Variation of soil organic carbon, stable isotopes, and soil quality indicators across an erosion–deposition catena in a historical Spanish olive orchard
oleh: J. A. Gómez, G. Guzmán, A. Toloza, C. Resch, R. García-Ruíz, L. Mabit
| Format: | Article |
|---|---|
| Diterbitkan: | Copernicus Publications 2020-05-01 |
Deskripsi
<p>This study compares the distribution of bulk soil organic carbon (SOC), its fractions (unprotected and physically, chemically, and biochemically protected), available phosphorus (P<span class="inline-formula"><sub>avail</sub></span>), organic nitrogen (N<span class="inline-formula"><sub>org</sub></span>), and stable isotope (<span class="inline-formula"><i>δ</i><sup>15</sup></span>N and <span class="inline-formula"><i>δ</i><sup>13</sup></span>C) signatures at four soil depths (0–10, 10–20, 20–30, and 30–40 cm) between a nearby open forest reference area and a historical olive orchard (established in 1856) located in southern Spain. In addition, these soil properties, as well as water stable aggregates (<span class="inline-formula"><i>W</i><sub>sagg</sub></span>), were contrasted at eroding and deposition areas within the olive orchard, previously determined using <span class="inline-formula"><sup>137</sup></span>Cs. SOC stock in the olive orchard (about 40 t C ha<span class="inline-formula"><sup>−1</sup></span>) was only 25 % of that in the forested area (about 160 t C ha<span class="inline-formula"><sup>−1</sup></span>) in the upper 40 cm of soil, and the reduction was especially severe in the unprotected organic carbon. The reference and the orchard soils also showed significant differences in the <span class="inline-formula"><i>δ</i><sup>13</sup></span>C and <span class="inline-formula"><i>δ</i><sup>15</sup></span>N signals, likely due to the different vegetation composition and N dynamics in both areas. Soil properties along a catena, from erosion to deposition areas within the old olive orchard, showed large differences. Soil C<span class="inline-formula"><sub>org</sub></span>, P<span class="inline-formula"><sub>avail</sub></span> and N<span class="inline-formula"><sub>org</sub></span> content, and <span class="inline-formula"><i>δ</i><sup>15</sup></span>N at the deposition were significantly higher than those of the erosion area, defining two distinct areas with a different soil quality status. These overall results indicate that the proper understanding of C<span class="inline-formula"><sub>org</sub></span> content and soil quality in olive orchards requires the consideration of the spatial variability induced by erosion–deposition processes for a convenient appraisal at the farm scale.</p>