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Charcoal Effects on Soil Solution Chemistry and Growth of Koeleria macrantha in the Ponderosa Pine/Douglas-fir Ecosystem

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We conducted laboratory and greenhouse experiments to determine whether charcoal derived from the ponderosa pine/Douglas-fir ecosystem may influence soil solution chemistry and growth of Koeleria macrantha, a perennial grass that thrives after fire. In our first experiment, we incubated forest soils with a factorial combination of Douglas-fir wood charcoal generated at 350°C and extracts of Arctostaphylos uva-ursi with and without the addition of glycine as a labile N source. These results showed that charcoal increased N mineralization and nitrification when glycine was added, but reduced N mineralization and nitrification without the addition of glycine. Charcoal significantly reduced the solution concentration of soluble phenols from litter extracts, but may have contributed bioavailable C to the soil that resulted in N immobilization in the no-glycine trial. In our second experiment, we grew K. macrantha in soil amended with charcoal made at 350°C from ponderosa pine and Douglas-fir bark. Growth of K. macrantha was significantly diminished by both of these charcoal types relative to the control. In our third experiment, we grew K. macrantha in soil amended with six concentrations (0, 0.5, 1, 2, 5, and 10%) of charcoal collected from a wildfire. The data showed increasing growth of K. macrantha with charcoal addition, suggesting some fundamental differences between laboratory-generated charcoal and wildfire-produced charcoal. Furthermore, they suggest a need for a better understanding of how temperature and substrate influence the chemical properties of charcoal.
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ORIGINAL PAPER
Charcoal effects on soil solution chemistry and growth
of Koeleria macrantha in the ponderosa pine/Douglas-
fir ecosystem
Michael J. Gundale &Thomas H. DeLuca
Received: 26 July 2005 /Revised: 10 April 2006 / Accepted: 12 April 2006 / Published online: 3 June 2006
#Springer-Verlag 2006
Abstract We conducted laboratory and greenhouse experi-
ments to determine whether charcoal derived from the
ponderosa pine/Douglas-fir ecosystem may influence soil
solution chemistry and growth of Koeleria macrantha,a
perennial grass that thrives after fire. In our first experi-
ment, we incubated forest soils with a factorial combination
of Douglas-fir wood charcoal generated at 350°C and
extracts of Arctostaphylos uva-ursi with and without the
addition of glycine as a labile N source. These results
showed that charcoal increased N mineralization and
nitrification when glycine was added, but reduced N
mineralization and nitrification without the addition of
glycine. Charcoal significantly reduced the solution con-
centration of soluble phenols from litter extracts, but may
have contributed bioavailable C to the soil that resulted in
N immobilization in the no-glycine trial. In our second
experiment, we grew K. macrantha in soil amended with
charcoal made at 350°C from ponderosa pine and Douglas-
fir bark. Growth of K. macrantha was significantly
diminished by both of these charcoal types relative to the
control. In our third experiment, we grew K. macrantha in
soil amended with six concentrations (0, 0.5, 1, 2, 5, and
10%) of charcoal collected from a wildfire. The data
showed increasing growth of K. macrantha with charcoal
addition, suggesting some fundamental differences between
laboratory-generated charcoal and wildfire-produced char-
coal. Furthermore, they suggest a need for a better
understanding of how temperature and substrate influence
the chemical properties of charcoal.
Keywords Charcoal .Soil solution chemistry .
Douglas-fir and ponderosa pine ecosystems
Introduction
It is well-established that fire alters N cycling in the
ponderosa pine/Douglas-fir (Pinus ponderosa/Psuedotsuga
menziesii) ecosystem (Neary et al. 1999; Hart et al. 2005).
Nitrogen availability has been shown to increase immedi-
ately after fire (Covington and Sackett 1990,1992; DeLuca
and Zouhar 2000) and may remain elevated on the scale of
months to years as a result of enhanced mineralization
(Covington and Sackett 1990,1992; Monleon et al. 1997;
Kaye and Hart 1998; Gundale et al. 2005). Numerous
processes that increase N mineralization after fire have been
identified, including improved substrate quality (White
1991,1994; Fernandez et al. 1997; Pietikainen et al.
2000a), death of roots and soil organisms resulting in a
large labile organic N pool (DeBano et al. 1979; Dunn et al.
1979; Diaz-Ravina et al. 1996; Neary et al. 1999), and a
reduction in C to N ratios due to preferential loss of C
during combustion (Gundale et al. 2005). A potentially
overlooked factor that may also enhance N cycling after fire
is the addition of charcoal to soils.
Several recent studies have shown that charcoal has the
potential to greatly enhance soil fertility. Amazonian forest
soils amended centuries ago with charcoal and manure still
maintain some of the highest biodiversity and productivity
Biol Fertil Soils (2007) 43:303311
DOI 10.1007/s00374-006-0106-5
M. J. Gundale (*):T. H. DeLuca
Department of Ecosystem and Conservation Sciences
University of Montana,
32 Campus Drive,
Missoula, MT 59812, USA
e-mail: mjgundal@yahoo.com
T. H. DeLuca
e-mail: tom.deluca@cfc.umt.edu
of any soils within the Amazon basin (Glaser et al. 2001,
2002; Mann 2002). In boreal forest soils, charcoal was
shown to enhance N cycling by ameliorating the inhibitory
effects of litter extracts from late-successional species,
which in turn promotes growth of early-successional
species (Zackrisson et al. 1996; Wardle et al. 1998; DeLuca
et al. 2002; Berglund et al. 2004). Recently, DeLuca et al.
(2006) found that the addition of wildfire-formed charcoal
to ponderosa pine forest soils increased nitrification rates.
