Los autores agradecen el financiamiento y
apoyo de los proyectos Fondecyt 1050565
y FONDEF D99I 1081.

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Carbono orgánico y propiedades del suelo

Soil organic matter in major pedogenic soil groups

Eucalyptus grandis and Acacia mangium in monoculture and intercropped plantations: Evolution of soil and litter microbial and chemical attributes during early stages of plant development

Changes in soil organic carbon (SOC) stability may alter carbon release from the soil and, consequently, atmospheric CO2 concentration. The mean annual temperature (MAT) can change the soil physico-chemical characteristics and alter the quality and quantity of litter input into the soil that regulate SOC stability. However, the relationship between climate and SOC stability remains unclear. A 500-day incubation experiment was carried out on soils from an 11 °C-gradient mountainous system on Changbai Mountain in northeast China. Soil respiration during the incubation fitted well to a three-pool (labile, intermediate and stable) SOC decomposition model. A correlation analysis revealed that the MAT only influenced the labile carbon pool size and not the SOC stability. The intermediate carbon pool contributed dominantly to cumulative carbon release. The size of the intermediate pool was strongly related to the percentage of sand particle. The decomposition rate of the intermediate pool was negatively related to soil nitrogen availability. Because both soil texture and nitrogen availability are temperature independent, the stability of SOC was not associated with the MAT, but was heavily influenced by the intrinsic processes of SOC formation and the nutrient status.

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Factors controlling soil organic carbon stability along a temperate forest altitudinal gradient.

Natural regeneration may be a cost-effective method for recovering areas previously used for intensive agricultural purposes. Plant diversity in the succession periods has been well documented; however, less attention has been paid to the changes in soil attributes, which may work as an instrument for the validation of regeneration methods. The present study is part of a broader interdisciplinary research project assessing the effects of natural regeneration on biodiversity and the quality of the soil. We investigated the effects of natural regeneration on the physicochemical attributes of the soil, as well as on soil organic carbon (SOC), microbial biomass carbon (MBC) and enzyme attributes. We assessed three stages and five areas of each natural regeneration stage (early-ER, intermediate-IR and late-LR) in two layers: 0–5 and 5–10 cm. The present study found a 20% SOC increase due to natural regeneration. In the first layer, SOC, urease, acid phosphatase and arylsulfatase absolute activities were significantly higher in the two older natural regeneration stages (IR and LR) than those found in the ER stage. We found a reduction in specific enzyme activities per SOC unit in the ER areas. Natural regeneration influenced SOC and MBC, the absolute enzyme activities, and the specific enzymes per SOC unit, mainly in the surface layer. The present study provided some of the first data concerning the beneficial effects of natural regeneration on the quality of soil as measured through enzyme activity, SOC and MBC in a tropical dry region in Northeastern Brazil.

Soil organic carbon, microbial biomass and enzyme activities responses to natural regeneration in a tropical dry region in Northeast Brazil

Carbon and nitrogen enhancement in Cambisols and Vertisols by Acacia spp. in eastern Burkina Faso: Relation to soil respiration and microbial biomass

Acacia communities and species responses to soil and climate gradients in the Sudano-Sahelian zone of West Africa

Savannas are dry tropical biomes characterized by high above- and belowground biomass production, but at the same time there is extensive C loss by fire regimes. Soil-mediated responses are crucial in biogeochemical cycling and the role of soil minerals may be important in controlling organic carbon (OC) storage and stabilization. The objective of this study was to determine OC fractional distribution and saturation capacity in three soil groups (Vertisols, Lixisols, Luvisols) that are characterized by specific and different 1:1 and 2:1 clay mineral dominance. For each soil group, top- and subsoils (0–10 cm, 40–60 cm) were sampled in protected Soudanian savannas across Burkina Faso and fractionated into free and aggregate-occluded particulate organic matter (fPOM, oPOM) and mineral-associated organic matter (mOM). The results showed that oPOM and mOM were significantly affected by soil groups and topsoil/subsoil layers. We consider this to be due to interactions with fine particles (clay, fine and medium silt), the presence of exchangeable Ca and Mg and extractable Al (D) and Fe (D) as revealed by significant positive correlations. We found that oPOM (13–29% of total OC) and mOM

