Impacts of silvicultural practices on the structure of hemi-edaphic macrofauna community

This research determined the influence of six conventional forest management systems on litter-dwelling macrofauna. The forests differed in structure (patch size) and tree composition. Pitfall trapping was carried out in a total of 128 managed stands in the Belgian Ardennes in 1999. We measured the biomass (dry weight) of predators (Arachnida, Carabidae, Staphylinidae and Chilopoda), phytophages (Curculionidae, Homoptera and Elateridae) and detritivores (Lumbricidae, Isopoda and Diplopoda) in young, medium-aged and mature stands in each of the six forest management systems.The major part of the predator biomass consisted of Carabidae in closed-canopy stages and of Arachnida in the regeneration stage. The main phytophagous group trapped was Curculionidae, except in large regenerating stands where Homoptera showed a higher biomass.With respect to forest succession, we obtained higher detritivore biomass in regenerating stands, especially in large ones, higher phytophage biomass in medium-aged stands and higher predator biomass in mature stands.In terms of forest composition, the richest stands as far as biomass and abundance were concerned, were oak forests where predators and detritivores were well represented, followed by coniferous and mixed forests (phytophages). Beech forests appeared to shelter the lowest abundance and biomass of litter-dwelling macro-invertebrates. This impoverishment is partly due to the less favourable edaphic conditions, but also to the silvicultural practices in these forests.When analysing biomass in terms of forest structure, the size of clear-cut patches was one of the most important features distinguishing even-aged and uneven-aged stands.     

Effects of forest stand type on oribatid mite (Acari: Oribatida) assemblages in a southwestern Quebec forest

Despite the ubiquity of oribatid mites in soil and litter systems, and their importance in decomposition and nutrient cycling processes, little is known of the factors underlying the composition of their assemblages. Our objective was to address this by determining how oribatid assemblage composition changes by forest stand type. This work was done in and near a hardwood forest in southwestern Quebec, Canada. We sampled mites by collecting 1 L of litter and 170 cm³ of soil from four sites in each of four distinct habitat types: American beech stands, sugar maple stands, mixed deciduous stands and mixed conifer plantations. Samples were collected in July and September 2005, and June 2006, and over 6500 oribatid mites were collected and identified to species. Abundance and species richness differed between forest types: for abundance conifer>beech>maple>mixed deciduous while for species richness beech and conifer>maple>mixed deciduous. Ordination analyses revealed that conifer plantations and beech stands supported distinct assemblages, while there were some overlap in the assemblages found in maple stands and mixed deciduous stands. These data support the importance of aboveground plant communities in affecting the composition of oribatid assemblages even at local scales and provide insight into additional impacts that may be caused by shifts in plant species ranges due to global changes.     

Timber harvesting alters soil carbon mineralization and microbial community structure in coniferous forests

Timber harvesting influences both above and belowground ecosystem nutrient dynamics. Impact of timber harvesting on soil organic matter (SOM) mineralization and microbial community structure was evaluated in two coniferous forest species, ponderosa pine (Pinus ponderosa) and lodgepole pine (Pinus contorta). Management of ponderosa pine forests, particularly even-aged stand practices, increased the loss of CO₂-C and hence reduced SOM storage potential. Changes in soil microbial community structure were more pronounced in ponderosa pine uneven-aged and heavy harvest stands and in lodgepole pine even-aged stand as compared to their respective unmanaged stands. Harvesting of trees had a negative impact on SOM mineralization and soil microbial community structure in both coniferous forests, potentially reducing coniferous forest C storage potential.     

Influence of tree characteristics and forest management on tree microhabitats

Higher densities of tree microhabitats in unmanaged forests may explain biodiversity differences with managed forests. To better understand the determinants of this potential biodiversity indicator, we studied the influence of tree characteristics on a set of tree microhabitats (e.g. cavities, cracks, bark features) on 75 plots in managed and unmanaged French forests. We hypothesized that the number of different microhabitat types per tree and the occurrence of a given microhabitat type on a tree would be higher in unmanaged than in managed forests, and that this difference could be linked to individual tree characteristics: diameter, vitality and species. We show that unmanaged forests contained more trees likely to host microhabitats (i.e. large trees, snags) at the stand level. However, at the tree level, forest management did not influence microhabitats; only tree characteristics did: large trees and snags contained more microhabitats. The number and occurrence of microhabitats also varied with tree species: oaks and beech generally hosted more microhabitats, but occurrence of certain types of microhabitats was higher on fir and spruce. We conclude that, even though microhabitats are not equally distributed between managed and unmanaged forests, two trees with similar characteristics in similar site conditions have the same number and probability of occurrence of microhabitats, whatever the management type. In order to preserve biodiversity, foresters could reproduce unmanaged forest features in managed forests through the conservation of specific tree types (e.g. veteran trees, snags). Tree microhabitats could also be more often targeted in sustainable forest management monitoring.     

