Close anthropogenic control of Fagus sylvatica establishment and expansion in a Swedish protected landscape – implications for forest history and conservation

Aim The dominant forces behind the expansion of Fagus sylvatica (beech) in northern Europe during the late Holocene have been much debated. Palaeoecological analyses were performed for a biodiversity hotspot reserve in order to study the processes behind the local establishment of Fagus, as well as the historical vegetational development in relation to present‐day biodiversity and conservation. Location Biskopstorp Forest Reserve in south‐west Sweden. Methods Pollen and charcoal were analysed from three small‐hollow sites in the reserve. Two of the investigated wetlands were located adjacent to old‐growth stands of Fagus, and the third was located near a stand of old Quercus. Results The 2500‐year record shows that Fagus was first established around the two Fagus old‐growth sites, c. ad 900 and 1200, respectively, and that this was followed by an expansion around ad 1600. During the establishment phase, and more so in the expansion phase, there were simultaneous increases in types of pollen indicative of human activity. These indicators are also frequent throughout the record from the Quercus site, but here Fagus never became common. Main conclusions The dynamics behind the establishment and expansion of Fagus in the reserve seems to have been influenced to a large degree by human activity, for example selective cutting, human‐induced fires, and agriculture. Fagus became established in the reserve more than 1000 years after it became established regionally, making climate less probable as the dominant force behind the species’ stand‐scale establishment. The spreading of Fagus across southern Scandinavia has previously been shown to be a patchy process in time and space. Our study suggests that this patchiness is evident also at a small spatial scale (a few kilometres). At the Quercus site, relatively high amounts of pollen from the field layer throughout the record indicate open conditions that probably favoured Quercus. The degree of human impact at this site was probably too high to allow the expansion of Fagus. With the long‐term perspective provided by our study it was possible to identify the last 200–300 years as an unrepresentative period with respect to tree species composition and forest dynamics. The large increase of Picea locally and regionally over the last several hundred years, combined with dramatic levels of human impact, have altered the tree composition and forest dynamics to such an extent that active management is necessary in order to maintain biodiversity in the reserve.     

A long‐term record of Quercus decline,logging and fires in a southern Swedish Fagus‐Picea forest

Abstract. We reconstructed forest development and disturbance events (fire and logging) during the last 1000 yr with tree‐ring data, pollen and charcoal analysis from a semi‐natural Fagus sylvatica‐Picea abies forest (ca. 1 km²) in the hemiboreal zone. According to pollen analysis, Quercus robur together with Pinus sylvestris was abundant in the forest until the turn of the 18th/19th centuries when these species disappeared completely (Quercus) or nearly completely (Pinus) and were replaced by Fagus and Picea. The disappearance of Quercus was corroborated by the remarkable discovery of a single Quercus stump that had been cut in the 18th century and had become overgrown and preserved by a very old Picea. In total 11 fires were dated from 1555 to 1748 from fire scars in several Pinus stumps cut 100 ‐ 200 yr ago. Since the last fire in 1748, no Quercus or Pinus have regenerated in the core of the reserve apart from single pines in neighbouring managed forest (80 yr ago). During the period of documented fires Fagus was protected from fires in a refuge made up of large boulders. Picea colonized the region at the time when the fires ceased 250 yr ago. We hypothesize that most of the fires were probably of human origin because of their patchiness and high frequency compared to the natural background levels of lightning ignitions in the region. On a 300‐yr time scale, logging and fire suppression seem to strongly overshadow the effect of climate change on forest composition and dynamics.