What are my land use options

in these soils?

CROPS AND TERRA ROXA

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

None 1-25% 26-50% 51-75% 76-99% 100%

Terra Roxa (%)

Cro

ps (%

)

Pasture (%)Cocoa and Sugar Cane (%)Other (%)

Source: Survey in Altamira 1998, N=402 Household

Figure 12

Collaborating Institutions

• Anthropological Center for Training and Research on

Global Environmental Change, Indiana University

• Remote Sensing Laboratory, Dept. of Geography,

Indiana State University

• Instituto Nacional de Pesquisas Espaciais (INPE),

Brazil

• Empresa Brasileira de Pesquisa Agropecuaria

(EMBRAPA), Brazil

Study Site: Altamira

Characteristics of the Study Site • Altamira grew from a small riverine town based on

rubber collection into a booming town of 85,000 due to

agropastoral production stimulated by the Transamazon

Highway built in 1971

• It has one of the most significant patches of alfisols, or

terra roxa estruturada eutrofica, in the Brazilian

Amazon

• Rainfall is about 2000 mm/yr

• Matas de cipo co-exist with dense tropical forest in the

region.

Human Population Characteristics

• About 30% of the population are long-term area

residents, known as caboclos; another 30% came from

the South as colonos; about 20% came from the

Northeast; about 20% came from the Central West

• About 21% had experience with bank credit

• About 20% were previous owners of land before

migrating to the region

• Nutrient-rich soils (alfisols) are associated with greater

overstory basal area

• Nutrient-poor soils (oxisols) are associated with greater

understory development

• But total basal area is similar

Basal Area and Soil Fertility

In comparing Altamira with other study areas we found that:

• The best discriminator of rate of secondary succession was height increment

• That the nutrient-rich site consistently had faster

height increment

• And that the difference accelerates through time

Inter-regional Comparison

• On arrival, most colonists did not recognize differences between alfisols

and oxisols

• Over the past 25 years, colonists have learned the differences and today

there is a clear association between the percentage of the property in

alfisols and crop choice (see figure above on crops and terra roxa)

• However, crop choice is constrained by the initial decision to locate on a

specific property

• Those who arrived early to the frontier acquired most of the plots with terra

roxa– and these plots have not been resold as often as poor quality property

(see table)

Choosing and Using Soils

CHOOSING TERRA ROXA BY COHORT*

% terra roxa Before 1971 1971-75 1976-80 1981-85 After 1985 TotalNone 6.25 38.82 62.69 62.12 72.62 59.451-25% 6.25 10.59 14.93 19.7 13.1 13.6826-50% 62.5 10.59 7.46 12.12 1.79 8.7151-75% 18.75 7.06 4.48 3.03 5.95 5.9776-99% 6.25 12.94 2.99 1.52 5.36 5.97100% 0.00 20.00 7.46 1.52 1.19 6.22Total 100.00 100.00 100.00 100.00 100.00 100.00*cohort is based on the year of arrival in the lot

Source: Survey in Altamira 1998, N=402 households

• Differences in soil quality explain important differences

in rates of secondary succession across regions.

• Differences in soil quality are associated with differences

in species composition in regrowing forests

• Differences in soil quality explain much of the variance in

crop choice and farmer persistence on rural properties

Discussion

• There is an urgent need to give priority to soil quality

assessment in advance of the construction of roads and

settlement of colonists

• Doing so will reduce the high environmental and social

costs resulting from uncritical clearing of land on poor

soils that leads to farm failures, loan defaults, and loss of

forest biodiversity – without benefit to the nation or local

populations.

Conclusion

WHAT DIFFERENCE DOES SOIL QUALITY MAKE?INTER- AND INTRA-SITE COMPARISONS ON HOW AMAZONIAN SOILS AFFECT LAND COVER TRAJECTORIES, CROP CHOICE, AND LAND TENURE

Emilio F. MoranIndiana University / ACT, USA

Contact: moran@indiana.edu