Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8893856 | Geoderma | 2019 | 15 Pages |
Abstract
Imperata grassland soils are widely perceived as having poor physical and chemical properties that render them unproductive and prone to erosion. They are therefore increasingly targeted for reforestation across the tropics. To better understand how reforestation and forest growth affect soil hydrological processes we compared the soil physical characteristics for an Imperata grassland and a 23-year-old 'reforest' on Leyte Island, the Philippines. Saturated hydraulic conductivity (Ksat) was determined in the field (Amoozemeter, 20-90â¯cm depth) and the laboratory (small-core permeametry). Core-based values of Ksat were (much) lower than field-based values, suggesting macropores were not sampled adequately with the small cores. Ksat decreased exponentially with depth in both land-cover types, with a median field-measured Ksat of the grassland of 2.1â¯mmâ¯hâ1 at the surface and 2.9â¯mmâ¯hâ1 at 20-40â¯cm depth, declining to â¤1â¯mmâ¯hâ1 below 60â¯cm. Corresponding values for the reforest were 59 (at 20â¯cm), 37 (at 40â¯cm) and 7.3â¯mmâ¯hâ1 (at 60-100â¯cm depth). Reforest Ksat-values down to 60â¯cm depth were significantly higher than corresponding values in the grassland, but the difference disappeared at 90â¯cm depth. Organic carbon content in the top 40â¯cm of soil was slightly higher in the reforest than the grassland. Bulk density was higher and porosity marginally lower in the grassland than the reforest at all depths considered. The median five-min rainfall intensity (June 2013-May 2014) was 3.2â¯mmâ¯hâ1, suggesting that >50% of the rainfall might generate Hortonian overland flow in the grassland. Overland flow is unlikely in the reforest where lateral flow is likely to be generated around 60â¯cm depth for ~30% of rain-time, versus 2-3% between 20 and 60â¯cm. Within the limitations of the space-for-time substitution approach, these results suggest that 23â¯years of forest development at Manobo had a positive effect on hillslope hydrological functioning.
Keywords
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Earth-Surface Processes
Authors
Jun Zhang, L. Adrian Bruijnzeel, Cecille Marie Quiñones, Roger Tripoli, Victor B. Asio, H.J. (Ilja),