Charcoal may enhance soil fertility through a variety of
mechanisms. Increased N turnover may occur by charcoal
sorption of high C:N organic molecules from the soil
solution (Zackrisson et al. 1996; Wardle et al. 1998; Glaser
et al. 2002), resulting in reduced microbial N immobiliza-
tion and higher net mineralization and nitrification rates. In
addition, charcoal may remove specific groups of organic
molecules, including polyphenol or monoterpene com-
pounds that are thought to inhibit nitrification (Rice and
Pancholy 1972; Zackrisson et al. 1996; DeLuca et al. 2002;
Berglund et al. 2004). Sorption of organic molecules, along
with the gradual breakdown of charcoal, may initiate
humus formation and, thus, enhance long-term soil fertility
(Glaser et al. 2002). Charcoal may also enhance soil
fertility by creating habitat for microbes within its porous
structure (Pietikainen et al. 2000b).
Despite these potential roles that charcoal may have in
increasing soil fertility, its ecological role in forest ecosys-
tems, such as ponderosa pine/Douglas-fir, has received little
attention. We conducted three separate experiments using
low-temperature charcoal to investigate whether charcoal
influences soil solution chemistry and growth of an early
successional species. In our first experiment, our objective
was to determine whether charcoal had an influence on soil
solution chemistry after addition of the extracts of a late
successional species, Arctostapholos uvi-ursi, via surface
adsorption of phenolic compounds. We hypothesized that
charcoal added to a ponderosa pine forest soil will
effectively sorb the phenol fraction in litter extracts, which
would correspond with enhanced N cycling.
In our second experiment, our objective was to compare
the influence of charcoal made from the bark of two
species, ponderosa pine and Douglas-fir, on growth of
Koeleria macrantha, a perennial grass species that thrives
after fire disturbance in western Montana ponderosa pine/
Douglas-fir forests. Bark charring during low-intensity
wildfire is a potentially significant source of charcoal in
this system. Charred bark may gradually slough from trees
after fire and become incorporated in the soils surrounding
trees. It is recognized that ponderosa pine is a more fire-
adapted species than Douglas-fir; thus, an intriguing
hypothesis is that charred bark of the more fire-adapted
species will have a stronger positive effect on N cycling
processes and plant growth.
In our third experiment, our objective was to determine
whether charcoal generated during a wildfire would have
any effect on K. macrantha growth and to determine
whether this relationship is dependent on soil charcoal
concentration. We hypothesized that wildfire charcoal will
positively influence K. macrantha and that this effect will
increase as a function of soil charcoal concentration.
Collectively, these three experiments address our central
hypothesis that charcoal will alter solution chemistry by
sorbing phenols and enhancing N cycling, which in turn
will improve the growth of early successional species.
Materials and methods
All three experiments utilized field-collected soil, which
was collected from the subsurface horizon (2030 cm, B
w
Horizon) of a forest soil associated with low elevation
(1,100 m) ponderosa pine/Douglas-fir vegetation in western
Montana, USA. The soil is a sandy-skeletal, mixed, frigid
Typic Dystrustepts. This ecosystem is characterized by low
annual rainfall (<350 mm annually) with approximately
50% falling as snow during the winter months. Soil was
collected during the month of September, returned to the
lab, upon which they were sieved (4 mm) and homoge-
nized. We then added one part sand to three parts field
moist soil (by mass) to decrease fertility and increase
porosity and gas exchange, such that nitrification would not
be limited by low O
2
availability. The sand fraction was
purchased as filter grade silica sand (for pool filters) and
was washed with 1 M HCl, followed by distilled water,
before being homogenized with field collected soil. This
sand-amended soil had a pH of 6.8, electrical conductance
of 91.2 μSm
1
, and had a textural distribution of 71%
sand, 21% silt, and 8% clay.
All experiments also included the addition of either
laboratory-generated charcoal from Douglas-fir and ponder-
osa pine or charcoal collected in the field after a wildfire.
Laboratory charcoal was generated by burying wood or bark
from these species in silica sand and heating at 350°C for 2 h.
Charcoal was then ground and sieved as specified for each
experiment. Various physical and chemical properties of these
charcoals were measured (Table 1). Charcoal pH was
measured from a 4:1 slurry of deionized water to charcoal.
Electrical conductance (EC) was measured from charcoal
paste (2:1 distilled water and charcoal). Cation exchange
capacity (CEC) was estimated on charcoal samples via NHþ
4
replacement where 1 g of charcoal was rinsed twice with
25 ml of 1 M ammonium acetate (pH 7) to saturate exchange
sites. Excess saturating solution was removed from charcoal
samples with three consecutive washes with 25 ml of 95%
ethyl alcohol. Sorbed NHþ
4was then extracted with 25 ml of
2 M KCl and analyzed on a segmented flow analyzer (Auto
304 Biol Fertil Soils (2007) 43:303311
Analyzer III, Bran Luebbe, Chicago, IL) using the Berthelot
reaction (Willis et al. 1993). Charcoal density was measured
by measuring dry mass of intact charcoal pieces and
measuring volume displacement in deionized water. Total
C was measured via dry combustion on a Fissions Elemental
Analyzer (Milano, Italy). Soluble and total phenols were
measured by extracting 1 g of ground charcoal in 25 ml of
deionized water and 50% methanol, respectively, and were
analyzed using the Prussian Blue Method (Stern et al. 1996).
Extractable NHþ
4and NO
3(Mulvaney 1996)wereextracted
by shaking 1 g of charcoal for 30 min in 25 ml of 2 M KCl,
and then filtering through Whatman #2 filters. The extracts
were analyzed for NHþ
4
N using the Berthelot reaction
(Willis et al. 1993)andNO
3
N by the cadmium reduction
method (Willis and Gentry 1987) on a segmented flow
analyzer (Auto Analyzer III). Soluble PO3
4was extracted by
placing1gofcharcoalin25mlof0.01MCaCl
2
for 30 min.
Extracts were filtered through Whatman #42 filter paper and
then analyzed on a segmented flow analyzer using the
molybdate method as described by Kuo (1996).
