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The forested area in the tropics continues to decrease. It is a challenge to preserve large areas of tropical forest to counteract the accelerating climate change and loss of biodiversity. The cumulative deforested area (including old clearings and hydroelectric dams) in Amazonia up until 1991 reached 427,000 km2 or 11 % of the 4 million km2 original forested portion of Brazil’s 5 million km2 legal Amazon region (Fearnside 1997).
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14 Slash and Char: An Alternative to Slash
and Burn Practiced in the Amazon Basin
ChristophSteiner
1
1Institute of Soil Science and Soil Geography, University of Bayreuth, 95440 Bayreuth, Germany
,2,WenceslauGeraldes Teixeira2
2Embrapa Amazˆonia Ocidental, CP 319, 69011-970 Manaus, Brasil
and Wolfgang Zech1
14.1
Introduction
The forested area in the tropics continues to decrease. It is a challenge to pre-
serve large areas of tropical forest to counteract the accelerating climate
change and loss of biodiversity. The cumulative deforested area (including
old clearings and hydroelectric dams) in Amazonia up until 1991 reached
427,000 km2or 11 % of the 4 million km2original forested portion of Brazil’s
5millionkm
2legal Amazon region (Fearnside 1997).
Large-scale cattle ranching is mainly responsible for this decline in forest
area. However, new settlers advancing along the roads also contribute to
deforestation through slash and burn agriculture. In 1990 and 1991, 31% of
the clearing was attributable to small farmers (Fearnside 2001).
Slash and burn is an agricultural technique widely practiced in the tropics
and is consideredtobesustainable when fallow periods of up to 20 years fol-
low 1–3 years of agricultural activity. In many parts of the world, the increas-
ing population size and socio-economic changes including pioneer settle-
ment made slash and burn agriculture unsustainable, leading to soil degrada-
tion. In Rondˆonia, a state in the southwestern corner of the Brazilian Amazon
region, intense migration resulted in anincreaseinthehumanpopulationat
arateof15%peryearbetween 1970 and 1980 – a doubling time of less than
5years.Thepopulation of the northern Amazon region increased by 5% per
year over the same period (Fearnside 1983). The soil nutrient availability
already decreases after one or two cropping seasons. Subsequently, field crops
have to be fertilized for optimum production, or fields have to be abandoned
and new forests have to be slashed and burned, the common practice.
Soil nutrient and soil organic matter (SOM) contents are generally low in
the highly weathered and acid upland soils of central Amazonia, and soil deg-
radation is mainly caused by a loss of SOM as CO2into the atmosphere and
of nutrients into the subsoil. This processiswellknownandexplainssome
aspects of the low fertility levels of many soils in the tropics under permanent
cropping systems (Zech et al. 1990). In strongly weathered soils of the tropics,
SOM plays a major role in soil productivity because it represents the domi-
nant reservoir of plant nutrients suchasnitrogen(N),phosphorus(P),and
sulfur (S). Generally, SOM contains 95 % or more of the N and S, and between
20 and 75% of the P in surface soils (Zech et al. 1997). SOM also influences
pH, cation exchange capacity (CEC), anion exchange capacity (AEC), and soil
structure. SOM mineralization decreases the total retention capacity of avail-
able cations in tropical soils, where SOMisoftenthemajorsourceofnegative
charge. MaintaininghighlevelsofSOMin tropical soils would be a further
step towards sustainability and fertility on tropical agricultural land, thus
reducing the pressureonpristine areas.
14.2
Carbon Emissions in Slash and Burn Agriculture
Tropic a l fore sts account for between 20 and 25% of the world terrestrial car-
bon reservoir (Bernoux et al. 2001). Fearnside (1997) calculated net commit-
ted emissions of forest burnings in Amazonia. This is calculated as the differ-
ence between the carbon stocks in the forest and in the equilibrium replace-
ment landscape. He estimated the above-ground biomass of unlogged forests
at 434 Mg ha–1,abouthalfofwhich is carbon. In most agricultural systems the
tendency has been for population pressure to increase, leading to increased
use intensity over time and shorter fallow periods, with resulting lower aver-
agebiomass for the landscape. The net committed emissions for 1990 land-
use changeinBrazilianLegalAmazoniawere5%ofthetotalglobalemissions
from deforestation and fossil fuel sources (Fearnside 1997). Although most
emissions are caused by medium and large ranchers, the emissions of the
small farmer population in the Amazon Basin were estimated to be between
34 and 88 million Mg CO2-equivalent carbon in 1990 (Fearnside 2001).
Charcoal formation during biomass burning is considered the only way
that carbon is transferred to long-term pools (Zech et al. 1990; Glaser et al.
