by depth. 

Note: comparisons for treatment C2 are approximated by the 

analysis because n=1 for this treatment; the value shown is 

not a true mean and the standard error used is the estimated 

value for the comparisons.

a

b a b a a c c b

0

0.5

1

1.5

2

0-10 cm 10-20 cm 20-30 cm

Bulk Density (g cm-3)

Compaction Treatment by Soil Depth

C 0

C 1

C 2

not differ between the control and any compaction or 

organic matter removal treatment at either depth 

(Table 3). Potasium was signifi cantly lower than the 

control in the OM1

 and OM2 treatments at 10-20 cm, 

and Mg was signifi cantly lower for treatments C1

 at 

0-10 cm and C2

 at 10-20 cm (Table 3).

Clay Loam Soil

At year 10, no signifi cant differences were detected 

in total carbon or total nitrogen between the control 

and any compaction or organic matter removal 

treatment at any depth (Table 4). Moreover, CECe, Ca, 

K, and Mg did not differ between the control and any 

compaction or organic matter removal treatment at 

either depth, while Na was signifi cantly lower than the 

control at 10-20 cm for both C1

 and OM1 treatments 

(Table 4). 
11

a

C0,OM0 (control) = no additional compaction and bole only harvest, C1 = medium compaction, C2 = heavy compaction, OM1 = total tree 

harvest, OM2 = total tree harvest + forest fl oor removal. Note: organic matter treatment means constrained to C0. Compaction treatment 

means constrained to OM0

.

*Indicates a signifi cant difference from the control (C0, OM0) at p ≤ 0.05.

Table 2.—Means (±standard errors) of soil chemical variables for organic matter removal and compaction 

treatments and the control at year 10 on loamy sand soil (Huron National Forest).

Soil depth CECe Ca K Mg Na Total C Total N

Treatmenta cm cmol kg-1 Mg ha-1

0-10 1.937 

±0.389

1.518 

±0.325

0.106 

±0.011

0.292 

±0.063

0.021 

±0.005 16.38 ±3.16 0.88 ±0.19

C0

, OM0 10-20 0.630 

±0.040

0.458 

±0.041

0.068 

±0.008

0.097 

±0.006

0.007 

±0.001 10.10 ±0.70 0.70 ±0.03

20-30 ----- ----- ----- ----- ----- 10.53 ±1.06 0.77 ±0.04

0-10 1.662 

±0.105

1.302 

±0.104

0.087 

±0.007

0.256 

±0.010

0.017 

±0.007 18.10 ±1.18 0.99 ±0.18

OM1 10-20 0.846 

±0.142

0.648 

±0.123

0.081 

±0.016

0.111 

±0.025

0.005 

±0.001 11.11 ±1.49 0.706 ±0.06

20-30 ----- ----- ----- ----- ----- 9.70 ±1.97 0.71 ±0.12

0-10 1.278* 

±0.105

0.952* 

±0.087

0.082 

±0.007

0.222 

±0.025

0.022 

±0.005 12.22 ±3.03 0.82 ±0.20

OM2 10-20 0.521 

±0.095

0.372 

±0.097

0.071 

±0.021

0.072 

±0.010

0.006 

±0.003 11.28 ±1.81 0.76 ±0.09

20-30 ----- ----- ----- ----- ----- 8.84 ±0.74 0.66 ±0.08

0-10 1.677 

±0.287

1.313 

±0.276

0.124 

±0.017

0.225 

±0.029

0.015 

±0.007 13.69 ±3.37 0.85 ±0.07

C1 10-20 0.569 

±0.114

0.412 

±0.103

0.063 

±0.007

0.075 

±0.014

0.019 

±0.004 9.09 ±0.66 0.79 ±0.09

20-30 ----- ----- ----- ----- ----- 10.33 ±0.34 0.73 ±0.06

0-10 1.459 

±0.266

1.128 

±0.237

0.105 

±0.018

0.219 

±0.016

0.007 

±0.003 17.88 ±3.03 0.88 ±0.12

C2 10-20 0.561 

±0.068

0.392 

±0.069

0.071 

±0.002

0.078 

±0.003

0.021* 

±0.002 15.06 ±2.65 0.92 ±0.04

20-30 ----- ----- ----- ----- ----- 12.01 ±0.79 1.10 ±0.19
12

a

C0,OM0 (control) = no additional compaction and bole only harvest, C1 = medium compaction, C2 = heavy compaction, OM1 = total tree 

harvest, OM2

 = total tree harvest + forest fl oor removal. Note: organic matter treatment means constrained to C0. Compaction treatment 

means constrained to OM0.

