CO₂ efflux at different zones of the gutter and control soil during four rainfall events.

<p>Solid line + circle represents the eroding zone; dotted line + circle represents the transport zone; solid line + triangle represents the depositional zones; and dotted line + triangle represents control soils. Values are mean± standard error of three replicates.</p

Mean cumulative CO₂ emission at the eroding, transport and depositional zones and control soil.

<p>Different capital letters mean significant difference at a single rainfall event between the different zones. Values are mean± standard error of three replicates.</p

Photographs of the experimental setup and sampling locations along the experimental flume.

<p>It included the eroding, transport and depositional zones of the flume. A shows the lateral view; B shows the vertical view.</p

Afforestation, Natural Secondary Forest or Dehesas? Looking for the Best Post-Abandonment Forest Management for Soil Organic Carbon Accumulation in Mediterranean Mountains

Forest expansion in Mediterranean mountain areas is a widespread phenomenon resulting from the abandonment of agricultural and pastoral activities during the last century. Therefore, knowledge of the long-term storage capacity of soil organic carbon (SOC) in Mediterranean forests is of great interest in the context of global change. However, the effects of these land uses and covers (natural secondary forest, afforestation with conifers and silvo-pastoral ecosystems (dehesas)) on SOC dynamics are still uncertain. The main objectives of this study were to evaluate physico-chemical soil properties, SOC and nitrogen stocks, and SOC fractions in Mediterranean forests and to assess the effects of tree species, the soil environment (acidic and alkaline), and land management. We selected five land uses and land covers: managed and non-managed afforestation and dehesa (except for alkaline dehesa) and a stage of succession when tree species begin to become established after abandonment. This study concludes that although total SOC stocks are higher in afforested systems with conifers, SOC is stored in less stable carbon pools than in broadleaf forests. In addition, this study confirms that there are marked differences in the results between acidic and alkaline environments. Finally, the management system is also a significant factor, particularly for afforested sites

Soil organic C redistribution in three density fractions due to erosion (mass balance approach; C in free light fraction, fPOC; C in occluded light fraction, oPOC; C in heavy fraction, MOC).

<p>Results are given as mean and standard error of three replicates.</p>a<p>. Original soil data were used to exclude any effect of soil erosion.</p>b<p>. Erosion induced formation of fPOC (disruption of aggregates) ΔC (g) = fPOC in depositional zone + fPOC in overland flow- fPOC in source area.</p>c<p>. Erosion-induced breakdown of aggregates (decline in oPOC) ΔC (g) = oPOC in depositional zone+oPOC in overland flow- oPOC in source area.</p

Conceptual diagram illustrating the total carbon budget as affected by soil erosion, transport and deposition in the four months rainfall simulation experiment.

<p>Fluxes were calculated on an annual base (interpolated from the 4-months experiments). The values were expressed as mean values and standard error of three replicates.</p

Basic properties of the loess soil used in the experiment. Results are shown as mean and standard error of three replicates.

a<p>: Soil organic carbon.</p>b<p>: Total nitrogen.</p

Initial soil water contents (m³/m³) before and after pre-wetting before starting the rainfall simulation.

<p>Initial soil water contents (m³/m³) before and after pre-wetting before starting the rainfall simulation.</p

Carbon concentrations and specific carbon fractions of soils and sediments for different zones and events.

<p>C in free light fraction  =  free particulate organic C, fPOC; C in occluded light fraction  =  occluded particulate organic C, oPOC; C in heavy fraction  =  mineral-associated organic C, MOC. Results are shown as mean and standard error of three replicates.</p>a<p>. Carbon concentration of bulk soils (mg C g⁻¹ soil).</p>b<p>. Carbon concentration of the three density fractions fPOC, oPOC and MOC in relation to the total weight of that specific soil fraction (mineral + C parts) (mg C g⁻¹ soil fraction).</p>c<p>. Carbon enrichment ratios, calculated on the basis of mg C soil fraction g⁻¹ soil organic C.</p>d<p>. Relative proportion of MOC (%SOC) in bulk soils, density fractions and sediments of overland flow for the first (Overland flow 1) and fourth rainfall event (Overland flow 4).</p