The potential role of biochar in adapting soils to climate change in Portugal

Abstract

The work presented, was to review the scientific literature for evidence of how biochar can be used to adapt soils to the challenges posed by climate change, specifically for three important land uses in Portugal, i.e. forest plantations, permanent crops, and grasslands.

Full text

Environment and Planning Department (DAO)
Environmental Science and Engineering Doctoral Program
Academic Year 2019-2020
The Potential Role of Biochar in Adapting Soils to Climate Change
in Portugal
Climate Change; Science, Adaption, and Mitigation course
Author: Behrouz Gholamahmadi, PhD student on Environmental Science and Engineering.
Supervisor: Dr. Frank G. A. Verheijen.
INTRODUCTION
Biochar is the carbon-rich product of the thermal conversion of biomass in absence of or with limited
air under high-temperature, a process called charring or pyrolysis also used for making charcoal
(Lehmann and Joseph, 2012). (Figure 1) Charcoal is from woody biomass and thermally converted
under less controlled pyrolysis conditions (often in a pile or a pit in the ground) than biochar, which
can be from any sustainably sourced biomass and under more controlled pyrolysis conditions
because it has to meet the quality criteria of the certification. For example, IBI (International Biochar
Initiative) Biochar Certification Program (IBI, 2015), and European Biochar Certificate (EBC, 2012)
are biochar certification programs and standards which they have common aims for providing an
indicator of quality and safety of biochar for use as a soil amendment, also through the necessary
quality assurances for both users and producers; and providing state-of- the-art information as a
sound basis for future legislative or regulatory approaches (Verheijen et al., 2015). It can be used to
improve agriculture and the environment in several ways, and its persistence in soil and nutrient
retention properties make it a potential soil amendment. Biochar sequestration in combination with
sustainable biomass production, can be carbon-negative and therefore used to actively remove
carbon dioxide from the atmosphere, with potentially major implications for mitigation of climate
change (Lehmann and Joseph, 2012). Studies show that biochar the potential mitigate to methane
emissions from soil, particularly from flooded (i.e. paddy) fields (Hedge’s d=-0.87) and/or acidic soils
(Hedge’s d=-1.56) (Jeffery et al., 2016). Also, the overall N2O emission reduction was 38%, and NO3¯
leaching was reduced by 13% (Borchard et al., 2019). In the (Liu et al., 2019) meta-analysis study

showed 29% reductions in yield-scaled greenhouse gas emission intensity by biochar varied with
different experimental condition and properties of soil and biochar. Across all studies, biochar
amendment had no significant effect on soil CO2 fluxes, but it significantly enhanced soil organic
carbon content by 40% and microbial biomass carbon content by 18% (Liu et al., 2016). For biochar
to be considered a sustainable policy option, it is essential to extend R&D to comprehensively cover
all soil functions (European Commission, 2006) and threats to soil, which include soil erosion, decline
in soil organic matter, soil compaction, soil sealing, decline in soil biodiversity, soil salinization, soil
contamination, and landslides (European Commission, 2006), and at several spatiotemporal scales
(Verheijen, Montanarella and Bastos, 2012). Also, the need for credible and reliable
measurement/monitoring, reporting and verification (MRV) platforms, both for national reporting
and for emissions trading (Smith et al., 2019). In the EU, Portugal has the lowest average Soil Organic
Carbon (SOC) content, i.e. 2.8%. (LUCAS model; (Aksoy, Yigini and Montanarella, 2016)). Biochar as
a boaster, plays important role to retention of soil organic matter (SOM) and by consequence in soil
organic carbon (SOC) that is suited to withstand the impact of climate change because could make
more resistance to erosion and retain water a lot better, especially during extreme events such as
droughts in Portugal.
Rising global temperatures are expected ranging from 2 to 5⁰C by 2100 (IPCC, 2013). Climate impacts
have led to poorer harvests and higher production costs, affecting price, quantity and the quality of
farmed products in parts of Europe. While climate change is projected to improve conditions for
growing crops in parts of northern Europe, the opposite is true for crop productivity in southern
Europe including Portugal. According to projections using a high-end emission scenario, yields of
non- irrigated crops like wheat, corn and sugar beet are projected to decrease in southern Europe
by up to 50 % by 2050 (EEA, 2019). The recent climatic trends over Portugal are already in line with
these climate projections (Fraga et al., 2016). For instance, viticulture is an important socioeconomic
sector in Portugal that strongly depends on specific soil conditions (e.g. soil moisture and
temperature, pH, salinity, and bulk density). Changes in critical factors like annual precipitation
amount and seasonal distribution, can lead to a wide range of effect (i.e. small shoot growth, poor
flower cluster, berry set enlargement) on the stage of grapevine development (Fraga et al., 2012).
Change on climate variables like temperature and precipitation are very important for forest soils.
Increasing frequency and intensity of summer heatwaves and lack of rainfall may exacerbate these
effects (Maracchi, Sirotenko and Bindi, 2005) and this warming may have a profound and immediate
impact on wildland fire activity. For instance, increasing of fire season severity and length (Flannigan
et al., 2013).
Soil organic matter (SOM) is a key component for soil structure maintenance and sustaining
production in grassland ecosystem (Conant, Paustian and Elliott, 2001). Biochar application has
potential to increase forage production may potentially increase SOM, thus sequestering
atmospheric carbon (C). Also, to be nitrogen (N) input, and a mitigation agent for environmentally
detrimental N losses (Clough et al., 2013).