*Indicates a signifi cant difference from the control (C0

, OM0) at p ≤ 0.05.

Table 3.—Means (±standard errors) of soil chemical variables for organic matter removal and compaction 

treatments and the control at year 10 on silt loam soil (Chippewa National Forest).

Soil Depth CECe Ca K Mg Na Total C Total N

Treatmenta cm cmol kg-1 Mg ha-1

0-10 5.403 

±0.466

4.305 

±0.422

0.239 

±0.011

0.831 

±0.092

0.028 

±0.012 17.44 ±0.62 1.14 ±0.05

C0

, OM0 10-20 3.326 

±0.489

2.423 

±0.364

0.199 

±0.014

0.692 

±0.142

0.012 

±0.005 6.58 ±0.72 0.63 ±0.02

20-30 ----- ----- ----- ----- ----- 3.33 ±1.05 0.48 ±0.06

0-10 4.358 

±1.150

4.457 

±1.101

0.195 

±0.010

0.686 

±0.058

0.007 

±0.004 16.33 ±2.14 1.08 ±0.08

OM1 10-20 2.873 

±0.322

2.197 

±0.312

0.142* 

±0.007

0.522 

±0.051

0.012 

±0.004 5.01 ±0.26 0.58 ±0.05

20-30 ----- ----- ----- ----- ----- 2.42 ±0.70 0.54 ±0.03

0-10 5.467 

±0.734

3.940 

±0.665

0.206 

±0.023

0.647 

±0.057

0.007 

±0.004 16.85 ±1.83 1.12 ±0.11

OM2 10-20 2.813 

±0.335

2.108 

±0.290

0.151* 

±0.020

0.531 

±0.058

0.023 

±0.004 7.65 ±2.58 0.62 ±0.02

20-30 ----- ----- ----- ----- ----- 1.97 ±0.31 0.47 ±0.03

0-10 4.725 

±0.500

3.910 

±0.480

0.220 

±0.011

0.572* 

±0.025

0.023 

±0.010 15.95 ±3.40 1.17 ±0.15

C1 10-20 2.928 

±0.281

2.182 

±0.209

0.157 

±0.013

0.553 

±0.064

0.037 

±0.013 4.75 ±1.59 0.67 ±0.10

20-30 ----- ----- ----- ----- ----- 2.46 ±0.15 0.49 ±0.05

0-10 5.573 

±1.053

4.637 

±0.980

0.251 

±0.033

0.669 

±0.062

0.016 

±0.009 18.27 ±2.40 1.19 ±0.14

C2 10-20 2.841 

±0.378

2.195 

±0.367

0.157 

±0.011

0.461* 

±0.041

0.028 

±0.010 8.44 ±2.77 0.69 ±0.08

20-30 ----- ----- ----- ----- ----- 2.35 ±0.14 0.45 ±0.02
13

a

C0,OM0 (control) = no additional compaction and bole only harvest, C1 = medium compaction, C2 = heavy compaction, OM1 = total tree 

harvest, OM2

 = total tree harvest + forest fl oor removal. Note: organic matter treatment means constrained to C0. Compaction treatment 

means constrained to OM0. b

Values are not means of replicates as C2OM0 at Ottawa had only 1 replicate (n = 1).

*Indicates a signifi cant difference from the control (C0, OM0) at p ≤ 0.05.

Table 4.—Means (±standard errors) of soil chemical variables for organic matter removal and compaction 

treatments and the control at year 10 on clay loam soil (Ottawa National Forest).

