Laura Quijano

Establishing a tracer-based sediment budget to preserve wetlands in Mediterranean mountain agroecosystems (NE Spain)

Mountain wetlands in Mediterranean regions are particularly threatened in agricultural environments due to anthropogenic activity. An integrated study of source-to-sink sediment fluxes was carried out in an agricultural catchment that holds a small permanent lake included in the European NATURA 2000 Network. More than 1000 yrs of human intervention and the variety of land uses pose a substantial challenge when attempting to estimate sediment fluxes which is the first requirement to protect fragile wetlands. To date, there have been few similar studies and those that have been carried out have not addressed such complex terrain. Geostatistical interpolation and GIS tools were used to derive the soil spatial redistribution from point (137)Cs inventories, and to establish the sediment budget in a catchment located in the Southern Pyrenees. The soil redistribution was intense and soil erosion predominated over soil deposition. On the areas that maintained natural vegetation the median soil erosion and deposition rates were moderate, ranging from 2.6 to 6 Mg ha yr(-1) and 1.5 to 2.1 Mg ha yr(-1), respectively. However, in cultivated fields both erosion and deposition were significantly higher (ca. 20 Mg ha yr(-1)), and the maximum rates were always associated with tillage practices. Farming activities in the last part of the 20th century intensified soil erosion, as evidenced by the 1963 (137)Cs peaks in the lake cores and estimates from the sediment budget indicated a net deposition of 671 Mg yr(-1). Results confirm a siltation risk for the lake and provide a foundation for designing management plans to preserve this threatened wetland. This comprehensive approach provides information useful for understanding processes that influence the patterns and rates of soil transfer and deposition within fragile Mediterranean mountain wetlands subjected to climate and anthropogenic stresses.

Lateral and depth patterns of soil organic carbon fractions in a mountain mediterranean agrosystem

48 Pags.- 6 Tabls.- 6 Figs. The definitive version is available at: http://journals.cambridge.org/action/displayJournal?jid=AGS

Radionuclides and soil properties as indicators of glacier retreat in a recently deglaciated permafrost environment of the Maritime Antarctica

Many ice-free environments in Maritime Antarctica are undergoing rapid and substantial environmental changes in response to recent climate trends. This is the case of Elephant Point (Livingston Island, South Shetland Islands, SSI), where the glacier retreat recorded during the last six decades exposed 17% of this small peninsula, namely a moraine extending from the western to the eastern coastlines and a relatively flat proglacial surface. In the southern margin of the peninsula, a sequence of Holocene raised beaches and several bedrock plateaus are also distributed. A main issue in this environment is the role of glacier retreat and permafrost controlling the recently formed soils. To this purpose, a total of 10 sites were sampled along a transect crossing raised beaches and moraine materials following the direction of glacier retreat. At the selected sites surface samples were collected until 12cm depth and sectioned at 3cm depth intervals to analyse main properties, grain size, pH, electrical conductivity and carbonates. Besides, elemental composition and fallout (FRNs) and environmental radionuclides (ERNs) were analysed. To assess if profile characteristics within the active layer are affected by glacier retreat variations of organic carbon and carbon fractions and 137Cs contents were examined. The presence of organic carbon (range: 0.13-3.19%), and 137Cs (range: bdl-10.1Bqkg-1) was only found at the raised beaches. The surface samples had abundant coarse fractions in rich sandy matrix with increasing acidic pH towards the coast. Significant differences were found in the elemental composition and the radionuclides between the moraine and raised beaches. Soil forming processes are related to the time of exposure of the landforms after glacier retreat. The results obtained confirm the potential for using geomorphological, edaphic and geochemical data to assess the influence of different stages of glacier retreat in recent soils and sediments.

NDVI, 137Cs and nutrients for tracking soil and vegetation development on glacial landforms in the Lake Parón Catchment (Cordillera Blanca, Perú)

The present dominant trend of retreating and shrinking glaciers is leading to the formation of new soil in proglacial zones. The Cordillera Blanca located in the Peruvian Andes includes the Lake Parón catchment known for the Artesonraju Glacier and its rapid retreat, forming the largest proglacial lake in the region. This work aims to gain knowledge of soil and vegetation development on the most representative proglacial landforms existing in the Parón catchment. Previous research in proglacial environments suggests that soil properties might indicate different ages of ice retreat besides the normalised difference vegetation index (NDVI), which is known to be a powerful tool for assessing vegetation development. In the area surrounding Lake Parón up to the glacier tongue, an altitudinal transect (4200-4700 m a.s.l.) was established for sampling topsoils. A total of 40 surface soil samples (0-3 cm) were collected from the main glacial landforms, moraines, colluvium, glacio-fluvial terraces and alluvial fans, developed after different stages of glacier retreat. Soil organic carbon (SOC) and SOC fractions (active and stable), total nitrogen (TN) and 137Cs were analysed. A multitemporal analysis of NDVI was performed to assess the vegetation dynamics in the Parón catchment and over the different glacial landforms over time (1987-2018). The NDVI increase in recent decades indicates an expansion of vegetation cover and density. We compared NDVI values with the SOC and TN content to assess the relationships with vegetation growth in mountain soils. NDVI and the distribution of SOC and TN content show a positive correlation between vegetation evolution and the enrichment in soil nutrients that are more abundant in older moraines in coincidence with highest NDVI. These results outline the effect of shrinking mountain glaciers on generating new soils in parallel with the growth of vegetation.