Soil loss and run-off in young forest stands as affected by site preparation technique: a study in NE Portugal

Abstract

Soil loss rates currently recorded in forests are very low. Nevertheless, that may not be the case during stand installation and early tree growth stage, when soil is disturbed and scarcely covered. Site preparation techniques, performed to improve soil conditions for plant growth, should help reducing this erosion potential. In this study, several site preparation techniques were applied prior to installing a mixed stand (Pseudotsuga mensiezii and Castanea sativa) and a subsequent monitoring scheme of run-off and soil loss ran for 2 years in order to compare their effectiveness for erosion control. The experimental area, near Macedo de Cavaleiros, NE Portugal, at 700 m elevation, with annual means of 656 mm rainfall and 12°C temperature, has Mediterranean climatic conditions. Experimental design comprised three blocks, corresponding to different topographical positions (near flat plateau, moderate slope shoulder and steep mid-slope), where eight treatments were randomly distributed in plots with 375 m 2 area: (1) Original soil control (no intervention on the original abandoned field); (2) No subsoiling, no ploughing, plantation with hole digger; (3) Subsoiling over the whole area, with covering shovel; (4) No subsoiling, contour bunds shaped by two plough passes; (5) Subsoiling in future plantation rows, contour bunds shaped by two plough passes; (6) Subsoiling over the whole area, contour bunds shaped by two plough passes; (7) Subsoiling over the whole area, contour ploughing over the whole area; and (8) Potential erosion (subsoiling over the whole area, ploughing downhill). Sediment and water exported from small plots (2.5 m 2 average area), two replicates per treatment and block, were collected after each rainfall erosion event, in a total of 21, summing 1,876-mm precipitation in 2 years. Mean annual run-off and soil loss in the original soil were 3.4 mm and 11.6 g m -2 , respectively. In treatments 2-7, values were higher 3-7 times, for run-off, and 5-12 times, for soil loss. Potential erosion averages 2.3 t ha -1 year -1 . Soil loss and run-off tend to increase with tillage intensity associated with site preparation technique, even though average two-year losses, in all cases, are below tolerable rates. Soil loss and run-off rates decreased with time, becoming globally negligible after 2 years. Slight and moderate soil disturbance intensity site preparation techniques reduce erosion rates to 30% of potential erosion, halving the critical period when above tolerance rates may occur.

Effect of prescribed fire on soil properties and soil erosion in a Mediterranean mountain area

“…In addition, other factors not explored in the analysis of the results may be contributing to low soil loss as the case of the high soil stoniness in the area, a situation similar to that of other areas studied by the authors in the NE of Portugal (Figueiredo, 2001;Figueiredo et al, 2012). The temporal evolution of soil loss and runoff follows an already known pattern, experimentally verified in areas of bare or sparsely vegetated soil .…”

Ecosystem Services from Small Forest Patches in Agricultural Landscapes

“…Soil loss is generally more than an order of magnitude lower in forests than on arable land [160]. In managed forests, heavy forestry vehicles and mechanical operations associated with logging, as well as clearcutting practises cause important disturbances of the upper soil layers and ground vegetation, thus expose these areas to water run-off and soil erosion [161]. Since SFP are usually less intensively managed, the terrain they cover would be less prone to soil loss and run-off.…”

Post-fire soil erosion mitigation: a review of the last research and techniques developed in Portugal

“…In fact, Martins et al (2013) have measured median soil erosion rates as high as 12-36 Mg ha -1 during the first year after terracing in a recently burnt area. , Ferreira et al (1997), Figueiredo et al (2011, Shakesby et al (1994), Prats et al (2012Prats et al ( , 2013Prats et al ( , 2014 and Malvar et al (2013).…”