Terra Preta
In order to describe and to define the TP and also the surrounding Latosol, it was necessary to visit a TP site, map it in the field, describe it and bring sample material to Germany for analysis. It was therefore essential to go to Brazil and carry out research in the field.
Since it was not possible to research from Germany with sufficient accuracy, at which locations there are distinct TP sites worth investigating, what type they are and whether they are still in the same condition as when they were mentioned in the literature (see para 1.4), the selection of the TP location could not already be made in Germany.
Contact with the Brazilian state authorities and their approval also had to take place on site in Brazil, since problems arose when applying for a research permit through the diplomatic representation in Germany. After many decades of the dominance of foreign, scientific research projects - with the return of the research results to the implementing countries, above all the USA, but also Western Europe and Japan, so that the results in Brazil were often not even available - a tendency developed in Brazil towards scientific self-sufficiency and the exclusion of foreign institutions.
The result is the national research that Brazil is striving for and the development of its own scientific education and research system, in which foreign research projects in cooperation with Brazilian government agencies are difficult, without this cooperation are not possible.
Initial contacts in this regard via German institutions in Manaus (consul, existing German research projects) turned out to be negative.
In Belem, on the other hand, FAO coordinator J.Dubois could be won, who in turn mediated to I.Falesi, director of EMBRAPA, today Minister of Agriculture of the State of Pará, known for his research at the TP through several publications (see para 1.2.3). He showed interest and assured the approval and assistance of EMBRAPA, Belem. As a result, however, the region with possible TP sites to be investigated was limited to the state of Pará.
The tropical rain forest places special demands on the soil scientist. Overcoming huge distances in an area with very poor transport connections often causes great difficulties or at least causes long delays. It therefore took the author several weeks to travel in the Amazon region before he found the first occurrence of TP.
A further problem was the procurement of the work equipment. For financial reasons it was not possible to take special tools from Germany, so that digging tools such as spades, pickaxes, shovels and hoes had to be procured in the exploration area, frames for humus recording and for volume samples, packaging material as well as a drying cabinet and precision scales had to be organized or made first on site.
A basically indispensable piece of equipment, the Pückhauer drill, could neither be bought, borrowed nor manufactured locally, so that the very difficult task due to the small size of the TP deposits, of extensive exploratory work were made considerably more difficult.
Another difficulty, the provision of manpower, was solved satisfactorily by choosing Belterra and the cooperation of EMBRAPA.
Only very few areas of Amazonia are mapped, which goes beyond a scale of 1:250,000.
Pedological maps are only available on a very small scale, e.g. those in para 2.6.3 listed 1:5 million map - and then only of limited interpretation - or of selected, smallest areas, for example along newly laid roads, e.g. on the route Manaus - Itacoatiara (IPEAN 1969). In the region around Santarém - Belterra, however, topographical sketches on a scale of 1:250,000 and 1:25,000 were made by the Americans in 1935 (unpublished). By inspecting the terrain and measuring with tape and compass, they were corrected and expanded at the most important points and form the basis of the maps.
For climatic reasons, pedological work is only possible in the 2 - 4 drier months (see para 2.3), since in the rainy season it is very difficult to search for TP localities and excavation work is impossible.
Daily precipitation of more than 10 to more than 20 mm quickly fill up soil pits.
The vegetation, on the other hand, does not pose an insurmountable problem. In the region around Belterra there is an extensive network of paths (see Chap. 3.4). Away from these paths and in less developed areas, advancing through clearing is time-consuming, but always possible, even in dense undergrowth. Despite the small size of the TP occurrences, the immediate vicinity of large trees could be avoided during excavations, so that no excessively dense root stock made the excavation difficult.
Likewise, the threat posed by dangerous animal species has long been overestimated. Nonetheless, several times larger snakes have been taken and tarantulas killed during exploration. A worker was bitten by a scorpion.
After consulting pedologists and archeologists, especially at EMBRAPA and the Goeldi Institute, Belem, and studying the literature on specified TP localities, the following locations were shortlisted:
Due to the limited time - the onset of the rainy season makes pedological work impossible - and the limited financial possibilities and work permits, the decision was made in favor of the occurrence on the Belterra plateau, since these well developed and are 'clear' TP in terms of size, thickness, abundance of fragments and organic substance and geological, morphological, cartographic and pedological characteristics. Some early work has already been done in this area.
Franco wrote his own work on the creation of the Belterra TP (1962, see Chap. 1.2.3), Sampaio mapped - not without controversy - the entire area as TP and 'Terrra Mulatta' (1962, in Sombroek 1966, p 175; fig 20 in Chap. 3.6). Furthermore, chemical analyzes of nearby TP were made (Ranzani. et.al.1962; Sombroek 1966, p.159 a.o.; Tab.4 in Chap.6). Americans drilled a geological depth profile to a depth of 122 m (1937, unpublished; fig.7 in Chap 2.1.3), there is a separate climate measuring station (previously unpublished data; Tab.1 and fig.12 in Chap. 2.3.2).
