Transformations of natural ecosystems in tropical regions, which are usually covered by high-biom... more Transformations of natural ecosystems in tropical regions, which are usually covered by high-biomass forests, contribute to increased atmospheric CO 2. Much of the carbon in forest ecosystems is stored in the soil. This study estimates soil carbon stock in a dense forest in central Amazonia from sets of soil samples collected in three topographic positions (plateau, slope and valley bottom). Soil organic matter (SOM) was fractionated by density and particle size, thus obtaining the free light fraction (FLF), intra-aggregated light fraction (IALF), sand fraction (F-sand), clay fraction (F-clay) and silt fraction (F-silt). Soil organic carbon (SOC) stocks on the plateaus (Oxisol), slopes (Ul-tisol) and valley bottoms (Spodosol) were 98.4 ± 7.8 Mg·ha −1 , 72.6 ± 5.4 Mg·ha −1 and 81.4 ± 8.9 Mg·ha −1 , respectively. Distribution of carbon in soil fractions was: 112.6 ± 15 Mg·ha −1 (FLF), 2.5 ± 0 Mg·ha −1 (ILAF), 40.5 ± 1.5 Mg·ha −1 (F-silt), 68.5 ± 4.2 Mg·ha −1 (F-clay) and 28.3 ± 1.4 Mg·ha −1 (F-sand), totaling 252.4 ± 22.1 Mg·ha −1 of carbon. Carbon is largely in labile form and near the soil surface, making it liable to release from deforestation or from climate change. Spodosols are more susceptible to soil carbon losses, demonstrating the need to preserve forested areas close to Amazonian rivers and streams.
Intensive sampling of rainfall, soil water and runoff was carried out in a tropical forest on one... more Intensive sampling of rainfall, soil water and runoff was carried out in a tropical forest on one small but highly responsive catchment in French Guiana. A geochemical hydrograph separation, based on 18 0 and hydrochemical tracers, was performed to separate streamflow into subsurface quick flow, mixing zone and groundwater slow flow contributions. Soil water (surface and deep layers) plays a significant role in the streamwater chemistry generation. With a few reasonable assumptions, a two or three-component model accommodating contributions from the different sources can explain the temporal variation of the geochemical tracers observed in the streamflow response.
S . P e r r i n a , M . B o u s s a f i r c , S . G o g o c , M . S a r r a z i n d & M . B r o s... more S . P e r r i n a , M . B o u s s a f i r c , S . G o g o c , M . S a r r a z i n d & M . B r o s s a r d b
... p. 215-221. SAH, RN; MIKKELSEN, DS; HAFEZ, AA 1989. Phosphorus behavior in floodeddrained soi... more ... p. 215-221. SAH, RN; MIKKELSEN, DS; HAFEZ, AA 1989. Phosphorus behavior in floodeddrained soils II: iron transformation and phosphorus sorption. ... Boletim da FCAP, Belém, n. 21, p. 65-75, dez. ZONTA, Elio Paulo; MACHADO, Amauri Almeida. 1991. ...
Palavras-chave: Granulometria. Topossequência. Sistemas pedológicos. Agricultura familiar. Abstra... more Palavras-chave: Granulometria. Topossequência. Sistemas pedológicos. Agricultura familiar. Abstract: The transformations in the Amazonian ecosystems, that occur from colonization process, it have been enough studied, however little have been considering the variations of the characteristics of the soil in the landscape. With the objective of evaluating the variation of the soil of a landscape of the Marabá (PA) region, a study was carried through involving the granulometric and organic composition of the soil. It tries to explain the variation of those characteristics in relationship the pedogenetics processes. The samples were removed of vertical profiles, in the top (Latosols), hillside (Cambisols) and low slope (Gleysols), in a topossequence with 300 m of extension, cultivated with Brachiaria brizantha. The analyses demonstrated the clay prevalence in Latosols and in Cambisols, and of sand in Gleysols, besides an accumulation of organic matter in surface. The increase in the silt...
Boletim do Museu Paraense Emílio Goeldi Ciências Naturais, 2006
... of Eastern Amazonia rontier of Eastern Amazonia Patricia Shanley 1 Nelson A. Rosa 2 Minha mãe... more ... of Eastern Amazonia rontier of Eastern Amazonia Patricia Shanley 1 Nelson A. Rosa 2 Minha mãe usou esta casca; nós não a usamos mais FS Carvalho Brito, filho do curandeiro. Resumo: Em resposta ao declínio na disponibilidade ...
