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In south-east Norway, in the hemiboreal vegetation zone, beech reaches its northern distribution limit and typically occupies the same type of sites as spruce. Under future climate change, this area is projected to fall within the temperate zone and beech to increase its distribution towards the north at the expense of spruce. However, such forecasts are based on very broad scale estimates and the knowledge of climatic adaptation and the competitive potential of the beech and spruce populations at these latitudes is scarce. Here, we use a dendrochronological approach to study the growth performance of neighbouring spruce and beech trees to climate variability over a period of 70 years. The two species responded quite similarly to variations in climate in the study area. Both showed increased incremental growth in response to high precipitation both in the previous and present year June, indicating that water is a limiting resource. In addition, beech showed a negative response to high temperatures in previous July and August, which is probably connected with growth reductions due to masting. Overall, spruce and beech in the hemiboreal zone show comparable responses to climatic variations as in the temperate zone. Due to the different drought-handling strategies of the two species, we suggest that the intensity of summer droughts and the variability between years are likely factors that would be decisive for which of them that will be more successful under future climatic conditions. [ABSTRACT FROM AUTHOR]

Veteran trees are keystone structures and play vital roles in ecosystems. Tree hollows, which are filled with a mix of leaves and wood that is transformed by the biotic community into wood mould, represent an important microhabitat. Tree hollow communities consist of three major groups of organisms: microbes, mesofauna (nematodes, mites and springtails) and macrofauna (beetles, millipedes and other insects). Little is known about the interplay between associated biota and their importance for decomposition and wood mould production. The aim of this study was to test how initial food web complexity in artificial tree hollows influences community structure, decomposition, and wood mould production. We used large wooden boxes to imitate natural hollows, and mounted them on 20 veteran oaks in Southern Norway. The food webs were manipulated into three levels: (i) a complex community with macrofauna and mesofauna, (ii) a simple community without macrofauna, and (iii) only the defaunated material. Three boxes (one of each treatment, N = 60 boxes) were mounted on each oak and left in the field from May 2017 to October 2019 (28 months). After the field experiment, macrofauna and mesofauna were collected and identified, mass loss in the boxes was determined, and nitrogen and phosphorus concentrations in the wood mould were measured. We found that the complex community treatment had the greatest diversity of beetles and the highest number of predatory macrofauna. The nematodes within the complex community treatment had greater trophic structuring with K‐selected species associated with stable conditions. The nematodes communities also indicated that the complex community had a balanced decomposition pathway, while the simple community was dominated by fungi and the defaunated community by bacteria. Lastly, we found that the boxes with the complex community treatment had the highest overall rate of mass loss, and greater amounts of wood mould with higher concentrations of nitrogen and phosphorus. Our results indicate that macrofauna in artificial hollows increase trophic structuring, enhance decomposition rates and wood mould production, and mediate the decomposition pathway. These findings highlight the importance of food web complexity for promoting biodiversity and ecosystem functioning in veteran tree hollows. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Aim: Functional traits offer a window into how organisms are adapted, and might acclimate, to environmental pressures. Despite being important in ecosystem function, lichens are underrepresented in trait‐based research; understanding how lichen functional traits vary with climate and habitat availability will be useful in predicting how communities will respond to climate change, for example, in wetter and warmer boreal and arctic ecosystems. Here, we assess the influence of macroclimate and forest availability on the spatial distribution of lichen traits across Norway. Location: Norwegian mainland. Taxon: Lichens. Methods: We used relative trait frequency (RTF) data from LIAS gtm, a database combining trait information from LIAS (A Global Information System for Lichenized and Non‐Lichenized Ascomycetes) and GBIF (Global Biodiversity Information Facility) species observations. The 20 traits included photobiont types, growth forms, cortical features and reproductive modes. Nonparametric multiplicative regression (NPMR) models were used to explore the relationships between the environmental predictors of precipitation, temperature and forest availability. Results: All traits showed significant relationships with the three environmental predictors. Photobiont type and reproductive mode traits produced the strongest models and revealed ecologically meaningful biogeographical patterns. Trebouxioid species peaked in colder, drier upland regions, while trentepohlioid lichens displayed an affinity for wetter and warmer climates and had a western and southern distribution. Cyanolichens increased with increasing precipitation and were strongly coastal. Sorediate and isidiate lichens were positively related to temperature, the former also increasing with forest cover. The above responses were consistent with the physiological and habitat requirements of the associated lichens. The remaining traits had weaker responses. Main conclusions: Discrete traits (i.e. photobiont type and reproductive mode) with relatively low ecological plasticity reflect clear functional environmental responses at the large scale. By contrast, growth form and thallus structural features—proxies for continuous variables—are too variable within each given category to show observable distribution patterns. [ABSTRACT FROM AUTHOR]