1998, 2001, 2002; Fearnside et al. 2001) and can have important effects on
atmospheric composition over geological time scales. At a burn of a forest
being converted to cattle pasture near Manaus, charcoal represented just
1.7% of the pre-burn biomass. The meancarboncontentofcharcoal manu-
factured from primary forest wood in the Manaus region is assumed to be
75% (Fearnside et al. 2001). Soils under tropical forest contain approximately
the sameamountofcarbonasthe abundant vegetation above it, being about
3% in the surface horizon and about 0.5 %inthesubsurfacehorizonsdown
to 100 cm depth (Sombroek et al. 2000). The soils of Brazilian Amazonia may
contain up to 136 Tg of carbon to a depth of 8 m, of which 47 Tg is in the top
1m. The current rapid conversion of Amazonian forest toagricultural land
makes disturbance of this carbon stock potentially important to the global
carbon balance and net greenhouse gas emissions. Soil emissions from Ama-
zonian deforestation represent a quantity of carbon approximately 20% as
large as Brazil’s annual emission fromfossil fuels (Fearnside and Barbosa
1998).
184 C. Steiner · W. G. Teixeira · W. Zech
14.3
Black Carbon in Soil –
Terra Pre ta do ´
Indio
Little attention has hitherto been given to black carbon as an additional
source of humic materials. Black carbon is produced by incomplete combus-
tion of biomass, creating various forms such as charcoal, charred plant resi-
dues, and soot.
The soils in Brazilian Amazonia are predominantly Oxisols and Ultisols,
but in addition a patchily distributed black soil occurs in small areas rarely
exceeding 2 ha. This is the so-called Te r r a p re t a d o ´
Indio.Becauseofthe simi-
larity in texture to that of immediately surrounding soils (from more or less
sandy to veryclayey),andbecauseoftheoccurrenceofpre-Columbian
ceramics and charcoal in the upper horizons, these soils are considered to be
anthropogenic (Sombroek 1966; Glaseretal.2001). According to Sombroek
(1966), terra preta is very fertile, and after clearing of forests the soils are not
immediately exhausted as the Oxisols are. Te r ra p r e ta contains significantly
more carbon (C), nitrogen (N), calcium (Ca), and phosphorus (P), and the
cation exchange capacity (CEC), pH value, and base saturation are signifi-
cantly higher in terra preta soils than inthesurroundingOxisols(Zechetal.
1990; Glaser et al. 2000).
Te r ra p r e ta soils contain up to 70 times more black carbon than the sur-
rounding soils. Due to its polycyclic aromatic structure, black carbon is
chemically and microbially stable and persists in the environment over cen-
turies (Glaser etal.2001). C14 ages of black carbon of 1,000–1,500 years sug-
gest a high stability of this carbon species (Glaser et al. 2000). It is assumed
that slow oxidation on the edges of the aromatic backbone of charcoal-
forming carboxylic groups is responsible for both the potential of forming
organo-mineral complexes and thesustainable increased CEC (Glaser et al.
2001). It can be concluded that in highly weathered tropical soils, SOM and
especially black carbon play a key role in maintaining soil fertility.
Black carbon has become an important research subject (Schmidt and
Noack 2000) due to its likely importance for the global C cycle (Kuhlbusch
and Crutzen 1995). Long-term studies with charcoal applications are needed
to evaluate their effects on sustained soil fertility and nutrient dynamics.
14.4
Slash and Char as an Alternative to Slash and Burn
After clearing the land foragricultural production, farmers use the wood for
charcoal production. The charcoal is produced in kilns close to the forest
edge (Fig. 14.1). The annual charcoal production of Brazil is 3.3 Gg (Gerais
1985). As of 1987, 86% of Brazil’s use of charcoal was for industry (i.e., iron
and steel) and 14% for residential and commercial purposes. Of wood used
for firewood and charcoal in Brazil in 1992, 69% came from plantations, 29%
from firewood collection, and 2% from sawmill scraps (Prado 2000).
Slash and Char: An Alternative to Slash and Burn Practiced in the Amazon Basin 185
Fig. 14.1. The charcoal drawing
illustrates slash and char in prac-
tice. AVeg e t a b l e p l a n t e d i n c h a r -
coal residues; Bbanana planting
hole filled with chicken manure,
soil, and charcoal; Con the sieve
table marketable pieces are sepa-
rated from charcoal dust and
small pieces, which are used in
agriculture
Only about 85% of the produced charcoal is marketable. On a sieve table
the different sizes are sorted out and filled into sacks for selling. Large
amounts of broken charcoal pieces and charcoal dust pass through the sieve
(Fig. 14.1C). These charcoal residues can be used in agriculture. The percent-
age of dust could be increased when organic materials other than wood are
included in the charring process.
14.5
Alternative Slash and Char in Practice
There is evidence that slash and char is practiced in a wide area of the Ama-
zon Basin. Coomes and Burt (1999) reported from the Peruvian Amazon near
Iquitos thatformosthouseholds,charcoalproductionisanintegralpartof
their swidden-fallow practices. On field excursions on an unpaved side road
leading from the Brazilian highway BR 174, 30 km into the forest, all visited
farmers settled on this road practiced slash and char. The agricultural prac-
tice of slash and char is also foundinthestate of Par´asouthofthe city Bel´em.
186 C. Steiner · W. G. Teixeira · W. Zech
Paragominas isknownforitstimberindustry. There the residues from the
sawmills are used for charcoal production, and the residues of charcoal pro-
duction for agriculture. These findings suggest that charcoal residues are fre-
quently used for agriculture where charcoal is produced.