Soil plays an important role in the C cycle, and substitution of tropical forest by cultivated la... more Soil plays an important role in the C cycle, and substitution of tropical forest by cultivated land affects C dynamic and stock. This study was developed in an area of expansion of human settlement in the Eastern Amazon, in Itupiranga, State of Pará, to evaluate the effects of native forest conversion to Brachiaria brizantha pasture on C contents of a dystrophic Oxisol. Soil samples were collected in areas of native forest (NF), of 8 to 10 year old secondary forest (SF), 1 to 2 year old SF (P1-2), 5 to 7 year old SF (P5-7), and of 10 to 12 year old SF (P10-12), and from under pastures, in the layers 0-2, 2-5 and 5-10 cm, to evaluate C levels and stocks and carry out separation of OM based on particle size. After deforestation, soil density increased to a depth of 5 cm, with greater increase in older pastures. Variation in C levels was greatest in the top soil layer; C contents increased with increasing pasture age. In the layers 2-5 and 5-10 cm, C content proved to be stable for the types of plant cover evaluated. Highest C concentrations were found in the silt fraction; however, C contents were highest in the clay fraction, independent of the plant cover. An increase in C associated with the sand fraction in the form of little decomposed organic residues was observed in pastures, confirming greater sensitivity of this fraction to change in soil use.
We examined the effect of plant diversity on plant production and soil macrofauna density and div... more We examined the effect of plant diversity on plant production and soil macrofauna density and diversity. Four plants species (Arachis pintoi, an herbaceous legume; Brachiaria brizantha, a perennial grass; Leucaena leucocephala, a legume shrub; Solanum rugosum, a non-legume shrub) were used in a field experiment and communities of all combinations of one, two, three or four species were established. Plant diversity neither significantly affected density and diversity of soil macrofauna nor total plant biomass, however, the biomass of specific plants was negatively affected by plant diversity. Earthworm and ant densities were significantly higher in the presence of A. pintoi although this plant influenced neither the density of the other group nor fauna diversity. Earthworm and diplopod densities increased significantly with shoot biomass of A. pintoi. Fauna diversity increased significantly with shoot biomass (specific and total). Root biomass did not affect fauna density and diversity. Our results suggest that fauna density is affected by litter quality and that it is more affected by resource quantity than quality. Our results also confirm the importance of nitrogen fixers to ecosystem function.
The functional patterns of microbial communities (microbial respiration, enzyme activities, funct... more The functional patterns of microbial communities (microbial respiration, enzyme activities, functional diversity) and the relevant physico-chemical characteristics of rhizospheric soils were studied during the process of mudflat colonization by mangrove. The study site is a fringe mangrove stand located in Montabo Bay at Cayenne (French Guiana). It is characterized by different vegetation development stages dominated by an assemblage of Avicennia germinans and Laguncularia racemosa. Rhizospheric and surface soils were collected from three stations based on successional stages of mangrove colonization: pioneer (P), coppice (C), and young forest (F). The microbial functional patterns showed significant progressive shifts along the mangrove vegetation profile. The P stages, those most influenced by tide currents, were macroscopically characterized by hydro-sedimentary instability and micro-phytobenthic colonization of mudflat. This stage, characterized by low total organic carbon (TOC) content and quality, showed the lowest extracellular enzymatic activities and the highest functional metabolic diversities. TOC quality analyses by 13 C CPMAS NMR provided evidence of progressive TOC enrichment and an increasing imprint of aboveground vegetation on C quality as succession occurs. These differences in the origin, amount, and quality of soil organic matter (SOM) of older stages exerted both a quantitative and qualitative control over microbial functional responses. This indicated the enhancement of abovegroundbelowground functional linkages, leading to the expression of high decomposition activities and a functional loss and specialization of rhizospheric microbial communities.
Almost all cultivated soils undergo some reduction in the porosity of the surface layers, and now... more Almost all cultivated soils undergo some reduction in the porosity of the surface layers, and nowhere is this more evident than in tropical rainforests that have been converted to pastures. Following deforestation in an area of Costa Rica, soil bulk density has been shown to increase ...
In Brazilian Amazonia there are 26 million hectares of degraded pastures. One of the causes of de... more In Brazilian Amazonia there are 26 million hectares of degraded pastures. One of the causes of degradation is assumed to be alterations in soil structure that is partly determined by a reduction in soil macrofauna diversity. The objective of this case study was to identify the ...
