1,721,002 research outputs found
Change in the bryophyte diversity and species composition of Central European temperate broad-leaved forests since the late nineteenth century
No full textThe diversity and species composition of the bryophyte flora colonizing the forest floor, live trees and deadwood in semi-natural broad-leaved forests of northern Germany was compared between a recent survey in 2013 and historical records from around 1900. The survey was based on the comparison of presence/absence data and their interpretation with help of ecological indicator values. Total species richness has declined in bryophytes growing on the forest floor but not in the other guilds, whereas a dramatic species turnover was found for all three guilds. This turnover was apparently primarily driven by the increased atmospheric load of reactive nitrogen from anthropogenic emissions. Sensitive species were replaced by more eutrophication-tolerant bryophytes; liverworts are overrepresented among the sensitive and thus declining species. Promotion of the competitive strength of vascular plants due to increased nitrogen levels is the likely cause of the reduction of bryophyte species richness on the forest floor. Former acidification by high atmospheric sulfur dioxide loads has left an imprint in the bryophyte vegetation by having favored acidophytic species and discriminating against basiphytic species. An increase in the mean indicator value for temperature suggests a beginning effect of climate warming on the bryophyte vegetation. Change in forest structure had an apparently smaller imprint on the bryophyte diversity of the studied semi-natural forests than atmospheric chemistry and climate. In this respect, bryophytes differ from the ecologically similar lichens, where published studies from the same region showed a dramatic decline of species richness and a stronger susceptibility to forest management
Ergebnisse einer Fallstudie aus dem Harz
No full textKurzfassung: Wirtschaftswälder unterscheiden sich grundlegend von Naturwäldern durch die Seltenheit von Bäumen jenseits des Umtriebsalters in der Alters- und Zerfallsphase sowie durch einen radikaleren Bruch der Bestandeskontinuität zwischen den aufeinanderfolgenden Waldgenerationen. Die natürliche Bestandesdynamik infolge altersbedingter Mortalität und externerr Störungen in vom Menschen nicht genutzten Wäldern führt zu einem heterogenen Muster von unterschiedlich großen Teilflächen unterschiedlicher Waldentwicklungsstadien und zur Bildung von Bestandeslücken. In Mitteleuropa sind Waldbestände, die zumindest seit mehreren Jahrhunderten einer natürlichen Bestandesdynamik ausgesetzt sind, äußerst selten. In einer Fallstudie im Harz (Deutschland) hatten wir die Gelegenheit, einen solchen Bestand zu untersuchen (Brockenurwald). Ziel der Untersuchung war die vergleichende Analyse der pflanzlichen Diversität (Bodenvegetation, Epiphyten) sowie ausgewählter Ökosystemeigenschaften (oberirdische Biomasse, ökosystemarer Kohlenstoffvorrat) in fünf altersabhängigen Waldentwicklungsphasen (Verjüngungs-, Aufwuchs-, Optimum-, Alters- und Zerfallsphase). Während sich die Bodenvegetation kaum zwischen den Entwicklungsstadien unterschied, war der Artenreichtum epiphytischer Moose und Flechten auf den stehenden Bäumen in der Alters- und insbesondere der Zerfallsphase signifikant größer als in den jüngeren Entwicklungsstadien, die auch im Wirtschaftswald vorkommen. Der Artenreichtum auf liegendem (aus der vorangegangenen Waldgeneration stammendem) Totholz war am höchsten in der Verjüngungs- und der Aufwuchsphase. Die oberirdische Biomasse und die Kohlenstoffvorräte waren in der Alters- und in der Zerfallsphase größer als in den anderen Waldentwicklungsstadien. Der Kohlenstoffvorrat im Boden war unabhängig vom Waldentwicklungsstadium konstant hoch. Unsere Ergebnisse unterstreichen die große Bedeutung der Alters- und Zerfallsphase und einer natürlichen Bestandesdynamik für die pflanzliche Diversität von Wäldern und für die Fähigkeit, große Vorräte an Kohlenstoff zu speichern
Ergebnisse einer Fallstudie aus dem Harz
No full textKurzfassung: Wirtschaftswälder unterscheiden sich grundlegend von Naturwäldern durch die Seltenheit von Bäumen jenseits des Umtriebsalters in der Alters- und Zerfallsphase sowie durch einen radikaleren Bruch der Bestandeskontinuität zwischen den aufeinanderfolgenden Waldgenerationen. Die natürliche Bestandesdynamik infolge altersbedingter Mortalität und externerr Störungen in vom Menschen nicht genutzten Wäldern führt zu einem heterogenen Muster von unterschiedlich großen Teilflächen unterschiedlicher Waldentwicklungsstadien und zur Bildung von Bestandeslücken. In Mitteleuropa sind Waldbestände, die zumindest seit mehreren Jahrhunderten einer natürlichen Bestandesdynamik ausgesetzt sind, äußerst selten. In einer Fallstudie im Harz (Deutschland) hatten wir die Gelegenheit, einen solchen Bestand zu untersuchen (Brockenurwald). Ziel der Untersuchung war die vergleichende Analyse der pflanzlichen Diversität (Bodenvegetation, Epiphyten) sowie ausgewählter Ökosystemeigenschaften (oberirdische Biomasse, ökosystemarer Kohlenstoffvorrat) in fünf altersabhängigen Waldentwicklungsphasen (Verjüngungs-, Aufwuchs-, Optimum-, Alters- und Zerfallsphase). Während sich die Bodenvegetation kaum zwischen den Entwicklungsstadien