Based on investigations there, the term 'Belterra Clay' was coined as a geological formation that strikes out at the surface in large parts of Amazonia (see Section 2.1.3 and fig. 4).
Last but not least, this area was chosen for the investigations because in this plantation created by Ford in 1934 there are extensive infrastructure facilities, such as a developed network of roads, an agricultural station (Posto) of EMBRAPA with vehicle park, tools, work equipment, scales etc. as well as accommodation, workers, even a small hospital. The daily bus connection to Santarém, 40 km away, with all supply options was also seen as a great advantage.
The offer of EMBRAPA as manager of the plantation and agricultural station to operate from Belterra and to be supported there with off-road vehicles, workers, working materials, maps etc. was therefore accepted.
The TP found near Belterra fulfills all the requirements to be a 'typical representative' of this soil type, such as clear expression, high C content and the presence of ceramic remains (see Chap.1.1.2), but also other characteristics such as gradual transition to Latosol, high fertility, looseness, relative homogeneity within a deposit, etc.
The Belterra site meets all other requirements as a starting point for the investigations, such as relatively good accessibility, the possibility of pre-treating and transporting the samples away and creating profiles of the soil type to be compared (Latosol profiles) nearby.
The latter point, which was not taken into account when planning and selecting this location, became a problem on site, since in the immediate vicinity of the TP deposits none of the TP unaffected Latosols were found, so that a larger distance between TP and Latosol reference areas had to be accepted.
Initially, there was only one critical point in the decision to choose Belterra as the location: a possible anthropogenic review by the plantation industry over the last 45 years. Measures such as clearing, constant thinning of undergrowth, cultivation with a monoculture and nutrient deprivation can produce strong changes in the soil. However, this problem was solved by selecting TP areas outside of the former plantation area.
The Latosol comparison surface with 5 profiles (SL 1-5) was selected at the edge of the plantation area - which had been abandoned for ca 25-30 years. The comparison with another Latosol sample area (profile SL 7) or its analytical data and Latosol profiles drawn with values from other authors (e.g. EMBRAPA 1975) confirmed. Not even the profile completely in the former plantation area SL 6 shows different values (see Chap.3.7.3).
Due to the necessary, very extensive site survey in the Belterra area (see Chap. 3.5), the work was delayed more than originally planned. Because of the onset of the rainy season in December, no further TP deposits could be visited. The original plan was to look for another TP site, which differs from the Belterras either in terms of the parent substrate (e.g. sandy TP) or in terms of vegetation (e.g. under 'primary forest'). But these plans had to be cancelled.
3.4 Location Description of Belterra
Belterra is located ca 40 km S of Santarém, only ca 1-3 km E and S of the steep slopes of the Planalto (see GIS online map to zoom and all profile locations). This tertiary, undestroyed plateau is made up of ca 40-50 m deep layers of clay, the so-called Belterra clays, from kaolinitic sediments of a Pliocene lake (see Chap 2.1.3 and fig.7): The terrain itself is completely flat, only interrupted by a few, closed, round depressions of ca 100-300 m in diameter and ca 10-20 m depth, the already mentioned Depressãos fechados (seeChap. 1.2). (See also field map).
Geomorphological work has not yet been carried out in this area (see also Chap. 2.2).
The entire plateau is ca 165 m above sea level (Sioli 1969, p.318 and others) and thus more than 100 m higher than the parts of the Terra Firme below the steep slope along the Tapajos and Amazon banks (ca 30 m above sea level). The escarpment is very intricate and twisted, forming several spurs. The break is clearly pronounced.
The transition from the level to the slope, often with an incline of 400 or even 450, takes place at a distance of ca 20-30 m. 228;this is probably due to soil genetic hardening processes in the upper layers (ca 1.00-1.50 m).
Due to the greater dehydration in vicinity of the slope during the dry season, there is an increased precipitation of Fe oxide.
Such lateritization processes, caused or reinforced by the better drainage of the laterally withdrawing water here, lead to a compact, solidified laterite horizon at a depth of 1-2 m at the escarpments of the plateau (more 'nodular laterite' than 'massive laterite').
In terms of soil science, this is known as plinthic Ferralsol (Fp; see Chap.2.6.1) or as containing laterite or even as laterite - in contrast to Latosol - or as Lateritico to address The two laterite profiles SP 9 ca 40 m before the escarpment and SP 0 ca 5 m below the escarpment at the slope (see Chap. 3.7.2) confirm the model by Townshend (1970, p.397):
Fig.15: Plateau laterite at the slope crest (nach Townshend 1970; Young 1976)
As the figure indicates, the laterite crusts also very quickly thin out from the escarpment to the plateau, and they no longer appear at a short distance (Sivarajasingham et.al.1962, p .50).
