The effect of sulfur and nitrogen additions on nutrient cycling and vegetative cover composition

in sandplain grassland restoration plots in Edgartown, MA

Fiona Jevon

Harvard University

Mentor: Chris Neill

Ecosystems Center, Marine Biological Laboratories

December 19th

, 2011

Abstract

Sandplain grasslands of the northeastern United States are early successional, costal

systems that support many rare and uncommon species. The conversion of these ecosystems for

agriculture in the 19th

and 20th

centuries resulted in the loss of many of these important species.

Because of the long lasting effects of cultivation, abandoned farm land tends to be dominated by

non-native vegetation. One theory for restoring these systems to native sandplain grassland is

using elemental sulfur to lower the pH of the soil. This study is based on an experiment in

Edgartown, MA which applies many different treatments to an abandoned agricultural field with

the aim of finding the most effective method for restoring the area to sandplain grassland. Soil

was collected from these experimental plots and tested for pH and inorganic nitrogen. Non-

native fescue grass was also grown in pH manipulated soil in growth chambers to determine a

pH response curve. From the experimental plots, sulfur additions were found to lower the pH of

the soil and increase the total cover of native species. Nitrogen treatments increased the cover of

non-native species, but had no significant effects on the native species. From the in-lab pot

experiment, non-native species were found to be inherently inhibited by low pH soils. Total

biodiversity was unchanged by either type of treatment. Based on these results, sulfur additions

are an effective method for restoring agricultural land to native-dominated sandplain grassland

systems.

Keywords: Native species, nitrogen, non-native species, pH, restoration, sandplain grassland,

sulfur.

Introduction

Sandplain grasslands are early successional, often coastal ecosystems found primarily in

the northeastern United States. These systems support a diverse group of uncommon plant and

animal species (Eberhardt et al, 2003). Unfortunately, many of these ecosystems have been lost

over the past 200 years as they were converted to agricultural land (Motzkin and Foster, 2003).

Today they are still in rapid decline; sandplain grasslands are naturally early succesional

systems, but due to human intervention such as fire suppression and reforestation the early

successional stage cannot be maintained (Neill, draft paper). Currently the only remaining

systems exist on small fragmented areas in costal New England and New York (Neill, draft

paper). Conservation and restoration of these systems has become a priority, not only because of

their unique species composition but also because they maintain the heterogeneity of the land;

naturally they are kept in earlier succession stages by disturbances such as fires, salt water spray,

and of forest clearing, while other systems follow natural, linear succession and become forests

(Neill, draft paper). On Martha’s Vineyard, much of the sandplain grassland was converted to

farmland, but even though agriculture has been abandoned in the area, the system cannot

naturally return to its previous state. This is because formerly cultivated lands are easily invaded

by non-native plants due to the long lasting effect that cultivation has on soil chemistry (Von

Halle and Motzkin, 2007). For example, many farms use nitrogen and lime fertilizers, which

increase the pH and available nitrates in the soils. The effects of these fertilizers are still present

even long after cultivation of the soil has ended (Von Halle and Motzkin, 2007). The active

restoration of the native sandplain grassland species will allow for this unique ecosystem to

expand and provide greater areas of habitat for the rare species which depend on it.

Restoring sandplain grasslands from agricultural fields requires a method of returning a

non-native dominated system to a native dominated one. One of the theories behind restoring

agricultural lands to native sandplain grasslands is based on the concept that non-native species

are better adapted for nutrient rich soils, as many of them are fast growing and have high

nitrogen requirements (Wilson and Tilman, 2002). They therefore tend to dominate abandoned

farmland, which has residual high nutrient levels due to historical fertilizer use. Native species

tend to be the opposite; they are adapted for the naturally more nutrient poor soil (Davis et al

2000). Therefore in order to restore native species it is necessary to lower the nutrient levels in

the soil. One method of doing this is lowering the pH of the soil; this has been found to decrease

the nitrification rates, therefore decreasing the available nitrogen in the form of nitrate (Ste Marie

and Pare, 1999). Therefore one technique used for restoration is lowering the pH of the soil by

adding elemental sulfur fertilizer (Weiler, 2011). Theoretically, this affects which types of

species are more likely to establish in that soil, and favor the establishment of native species over

non-natives.