Experiment 1: charcoal sorption potential
We conducted a laboratory incubation study using the soil
described above, where Douglas-fir charcoal and extract of
Arctostaphylos uva-ursi were added in a factorial combi-
nation yielding four treatments (Charcoal/Extract, Charcoal/
No extract, No Charcoal/Extract, and No Charcoal/No
extract). Each treatment was replicated five times and
consisted of 300 g of soil and placed into mason jars. The
treatments receiving charcoal addition received a 2%
charcoal amendment (20 g/kg). Charcoal was generated in
a muffle furnace by submerging Douglas-fir wood in sand
and heating it at 350°C for 2 h. Charcoal was ground and
sieved through a 4.75-mm sieve. A. uva-ursi extract was
made by extracting 100 g of A. uva-ursi leaves in 1 l of
deionized water for 24 h and filtering this extract through
Whatman #42 filters. The total phenol concentration of this
extract was 267.5 mg/l. Extract treatments received 25 ml
of this extract. No-extract treatments received an equivalent
volume of deionized water. Soils were homogenized
following this addition. This addition brought the soil in
each mason jar to a water content of approximately 60%
WHC. Mason jars were incubated in the dark for 14 days
after which a portion of the soil was extracted and analyzed.
This entire experiment was repeated exactly as described
above but with glycine added to all mason jars as a source of
highly labile organic N to stimulate a more marked N
response. Glycine, a simple amino acid that is readily
mineralized to NHþ
4, was added to each mason jar at a rate
of 75 mg/jar (250 mg/kg of soil). These two experiments will
hereafter be referred to as the glycine and no-glycine trials.
Experiment 2: effects of bark charcoal on plant growth
This greenhouse experiment consisted of three treatments
(Douglas-fir charcoal, ponderosa pine charcoal, and a
control) using the sand-amended soil described above to
evaluate the influence of charcoal source on K. macrantha.
Each treatment consisted of 20 replicate pots where each
pot received 1.5 kg of soil, and charcoal treatments received
a 2% (by mass) charcoal amendment. One percent of this
charcoal was homogenized into the soil, while the other 1%
was evenly distributed on the soil surface. We made
charcoal from Douglas-fir and ponderosa pine in the
laboratory by burying bark of each species in silica sand
and heating to 350°C in a muffle furnace for 2 h. Charcoal
was ground and sieved (<1 mm) using a Wiley mill.
Organic horizons (O
i
,O
e
, and O
a
) were added to the surface
of each pot to add an additional and substantial mineraliz-
able pool of plant essential nutrients, as well as to provide a
source of bioavailable organic C that may influence soil
nutrient transformations. This organic material was ran-
domly collected (as described in Gundale et al. 2005) from
a ponderosa pine/Douglas-fir forest that had not been
exposed to fire for approximately 80 years and originated
from numerous species, including understory and overstory
species, but appeared to be primarily composed of
undecomposed ponderosa pine and Douglas-fir litter. The
organic material was homogenized and 100 g was added to
the surface of each pot. A mixed bed ionic resin capsule
(Unibest, Bozeman, MT) was placed in the center of each
pot to sorb nutrients throughout the duration of the
experiment.
K. macrantha was grown in these pots between October
2004 and March 2005 under ambient light conditions. An
average greenhouse temperature of 21°C was maintained. K.
macrantha seeds (Western Native Seeds, Coaldale, CO)
were germinated in a separate soil medium, and a single
seedling was transplanted into each pot. Pots were watered
3 days a week throughout the duration of the experiment. At
Table 1 Chemical properties of four charcoal types (df Douglas-fir,
pp ponderosa pine, wildfire wildfire collected) used in the laboratory
and greenhouse experiments
df Wood df Bark pp Bark Wildfire
pH 4.15 4.18 4.81 5.74
EC (μSg
1
) 20.5 24.2 111.6 141.5
CEC (cmol
c
kg
1
) 20.66 19.42 34.48 29.35
Density (g cm
3
) 0.30 0.08 0.21 0.29
Total C (%) 72.9 72.4 71.5 82.3
Soluble phenols (μgg
1
) 34.9 30.7 43.4 48.2
Total phenols (μgg
1
) 441.7 148.1 810.4 393.8
PO3
4(μgg
1
)0.94 0.84 2.46 0.95
NHþ
4(μgg
1
)7.12 9.0 5.6 38.3
NO
3(μgg
1
)0.12 0.3 0.0 4.4
Biol Fertil Soils (2007) 43:303311 305
the end of the experiment, resin capsules were recovered,
and soil was rinsed from roots. Plants were oven-dried at 65°C,
and above- and belowground masses were measured.
Experiment 3: effect of wildfire charcoal on plant growth
Charcoal collected from a wildfire site was added to the soil
described above at a rate of 0, 0.5, 1, 2, 5, and 10%, and
placed in greenhouse pots seeded with K. macrantha to
determine whether an increase in soil charcoal content has
any influence on the growth of K. macrantha.Each
treatment (n=10) was established by adding 1.0 kg of
charcoal-amended soil per pot. The charcoal used in this
experiment differed from both previous experiments because
it was collected after a wildfire rather than generated in the
laboratory. Large particles (>5-cm diameter) of charcoal
were collected in the spring of 2004 from the Black
Mountain Fire (August 2003), Missoula, MT, (DeLuca et
al. 2006). It was impossible to decipher the species origin of
this charcoal, but it was likely primarily Douglas-fir and
ponderosa pine wood and bark char. The charcoal particles
were crushed, using a mallet, producing fragments ranging
from a diameter of 2 cm to microscopic. No attempt was
made to discriminate against any size class in an attempt to
simulate the range of charcoal particle sizes likely incorpo-
rated into the soil under natural conditions. Organic horizon
materials (50 g) were collected from a forest stand not
exposed to fire for over 80 years and added to the surface of
each pot as described earlier. All other experimental
conditions were run identically to experiment 2.