These 'plateau laterites' (according to McFarlane 1976; Townshend 1970) depend on the principle of a homolithic strata (Louis 1979, p.333) the formation of sharply defined plateau and terrace escarpments, where lateral erosion does not cause the levels to drop or the edge to flatten, but instead incises and cuts into the plateau edges. This cliff therefore consists of an alternating succession of spurs, ridges and gorges and cuts covered, as can also be seen well on the maps fig. 14 and 17.
Fig.16: Formation of plateau laterite (Young 1976); right profile relates to SP O
The region around Belterra has a long history of settlement, as can be seen from the pottery finds, historiography and the TP origin theories (see Chap.1.2). In its current form, Belterra was only built in 1934 by the American 'Companha Ford Industrial do Brasil' (Plantacoes Ford de Belterra).
The reason for this lay in the Americans' considerations of autonomy for their rubber needs. Because of the Stevenson Plan 1922-28, people feared their own - overpriced - pricing policy by the English in the sale of Indian-Malaysian rubber, which at that time almost exclusively dominated the market. The US Department of Commerce therefore looked for ways to set up a crisis-proof rubber plantation in other tropical countries. Ford therefore in 1927 began clearing and establishing plantations at Fordlandia 100 km to the S, after failures there in 1934 at Belterra, which had the advantage of being level and thus allowing the use of machinery.
Whether the higher fertility of this area as a result of the TP was an argument for the selection of this location is unknown, but cannot be ruled out.
In 1939, around 50 qkm of the total area of 2428 qkm were planted with (2 million) rubber trees (Hevea brasiliensis). A leaf disease that occurred in Fordlandia, which can only spread to such an extent in monocultures and which ultimately led to the abandonment of this planting, was prevented by two grafts in Belterra, resulting in a resistant cross-breeding of native rubber trees and oriental scions. However, since this cultivation was very labor-intensive and cost-intensive and the demand for rubber as a raw material decreased after World War II, Ford sold the plant to the Brazilian government in 1945, which continues to operate it on an ever smaller scale through EMBRAPA.
Today the tree population in Belterra is over-aged, the undergrowth is no longer cleared out, in the former plantation areas the capoeira (secondary forest) is becoming more and more popular. Rubber is only tapped to a small extent - for the production of chewing gum.
Today only about one fifth of the former population of ca 8-10,000 inhabitants still lives in Belterra (Zimmermann 1958, p.80).
A part of the road network with 3 W-E and 5 N-S routes is still preserved today, further afield (dashed lines in fig. 17) are often no longer passable. The rectangular subdivision into 441 planned or 310 plots planted with rubber trees (with a side length of 404 m) is no longer recognizable on the site and is located approximately within Estrada 1 and 7, and between 2 and 10, respectively (see map fig.17).
In addition to the course of the slope and the layout of the settlement and the paths, this map also shows the situation of the examined profiles:SP 1 - 5 lie on a spur far outside the former plantation area, SP 9 and SP 0 right at the escarpment, SL 1 - 5 at the very edge of the former plantation and therefore the earliest to be abandoned, SL 6 in relatively long cultivated terrain andSL 7 completely outside the former plantation (see Chap.3.7).
During exploration, a number of TP sites, some linked to each other, some isolated, have been identified, visited and mapped.
The focus was on following questions:
The descriptions thus referred primarily to the recording of the humus content, the thickness of the TP-typical Ah horizons, the texture as well as the form, extension and relief situation of the site and quantification of the ceramic pieces. For each detected TP occurrence, several profiles (ca 5-10), more than 30 (!) in location 1 alone, were dug and samples taken in order to be able to compare the different TP intensities directly with one another in a color comparison.
The aim of this field work was, in addition to the first large-scale mapping of TP occurrences and their identification, the selection of a typical, well-defined and undisturbed site in which the profiles for sampling should be created .
3.5.2 Description of 19 Surveyed Sites
Following TP sites have been identified:
Located in the centre of Belterra, this TP is undoubtedly the largest and deepest. Its center is at the beginning of Estrada 1, roughly between the EMBRAPA office and the hotel. Its centre is a circle with a diameter of ca 400-500 m. Its core area is thus ca 14-18 ha. With this size it is very large compared to other TPs mentioned in literature (location: 2.6374 S - 54.9361 W, further description in Chap. 3.7.2).
The transition zone to Latosol is accordingly large. This extends ca 500 m to the N and S and connects there + to the TP site 2 (see below). To the E it reaches just before the Praca, i.e. ca 250 m beyond the core area. To the W it ends soon. because of the steep escarpment slopes of the Planalto there. At the top of the escarpment there is a typical TP (SP 9), only 5 m below (SP 0) high C content and ceramic residues were still found, but other properties such as Ca and Mg content etc. are no longer typical of TP, as chemical analysis also shows. After a further difference in altitude of only 5-10 m, the TP character has completely disappeared. Then laterites and strong, but stronger reddish shades dominate because of the stronger Fe accumulation there (orthic, plinthic ferralsols; see also Chap. 3.4.1). 2 profile pits were excavated here (SP9/0, see profile descriptions).
