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Effects of forest slash and burn on the distribution of trace elements in floodplain sediments and mountain soils of the Subandean Amazon, Peru
Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.ORCID iD: 0000-0002-3585-2209
Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
2010 (English)In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 25, no 8, 1097-1106 p.Article in journal (Refereed) Published
Abstract [en]

Forest clearing through slash and burn to open up agricultural land is an ongoing process in large parts of the Amazon Basin. This activity severely affects the structure and balance of the natural ecosystem, and also has the potential to cause substantial changes in landscape geochemistry. The latter is the topic of this study, with special attention on translocation of potentially toxic trace elements from deforested areas to downstream aquatic and terrestrial systems. Sampling of floodplain sediments and mountain soils (Inceptisols on redbed lithologies) was carried out in two adjacent Subandean river basins, with deforestation extents of ca. 1/3 and 2/3 of the basin areas. Several 'toxic and potentially toxic metals (e.g., Hg, Cd, Pb, Cu and Ni) and other major and minor elements showed concentration peaks at certain depths in the alluvial deposits of both basins. These peaks were associated with organic matter, and occurred just below layers of combustion residues originating from burning of in situ biomass. Downward migration of particles originating in the combustion residues is suggested to be the direct mechanisms of the metal enrichments. Further evidence of an in situ origin of the metal peaks in the sediments was provided by the geochemical composition of soils located upstream of the floodplains. Disturbed soils (i.e. soils of pasture, coffee plantations, secondary forest and recently swidden fields) were found to be similar to soils under natural forest. Moreover, trace element concentrations in floodplain deposits were similar in the two drainage basins despite the large difference in exploitation degree. Thus, no evidence was found of large scale (basin-wide) increases in trace-metal leaching or translocation as a result of the extensive deforestation and agricultural land-use that has been practiced in the Amazonian highland jungle over more than 100 a.

Place, publisher, year, edition, pages
2010. Vol. 25, no 8, 1097-1106 p.
National Category
Environmental Sciences
Research subject
Natural Science, Environmental Science
Identifiers
URN: urn:nbn:se:lnu:diva-7201DOI: 10.1016/j.apgeochem.2010.04.014OAI: oai:DiVA.org:lnu-7201DiVA: diva2:343475
Available from: 2010-08-13 Created: 2010-08-13 Last updated: 2016-10-05Bibliographically approved
In thesis
1. Environmental Effects of Agricultural Expansion in the Upper Amazon: A study of river basin geochemistry and hydrochemistry, and farmers' perceptions
Open this publication in new window or tab >>Environmental Effects of Agricultural Expansion in the Upper Amazon: A study of river basin geochemistry and hydrochemistry, and farmers' perceptions
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis natural science is combined with environmental psychology in order to determine how deforestation and subsequent agricultural expansion in the Peruvian highland jungle has affected the natural environment and rural livelihoods. This region is part of one of the most biodiverse areas on Earth and is also exposed to high pressure from deforestation that threatens the ecosystems as well as the well-being of local populations. The problem stretches beyond the upper Amazon since the region constitutes headwaters to theAmazon Riverand is part of the most important forest ecosystem of the world.

This study evaluates the relative controls of human induced land-cover change and natural factors on the chemical status of soils, stream waters, and sediments, mainly through a spatial sampling design. The field work was located to two adjacent river basins underlain by sedimentary rocks. Streams of 48 independent sub-basins, the two main rivers, 80 upland soil sites (weakly developed soils on sandstone and siltstone) and four vertical profiles of floodplain sediments were sampled and analysed for major and trace elements, including nutrients and potentially toxic metals. Further, perceptions of environmental changes were investigated through a combination of quantitative and qualitative interview data collected from 51 smallholder farmers.

