Influence of ground substrate on establishment of reindeer lichen after artificial dispersal

Methods to improve the recovery of reindeer lichen after soil disturbance or overgrazing are being sought for areas where reindeer are herded. The effects of four substrates – mineral soil, moss, twigs and pine bark – on the establishment of lichen fragments after total removal of the vegetation were thus studied in a middle-aged pine stand and a clear-cut, both located in a lichen-rich pine-heath. Cladina mitis fragments of two sizes were manually dispersed in 1 m2 quadrats and their movements from their respective dispersal points were registered after one year. The natural re-establishment of lichens in the quadrats was monitored over three years by using digital pictures. In the forest stand, no significant differences were detected in either the fragment movement or the lichen establishment between the different substrates, but the fragment size had positive effects on both parameters. In the clear-cut, the moss substrate was the most suitable not only for the artificially dispersed lichens to fasten to, but also for the natural settlement of lichens from the surrounding lichen mat. More lichen thalli fastened to the bark and twigs substrates than to the mineral soil, but the settlement of lichens from the surrounding was greater on bare mineral soil substrate. The results indicate that artificial dispersal of lichen thalli on an appropriate substrate could be a successful strategy for promoting lichen recovery

The introduction of Pinus contorta in Sweden

An increasing demand for forest-based products calls for further development and intensification of forest management. The use of non-native tree species in forestry is a common and expanding silvicultural practice worldwide but the effect of non-native trees on native biodiversity and ecosystem functioning is still poorly understood. The general aim of this thesis is to increase our knowledge about what effects large-scale introduction of a non-native tree species have on forest biodiversity over a chronosequence of forest stand ages. The non-native Pinus contorta and the two native tree species Pinus sylvestris and Picea abies were studied over three age classes (15, 30, 85 years old) of managed forests in northern Sweden to compare the stand- and tree structures, the cover and composition of functional groups of ground vegetation, and the species- and functional diversity of epiphytic lichens. Differences in ground vegetation cover were linked to both tree species and different stand and tree characteristics, but the differences were not consistent over the age classes. Stands of P. contorta had higher cover of vascular plants than the native tree species, and the cover increased with increasing stand age. Trees of P. contorta generally were of larger size than native tree species of comparable age, and also had greater branch surface area in young and middle aged stands, indicating more available substrate for epiphytes. However, the species richness of epiphytic lichens in P. contorta stands was comparable to P. sylvestris and the highest species richness was found in Picea abies stands. Although the forests shared many species, the composition progressively diverged with increasing forest age. Presence of dead branches, greater bark crevice depth and canopy cover generally had positive effect on functional trait diversity, and the reproductive strategy and growth form were the most influential traits on differences in functional diversity between tree species at early successional stages. Generally, the results suggest that abiotic and biotic factors common to all young managed forests act as environmental filters that cause similarly low levels of functional diversity and functional insurance among their epiphytic lichen communities. In conclusion, the planting of P. contorta does not create “green deserts” from the perspective of epiphytic lichens or understory vegetation. However, most stands of P. contorta are still younger than 50 years, and to assess the implications on forest diversity over a full rotation cycle, future studies should focus on describing diversity in old P. contorta stands

A Pine Is a Pine and a Spruce Is a Spruce--The Effect of Tree Species and Stand Age on Epiphytic Lichen Communities.

With an increasing demand for forest-based products, there is a growing interest in introducing fast-growing non-native tree species in forest management. Such introductions often have unknown consequences for native forest biodiversity. In this study, we examine epiphytic lichen species richness and species composition on the trunks of non-native Pinus contorta and compare these to the native Pinus sylvestris and Picea abies in managed boreal forests in northern Sweden across a chronosequence of age classes. Overall, we recorded a total of 66,209 lichen occurrences belonging to 57 species in the 96 studied forest stands. We found no difference in species richness of lichens between stands of P. contorta and P. sylvestris, but stands of P. abies had higher total species richness. However, species richness of lichens in stands of P. abies decreased with increasing stand age, while no such age effect was detected for P. contorta and P. sylvestris. Lichen species composition progressively diverged with increasing stand age, and in 30-year-old stands all three tree species showed species-specific assemblages. Epiphytic lichen assemblages in stands of 30-year-old P. contorta were influenced by greater basal area, canopy closure, and average diameter at breast height, P. abies stands by higher branch density and canopy closure, and stands of P. sylvestris by greater bark crevice depth. Differences in lichen species richness and composition were mainly explained by canopy closure and habitat availability, and the greater canopy closure in mature P. abies stands promoted the colonization and growth of calicioid lichen species. Our results indicate that the non-native P. contorta have similar species richness as the native P. sylvestris. The main difference in lichen species richness and composition is between P. abies and Pinus spp. in managed forests of boreal Sweden

Model-averaged parameter estimates and 95% confidence intervals for total lichen species richness in <i>Picea abies</i>, <i>Pinus contorta</i>, and <i>Pinus sylvestris</i> stands of three different age classes.

<p>Model-averaged parameter estimates and 95% confidence intervals for total lichen species richness in <i>Picea abies</i>, <i>Pinus contorta</i>, and <i>Pinus sylvestris</i> stands of three different age classes.</p

Average lichen cover per tree plot in the different stand types.

<p>Error bars represent the standard error.</p

a-c. Similarity percentage analysis (SIMPER) of lichen community dissimilarity between the different tree species.

<p>Panels show <i>Picea abies</i>, <i>Pinus contorta</i>, and <i>Pinus sylvestris</i> in (a) 15-year-old, (b) 30-year-old, and (c) 85-year-old forest stands. The single 85-year-old <i>P</i>. <i>contorta</i> stand was not included in the analysis. Species from the top of the list contributed the most to the average dissimilarity of lichen assemblages in different stand types. Only species that contributed to 90% of the dissimilarity between stand types are presented. Lichen growth form is indicated by the letter in brackets: (c) = crustose, (f) = foliose, and (fr) = fruticose.</p

Average number of lichen species per tree plot in the different stand types.

<p>Error bars represent the standard error.</p

Nonmetric multidimensional scaling (NMDS) ordination graph of lichen species composition.

<p>Lichens of 57 taxa on 384 trees in a total of 96 managed forest stands of <i>Picea abies</i>, <i>Pinus contorta</i>, and <i>Pinus sylvestris</i> in (a) 15-year-old, (b) 30-year-old, and (c) 85-year-old stands. Triangles = <i>Picea abies</i>, crosses = <i>Pinus contorta</i>, and squares = <i>Pinus sylvestris</i>. Correlation coefficients between five environmental variables and the NMDS scores are presented as vectors from the origin. The lengths of the vectors are arbitrarily scaled to make a readable biplot, so only their directions and relative lengths should be considered. All NMDSs resulted in 2-dimensional solutions with all final stresses < 0.14. Axis 1 explained most of the variance in the data. The following terms have been abbreviated: bark crevice depth (Bark crevice) and diameter at breast height (Dbh).</p