Apart from this relief-related peculiarity, the 'lens theory' of Franco (1962, see Chap. 1.2.3) can be confirmed, see small, schematic representation of isocarbonals (lines with same C content) below.
Fig.18: Isocarbonale representation of a typical TP site (as no.1)
(Crosses indicate pottery)
The entire TP site has an area of 120-150 ha. The extent with increased humus content is approx. 1/3 larger than indicated on the map (fig. 17). Pottery was found on a smaller 'inner' part of this TP, but here in abundance, even partly on the surface or on the road.
Ca 1 km S of this location E of Estrada 2 a TP has developed which is significantly 'weaker'. It has a core area of ca 50 m in diameter and is only half as deep. In terms of off-road response, this TP already resembles the surrounding Latosol from a depth of around 40 cm. The transition area extends in a circle over an area of ca 5 ha or slightly more (Locality: 2.6534 S - 54.9371 W).
The proximity to the above TP suggested that both TPs are connected and are only separated from each other by a zone of weaker expression. Therefore, 5 test profiles were created along a straight line to examine this transition. When moving away from location 1, the topsoil horizons gradually became lighter and brighter, the 'thickness' of the TP became smaller and smaller, no more pottery could be found. After ca 2/3 of the distance the floor was addressed as Latosol. Approaching location 2, the soil became darker again, the humus Ah more powerful and even closer to the pottery were also found in the center.
Fig.19: Isocarbonalen representation of the transition from TP site 1 to 2, schematized
A similar connection may exist to the third visited TP in close proximity (400m SW site 2), ca 100m N of the cemetary. The size of the core area is considered very small (ca 0.1 ha). Very few pieces of pottery have been found.
If the previous 3 TP localities + were related to each other, this is not the case with the site SW of the intersection Estrada 4 with 3, which only has a very small extent (below 0 .1 ha), but has a medium intensity (darkerAh to a depth of ca 30 cm). It is under intensive agricultural use in a vegetable field by a cottage (location: 2.6530 S - 54.9370 W).
To the W of the landing field, the TP site 'C.B.A.' is located on a pronounced spur that protrudes almost 500 m above the rest of the slope. Black topsoil and therefore higher humus content was found on all high parts of this spur, i.e. at the level of the plateau. However, the dark coloring quickly disappears down the slope, as already surveyed in site 1, and when approaching the actual plateau, i.e. when leaving this spur. This TP therefore only covers ca 0.5 ha, the transition area is relatively small at 1-2 ha. Very few pieces of pottery were found (location: 2.6709 S - 54.9648 W).
On another, very exposed spur on the NW corner of the Belterra Plateau, the very pronounced TP Chico Alfredo was found. In terms of its intensity, i.e. the humosity, and the depth of the Ah horizons, it almost matches the 1st site, but it is considerably smaller, but still larger than the others mentioned. In the actual core area, it covers an area of ca 0.65 ha. It radiates over 2-5 ha with an increased humus content (location: 2.6003 S - 54.9439 W).
It is discussed in detail in Chap.3.7.1 due to its favorable, TP-typical properties. 7 profile pits were excavated here (SP1/2/4-8, see profile descriptions).
Ca 2.5 km to the E, at a short distance from the escarpment, is the weaker TP 'Dourado' with a smaller area and only a moderately black, not particularly deep Ah (location: 2.6167 S - 54.9227 W).
Not far away, the site 'Cacoalinho', ca 2.5 km NE of the Praca, shows some of the darkest black hues in the topsoil (lowest value values; ca 1.5-2) and therefore presumably the highest humus content (location: 2.6179 S - 54.9146 W). However, this intense expression diminishes very quickly with depth and from a depth of ca 50-60 cm can already largely be regarded as latosol. The intensive black tone is only limited to a very small area of 30-40 m in diameter.
Ca 500 m to the N is another, weaker (sub-)centre of this site.
The transition between these two TP areas was also examined. There is some typical Latosol in between. However, due to the close proximity of these two TPs, the same site is spoken of.
The TP area 'Mt. Christo' with moderate pottery finding has an average overall size, its core area with a relatively high humus content is relatively small. Already at a depth of ca 25 cm, the TP merges into the Latosol (location: 2.6030 S - 54.8793 W).
Extreme abundance on pottery characterizes the TP of 'Santo Antonio', also directly on the escarpment on a spur similar to 'C.B.A.' or Chico Alfredo with a deep black Ah up to 40 cm. But here, too, the transition to the light hues of the Box often occurs very quickly and abruptly (location: 2.5968 S - 54.8609 W).
A relatively deep, very dark TP with a lot of pottery is that of 'São João' ca 12 km NE of Belterra, 500 m from the escarpment. It has been accurately recorded and mapped. The core covers almost 1 ha, the transition area ca 10-15 ha (location: 2.5796 S - 54.8425 W).
Because of an optimal transition from ca 500 m to the Latosol, a longitudinal profile of the soil association with 5 soil profiles was drawn here, which is intended to characterize the transition from the center of the TP to the Latosol.