Pontoscolex corethrurus (Glossoscolecidae, Oligochaeta) is an invasive endogeic earthworm that ha... more Pontoscolex corethrurus (Glossoscolecidae, Oligochaeta) is an invasive endogeic earthworm that has colonized most land transformed by human activities in the humid tropics. When installed, populations can change soil physical properties, biogeochemical processes and microbial communities. The aim of this study was to determine whether P. corethrurus establishment is a result of (1) a competitive exclusion of native earthworm species or
Fire-free forest conversion with organic inputs as an alternative to slash-and-burn could improve... more Fire-free forest conversion with organic inputs as an alternative to slash-and-burn could improve agroecosystem sustainability. We assessed soil carbon mass changes in a sandy-clayey and well-drained soil in French Guiana after forest clearing by the chop-and-mulch method and crop establishment. At the experimental site of Combi, native forest was cut down in October 2008; woody biomass was chopped and incorporated into the top 20 cm of soil. After about one year of legume and grass cover, three forms of land management were compared: grassland (Urochloa ruziziensis), maize/soybean crop rotation with disk tillage and in direct seeding without tillage. There were four replicates. We measured 14.16 kg m −2 of carbon in 2 mm-sieved soil down to 2 m depth for the initial forest. Forest clearing did not induce significant soil compaction; neither did any specific agricultural practice. In converted soils, C stocks were measured in the 0-30 cm layer after each crop for three years. Carbon mass changes for soil fractions <2 mm (soil C stock) and >2 mm (soil C pool) in the 0-5, 5-10, 10-20 and 20-30 cm soil layers were assessed on an equivalent soil mass basis. One year and 1.5 years after deforestation, higher C stocks (+0.64 to 1.16 kg C m −2 yr −1 ) and C pools (+0.52 to 0.90 kg C m −2 yr −1 ) were measured in converted soils, compared to those of the forest into the top 30 cm of soil. However, the masses of carbon in these converted soils declined later. The highest rates of carbon decrease were measured between 1.5 and 2 years after forest conversion in the <2 mm soil fraction, from 0.46 kg C m −2 yr −1 (in grassland soils) to 0.71 kg C m −2 yr −1 (in cropland under no tillage). The carbon pool declined during the third year at rates of 0.41 kg C m −2 yr −1 (cropland under disk tillage) to 0.76 kg C m −2 yr −1 (grassland soils). Three years after forest conversion, C masses in the top 30 cm of soils for grassland showed similar values than for forest. In comparison, the carbon stock in cropped soils managed under no tillage in direct seeding (without mulch) was significantly 17% and 16% lower than in forest and grassland soils, respectively. None of the studied agricultural practices succeeded in accumulating carbon from the chopped forest biomass.
Transformations of natural ecosystems in tropical regions, which are usually covered by high-biom... more Transformations of natural ecosystems in tropical regions, which are usually covered by high-biomass forests, contribute to increased atmospheric CO 2. Much of the carbon in forest ecosystems is stored in the soil. This study estimates soil carbon stock in a dense forest in central Amazonia from sets of soil samples collected in three topographic positions (plateau, slope and valley bottom). Soil organic matter (SOM) was fractionated by density and particle size, thus obtaining the free light fraction (FLF), intra-aggregated light fraction (IALF), sand fraction (F-sand), clay fraction (F-clay) and silt fraction (F-silt). Soil organic carbon (SOC) stocks on the plateaus (Oxisol), slopes (Ul-tisol) and valley bottoms (Spodosol) were 98.4 ± 7.8 Mg·ha −1 , 72.6 ± 5.4 Mg·ha −1 and 81.4 ± 8.9 Mg·ha −1 , respectively. Distribution of carbon in soil fractions was: 112.6 ± 15 Mg·ha −1 (FLF), 2.5 ± 0 Mg·ha −1 (ILAF), 40.5 ± 1.5 Mg·ha −1 (F-silt), 68.5 ± 4.2 Mg·ha −1 (F-clay) and 28.3 ± 1.4 Mg·ha −1 (F-sand), totaling 252.4 ± 22.1 Mg·ha −1 of carbon. Carbon is largely in labile form and near the soil surface, making it liable to release from deforestation or from climate change. Spodosols are more susceptible to soil carbon losses, demonstrating the need to preserve forested areas close to Amazonian rivers and streams.
Intensive sampling of rainfall, soil water and runoff was carried out in a tropical forest on one... more Intensive sampling of rainfall, soil water and runoff was carried out in a tropical forest on one small but highly responsive catchment in French Guiana. A geochemical hydrograph separation, based on 18 0 and hydrochemical tracers, was performed to separate streamflow into subsurface quick flow, mixing zone and groundwater slow flow contributions. Soil water (surface and deep layers) plays a significant role in the streamwater chemistry generation. With a few reasonable assumptions, a two or three-component model accommodating contributions from the different sources can explain the temporal variation of the geochemical tracers observed in the streamflow response.