With this study I tried to determine how both sulfur and nitrogen additions to a

previously cultivated field affect the available nutrient levels, particularly nitrate. Theoretically,

nitrogen additions should increase nitrate concentrations, and sulfur additions should decrease

nitrate concentrations due to lowering the pH. I also want to determine if the sulfur and nitrogen

additions affect the number and cover of native species. If the above hypothesis is true, I would

expect that the nitrogen additions should have lower native cover and higher non-native cover,

while the opposite should occur in the sulfur addition plots. Finally I want to find the growth

response curve of a non-native grass species. If non-natives establish less predominantly in the

lower pH plots, this could be due either to the fact that native plants out compete them for the

limited nutrient resources, or due to an inherent inhibition of the non-natives to low pH soils. A

growth response curve showing if and at what pH a non-native grass responds negatively to low

pH in the absence of competition will show which of these hypotheses is true.

Methods

Site description

The experimental restoration plots at Herring Creek in Edgartown, MA began in 2007,

when Neill et al set up 180 plots on a previously agricultural field adjacent to native sandplain

grassland (Katama airfield). The plots were set up in 5 different blocks, which were each broken

into a 6x6 grid of 36 square plots (Figure 1). These small plots were randomly assigned to

treatments, and treated in the summer of 2007. Thus each treatment has 5 repetitions. The

treatments consist of various methods for decreasing the prevalence of non-native species and

increasing native species. For the purpose of this project I considered only the following

treatments: control, control tilled, low sulfur addition, medium sulfur addition, high sulfur

addition, low nitrogen addition, medium nitrogen addition, and high nitrogen addition (Figure 1).

The control plots were plots left entirely untouched. The tilled control plots were tilled and re-

seeded with native seed from the Katama Airfield in 2008, but then left untreated. The treated

plots were also tilled and re-seeded, then treated with various levels of either nitrogen or

elemental sulfur fertilizer, also in 2008. Data on the soil characteristics and vegetative cover of

these plots has been collected since 2007; therefore data from 2007 is pre-treatment data and data

from 2008 is the first year of data post-treatment. The point of this experiment is to determine

the most effective method for restoring previously agricultural land to native sandplain

grassland.

Field and lab methods

For the purposes of this project I sampled only from the sulfur addition, nitrogen

addition, control and tilled control plots. In the field, I used a 10 cm deep corer to collect 2 soil

samples for the following plots: In the lab, I homogenized each soil sample, and weighed out 10

grams of wet soil, then dried these samples in an oven at 60 degrees for 2 days and weighed them

again to determine the wet:dry ratio of soil from each plot. I then measured the initial pH and

initial nitrate and ammonium stocks. This was done by extracting a 10 g subsample with 100 mL

of 1 M KCl in a sealed cup. These 64 cups were then placed on a shaker table for 1.5 hours then

allowed to settle for 24 hours. Then they were filtered using 25 mm GF/F swinnex filters into

scint vials, and frozen until analysis. Then a 0-100uM standard curve was run on both the

Lachat and Shimadzu 1601 analyzers, and the samples were analyzed for NO3 on the Lachat and

NH4 on the Shimadzu 1601.

The remaining samples were incubated in closed plastic bags at 25 degrees C. I extracted

another 10 g of each sample and analyzed for nitrate and ammonium concentrations after 8 days

and again after 16 days. Net mineralization and nitrification rates for each of the plots was then

calculated based on the change in concentration over the incubation period. I also measured pH

at each of these three time points.

I compared my data to data collected on the pH, inorganic nitrogen concentrations in the

soil and mineralization and nitrification rates over the past 5 years. I also compared these soil

characteristics to data collected on the overlying vegetation. In particular I was interested in the

total number of species per plot, the number of natives and non-natives, and the total cover of

natives and non-natives.

Plant growth experiment

In addition to collecting samples from the experimental plots, I grew the non-native

fescue grass (Festuca arundinacea). I tilled 1 gram (about 438 seeds) of a store bought mix of

fescue seed (Black Beauty) into the top inch of soil, which was a 1:1 mix by volume of sterile

potting soil and sand. I used a control and 4 different treatments of dilute sulfuric acid in order

to manipulate the pH of the soil to determine the response of a non-native plant to different

levels of acidity. Each pot was leached through with 350 ml of the given dilution of sulfuric acid

initially, and then watered with that dilution as necessary in order to maintain the acidity level.