The 38 samples taken were sent to Germany. So far, only the volume weights of these samples have been determined in analyses. The strong decrease in volumetric weight from Latosol to TP observed in the field could be proven.
A few kilometers to the S, but at a greater distance from the escarpment, is the TP 'São Francisco', which also has very rich abundance of pottery. The center is slightly < 1 ha. In the upper 30 cm the colour is + intense black, which quickly decreases in the next 20 cm (location: 2.6068 S - 54.8458 W).
After Moreira d.S. Indians still settled here until about 1920/30 (oral communication).
S of Estrada 7 near the water tower is another, very small TP with a not too small thickness (ca 40 cm) of a deep black (value ca 2) Ah-horizon, which then very quickly changes to the colors of a yellow Box. Despite the small extent, pottery was found in abundance on and in the ground. The actual core area of ca 0.1 ha is mainly on a small hill (ca 20-30 m in diameter) and goes very quickly into the surrounding Latosol (location: 2.6843 S - 54.9044 W).
Only ca 1 km further W, also S of Estrada 7 in terrain with a stronger relief, an isolated TP with a somewhat larger extent was found, but a lower intensity of the humus (less deep and lighter) and merging even faster into the underlying latosol, noted (location: 2.6832 S - 54.9203 W).
3-4 km S of Estrada 7 on the road to Capim is the TP site 'Castanheiras' right next to a small depression (Depressao Fechado of ca 20 m diameter and 3 m depth). Its area is only very small. The faint black color fades after ca 20 cm. Only a moderate number of pottery were found (location: 2.7276 S - 54.9561 W).
On the road to Aramanay on the Tapajos on the pepper plantation of Sr. Coleman there is a TP that shows a dark coloring of the upper 10-30 cm, but no pottery in the examined area. The actual center was not visited because of the recent planting. But pottery is to be expected there. The actual TP area is assumed to be medium-sized (ca 2-5 ha) (location: 2.6875 S - 54.9787 W).
Below (!) the steep slope, in a more sandy substrate, two TPs were visited near Tijucal. Their sizes were estimated despite the inaccessibility of the terrain. The intensity is only moderate, below ca 30-40 cm the strongly silty to sandy Latosol (location: 2.5814 S - 54.8817 W).
The TP of Pedreira lies in completely sandy terrain on the road to Pindobal, below the plateau drop. It is very extensively black and small in size (0.2 ha). A number of pottey pieces demonstrate the anthropogenic origin (location: 2.6391 S - 54.9557 W).
In the vicinity of Santarém, on the local, purely sandy substrate, in several places, e.g. in Santarém, at the IBGE station, etc., humus topsoil horizons and partly overabundant pottery were found (see Chap. 1.4, para.28). However, all the profiles created indicate extreme disturbance through agricultural use or construction measures, so that undisturbed profiles and thus soil samples could not be taken. Already Barata (1953, p.4, in Palmatary 1960. p.24) expresses that in the vicinity of Santarém, although strongly pronounced TP exists, but this is not worth investigating because of its situation, which has been disturbed by agriculture.
The following table gives an overview of the data of the 19 examined TP sites.
| 1 | Centre | | Edge of Planalto | Flat | Cultivated | 2 | E Estrada 2 | Edge of Planalto | Flat | Previous plantation | 3 | N cemetary | Edge of Planalto | Weak relief | Previous plantation | 4 | Intersection 3 / 4 | Planalto | Weak relief | Plantation | 5 | C.B.A | Planalto spur | Flat | Previous plantation | 6 | Chico Alfredo | Planalto spur | Flat | Previous plantation | 7 | Dourado | Edge of Planalto | Flat | Previous plantation | 8 | Cacoalinho | Edge of Planalto | Undulating | Secondary forest | 9 | Mt.Christo | Edge of Planalto | Flat | Secondary forest | 10 | Santo Antonio | Planalto spur | Flat | Plantation | 11 | São João | Planalto | Undulating | Secondary forest | 12 | São Francisco | Planalto | Flat | Secondary forest | 13 | Water tower | Planalto | Small hill | Plantation | 14 | S Estrada 7 | Planalto | Undulating | Secondary forest | 15 | Castanheiras | Planalto | Undulating | Secondary forest | 16 | Road to Aramanay | Planalto | Flat | Plantation | 17 | Tijucal | Varzea, marshland | Undulating | Primary forest | 18 | Pedreira | Varzea, marshland | Slope | Secundary forest | |
3.5.3 Regular Observations From these representations it can be seen that - with limitations - TP occurrences + are round and the core area with the most intense, i.e. darkest, and strongest developments of an Ah horizon is in the center of the circle. This is also where most of the pottery pieces occur. The ring-shaped transition area to the Latosol often exceeds the actual TP area many times over. However, some heterogeneities were also shown, for example that the rule 'The darker the topsoil, the more pottery is found' also knows exceptions, e.g. the site Cocoalinho (no.8) with the blackest shade, but not above average or v.v. the TP of São Francisco with a lot of pottery, but only a medium intensity. Another, fundamental rule 'The more humus-rich the topsoil, the greater the thickness or (the greater) the entire TP area' finds limiting exceptions, for example in the TP at the water tower (no.13), where a very dark hue finds a very small extension, or in Santo Antonio (no.10) with a very dark black A h on the surface, but a Latosol from ca 50 cm depth. Cum grano salis are nevertheless the above rules on the relation between the humus content of the topsoil, thickness of the TP, size of the site and