S . P e r r i n a , M . B o u s s a f i r c , S . G o g o c , M . S a r r a z i n d & M . B r o s... more S . P e r r i n a , M . B o u s s a f i r c , S . G o g o c , M . S a r r a z i n d & M . B r o s s a r d b
... p. 215-221. SAH, RN; MIKKELSEN, DS; HAFEZ, AA 1989. Phosphorus behavior in floodeddrained soi... more ... p. 215-221. SAH, RN; MIKKELSEN, DS; HAFEZ, AA 1989. Phosphorus behavior in floodeddrained soils II: iron transformation and phosphorus sorption. ... Boletim da FCAP, Belém, n. 21, p. 65-75, dez. ZONTA, Elio Paulo; MACHADO, Amauri Almeida. 1991. ...
Palavras-chave: Granulometria. Topossequência. Sistemas pedológicos. Agricultura familiar. Abstra... more Palavras-chave: Granulometria. Topossequência. Sistemas pedológicos. Agricultura familiar. Abstract: The transformations in the Amazonian ecosystems, that occur from colonization process, it have been enough studied, however little have been considering the variations of the characteristics of the soil in the landscape. With the objective of evaluating the variation of the soil of a landscape of the Marabá (PA) region, a study was carried through involving the granulometric and organic composition of the soil. It tries to explain the variation of those characteristics in relationship the pedogenetics processes. The samples were removed of vertical profiles, in the top (Latosols), hillside (Cambisols) and low slope (Gleysols), in a topossequence with 300 m of extension, cultivated with Brachiaria brizantha. The analyses demonstrated the clay prevalence in Latosols and in Cambisols, and of sand in Gleysols, besides an accumulation of organic matter in surface. The increase in the silt...
Boletim do Museu Paraense Emílio Goeldi Ciências Naturais, 2006
... of Eastern Amazonia rontier of Eastern Amazonia Patricia Shanley 1 Nelson A. Rosa 2 Minha mãe... more ... of Eastern Amazonia rontier of Eastern Amazonia Patricia Shanley 1 Nelson A. Rosa 2 Minha mãe usou esta casca; nós não a usamos mais FS Carvalho Brito, filho do curandeiro. Resumo: Em resposta ao declínio na disponibilidade ...
Soil plays an important role in the C cycle, and substitution of tropical forest by cultivated la... more Soil plays an important role in the C cycle, and substitution of tropical forest by cultivated land affects C dynamic and stock. This study was developed in an area of expansion of human settlement in the Eastern Amazon, in Itupiranga, State of Pará, to evaluate the effects of native forest conversion to Brachiaria brizantha pasture on C contents of a dystrophic Oxisol. Soil samples were collected in areas of native forest (NF), of 8 to 10 year old secondary forest (SF), 1 to 2 year old SF (P1-2), 5 to 7 year old SF (P5-7), and of 10 to 12 year old SF (P10-12), and from under pastures, in the layers 0-2, 2-5 and 5-10 cm, to evaluate C levels and stocks and carry out separation of OM based on particle size. After deforestation, soil density increased to a depth of 5 cm, with greater increase in older pastures. Variation in C levels was greatest in the top soil layer; C contents increased with increasing pasture age. In the layers 2-5 and 5-10 cm, C content proved to be stable for the types of plant cover evaluated. Highest C concentrations were found in the silt fraction; however, C contents were highest in the clay fraction, independent of the plant cover. An increase in C associated with the sand fraction in the form of little decomposed organic residues was observed in pastures, confirming greater sensitivity of this fraction to change in soil use.
We examined the effect of plant diversity on plant production and soil macrofauna density and div... more We examined the effect of plant diversity on plant production and soil macrofauna density and diversity. Four plants species (Arachis pintoi, an herbaceous legume; Brachiaria brizantha, a perennial grass; Leucaena leucocephala, a legume shrub; Solanum rugosum, a non-legume shrub) were used in a field experiment and communities of all combinations of one, two, three or four species were established. Plant diversity neither significantly affected density and diversity of soil macrofauna nor total plant biomass, however, the biomass of specific plants was negatively affected by plant diversity. Earthworm and ant densities were significantly higher in the presence of A. pintoi although this plant influenced neither the density of the other group nor fauna diversity. Earthworm and diplopod densities increased significantly with shoot biomass of A. pintoi. Fauna diversity increased significantly with shoot biomass (specific and total). Root biomass did not affect fauna density and diversity. Our results suggest that fauna density is affected by litter quality and that it is more affected by resource quantity than quality. Our results also confirm the importance of nitrogen fixers to ecosystem function.
