Pleta dels Molières is a valley-bottom peatland located in the SCI Aigüestortes, part of the European Natura 2000 network, in the central Pyrenees, near Vielha (Val d’Aran, Catalonia, 42.62ºN, 0.74ºE; 1,720 m a.s.l.). The peatland develops under acidic soil conditions (pH ~4.5–5.5), which shape a mosaic of habitats that includes heather (Erica tetralix) and Sphagnum hummocks, rheophilous fens dominated by Trichophorum, and acid fens with Carex nigra. It represents one of the most characteristic examples of peat-forming acidic wetlands in the region.

The climate is temperate mountain, with mean annual temperatures around 6–7 °C and annual precipitation between 1,200–1,600 mm. Precipitation falls predominantly as rain (≈70–85%), with snow accounting for roughly 15–30% of annual totals. Snowfall is concentrated in the winter months, where it contributes to seasonal snow cover and plays a key role in soil moisture recharge and early spring runoff, despite not being the dominant form of precipitation.

The site lies on granite substrates and is hydrologically connected to headwater streams, creating strong links between soils, groundwater, and surface waters. These connections regulate how carbon and nutrients are stored, transformed, and released, while also influencing the mobility of minor elements such as phosphorus, iron, and silica. During wetter periods, organic matter and nutrients can be flushed out, contributing to export fluxes of dissolved carbon and nitrogen to downstream waters. This makes Pleta dels Molières a valuable site for studying how peatlands mediate elemental cycles and their impacts on water quality in mountain ecosystems, and for understanding how environmental changes may alter these processes.