In declining broadleaf forests in western Ukraine, several Phytophthora species including P. plurivora, P. bilorbang, P. polonica, P. gonapodyides and P. cactorum were recovered using soil baiting ...assays and identified using morphological and molecular methods. Pathogenicity tests of selected isolates were performed on black alder (Alnus glutinosa (L.) Gaerth.) and silver birch (Betula pendula Roth.) to assess susceptibility of these two tree species to the newly detected Phytophthora species. Phytophthora plurivora, P. bilorbang and P. polonica showed higher pathogenicity in both alder and birch compared to the other tested Phytophthora species.
Forest peatlands represent 25 % of global peatlands and store large amounts of carbon (C) as peat. Traditionally they have been drained in order to increase forestry yield, which may cause large ...losses of C from the peat. Rewetting aims to stop these losses and to restore the initial storage function of the peatlands. As roots represent major peat-forming elements in these systems, we sampled roots with diameter <5 mm in a drained and a rewetted forest peatland in north-east Germany to evaluate differences in tree biomass investments below ground, root functional characteristics and root age.
We cored soil next to Alnus glutinosa stems and sorted root biomass into <1, 1-2 and 2-5 mm diameter classes. We measured biomass distribution and specific root area (SRA) in 10-cm depth increments down to 50 cm, and estimated root age from annual growth rings.
Root biomass in the rewetted site was more than double that in the drained site. This difference was mostly driven by very fine roots <1 mm, which accounted for 51 % of the total root biomass and were mostly (75 %) located in the upper 20 cm. For roots <1 mm, SRA did not differ between the sites. However, SRA of the 1-2 mm and 2-5 mm diameter roots was higher in the drained than in the rewetted site. Root age did not differ between sites.
The size-dependent opposite patterns between root biomass and their functional characteristics under contrasting water regimes indicate differences between fine and coarse roots in their response to environmental changes. Root age distribution points to similar root turnover rates between the sites, while higher root biomass in the rewetted site clearly indicates larger tree C stocks below ground under rewetting, supporting the C sink function of the ecosystem.
Alnus glutinosa
(black alder) is a mycorrhizal pioneer tree species with tolerance to high concentrations of salt in the soil and can therefore be considered to be an important tree for the ...regeneration of forests areas devastated by excessive salt. However, there is still a lack of information about the ectomycorrhizal fungi (EMF) associated with mature individuals of
A. glutinosa
growing in natural saline conditions. The main objective of this study was to test the effect of soil salinity and other physicochemical parameters on root tips colonized by EMF, as well as on the species richness and diversity of an EMF community associated with
A. glutinosa
growing in natural conditions. We identified a significant effect of soil salinity (expressed as electrical conductivity: EC
e
and EC
1:5
) on fungal taxa but not on the total level of EM fungal colonization on roots. Increasing soil salinity promoted dark-coloured EMF belonging to the order Thelephorales (
Tomentella
sp. and
Thelephora
sp.). These fungi are also commonly found in soils polluted with heavy-metal. The ability of these fungi to grow in contaminated soil may be due to the presence of melanine, a natural dark pigment and common wall component of the Thelephoraceae that is known to act as a protective interface between fungal metabolism and biotic and abiotic environmental stressors. Moreover, increased colonization of fungi belonging to the class of Leotiomycetes and Sordiomycetes, known as endophytic fungal species, was observed at the test sites, that contained a larger content of total phosphorus. This observation confirms the ability of commonly known endophytic fungi to form ectomycorrhizal structures on the roots of
A. glutinosa
under saline stress conditions.
Genetic admixture is supposed to be an important trigger of species expansions because it can create the potential for selection of genotypes suitable for new climatic conditions. Up until now, ...however, no continent‐wide population genetic study has performed a detailed reconstruction of admixture events during natural species expansions. To fill this gap, we analysed the postglacial history of Alnus glutinosa, a keystone species of European swamp habitats, across its entire distribution range using two molecular markers, cpDNA and nuclear microsatellites. CpDNA revealed multiple southern refugia located in the Iberian, Apennine, Balkan and Anatolian Peninsulas, Corsica and North Africa. Analysis of microsatellites variation revealed three main directions of postglacial expansion: (i) from the northern part of the Iberian Peninsula to Western and Central Europe and subsequently to the British Isles, (ii) from the Apennine Peninsula to the Alps and (iii) from the eastern part of the Balkan Peninsula to the Carpathians followed by expansion towards the Northern European plains. This challenges the classical paradigm that most European populations originated from refugial areas in the Carpathians. It has been shown that colonizing lineages have met several times and formed secondary contact zones with unexpectedly high population genetic diversity in Central Europe and Scandinavia. On the contrary, limited genetic admixture in southern refugial areas of A. glutinosa renders rear‐edge populations in the Mediterranean region more vulnerable to extinction due to climate change.