Figure 1 – Concept of pyrolysis process with biochar sequestration. Typically, about 50% of the pyrolyzed biomass is
converted into biochar and can be returned to soil (Lehmann, 2007).
The aim of the work presented here was to review the scientific literature for evidence of how
biochar can be used to adapt soils to the challenges posed by climate change, specifically for three
important land uses in Portugal, i.e. forest plantations, permanent crops, and grasslands.
METHODS AND MATERIALS
The databases SCOPUS and Web of Science were searched, for the key terms: “Biochar AND soil
AND climate change”; “Biochar AND soil erosion”; and “Biochar AND infiltration”, for period
between “2000-2019”. Finding from SCOPUS portal returned 398 documents between “2007-2019”.
Most were research articles (270), review papers (62), Book chapters (27), and the rest were
Conference papers (19), Book (8), Note (5), Letter (3), Conference review (2), Editorial (1), and Short
survey (1). Figure 2 shows the temporal and “by country”, and Figure 3 shows “by year” distributions
of SCOPUS search results. Of these papers, 223 are with quantitative data from field/lab
experiments (Limited to “experiment” key word search bar).

Figure 2 – Frequency distributions of documents count from SCOPUS (by country)
Figure 3 – Frequency distributions of documents from SCOPUS (by year)

For the search key of “Biochar and infiltration” (TS= (Biochar and infiltration)) the WoS portal yielded
86 documents between “2010-2019”. Finding were research articles (78), review papers (2),
Proceeding papers (4), Early access (2). Figure 4 shows the temporal and “by country”, and Figure 5
shows “by year” distributions. Of these papers, 28 are with quantitative data from field/lab
experiments (Limited to “experiment” key word search bar).
Figure 4 – Frequency distributions of documents from WoS (by year)
Figure 5 – Frequency distributions of documents from WoS (by country)

For the search key of “Biochar and soil erosion” (TS= (Biochar and soil erosion)) the WoS portal
yielded 110 documents between “2010-2019”. Finding were research articles (94), review papers
(12), Proceeding papers (8), Early access (5). Figure 6 shows the temporal and “by country”, and
Figure 7 shows “by year” distributions. Of these papers, 40 are with quantitative data from field/lab
experiments (Limited to “experiment” key word search bar).
Figure 6 – Frequency distributions of documents from WoS (by year)
Figure 7 – Frequency distributions of documents from WoS (by country)