abundance of fragments based on the field observations. A theory of a potteryless and thus possibly non-anthropogenic TP (see Chap.1.2) can not be verified based on the field observations. No 'potteryless TP' was found. In the vast majority of cases, the TP deposits are integrated flat into the terrain and can therefore not represent a 'plagging' (see Chap.1.2.3). Only in very few cases (nos.3 and 13) do they consist of small, convex hillocks. After the above presentation and consideration of a map (fig.17), it is noticeable that most and most intense TP deposits are located along the escarpment or in its immediate vicinity and the intensity or accumulation of TP deposits decreases with greater accumulation from the slope edge. This can probably be explained by the way the Indians settled, who preferred to settle in places with a wide, all-round sieve(Mayntzhusen 1912, S.462; see Chap.1.2.1). In the 1-3 km wide transitional area of the outgoing TP influence - the whole of Belterra stands on such an area - there are a few more TP 'sub-centres' (e.g. São Francisco) with a stronger expression and abundance of pottery. A hasty and therefore incorrect interpretation of this fact led to Sampaio's mapping of Belterra's TP and the erroneous representation of the 'Terra Mulatta' as its own soil type (< font size=2>1962; Sombroek 1966, p.175; seeChap.1.1.3). This small map is included as a discussion point and for the sake of completeness. However, a critical consideration must be pointed out! The maps drawn by the author (fig.17) should be understood as a correction and specification of the map of Sampaios. Fig.20: Alleged TP distribution in Belterra according to J.B.Sampaio (1962; Sombroek 1966) The influence of the TP on the Latosol humus content over a distance of ca 5 km posed problems in the selection of the Latosol reference plots (seeChap.3.3.7). It has not yet been possible to clarify what causes this influence or whether it is possibly anthropogenic. Based on the detailed pre-survey, one of the 19 TP sites was selected for more detailed analysis. For most of them, the intensity that was too weak (light) and the TP topsoil that was too shallow spoke against it (sites 2-5, 9, 14-18), others were too small in their core area (sites 8, 10, 12, 13). Also, São João (site 11) had to be excluded because of the relatively small size of its core area, the poor accessibility from Belterra and the extremely heavy soil, as did the strongest TP representative (site 1) despite its maximum thickness, humus content and abundance of pottery because of human disturbance (roads, houses, vegetable and gardening, plantations) (field sketch: see Chap.3.8). The TP site Chico Alfredo was therefore chosen, since this is sufficiently humic, deep enough, easily accessible, has a lot of pottery and is outside the former plantation area and is neither used nor disturbed - and thus fulfills all requirements. In order to get at least an impression of another TP site, another profile was made in the 'Belterra / Centre' occurrence (site 1) at a relatively undisturbed location at some distance from the nearest house: SP 9 with a deep black topsoil. However, its values largely correspond to those of Chico Alfredo (profiles SP 1/2/4-8). A further indication gives an insight into the slope dynamics at the beginning of a catena: SP 0, at a distance of 80-100 m W of SP 9 ca 5-6 m below it on the 25-30% inclined slope (see also Chap.3.4.1). The very different dynamics were already apparent when addressing the terrain: its upper horizons were much brighter (value 2-3) than those of the other TP profiles. However, the resulting assumption of a lower humus content was not confirmed by a corresponding analysis (see data volume p.100): An above-average amount of C was even measured (SP0003: 11.6% C). Since such a humus content does not correlate with the relatively low black color of the topsoil, a different color of this soil - and thus a different content of oxides - must be inferred. In fact, when digging deeper at this point (up to 2.10 m), i.e. when the latosolic to lateritic subsoil was reached, the subsoil did not turn light yellow as in the other profiles, but red, and thus an orthic or almost rhodic Ferralsol (see Chap.2.6.1). According to Brazilian soil mapping, this Latosol representative is compared to the yellow 'Latosol Amarelo' that occurs in Belterra and is very dominant in the Brazilian Amazon region as a 'Latosol Vermelho Amarelo' (see fig. 13 in Chap.2.6.3). 3.7.3 Latosol Comparison Sites The aim of this field work and the subsequent analyzes should not only be an exact inventory of the TP, but also the possibility of a comparison between the TP and the original soil type, the latosol, since it is only just beginning to emerge this comparison reveals the different content and dynamics. It is therefore important that the two comparison areas consist of the same substrate (same particle size), are morphologically identical, have the same vegetation, are not too far apart and are at the same altitude. Because of the wide sphere of influence of the TPs (see Chap.3.6), the point of the small distance from each other proved to be impossible. A Latosol comparison area was therefore set up on the extreme edge of the former plantation area (see Chap.3.3) near the Estrada 5 with 10 selected, at a distance to Chico Alfredo of ca 9 km. Because only there was a clear, clayey, yellow Latosol, only weakly humic in the uppermost horizon, found. However, since the entire plateau belongs to the Pliocene Barreiras series (see Chap.2.1.3) and no significant erosion processes have taken place, this