Spruce forest conversion to a mixed beech-coniferous stand modifies oribatid community structure

We investigated oribatid mite community diversity and structure in the managed conversion of coniferous stands into semi-natural montane forests that are composed of a small-scale mosaic formed by different age classes of silver fir, Norway spruce and European beech in the southern Black Forest area, South-Western Germany, using the space-for-time substitution method. The core hypothesis was that changing tree composition and management practice will affect functional structure and diversity of oribatid mite community through changing substrate quality and litter diversity. Three forest districts were selected within the research region. Four stand types representing the major stages of forest conversion were selected within each forest district: (i) even-aged spruce monocultures, (ii) species enrichment stage, (iii) forest stand structuring stage, at which fur and beech and other deciduous trees penetrate the upper storey of the forest and (iv) a diverse continuous cover forest respectively. Oribatid mite abundance, species richness and composition, biomass, ecomorphs and feeding groups relative abundance were determined. An overall increase in species richness moving from the spruce monoculture to a continuous cover forest was detected. However, the herbivorous and litter-dwelling mites were most sensitive to forest conversion demonstrating significant differences in abundance between conversion stages. Almost all changes in the oribatid community were associated with the properties of the changing litter layer. Abundance of soil-dwelling mites remained very stable what is in contradiction with the response of the other soil fauna groups found at the same sites. Overall oribatid community seemed to be more dependent on total microbial biomass than fungi. However, observed effects were overshadowed by considerable district-induced differences.     

Does forest continuity matter in conservation? - A study of epiphytic lichens and bryophytes in beech forests of southern Sweden

The effects of forest continuity at local scale for red-listed and indicator species of epiphytic lichens and bryophytes were investigated in 150 Fagus sylvatica stands in southern Sweden. Stands having forest continuity (n = 106) had continuous forest cover more than 350 years, whereas stands lacking continuity (n = 44) had forest cover less than 160 years. Forest continuity was identified by comparing a sequence of historical maps with a modern survey of beech forests. In the field woody beech substrates were searched for the epiphytes of interest. A number of environmental and spatial variables were inventoried and compiled for each stand. In all 64 species (51 lichens, 13 bryophytes) were found in the stands having continuity, and 21 (14 lichens, 7 bryophytes) in the stands lacking continuity. Controlling for the different number of surveyed stands, stands having continuity had significantly more species of lichens, but not of bryophytes. In the stands lacking continuity we did not find lichens associated with the very late succession stage. The quantity of substrates, stand age and forest continuity were the three most important factors explaining species richness as well as composition of studied epiphytes. The effect of continuity was probably due to a combination of a higher substrate quality, mainly old beeches, and a longer time available for colonization. Also, we found strong positive correlations between number of indicator and red-listed epiphyte species. In short-term conservation old stands having continuity, containing suitable substrates and indicator species are target areas.     

Openness in management: Hands-off vs partial cutting in conservation forests, and the response of beetles

The appropriate management of forest reserves is debated; two major alternatives are succession to ‘wild’ state, or management to produce semi-open stands. For temperate conservation stands, there are no strong experiments replicated at landscape level. In each of 22 forests rich in oaks (Quercus spp.) in Sweden, we set up a closed-canopy wild plot (1 ha), and a cutting plot (1 ha) to produce semi-open conditions, studying them before and after cutting. About 25% of the tree basal area was cut (large trees and dead wood retained) and harvested as bio-fuel, a CO₂ - neutral energy source. We examined the response of beetles and trapped 59,000 individuals (1174 species; 100 red-listed species). For both the guild of herbivorous beetles (222 species) and of saproxylic beetles connected to oak wood (267 species), species richness increased by about 35% in the harvested plots, relative to the wild reference plots. Species composition within the groups changed, though not strongly. Thirteen saproxylic species of 50 analysed, and three herbivores of 12 increased in cutting plots. For red-listed saproxylic beetles, species richness did not change significantly. Regression analyses suggest that more open cutting plots disfavour the red-listed beetles of this forest type. Thus, partial cutting increased species diversity of two beetle groups, probably due to changed microclimate and increase in herbaceous plants, but some red-listed saproxylic beetles may be disfavoured. A hands-off alternative may through storms and other disturbances produce open patches, more dead wood, and favour some species. Combinations of these alternatives, carefully planned at the landscape level, need to be considered.     