Although the pesticide hexachlorocyclohexane (HCH) and its isomers have long been banned, their presence in the environment is still reported worldwide. In this study, we investigated the ...bioaccumulation potential of α, β, and δ hexachlorocyclohexane (HCH) isomers in black alder saplings (Alnus glutinosa) to assess their environmental impact. Each isomer, at a concentration of 50 mg/kg, was individually mixed with soil, and triplicate setups, including a control without HCH, were monitored for three months with access to water. Gas chromatography-mass spectrometry revealed the highest concentrations of HCH isomers in roots, decreasing towards branches and leaves, with δ-HCH exhibiting the highest uptake (roots-14.7 µg/g, trunk-7.2 µg/g, branches-1.53 µg/g, leaves-1.88 µg/g). Interestingly, α-HCH was detected in high concentrations in β-HCH polluted soil. Phytohormone analysis indicated altered cytokinin, jasmonate, abscisate, and gibberellin levels in A. glutinosa in response to HCH contamination. In addition, amplicon 16S rRNA sequencing was used to study the rhizosphere and soil microbial community. While rhizosphere microbial populations were generally similar in all HCH isomer samples, Pseudomonas spp. decreased across all HCH-amended samples, and Tomentella dominated in β-HCH and control rhizosphere samples but was lowest in δ-HCH samples.
Leaf litter decomposition is a major ecosystem process that can link aquatic to terrestrial ecosystems by flows of nutrients. Biodiversity and ecosystem functioning research hypothesizes that the ...global loss of species leads to impaired decomposition rates and thus to slower recycling of nutrients. Especially in aquatic systems, an understanding of diversity effects on litter decomposition is still incomplete.
Here we conducted an experiment to test two main factors associated with global species loss that might influence leaf litter decomposition. First, we tested whether mixing different leaf species alters litter decomposition rates compared to decomposition of these species in monoculture. Second, we tested the effect of the size structure of a lotic decomposer community on decomposition rates.
Overall, leaf litter identity strongly affected decomposition rates, and the observed decomposition rates matched measures of metabolic activity and microbial abundances. While we found some evidence of a positive leaf litter diversity effect on decomposition, this effect was not coherent across all litter combinations and the effect was generally additive and not synergistic.
Microbial communities, with a reduced functional and trophic complexity, showed a small but significant overall reduction in decomposition rates compared to communities with the naturally complete functional and trophic complexity, highlighting the importance of a complete microbial community on ecosystem functioning.
Our results suggest that top‐down diversity effects of the decomposer community on litter decomposition in aquatic systems are of comparable importance as bottom‐up diversity effects of primary producers.
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Plain Language Summary
Summary
Climate change scenarios predict an increase in global temperature and alterations in precipitation regimes, which may change nutrient concentrations in waterbodies. In forested streams, ...decomposition of allochthonous organic matter is a key ecosystem process that is affected by the quality of plant litter entering the streams and several environmental factors, including nutrient concentrations, whose interactive effects are difficult to predict.
We examined the concomitant effects of increased temperature, concentration of inorganic nutrients in stream water and litter quality on leaf decomposition and activity of microbial decomposers. Leaves of alder (Alnus glutinosa) and oak (Quercus robur), representative of high and low initial N content, respectively, were immersed in a stream (NW Portugal) to allow microbial colonisation and then were exposed in microcosms to increasing concentrations of N‐NO3 (0.09–5 mg L−1; six levels) and P‐PO4 (0.003–0.3 mg L−1; three levels) alone or in all possible combinations. One set of microcosms was kept at 12 °C, a temperature typically found in Iberian streams in autumn, and the other set at 18 °C to simulate a warming scenario.
Nitrogen immobilisation was higher in alder than in oak leaves, and increased with temperature and N concentration in stream water for both leaf species.
Leaf decomposition, fungal biomass accrual and reproduction were not affected by P concentration, but overall microbial activity increased asymptotically (Michaelis–Menten kinetics) with N concentration. Increased temperature led to an increase in maximum activity of fungal decomposers and to a decrease in N concentration needed to achieve it, especially in alder leaves.
Under the predicted warming scenario, leaf decomposition may become faster in streams with lower nutrient levels, especially those receiving high‐quality leaf litter.