Farmers around Manauswerevisited to observe their agricultural practices.
There is a high demand for charcoal in the nearby city of Manaus caused by a
preference for barbecued meat (churrasco). The majority of the farmers use a
permanent kiln. In such a kiln about 1,400kg of charcoal can be produced per
filling. A farmer with no access to the nearby city markets sells the charcoal for
US$ 0.17 per 2-kg sack. At the main road (BR 174) which goes from Manaus to
Presidente Figueiredo, the sacks already have a price of US$ 0.27. In Manaus
the sameunitissoldforUS$0.50.67 (US$ 1=3 Brazilian reais).
Coomes and Burt (1999) investigated charcoal producers near Iquitos in
the Peruvian Amazon region and found that the mean kiln producing 945kg
of charcoal requires a labor investment of 26 days. In their study area, char-
coal is produced in an earth-mound kiln, which demands more labor than
the permanent kiln type used near Manaus. A charcoal producer near the
EMBRAPA experimental research station loads his permanent kiln every
12 days. The labor investment is relatively small for the four production
stages. Wood is collected and prepared in 1 day by four workers (family
members), combustion is supervised for 4 days, charcoal is cooled for 8 days,
and than sackedbyfourworkersin1day.Cooling and combustion supervi-
sion require almost no labor input, allowing time for new wood procurement,
charcoal sacking, or agricultural activities. Charcoal producers close to rivers
shorten the cooling process by using water. Either 80–100 50-l sacks with a
mean weight of 15 kg or 400–500 sacks weighing 3 kg are filled. The producer
sells a large sack for US$ 1.00 and a small one for US$ 0.23. On the nearby
major road (AM-010), the big sacks are sold for US$ 1.67 and the small ones
for US$ 0.50. The monthly income fromcharcoalproduction is between
US$ 200 and 260, which is three to four times the minimum salary of US$ 66.
Charcoal producers reportthattheresiduesareusedfortheirownagricul-
ture and are also picked up by large-scale farmers. These cash crop farms are
usually cleared by bulldozer and do not produce their own charcoal. Four
types of charcoal use in agriculture were observed:
1. The residues from charcoal production are mainly used as an amendment
in planting holes. Mainly bananas (or other fruit trees) are planted in such
holes. Typically, the holes are about 30cm wide and 50 cm deep. These
planting holes are filled with chicken manure, charcoal, and soil
(Fig. 14.1B).
2. The slash and char farmers produce a kind of charcoal compost. Around
the charcoal kilns they dig holes in which the charcoal residues are depos-
ited in layers alternating with organic matter, ashes, and soil. After 1year
of decomposition the farmers use the created material as fertilizer applied
on the soil surface. Analyses of such a charcoal-compost show that it has
Slash and Char: An Alternative to Slash and Burn Practiced in the Amazon Basin 187
ahighpHvalue(6.88inH
2O) and is extremely rich in Ca (2,360.79 ppm),
Mg (1,241.2 ppm), and K (521 ppm).
3. Charcoal residues are used for vegetable and herb production in home
gardens. These gardens are planted in elevated planters, and the crops are
grown about 1.5 m above the ground to avoid damages caused by domestic
animals. These planters are filled with soil, charcoal residues, compost,
chicken manure, and other forms oforganicmatter(Fig. 14.1A).
4. Charcoal residues are applied on the soil surface. Farmers report that this
maintains soil moisture, especially during the dry season.
In addition, charcoal and charcoal byproducts are used in more technical
ways. Coal from geological deposits and from various specialized procedures
was successfullyusedforsoilamelioration. Adding charcoal to soil can sig-
nificantly increase seed germination, plant growth, and crop yields. Similar
observations were made after additions of humic acids from coal deposits
(Glaser et al. 2002). In the south of Brazil a liquid called pirolenhoso is
extracted out of the smoke from charcoal production. This technique comes
from Japan and the elixir has been used there for centuries to increase crop
productivity and quality and to combat diseases and pests in agriculture. So
far not much is known about the chemicalcomposition of the product, which
consists of more than 200 chemical compounds. For production the gases
from the charcoal kiln are captured andchanneledinawayto allow the con-
densation of the vapor. The extract is applied to the soil in a 1:100 dilution
with water. In spite of the lack of research, in practice this byproduct of char-
coal production hasbeen showing efficiency in controlling nematodes and
diseases. On the other hand, used as fertilizer, it increases the vigor and
improves the root building, the productivity, and the resistance of the plants,
and it increases the sugar content in fruits, which also have accentuated
colors and scents (Glass 2001). A growing number of organic farmers have
begun the production of pirolenhoso.Theysellthe product for US$ 0.33 l–1
and a farmer can produce about 600 l month–1.Themarketforthe extract is
very large in Brazil as well as in other countries, mainly in Japan (Glass 2001).
Other charcoal and byproduct uses include the following. A German com-
pany invented a product based on coal for the ecological improvement of all
types of soils. The product is sold as a soil conditioner and used in organic
farming and for restoration of degraded soils, mainly ski slopes (TERRA-
TEC, Finning, Germany). Chicken fodder is supplemented with charcoal.