Soil Depth CECe Ca K Mg Na Total C Total N

Treatmenta cm cmol kg-1 Mg ha-1

0-10 8.622 

±0.935

6.600 

±0.742

0.329 

±0.043

1.686 

±0.232

0.007 

±0.001 28.68 ±3.79 1.52 ±0.15

C0

, OM0 10-20 11.072 

±1.394

7.600 

±0.980

0.450 

±0.046

2.906 

±0.368

0.117 

±0.016 10.67 ±0.27 0.81 ±0.03

20-30 ----- ----- ----- ----- ----- 7.62 ±0.09 0.66 ±0.03

0-10 7.963 

±0.301

5.880 

±0.248

0.335 

±0.006

1.735 

±0.048

0.012 

±0.004 30.22 ±3.43 1.67 ±0.12

OM1 10-20 10.830 

±0.342

7.240 

±0.201

0.439 

±0.016

3.083 

±0.137

0.067* 

±0.010 11.55 ±1.09 0.89 ±0.06

20-30 ----- ----- ----- ----- ----- 8.18 ±0.47 0.69 ±0.02

0-10 8.521 

±0.565

6.167 

±0.433

0.370 

±0.020

1.972 

±0.134

0.012 

±0.006 31.18 ±3.59 1.67 ±0.17

OM2 10-20 10.700 

±1.106

7.200 

±0.757

0.427 

±0.018

2.983 

±0.312

0.089 

±0.026 12.40 ±1.50 0.94 ±0.03

20-30 ----- ----- ----- ----- ----- 9.31 ±1.35 0.67 ±0.01

0-10 7.515 

±0.259

5.425 

±0.125

0.303 

±0.029

1.771 

±0.113

0.017 

±0.001 32.78 ±3.39 1.85 ±0.08

C1 10-20 10.986 

±0.796

7.225 

±0.525

0.405 

±0.018

3.275 

±0.242

0.081* 

±0.011 10.27 ±0.59 0.95 ±0.01

20-30 ----- ----- ----- ----- ----- 7.49 ±0.07 0.67 ±0.03

0-10 8.034 5.750 0.362 1.908 0.014 26.35 1.54

C2

b 10-20 12.218 8.20 0.456 3.483 0.078 10.09 0.82

20-30 ----- ----- ----- ----- ----- 8.81 0.75
14

Vegetation Responses

Loamy Sand Soil

 Both total aboveground woody biomass and aspen 

biomass at year 10 were signifi cantly lower for the 

OM2

 treatment than the control. Aspen biomass was 

signifi cantly greater than the control for C1

 treatment 

and total biomass was marginally higher than the 

control for this treatment. Herbaceous biomass, total 

stem density, and aspen stem density did not differ 

signifi cantly between the control and any compaction 

or organic matter removal treatments 

(Fig. 9).

Silt Loam Soil

Both total aboveground woody biomass and mean 

aspen biomass were signifi cantly less for the OM2

, 

C1

 and C2 treatments than for the control. C1 and C2

had signifi cantly higher herbaceous biomass than the 

control and C2

 also had signifi cantly lower total stem 

density compared to control (Fig. 10). 

Clay Loam Soil

On the clay loam soil, the C1 treatment had a 

signifi cantly higher total biomass compared to the 

control. Total biomass and aspen biomass were 

signifi cantly higher than control for the OM2

 treatment. 

Herbaceous biomass, total stem density, and aspen 

stem density were not signifi cantly different from the 

control for any of the treatments (Fig. 11).

Figure 9.—Means and standard errors for aboveground biomass and density of vegetation groups 10 years after application 

of OM1 (whole-tree harvest), OM2 (whole-tree harvest plus forest fl oor removal), C1 (medium), and C2 (heavy) compaction 

treatments, relative to C0

OM0 (control: bole only harvest and no additional compaction) on loamy sand soil at the Huron 

National Forest. Bars with an asterisk indicate means were signifi cantly different from the control (p ≤ 0.05). 

0

5

10

15

20

25

30

Total Aspen H erbaceous

Mg ha-1

Biomass

C0OM0

OM1

OM2

C 1

C 2

0

20000

40000

60000

80000

100000

Total Aspen

Stems ha-1

Density
15

Figure 10.—Means and standard errors for aboveground biomass and density of vegetation groups 10 years after application 

of OM1 (whole-tree harvest), OM2 (whole-tree harvest plus forest fl oor removal), C1 (medium), and C2 (heavy) compaction 

treatments, relative to C0

OM0 (control: bole only harvest and no additional compaction) on silt loam soil at the Chippewa 

National Forest. Bars with an asterisk indicate means were signifi cantly different from the control (p ≤ 0.05). 