Woodpeckers as reliable indicators of bird richness, forest health and harvest

Woodpeckers (family Picidae) show promise as indicators of avian diversity in forests because their populations can be reliably monitored, and their foraging and nesting activities can positively influence the abundance and richness of other forest birds. A correlation between woodpecker richness and richness of forest birds is known to exist at the landscape scale, but uncertainty remains whether this correlation occurs at the smaller stand-level spatial scales where forest management activities take place. We used data collected under a diverse range of forest types, harvest treatments, and forest health conditions during a long-term study of bird communities in interior British Columbia, Canada, to examine two basic questions: (1) at the level of individual forest stands, is woodpecker richness correlated with bird richness (measured as richness of all other bird species)? and (2) do woodpecker richness and bird richness have similar habitat correlates? Bird richness was positively correlated with woodpecker richness (β = 0.59, SE = 0.22, 95% CI = [0.14 1.03]). Richness of both woodpeckers and all other birds were positively correlated with tree species richness and negatively correlated with density of pines, and the effect for forest harvest type was similar for both measures of avian richness (uncut < partial harvest < clearcut with reserves). The effect of density of lodgepole pines killed by mountain pine beetles differed between the two richness measures, being positive for woodpecker richness and negative for forest bird richness. We conclude that the richness of woodpeckers is indeed correlated with the richness of other birds at the stand-level, and can serve as a reliable indicator of overall bird richness in most forest stands and conditions, except during insect outbreaks when differential responses by woodpeckers and the rest of the avian community may decouple the relationship between bird richness and woodpecker richness.     

The effects of forest patch size and matrix type on changes in carabid beetle assemblages in an urbanized landscape

In this study we compared ground beetles (Carabidae) from a range of different forest fragments along an urbanization gradient in Brussels, Belgium. We address the following questions: (i) How does the degree of urbanization in the surrounding habitat affect forest beetles, and does it interact with the effects of patch size and distance to forest edge? (ii) Do these factors have a different effect at the level of individual species, habitat affinity groups or total community? During 2002 we sampled 13 forest plots in 10 forest patches, ranging in size from 5.27 to 4383 ha. The beetles were captured using transects of pitfall traps from the edge to a distance of 100 m into each woodland and identified to species level. Effects of urbanization, forest size and forest edge were evaluated on total species number, abundance and habitat affinity groups and ten abundant, widespread model carabid species. Overall, the effects of urbanization, forest size and edge effects slightly influenced total species richness and abundance but appeared to have a major effect on ground beetle assemblages through species specific responses. More urbanized sites had significantly fewer forest specialists and more generalist species. Large forest fragments were favoured by forest specialist species while generalist species and species frequently associated with forest (forest generalists) dominated the smaller forests. Forest edges mainly harboured generalist species while forest specialist species were more frequent into the forests if the forest patches were large enough, otherwise they disappeared due to the destruction or impoverishment of their habitat. Our results show the importance of differentiating between habitat affinity, especially habitat generalists versus specialists, the latter having a higher value in nature conservation, and merely the quantity of species represented in human-dominated areas.     

Cost-effectiveness of silvicultural measures to increase substrate availability for red-listed wood-living organisms in Norway spruce forests

It is important that measures to maintain biodiversity are taken in a way that is cost-effective for the landowner. We analyzed the cost-effectiveness of silvicultural measures that aim at increasing the substrate availability for red-listed (species that are threatened, near threatened or where species probably are threatened but data is deficient) saproxylic (wood-inhabiting) organisms. We modelled stands of Norway spruce (Picea abies) in three regions of Sweden by using computer simulations and a database with substrate requirements of saproxylic beetles and cryptogams on the Swedish Red-List. Conclusions concerning cost-effectiveness of silvicultural measures depend on the extinction thresholds of the species they are intended to conserve; measures that generate only small amounts of coarse woody debris (CWD) may provide too little substrate to be useful for species with high extinction thresholds. In northern Sweden, forestland is relatively inexpensive, so a cost-effective strategy to increase the amount of spruce CWD was to set aside more forests as reserves. In central and southern Sweden, more emphasis should instead be given to increasing the amount of CWD in the managed forest. The regulations by the Forest Stewardship Council (FSC) could be made more cost-effective by prescribing creation of more high stumps and retention of larger amounts of naturally dying trees. Large-sized CWD, CWD from slow-growing trees, and CWD in late decay stages are substrate types that were particularly rare in managed forest in relation to unmanaged forests. Manual soil scarification and retention of living trees are measures that can increase the proportion of these underrepresented CWD types.     