The control pots were watered with distilled water, the S1x pots (4 reps) were watered with

1:10,000 dilute sulfuric acid, the S2x pots (4 reps) were watered with 1:2000 dilute sulfuric acid,

the S3x pots were watered with 1:600 dilute sulfuric acid and the S4x pots were watered with

1:200 dilute sulfuric acid. The pH of the pots was checked 5 times over the 18 day growing

period and if necessary additional acid was added to pots. If the pH was stable I watered the pots

with DI to equalize the amount of liquid I gave each pot. After 18 days, I harvested the above

and belowground biomass of each pot. I dried and weighed the above and below ground

biomass and counted the blades which sprouted in each pot to determine a percent germination.

Results

The experimental plot data on soil characteristics showed that nitrification rates across all

plots regardless of treatments were not significantly related to pH (Figure 2). However,

nitrification rates from previous years did have a weak positive correlation (Figure 3). Pools of

extractable nitrate tended to be higher in less acidic soils (Figure 4). Lower soil pH also

correlated weakly with higher native species across all plots (Figure 5).

The overall vegetative dynamics in the plots can be seen in Figure 6. In the tilled plots

collectively, three dominant, non-native grass species (Anthoxanthum odorata, Bromus inermis

and Dactylis glomerata) initially decreased sharply, then slowly increased again over time.

Ragweed (Ambrosia artemisiifolia), a native ruderal species, increased initially then decreased.

Little bluestem (Schizachyrium scoparium), a target native species for sandplain restoration,

doesn’t appear until after 2009 but increased steadily. In the untilled plots, little bluestem never

appears, and ragweed only established slightly. The old grasses are highly variable, but stay

dominant over the entire time period.

Looking specifically at the treatments, the average pH is lower in the sulfur plots, and

about equal in the nitrogen addition and control plots (Figure 7). Nitrate concentrations are

positively correlated with nitrogen addition, and negatively correlated to sulfur addition (Figure

8). Total species number is approximately the same across the six treatments and similar to the

tilled control, and all of these are higher than untouched control (Figure 9). Additionally, there is

a large increase in total number of species between 2008 and 2009 in all plots, and a small

decrease in 2011 in the high sulfur treatment.

The medium and high nitrogen addition plots have a stable number of native species from

2009 to 2011, and slightly more than the low nitrogen and the controls (Figure 10). The sulfur

addition plots have more highly variable numbers of native species across the years, and native

species numbers decrease slightly in 2011 in the medium and high sulfur treatments.

Total native cover, on the other hand, is highest in the high sulfur addition plots, followed by the

medium and low sulfur additions (Figure 11). The native cover in the sulfur addition plots also

increases over time. In the nitrogen addition plots, native cover is highly variable and all three

treatments have similar cover to the controls.

The number of non-natives is not significantly different across the treatments or from the

tilled control, but it does seem to be decreasing over time in the sulfur addition plots (Figure 12).

Non-native cover in 2011 is slightly lower in the nitrogen addition plots than in the controls, but

nitrogen addition and non-native cover is positively correlated. Non-native cover is correlated

negatively with sulfur addition (Figure 13).

Plant growth experiment

The percent germination of the pots approximately followed a second degree polynomial

curve; at an average soil pH of around 5, the percent germination of the grass began to decline

rapidly (Figure 14). Aboveground biomass also responded sharply to pH levels lower than 5, but

at pH levels between 5 and 7 didn’t seem to show much difference (Figure 15). Belowground

biomass had a very similar curve to aboveground biomass (Figure 16). The root:shoot ratio

seemed to have a optimal pH of around 5.5, and high root:shoot at low pH.

Discussion

The lack of correlation between nitrification rates and pH possibly shows that in this

case, the acidic soils are not affecting the nitrification process significantly. However the

correlation between the same variables in previous years at the same sites indicates that we

cannot conclusively disprove this relationship. In fact, there is a correlation between the pools of

extractable nitrate and the pH of the soil, which indicates that the pH is in fact related to the

available nutrient levels in the soil. Additionally, the pH also correlates with total native

vegetative cover. This indicates that theory of restoration through pH manipulation is manifest

in these plots.

Looking generally at what occurred vegetatively in the experimental plots, we can see

some of the expected dynamics. The initial tilling of the treated plots significantly decreased the

cover of non-native “old grasses”, but they began to re-emerge again after a few years. In the

first year after treatment, the fast-growing ruderal native species Ragweed spiked, but decreased

again. As the ragweed decreased, Little bluestem began to increase, and continues to grow.

Little bluestem is a target species for sandplain grassland restoration, so the steady increase over

the last 2 years is a promising sign for these results.