0

10

20

30

40

50

Total Aspen H erbaceous

Mg ha-1

Biomass

C0OM0

OM1

OM2

C 1

C 2

0

20000

40000

60000

80000

100000

Total Aspen

Stems ha-1

Density

Figure 11.—Means and standard errors for aboveground biomass and density of vegetation groups 10 years after application 

of OM1 (whole-tree harvest), OM2 (whole-tree harvest plus forest fl oor removal), C1 (medium), and C2 (heavy) compaction 

treatments, relative to C0OM0 (control: bole only harvest and no additional compaction) on clay loam soil at the Ottawa 

National Forest. Bars with an asterisk indicate means were signifi cantly different from the control (p ≤ 0.05). Note: n=1 for 

treatment C2

; it was not included in the analysis.

0

5

10

15

20

Total Aspen H erbaceous

Mg ha-1

Biomass

C0OM0

OM1

OM2

C 1

C 2

0

10000

20000

30000

40000

50000

Total Aspen

Stems ha-1

Density
16

DISCUSSION

In this study, we asked if there was an effect from 

organic matter removal or soil compaction on soil 

physical and chemical properties, 10 years after 

treatment application, and at what level of treatment 

an effect was evident. The compaction treatments 

increased soil bulk density above preharvest levels 

for all three soil types and at all soil depths, but 

particularly at 0-10 cm. Generally, the increase in 

bulk density paralleled the increasing intensity of 

the compaction treatment. Moreover, bulk densities 

generally remained above pretreatment levels on all 

soil types, 10 years after treatment, particularly at 0-10 

cm. However, by year 10, bulk density at 0-10 cm 

decreased and compaction treatments were no longer 

signifi cantly different from control, except on the 

clay loam soil where the high compaction treatment 

remained signifi cantly greater than the no-additional 

compaction treatment. Bulk density at the deeper soil 

depths remained signifi cantly greater than control for 

both compaction treatments on the loamy sand soil. 

Overall, by year 10, organic matter removal treatments 

had little effect on the soil properties we examined on 

any of the soil types. 

Soil chemical responses were generally minimal 

and specifi c to a soil texture. On the loamy sand 

soil (Huron National Forest), CECe and Ca were 

signifi cantly lower at the 0-10 cm soil depth with total 

tree plus forest fl oor removal, relative to the control. It 

appears that the removal of forest fl oor organic matter, 

in addition to total tree harvest, may result in lower 

Ca concentrations in the upper most 10 cm in the 

loamy sand soil. This may result in decreased inputs 

of Ca to the soil, after removal of the forest fl oor, 

and/or increased leaching for a short period of time. 

On the silt loam soil (Chippewa National Forest), Mg 

was signifi cantly less for the moderate compaction 

treatment at 0-10 cm and the heavy compaction 

treatment at 10-20 cm, while K was signifi cantly 

less than the control with total tree plus forest fl oor 

removal at 10-20 cm. On the clay loam soil (Ottawa 

National Forest), only one soil chemical measure 

(Na in C1

 at 10-20 cm) differed signifi cantly from the 

control at year 10.

Is there an effect of treatment on vegetation 

productivity and abundance after 10 years and at 

what level of organic matter removal or compaction 

is an effect evident? On the loamy sand soil (Huron 

National Forest), both total woody and aspen biomass 

were signifi cantly less with total tree harvest plus 

forest fl oor removal than the control, but biomass in 

the total tree harvest treatment did not differ from the 

control. Possibly, the decrease in biomass resulted 

from the reduction in Ca that was also noted in this 

treatment. Also at year 10, moderate compaction on 

the loamy sand soil signifi cantly increased aspen 

biomass compared to the control. A similar response 

for aspen biomass was found at year 5 and was 

attributed to increased water-holding capacity due to 

conversion of some macropores to micropore space 

with moderate compaction (Stone et al. 1998). This 

is consistent with results from an analysis of other 

LTSP sites, where biomass production increased 

with compaction on sand soils (Powers et al. 2005), 

presumably due to improved moisture status. However, 

our data also show that heavy compaction did not 

result in further improvements in moisture status 

above moderate compaction.