unterschied, war der Artenreichtum epiphytischer Moose und Flechten auf den stehenden Bäumen in der Alters- und insbesondere der Zerfallsphase signifikant größer als in den jüngeren Entwicklungsstadien, die auch im Wirtschaftswald vorkommen. Der Artenreichtum auf liegendem (aus der vorangegangenen Waldgeneration stammendem) Totholz war am höchsten in der Verjüngungs- und der Aufwuchsphase. Die oberirdische Biomasse und die Kohlenstoffvorräte waren in der Alters- und in der Zerfallsphase größer als in den anderen Waldentwicklungsstadien. Der Kohlenstoffvorrat im Boden war unabhängig vom Waldentwicklungsstadium konstant hoch. Unsere Ergebnisse unterstreichen die große Bedeutung der Alters- und Zerfallsphase und einer natürlichen Bestandesdynamik für die pflanzliche Diversität von Wäldern und für die Fähigkeit, große Vorräte an Kohlenstoff zu speichern
Response of ground vegetation and epiphyte diversity to natural age dynamics in a Central European mountain spruce forest
No full textQuestion Natural forest age dynamics is often more or less cyclic, with profound temporal changes in stem density and tree size, tree age structure, deadwood frequency and the abundance of canopy gaps. We investigated the response of ground and epiphyte vegetation to the natural forest age dynamics of an old‐growth spruce forest focussing on (1) the influence of stand age‐related shifts in forest structure and related changes in soil conditions on the diversity and composition of plant communities, (2) differences in the species turnover of cryptogamic epiphytes and ground vegetation in relation to forest age development, and (3) the importance of later (advanced) forest development stages for characteristic epiphyte communities. Location High‐montane old‐growth spruce forest (Picea abies (L.) Karst.) on Mt. Brocken, Harz Mountains, Germany. Methods Five defined forest development stages (regeneration to decay) were investigated with five 100‐m² plots for each stage, in which we studied forest structure, ground vegetation and the epiphytes of living trees and dead trunks. Results The ground vegetation did not significantly change across the forest development stages. Epiphyte diversity on dead standing trees markedly increased towards later stages, with the highest diversity in the over‐mature and decay stages. Diversity of epiphytes on lying trunks was highest in early development stages. Trees in decay as well as regeneration stage included a set of characteristic epiphytes, being rare or absent in the other stages. Conclusions Deadwood, i.e. trees and lying trunks and their epiphytes, outlast the oldest individuals of the tree layer and are still present in the early stages of the following forest generation. Epiphyte diversity on lying deadwood was higher in young than late forest development stages. Habitat continuity presents a fundamental difference to managed forests; it promotes species with dispersal limitations, which are common among cryptogamic epiphytes
Results of a case study in the Harz Mountains
No full textManaged forests differ principally from old-growth forests by the scarcity of ageing and decaying trees beyond the rotation age as well as by the more radical disruption of stand continuity between consecutive forest generations. The natural dynamics due to age-dependent mortality and external disturbance in unmanaged stands results in a heterogeneous spatial pattern of differently sized patches of different forest development stages and in the formation of gaps. Forest stands, which follow natural forest dynamics since at least several centuries, are extremely rare in Central Europe. In a case study in the Harz Mountains, Germany, we had the opportunity to study such a forest stand (Bracken old growth forest). The objective of our study was the comparative analysis of plant diversity (ground vegetation, epiphytes) as well as of selected ecosystem properties (aboveground biomass, ecosystem carbon pool) in five age-dependent forest development stages (regeneration, initial, climax, over-mature, and decay stages). While the ground vegetation did hardly differ between the forest development stages, the species richness of epiphytic bryophytes and lichens on standing trees was significantly greater in the over-mature and decaying stages than in the earlier ones, which are also found in managed forests. The species richness on downed deadwood (originating from the preceding forest generation) was highest in the regeneration and initial stages. The aboveground biomass and carbon pools were higher in the over-mature and decaying stages than in the other forest development stages. The pool of soil organic carbon was consistently high across the forest development stages. Our results confirm the great importance of the over-mature and decaying stages for plant diversity and for the capability of forests to store high amounts of carbon
The significance of deadwood for total bryophyte, lichen, and vascular plant diversity in an old-growth spruce forest
