Epixylic Species Research Articles

The effect of light conditions on herbs, bryophytes and seedlings of temperate mixed forests in Őrség, Western Hungary

The effect of light on different understory plant groups (herbs, ground floor bryophytes, trunk-dwelling bryophytes and seedlings) was studied in a deciduous–coniferous mixed woodland in Western Hungary. The correlation of cover and species richness in each group and the cover of individual species to relative diffuse light were analyzed at different spatial scales. The study was carried out in 34 forest stands with different tree species composition. The importance of light in determining species composition was investigated by redundancy analysis. Species within each plant group were classified based on their light response. Light was positively correlated with species richness of herbs, cover of ground floor and trunk-dwelling bryophytes, and species richness and cover of seedlings. In redundancy analysis, the variance explained by light was 13.0% for herbs, 15.0% for bryophytes and 8.6% for seedlings. Within the group of herbs, species preferring open conditions and light-flexible (gap) species were separated on the basis of the spatial scale of the analysis, while shade-tolerant species were not correlated positively with light. Among bryophytes mainly terricolous, opportunistic and mineral soil-inhabiting species showed significant positive correlations with light, while epiphytic and epixylic species did not respond to light. Seedlings of Quercus petraea and Pinus sylvestris were positively related to light, while most other seedling species were shade-tolerant. In case of vascular plants, the species’ correlations with light were in agreement with their light indicator values; however, they were independent in the case of bryophytes. This study proved that the extent and spatial pattern of light influenced strongly the understory plant groups. Species within each group respond to light conditions differently, concerning the strength, direction and spatial scale of the relationships.

Partial cutting as a conservation alternative for oak ( Quercus spp.) forest—Response of bryophytes and lichens on dead wood

Semi-open oak-rich forests may support many species adapted to large trees and coarse woody debris. Currently many oak-rich forests in northern Europe have more or less closed canopies due to lack of natural and cultural disturbances. In these forests, conservation oriented partial harvesting of biofuel may restore a desired forest structure and light regime that potentially may favour many species that have declined during the last century. We quantified effects of such cutting on lichens and bryophytes living on dead wood in southern Sweden, using a design with paired cutting and control plots (each 1 ha) in 15 forests. In each plot we surveyed the same five logs and three stumps before and after harvest (25% of the tree basal area removed). The epixylic species composition shifted towards a flora typical for dryer dead wood. The mean species number of lichens per stump increased (clear effect) and the mean number of bryophytes per stump decreased (nearly significantly) due to harvesting. The species composition, but not species richness, on logs was affected. No increases or decreases in species of conservation concern could be detected. Since the overall negative effects were weak, we suggest that partial harvesting of dense oak forests is compatible with maintenance of the diversity of lichens and bryophytes on dead wood. However, the amount of such forest harvested needs to be carefully assessed in relation to demands of other taxa.

Patterns of epixylic vegetation on spruce logs in late-successional boreal forests

There is a wide diversity in composition and structure of epixylic vegetation that depends on the stage of overgrowing, species of logs, ecological conditions, geographical position and random factors. We analyzed vegetation on spruce logs in the late successional spruce forests of the Sphagnum– Myrtillus, Myrtillus and Oxalis types in northwestern Russia. Vascular plants, lichens, hepatics and mosses constitute, respectively, 18, 17, 21 and 44% of the flora on the decaying wood. The total number of species increases from the first to the second stage of overgrowing, and then decreases at the fourth stage. However, the number of species per plot barely changes. The dynamics of epixylic species and generalists depend on the phytosociological conditions. The described sequences of vegetation are divided into three types of microsuccession. The first type is characterized by the dominance of the epiphytes in the early stages and the epigeous species in the late stages. The low abundance of generalists and epixylics is observed in the spruce forests with well-developed ground feather moss cover. The second type of microsuccession has a small coverage and number of epigeous species and a significant share of generalists on the latter stages of overgrowing. It is connected with the herb-rich, mainly deciduous forests. The third type of microsuccession includes one more stage where one group of ground flora mosses (green mosses) is replaced with another one ( Sphagnum). This is characteristic for the Sphagnum– Myrtillus type of spruce forests.

Bryophyte responses to fragmentation in temperate coastal rainforests: A functional group approach

The species richness and frequency of occurrence of bryophytes within taxonomic and functional groups was examined in relation to the size of 20 old-growth patches (size range: 0.6–63.6 ha) remaining after logging in temperate rainforests of coastal British Columbia. At the centre of each remnant patch, bryophytes were sampled in sixty-three 10 cm × 30 cm microplots on three substrate-types (forest floor, downed logs and tree bases). Generalized linear models demonstrated that the species richness and frequencies of some bryophyte functional groups were related to patch size. In particular, some dispersal-limited groups (perennial stayers) and microclimate-sensitive groups (closed canopy species, epixylic (log-dwelling) species, and liverworts) showed significant declines in either richness or frequency as patch size decreased. In contrast, colonists and open canopy species showed little association with patch size. Many, but not all, of the significant patch size relationships disappeared when the three smallest patches (0.6–1.8 ha) were eliminated from the analysis. These results suggest that patches sized 3.5 ha or larger may provide habitat capable of sustaining a diverse array of bryophyte functional groups in temperate rainforest landscapes.

