Causes and mechanisms of synchronous succession trajectories in primeval Central European mixed Fagus sylvatica forests

Abstract

1. Natural succession trajectories of Central European forest ecosystems are poorly understood due to the absence of long-term observations and the pervasive effects of past human impacts on today's vegetation communities. This knowledge gap is significant given that currently forest ecosystems are expanding in Europe as a consequence of global change.2. Annually laminated sediments were extracted from two small lowland lakes (Moossee 521 m a.s.l.; Burgäschisee 465 m a.s.l.) on the Swiss Plateau. We combine high-resolution palaeoecological and quantitative analyses to assess changes in vegetation during the Neolithic. We test for regionally synchronous land-use phases and plant successional patterns that may originate from complex interactions between human and climatic impacts. 3. Mixed Fagus sylvatica forests dominated the Swiss Plateau vegetation over millennia. During the period 6,500-4,200 cal year bp, pronounced forest disruptions accompanied by increased fire and agricultural activities occurred at c. 6,400-6,000 cal year bp, 5,750-5,550 cal year bp, around 5,400 cal year bp and at 5,100-4,600 cal year bp. Biodiversity increased during these land-use phases, likely in response to the creation of new open habitats. After decades to centuries of land-use, arboreal vegetation re-expanded. In a first succession stage, heliophilous Corylus avellana shrubs were replaced by pioneer Betula trees. These open arboreal communities were out-competed within 150-200 years by late-successional F. sylvatica and Abies alba forests. Most strikingly, cross-correlations show that these successions occurred synchronously (±11 years) and repeatedly over large areas (>1,000 km 2 ) and millennia. 4. Synthesis. First notable human impact shaped the primeval mixed Fagus sylvatica forests in Central Europe from c. 6,800-6,500 cal year bp on. Agrarian societies were susceptible to climate changes and we hypothesize that climate-induced, simultaneous agricultural expansion and contraction phases resulted in synchronous regional forest successions. Currently, forests are expanding in Central Europe as a result of land abandonment in marginal areas. Our results imply that mixed Fagus sylvatica forests with Abies alba and Quercus may re-expand rapidly in | 1393 Journal of Ecology REY Et al.

Congruent patterns of functional diversity in saproxylic beetles and fungi across European beech forests

“…20,000 years ago), European beech survived in several distinct refugia in southern Europe, but these refugia contributed very differently to the re‐colonization process (Magri, ), which continues to date, with an expansion of several hundred metres per year towards the north in Sweden (Björkman, ) and towards the northeast in Poland (Latalowa, ). Early on, natural beech forests began to be replaced by farmland and urban areas, with decreasing historical land use intensity from west to east (Kaplan, Krumhardt, & Zimmermann, ; Peterken, ; Rey et al., ; Rose, ), but distribution was partly also favoured by humans regionally (Björkman, ).…”

Wälder in der Zeitmaschine – Möglichkeiten und Grenzen der Paläoökologie

“…die Zunahme von Kulturbegleitern (den «Unkräutern»). Da die tieferen Lagen im Früh-Holozän vollständig bewaldet waren, setzten die jungsteinzeitlichen Bauern Feuer ein, um Flächen für den Ackerbau zu gewinnen (Gobet et al 2010, Schwörer et al 2015, Rey et al 2018, Tinner et al 1999. Mit dem Anbau von Kulturpflanzen wurden auch Ackerbegleitpflanzen eingeschleppt (sogenannte Adventiten) und gewisse einheimische Pflanzen gefördert (sogenannte Apophyten).…”

Climate impacts on deglaciation and vegetation dynamics since the Last Glacial Maximum at Moossee (Switzerland)

“…The standard sampling was 1 cm 3 every 10 cm. A higher resolution was implemented for the Oldest Dryas (18,800-14,700 cal BP) and for the Neolithic-Mid Bronze Age (7400-3200 cal BP, see Rey et al, 2019a). All palynological samples were treated with HCl, KOH, HF, acetolysis, sieved with a mesh size of 0.5 mm and mounted in glycerine following standard approaches (Moore et al, 1991).…”

“…We first applied rarefaction analysis to calculate palynological richness (PRI), which is frequently used as a proxy for local to regional species richness (e.g. Birks and Line, 1992;Odgaard, 1999;Schwörer et al, 2015;Rey et al, 2019a). Rarefaction analysis assesses the number of taxa per sample after setting a constant minimum 150 terrestrial pollen sum (Birks and Line, 1992), which was 116 in our case.…”

“…slash-and-burn, e.g. Tinner et al, 1999;Kleinmann et al, 2015;Rey et al, 2017Rey et al, , 2019a. Disruption and land use phases generated typical successional cycles starting with arboreal pioneers (Corylus avellana, tree Betula and Alnus) rapidly spreading after disturbance.…”