A high-altitude lake sediment sequence (Buhăiescu Mare, 1918 m a.s.l.) in the subalpine zone of the Rodna Mountains was analysed through a multi-proxy approach to determine the sensitivity of high mountain habitats to climate, fire and land use changes. The early Holocene regional forests were dominated by Pinus ( sylvestris and mugo) and replaced by Picea abies from 9800 cal. yr BP. After an extended hiatus in the profile ( c. 9800–4200 cal. yr BP), probably because of the physical removal of sediments through avalanche or high-flow events, P. abies, Abies alba and Fagus sylvatica forests developed after 4200 cal. yr BP. The timberline and treeline reacted sensitively to past changes in climate and human impact. The site was probably situated above the treeline throughout most of the investigated period. However, a treeline ecotone or krummholz zone may have sporadically reached the lake’s elevation in the early Holocene. A decline in timberline and treeline elevation was noted during the last 1200 years, and more evidently over the past 200 years, with replacement by subalpine shrubs ( Alnus viridis) and alpine herbaceous communities. Because these vegetation changes were associated with an increased prevalence of pollen-based anthropogenic indicators, charcoal particles and abiotic indicators, human-induced fires and clearance and resultant erosion inputs to the lake are implied. Effects of current warming on the altitude range of trees are not yet visible, probably because land use has more strongly contributed to changes in land cover than the climate fluctuations of the last millennium in the Rodna Mountains.
a b s t r a c t a r t i c l e i n f oWe provide sedimentological, geochemical, mineral magnetic, stable carbon isotope, charcoal, and pollen-based evidence from a guano/clay sequence in Gaura cu Muscă Cave (SW Romania), from which we deduced that from 1230 BC to~AD 1240 climate oscillated between wet and dry. From~1230 BC to AD 1000 the climate was wetter than the present, prompting flooding of the cave, preventing bats from roosting, and resulting in a slow rate of clay accumulation. The second half of the Medieval Warm Period (MWP) was generally drier; the cave experienced occasional flash flooding in between which maternity bat roosts established in the cave. One extremely wet event occurred around AD 1170, when Fe/Mn and Ti/Zr ratios show the highest values coincident with a substantial increase of sediment load in the underground stream. The mineral magnetic characteristics for the second part of the MWP indicate the partial input of surface-sourced sediments reflecting agricultural development and forest clearance in the area. Pollen and microcharcoal studies confirm that the overall vegetation cover and human land use have not changed much in this region since the medieval times.
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