Wind erosion in Moroccan argan woodlands under extensive agro-silvo-pastoral management

<p>The Moroccan argan woodlands form a unique ecosystem that is at acute risk of degradation and desertification. Beside the great impact on local and regional socio-economical structure, the characteristic landscape is assumed to protect populated and agriculturally productive areas such as the Souss-Massa-region against desertification processes from the adjacent desert areas in Southwest Morocco and Algeria.</p><p>The experimental-empirical study with the Trier Portable Wind Simulator was conducted to quantify sediment mobilisation by wind on various surface characteristics associated to argan woodlands under extensive agro-silvo-pastoral management. Tested surfaces included physical and biological crusts, stone and litter cover and ploughed surfaces.</p><p>We found that the argan woodlands of the Souss region may be a significant source of wind eroded sediment particularly facing effects of overexploitation and climate change. An adapted land management is key to prevent severe dust production and mitigate possible impacts of land use change and climate change related shifts in wind and rainfall patterns.  </p>

Assessing hillslope-channel connectivity in an agricultural catchment using rare-earth oxide tracers and random forests models

Soil erosion from agricultural areas is a large problem, because of off-site effects like the rapid filling of reservoirs. To mitigate the problem of sediments from agricultural areas reaching the channel, reservoirs and other surface waters, it is important to understand hillslope-channel connectivity and catchment connectivity. To determine the functioning of hillslope-channel connectivity and the continuation of transport of these sediments in the channel, it is necessary to obtain data on sediment transport from the hillslopes to the channels. Simultaneously, the factors that influence sediment export out of the catchment need to be studied. For measuring hillslope-channel sediment connectivity, Rare-Earth Oxide (REO) tracers were applied to a hillslope in an agricultural catchment in Navarre, Spain, preceding the winter of 2014-2015. The results showed that during the winter no sediment transport from the hillslope to the channel was detected.To test the implication of the REO results at the catchment scale, two contrasting conceptual models for sediment connectivity were assessed using a Random Forest (RF) machine learning method. The RF method was applied using a 15-year period of measured sediment output at the catchment scale. One model proposes that small events provide sediment for large events, while the other proposes that only large events cause sediment detachment and small events subsequently remove these sediments from near and in the channel. For sediment yield prediction of small events, variables related to large preceding events were the most important. The model for large events underperformed and, therefore, we could not draw any immediate conclusions whether small events influence the amount of sediment exported during large events. Both REO tracers and RF method showed that low intensity events do not contribute any sediments from the hillslopes to the channel in the Latxaga catchment. Sediment dynamics are dominated by sediment mobilisation during large (high intensity) events. Sediments are for a large part exported during those events, but the system shows a memory of the occurrence of these large events, suggesting that large amounts of sediments are deposited in and near the channel after these events. These sediments are gradually removed by small events. To better understand the delivery of sediments to the channel and how large and small events influence each other more field data on hillslope-channel connectivity and within-channel sediment dynamics is necessary.