Mario Miamoto, the owner of a large battery farm near Manaus (AM-010, km
38), adds 1% charcoal to the chickens’ nutrition inordertoassuage the mal-
odorousness of the manure, thus increasing the chickens’ appetite. He uses
about 2.5 tons of charcoal waste per month. The sameisdonewithcattlefod-
der to prevent digestion disorders. Osvaldo Sassaki used charcoal success-
fully for the development of hydroponic systems attheUniversityofAmazo-
nas. Osvaldo Sassaki used charcoal in these experiments as a nutrient-
sorbing material (O.K. Sassaki, pers. comm.).
188 C. Steiner · W. G. Teixeira · W. Zech
Tabl e 1 4 . 1. Biomass accumulation of secondary forest in Brazilian Amazonia (Fearnside
and Guimar˜aes 1996, with permission of Elsevier). The growth rate is highest in young
succession stages, creating an incentive for longer fallow periods in slash and char agricul-
ture. Fallows of between 8 and 12 years are sufficiently long for both charcoal production
and agricultural cultivation. (Coomes and Burt 1999)
Age Live biomass
(t ha–1)
Root/
shoot
ratio
Ave r ag e g ro w th
rate of total
biomass since
abandonment
(t ha–1 year–1)
Growth rate of
total live biomass
in intervalha–1
(t ha–1 year–1)(years) Wood Leaves Roots Total live
529.2 4.0 13.8 47.0 0.42 9.4 9.4
10 70.8 6.0 23.1 99.9 0.30 10.0 10.6
20 110.8 10.0 24.2 145.0 0.20 7.3 4.5
30 113.8 9.5 27.7 151.0 0.22 5.0 0.6
80 135.4 8.0 28.5 171.9 0.20 2.1 0.4
14.6
Advantages of Slash and Char
The advantages of slash and char agriculture as an alternative to slash and
burn need to be investigated in more detail, but the following statements can
be made already:
1. Charcoal provides income for rural households. Financial income could be
used to buy organic fertilizer such as chicken manure, which is cheaper
than charcoal and available around Manaus. The residues from charcoal
production together with chicken manure can improve the soil’s fertility
and decrease the amount of leached nutrients (Lehmann et al. 2003).
2. The incomefromcharcoalmarketingprovides an incentive for longer fal-
low periods because households practicing slash and char agriculture pre-
fer secondary regrowth of an age between 8 and 12 years. The removal of
wood for charcoal production does not diminish agricultural productivity
(Coomes and Burt 1999). The mean age of secondary forest cleared for tra-
ditional slash and burn agriculture is 5 years. The total biomass of second-
ary forest derived from farmland at the average age would be 50 Mg ha–1,
including fine litter and other dead above-ground biomass (Fearnside and
Guimar˜aes 1996), which is less than half the amount after a 10-year fallow
(Table 14.1). Slash and char as an agricultural practice provides increased
soil fertility through active improvement by organic matter applications
and by longer fallow periods. Additionally, the increased CO2reabsorption
in longer fallow periods and the charcoal amendments to soil transfer
more CO2from the atmosphere into biomass and finally into a stable form
of SOM.
Slash and Char: An Alternative to Slash and Burn Practiced in the Amazon Basin 189
3. Charcoal could improve the soil quality by changing soil physical parame-
ters such as bulk density, water retention, and water-holding capacity, a
significant advantage forplants,especially in the 4-month dry season.
4. Charcoal amendments seem to have insect-repellent properties. Farmers
report that charcoal amendments in banana planting holes keep the wide-
spread pest Cosmopolites sordidus (broca-da-bananeira)fromaffectingthe
plants. This beetle is a common crop pest in all areas of the world where
bananas are cultivated (Fancelli 1999).
5. The regeneration of primary forest species is much greater in areas that
are not burnt after felling. An unusually high occurrence of primary forest
species from the families Lecy thidaceae, Bignoniaceae, and Meliaceae was
found in anareaofsecondarygrowthnearManaus. The area where origi-
nal forest was cut, but not burned, to obtain wood for charcoal production
is unusually rich in young primary forest species. Far less damage is done
to the nativegenepoolwhentheareaisnotburned after clearing. This is
true not only because of the propensity of many felled trees to regenerate
from stump sprouts, but also because seed material is not destroyed
(Prance 1975).
6. The CO2balance between biosphere and atmosphere as a result of charcoal
production is neutral if regrowing wood from plantations or secondary
forest is used. The use of charcoal in agriculture would create a carbon
sink as a stable soil carbon pool.
7. An indirect advantage of slash and char is thatcharcoalcouldalsobepro-
duced in the wet season, when burningisnotpossible.Controlled year-
round charcoal production would distribute emissions around the year
and reduce the high aerosol emissions during the dry season. Artaxo et al.
(2002) predicted that the negative effects of burning are not locally
restricted. The emitted aerosols reduce solar radiation by about 40% in
the critical PAR region, which could lead to an average 3°C drop in tem-
perature during the burning seasons over regions as large as 3 million km2.
The reduced temperature and solar radiation seriously affect photosynthe-
sis, and further damage is caused by the phytotoxic gas ozone. Significant
ozone concentrations, in the order of 80–100 ppb, were observed in
regions far from the burnings. Furthermore, the aerosol emissions could
reduce precipitation in some regions by as much as 30%. Artaxo et al.