Lichen heaths are declining in abundance in alpine and Arctic areas partly due to an increasing competition with shrubs. This shift in vegetation types might have important consequences for the microclimate and climate on a larger scale. The aim of our study is to measure the difference in microclimatic conditions between lichen heaths and shrub vegetation during the growing season. With a paired plot design, we measured the net radiation, soil heat flux, soil temperature and soil moisture on an alpine mountain area in southern Norway during the summer of 2018 and 2019. We determined that the daily net radiation of lichens was on average 3.15 MJ (26 %) lower than for shrubs during the growing season. This was mainly due to a higher albedo of the lichen heaths but also due to a larger longwave radiation loss. Subsequently, we estimate that a shift from a lichen heath to shrub vegetation leads to an average increase in atmospheric heating of 3.35 MJ d -1 during the growing season. Surprisingly, the soil heat flux and soil temperature were higher below lichens than below shrubs during days with high air temperatures. This implies that the relatively high albedo of lichens does not lead to a cooler soil compared to shrubs during the growing season. We predict that the thicker litter layer, the presence of soil shading and a higher evapotranspiration rate at shrub vegetation are far more important factors in explaining the variation in soil temperature between lichens and shrubs. Our study shows that a shift from lichen heaths to shrub vegetation in alpine and Arctic areas will lead to atmospheric heating, but it has a cooling effect on the subsurface during the growing season, especially when air temperatures are relatively high. [ABSTRACT FROM AUTHOR]

Lichen heaths are declining in abundance in alpine and arctic areas partly due to an increasing competition with shrubs. This shift in vegetation types might have important consequences for the microclimate and climate on a larger scale. The aim of our study is to measure the difference in microclimatic conditions between lichen heaths and shrub vegetation during the growing season. With a paired plot design, we measured the net radiation, soil heat flux, soil temperature, and soil moisture on an alpine mountain area in south Norway during the summer of 2018 and 2019. We determined that the daily net radiation of lichens was on average 3.15 MJ (26 %) lower than for shrubs during the growing season. This was mainly due to a higher albedo of the lichen heaths, but also due to a larger longwave radiation loss. Subsequently, we estimate that a shift from a lichen heath to shrub vegetation leads to an average increase in atmospheric heating of 3.35 MJ per day during the growing season. Surprisingly, the soil heat flux and soil temperature were higher below lichens than below shrubs during days with high air temperatures. This implies that the relatively high albedo of lichens does not lead to a cooler soil compared to shrubs during the growing season. We hypothesize that the thicker litter layer, the presence of soil shading, and a higher evapotranspiration rate at shrub vegetation are far more important factors in explaining the variation in soil temperature between lichens and shrubs. Our study shows that a shift from lichen heaths to shrub vegetation in alpine and arctic areas will lead to atmospheric heating, but has a cooling effect on the subsurface during the growing season, especially when air temperatures are relatively high. [ABSTRACT FROM AUTHOR]

Lichen heaths are declining in abundance while shrubs are increasing their range in alpine and arctic areas due to climate change. This can have a large impact on the surface albedo of these areas. The aim of this article is to quantify the difference in albedo between lichen heaths and shrub-dominated vegetation and the variability within lichen heaths. Several environmental conditions that can influence the albedo measurements are considered. We measured the albedo of twenty lichen- and shrub-dominated plots on an alpine mountain area in southern Norway in the summer of 2018 with two radiometers using a paired plot design. With this design, we ensured similar weather conditions, aspects, and zenith angles between the paired lichen- and shrubdominated plots. In addition, we collected patches of Cladonia stellaris and Flavocetraria nivalis to measure their albedo. The average difference in albedo between the lichen- and shrub-dominated plots is 0.124. The albedo of the lichen-dominated plots varies between 0.227 and 0.284, and that of the shrub-dominated plots varies between 0.115 and 0.148. This variation in albedo is explained by differences in aspect and vegetation composition. Further studies should focus on the consequences of this decrease in albedo for the microclimate in alpine and arctic areas. [ABSTRACT FROM AUTHOR]

Past forest management decisions have resulted in European beech being replaced with Norway spruce across Europe. Previous studies have revealed variances in soil carbon (C) under different dominating tree species. Yet, there is a scarcity of knowledge about how beech and spruce differ in impact on forest soil C in boreal regions, where beech has its northern distribution limit. We have therefore compared soil C in a natural beech forest (Be) with that of two spruce forests: one planted on former beech forest (SpBe) and the other on former spruce forest (Sp), in South-East Norway. Analyses of biochemical parameters and fungal biomass were performed along fine-scaled soil profiles, covering both the organic and mineral layers. We found no significant difference between the forests when comparing estimates of total C stocks per area. However, throughout the soil profile, the distribution of soil C in Be varied significantly from SpBe, while Sp was intermediate. The distribution of fungal biomass along the soil profile in Be varied significantly from the two other forests. Hence, fungal biomass may drive the observed differences. Soil C, nitrogen (N), and C/N ratios were forest type and soil depth dependent, whereas forest type had an effect on the vertical distribution of condensed tannins and fungal biomass. Our results suggest that the presence of beech or spruce as the dominant tree species in the studied area has an effect on the vertical distribution of soil properties, while there is no major difference when comparing the whole soil profile. [ABSTRACT FROM AUTHOR]