RESULTS AND DISCUSSIONS
Impacts of climate change on soil may differ for three mainland uses in Portugal, i.e. forest
(plantation); permanent crops (e.g. vineyard, olive/orange orchards); and grasslands, by varying
effects on soil physical properties, soil moisture, infiltration index, organic matter dynamics, and C
sequestration in soil. Among the soil physical properties investigated in the recent meta-analysis of
(Razzaghi, Obour and Arthur, 2019), biochar, in general, reduced soil bulk density and increased
plant available water. Changes in soil water content retained at field capacity and wilting point
showed an increase in the coarse- and medium-textured soils but decreased for the fine-textured
soils suggesting that the impact of biochar on soil water content may be soil type-dependent.
(Tisserant and Cherubini, 2019) in another review by a meta-analysis, found that biochar in soils
presents relatively low risks in terms of negative environmental impacts and can improve soil quality
and that decisions regarding feedstock mix and pyrolysis conditions can be optimized to maximize
climate benefits and to reduce trade-offs under different soil conditions. Biochar systems also
interact with the climate through many complex mechanisms (i.e., surface albedo, black carbon
emissions from soils, etc.) or with water bodies through leaching of nutrients. Figure 8 summarizes
how biochar interacts with the climate system once incorporated in the field (not all mechanisms
may happen in all cases, and some mechanisms can result in either cooling or warming depending
on local conditions).
Figure 8 – Biochar’s effects on climate under cultivated field (left) or fallow (right) conditions. Signs in parenthesis indicate
biochar’s effect on the variable compared to control without biochar: (+) increased, (−) decreased, (=) unchanged, (?) there
is limited data available for assessment. Here are the different mechanisms of how biochar in soil may affect the climate

system. Soil Organic Carbon (SOC): Biochar has a positive direct effect on SOC by providing recalcitrant carbon and an
indirect positive effect on SOC by stabilization of soil carbon. Some biochar carbon may be leached from soils or
transported by wind. (Soil Inorganic Carbon (SIC): Biochar’s effect on SIC is still limited in scientific evidence, but a
preliminary study shows that biochar increases SIC stock both directly and indirectly. Albedo: Biochar tends to make soils
darker and, hence, to reduce surface albedo. However, the presence of a vegetation canopy or snow cover can dampen
these effects. Soil emissions: Changes in soil emissions depend on the gas (i.e., N2O, CH4, NOx, and NH3), biochar
properties, and soil conditions. Water retention: Biochar increases soil water retention and plant available water, making
more water available for evapotranspiration under cultivation and evaporation under fallow. Evapotranspiration: Under
cultivation, biochar has a contrasting effect on evapotranspiration depending on soil condition and climate (e.g.,
precipitation level and energy limitation for evapotranspiration) and can increase or decrease plant water use efficiency.
Under fallow, biochar tends to reduce evaporation; however, more evidence is needed. Net Primary Productivity (NPP):
Biochar has mixed effects on NPP depending on soil conditions; increased NPP fixes more carbon in vegetation, increasing
residues left on field and root and increasing root exudates, which may participate in increasing SOC. Black Carbon: During
application of biochar, tilling operation microparticles of black carbon can be transported by wind. Soil temperature: In
the absence of crop canopy, soil temperature increases and daily soil temperature fluctuations, which can affect sensible
heat flux, water evaporation, and SOC degradation rate. Under cultivation, biochar tends to decrease soil temperature
fluctuations (Tisserant and Cherubini, 2019).
In recent meta-analysis studies explored, biochar’s effect on soil water retention and plant water
availability may represent an interesting adaptation to climate change. Most of these biochar–soil-
climate interactions are discussed in detail in the following sections.
1- Decreasing of soil moisture and negative consequences for plant species in the forest
Forest soils act as moisture reservoirs and regulators in the forest water cycle. Numerous studies
have shown that soil water stress affects the growth of natural and planted forests and increases
tree mortality (Brzostek et al., 2014; Fargeon et al., 2016). Recent studies have demonstrated that
the application of biochar can significantly increase soil water holding capacity and thus moisture
contents in forest ecosystems. For example, (Prober et al., 2014) reported that the soil moisture
content in mesic woodlands increased by 6 to 25% after the application of green waste biochar at a
rate of 20 t ha ̄¹. Similarly, (LIN et al., 2017) reported that the overall average runoff decreased by
28% after the application of rice straw biochar at a rate of 20 t ha ̄¹ over a period of 2 years,
compared to a control treatment. The reduction in runoff was attributed, inter alia, to the strong
water retention effect of biochar. In addition, the response of soil hydrological properties to biochar
applications is biochar-specific (Lewis, Wu and Robichaud, 2006; Mukherjee and Lal, 2013). For
example, (Uzoma, 2011) investigated the effects of biochar application at various rates (0, 10, and
20 t ha 1) and biochar pyrolysis temperatures (300, 400, and 500 °C) on the hydraulic properties of
sandy soils. The experiments indicated that biochar application increased the saturated water
content from 0.2 to 56.1%. The application of biochar significantly increased the available water
capacity of all treated sandy soils compared to the control except for the treatment with biochar
prepared with a pyrolysis temperature of 300 °C and an application rate of 10 t ha 1. In addition to
biochar specificity, the response of soil hydrological properties to biochar amendments is soil-
specific (Lewis, Wu and Robichaud, 2006).For example, biochar treatment significantly increased
the water holding capacity of sandy soils, but no such effect was observed for silt loams despite
equivalent water potentials (D. Tian, 2015).
According to the results obtained by (Kinney et al., 2012), water repellency increased significantly
when higher rates, that is, above 5% of biochar were applied. On the other hand, (Briggs, Breiner

