The importance of extreme events in controlling erosion and sediment transport in semi-arid areas has long been appreciated but in practice being by definition rare and episodic they are difficult to study. When they are observed this is frequently in catchments for which little data are available. Another difficulty is that even when catchments are being monitored the instruments that record discharge, sediment load and hillslope sediment fluxes perform inaccurately or unpredictably during extreme weather conditions. This paper describes slope and channel processes that were actually observed by the authors during a (at least) 1 : 30 year 30 minute event with a rainfall intensity of 240 mm h 1 in a second-order tributary of the Rio Camacho near Tarija in southern Bolivia. During the event, it could be observed how different tributary streams and slope sections contributed sediments and flow to the main channel. Evidence for these contributions did not survive the event, which has implications for both modelling and monitoring. Before the onset of the event open erosion plots were functioning on the slopes where rainfall and runoff were being measured. Rainfall experiments were used to obtain infiltration rates.The storm began with a moderate intensity of about 5 cm per hour but increased after 5 minutes to 30 cm per hour and continued for 30 minutes. At this time, the rainfall intensity greatly exceeded the infiltration capacity and water started draining the steep slopes. The ephemeral channel rapidly filled up with runoff. Erosion by hailstones was considerable.Provisionally, the discharge during peak runoff was estimated at 43Ð7 m 3 s 1 (Manning equation). On the basis of sediment loads carried by previous storms, (average concentration of 21 g l 1 ) the total suspended load discharge during the storm would have been 15 ton ha 1 . Within the ephemeral channel, 10 to 50 cm thick layers of coarse sediments were deposited. The collectors of the open erosion plots could not handle the large amounts of runoff and sediment and were completely filled to overflowing.Comparing these data with soil losses during less intense storms it can be concluded that extreme events largely contribute to erosion and sediment transport and that the majority of the rainstorms play only a minor role. The results also show how limited the values of rainfall experiments are in understanding geomorphic events. This makes modelling of erosion and soil losses a difficult and hazardous task.

BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

[1] Timber harvesting by clear cutting is known to impose environmental impacts, including severe disturbance of the soil hydraulic properties which intensify the frequency and magnitude of surface runoff and soil erosion. However, it remains unanswered if harvest areas act as sources or sinks for runoff and soil erosion and whether such behavior operates in a steady state or evolves through time. For this purpose, 92 small-scale rainfall simulations of different intensities were carried out under pine plantation conditions and on two clear-cut harvest areas of different age. Nonparametrical Random Forest statistical models were set up to quantify the impact of environmental variables on the hydrological and erosion response. Regardless of the applied rainfall intensity, runoff always initiated first and yielded most under plantation cover. Counter to expectations, infiltration rates increased after logging activities. Once a threshold rainfall intensity of 20 mm/h was exceeded, the younger harvest area started to act as a source for both runoff and erosion after connectivity was established, whereas it remained a sink under lower applied rainfall intensities. The results suggest that the impact of microtopography on surface runoff connectivity and water-repellent properties of the topsoil act as first-order controls for the hydrological and erosion processes in such environments. Fast rainfall-runoff response, sediment-discharge-hystereses, and enhanced postlogging groundwater recharge at catchment scale support our interpretation. At the end, we show the need to account for nonstationary hydrological and erosional behavior of harvest areas, a fact previously unappreciated in predictive models.Citation: Mohr, C. H., R. Coppus, A. Iroume´, A. Huber, and A. Bronstert (2013), Runoff generation and soil erosion processes after clear cutting,

Land degradation is a globally recognized problem and restoration of degraded land is currently high on the international agenda. Forest landscape restoration and other restorative ecosystem management activities are important measures that contribute towards reaching the objectives of the Bonn Challenge, which aims to restore 350 million hectares by 2030. In this context, many restoration projects are being planned and implemented in Latin America and the Caribbean (LAC). We present an overview of the location, goals and activities, and an estimated climate change mitigation potential of 154 recent, ongoing and planned restoration projects in LAC. Our analysis suggests that most projects are located in the humid tropics and less attention is paid to drylands. Increasing vegetation cover, biodiversity recovery and recovery of ecological processes are the most common goals. Restorative activities to fulfil these goals were diverse and were related to the type and source of funding that projects receive. For example, projects implemented through the Forest Investment Program (FIP) and the Global Environment Facility (GEF) generally rely on natural or assisted regeneration over large areas (>20,000 ha), whereas Clean Development Mechanism (CDM) projects establish forest plantations, often including exotic monocultures, in smaller project areas (<5000 ha). Projects that are specifically implemented within the scope of Initiative 20 × 20 and other local initiatives that target the local environmental problems, are more varied and rely on a wider portfolio of restorative activities, such as erosion control, exclusion of grazing and mixed plantations. These projects are usually implemented in smaller project areas (<5000 ha). All projects had the potential to contribute to climate change mitigation by storing additional forest aboveground biomass through natural regeneration, assisted regeneration or establishing a plantation. Further analysis of the implemented activities is an important next step to investigate their effectiveness in terms of goals achieved under Initiative 20 × 20 and the Bonn Challenge. This would provide information for future restoration projects and upscaling of restorative activities in a wider area.

Restoring degraded lands is high on the international agenda and the number of restoration projects in Latin America and the Caribbean (LAC) has increased considerably over the past decades. However, the variety of approaches used have not been systematically documented and analyzed. We aimed to develop a restoration typology as a function of the geographical and socio-economical setting, planning, timeframe, finances, implementation, monitoring and potential impact, which will help to discern broad patterns and identify gaps in project implementation in LAC. We categorized 97 restoration projects using Multiple Correspondence Analysis and a Hierarchical Clustering on Principal Components. Three main restoration types emerged from the clustering, with the main defining variables being: (1) project area under restoration, (2) amount of funding received, (3) source of funding and (4) monitoring efforts. The first type are large-scale projects, which receive high amounts of funding provided by international donors, and with a well-established monitoring plan; the second type are projects financed with private money, typically lacking a sound monitoring program; and the third type represents small projects with low amounts of funding, financed with public funds from national governments, often with a rudimentary monitoring plan. The typology enables a comparative analysis of the status and trends of restoration activities across Latin America. We conclude that, despite growing awareness and recognition that integrated approaches are needed to revert complex and interconnected socio-economic and environmental issues like land degradation, the socio-economic dimension remains underexposed in the majority of restoration projects, whereas monitoring is still regarded as an extra cost instead of a necessary investment.