NDVI, Cs 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 Cs 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.