and Graham, 2012) observed an extremely hydrophobic characteristic (water drop penetration time
>2 h) for a Pinus ponderosa biochar. However, they observed that older carbon under forest floor
layers was less water repellent. (Baronti et al., 2014) did not confirm a significant increase in soil
hydrophobicity in the field trial with biochar produced from orchard wastes. Also (Abel et al., 2013)
concluded that biochar produced from maize feedstock and pyrolyzed at 750 °C had no effect on
soil water repellency. (Kinney et al., 2012) found that biochars from three different feedstocks
followed the same trend: pyrolysis at 300 °C produced very hydrophobic biochar, but hydrophobicity
decreased with an increase in the temperature. The explanation for that phenomenon was
proposed by (Hallin et al., 2015).They found that biochar produced at lower temperatures b500 °C
retained organic functional groups from the feedstock, and therefore it is usually water repellent.
However, pyrolysis at temperature above 500 °C volatilized the organic groups linked to
hydrophobicity, making the biochar more hydrophilic. (Novak et al., 2012) also suggested that
reduced biochar repellency in higher temperature were due to changes in the proportions of
hydrophobic and hydrophilic functional groups. It is thought that the hydraulic properties of biochar
depend largely on the biomass feedstock used and pyrolysis conditions. Moreover, it is also stated
that hydrophobicity of biochar changes over the time. (Briggs, Breiner and Graham, 2012) observed
high water repellency for a freshly produced wooden biochar, but older carbon under forest
condition was less water repellent. To explain the mechanism of soil water repellency after biochar
amendment, (Verheijen et al., 2010) proposed an analogy between the impact of biochar addition
and the result of wildfire when water repellency was observed in forest soils. According to (Doerr
and Thomas, 2000), this mechanism is ascribed to the reorientation of amphiphilic molecules by
heat from a fire. This does not affect the soil but could affect the biochar during pyrolysis process.
Yet this hypothesis of the mechanism of the soil hydrophobicity after biochar application is still not
fully understood. To sum up, the water holding capacity of forest soils plays an important role for
forestry production, especially in arid and semi-arid areas. Study from (Nunes et al., 2019) shows a
comparative analysis of the data provided by IPMA (Portuguese Institute of the Sea and the
Atmosphere), was carried out for the period from 2001 to 2017 with the climatic normal for the
period between 1971 to 2000, for the variables of the average air temperature, and for the
precipitation. In this comparative study, the average monthly values were considered and the
months in which anomalies occurred were determined. Anomalies were considered in the months
in which the average air temperature varied by 1 °C than the value corresponding to the climatic
norm, in at least 50% of the national territory. The same procedure was repeated for the variable
precipitation, counting as anomaly the occurrence of a variation in precipitation of 50%, also in 50%
of the national territory. It is critical to further study the effects of different biochar types on the
water holding capacity and plant available soil water contents and soil water repellency of different
soil types and under different forest ecosystems, as well as the associated mechanisms (Li et al.,
2018).
2- Retain crop productivity and quality in droughts and different climate condition
(viticulture)
In recent decades global climate changes has been a major cause of concern for winegrowers
because of the rise in mean annual air temperature and of the increase of frequency and intensity
of extreme weather events such as droughts and heatwaves. Those changes are projected to