(2002) assumed that as much as half of the Amazonian forest could be
affected by secondary pollution. Altogether, these combined effects could
reduce the amount of water evaporating from the Amazon’s vegetation,
affecting weather worldwide.
190 C. Steiner · W. G. Teixeira · W. Zech
14.7
Slash and Char Research Activities
Charcoal powder was tested in a randomized multiple block field experiment
near Manaus, Brazil. Charcoal amendments (11 Mg ha–1)elevatedtheabove-
ground biomass productionsignificantlyonfertilized plots. In the second
cropping period the yield of sorghum (Sorghum bicolor)wasincreased by
880% in comparison with plots receiving just mineral fertilizer without char-
coal amendments. Charcoal amendments alone did not increase crop pro-
ductivity. These results strengthen the hypothesis that charcoal retains nutri-
ents and makes them available.
The claims thatcharcoalamendments in banana planting holes keep the
widespread pest Cosmopolites sordidus (broca-da-bananeira)fromattacking
the plants could not be confirmed. In a greenhouse experiment 20 banana
plants of two different varieties (Caipira and Prata Zulu) where planted in
pots. The soil was amended with chicken manure and lime. Ten plants
received additional charcoal amendments (one third of the volume). Four of
the ten bananas were infected by Cosmobolites sordius in the charcoal treat-
ment, showing clearly thatcharcoaldoes not repel those species. On the other
hand, five of the ten banana plants in the treatments without charcoal died,
apparently because of a lack of drainage. Insufficient water drainage affected
mainly the Caipira variety (four of five plants). Insufficient drainage was also
observed in a banana plantation north of Manaus (BR 174, km 102) where
rotten banana rhizomes were found in planting holes full of standing water.
Greenhouse experiments of Lehmann et al. (2003) showed that charcoal
additions increased biomass production of a rice crop by 17% in comparison
to a control on aXanthic Ferralsol. Combined application of N with charcoal
resulted in a higher N uptake than what would havebeen expected from fer-
tilizer orcharcoalapplicationsalone.Thereasonisahighernutrientreten-
tion of appliedammoniumbythecharcoal-amendedsoils.
14.8
Conclusions
The observed effects of charcoal applications in slash and char agriculture
seem to match the properties of the fertile anthropogenic terra preta soils in
the Amazon Basin. Charcoalproductionisalucrativeactivityandtransfers
SOM into stable pools when residues are used in agriculture. Where charcoal
is produced the residues are used for soil amelioration. Farmers evolved vari-
ous techniquestousecharcoal residues. Due to the relatively low nutrient
content, charcoal is mixed with chicken manure for planting holes or a
nutrient-rich charcoal compost is produced for surface application. This
compost could act asaslow-releasefertilizer. Inourexperiments, soil
charcoal amendments improved crop growth and yield significantly. We are
conducting further experiments to determine the mechanisms of soil
Slash and Char: An Alternative to Slash and Burn Practiced in the Amazon Basin 191
improvement through charcoal amendments and the efficiency of slash and
char agriculture. Should slash and char become common throughout the
tropics itcouldserveasasignificant carbon sink and could improve the sus-
tainability of tropical agriculture.
Acknowledgements. The research was conducted within SHIFT ENV 45, a German–Brazilian
cooperation, and financed by BMBF, Germany, and CNPq, Brazil. A financial contribution was
given by the doctoral scholarship program of the Austrian Academy of Sciences. We are grateful
for Johannes Lehmann’s (Cornell University) and Bruno Glaser’s (University of Bayreuth) valu-
able advice and for the fieldworkers’ help particularly Luciana Ferreira da Silva and Franzisco
Arag˜ao Sim˜ao and the laboratory technician, Marcia Pereira de Almeida. We thank Ilse Acker-
man for her comments on a draftofthispaper.
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ics. Geoderma 79:117–161
Slash and Char: An Alternative to Slash and Burn Practiced in the Amazon Basin 193
... No se conoce, sin embargo, el proceso por cual fueron creadas. Aunque no es muy común, también en la actua-lidad existe la práctica de añadir carbón vegetal a los suelos agrícolas para aumentar su productividad (Steiner et al., 2004;Miltner & Coomes, 2015). ...
Technical Report
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Policy paper about sustainable management of renewable natural resources in indigenous territories in nortwestern Amazonia
... In summarising the research on Amazonian Dark Earths (ADEs), Arroyo-Kalin (2014b) makes clear that a variety of contexts must be considered for its formation. In the Amazon, different kinds of dark earth are associated with a variety of land uses, with particularly deep and fertile ADEs formed by a build-up of midden or refuse material associated with sedentary settlement and less organically-rich ADEs with less intensive and repetitive behaviour, including past slash-and-char agricultural practices (Lehmann et al., 2003;Steiner et al., 2004;Glaser and Birk, 2012;Nigh and Diemont, 2013;Niu et al., 2015). ...
