Millennial land use explains modern high-elevation vegetation in the submediterranean mountains of Southern Europe

Aim Pinewood decline and scrubland expansion are major features of Late Holocene vegetation history in the Cantabrian Range. However, the drivers of this remarkable vegetation shift remain to be investigated. Here, we aim at disentangling the role of past land use and climate in shaping the high-elevation Cantabrian landscape during the past two millennia. Location Cantabrian Range (northern Iberia). Taxa Pinus sylvestris, Betula, Ericaceae, Juniperus, Poaceae. Methods We conducted high-resolution multiproxy palaeoecological analyses (pollen, plant macrofossils, microscopic charcoal and dung fungi) on lake sediments from Lago del Ausente to reconstruct vegetation, fire occurrence and grazing through time. The chronology is based on C-14 (terrestrial plant macrofossils) and Pb-210 dating, and Bayesian age-depth modelling ('rbacon'). We carried out cross-correlation analysis to quantify vegetation responses to fire. Results Between 250 and 900 CE, the vegetation above 1700 m a.s.l. consisted of subalpine scrubland and scattered P. sylvestris trees/stands. Pinewoods with Betula were widespread at slightly lower elevation. This vegetation was resilient to moderate fire disturbance associated with limited pastoral activities. In contrast, enhanced fire occurrence alongside heavier pastoralism led to the demise of pinewoods and their replacement with Betula stands, subalpine scrublands, and meadows between 900 and 1100 CE. Later, the subalpine scrubland-birch tree line did not respond to Little Ice Age cooling. However, further intensification of transhumant herding between 1300 and 1860 CE ('La Mesta') triggered birch decline and the establishment of the modern treeless landscape. Main conclusions The extant high-elevation vegetation of the Cantabrian Range is largely the legacy of intensive land use starting more than one millennium ago. Recurrent and severe fires to promote pasturelands led to the regional extirpation of the previously widespread Pinus sylvestris. Future management should aim at preserving the valuable cultural open landscape of mountain scrubland and meadows and also at restoring patches of ancient pine-birch woodlands.

Automated summary

This study investigated the drivers of vegetation change in the Cantabrian Range during the Late Holocene. The results showed that past land use and climate change have played a significant role in shaping the high-elevation vegetation, particularly the decline of pine and expansion of scrubland. Future management should focus on preserving and restoring mountain scrubland and meadows, as well as reestablishing ancient pine-birch woodlands.