increase in the forthcoming decades causing a shift in the viticulture suitability of many productive
regions (Hannah et al., 2013).
(Baronti et al., 2014), applied a large volume (22 and 44 ton ha ̄¹) of biochar for two consecutive
seasons to a non-irrigated vineyard in Tuscany (central Italy), and reported an increase in soil water
content, a reduction of plant water stress and an increase of photosynthetic activity during drought.
This suggests that the application of biochar to vineyards is a feasible adaptation strategy to reduce
the impact of severe water stress periods without recurring to irrigation. (Genesio et al., 2015)
assessed the impact of biochar on grape yield and grape quality parameters in four harvests, based
on the same field experiment described in (Baronti et al., 2014). They found increased productivity
from four harvest-years, following biochar application, ranged from 16% to 66%, of treated plots
with respect to their controls, while no significant differences were observed in grape quality
parameters. The observed increase in productivity was inversely correlated with rainfall in the
vegetative period, confirming the key role of biochar in regulating plant water availability. These
findings support the feasibility of a biochar-based strategy as an effective adaptation measure to
reduce the impact of water stress periods with no negative effects on grape quality.
3- Biochar, soil and land-use interactions: nitrate leaching and N2O emissions
(Borchard et al., 2019) in their results revealed that biochar applications to Histosols reduced N2O
emissions by −47%. This N2O emissions reduction may be improved by biochar through i) alteration
in soil moisture regime during non-flooded periods (Clough et al., 2013; Ajayi and Horn, 2016;
Petersen et al., 2016) , ii) a reduction of redox potentials to levels that promote formation of NH4+,
or iii) complete denitrification to N2 (Cayuela et al., 2013; Harter et al., 2014; Sumaraj and Padhye,
2017). Meta-analysis revealed that biochar stimulates an overall N2O emissions reduction of 38%
with greater reductions immediately after application. The time dependent impact of biochar
application on soil N2O emissions is a crucial factor requiring consideration in order to develop and
test resilient and sustainable biochar-based greenhouse gas mitigation strategies. In terms of land
use, biochar can reduce rice paddy soil N2O emissions (i.e. Anthrosols) by almost 40%; this may
significantly mitigate climate change, as ~140 Mha are used as paddy fields globally (Kögel-Knabner
et al., 2010) ,and since methane emissions from paddy soils have been found to be reduced as well
(Jeffery et al., 2016). Adding biochar to sandy or coarse textured soils (e.g. Arenosols) reduced both
N2O emissions and NO3− leaching, which reduces soil N losses and presumably improves both N
use efficiency and mitigates climate change. Considering land use (e.g., paddy soils, grasslands,
annual or perennial cropping systems, etc.) in conjunction with soil properties (e.g. texture, soil
organic matter, pH) may provide reliable information suitable for up-scaling N2O emission reduction
estimations and potentials, and ultimately the best practical scenarios for environmental biochar
use. Results support the notion of a dose-response relationship of biochar application on N2O
emission reduction and also NO3− leaching, which hints towards the interesting possibility of using
biochar as a carrier matrix for “carbon-fertilizers” as successfully explored by (Qian et al., 2014).
Using biochar in this way would greatly reduce the required dose of N per hectare, which would
improve N use efficiency and reduce the economic barriers for biochar use in agronomy. However,
the eco-physiological mechanisms controlling N uptake by plants in soil-biochar-plant systems
require further analyses to ensure sustainable N-management (Borchard et al., 2019).