No full textModern silviculture has led to a reduction in deadwood, especially that of large diameter, and thus the loss of an important habitat niche in most European forests. We analyzed the significance of deadwood for the total species diversity in three plant groups (bryophytes, lichens, and vascular plants) in one of Central Europe’s few remnants of unmanaged old-growth forest. The site is a montane forest of Picea abies on Mt. Brocken, Harz Mountains, Germany, which has not been managed for at least several centuries, undergoes natural forest dynamics, and thus harbors large amounts of standing and downed deadwood. Epiphyte vegetation of live trees and the ground vegetation were studied for comparison. We did not find any obligate deadwood species. Nevertheless, 84 % (70 species) of the total species were found on standing or downed deadwood. One-third of these species, or 28 % of the total species in the forest, were only sampled on deadwood, whereas the remaining species were also found on live trees and/or the ground. Bryophytes were the largest group of species on deadwood (47 % of the deadwood-inhabiting species), followed by lichens (37 %) and vascular plants (16 %). Large-diameter deadwood in an advanced stage of decay harbored more species than smaller fragments in the early stages of decay. Despite the lack of obligate deadwood colonizers, deadwood apparently plays a key role for forest plant diversity, mainly by providing an environment with low competition and thus facilitating the establishment of species
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Separating forest continuity from tree age effects on plant diversity in the ground and epiphyte vegetation of a Central European mountain spruce forest
No full textForest continuity has been identified as an important factor influencing the structure and diversity of forest vegetation. Primary forests with centuries of continuity are usually more diverse than young secondary forests as forest are colonized only slowly and because the former are richer in old tree individuals. In the present study, performed in unmanaged high-elevation spruce forests of the Harz Mountains, Germany, we had the unique opportunity to separate the effects of forest continuity and tree age on plant diversity. We compared an old-growth spruce forest with century-long habitat continuity with an adjacent secondary spruce forest, which had naturally established on a former bog after 1796 when peat exploitation halted. Comparative analysis of the ground and epiphyte vegetation showed that the plant diversity of the old-growth forest was not higher than that of the secondary forest with a similar tree age of >200 years. Our results suggest that a period of >200 years was sufficient for the secondary forest to be colonized by the whole regional species pool of herbaceous and cryptogam forest plants and epiphytes. Therefore, it is likely that habitat structure, including the presence of old and decaying trees, was more important for determining plant diversity than the independent effect of forest continuity. Our results are probably not transferrable to spruce forests younger than 200 years and highly fragmented woodlands with long distances between new stands and old-growth forests that serve as diaspore sources. In addition, our results might be not transferable to remote areas without notable air pollution, as the epiphyte vegetation of the study area was influenced by SO2 pollution in the second half of the 20th century
Lichen substance concentrations in the lichen Hypogymnia physodes are correlated with heavy metal concentrations in the substratum
No full textLichen substances (i.e. lichen-specific carbon-based secondary compounds) are known to be involved in the uptake and immobilization of metal ions, though the biochemical mechanisms of this interaction are largely unexplained. Previous research on potential effects of lichen substances on heavy metal uptake and tolerance mostly focused on lichens in heavily polluted areas with exceptionally high metal concentrations. In the present study, we aimed at gathering information as to whether lichen substances might be involved in the fine-tuning of metal uptake even at not or low-polluted sites. Therefore, we studied lichen substance concentrations in the epiphytic lichen Hypogymnia physodes and metal concentrations in its substratum in a montane spruce forest of Germany. H. physodes produces two depsides and five depsidones, which had been shown to be involved in metal homeostasis, namely in Cu and Mn uptake, in previous laboratory experiments. The amount of lichen substances increased with increasing heavy metal concentration in the substratum, though the latter varied only in the range of a few μmol g−1 between the sample trees. Variability of lichen substance concentrations in H. physodes within the individual trees was low. Among the different lichen substances of H. physodes, the amount of the depsidone physodalic acid relative to the total of lichen substances was most closely correlated to the concentrations of Cu and Mn in the substratum, whereas the amount of the depsidone 3-hydroxyphysodic acid decreased both with increasing concentrations of these two metals and physodalic acid. Thus, our data suggest that lichen substances contribute to metal homeostasis not only in heavy metal-rich habitats, but also at not or low-polluted sites where the lichen substances apparently help to maintain constant intracellular metal concentrations despite of spatially varying availabilities of metal ions
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