Soils of primary forests were found to be chemically similar to those of regenerated forests and agricultural land-covers (pastures and coffee plantations), and differences in chemical concentrations between streams draining areas to varying degrees covered by forest were assigned to natural variability. In addition, the chemical composition of alluvial deposits was similar in the two drainage basins despite a substantial difference in exploitation degree (30 % versus 70 % cleared from forest). Thus, no evidence was found of long-term changes in the geochemistry of the Subandean river basins as a result of the conversion of primary forest to agricultural land-uses. The farmers, however, perceived an overall increase in environmental degradation as well as a change towards drier and warmer climatic conditions. The climate change was reported to be the main factor responsible for a negative trend in life quality (rural livelihoods). The results may be used in the work of identifying priorities and key factors necessary for environmental and socioeconomic sustainability in the upper Amazon.

 

Abstract [es]

En esta tesis se combina la ciencia natural con la psicología ambiental con el fin de determinar como la ampliación de la frontera agrícola ha afectado el medio ambiente y los medios de vida en la selva alta del Perú. Esta región forma parte de una de las zonas con mayor biodiversidad en el planeta y a su vez está expuesta a una alta presión de la deforestación que amenaza a los ecosistemas, así como el bienestar de la población en esta zona. Así mismo, este problema se hace sentir mas allá de la selva alta ya que esta zona forma parte de las cabeceras del río Amazonas y pertenece al ecosistema forestal más importante del mundo.

Este estudio evalúa los efectos de la agricultura de tala y quema, en comparación con los factores naturales, sobre las propiedades químicas de los suelos, las quebradas, y los sedimentos, principalmente a través de un diseño de muestreo espacial. El trabajo de campo se realizó en dos cuencas fluviales adyacentes que están compuestas por rocas sedimentarias. Quebradas de 48 sub-cuencas independientes, dos ríos principales, 80 localidades de suelo (poco desarrollados sobre areniscas y limolitas) y cuatro perfiles verticales de sedimentos fluviales fueron muestreados y analizados para los elementos mayores y menores, incluyendo nutrientes y metales potencialmente tóxicos. También se han investigado las percepciones sobre los cambios ambientales usando una combinación de datos cuantitativos y cualitativos, recopilados a través de entrevistas a 51 agricultores.

Según los resultados no hubo diferencias significativas entre la química de suelos de bosques primarios y tierras agrícolas (pastos, plantaciones de café y de bosques secundarios). En cuanto a las quebradas, las diferencias en las concentraciones de sustancias químicas entre sub-cuencas afectadas por la deforestación en diferentes grados fueron asignados a una variabilidad natural. Además, la composición química de los depósitos aluviales fue similar en las dos cuencas a pesar de una diferencia sustancial en el grado de explotación (30 % en comparación con 70 % deforestado). Por lo tanto, no se encontró evidencia de cambios persistentes en la geoquímica de las cuencas Subandinas como resultado de la conversión de bosques a tierras agrícolas. Sin embargo los agricultores percibieron una tendencia general de aumento de la degradación del medio ambiente, así como un cambio en el clima a condiciones más secas y cálidas, lo cual fue reportado como el principal factor responsable de un cambio negativo en la calidad de vida. Estos resultados pueden ser utilizados en el trabajo de identificación de prioridades y factores claves para la sostenibilidad ambiental y socioeconómica en la selva alta.

 

Place, publisher, year, edition, pages
Växjö, Kalmar: Linnaeus University Press, 2011. 92 p.
Series
Linnaeus University Dissertations
Keyword
tropical humid forest, deforestation, land-use change, slash-and-burn agriculture, spatial variation, vertical distribution, multielement analysis, sustainable development, rural livelihoods, bosque húmedo tropical, deforestación, cambios de uso de la tierra, agricultura de tala y quema, variabilidad espacial, distribución vertical, análisis multielemental, desarrollo sostenible, cambio climático, sustentos rurales
National Category
Natural Sciences
Research subject
Natural Science, Environmental Science
Identifiers
urn:nbn:se:lnu:diva-14713 (URN)978-91-86983-05-5 (ISBN)
Public defence
2011-10-21, Fullriggaren, Sjöfartskolan, Kalmar, 09:30 (English)
Opponent
Supervisors
Available from: 2011-10-05 Created: 2011-10-05 Last updated: 2013-03-18Bibliographically approved

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