On the silt loam soil (Chippewa National Forest), 

total biomass and aspen biomass were signifi cantly 

less than the control with total tree harvest plus forest 

fl oor removal and with both levels of compaction. 

Moreover, total stem density was lower than the 

control on the highest compaction treatment. Neither 

total biomass nor aspen biomass differed from the 

control with total tree harvest alone. The reduction 

of biomass with total tree plus forest fl oor removal 

is probably not due to the reduction in K with this 

treatment, as K limitations are rare in most forests. 

Reductions in biomass with the compaction treatments 

likely was due to reductions in macropores, increased 

root restriction, reduced water infi ltration rates, and 

altered gaseous exchange (Alban 1991, Greacen and 

Sands 1980). Moreover, the timing of the compaction 

treatments at this site may have played a signifi cant 

role in the biomass reduction noted. Compaction 

treatments were applied in late spring after aspen 

suckering had already begun and resulted in some 

destruction of these suckers by the compaction 

equipment (Stone 2001, 2002, Stone and Kabzems 

2002). The extent to which this may have impacted 

aspen resuckering and subsequent biomass growth 

may have been signifi cant. While application of 

compaction treatments after aspen suckering likely 
17

had some impact on aspen regrowth, it is clear that 

total biomass and aspen biomass were greatly reduced 

by both moderate and high compaction, likely due to 

increased bulk densities with these treatments, which 

in turn may have resulted in reduced aeration and 

moisture availability. Herbaceous biomass at year 

10 was signifi cantly greater on the two compaction 

treatments and may refl ect reduced shading and 

competition with less woody vegetation on these 

treatments. 

On the clay loam soil (Ottawa National Forest), total 

tree harvest with forest fl oor removal signifi cantly 

increased both total and aspen biomass, while total 

tree harvesting alone did not differ signifi cantly from 

main bole only harvesting. The explanation for this 

is not apparent. Moderate compaction signifi cantly 

increased total biomass, suggesting that this level 

of compaction may have improved moisture status. 

Heavy compaction appeared to reduce both total and 

aspen biomass relative to the control, although there 

was only one replicate for this later treatment, so 

comparisons should be made with caution. However, 

the latter result is consistent with results from an 

analysis of other LTSP sites, which showed that 

biomass production generally declined with high 

compaction on clay soils (Powers et al. 2005). One 

explanation for increased aboveground biomass 

production with both the total tree harvest plus forest 

fl oor removal and moderate compaction treatments is 

that growth of individual aspen suckers may have been 

stimulated by the application of these treatments, while 

competition by less disturbance-tolerant species may 

have been reduced. In contrast, the heavy compaction 

treatment, with increased bulk density at 0-10 cm, may 

have damaged and destroyed many plant propagules, 

including tree roots.

Management Implications

If main bole harvest with no additional compaction 

is the standard against which to judge other 

treatments, then the tenth year results for aspen 

forests suggest that all three soil types can tolerate 

total tree harvest, with no additional compaction, 

without signifi cant reductions in total woody or aspen 

biomass production, as long as there is no additional 

compaction. The addition of forest fl oor removal to 

the total tree harvest resulted in negative impacts 

on biomass production for the loamy sand and silt 

loam soils, but had signifi cant positive effects on 

the clay loam soil. The caveat for these conclusions 

is that they are based on relatively short-term (10 

years) data; potentially, results could differ in future 

years. However, our results are supported by a study 

comparing main bole and whole-tree harvesting in 

other aspen ecosystems (Alban and Perala 1988), 

in which neither treatment negatively impacted soil 

properties in the short-term (8 years or less), even 

though whole-tree harvesting removed as much as 40 

percent of the available ecosystem Ca and signifi cant 

amounts of other nutrients in the upper mineral soil 

and forest fl oor. In Alban and Perala’s study, annual 

litterfall mass returned to preharvest levels within 6 

years and there were no differences between the two 

harvesting systems in forest fl oor weight, vegetative 

regrowth, and soil carbon. 

