Luis Merino-Martín

Plot-scale effects on runoff and erosion along a slope degradation gradient.

Received 17 February 2009; revised 31 October 2009; accepted 16 November 2009; published 6 April 2010. [1] In Earth and ecological sciences, an important, crosscutting issue is the relationship between scale and the processes of runoff and erosion. In drylands, understanding this relationship is critical for understanding ecosystem functionality and degradation processes. Recent work has suggested that the effects of scale may differ depending on the extent of degradation. To test this hypothesis, runoff and sediment yield were monitored during a hydrological year on 20 plots of various lengths (1–15 m). These plots were located on a series of five reclaimed mining slopes in a Mediterranean‐dry environment. The five slopes exhibited various degrees of vegetative cover and surface erosion. A general decrease of unit area runoff was observed with increasing plot scale for all slopes. Nevertheless, the amount of reinfiltrated runoff along each slope varied with the extent of degradation, being highest at the least degraded slope and vice versa. In other words, unit area runoff decreased the least on the most disturbed site as plot length increased. Unit area sediment yield declined with increasing plot length for the undisturbed and moderately disturbed sites, but it actually increased for the highly disturbed sites. The different scaling behavior of the most degraded slopes was especially clear under high‐intensity rainfall conditions, when flow concentration favored rill erosion. Our results confirm that in drylands, the effects of scale on runoff and erosion change with the extent of degradation, resulting in a substantial loss of soil and water from disturbed systems, which could reinforce the degradation process through feedback mechanisms with vegetation.

Seed ecology informs restoration approaches for threatened species in water-limited environments: a case study on the short-range Banded Ironstone endemic Ricinocarpos brevis (Euphorbiaceae)

Translocation of threatened species is challenging in semiarid environments, especially when seeds are the principal means of in situ establishment. Worldwide, the overall success of translocations using seeds is highly variable and generally unpredictable. Most seed-based translocations are embarked upon with limited understanding of the species’ seed biology or the nuances of the local abiotic environment in which to guide restoration approaches. For instance, within Australia just 14% of threatened species translocations use directly sown seeds and consequently, to improve the chances of restoration success, both the seed biology and the influence of the abiotic environment need to be adequately understood. We investigated these aspects in Ricinocarpos brevis R.J.F.Hend. & Mollemans – a short-range Banded Ironstone endemic – by focusing on a series of laboratory and field experiments to understand the key drivers of dormancy alleviation and germination promotion, as well as in-situ conditions of natural and recipient translocation sites. Fresh seeds were found to have high viability, fully developed linear embryos and possess physiological dormancy, with enhanced germination when exposed to smoke water, karrikinolide (KAR1) and gibberellic acid (GA3). Under laboratory conditions, seeds germinated over a range of temperatures (15−30°C), but germination was suppressed by light and highly sensitive to water stress. Seeds had reduced germination when sown on the soil surface, but could emerge from up to 13 cm in depth. Under field conditions, in-situ emergence was <2%. Using in-situ emergence results, soil loggers and rainfall data, we developed a model of the recruitment bottlenecks faced by this species under in-situ conditions, an approach that provides useful insights to assist future translocations. Understanding seed biology and seed ecology enables better insights into the principal bottlenecks restricting in-situ emergence and consequently restoration success, leading to the development of more effective approaches for conserving other threatened flora in future.

Land cover effects on water balance partitioning in the Colombian Andes: improved water availability in early stages of natural vegetation recovery

Vegetation actively affects different components of the water budget in multiple spatial and temporal scales. Changes in vegetation cover and structure—such as those resulting from land use—alter natural ecohydrological dynamics, leading to changes in natural hydrologic regimes. In tropical mountain ecosystems, such as the Colombian Andes, significant areas of native forests have been converted to agro-ecosystems that include pasturelands and croplands, to supply societal demands for other ecosystem services. Yet, services such as water provision and hydropower generation that depend on the regulation of hydrologic fluxes are also demanded from these ecosystems, potentially generating conflicting societal demands. In this study, we assess the effect of vegetation cover type and rainfall seasonality on the dynamics of hydrological partitioning—an indicator of hydrologic regulation—at three temporal scales, in a simulated gradient of human disturbance characterized by seven types of vegetation cover. Overall, vegetation cover effects on hydrologic partitioning are more pronounced in shorter, weekly to seasonal, timescales than in annual timescales. Natural vegetation cover types have a higher potential for maintaining water availability, as evidenced by lower variability of soil moisture storage and hydrological fluxes both within and between seasons. Notably, among all cover types, early stages of natural vegetation recovery appear to be more effective in maintaining higher levels of soil moisture while decreasing potential overland flow and other water losses, therefore more effectively contributing to deep drainage and potentially to groundwater recharge, which relate to hydrologic regulation and, ultimately, water availability. Collectively, our results provide insights for decision-making in land management, particualrly when provisioning and regulatory ecosystem services are demanded from these strategic ecosystems.