Changes in humus properties and collembolan communities following the replanting of beech forests with spruce

Differences of collembolan communities within the organo-mineral A layer were studied in relation to physico-chemical changes in humus at nine sites of beech forests (Fagus sylvatica L.) and first generation spruce stands (Picea abies (L.) Karst.), planted on former beech forest 30 years ago (Central Pyrenees, France). Changes in humus form were caused by the spruce plantation and occurred mainly within the fermentation horizon where acidifying litter accumulation increased the horizon depth. The recent replacement of beech by spruce induced a shift from mull towards moder humus forms, which is explained by the decreasing organic matter turnover rate. A significant decrease in the three exchangeable cations and pH under spruce was also observed. Collembolan species diversity within the A horizon was significantly lower under spruce at this early stage of the silvogenetic cycle. Differences between species composition of Collembola between the two forest stands is related to changes in environmental conditions (e.g. nutrient availability, soil porosity, soil moisture). This study shows how forest management practices are susceptible to modify biological activity within the A horizon under exotic conifer plantations.     

Learning from a “benign neglect strategy” in a national park: Response of saproxylic beetles to dead wood accumulation

Increasing demands for firewood owing to rising energy costs have accelerated discussions about the amount of dead wood needed for conservation. A sharp increase in dead wood caused by bark beetles in a German national park provides lessons for management of commercial and protected forests. We investigated the effects of dead wood due to bark beetle infestation as well as tree senility on abundance and richness of saproxylic species of beetles. Increasing amounts of spruce dead wood and opening of the canopy by bark beetles had positive effects on the abundance of host-generalist, conifer-specialist, and red-listed saproxylic beetles. Broadleaf specialists were positively associated with the amount of broadleaf dead wood and negatively associated with canopy openness. Gradient analysis of beetle assemblages revealed two major environmental axes: canopy openness and amount of dead wood. We found a threshold for community divergence at a canopy openness of 23% (confidence interval CI: 11-49) and at an amount of dead wood of 64 m³ ha⁻¹ (CI: 35-160). Critically endangered species served as indicators of dense and open forests, but only when the amount of dead wood was high. Our results suggest that, to maintain saproxylic beetle assemblages, the amount of dead wood in commercial montane forests (at present ≈15 m³ ha⁻¹) needs to be tripled, with a focus on broadleaf wood in dense stands and spruce wood in open stands. For large protected areas in Europe, our data suggest that bark beetle infestation and senescence without active forest management improves habitat conditions for saproxylic beetles.     

Management intensity affects traits of soil microarthropod community in montane spruce forest

This study examined the influence of forest management intensity (3 unmanaged, 3 mild managed, 5 intensively managed stands) on soil microarthropods in montane spruce forest. We particularly focused on Oribatida and Collembola which play important roles in organic matter decomposition and nutrient cycling. Our results showed a significant shift from fungivory and carnivory to detritivory in the Oribatida community accompanying management intensification. Similarly, parthenogenetic oribatid mite species contributed more to the community in intensively managed forests and the presence of Collembola species with developed furca increased with management intensification. Although there was no remarkable influence of management intensity on total densities or diversity indices, important and significant shifts in species composition and functional groups showed that soil functions and processes were affected by forest management. Trait assessment indicates a shift in roles Oribatida play in decomposition; fragmentation and comminuting of undecomposed litter seems to gain importance in the intensively managed forest, whereas fungivorous species affect primary decomposers through feeding on fungi in the unmanaged forest.     

Long-term impacts of even-aged timber management on abundance and body condition of terrestrial amphibians in Northwestern California

Conservation needs for amphibians in managed timberlands may differ based upon the species present and the timber harvesting methods employed. Clearcuts have been documented to be detrimental to amphibians but the impacts of associated silvicultural edges and alternative harvesting treatments are not well understood. The primary objective of this study was to determine if amphibian abundances and body condition differed in thinned forests and intact forests, and in clearcuts and associated silvicultural edges. We also examined which environmental attributes were important in explaining observed differences. We sampled clearcuts, silvicultural edges, and adjacent late-seral forests at 10 sites in northwestern California from October 1999 to July 2002. Clearcuts at these sites ranged in age from 6 to 25 years. Five of these forest stands were intact and five had been commercially thinned at least 10 years prior to our study. Amphibian abundances were similar in thinned and unthinned forests, but body condition of the most common species was lower in thinned forests. Abundances of amphibians were nearly twice as high in forests and at silvicultural edges than in clearcuts. Clearcutting at these sites appears to have affected amphibian numbers up to 25 years post-harvest, however, silvicultural edges were suitable habitats for amphibians. While commercial thinning did not reduce amphibian numbers, it is an intermediate treatment followed by clearcutting. Where conservation of amphibians is a concern, even-aged silvicultural systems may not provide the most appropriate method for maintaining viable populations on managed forestlands in the northwestern US.     