Article
Soils are a pivot of sustainable development. Yet, urban planning decisions persist in compromising the usability of the urban soils resource. Urban land cover expansion to accommodate an increasing population results in soil sealing. Concealment of and physical obstructions to soils prevent urban populations from engaging with their soil dependency. The concept of soil connectivity recognises that nurturing mutually beneficial soil–society relations is an essential dimension for achieving soil security. The concentrated populations of urban environments acutely require productive soil–society relations and offer the greatest potential for enhancing soil connectivity. Soil connectivity remains notably under-researched, however, resulting in deficient evidence to substantiate exactly how soil connectivity can contribute to sustaining urban life. The entanglement of soil and urban development has been critical throughout history, but seldom recognised in soil security discourse. We review the manifestation of effective soil connectivity in Precolumbian lowland Maya tropical urbanism. Archaeological evidence reveals, first, that lowland Maya urban settlement patterns largely preserved the availability, proximity, and accessibility of soils in the subdivision and configuration of urban open space. Second, Maya urban life included practices that proactively contributed to the formation of soils by adding to the stock of soils and improving beneficial soil properties of the thin and often nutrient-poor soils resulting from the regionally dominant karstic lithology. Third, a range of Maya landscape modifications and engineering practices enabled the preservation and protection of soils within urban environments. We derive evidence-based insights on an urban tradition that endured for well over two millennia by incorporating intensive soil–society relationships to substantiate the concept of soil connectivity. Inspiring urban planning to stimulate soil connectivity through enhancing the engagement with soils in urban life would promote soil security.
... The persistence of SOM and soil nutrients (e.g., phosphorus and calcium) is because much of the carbon is pyrogenic, which is highly recalcitrant and resists weathering in the high temperatures and precipitation regimes typical of Amazonia (Glaser, Lehmann, and Zech 2002). This pyrogenic carbon is formed during slow, cool burns with smoldering, a process identified as variations on "slash and char" in contrast to "slash and burn" (Steiner, Teixeira, and Zech 2004;WinklerPrins 2009;Arroyo-Kalin 2012). Soils with pyrogenic carbon absorb and retain nutrients and moisture better, and yield more plantavailable nutrients over the long term, a combination that contributes to their fertility. ...
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This article examines three intertwined forms of human transformation of Amazonia’s landscapes: (1) anthrosols, (2) cultural or domesticated forests, and (3) anthropogenic earthworks. By acknowledging the extent to which landscapes are humanized, an Anthropocene lens provides an opportunity to examine Amazonia as an Anthropogenic space (anthrome), providing a more realistic approach to understanding the region’s past and for guiding its conservation. ©, This work was authored as part of the Contributor's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 USC. 105, no
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A paisagem manejada através dos conhecimentos tradicionais das Comunidades Fundo de Pasto, formam um agroecossistema baseado em três distintos subsistemas, o primeiro são as áreas de Fundo de Pasto, parcela do território considerada de posse coletiva e manejada através da gestão comunitária dos recursos naturais. Essas áreas preservam a Caatinga de forma contínua sem cercas, onde circulam livremente a fauna silvestre e os rebanhos de caprinos e ovinos. O segundo subsistema é denominado de Cercado dos Animais, espaço com vegetação nativa cercada para o manejo reprodutivo dos rebanhos com diferentes subdivisões e piquetes sendo gerida de forma autônoma pelas famílias. O terceiro subsistema são as áreas destinadas aos Roçados e Quintais Produtivos, que correspondem às pequenas parcelas de terra desmatada, com a presença marcante das árvores nativas de umbu preservadas. Essas áreas são utilizadas para o cultivo de lavouras temporárias e perenes de plantas alimentares e forrageiras.
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O umbuzeiro ou imbuzeiro (Spondias tuberosa Arruda) é a principal espécie frutífera endêmica do bioma Caatinga. Planta xerófila da família Anacardiaceae, possui alta variabilidade genética e fenotípica e se encontra dispersa em toda a região do Semiárido. Seu nome tem origem no tronco linguístico Tupi, dos fonemas “ymbu” ou “ymbuyrá” que significam “árvore que dá de beber”, derivados dos sufixos y-água, u-beber, ybyrá-árvore, yburá-água que brota de cima/manancial. Isso demonstra o amplo conhecimento que os povos nativos da região tinham sobre os múltiplos usos da planta, desde suas raízes formadas por túberas, capazes de armazenar água e nutrientes, aos seus frutos, folhas, cascas e sementes, compondo assim uma rica e estratégica fonte alimentar na dieta dos povos coletores e caçadores que habitaram a Caatinga por milhares de anos, até a chegada dos colonizadores europeus.
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The two book chapters in this section synthesize William Denevan’s thinking about how Native Amazonians created and managed agroforestry systems for food production and in the process created an anthropogenic soil called brown earth (terra mulata). The practices involved were labor intensive, because of the use of stone and wooden tools, allied with burning of semi-dry organic wastes, resulting in continual additions of charred biomass to the soil, which fertilized the food plants and created these brown earths. William Denevan did not use the term agroecology, but many of these practices are resurgent today in agroecological farming methods.