Laboratory analyses
At the end of experiment 1, 30 g of soil were extracted with
2 M KCl and analyzed for NHþ
4and NO
3as described
above. Amino N was measured on these same extracts
using the ninhydrin method (Moore 1968). Soluble phenols
were extracted by shaking 30 g of soil for 1 h with 50 ml of
deionized water followed by filtration. Sorbed phenols were
extracted by shaking 30 g of soil with 50% methanol for
24 h followed by filtration. Phenols in these extracts were
measured using the Prussian blue method (Stern et al.
1996). Respiration was measured at the end of the
incubation by incubating 50 g dry weight equivalent soil
in a sealed container with 20 ml 1 M NaOH traps for 3 days
(Zibilske 1994).
Mixed bed ionic resin capsules (Unibest) were used in
experiments 2 and 3 to determine solution NHþ
4;NO
3, and
PO
4throughout the duration of the experiments. Capsules
were placed in the center of each pot, directly beneath each
plant, and were removed and extracted in 10 ml of 2-M KCl
three consecutive times. We analyzed NHþ
4;NO
3,and
PO3
4from these extracts as described previously.
Statistical analyses
Data in experiment 1 meeting assumptions of normality and
homoscedasticity were analyzed using two-factor analysis
of variance (ANOVA), where extract and charcoal were
entered as fixed factors under the general linear model.
Variables not meeting these assumptions were analyzed
using a KruskalWallis test (KW test). This analysis tests
for differences among treatments but does not evaluate the
significance of individual factors or interactions between
factors.
Data in experiments 2 and 3 were analyzed using one-
factor ANOVA followed by the StudentNewmanKeuls
post hoc procedure. Different letters are used to display post
hoc differences. Data not meeting assumption of normality
and homoscedasticity were compared using KW tests,
which were not followed by post hoc procedures. All
analyses were conducted using SPSS 12.0 software.
Results and discussion
Experiment 1: low temperature charcoal sorption potential
Both charcoal and litter extract significantly influenced
numerous soil chemical variables (Fig. 1). In both glycine
and no-glycine trials, litter extract negatively influenced
extractable NO
3concentrations. The negative influence of
A. uva-ursi on extractable NO
3reported here is consistent
with our previous studies in ponderosa pine forest soils
(DeLuca et al. 2006) and with studies that showed that litter
from late-successional boreal species, such as the ericaceous
shrub Empetrum hermaphroditum, diminishes net nitrifica-
tion (DeLuca et al. 2002; Berglund et al. 2004). Charcoal
had an unexpected negative effect on NO
3in the no-glycine
trial. In contrast, the addition of charcoal increased NO
3
concentrations in the glycine trial. These results may be a
function of the charcoal we used in this study, which was
generated at a low temperature (350°C). Charcoal contains a
significant concentration of bioavailable C, specifically
soluble phenols (Table 1) that may have caused net NO
3
immobilization (Schimel et al. 1996) in the no-glycine trial
where low NHþ
4concentrations existed (Rice and Tiedje
1989). The NO
3immobilization effect did not occur in the
glycine trial because NHþ
4limitations were drastically
reduced with glycine addition. In addition, higher rates of
nitrification in the glycine trial likely occurred because this
process was not limited by a lack of substrate availability
(glycine additions resulted in high NHþ
4concentrations).
The higher rate of nitrification associated with charcoal
in the glycine trial is consistent with the finding reported by
DeLuca et al. (2006), which suggests that charcoal may
sorb compounds from litter extract and the soil solution that
306 Biol Fertil Soils (2007) 43:303311
are inhibitory to nitrifying bacteria, or sorb carbon-rich
molecules that would otherwise stimulate microbial immo-
bilization of N.
A. uva-ursi extract had a strong positive effect on NHþ
4
in both no-glycine and glycine trials because it likely
contained some NHþ
4and substrates that are rapidly
mineralized to NHþ
4. Charcoal had a strong negative effect
on NHþ
4in both no-glycine and glycine trials. The
mechanisms for this pattern may differ between the two
trials. In the no-glycine trial, the most likely explanation for
reduced NHþ
4is that immobilization occurred as a function
of N limitations in these soils. In the glycine trial, higher
rates of nitrification associated with charcoal likely con-
tributed to lower NHþ
4concentrations.
Both charcoal and extract significantly influenced con-
centrations of amino N that represent a highly labile
Phenols (
µ
µ
g g-1)
0
5
10
15
20
Soluble Phenols
Sorbed Phenols
Soluble Phenols
KW test **
Sorbed Phenols
Charcoal ***
Extract ***
Charcoal x Extract NS
0
5
10
15
20
Soluble Phenols
KW test *
Sorbed Phenols
Charcoal ***
Extract **
Charcoal x Extract NS
0
50
100
150
200 Amino N
Charcoal ***
Extract *
Charcoal X Extract NS
Ammonium
Charcoal ***
Extract **
Charcoal x Extract NS
Nitrate
KW test ***
Extractable N (
µ
µ
g g-1)
0
5
10
15
20
Amino N
NH4
+
NO3
-
Amino N
Charcoal *
Extract ***
Charcoal x Extract **
Ammonium
KW test ***
Nitrate
Charcoal ***
Extract ***
Charcoal x Extract *
S S + E S + C S + C + E
Respiration (
µ
µ
g CO2 day-1)
0.0
0.1
0.2
0.3
0.4
0.5
Respiration
Charcoal NS
Extract *
Charcoal x Extract NS
S S + E S + C S + C + E
0.0
0.1
0.2
0.3
0.4
0.5
Respiration
Charcoal NS
Extract NS
Charcoal x Extract **
ab
cd
ef
No-Glycine Trial Glycine Trial
Fig. 1 Extractable amino N, NH þ
4, and NO
3[mean (SE)] without
(a) and with (b) glycine addition; soluble (water extracted) and sorbed
phenols (methanol extracted) [mean (SE)] without (c) and with (d) glycine
addition; and basal soil respiration [mean (SE)] without (e) and with
(f) glycine addition, from a 14-d soil incubation experiment where soils
were amended with a factorial combination of charcoal and extracts from
Arctostaphylos uva-ursi leaves (Ssoil only, S+E soil plus extract, S+C soil
plus charcoal, S+C+E soil plus charcoal plus extract). Data were analyzed
with a two-factor ANOVA where significance was tested for Charcoal,
Extract, and Charcoal × Extract interaction. Data that did not meet
parametric assumptions of normality or homoscedasticity were analyzed
using a KruskalWallis (KW) test. Asterisks represent statistical signifi-
cance (pvalue, ns >0.1, *<0.05, **<0.01, ***<0.001)
Biol Fertil Soils (2007) 43:303311 307
fraction of organic N that can be rapidly mineralized.