Alnus glutinosa (namely black alder or European alder) is a tree of the Betulaceae family widely spread through Europe, Southeastern Asia, the Caucasus mountains, and Western Siberia. Its bark is ...traditionally used for medicinal purposes as an astringent, cathartic, febrifuge, emetic, hemostatic, and tonic, suggesting that it may contain bioactive compounds useful to counteract inflammation. The aim of this study was to investigate the phytochemical profile of A. glutinosa stem bark extract (AGE) by LC-DAD-ESI-MS/MS analysis and to validate some biological activities such as antioxidant, anti-inflammatory and anti-angiogenic properties by in vitro and in vivo models (chick chorioallantoic membranes and zebrafish embryos), that can justify its use against inflammatory-based diseases. The AGE showed a high total phenols content expressed as gallic acid equivalents (0.71 g GAE/g of AGE). Diarylheptanoids have been identified as the predominant compounds (0.65 g/g of AGE) with oregonin, which alone constitutes 74.67% of the AGE. The AGE showed a strong and concentration-dependent antioxidant (IC50 0.15–12.21 µg/mL) and anti-inflammatory (IC50 5.47–12.97 µg/mL) activity. Furthermore, it showed promising anti-angiogenic activity, inhibiting both the vessel growth (IC50 23.39 µg/egg) and the release of an endogenous phosphatase alkaline enzyme (IC50 44.24 µg/embryo). In conclusion, AGE is a promising source of antioxidant, anti-inflammatory and angio-modulator compounds.
A protocol has been developed for the propagation of
Alnus glutinosa
axillary shoots in liquid medium. The explants were cultured in Woody Plant Medium supplemented with 0.1 mg l
− 1
benzyladenine ...and 0.5 mg l
− 1
indole acetic acid. The effect of the bioreactor type (RITA® and Plantform™), frequency of the immersions, regulator concentrations, and volume of medium per explant was investigated. All the treatments with the temporal immersion systems (TIS) increased the proliferation rates. The best results were obtained on using the Plantform™ vessels and, unlike the shoots cultured in RITA® vessels, the culture in Plantform™ had very low hyperhydricity percentages. Shoots originating from the culture in semi-solid medium and in Plantform™ rooted in semi-solid medium with 0.1 mg/l indole butyric acid for 7 days. No significant differences were observed in the rooting or acclimatization percentages, with survival percentages greater than 85% being achieved. This is the first work on the use of TIS systems in alder propagation, with the results of this study providing new perspectives for its mass propagation.
Key message
A new protocol is described in order to reduce the propagation costs of alder.
The leaf area index (LAI), as a key indicator of physical and biological processes related to vegetation dynamics, is valuable in monitoring the biomass of forests. Based on the phenological ...development of trees, the LAI shows high seasonal variability. This study estimated the LAI through field measurements and satellite-derived spectral vegetation indices (SVIs) in two alluvial forest sites at species level (black alder). The primary objective of this study was the validation of seasonal relationships between field-measured LAI, using a LI-COR 2200 plant canopy analyzer (PCA), and four red edge and non-red edge satellite-derived spectral vegetation indices (SVIs) of 10 high spatial resolution RapidEye images: the normalized difference vegetation index (NDVI), the red edge NDVI (NDVI-RE), the modified red edge simple ratio (mSR-RE), and the curvature. The indices were compared using 4 phenological phases (leaf flushing until crown closure, leaf growth under crown closure, decreasing leaf chlorophyll content, and leaf senescence) over the entire vegetation period in 2011 using regression analyses, t-test and root mean square error (RMSE). The results suggest that the LAI–SVI relationships varied seasonally. Strong to weak linear relationships were obtained during different periods. For each phase, a different SVI fitted best: NDVI-RE during leaf flushing until crown closure (R2=0.62, RMSE=0.47), mSR-RE during leaf growth under crown closure (R2=0.422, RMSE=0.71), NDVI-RE during decreasing leaf chlorophyll content (R2=0.182, RMSE=0.58), and NDVI during leaf senescence (R2=0.829, RMSE=0.53). Thus, implementing the red edge channel improved the LAI–SVI relationships, particularly during periods with few variations in the LAI. An analysis of the entire vegetation period revealed that NDVI had the best regression (R2=0.942, RMSE=0.507) because it was the most stable index due to moderate LAI values (average max. LAI=4.63). The satellite-based vegetation indices used in this study provided reliable estimates and described the temporal changes and spatial variability in the LAI well. It can be concluded that a LAI–SVI relation cannot be established by a single linear regression throughout a year. Hence, a multi-temporal approach is recommended when monitoring alluvial forest dynamics. Future research on estimating the LAI based on satellite imagery should include the phenological phases into the calculation.
•Different Spectral Vegetation Indices correlated best compared to Leaf Area Index.•The relations of Spectral Vegetation Indices and Leaf Area Index varied seasonally.•These relations based on the forest phenology of Alnus glutinosa.•Strong relations occurred during: leaf flushing until crown closure, leaf senescence.
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