The pastures were greener over there: Contrasting human management in Pyrenean subalpine ecosystems through sedaDNA

The impacts of current and projected global change on fragile high-altitude mountain ecosystems highlight the need to understand how these systems responded to both past climatic variability and human activities in order to better interpret ongoing changes. Throughout the Holocene, a number of disturbances have produced significant impacts on ecosystem functionality. A paramount example is pastoralism in mountain environments, that may have induced modifications and long-term ecological changes. In the Pyrenees, the first and earliest evidence of unequivocal human landscape management has been identified through sedimentary ancient DNA (sedaDNA), revealing an anthropogenic landscape opening linked to the early presence of domestic animals at the lower subalpine belt (Tramacastilla, 1682 m a.s.l.) ca. 6 ka BP. In this research we present a new record of landscape evolution and human activity presence at the upper subalpine boundary of the Pyrenees by analyzing sedaDNA at Basa de la Mora lake (BSM, 1913 m a.s.l; central Pyrenees).

We recovered a new lacustrine sequence from BSM to reconstruct Holocene plants and animal communities using sedimentary ancient DNA (sedaDNA), together with additional proxies to infer fire activity and temperature variability. These results are compared with the Tramacastilla lacustrine record and its sedaDNA reconstruction in order to identify differences in human land-use practices across subalpine ecosystems at different elevations during the last 9 ka BP.

Our result proves two contrasting cases of landscape management and plant community responses to disturbance in high-altitude environments during the same chronological period: Tramacastilla primarily shaped by human management, where diversity patterns dramatically change with human activity, and Basa de la Mora, mainly responding to natural disturbances such as fire and temperature variability.