Glycine, which is a simple amino N molecule, stimulated
rapid rates of N mineralization and resulted in increased
amino N concentrations, which suggests that the added
glycine was not completely utilized and that substrate
limitations were eliminated during this trial. In glycine and
no-glycine trials, the litter extract resulted in higher
concentrations of amino N to soils. The effect of charcoal
on amino N, however, differed in glycine and no-glycine
trials. In the no-glycine trial, charcoal significantly in-
creased amino N concentrations. This response may have
occurred because charcoal sorbed phenolic molecules that
otherwise would form insoluble complexes with amino N
groups. In contrast, charcoal had a negative effect on amino
N in the glycine trial, which is likely the result of charcoal
enhancing microbial utilization of glycine.
As expected, A. uva-ursi extract significantly increased
phenols (soluble and sorbed) in both trials. The addition of
charcoal to soil significantly diminished the soluble phenol
concentration while increasing the pool of sorbed phenol.
This result is consistent with several studies in the boreal
forest that have demonstrated a high capacity of charcoal to
adsorb phenolic compounds (Zackrisson et al. 1996; Wardle
et al. 1998; DeLuca et al. 2002; Berglund et al. 2004).
Solubility of these fractions likely influences the degree to
which they are bioavailable and, therefore, their ability to
interfere with N transformations (Harborne 1997). It is
interesting to note that total phenols (sorbed and soluble)
was higher in the charcoal-only treatment of both trials than
the control, demonstrating that charcoal itself adds a
substantial amount of total phenol to the soil (Table 1).
These phenols are likely derived from the components of
wood, such as lignin that are degraded during charcoal
formation. It is unclear what effect these phenols have on
soil processes, but it is likely that they could be utilized as a
food source by microbes, stimulating N immobilization.
Soil respiration showed little response to charcoal in
glycine or no-glycine trials. In the no-glycine trial, the extract
significantly increased soil respiration. Extract and charcoal
had no individual effect on soil respiration in the glycine trial;
however, the interaction between charcoal and extract showed
a significant effect. We speculate that this response may
reflect that amines and degradable carbon substrates were
better utilized by microbes when phenolic molecules in the
same extract were sorbed by charcoal.
These data demonstrate that low-temperature charcoal
effectively sorbs soluble phenols from A. uva-ursi extracts,
which in turn stimulates nitrification, provided nitrification is
not substrate-limited. Our results are consistent with
Berglund et al. 2004 and DeLuca et al. (2002), who showed
that the effect of charcoal on nitrification only occurred when
a labile N source was also present. These studies are also
consistent with the Terra Preta phenomenon reported in the
Amazonian basin where charcoal and manure (high labile N
concentration) were historically incorporated into the soil
(Glaser et al. 2001,2002). Today, these soils maintain the
highest fertility in the region, which may in part be a
function of the interactive effect of charcoal and manure.
Experiment 2: effects of bark charcoal on plant growth
In this experiment, we unexpectedly found that charcoal
from both species diminished growth of K. macrantha
relative to the control with reduced mass in both above-
ground and belowground growth (Table 2). K. macrantha
growing in pots with Douglas-fir charcoal had a signifi-
cantly higher root to shoot ratio than the other treatments
that appeared to be primarily driven by low aboveground
biomass. This data suggests that there is likely no difference
in the effect of ponderosa pine and Douglas-fir charcoal on
plant species in this ecosystem.
We found that resin-sorbed NHþ
4and NO
3were
significantly higher in the Douglas-fir charcoal treatment
relative to the ponderosa pine charcoal treatment and the
control. Resin-sorbed PO3
4was significantly higher in both
Douglas-fir and ponderosa pine charcoal treatments than
the control. These results may be interpreted in several
ways. First, they may indicate higher mineralization and
nitrification rates in the presence of charcoal as suggested
by experiment 1. If higher mineralization occurred in the
presence of charcoal, it is unclear why a corresponding
increase in plant growth did not occur. It is possible that
some toxic substance was generated during charcoal
formation that inhibited root growth of K. macrantha,
despite a positive effect on nutrient availability (Fritze et al.
Table 2 Plant mass and resin sorbed nutrients (mean±SE, n=20) from
a greenhouse experiment where soil was amended with 2% charcoal
made from Douglas-fir (df) and ponderosa pine (pp) bark at 350°C
df
Charcoal
pp
Charcoal
no
Charcoal
p
value
Total mass (g) a1.6 (0.2) a1.9 (0.1) b2.5 (1.0) <0.001
Root mass (g) a0.8 (0.1) a0.9 (0.1) b1.2 (0.1) <0.05
Aboveground
mass (g)
a0.7 (0.1) b1.0 (0.1) c1.3 (0.1) <0.001
Root to shoot
ratio
a1.1 (0.1) b0.9 (0.1) b0.9 (0.1) <0.01
NHþ
4(μg resin
capsule
1
)
a4.6 (0.9) b1.4 (0.6) b2.2 (0.8) <0.05
NO
3(μg resin
capsule
1
)
a1,770.8
(286.2)
b935.8
(241.9)
b581.5
(211.8)
<0.01
PO3
4(μg resin
capsule
1
)
a5.1 (1.4) a5.6 (0.9) b0.5 (1.2) <0.05
Letters in bold indicate differences using the StudentNewmanKeuls
post hoc procedure
308 Biol Fertil Soils (2007) 43:303311
1998; Villar et al. 1998). These toxic substances are likely
to be more abundant in low temperature charcoals, such as
used in this experiment, and may be prone to volatilization
at higher temperatures. An additional explanation is that
charcoal may have enhanced soil macroporosity, allowing
more soil solution to pass through capsules, resulting in
misleading resin-sorbed nutrient concentrations.