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This review highlights the ubiquity of black carbon (BC) produced by incomplete combustion of plant material and fossil fuels in peats, soils, and lacustrine and marine sediments. We examine various definitions and analytical approaches and seek to provide a common language. BC represents a continuum from partly charred material to graphite and soot particles, with no general agreement on clear-cut boundaries. Formation of BC can occur in two fundamentally different ways. Volatiles recondense to highly graphitized soot-BC, whereas the solid residues form char-BC. Both forms of BC are relatively inert and are distributed globally by water and wind via fluvial and atmospheric transport. We summarize, chronologically, the ubiquity of BC in soils and sediments since Devonian times, differentiating between BC from vegetation fires and from fossil fuel combustion. BC has important implications for various biological, geochemical and environmental processes. As examples, BC may represent a significant sink in the global carbon cycle, affect the Earth's radiative heat balance, be a useful tracer for Earth's fire history, build up a significant fraction of carbon buried in soils and sediments, and carry organic pollutants. On land, BC seems to be abundant in dark-colored soils, affected by frequent vegetation burning and fossil fuel combustion, thus probably contributing to the highly stable aromatic components of soil organic matter. We discuss challenges for future research. Despite the great importance of BC, only limited progress has been made in calibrating analytical techniques. Progress in the quantification of BC is likely to come from systematic intercomparison using BCs from different sources and in different natural matrices. BC identification could benefit from isotopic and spectroscopic techniques applied at the bulk and molecular levels. The key to estimating BC stocks in soils and sediments is an understanding of the processes involved in BC degradation on a molecular level. A promising approach would be the combination of short-term laboratory experiments and long-term field trials.
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The Lecythidaceae of a 2500 m2 area of the secondary forest of INPA was studied. The 97 individuals of Lecythidaceae present indicated a high number of primary forest species. It is concluded that most of the area was not burnt when the original forest was cut, and the regeneration of primary forest species is much greater in areas which are not burnt over after felling. This is further supported by parallel studies of Bignoniaceae and Meliaceae of the same area.
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Twelve 60-m2 plots were cut and weighed in a clearing at a cattle ranch near Manaus, Amazonas, Brazil. Aboveground dry weight biomass averaged 369 metric tons (Mgha−1) (SD=187). This corresponds to ≈483Mgha−1 total biomass. Pre- and post-burn aboveground biomass loading was evaluated by cutting and weighing, and by line-intersect sampling (LIS) done along the axis of each quadrat. Because direct weighing of biomass disturbs the material being measured, the same quadrats cannot be weighed both before, and after, the burn. The high variability of the initial biomass present in the quadrats made use of volume data from the LIS more reliable for assessing change in the biomass of wood >10cm in diameter; estimates of changes in other biomass components relied on data from direct weighing. Estimates of initial stocks of all components relied on direct measurements from the pre-burn quadrats; in the case of wood >10cm in diameter this was supplemented with direct measurements from the post-burn quadrats adjusted for losses to burning as determined by LIS. The measurements in the present study imply a 28.3% reduction of aboveground carbon pools. This estimate of burning efficiency is in the same range obtained in other studies using the same method, but two other methods in use in the Brazilian Amazonia produce consistently different results, one higher and the other lower than this one. Charcoal made up 1.7% of the dry weight of our remains in the post-burn destructive quadrats and 0.93% of the volume in the line-intersect sampling transects. Approximately 1.8% of the pre-burn aboveground carbon stock was converted to charcoal.
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Deforestation in the Brazilian Legal Amazon releases substantial amounts of greenhouse gases. Net committed emissions (the long-term result of emissions and uptakes in a given area that is cleared) totaled 267-278 million t of CO2-equivalent carbon in 1990 (under low and high trace gas scenarios), while the corresponding annual balance of net emissions (the balance in a single year over the entire region, including areas cleared in previous years) in 1990 was 354-358 million t from deforestation plus 62 t from logging. These figures contrast sharply with official pronouncements that claim little or even no net emission from Amazonia. Most emissions are caused by medium and large ranchers (despite recent official statements to the contrary), a fact which means that deforestation could be greatly slowed without preventing subsistence clearing by small farmers. The substantial monetary and non-monetary benefits that avoiding this impact would have provide a rational for making the supply of environmental services a long-term objective in reorienting development in Amazonia.
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In Amazonia, land-uses requiring large inputs of labour and other resources per hectare, such as annual and perennial crops, can be expected to decrease in relative importance as compared with uses such as cattle ranching and forest cutting for timber and charcoal. Cattle ranching has already claimed the largest share of cleared areas in the region, even in comparatively fertile areas including Rondônia in southwestern Amazonia where crops such as cacao account for most credit disbursement and official fanfare. The trend to cattle pasture includes expansion within small-farmer settlement zones—a process spurred by turnover in the colonist population. In other areas of the region, the trend to ranching stems from continued proliferation and expansion of large concerns which profit both from speculative gains and various governmental subsidies.
