Erosion in forestland
This section includes 3 studies published in peer review journals:
a) European Study: Assessment of cover changes and soil loss potential (Borrelli et al., 2016, Ecological Indicators): This study present the spatial patterns of forest cover changes in 36 countries and their impact in erosion potential.
b) Case Study in Italy (Borrelli et al, 2014, Applied Geography). This case study performs a risk assessment of human-induced accelerated soil erosion processes in the forestland.
c) Soil Loss in the Italian forest (Borrelli et al, 2016, Catena). High resolution erosion assessment in Italy using RUSLE2015
European Study: Assessment of cover changes and soil loss potential
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Case Study: Italy
The temporary absence of a vegetation cover directly exposes the forest soils to the impacts of rainfall events (Morgan, 2005). This alters the natural water balance of the forestlands increasing the magnitude of down-slope soil mobilization (water soil erosion). The occurrence of accelerated soil erosion processes associated with forest harvesting were found in several European locations including England, Italy among others (Stott et al., 2001). Facing the fact that the forestland and forest soils are among the most valuable and strategically most multifunctional natural assets, the European Union and the United Nations strongly encourage policies targeting the forest resources conservation . The challenge for the immediate future is to assure that the forests meet the various humans needs and, at the same time, to minimize the negative effects of the human interference on the forests (safeguarding forest and soil biodiversity, recreational needs, and ecosystem services). Such ambitious undertaking, however, requires in-depth knowledge about the current status of European forests as an important precondition. An adequate knowledge about forest harvesting districts that are involved in the wood supply chain and related soil erosion processes needs to be archived.
Key Problem and Research Aim
The overall aim of the study is to perform a risk assessment of human-induced accelerated soil erosion processes in the forestland sectors of a test area of the European Union. The selected physiographic unit is Italy, which falls in a Mediterranean region particularly prone to erosion. In Italy, forestland is the second most common type of land use covering about 87,592 km² (29% of the land surface), out of which 42% is currently managed as coppice forest (INFC, 2007). As a result, a vast area of the country, mostly located in mountainous areas characterized by heavy bursts of intensive and erosive rainfalls that hit the steep slopes (van der Knijff et al., 1999), is subject to operations of wood extraction. For some of these forest landscapes this practice of land resource exploitation may result in irremediable damages. To achieve this aim, the spatio-temporal pattern and dynamic changes of the specific soil erosion risks of the Italian forests will be investigated by means of a spatially distributed modeling approach. To enable the modeling phase of soil erosion, initially, the vegetation changes that are the direct cause of the instability in the natural balance and thus responsible for the accelerated erosion process need be carefully mapped.
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Figure 1: Forest change from July 2002 to July 2011. Note that the forest changes (brown) may be enhanced in size because of the small scale of the map.
Figure 2: Forest change area at province level (EU NUTS-3 units)
Soil erosion in the Italian forest. First comprehensive monitoring and modelling approach
As a member of the European Union, Italy has committed to the maintenance and protection of its forests based on sustainable forest development and management practices. According to Eurostat, Italy has the seventh largest forest surface available for wood supply in the EU-28, which is equal to 8.086 million hectares. For 2012, the Italian National Institute of Statistics estimated the total roundwood production of Italy to be 7.7 million m3, from a harvested forest surface of 61,038 hectares. Large parts of the country’s forests, mainly located in vulnerable mountainous landscapes that are highly sensitive to environmental changes, are subject to anthropogenic disturbance driven by wood supply interests. Despite the extensive logging activities and the well-known impacts that such management practices have on the soil-related forest ecosystems, there is a lack of spatially and temporally explicit information about the removal of trees. Hence, this study aims to: i) assess the soil loss by water erosion in Italian forest areas, ii) map forest harvests and iii) evaluate the effects of logging activities in terms of soil loss by means of comprehensive remote sensing and GIS modelling techniques.
The spatio-temporal pattern of rill and inter-rill soil erosion processes in Italian forest lands is based on a spatially distributed modelling approach (Figure 1). Prior to the soil erosion modelling phase, the status of the vegetation and the logged areas were outlined by remote sensing and GIS operations. As a first step, the impact of a 30-year period of forest logging was established based on forest change detection techniques (2002-2011) and a rules-based approach that randomly generated clear-cut areas (1982-2001). As the second step, the long-term soil loss rates (Mg ha-1 y-1) were predicted by means of a revised version of the Universal Soil Loss Equation (USLE).
The study area covers about 785.6·104 ha, which corresponds to the main forest units described within the CORINE land cover 2006 database (EEA, 2014), i.e. broad-leaved forests (547.9·104 ha, 70%), coniferous forests (128.6·104 ha, 17%) and mixed forests (109.1·104 ha, 13%).
The derived high-resolution data regarding forest cover change shows that 317,535 ha (4.04% of the total forest area in Italy) were harvested during the period under review (Figure 2). The predicted long-term annual average soil loss rate was 0.54 Mg ha-1 yr-1 (equal to 67.946 x 103 Mg yr-1) (Figure 3). The average rate of soil loss in forests that remained undisturbed during the modelled period is equal to 0.33 Mg ha-1 yr-1. Notably, about half of the soil loss (45.3%) was predicted for the logged areas, even though these cover only about 10.6% of the Italian forests. The identified erosion hotspots may represent a serious threat for the soil-related forest ecosystems, and are in contrast to the EC Thematic Strategy for Soil Protection and Water Framework Directive.
Figure 1: Workflow — Assessment of vegetation cover, tree harvesting and soil loss potential for the Italian forestland.
Figure 2: Forest harvesting averaged by 2.5 × 2.5 km grid.
Figure 3: Left) Average long-term soil loss potential modelled assuming the absence (L1) and presence (L2) of forest harvesting activities. Right) Post-harvest vegetation development. (a) Landsat false-colour time-series (bands 4/3/2) for the period from Summer 2004 (i) to Summer 2009 (iv) (Path 192 Row 30 — Tuscany). (b) Average Landsat NDVI time-series for 250 clear-cut areas spread across the country. (c) Average MODIS EVI 16-day time-series extracted by the JRC Phenolo model for 510 clear-cut areas spread across the country (the continuous line indicates the moving average). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
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Borrelli, P., Panagos, P., Märker, M., Modugno, S., Schütt, B. 2016. Assessment of the impacts of clear-cutting on soil loss by water erosion in Italian forests: First comprehensive monitoring and modelling approach. CATENA, doi:10.1016/j.catena.2016.02.017
||Title: Soil erosion in forestland in Europe (using RUSLE2015)|
Resource Type: Datasets, Soil Threats Data
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Publisher: European Commission - DG JRC