Experiment 3: effect of wildfire charcoal on plant growth
In support of our hypothesis, natural charcoal collected from a
wildfire showed a positive effect on growth of K. macrantha
(Table 3). Both total and aboveground masses were signifi-
cantly higher in pots amended with 5 and 10% charcoal
addition than the control. Pots with lower charcoal content
(0.52%) showed an intermediate growth response. No
significant shift in allocation to above- or belowground
structures was detected across the charcoal gradient. As in
experiment 2, resin-sorbed NO
3and PO3
4decreased as plant
growth increased. These results suggest that these measure-
ments do not reflect any direct effect charcoal may have on
nutrient cycling, but are rather indicative of the solution nutrient
concentration as influenced by plant uptake. No difference in
resin sorbed NHþ
4occurred across the charcoal gradient.
The different responses of K. macrantha to charcoal in
experiments 2 and 3 suggest that charcoal produced in a
laboratory may be greatly different from charcoal generated
during wildfire. Differences in charring conditions may
influence the chemical and structural nature of charcoal and
may therefore change its influence on soil solution
chemistry. One potentially important difference between
laboratory- and wildfire-collected charcoal was the ratio of
soluble phenols to NHþ
4concentration extracted from the
charcoals (Table 1). While all charcoal had relatively
similar soluble phenol contents, which may stimulate
microbial N immobilization, high NHþ
4concentrations
may have offset this immobilization effect when wildfire
charcoal was used. Another potentially important difference
is the different pH of laboratory charcoal and wildfire
charcoal (Table 1). The low pH associated with the lab
charcoals may have indirectly diminished P availability
in these treatments. Another difference between the
charcoal used in experiments 2 and 3 was the range
of charcoal particle size used. Experiment 3 incorporated
charcoal ranging from large (12cm)tomicroscopic
fractions. We noted substantial root penetration into large
charcoal particles at the end of this greenhouse experiment,
which suggests that some resource, such as water, is more
available inside large charcoal particles. It is also possible
that grinding charcoal to a smaller size class, in some way,
eliminates its beneficial effects on soil fertility. For
instance, grinding may enhance the availability of organic
carbon because it is very immobile, whereas N ions are
significantly more mobile; thus, nutrient immobilization
may be more substantial when charcoal is ground.
Conclusion
It is clear that charcoal has the potential to significantly alter
soil solution chemistry and growth of K. macrantha. Charcoal
did not appear to stimulate N cycling in a low-nutrient
setting, but when glycine was added to soil, charcoal greatly
enhanced N mineralization and nitrification. This result may
indicate that low temperature charcoal contributes bioavail-
able carbon that causes N immobilization under low nutrient
conditions. As hypothesized, charcoal effectively sorbed
soluble phenols from litter extracts. This sorption may
effectively reduce the inhibitory effect of litter extracts on
soil microorganisms, plants, and biogeochemical processes.
Low-temperature, laboratory-generated charcoal had a nega-
tive effect on growth of K. macrantha, possibly as a result of
Table 3 Plant mass and resin sorbed nutrients (mean±SE, n=10) from a greenhouse experiment where soil was amended with 0, 0.5, 1, 2, 5, and
10% charcoal collected from a wildfire
Percent charcoal
0% 0.5% 1% 2% 5% 10% p
Total mass (g) a0.5 (0.2) ab1.0 (0.3) ab1.1 (0.2) ab1.1 (0.2) b1.3 (0.1) b1.4 (0.1) <0.05
Root mass (g) 0.3 (0.2) 0.6 (0.2) 0.7 (0.1) 0.7 (0.1) 0.8 (0.1) 0.8 (0.1) >0.05
Aboveground mass (g) a0.2 (0.1) ab0.4 (0.1) ab0.4 (0.1) ab0.4 (0.1) b0.5 (0.1) b0.6 (0.1) <0.01
Root to shoot ratio 1.5 (0.2) 1.5 (0.3) 1.8 (0.2) 1.7 (0.3) 1.6 (0.2) 1.3 (0.1) >0.05
NHþ
4(μg resin capsule
1
)55.6 (4.0) 49.8 (4.6) 36.9 (6.0) 42.7 (2.2) 43.0 (1.3) 44.4 (2.9) <0.05
a
NO
3(μg resin capsule
1
)a1,539.8
(463.4)
b947.9
(128.4)
bc552.3
(116.3)
bc556.1
(93.4)
bc561.8
(278.7)
c248.6
(29.8)
<0.001
PO3
4(μg resin capsule
1
)a10.1 (1.4) a8.8 (2.1) ab5.8 (1.2) ab6.5 (1.7) bc1.7 (1.0) c0.0 (1.2) <0.001
Letters in bold indicate differences using the StudentNewmanKeuls post hoc procedure
All pvalues are for one-way ANOVA, unless otherwise noted
a
KruskalWallis test pvalue
Biol Fertil Soils (2007) 43:303311 309
a toxicity effect caused by some compound formed during
low temperature charring or by N immobilization, as
suggested by the no-glycine soil incubation. In contrast,
charcoal created during a wildfire had a positive effect on the
growth of K. macrantha, suggesting low-temperature, labo-
ratory charcoal may not adequately represent field-collected
charcoal. Field-collected charcoal may have been generated
in a higher oxygen, higher temperature environment and may
have been exposed to leaching by rainwater and occlusion by
soil organic compounds before collection. Further investiga-
tion is required to evaluate how charcoal formation conditions
alter its effect on soil processes and plant growth and how
these processes manifest themselves in natural ecosystems.
Acknowledgements We thank V. Kurth, D. Mackenzie, and T.