Focusing in on how effectively the treatments were functioning specifically, the sulfur

addition treatments have significantly lowered the pH from the pretreatment levels, even

compared to the control plots which have also become slightly more acidic. This shows that the

treatment of sulfur is impacting the soil in the expected manner. Additionally the nitrate

concentration is much lower in the sulfur treatments than the other plots, showing that the

decrease in pH in these plots seems to decrease the nitrate as well. The nitrogen treatments have

also had the expected effects on the soil; the nitrogen treatment plots have higher levels of nitrate

than the control.

The changes in soil chemistry also affected the vegetative cover. The nitrogen treatments

seem to slightly increase biodiversity (measured by total number of species) compared to the

control plots. This is somewhat surprising, as we might expect the additional nitrogen to favor

only fast-growing, non-native plants. The sulfur additions also seem to increase biodiversity

slightly compared to the controls, but the diversity seems to be decreasing over time. This

decrease is likely due to a shift in dominance; as a few species become established as the

dominant players in these plots, species that are not well established are out-competed. Little

bluestem, for example, has become dominant in some of these plots.

The total number of native species has the same trend to total number of all species.

Again, the recent drop in number of native species in the sulfur addition plots is likely due to the

increased dominance of certain native species, such as Little bluestem. The total native cover in

the nitrogen addition plots does not meet the expected hypothesis; increasing nitrate levels

should decrease total native cover, but the 3 nitrogen treatments all have similar native cover to

each other and to the controls. This is possibly due to the fact that these plots already had high

nutrient levels due to their previous cultivation, so the addition of nitrogen in fact doesn’t make a

large difference to the vegetation even though it is increasing the available nutrients in the soil.

The sulfur plots do meet expectations; higher sulfur additions have higher native cover, which is

exactly what the theory would lead us to expect. Additionally the native cover in the sulfur plots

is increasing over time; this relates again to the idea that certain native species are becoming

dominant, and increasing their total cover over time.

The number of non-native species is approximately the same across the treatments, which

is not what we expected. The treatments should have caused higher numbers in the nitrogen

addition plots and lower number in the sulfur addition plots. However there is a downward trend

in the sulfur addition plots over time, so it seems that over time the treatments are working as

anticipated. More notably, the total non-native cover in 2011 is significantly lower in the sulfur

addition plots than the control or the nitrogen addition plots. This suggests that the pH

manipulation is favoring the establishment of native species over non-natives. The opposite is

true in the nitrogen and control plots- the positive correlation between nitrogen addition and non-

native cover shows that the nitrogen additions are having some of the expected effects in that

nitrogen addition seems to weakly promote an increase in non-native cover.

The apparent negative correlation between sulfur addition and non-native cover could be

explained either by the natives being able to out-compete the non-natives for the already low

levels of nutrients, or by an inherent pH inhibition in the non-natives. Based on data from the

pot experiment, non-native fescue grass has an inherent inhibition to low pH soils. The percent

germination in the pots shows that below a threshold pH of about 5, the non-native grass is

strongly inhibited in how many of the seeds are able to germinate. This compares to a general

literature value of about 5.3 for a crucial soil pH turning point, below which nitrification rates are

strongly inhibited (Ste-Marie and Pare, 1999). The above and belowground biomass had a

similar threshold level of about 5, below which the total biomass decreased significantly. This

also compares to the average pH of the sulfur plots, which in 2011 were 4.46, 4.18 and 3.86.

The control plots were around a pH of 5.4. This implies that it is not just out-competition that is

limiting the establishment of non-natives in the sulfur addition plots, but an inherent inhibition of

non-natives to grow in low pH soils. The root: shoot ratio relationship seems to show that plants

growing in a pH between about 5.2 and 6.2 expend the least energy on building roots relative to

shoots, implying that this is the pH range at which the plant feels least stressed. Particularly at

lower pH soil, the grass tends to expend relatively more energy building roots, implying that it is

more nutrient stressed. However due to the small number of samples, it is also possible that this

correlation is not showing a true relationship. Overall, this experiment shows a strong inhibition

of non-native growth below a pH of 5. While this is possibly due to the changes in nitrification,

it could also be a simple pH inhibition. Further research on the mechanism of pH inhibition

could show this conclusively.

Restoration implications

Regardless of the mechanism, elemental sulfur fertilizer seems to be a very effective

method of achieving sandplain restoration goals. Without significantly effecting overall

biodiversity, the lowering of the soil pH seems to favor the establishment of target native

vegetative species, such as little bluestem. It also seems to create an environment that is much

less favorable for the non-native species, so that over time the treatment becomes more effective.