Seasonal growth and dynamics of epixylic bryophytes in Bohemian old-growth forest

Seasonal patterns in growth and dynamics of 13 epixylic bryophyte species (six liverworts and seven mosses) were studied within permanent plots in the Žofínský prales old-growth forest in south-eastern Bohemia, Czech Republic. Transparencies were used to record positions and cover of bryophyte colonies within each plot twice a year (in spring and autumn) for periods of 1–4 years. Percentage growth of species populations and growth dynamics of their colonies were analysed in order to identify seasonality in their growth. Establishment of bryophyte colonies and their expansion, as well as pair-wise overgrowth of adjacent colonies of different species were compared in order to identify competitive interactions between bryophyte species. Bryophytes grew faster during the winter season (October–April) than during summer, and the various species did not differ in their percentage growth. The growth dynamics of bryophyte colonies was highly seasonal and the species differed in their dynamics pattern. The expansion and retreat (local extinction) of bryophyte species were greatest in winter, and the stability of colonies was, therefore, higher in summer. Interspecific competition among the species studied appears to be low.

Diversity and composition of dead wood inhabiting bryophyte communities in European beech forests

Species composition and diversity of bryophyte communities occurring on dead beech trees were analyzed in five European countries (Slovenia, Hungary, The Netherlands, Belgium and Denmark). Altogether 1.009 trees were inventoried in 19 beech dominated forest reserves. The differences in the composition of bryophyte communities were high among countries and it overwhelms the effect of decay stages, which affect the species com-position at local scale. Well decayed trees were dominated by epixylic species in Slovenia, while in other countries the proportion of opportunistic bryophytes was much higher and in Atlantic countries uproot species are also common. In Slovenia hepatics, in Hungary and Denmark pleurocarps, and in The Netherlands and Belgium acrocarps were the most fre-quent. Diversity of communities differed considerably among regions. Slovenian sites were the hotspot of bryophyte diversity characterized by high species richness (both tree and country level) and a high fraction of rare and threatened species. This richness is most likely caused by the combination of high air humidity combined with a very high degree of natu-ralness of the Slovenian sites. The diversity of Hungarian stands was intermediate reflecting the relatively high naturalness of the study sites, as well as a rather continental climate sub-optimal for epixylic liverworts. Atlantic forests have deteriorated bryophyte communities on dead trees, dominated by a few opportunistic species. This is partly a result of habitat frag-mentation and past and recent management of forest. Most of the stands the amount and quality of dead wood is not suitable for species rich epixylic bryophyte communities.

Preferences of dead wood inhabiting bryophytes for decay stage, log size and habitat types in Hungarian beech forests

This study describes the quantitative preferences of epixylic bryophytes for decay stages, log size and habitat type. The two habitats investigated were zonal (situated on plateaux without extreme microclimatic conditions) and ravine-like near-natural beech stands. Preferences of 30 bryophyte species are described using logistic regression modelling. The species pool differed between habitat types. In the ravine-like forests more species are found. Regionally rare epixylic species (mainly liverworts) were limited to these forests. The species richness of individual logs was also higher in the ravine-like than in the zonal forests and the proportion of logs of all sizes colonized by bryophytes was higher in the former. The species were classified into four categories on the basis of their preference for decay stages: strict epixylics, indifferent species, preferential epixylics and epiphytes. The epixylics and preferential epixylics prefer advanced decay stages while the latter extend further into earlier decay stages than strict epixylics. Common epixylic species have a wider tolerance to decay stage than rare ones. Probabilities of species occurrence increase with log size, more strongly in zonal stands than in ravines. A simple successional scheme for bryophyte succession on dead wood is proposed on the basis of the observed species responses.

Composition and ecology of macrofungal and myxomycete communities on oak woody debris in a mixed-oak forest of Ohio

Woody debris is recognized as an important structural component in forests, but little is known about the epixylic communities that it supports in many forest types. The goal of this study was to identify the macrofungal (asco mycetes and basidiomycetes) and myxomycete communities found on woody debris in the topographically dissected mixed-oak forests of southern Ohio and identify environmental parameters that influence species richness and species distributions. Fifty oak (Quercus spp. L.) logs were selected across slope aspects and slope positions throughout the landscape to maximize microsite variability. Over a 2-year period, 130 epixylic species were collected (28 ascomy cetes, 72 basidiomycetes, and 30 myxomycetes). Log surface area explained a significant amount of variation in species richness (R2 = 0.51, P < 0.001). Richness was significantly (P < 0.05) correlated with volume of woody debris in the plot (+) and with study log volume (+), lichen cover (–), and surface structural characteristics (amount of bark (+), solid wood (–), and fragmented wood (+)). Canonical correspondence analysis revealed that slope aspect, bark cover, percent slope, and woody stem density influenced individual epixylic species distributions. Because of their influence on epixylic communities, various environmental parameters must be accounted for in regional epixylic studies.

The occurrence of epixylic bryophyte and lichen species in an old natural and a managed forest stand in Northeast Sweden

An old natural spruce stand and a managed spruce stand were compared with regard to occurrence of epixylic bryophyte and lichen species and amount of decaying wood in different size classes and decay stages. Epixylic hepatics occurred more frequently in the natural stand while Cladonia species were predominant in the managed stand. This difference is explained by differences in humidity regimes, with the managed stand exposed to drought more often than the natural stand. The managed stand also had a more uneven supply of logs in different decay stages with some stages almost missing. Wood in advanced stages of decomposition was scarce and occurred mostly as stumps in the managed stand. These two factors, substrate shortage and humidity regimes, may explain why only the most drought-resistant of the epixylic species preferring well-decayed wood were found. It is concluded that drought-sensitive bryophytes growing on logs in intermediate stages of decay are among the species most threatened by modern forest management.