自然再生、非管理、伐光的山毛榉林丛枝菌根真菌的浸染性研究

Clear-cutting,a management practice applied to many beech forests in the North of Spain,modifies microclimate and,consequently,the composition of the understory plant community in the disturbed areas.The objectives of this study were to assess if changes in the understory vegetation caused by altered light microclimate after clear-cutting affect the infectivity of arbuscular mycorrhizal fungi(AMF) on herbaceous plant species in beech(Fagus sylvatica L.) forests naturally regenerating from clear-cutting and to test if the use of bioassays for studying the infectivity of native AMF could provide useful information to improve the management of clear-cut areas.Three nearby beech forests in northwest Navarra,Spain,a region in the northwest part of the Pyrenees,were selected:an unmanaged forest,a forest clear-cut in 1996,and another forest clear-cut in 2001.High stem density in the forest clear-cut in 1996(44 000 trees ha -1) attenuated photosynthetic active radiation(PAR) and impaired the growth of herbaceous species within the ecosystem.The percentage of AMF colonization of plants in bioassays performed on soil samples collected from the forest clear-cut in 1996 was always lower than 10%.In the forest clear-cut in 2001,where soil was covered by perennial grasses,PAR was high and the infectivity of native AMF achieved minimum values in spring and autumn and a maximum value in summer.In contrast,the infectivity of native AMF in the unmanaged forest remained similar across the seasons.Our results demonstrated that changes in the composition of understory vegetation within beech forests strongly affected the infectivity of native AMF in clear-cut areas and suggested that the assessment of the infectivity of native AMF through bioassays could provide helpful information for planning either the removal of overstory when the tree density is so high that it impairs the correct development of herbaceous species or the plantation of new seedlings when high light intensity negatively affects the establishment of shade species.     

The effect of stand structure and tree species composition on epiphytic bryophytes in mixed deciduous-coniferous forests of Western Hungary

The effect of tree species, stand structure, landscape and historical variables was studied on the species composition, species richness and cover of epiphytic bryophyte assemblages in mixed deciduous-coniferous forests of Western Hungary. Stand and tree level assemblages were analyzed by ordinations and generalized linear modeling in 35 70-110 year old stands of different management regimes.Bryophytes showed a considerable preference to different host trees, so that stand level diversity of bryophyte assemblages was determined mainly by tree species diversity, and their composition by tree species composition. Cover and diversity of epiphytic bryophytes were the highest on oaks (Quercus petraea and Quercus robur), and the lowest on Scotch pine (Pinus sylvestris). The presence of sapling (shrub) layer increased, whereas a large number of medium sized trees decreased bryophyte species richness in this study. Tree size was much less influential which is explained by the lack of large, veteran trees. Forest management maintaining tree species diversity, structural heterogeneity and temporal continuity of the stands could considerably contribute to the conservation of this organism group. Selective cutting is more appropriate for these conservational purposes than shelterwood management system.     

Use of remnant boreal forest habitats by saproxylic beetle assemblages in even-aged managed landscapes

Saproxylic Coleoptera are diverse insects that depend on dead wood in some or all of their life stages. In even-aged boreal forest management, remnant habitats left as strips and patches contain most of the dead wood available in managed landscapes and are expected to act as refuges for mature forest species during the regeneration phase. However, use of remnant habitats by the saproxylic fauna has rarely been investigated. Our objective was to characterize the saproxylic beetle assemblages using clearcuts and forest remnants in western Québec, Canada, and to explore the effects of forest remnant stand characteristics on saproxylic beetle assemblages. We sampled both beetle adults and larvae, using Lindgren funnels and snag dissection, in five habitat locations (clearcuts, forest interiors of large patches, edges of large patches, small patches and cut-block separators) from three distinct landscapes. Adult saproxylic beetles (all feeding guilds combined) had significantly higher species richness and catch rates in small patches compared to forest interiors of large patches; the phloeophagous/xylophagous group had significantly higher species richness only. Small patches, cut-block separators and edges of large patches also had the highest snag density and basal area, increasing habitat for many saproxylic beetles. No significant differences in density of saproxylic larvae were found between habitat patches, but snag dissection nevertheless suggests that snags in forest remnants are used by comparable densities of insects. Saproxylic beetles appear to readily use habitat remnants in even-aged managed landscapes suggesting that forest remnants can insure the local persistence of these species, at least in the timeframe investigated in our study.     