Gastropod abundance was quantified in forest litter around 33 trees harbouring Lobaria pulmonaria in southern Norway. In total, 1709 snails representing 28 species were found, and the number of snail species strongly increased with the total number of specimens found. Number of snail species, as well as snail abundance, was highest around trees on high pH soils. There was a positive relationship between number of snail specimens and cover of grazing traces on L. pulmonaria, presumably because calcareous soils facilitate both litter dwelling and climbing gastropods. The results suggest that gastropods may limit the distribution of L. pulmonaria in calcareous broad-leaved forests. [ABSTRACT FROM AUTHOR]

Beech forests reaches its native distribution limit in SE Norway, but is expected to expand substantially northwards due to climate warming. This may potentially result in a fundamental transformation of contemporary Northern European forests, with tentative effects on the associated belowground fungi. Fungal communities mediate vital ecosystem processes such as ecosystem productivity and carbon sequestration in boreal forests. To investigate how soil fungi is affected by the vegetation transition from spruce to beech forest, we sampled litter, humus and mineral soil in a forest landscape dominated by beech, spruce or a mixture of these. The fungal communities in the soil samples were analyzed by DNA metabarcoding of the rDNA ITS2 region. Although soil layers were the most important structuring gradient, we found clear differences in fungal species composition between spruce and beech plots. The differences in fungal community composition were most evident in the litter and least in the mineral soil. Decomposers, most notably Mycena, dominated the litter layer while various mycorrhizal fungi dominated the humus and mineral layers. Some ectomycorrhizal taxa, such as Cenoccocum and Russula, were more abundant in spruce forests. Differences in fungal community composition between forest types can potentially have large impacts on carbon sequestration rates.

Lichens are useful monitoring organisms for heavy metal pollution. They are high in carbon based secondary compounds (CBSCs) among which some may chelate heavy metals and thus increase metal accumulation. This study quantifies CBSCs in four epiphytic lichens transplanted for 6months on stands along transects from a highway in southern Norway to search for relationships between concentrations of heavy metals and CBSCs along a gradient in heavy metal pollutants. Viability parameters and concentrations of 21 elements including nutrients and heavy metals in these lichen samples were reported in a separate paper. Medullary CBSCs in fruticose lichens (Ramalina farinacea, Usnea dasypoga) were reduced in the most polluted sites, but not in foliose ones (Parmelia sulcata, Lobaria pulmonaria), whereas cortical CBSC did not change with distance from the road in any species. Strong positive correlations only occurred between the major medullary compound stictic acid present in L. pulmonaria and most heavy metals, consistent with a chelating role of stictic acid, but not of other studied CBSCs or in other species. However, heavy metal chelating did not protect L. pulmonaria against damage because this species experienced the strongest reduction in viability in the polluted sites. CBSCs with an accumulation potential for heavy metals should be quantified in lichen biomonitoring studies of heavy metals because they, like stictic acid, could overshadow pollutant inputs in some species rendering biomonitoring data less useful. In the two fruticose lichen species, CBSCs decreased with increasing heavy metal concentration, probably because heavy metal exposure impaired secondary metabolism. Thus, we found no support for a heavy metal protection role of any CBSCs in studied epiphytic lichens. No intraspecific relationships occurred between CBSCs versus N or C/N-ratio. Interspecifically, medullary CBSCs decreased and cortical CBSCs increased with increasing C/N-ratio., (Copyright © 2015 Elsevier B.V. All rights reserved.)

While there has been much interest in the relationships between traits of primary producers and composition of associated invertebrate consumer communities, our knowledge is largely based on studies from vascular plants, while other types of functionally important producers, such as lichens, have rarely been considered. To address how physiological traits of lichens drive community composition of invertebrates, we collected thalli from 27 lichen species from southern Norway and quantified the communities of associated springtails, mites, and nematodes. For each lichen species, we measured key physiological thallus traits and determined whether invertebrate communities were correlated with these traits. We also explored whether invertebrate communities differed among lichen groups, categorized according to nitrogen-fixing ability, growth form, and substratum. Lichen traits explained up to 39% of the variation in abundances of major invertebrate groups. For many invertebrate groups, abundance was positively correlated with lichen N and P concentrations, N:P ratio, and the percentage of water content on saturation (WC), but had few relationships with concentrations of carbon-based secondary compounds. Diversity and taxonomic richness of invertebrate groups were sometimes also correlated with lichen N and N:P ratios. Nitrogen-fixing lichens showed higher abundance and diversity of some invertebrate groups than did non-N-fixing lichens. However, this emerged in part because most N-fixing lichens have a foliose growth form that benefits invertebrates, through, improving the microclimate, independently of N concentration. Furthermore, invertebrate communities associated with terricolous lichens were determined more by their close proximity to the soil invertebrate pool than by lichen traits. Overall, our results reveal that differences between lichen species have a large impact on the invertebrate communities that live among the thalli. Different invertebrate groups show contrasting responses to traits that are indicative of thallus quality (nutrient concentrations), and thallus growth form is often an important determinant of the invertebrate community. Given the large diversity of lichen traits and growth forms that occur in many ecosystems, lichen-invertebrate communities may be an important contributor to overall community diversity in boreal forests.