Burgoyne for their assistance in the laboratory and greenhouse. We
also acknowledge funding from the NSF (NSF-DEB-03171108) and
the USDA Joint Fire Sciences Program (FFS #107) for this research.
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... These findings provide valuable insights for optimizing P management strategies in paddy fields. [3] 。长久的耕种与施肥导致大量磷素累积在土壤中,且过量累积的磷极易随地表径流和淋溶 流失,进而导致水体污染等环境问题 [4] 。土壤遗存磷指数(P LGC )、磷吸附容量(P SOR )、磷饱和度(DPS) 通常被用来评估与预测土壤磷的流失潜能与风险。其中,P LGC 是土壤中以植物潜在利用形式累积的 磷,即当外界不再继续输入磷源时,土壤本身可以供作物利用的磷含量,即 P LGC 数值越高,土壤 自身的供磷能力越强 [5] ;P SOR 反映了土壤对磷的吸附磷吸附能力,P SOR 数值越高,土壤对磷吸附力 越强,可吸附的磷量越多 [6] ;DPS 是土壤可提取态磷占土壤最大吸附量磷的比值,可以表征土壤磷 的饱和状态 [7] ,DPS 值越高,表示土壤中磷饱和程度越高、土壤的释磷潜能越大、磷的吸附能力越 弱 [8] [9] 。 稻秆生物炭是稻秆在缺氧的环境下高温热解而成,具有碱性、高表面积、吸附性强等理化性质 [10] ,被作为一种土壤改良剂广泛应用于农业生产中 [11] ,对农作物高产稳产与生态环境都有着至关 重要的作用。农田中施用生物炭会影响土壤磷的形态及有效性:首先,生物炭可以直接向土壤输入 无机磷,生物质在热解为生物炭的过程中伴随着有机磷化学键的断裂和碳的升华,且 600℃下热解 制成的生物炭只有无机正磷酸盐一种形态的磷存在 [12] ;其次,生物炭通过影响土壤微生物数量和活 性进而影响磷酸酶的活性,促进有机磷矿化为无机磷的反应 [13] 。此外生物炭可以降低酸性土壤对磷 的吸附,提高磷的有效性 [14] 。但也有研究发现生物炭增加了酸性土壤对磷的吸附,降低磷的有效性 [15] 。在低磷土壤中,生物炭可以吸附一部分磷,以减少磷从土壤到地表水或者地下水的淋失 [16] 。 李发永等研究发现生物炭输入有增加土壤中磷素流失潜能的风险,生物炭与化肥联用可能增强化肥 磷素流失 [17] 。可见,秸秆生物炭对酸性稻田土壤磷素的有效性及流失风险的影响仍待进一步研究。 本文以江西鹰潭孙家小流域内酸性稻田土为研究对象,基于水稻盆栽实验对比分析了生物炭添 加一年与两年后,稻田土壤全磷、各形态磷组分及遗存磷指数(P LGC )、磷饱和度(DPS)和磷吸附容量 (P SOR )的变化规律与差异;估测生物炭添加后稻田土壤磷的流失潜能与风险,从而为生物炭的合理 施用及稻田磷素高效管理提供理论依据。 2.6 相关性分析 将稻田壤磷组分及 P SOR 、DPS、P LGC 与稻田的 pH、TP、Fe M3 和 Al M3 做相关性分析,土壤 P OCL 与 P HCl 和 Al M3 均呈显著负相关(P < 0.05),P HCl 与土壤 TP 呈极显著正相关(P < 0.01);P LGC 和 DPS 与 P SOL 、P M3 呈现极显著正相关,与 Po OH 呈现显著正相关。P SOR 与 pH 成极显著负相关,与 Fe M3 呈 现显著负相关(P < 0. 3 讨论 生物炭可以通过与土壤有机质和矿物组分的相互作用,改变磷的化学形态和土壤对磷的吸附和 解吸能力 [21] 。生物炭施用均显著增加了 P SOL 、P M3 、Po OH 、P HCl 含量及占比(图 2 ~ 4),即土壤中稳 定性较低且易被作物直接吸附利用的 P SOL 和 P M3 显著增加,但只有两年连施生物炭显著降低了稻田 土壤 P OCL 的占比(图 8)。这可能是因为生物炭中有由丰富的正磷酸盐和少量的浓缩磷酸盐组成的有 效磷,逐步释放进土壤中可增加土壤 P SOL 和 P M3 含量 [23] 。生物炭添加显著降低了成熟期稻田土壤 [19] 。此外生物炭表面的含氧官能团与土壤溶液中的 H + 中合后,促使 Al 3+ 发生了水解转变为 Al(OH) 3 沉淀,从而降低了溶液中交换性铝的含量 [24] 。Pi OH 和 Po OH 是土壤中通过化学吸附结合在铁铝氧化 物上的无机磷和有机磷,是中等活性磷,对植物有效性较低,占据了土壤总磷大部分 [25] 。研究发现 秸秆生物炭会显著提高土壤中有机磷含量,有效降低土壤有机磷活性,增强有机磷稳定性 [26] ...
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This study examined the influence of biochar application on soil phosphorus dynamics in a typical red paddy soil through a rice pot experiment. The experiment compared three treatments: no biochar application (CK), one-year biochar application (B1), and two-year consecutive biochar application (B2). The concentrations and proportions of total phosphorus (TP), active P (PSOL, PM3), moderately stable P (PiOH, PoOH, PHCl), and highly stable P (PCL, POCL) were analyzed at different rice growth stages. Additionally, the responses of soil legacy P index (PLGC), P saturation degree (DPS), and P adsorption capacity (PSOR) to biochar addition were investigated. The results revealed that compared to the CK treatment, B1 application significantly reduced active P during the tillering stage but increased it during the maturity stage. Moderately stable P increased significantly during the tillering stage in the B1 treatment. No significant changes were observed in highly stable P for all treatments(P < 0.05). In the B2 treatment, active P significantly increased during the heading and maturity stages, while moderately stable P increased during the tillering and maturity stages. The content of highly stable P remained unchanged, but its proportion decreased significantly by 18.8% and 27.8% during the heading and maturity stages, respectively. Both B1 and B2 treatments led to a significant increase in PLGC and DPS, and the B1 treatment showed a significant increase in PSOR during the heading stage. Overall, the addition of biochar significantly increased the content and proportion of active P and moderately stable P in paddy soil, decreased the proportion of highly stable P with low plant utilization, and enhanced soil legacy P and bioavailable P. These findings provide valuable insights for optimizing P management strategies in paddy fields.