Acknowledgements

I would like to thank Chris Neill for all of his help and support during the process of

completing this project. I also want to thank Rich McHorney, Stef Strebel and Carrie Harris for

their endless patience with me in helping me with lab work. Finally I want to thank Emily

Rogers for her assistance with my field work.

Literature Cited

Davis, Mark, J. Phillip Grime, Ken Thompson. 2000. Fluctuating Resources in Plant

Communities: A General Theory of Invasibility. Journal of Ecology 88(3): 528-534.

Eberhardt, Robert W, David R Foster, Glenn Motzkin, Brian Hall. 2003. Conservation of

Changing Landscapes: Vegetation and Land use history of Cape Cod National Seashore.

Ecological Application 13 (1): 68-84.

Motzkin, Glenn and David R. Foster. 2002. Grasslands, heathlands and shrublands in costal

New England: historical interpretations and approaches to conservation. Journal of

Biogeography 29: 1569-1590.

Nagel, Laura. 2005. Use of soil carbon amendments on a Martha’s Vineyard grassland

restoration site. Unpublished.

Neill, Chris. A proposal for sandplain ecosystem restoration at Herring Creek, Martha’s

Vineyard, Massachusetts. Unpublished.

Ste-Marie, Catherine and David Pare. 1999. Soil, pH and N availability effects on net

nitrification in the forest floors in a range of boreal forest stands. Soil Biology and

Biogeochemistry 31 (11): 1579-1589.

Von Holle, Betsy and Glenn Motzkin. 2007. Historical land use and environmental determinants

of nonnative plant distribution in coastal southern New England. Biological Conservation 36: 33-

43.

Weiler-Lazarz, Annalisa. 2011. Factors limiting native species establishment in former

agricultural fields.

Wilson, Scott and David Tilman. 2002. Quadratic variation in old field species richness along

gradients of disturbance and nitrogen. Ecology 83(2) 4992-504.

Appendix Contents

Figure 1: Experimental layout of Herring Creek Farm and plots considered in this paper

Figure 2: Nitrification vs. pH in 2011

Figure 3: Nitrification vs. pH in 2009

Figure 4: Nitrate concentration vs. pH

Figure 5: Total native cover vs. pH

Figure 6: Vegetative dynamics of all plots over time

Figure 7: Average pH by treatment over time

Figure 8: Average nitrate concentration by treatment over time

Figure 9: Average biodiversity by treatment over time

Figure 10: Average total number of natives by treatment over time

Figure 11: Average total native cover by treatment over time

Figure 12: Average total number of non-natives by treatment over time

Figure 13: Average total non-native cover by treatment in 2011

Figure 14: Percent germination vs. pH of experimental pots

Figure 15: Aboveground biomass vs. pH of experimental pots

Figure 16: Belowground biomass vs. pH of experimental pots

Figure 17: Root:shoot ratio vs. pH of experimental pots

Appendix

Block B

37 38 39 40 41 42

43 44 45 46 47 48

49 50 51 52 53 54

55 56 57 58 59 60

61 62 63 64 65 66

67 68 69 70 71 72

Block C

73 74 75 76 77 78

79 80 81 82 83 84

85 86 87 88 89 90

91 92 93 94 95 96

97 98 99 100 101 102

103 104 105 106 107 108

C Control

CT Tilled control

N1x Low nitrogen addition

N2x Medium nitrogen addition

N3x High nitrogen addition

S1x Low sulfur addition

S2x Medium sulfur addition

S3x High sulfur addition

Block A

1 2 3 4 5 6

7 8 9 10 11 12

13 14 15 16 17 18

19 20 21 22 23 24

25 26 27 28 29 30

31 32 33 34 35 36

Block D

109 110 111 112 113 114

115 116 117 118 119 120

121 122 123 124 125 126

127 128 129 130 131 132

133 134 135 136 137 138

139 140 141 142 143 144

Block E

145 146 147 148 149 150

151 152 153 154 155 156

157 158 159 160 161 162

163 164 165 166 167 168

169 170 171 172 173 174

175 176 177 178 179 180

Figure 1: This is the experimental layout of the Herring Creek Farm Experiment. The colored

plots represent plots which I sampled from, and the white blocks represent other treatments not

considered in this paper.