relatively large distance could be accepted. To ensure that this Latosol comparison area is not an exception, as well as to obtain a similar number of Latosol and TP profiles, 2 more Latosol profiles were made at other locations created (see also Chap.3.3): SL 6, ca 4.3 km S of Belterras öE of Estrada 4 in plantation terrain that has been in use for a long time and in the weak but still noticeable sphere of influence of the TP (ca 3 km away from the TP location 'C.B.A'), as well as SL 7, ca 6 km S of Belterra outside the former plantation area and TP influence (also outside the 'Terra Mulatta'), in the upper part of a very wide, very shallow depression. The SL 7 profile was primarily intended to assess the influence of the plantation monoculture, which can, however, be neglected: SL 7 does not show any analytical values that deviate from the SL 1-5 profiles in any way. The samples from the profiles SL 1-5 and SL 7 can therefore be considered typical of Latosol, i.e. the anthropogenically unaffected soil type of the local region, the 'initial type of the TP'. SL 6 for estimating the wide transitional area that clearly belongs to Latosol, on the other hand, shows weak transitional characteristics, i.e. slightly higher humus content. The TP site selected for the excavation work and for comparison with the Latosol. Chico Alfredo lies on the exposed spur described above on the NW corner of the Belterra Plateau (seeChap.3.4.1). It juts out ca 500-600 m further to the W than the rest of the plateau edge, but the surface is completely flat. 50-200 m before the end is the center of this TP site with an area of ca 0.65 ha (closely hatched in map fig.21) with the innermost core atProfile SP 1. Both towards the extreme end and towards the beginning of the spur, the top soil darkening and abundance of pottery slowly diminish. Something similar was also observed for the site 'C.B.A.'. Different intensities and thus transition areas can be recognized, such as the area of ca 1.7 ha hatched on the map, but also the entire spur, as shown on this map.It can still be described as a - weaker - TP transition zone. At the escarpment, i.e. in the N and S of the actual core area, the TP character is disappears very quickly. Only a few meters below the edge there is no significant humus content. In the E part of the spur there are 3 smaller huts inhabited by a family. A path leads past these huts to the extreme edge of the spur and from there down to the Tapajos alluvial plain ca 120 m below, where the next drinking water point is located ca 3 km away. In the immediate vicinity of the huts (ca 30 m) there are small vegetable beds. Three older, no longer used shifting cultivation plots with former cassava cultivation are marked on the map. In particular, the one with the profiles SP 5-7 does not seem to have been used for a long time (ca 5-10 years). Fig.21: TP Site Chico Alfredo The vegetation - also in these places - can be described as ca 5-30 year old secondary forest (capoeira). Some larger trees, several meters in diameter, show greater age. Overall, the vegetation is influenced by slash-and-burn agriculture, but is otherwise undisturbed and thus typical of the entire area. After a detailed survey, cartographic recording and creation of dozens of small prospecting profiles in the TP topsoil, a number of test bores were drilled. Important when selecting these spots was a sufficient distance to the next larger trees and to the next impact as well as the undisturbed level position on the spur. If it was located in the inner TP area, i.e. the humus content was high enough, a profile of ca 2 x 1 m ground plan was excavated to a depth of 150-160 cm. Because of the heavy, clayey soil, this was very labour-intensive. In this way, however, a profile wall of ca 6 m in length could be addressed. The distance between these sample drills resulted from the size of the actual center at ca 0.65 ha, not further than 130 m. In some cases, therefore, the profiles had to be created at intervals of only 20-30 m. Another move to the outer areas of this TP site would not have resulted in more distinct TP, but rather transitional types in transition to Latosol. The samples taken from this would no longer have had the meaningfulness necessary for the representation of the TP; statistical validation would have been impossible due to the large variance. The 10 profiles per sample area originally planned for the high level of statistical validation therefore had to be limited to a number of 7 here due to the small-scale nature of the occurrence and compliance with a minimum distance from profile to profile (SP 1 , 2, 4-8) . A total of 16 drills were made as part of the Latosol - TP comparison, which are listed below. In the coding, S stands for Santarém, P for Terra Preta, L for Latosol. The sub-horizons are numbered consecutively; the index numbers in the horizon designations are therefore not to be understood as genetic or descriptive in the sense of the Anglo-Saxon literature (e.g. Soil Survey Staff 1960, p.25f.), i.e. e.g. a A2 not as Eluvial-A horizon! From these 16 chosen pits it was necessary to take typical samples for the horizons. Since a later 'chemical analysis carried out with great effort cannot be better than the sample it represents' (Maxwell 1968, in Herrmann 1975, p. 12), care was always taken in the field to take the samples with greatest care, i.e. to take the samples from characteristic areas, not from above-average light or dark areas, to the greatest possible horizontal distance (often across the entire profile wall of ca 6 m), and to exclude foreign particles that