4- Soil albedo and potential impact on the global radiation balance
(Verheijen et al., 2013) with a laboratory experiment showed a strong tendency for soil surface
albedo to decrease as a power decay function with increasing biochar application rate, depending
on soil moisture content, biochar application method and land use. Surface application of biochar
resulted in strong reductions in soil surface albedo even at relatively low application rates. As a first
assessment of the implications for climate change mitigation of these biochar–albedo relationships,
they applied a first order global energy balance model to compare negative radiative forcing (from
avoided CO2 emissions) with positive radiative forcing (from reduced soil surface albedos). For a
global-scale biochar application equivalent to 120 t ha ̄¹, they obtained reductions in negative
radiative forcing of 5 and 11% for croplands and 11 and 23% for grasslands, when incorporating
biochar into the topsoil or applying it to the soil surface, respectively. For a lower global biochar
application rate (equivalent to 10 t ha ̄¹), these reductions amounted to 13 and 44% for croplands
and 28 and 94% for grasslands. Also, (Genesio et al., 2012) worked to characterizing the annual
albedo cycle for a durum wheat crop in Central Italy, by means of a spectroradiometer measurement
campaign. Plots treated with biochar, at a rate of 30–60 t ha ̄¹, showed a surface albedo decrease of
up to 80% (after the application) with respect to the control in bare soil conditions, while this
difference tended to decrease during the crop growing season, because of the prevailing effect of
canopy development on the radiometer response. After the post-harvesting tillage, the soil treated
with biochar again showed a lower surface albedo value (<20–26% than the control), while the
measurements taken in the second year after application suggested a clear decrease of biochar
influence on soil color. Although, decreases in soil surface albedo lead to more absorbance of solar
energy, but it is not clear yet what the impacts of that will be on topsoil temperatures because of
confounding effects of increased soil moisture contents, i.e. a wetted soil warms up less deep than
a drier soil because of the large specific heat of water. Nevertheless, bare soil evaporation should
increase with lower soil surface albedo, all else being equal (e.g. solar radiation, vegetated soil
cover). However, biochar might lead to concomitant increases in vegetated soil cover, which would
reduce bare soil evaporation.
5- Interaction between hydroclimatic change and soil erosion
Simultaneous changes in global and regional hydroclimates, related to global warming and shifts in
the nature of the hydrologic cycle, may result in increased frequency and erosivity of rainfall events
(Hatfield, Cruse and Tomer, 2013). Also, rainfall erosivity is, in general terms, the ability or power of
rain to cause soil loss. The result of the studies on climate change and erosion show that the
anticipated effects of climate change on both runoff and erosion are significant and important. The
interactions involved are complex because of many interactions between the processes involved
(Nearing, 2004). Infiltration is an important process in the hydrologic cycle; it determines water
intake by the soil profile and the amount lost as runoff. (Abrol et al., 2016) reported on the results
of biochar application in the soil in a rainfall simulation experiment. The hypothesis was that adding
biochar could moderate the reductions in infiltration rates (IR) that occur during high-intensity
rainstorms in seal-prone soils, and hence result in reduced runoff and erosion rates. In the non-
calcareous loamy sand, 2% biochar was found to significantly increase final infiltration rate by 1.7
times, and significantly reduce soil loss by 3.6 times, compared with the 0 % biochar control. In
another research by (Jien and Wang, 2013) on highly weathered soils in humid Asia that they are
characterized by low soil fertility and high soil erosion potential. The study used three application

rates (0%, 2.5%, and 5%; w/w) of the biochar with an incubation time of 105 d for all cases. Soils
were collected at 21 d, 42 d, 63 d, 84 d, and 105 d during the incubation period to evaluate changes
in soil properties over time. Experimental results indicate that applying biochar improved the
physicochemical and biological properties of the highly weathered soils, including significant
increases in soil pH from 3.9 to 5.1. Incorporating biochar into the soil significantly reduced soil loss
by 50% and 64% at 2.5% and 5% application rates, respectively, compared with the control. Being a
key indicator of soil quality, soil aggregate stability represented generally by a mean weight
diameter (MWD) could influence water infiltration and thus soil erosion. Biochar addition helped to
improve soil structure by increasing aggregate stability through promotion of macro aggregate
formation (Herath, Camps-Arbestain and Hedley, 2013; Ouyang et al., 2013).
Conclusion
Biochar has attracted attention as a soil amendment capable of improving yield and soil quality and
of reducing soil greenhouse (GHG) emission. In this report, we reviewed and discussed how biochar
could be a mitigation tool and option for adapting soils to climate change, considering of Portugal
current and future climatic condition. Scientific evidences of climate change’s Impacts on soil under
forest (plantation), permanent crops (e.g. vineyards), and other land-uses (e.g. grasslands, perennial
crops) and also soil-biochar-climate interactions, explored. Based on the evidence of the literature
reviewed for the likely impacts of climate change on soil, we conclude that biochar application to
soil has great potential for permanent crops, moderate potential for forest, and limited potential
for grasslands.
Recommendations for future research
To date, scientific evidence of biochar application experience on vineyard soils in order to adapting
with climate change, has been limited in Portugal. Due to a strong socio-economic dependence of
vineyards in Portugal and great potential of using biochar on this land-use, there needs more
research for biochar effects on vineyard soil properties and structure. specifically, biochar effects
on runoff and soil erosion in long-term, large-scale and different experimental conditions.
Acknowledgments: The Author thanks Dr. Frank G. A. Verheijen for guideline and useful comments.
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