Figure 2: Net nitrification rate versus pH of all considered Herring Creek plots in 2011.

-0.5

0.0

0.5

1.0

1.5

2.0

0 1 2 3 4 5 6

Ne

t n

itri

fica

tio

n (u

g N

/g d

ry s

oil/

day

)

pH

Figure 3: Net nitrification rate versus pH of all considered Herring Creek plots in 2009.

R² = 0.2895

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 1 2 3 4 5 6 7 8

Ne

t n

itri

fica

tio

n (

ug

N/g

dry

so

il/d

ay)

pH

Net Nitrification vs pH 2009

Figure 4: Nitrate concentration versus pH in all Herring Creek plots considered for this project in

2011.

R² = 0.2658

0

1

2

3

4

5

6

7

3 3.5 4 4.5 5 5.5 6

uG

NO

3/g

dry

so

il

pH

Figure 5: Total native cover versus pH in subset of Herring Creek plots in 2011.

R² = 0.397

0

20

40

60

80

100

120

140

160

3 3.5 4 4.5 5 5.5 6

Per

cen

t n

ativ

e co

ver

pH

Figure 6: Percent cover of old grass (Anthoxanthum odorata, Bromus inermis and Dactylis

glomerata), Ragweed (Ambrosia artemisiifolia), and Little bluestem (Schizachyrium scoparium)

over time in the tilled and untouched control plots.

0

10

20

30

40

50

60

70

80

2007 2008 2009 2010 2011

Per

cen

t co

ver

Tilled plots

Old grass

Ragweed

Little Bluestem

0

10

20

30

40

50

60

70

80

2007 2008 2009 2010 2011

Control plots

Figure 7: Average pH across six treatment types and two types of control plots over time.

0

1

2

3

4

5

6

7

C CT N1 N2 N3 S1 S2 S3

pH

Treatment

2007

2009

2010

2011

Figure 8: Average nitrate concentration in six treatment type and two types of controls in 2011.

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

C CT N1 N2 N3 S1 S2 S3

ug

NO

3/g

dry

so

il

Treatment

Figure 9: Average total number of species in six treatments and two controls over time.

0

5

10

15

20

25

30

C CT N1 N2 N3 S1 S2 S3

Nu

mb

er

of

spe

cie

s

Treatment

2007

2008

2009

2010

2011

Figure 10: Average total number of native species in six treatments types and two controls over

time.

0

2

4

6

8

10

12

14

16

18

C CT N1 N2 N3 S1 S2 S3

Nu

mb

er

of

nat

ive

sp

eci

es

Treatment

2007

2008

2009

2010

2011

Figure 11: Average percent native cover in six treatments types and two controls over time.

0

20

40

60

80

100

120

140

C CT N1 N2 N3 S1 S2 S3

Pe

rce

nt

nat

ive

co

ver

Treatment

2007

2008

2009

2010

2011

Figure 12: Average total number of non-native species in six treatment types and two controls

over time.

0

2

4

6

8

10

12

14

16

C CT N1 N2 N3 S1 S2 S3

Nu

mb

er

of

no

n-n

ativ

e s

pe

cie

s

Treatment

2007

2008

2009

2010

2011

Figure 13: Average total cover of non-natives across 6 treatment types and two controls in 2011.

0

20

40

60

80

100

120

140

160

C CT N1 N2 N3 S1 S2 S3

Pe

rce

nt

no

n-n

aitv

e c

ove

r

Treatment

Figure 14: Percent germination versus pH of experimentally grown non-native fescue grass.

R² = 0.9401

0

10

20

30

40

50

60

70

80

90

0 1 2 3 4 5 6 7 8

Pe

rce

nt

germ

inat

ion

(%

)

pH

Figure 15: Aboveground biomass versus pH of experimentally grown non-native fescue grass.

R² = 0.9279

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0 1 2 3 4 5 6 7 8

Dry

ab

ove

gro

un

d b

iom

ass

(gra

ms)

pH

Figure 16: Belowground biomass versus pH of experimentally grown non-native fescue grass.

R² = 0.943

0

0.1

0.2

0.3

0.4

0.5

0.6

0 1 2 3 4 5 6 7 8

Dry

be

low

gro

un

d b

iom

ass

(gra

ms)

pH

Figure 17: Root:shoot ratio versus pH of experimentally grown non-native fescue grass.

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 1 2 3 4 5 6 7 8

Ro

ot:

sh

oo

t ra

tio

pH