Our results suggest that heavy compaction is likely 

is be detrimental to woody plant production, at least 

in the short term. Moderate compaction may actually 

stimulate production on some soils (loamy sand and 

clay loam). However, we do not recommend that 

controlled compaction be used as a tool to improve 

productivity, as controlling the level of application 

would be diffi cult. Rather, the goal should be to 

minimize compaction to the extent possible in all cases. 

The long-term impacts on site quality and productivity 

of whole-tree harvesting and compaction remain 

largely unknown. For example, long-term impacts for 

soil cation depletion, for example Ca reduction on the 

loamy sand soil, remain unknown given that the aspen 

stands we studied are still relatively young and nutrient 

demanding (Alban and Perala 1990). Shorter rotations 

with more frequent entries for whole-tree tree harvests 

for biomass feedstocks add to that uncertainty of 

response and the need for caution. Long-term research 

such as the LTSP program is essential for increasing 

our understanding of these responses.

ACKNOWLEDGMENTS

We are grateful to the Forest Service soil scientists 

that have supported this work over the last decade, 

especially Sarah Mase, Joe Gates, Jim Barrot, Neil 

Babik, and Dave Shadis. We thank Mary Beth Adams 

and Randy Kolka for helpful comments on an earlier 

version of this report and John Stanovick for statistical 

support.
18

LITERATURE CITED

Alban, D.H. 1991. The impact of aspen harvesting 

on site productivity. In: Navratil, S.; Chapman, 

P.B., eds. Aspen management for the 21st century: 

proceedings of the symposium; 1990 November 

20-21; Edmonton, Alberta: Forestry Canada 

Northwest Regional Northern Forest Center and 

Poplar Council: 71-76.

Alban, D.H.; Perala, D.A. 1990. Impact of aspen 

timber harvesting on soils. In: Gessel, S.P.; 

Lactate, D.S.; Weetman, G.F.; Powers, R.F., eds. 

Sustained productivity of forest soils: proceedings 

of the 7th North American forest soils conference: 

1988 July 24-28; Vancouver, British Columbia: 

University of British Columbia, Faculty of Forestry 

Publication: 377-391.

Ballard, T.M. 2000. Impacts of forest management 

on northern forest soils. Forest Ecology and 

Management. 133: 37-42.

Greacen, E.L.; Sands, R. 1980. Compaction of forest 

soils: a review. Australian Journal of Soil Research. 

18: 163-189.

Grigal, D.F. 2000. Effects of extensive forest 

management on soil productivity. Forest Ecology 

and Management. 138: 167-185.

Hendrickson, O.Q.; Chatarpaul, L.; Burgess, D. 

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Great Lakes Region. Res. Pap. NRS-17. Newtown Square, PA: U.S. 

Department of Agriculture, Forest Service, Northern Research Station. 20 p.

Impacts of organic matter removal and compaction on soil properties and 

productivity are reported from the fi rst 10 years of the Long-Term Soil Productivity 

Study in Great Lakes aspen ecosystems. Organic matter removal treatments 

included main bole, total tree harvest, and total tree harvest with forest fl oor 

removal. Compaction treatments included minimal compaction, moderate, and 

heavy compaction. Treatments were replicated on a clay loam, silt loam, and 

loamy sand soils. Compaction treatments on all soils increased bulk density above 

preharvest levels. In most cases, bulk density at year 10 was still above preharvest 

levels. Total carbon, nitrogen, and cations showed little or no impact from treatment. 

Compaction and organic matter removal impacted aboveground productivity, 

however the responses were variable. Aboveground production declined on the 

loam soil with moderate and heavy compaction. Production increased with moderate 

compaction on the loamy sand and clay loam soils, but signifi cantly decreased with 

heavy compaction on clay loam soil. Total tree harvest with forest fl oor removal 

reduced production on the loamy sand and loam soils, while it increased production 

on the clay loam soil. Results from this study suggest that heavy compaction and/or 

high organic matter removals are detrimental to sustaining forest productivity. 

KEY WORDS: Long-term soil productivity (LTSP), whole-tree harvesting, 

 biomass harvesting, bioenergy, trembling aspen, soil compaction, 

 organic matter removal, harvesting impacts

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