could possibly get into the samples from horizons above. Since horizons in the Latosol are difficult to identify and - with the exception of the A horizon - can only be identified very indistinctly and with broad transition zones (e.g. Soil Survey Staff 1960, p.29), it seemed better to relate soil samples to a specific depth rather than a specific horizon. This sometimes resulted in several samples made from a thick horizon that appears homogeneous in terms of response (e.g. for horizon BA of profile SP 8 at a depth of 36-95 cm with sampling at 40, 60, 80 cm depth). As a result, the sample material is no longer characteristic of a certain horizon, but of a certain depth. This also facilitates the later, quantitative comparison of different profiles at a certain depth. A sample taken in this way should therefore not contain too much material from the area above or below the delivered depth. For a sample from the subsoil, the sampling depth range is ca 3-4 cm, from the topsoil ca 2 cm. On the other hand, where clear diagnostic horizons could be identified, the sampling depths were adjusted to the definition of horizons. It also goes without saying that the gradation of the sample depths in the topsoil was more dense (approx. every 10 cm) than in the subsoil (ca every 20-30 cm). The sample material was removed at the specified depth from all of the profile walls mentioned with a spatula or a knife. The heaviness of the soil, i.e. its high clay content, and the drying out favored this work. In order to prevent material falling from above from 'contaminating' the sample, the three or four profile walls were cut and 'cleaned' a second time after the profile had been addressed. For the same reason, sampling started at the bottom and progressed upwards. The subsequent removal of samples to determine the volume weight was carried out using a round soil sampler with a volume of ca 1 liter specially made in Belem. Its precise determination and correction is shown in Chap.4.2. This cylinder was driven into the undisturbed soil using an overlaid hardwood board in such a way that the sample was not compressed by the impact, loosened by the concussion, or material fell over the top of the cylinder . The structure and the packing density were not allowed to be changed. Depending on the size of the entire ground impact, the cylinder impact occurred in a horizontal or vertical direction. It was then exposed with a pickaxe and knife, and the upper and lower edges were cut off as flatly as possible with sheet metal, so that the volume of the - uncompacted ! - soil exactly matched that of the cylinder. Two samples per horizon were taken to ensure better security of the data material (errors in sampling, inhomogeneities of the horizon, proportions of concretions, roots or pottery remains). When lower horizons occurred and were addressed at greater depths (e.g. B21 and B22), separate volume samples were not always taken, but only those valid for the entire horizon (in this example: for B2). The corresponding assignments are irrelevant for further interpretation, but are nevertheless listed in the data volume, pp.8-41, column 7. The organic topsoil was removed using a square metal frame with a side length of 23.2 cm, i.e. a removal area of 538 cm2. This frame was laid out in the immediate vicinity of the outcrop at three locations that were as undisturbed as possible, in any case not trampled on and not affected by the excavation of the soil, which were marked and estimated before the work began, and the individual humus horizons were collected separately. The decisive factor here was to single out the difference between the fresh litter, the OL horizon, and the mined, bitten, rotten and fungus-covered litter humus, the OF layer. Humification layers could not be found anywhere because of the very high rate of mineralization under these weathering conditions. After the sample had been taken and the material placed in plastic bags labeled with the profile number, sampling depth and purpose of use (plastic strips stamped with the sample number were inserted for security), the samples were taken on windless days from sheltered locations, so that no dust could be blown into the bags, opened and dried in the sun for several days, turning frequently. It was possible to see whether the sample still contained soil water if the airtight sealed bag was heated and then water from the sample condensed and deposited on the inside of the bag. Condensation of this type can be seen as an indication that the sample has not dried sufficiently. Due to the multiple days' drying at 600 - 800, it could be assumed that there was only a very small trace of moisture in the soil. After drying, larger foreign bodies and impurities such as ceramic remains, charcoal, plant parts such as larger roots, pieces of wood and soil animals were sorted out. Ca 250 g of the inorganic samples were packed airtight in plastic bags for shipment to Germany, a further 200 g were made available to EMBRAPA for their research. Of the topsoil samples approx. 80 g were sent to Germany. Also on site, i.e. in Belterra, the volume weight determinations and the necessary drying and weighing were carried out (see Chap.4.2) as well as the individual horizons and TP localities examined and compared with each other for their color intensity. However, this is more precisely obtained by using the Munsell color scale (see Chap.4.10).3.6 Extension of Belterra's TP Complex
3.7 Selection and Concept of Sample Sites
3.8 Sample Site Chico Alfredo and Creation of Profiles3.11 Pre-treatment and Drying of Samples
Last updates: 2007/2022