Upload
others
View
4
Download
0
Embed Size (px)
Citation preview
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