Composition of the microbial communities in the mineral soil under different types of natural forest

Phospholipid fatty acid (PLFA) patterns were used to describe the composition of the soil microbial communities under 12 natural forest stands including oak and beech, spruce-fir-beech, floodplain and pine forests. In addition to the quantification of total PLFAs, soil microbial biomass was measured by substrate-induced respiration and chloroform fumigation-extraction. The forest stands possess natural vegetation, representing an expression of the natural site factors, and we hypothesised that each forest type would support a specific soil microbial community. Principal component analysis (PCA) of PLFA patterns revealed that the microbial communities were compositionally distinct in the floodplain and pine forests, comprising azonal forest types, and were more similar in the oak, beech and spruce-fir-beech forests, which represent the zonal vegetation types of the region. In the nutrient-rich floodplain forests, the fatty acids 16:1ω5, 17:0cy, a15:0 and a17:0 were the most prevalent and soil pH seemed to be responsible for the discrimination of the soil microbial communities against those of the zonal forest types. The pine forest soils were set apart from the other forest soils by a higher abundance of PLFA 18:2ω6,9, which is typical of fungi and may also indicate ectomycorrhizal fungi associated with pine trees, and high amounts of PLFA 10Me18:0, which is common in actinomycetes. These findings suggest that the occurrence of azonal forest types at sites with specific soil conditions is accompanied by the development of specific soil microbial communities. The study provides information on the microbial communities in undisturbed forest soils which may facilitate interpretation of data derived from managed or even damaged or degraded forests.     

Polypore diversity in the herb-rich woodland key habitats of Koli National Park in eastern Finland

Species diversity of polypores (Basidiomycetes) was compared between woodland key habitats (WKHs) and old-growth forest controls in boreal forests in eastern Finland. WKHs, which were set aside for their rich vascular plant flora, turned out not to be hot spots for the species richness of polypores, nor did their species composition represent the overall species richness of the area. Differences in the total volume of CWD, tree species composition and several CWD qualities were reflected as differences in the species assemblages between the groups. The results indicated that only a fraction of the overall polypore diversity was represented in the small-size WKHs (<0.5 ha), and the protection of red-listed and indicator polypores in WKHs was random. However, rare old-growth forest indicators were found even in small-size WKHs, if the CWD quality was appropriate for them. Nevertheless, our study does not answer the question whether the occurrences of rare and red-listed species will survive in small-size WKHs surrounded by altered environments such as clear-cuts, because our study sites were located in undisturbed areas. The results stress the importance to protect typical old-growth forest patches with high CWD volume and quality in boreal forests.     

Epiphyte communities on the trunks of retention trees stabilise in 5 years after timber harvesting, but remain threatened due to tree loss

Live retention trees are expected to support the recovery of epiphytes in regenerating stands by retaining a part of the populations in cutover sites and receiving propagules from adjacent forests. So far, the research has been focused on immediate post-harvesting mortality caused by microclimatic stress while a broader perspective on epiphyte community dynamics is lacking. We studied lichen and bryophyte communities on the trunks of retention trees and adjacent forest trees in Estonia, where significant desiccation (particularly of bryophytes) had been documented within 2-3 years after timber harvesting. The resampling 5-6 years after harvesting indicated that, during the 3 years passed, (1) lichen species richness per surviving tree increased and bryophyte species richness stabilised, (2) there were no clear successional changes in the composition of the communities and (3) retention trees were more frequently colonised than forest trees. Most epiphyte extinctions between the sampling years were related to the death of trees (particularly in the forests because of harvesting) and stochastic disappearances of the smallest populations. Also, retention trees were very rarely colonised by species of conservation concern. We conclude that, in addition to addressing the microclimatic stress in the first post-harvesting years, crucial elements in sustaining epiphytic bryophyte and lichen populations in green-tree retention systems include careful selection of the retention trees and a supportive reserve network. The selection of the trees should assure representativity and long-term survival of local populations, while reserves should host the most demanding species and be stable colonisation sources in general.