... Soil microbes play a crucial role in natural biochemical processes, enhancing soil fertility through the microcirculation of nutrients within the soil ecosystem (Zou et al., 2018). Recent studies have investigated the influence of biochar addition on soil health, with a primary focus on its effects on the physical (Wang et al., 2016b), chemical (Wang et al., 2016a;Zhang et al., 2018a,b), and microbial interactions (Ahmad et al., 2014;Cheng et al., 2019;Gundale and DeLuca, 2007;Ding et al., 2019). ...
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The chapter explores the interrelationship between biochar and soil microorganisms, focusing on the role of biochar as a growth promoter and its effects on soil contaminants. Biochar and microorganism interactions are intricate and multifaceted. Biochar–microbe interactions, the dissipation and transformation of contaminants, and the immobilization of contaminants are discussed. Various interactions between biochar and soil microorganisms are also investigated. Overall, this review highlights the potential of biochar to promote soil microbial activity and mitigate the impacts of contaminants, while emphasizing the need for further research in this field.
... The ability of biochar to increase extractable P (PO 4 ) levels in the soil solution, either directly through its anion exchange capacity or by affecting the availability of the cations (Fe 2+ , Al 3+ , and Ca 2+ ), has increased the quantity of soil P that is readily available. The fact that with P, soil P availability has increased is another factor [55]. This is made feasible by an elevation in soil pH caused by biochar, which bonds these metal cations together to prevent P from interacting with them and inhibits P from precipitating in solution by forming actinide. ...
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Few studies have examined how fertilizers aff ect soil chemical properties, cabbage (Brassica oleracea L.) yield, and nutrient uptake in Ghana. This study examined how corn cob biochar (CCB) and NPK (15:15:15) fertilizer aff ected cabbage growth, yield, soil chemical properties, and nutrient uptake. The study was conducted during the 2021 major season at Soil Research Institute, Kwadaso. A 3×3 factorial experiment set out in a Randomized Complete Block Design with three replications was conducted. The treatments applied were control (No fertilizer), 50% NPK, 100% NPK, 2,500 kg ha-1 CCB, 50% NPK + 2,500 kg ha-1 CCB, 100% NPK + 2,500 kg ha-1 CCB, 5,000 kg ha-1 CCB, 50% NPK + 5,000 kg ha-1 CCB and 100% NPK + 5,000 kg ha-1 CCB. Application of 100% NPK resulted in the largest (2.99 cm) stem diameter. Application of 100% NPK + 5,000 kg ha-1 CCB resulted in the tallest plants (42.3 cm) and cabbage leaf spread (71.23 cm). Application of 100% NPK + 5,000 kg ha-1 CCB resulted in the largest cabbage head circumference (67.43 cm). The 100% NPK + 2,500 kg ha-1 CCB gave the highest yield (40679 kg ha-1). 100% NPK + 2,500 kg ha-1 CCB increased nitrogen uptake, 50% NPK + 5,000 kg ha-1 increased phosphorus and calcium uptake, 100% NPK + 5,000 kg increased potassium uptake, and 50% NPK + 2,500 kg increased magnesium uptake. Therefore, it is suggested that CCB and NPK fertilizers be applied to enhance the soil’s physical and chemical properties, nutrient uptake, and other factors contributing to cabbage growth and yield.
... Biochar contains high amounts of carbon, nitrogen, phosphorus, magnesium, potassium, and calcium . The impact of biochar application on plants and soils is influenced by the type of crops grown, farming systems, plant species, climate (Gundale and DeLuca, 2006;Unger 54(2): 287-292 (2024Unger 54(2): 287-292 ( ) et al., 2011 and fertilization (Haefele et al., 2011). The large surface area of biochar provides a suitable habitat for soil microorganisms (Lehmann et al., 2011). ...
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Phosphorus (P) is one of the most important elements required for the physiological and biochemical functions of plants. It is well known that there are many limitations to the uptake of phosphorus from soil. In this study, the interaction between different doses of chemical P fertilizer and biochar application on wheat plants was investigated. In this greenhouse experiment, P fertility was studied in calcareous soil with a high pH in southern Turkey. Wheat plants were grown for seven weeks with 3 biochar doses (0-20-40 tonnes ha-1) and 4 P fertilizer applications (0, 50, 100, and 200 kg P2O5 ha-1). Dry weight (DW), macro (nitrogen (N), P, potassium (K), magnesium (Mg)), and micronutrient (iron (Fe), zinc (Zn), copper (Cu), and manganese (Mn)) concentrations were evaluated in post-harvest plant samples. The efficiency of P utilization (agronomic, physiological, and apparent recovery) was also determined. The dry matter yield increased significantly with increasing biochar dose and P application. The highest agronomic efficiency and apparent recovery efficiency of wheat plants were found to be 13.16 mg-1 and 12.52 % when BOP50 was applied. Increases in N, K, Zn, and Mn concentrations in wheat plants were determined depending on biochar and P dose applications.
... The ability of biochar to increase extractable P (PO 4 ) levels in the soil solution, either directly through its anion exchange capacity or by affecting the availability of the cations (Fe 2+ , Al 3+ , and Ca 2+ ), has increased the quantity of soil P that is readily available. The fact that with P, soil P availability has increased is another factor [55]. This is made feasible by an elevation in soil pH caused by biochar, which bonds these metal cations together to prevent P from interacting with them and inhibits P from precipitating in solution by forming actinide. ...
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