Hartmut Dierschke

Microclimate moderates plant responses to macroclimate warming

Significance Around the globe, climate warming is increasing the dominance of warm-adapted species—a process described as “thermophilization.” However, thermophilization often lags behind warming of the climate itself, with some recent studies showing no response at all. Using a unique database of more than 1,400 resurveyed vegetation plots in forests across Europe and North America, we document significant thermophilization of understory vegetation. However, the response to macroclimate warming was attenuated in forests whose canopies have become denser. This microclimatic effect likely reflects cooler forest-floor temperatures via increased shading during the growing season in denser forests. Because standing stocks of trees have increased in many temperate forests in recent decades, microclimate may commonly buffer understory plant responses to macroclimate warming. Recent global warming is acting across marine, freshwater, and terrestrial ecosystems to favor species adapted to warmer conditions and/or reduce the abundance of cold-adapted organisms (i.e., “thermophilization” of communities). Lack of community responses to increased temperature, however, has also been reported for several taxa and regions, suggesting that “climatic lags” may be frequent. Here we show that microclimatic effects brought about by forest canopy closure can buffer biotic responses to macroclimate warming, thus explaining an apparent climatic lag. Using data from 1,409 vegetation plots in European and North American temperate forests, each surveyed at least twice over an interval of 12–67 y, we document significant thermophilization of ground-layer plant communities. These changes reflect concurrent declines in species adapted to cooler conditions and increases in species adapted to warmer conditions. However, thermophilization, particularly the increase of warm-adapted species, is attenuated in forests whose canopies have become denser, probably reflecting cooler growing-season ground temperatures via increased shading. As standing stocks of trees have increased in many temperate forests in recent decades, local microclimatic effects may commonly be moderating the impacts of macroclimate warming on forest understories. Conversely, increases in harvesting woody biomass—e.g., for bioenergy—may open forest canopies and accelerate thermophilization of temperate forest biodiversity.

Species-rich beech woods in mesic habitats in central and western Europe: a regional classification into suballiances

On the basis of 8697 relevés a syntaxonomical survey of beech woods of central and western Europe is presented. The review table is restricted to beech and fir-beech communities in mesic habitats (without Luzulo- and Cephalanthero-Fagenion). It shows 11 groups of differential species. Their combination leads to 4 suballiances of Fagion: Endymio-, Scillo-, Galio odorati- and Lonicero alpigenae-Fagenion. For each suballiance the nomenclatural type and a short description is given.

Stand und Aufgaben der Pflanzensoziologischen Systematik in Europa

Nachdem withrend des Symposions tiber pflanzensoziologische Systematik in Stolzenau 1964 verschiedene VorschHige gemacht wurden und eine Resolution zur Schaffung eines europXischen Prodomus der Pflanzengesellsehaften aufforderte, war es um diese Fragen wieder still geworden. Ein zweit~igiges Kolloquium, von Prof. TOXEN im April 1968 in Todenmann einberufen, zu dem fiihrende Pflanzensoziologen aus allen europ~tischen L~indern eingeladen waren, sollte alten Pl~inen neuen Aufschwung geben. Nach zwei weiteren Kurztagungen im M~irz 1969 und 197o sind jetzt die Vorbereitungen so weit gediehen, dab in absehbarer Zeit erste Ergebnisse zu erwarten sind. Es erscheint deshalb n~tztich, einen kurzen Bericht fiber den augenblicklichen Stand der Arbeiten und die ihnen vorangehenden Beratungen zu geben.

Grundwasser — Ganglinien einiger Pflanzengesellschaften des Holtumer Moores östlich von Bremen

In den Jahren 1963–65 wurden im Holtumer Moor unter verschiedenen Gesellschaften des Bromo-Senecionetum aquaticae und des Lolio-Cynosuretum die Grundwasserstände in Meßbrunnen beobachtet und die Ergebnisse zu Ganglinien zusammengestellt. Jeder der rein floristisch-pflanzensoziologisch unterschiedenen Vegetationseinheiten konnte ein charakteristischer Ganglinientyp zugeordnet werden, der durch jeweils verschiedene Höhe und Schwankungsamplitude des Grundwasserspiegels gekennzeichnet ist. In the period 1963–65 the groundwater levels under different communities of the Bromo-Senecionetum aquaticae and the Lolio-Cynosuretum in the Holtum moor area were observed. The results were brought together in graphs. It was possible to relate each of the floristic-sociological units to a characteristic graph line type which is defined respectively by the different heights and fluctuation amplitudes of the groundwater levels.

Ecological Indicator Values of Europe (EIVE) 1.0: a powerful open-access tool for vegetation scientists

Background: Ecological indicator values (EIVs) have a long tradition in vegetation ecological research in Europe. EIVs characterise the ecological optimum of species along major environmental gradients using ordinal scales. Calculating mean indicator values per plot is an effective way of bioindication. Following first systems in Russia and Central Europe, about two dozen EIV systems have been published for various parts of Europe. Aims: As there was no EIV system available at European scale that could be used for broad- scale analyses, e.g. in the context of the European Vegetation Archive (EVA), we develop such a system for the first time for the vascular plants of Europe. Location: Europe. Methods: We compiled all national and major regional EIV systems and harmonized their plant nomenclature with a newly developed contemporary European taxonomic backbone (EuroSL 1.0). Using regression, we rescaled the individual EIV systems for the main parameters to continent-wide quasi-metric scales, ranging from 1 to 99. The data from each individual system were then translated into a probability curve approximated with a normal distribution, weighed with the logarithm of the area represented and summed up across the systems. From the European density curve we extracted then a mean and a variance, which characterise the distribution of this species along this particular ecological gradient. Results and conclusions: Our consensus approach of integrating the expert knowledge of all existing EIV systems allowed deriving the first consistent description of the ecological behaviour for a significant part of the European vascular flora. The resulting Ecological Indicator Values of Europe (EIVE) 1.0 will be published open access to allow bioindication beyond country borders. Future releases of EIVE might contain more parameters, non- vascular plants and regionalisation or could be re-adjusted and extended to hitherto non- covered species through co-occurrence data from EVA.