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Soils in Brazilian Amazonia may contain up to 136 Gt of carbon to a depth of 8 m, of which 47 Gt are in the top meter. The current rapid conversion of Amazonian forest to cattle pasture makes disturbance of this carbon stock potentially important to the global carbon balance and net greenhouse gas emissions. Information on the response of soil carbon pools to conversion to cattle pasture is conflicting. Some of the varied results that have been reported can be explained by effects of soil compaction, clay content and seasonal changes. Most studies have compared roughly simultaneous samples taken at nearby sites with different use histories �i.e., ‘chronosequences’.; a clear need exists for longitudinal studies in which soil carbon stocks and related parameters are monitored over time at fixed locations. Whether pasture soils are a net sink or a net source of carbon depends on their management, but an approximation of the fraction of pastures under ‘typical’ and ‘ideal’ management practices indicates that pasture soils in Brazilian Amazonia are a net carbon source, with the upper 8 m releasing an average of 12.0 t C/ha in land maintained as pasture in the equilibrium landscape that is established in the decades following deforestation. Considering the equilibrium landscape as a whole, which is dominated by pasture and secondary forest derived from pasture, the average net release of soil carbon is 8.5 t C/ha, or 11.7 x 10 6 t C for the 1.38 x 10 6 ha cleared in 1990. Only 3% of the calculated emission comes from below 1 m depth, but the ultimate contribution from deep layers may be substantially greater. The land area affected by soil C losses under pasture is not restricted to the portion of the region maintained under pasture in the equilibrium landscape, but also the portion under secondary forests derived from pasture. Pasture effects from deforestation in 1990 represent a net committed emission from soils of 9.2 x 10 6 t C, or 79% of the total release from soils from deforestation in that year. Soil emissions from Amazonian deforestation represent a quantity of carbon approximately 20% as large as Brazil’s annual emission from fossil fuels.
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The study deals with soils of the Brazilian part of the Amazon basin. Most soils are Latosols, some with soft or hardened plinthite. The Latosols are characterized by a latosolic B horizon as defined in Brazil.Plinthite, its formation and morphology were extensively described. Five main types of hard plinthite were distinguished. The rather uniform soils of the Amazon Planalto proved to be mainly Kaolinitic Yellow Latosols.Various intergrades toward Groundwater Laterites and Red Yellow Podzolic soils were shown to exist.Special attention was given to the relation between the soil conditions and vegetative cover. The mean gross timber volume and the presence of specific tree species were discussed.The suitability was assessed of the soils for agricultural production, especially vegetables, cash crops and some perennials such as oil palms.
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This review highlights the ubiquity of black carbon (BC) produced by incomplete combustion of plant material and fossil fuels in peats, soils, and lacustrine and marine sediments. We examine various definitions and analytical approaches and seek to provide a common language. BC represents a continuum from partly charred material to graphite and soot particles, with no general agreement on clear-cut boundaries. Formation of BC can occur in two fundamentally different ways. Volatiles recondense to highly graphitized soot-BC, whereas the solid residues form char-BC. Both forms of BC are relatively inert and are distributed globally by water and wind via fluvial and atmospheric transport. We summarize, chronologically, the ubiquity of BC in soils and sediments since Devonian times, differentiating between BC from vegetation fires and from fossil fuel combustion. BC has important implications for various biological, geochemical and environmental processes. As examples, BC may represent a significant sink in the global carbon cycle, affect the Earth's radiative heat balance, be a useful tracer for Earth's fire history, build up a significant fraction of carbon buried in soils and sediments, and carry organic pollutants. On land, BC seems to be abundant in dark-colored soils, affected by frequent vegetation burning and fossil fuel combustion, thus probably contributing to the highly stable aromatic components of soil organic matter. We discuss challenges for future research. Despite the great importance of BC, only limited progress has been made in calibrating analytical techniques. Progress in the quantification of BC is likely to come from systematic intercomparison using BCs from different sources and in different natural matrices. BC identification could benefit from isotopic and spectroscopic techniques applied at the bulk and molecular levels. The key to estimating BC stocks in soils and sediments is an understanding of the processes involved in BC degradation on a molecular level. A promising approach would be the combination of short-term laboratory experiments and long-term field trials.
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This study was performed to quantify the black carbon content of vegetation fire residues for use in assessing the impact of vegetation fires on atmospheric carbon dioxide levels. Samples of laboratory fire residues from different vegetation types were analyzed for black carbon and corresponding hydrogen. Two pretreatment steps removed all inorganic and organic carbon. An elemental analysis was then conducted to quantify black carbon and its hydrogen/carbon (H/C) ratio. Results of 22 experimental fires are presented which demonstrate that black carbon is definable as the fire produced carbon fraction with molar H/C ratio of ⤠0.2 which is resistant to heating to 340 C in pure oxygen. Correlation studies of black carbon formation to the carbon monoxide/carbon dioxide ratio of emissions showed that the major source of black carbon is flaming combustion. More than 80% of the black carbon produced by vegetation fires was found to remain in the fire residues. Based on the ratios determined of black carbon to emitted carbon dioxide and to the fire exposed carbon, the annual global black carbon formation was estimated to be from 50 to 270 teragrams per year. The fire-induced sequestration of carbon from the short-term biospheric cycle to the long-term geological cycle may be a significant sink of atmospheric carbon dioxide and source of oxygen, and should be considered in atmospheric analyses. 54 refs., 3 figs., 4 tabs.