The functional patterns of microbial communities (microbial respiration, enzyme activities, funct... more The functional patterns of microbial communities (microbial respiration, enzyme activities, functional diversity) and the relevant physico-chemical characteristics of rhizospheric soils were studied during the process of mudflat colonization by mangrove. The study site is a fringe mangrove stand located in Montabo Bay at Cayenne (French Guiana). It is characterized by different vegetation development stages dominated by an assemblage of Avicennia germinans and Laguncularia racemosa. Rhizospheric and surface soils were collected from three stations based on successional stages of mangrove colonization: pioneer (P), coppice (C), and young forest (F). The microbial functional patterns showed significant progressive shifts along the mangrove vegetation profile. The P stages, those most influenced by tide currents, were macroscopically characterized by hydro-sedimentary instability and micro-phytobenthic colonization of mudflat. This stage, characterized by low total organic carbon (TOC) content and quality, showed the lowest extracellular enzymatic activities and the highest functional metabolic diversities. TOC quality analyses by 13 C CPMAS NMR provided evidence of progressive TOC enrichment and an increasing imprint of aboveground vegetation on C quality as succession occurs. These differences in the origin, amount, and quality of soil organic matter (SOM) of older stages exerted both a quantitative and qualitative control over microbial functional responses. This indicated the enhancement of abovegroundbelowground functional linkages, leading to the expression of high decomposition activities and a functional loss and specialization of rhizospheric microbial communities.
Almost all cultivated soils undergo some reduction in the porosity of the surface layers, and now... more Almost all cultivated soils undergo some reduction in the porosity of the surface layers, and nowhere is this more evident than in tropical rainforests that have been converted to pastures. Following deforestation in an area of Costa Rica, soil bulk density has been shown to increase ...
In Brazilian Amazonia there are 26 million hectares of degraded pastures. One of the causes of de... more In Brazilian Amazonia there are 26 million hectares of degraded pastures. One of the causes of degradation is assumed to be alterations in soil structure that is partly determined by a reduction in soil macrofauna diversity. The objective of this case study was to identify the ...
Pontoscolex corethrurus (Glossoscolecidae, Oligochaeta) is an invasive endogeic earthworm that ha... more Pontoscolex corethrurus (Glossoscolecidae, Oligochaeta) is an invasive endogeic earthworm that has colonized most land transformed by human activities in the humid tropics. When installed, populations can change soil physical properties, biogeochemical processes and microbial communities. The aim of this study was to determine whether P. corethrurus establishment is a result of (1) a competitive exclusion of native earthworm species or
Fire-free forest conversion with organic inputs as an alternative to slash-and-burn could improve... more Fire-free forest conversion with organic inputs as an alternative to slash-and-burn could improve agroecosystem sustainability. We assessed soil carbon mass changes in a sandy-clayey and well-drained soil in French Guiana after forest clearing by the chop-and-mulch method and crop establishment. At the experimental site of Combi, native forest was cut down in October 2008; woody biomass was chopped and incorporated into the top 20 cm of soil. After about one year of legume and grass cover, three forms of land management were compared: grassland (Urochloa ruziziensis), maize/soybean crop rotation with disk tillage and in direct seeding without tillage. There were four replicates. We measured 14.16 kg m −2 of carbon in 2 mm-sieved soil down to 2 m depth for the initial forest. Forest clearing did not induce significant soil compaction; neither did any specific agricultural practice. In converted soils, C stocks were measured in the 0-30 cm layer after each crop for three years. Carbon mass changes for soil fractions <2 mm (soil C stock) and >2 mm (soil C pool) in the 0-5, 5-10, 10-20 and 20-30 cm soil layers were assessed on an equivalent soil mass basis. One year and 1.5 years after deforestation, higher C stocks (+0.64 to 1.16 kg C m −2 yr −1 ) and C pools (+0.52 to 0.90 kg C m −2 yr −1 ) were measured in converted soils, compared to those of the forest into the top 30 cm of soil. However, the masses of carbon in these converted soils declined later. The highest rates of carbon decrease were measured between 1.5 and 2 years after forest conversion in the <2 mm soil fraction, from 0.46 kg C m −2 yr −1 (in grassland soils) to 0.71 kg C m −2 yr −1 (in cropland under no tillage). The carbon pool declined during the third year at rates of 0.41 kg C m −2 yr −1 (cropland under disk tillage) to 0.76 kg C m −2 yr −1 (grassland soils). Three years after forest conversion, C masses in the top 30 cm of soils for grassland showed similar values than for forest. In comparison, the carbon stock in cropped soils managed under no tillage in direct seeding (without mulch) was significantly 17% and 16% lower than in forest and grassland soils, respectively. None of the studied agricultural practices succeeded in accumulating carbon from the chopped forest biomass.
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