B1) Epiphyte & Microhabitat Diversity
Epiphyte and microhabitat diversity and function on habitat trees
Markus Hauck 1 & Stefan Kaufmann 1 (since 2019)
Albert Reif 2 (until 2019) & Stefanie Gärtner 3 (until 2019)
Doctoral researchers: Diane Stevenson 2 (since 2016), Dina Emrich 1(since 2019)
& Theresa Möller 1 (since 2022)
1 University of Freiburg, Faculty of Environment & Natural Resources, Institute of Forest Sciences,
Chair of Applied Vegetation Ecology
2 University of Freiburg, Faculty of Environment & Natural Resources, Institute of Forest Sciences,
Chair of Site Classification and Vegetation Science
3 National Park Black Forest, Working Group Conservation of Processes & Development of Vegetation
Background
Epiphytic lichens and bryophytes respond more sensitively to changes in the site condition of forests than vascular plants. This applies both to natural fluctuations in site conditions in the course of forest aging and disturbance dynamics and to the impact of anthropogenic disturbance, including effects of forest management or air pollutants.
A key reason for the high responsiveness of epiphytic lichen and bryophyte species richness and species composition to changes in the forest structure and in forest management is their direct dependence on trees and deadwood, whereas the forest floor vegetation is only indirectly affected via changes in microclimate and soil conditions.
Epiphytic lichens and bryophytes are also heavily affected by forest fragmentation and the disruption of habitat continuity as the result of dispersal limitations and edge effects. Old large-diameter trees and deadwood are usually particularly rich in epiphyte species because they offer special microhabitats and long habitat continuity.
Research questions and hypotheses
The role of habitat trees (defined as trees of an age and tree diameter that is clearly above the stand average) for conserving the total forest epiphyte diversity will be quantified by the comparative study of habitat trees and ‘average’ trees that represent the typical tree diameter and tree species of the stand. Using the complete plot design of 135 sample plots, we will address the questions how habitat trees differ in their epiphytic lichen and bryophyte diversity from the remaining forest stand in variation of
(1) the species identity of the habitat tree,
(2) the main tree species of the stand,
(3) the diameter and microhabitat characteristics of the habitat tree, and
(4) forest connectivity. We will further analyse how these factors interact with elevation, aspect, and tree species richness.
Our key hypotheses include:
(1) Habitat trees are generally richer in epiphytic lichens and bryophytes both in terms of species richness (α-diversity) and turnover (β-diversity) than the average trees of a stand.
(2) The epiphytic lichen and bryophyte species richness of habitat trees is strongly dependent on tree species identity.
(3) The tree species composition of the surrounding stand exerts a significant influence on the epiphyte diversity of the habitat tree.
(4) Broad-leaved habitat trees in conifer-dominated forest stands contribute disproportionally to the epiphyte diversity of the total stand.
(5) High forest connectivity has a beneficial influence on the epiphyte diversity of habitat trees.
(6) The increase in epiphytic lichen and bryophyte diversity with elevation is steeper in conifers than in broad-leaved trees.
(7) Habitat trees with high lichen and bryophyte species richness differ from other trees in structural, microclimatic and chemical site conditions.
Approach, methods and linkages
Based on the stand structural data from A2, the 5 habitat trees with the highest diameter at breast height (dbh) will be selected on every plot. These trees will be compared with 5 ‘average’ trees representing the respective plot’s most common tree species close to the mean dbh of these trees in that plot. The average trees will be selected by choosing the closest tree from each sampled habitat tree, which (1) belongs to the plot’s most common tree species and (2) has a dbh equalling the stand’s mean dbh (± 15 %). In accordance with many other studies of our group, e.g. references, all epiphytic lichens and bryophytes at a stem height of 0-2 m above the ground will be recorded and their cover will be estimated in percent classes.
Limiting the vegetation survey to the lower 2 m of the trunk, which are easily accessible from the ground, is necessary to cope with the high number of sample trees. Based on our previous work in primeval Fagus sylvatica forests, we expect that this limitation will lead to an underestimation of total epiphytic bryophyte species richness on the sample plot by 10 %. For lichens, which are less restricted to the tree base than bryophytes due to their different ecology (i.e. the lower moisture demand of most lichen species), the underestimation will be much higher. Nevertheless, the plot level diversity patterns are little influenced by the restriction of vegetation sampling to the lowest 2 m of the stem. Light microscopy and thin-layer chromatography will be employed for species identification.
The results can be linked to the other biodiversity work packages (B2-B6, B8-B9) to analyse diversity patterns across different organism groups. We are especially interesting in analyzing common and divergent patterns of lichens and bryophytes with fungi (B9) and vascular plants (B2), but also with insects (B3, B4) and vertebrates (B4, B5, B8). We will closely cooperate with A1 and A2 to integrate their stand structural data into our analyses. Our results can furthermore be used (together with other biodiversity data) as the basis of analyses in the C and D modules, for example, by verifying stakeholder perceptions that are surveyed in C2.
ConFoBi publications by B1
Kaufmann, Stefan; Funck, Sarah-Katharina; Paintner, Franziska; Asbeck, Thomas & Hauck, Markus (2021). The efficiency of retention measures in continuous-cover forestry for conserving epiphytic cryptogams: A case study on Abies alba. Forest Ecology and Management, 502, 119698. www.doi.org/10.1016/j.foreco.2021.119698.
Wirth, Volkmar; Tønsberg, Tor; Reif, Albert; Stevenson, Diane (2018): Loxospora cristinae found in Germany. Herzogia 31: 995. https://doi.org/10.13158/heia.31.2.2018.995