Organic carbon fractional distribution and saturation in tropical soils of West African savannas with contrasting mineral composition

Regeneration success, persistence strategies (seedlings vs. coppicing), and population trend of Acacia spp. were tested under two land-use regimes in eastern Burkina Faso: (i) protected areas shielded to livestock grazing pressure, to logging, and using early annual fire as a management system; (ii) areas with high human impact (heavily and extensive livestock grazing, harvesting for wood and for medicinal plants). Generally, a good regeneration rate of Acacia species was observed in protected areas and a poor regeneration rate in areas with high human impact. Nevertheless, some species affiliated to the subgenus Aculeiferum as A. dudgeoni and A. polyacantha showed a good regeneration under both land use regimes. Juvenile plants less than 25 cm height of A. dudgeoni and A. gourmaensis increased by 116 to 50 % in areas with human impact as compared to their populations in protected areas. With SCD slopes varying from –0.40 to -0.70, the protected Acacia woodland displayed a stable population structure due to abundance of recruitment, and coppicing persistence (more common in the subgenus Aculeiferum) favoured by early annual fire. Consequently, the protected areas are favourable for Acacia woodland regeneration. Conversely, SCD slopes are positive or close to zero in areas of anthropogenic regime and showed a declining population, especially more marked with the subgenus Acacia due to permanent seed and seedling removal by livestock grazing. Nevertheless, the number of seedlings of some species was higher in areas under human pressure than in protected areas, especially for the subgenus Aculeiferum, improving the genetic variability and thus the long-term maintenance of the population

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Impact of Protected Areas and Land Use on Regeneration of Acacia Woodland’s in Eastern Burkina Faso

La prediction spatiale est un outil capital pour la gestion de la biodiversite et l’amenagement des ecosystemes. Au regard de l’importance socio-economique et ecologique des Acacia spp. dans le developpement rural des zones seches (fourrage pour le betail, bois d’energie, production de gomme, rehabilitation des terres degradees), la modelisation spatiale de la distribution de quatre especes soudanosaheliennes (Acacia dudgeoni, Acacia gourmaensis, Acacia hockii et Acacia seyal) a ete realisee dans la region Est du Burkina Faso. Cette modelisation s’est basee sur un echantillonnage de 175 placettes en integrant, comme predicteurs de l’occurrence des especes, les variables environnementales (climat et sol) et geographiques (densite locale, tendance spatiale). Les modeles sont selectionnes et evalues par des methodes de validation croisee en utilisant le programme GRASP (generalized regressions and spatial analysis). L’evaluation des modeles de regression montre des modeles stables et adequats pour les especes A. gourmaensis, A. hockii, avec des correlations de Spearman elevees entre les valeurs predites et observees de la validation croisee (respectivement, 0,72 et 0,84). Le modele de A. seyal montre une autocorrelation significative, et sa prediction spatiale a ete calibree par deux methodes en tenant compte des termes autoregressifs. La prediction spatiale, realisee grâce a une couverture spatiale des predicteurs, montre la distribution potentielle des differentes especes mettant en evidence des zones de forte et de faible occurrence. Ces informations sont necessaires pour la gestion et la mise en valeur de ces ressources forestieres dans un contexte environnemental marque par la forte pression anthropique et le changement climatique.

Lamourdia Thiombiano

Papers

Carbon and nitrogen enhancement in Cambisols and Vertisols by Acacia spp. in eastern Burkina Faso: Relation to soil respiration and microbial biomass

Acacia communities and species responses to soil and climate gradients in the Sudano-Sahelian zone of West Africa

Organic carbon fractional distribution and saturation in tropical soils of West African savannas with contrasting mineral composition

Impact of Protected Areas and Land Use on Regeneration of Acacia Woodland’s in Eastern Burkina Faso

Prédiction spatiale et modélisation de la distribution des Acacia spp. dans l’Est du Burkina Faso