Forest management aims for productive and stable forests that continuously provide ecosystem goods and services, including balancing nutrient fluxes. Increasing heat and frequent droughts in ...temperate European forests make the introduction of non-native Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) an increasingly relevant climate change adaptation strategy, particularly as an admixture to native tree species, such as European beech (Fagus sylvatica L.). Douglas fir can alter biogeochemical processes in forest soils, potentially leading to an excess of nitrogen in the ecosystem, but the biotic and abiotic controls of this effect need further examination (species interactions, soil type). Here we studied nitrate leaching on plots of two contrasting textures (southern loamy and northern sandy site) planted with either pure Douglas fir, pure Norway spruce (Picea abies L. Karst.), pure European beech or a mixture of beech with either of the conifers. We used P80 suction lysimeters at 5 and 60 cm soil depth and collected soil solution over two continuous years to estimate nitrate leaching risks. We found highest concentrations of nitrate in soil solution in lower soil layers under Douglas fir (29.14 mg/L), which corroborates the findings of some studies conducted in pure stands. Comparisons of concentrations below the litter layer and below the main rooting zone implied that accumulation and microbial production of nitrate is taking place under Douglas fir. In Douglas fir-beech mixed stands, however, we found sustained significantly lower nitrate concentrations in soil solution below the main rooting zone (1.68 mg/L), implying a mixture effect. Furthermore, site played a key role in controlling nitrate concentrations in soil solution under Douglas fir on sites with finer soil texture and a lower C:N ratio. Elevated nitrate concentrations were associated with a P-limitation found in the trees, which likely caused reduced nitrate uptake. We discuss the results with regards to throughfall, litter, soil and microbial characteristics. We conclude that increased nitrate concentrations under Douglas fir stands may pose a relatively higher nitrate leaching risk than Norway spruce and a considerably higher risk compared to beech stands. However, the low susceptibility to leaching under beech stands seems to be a strong effect trait in mixtures, diminishing the high leaching potential Douglas fir induces on some sites. Low leaching potential is key to sustaining adequate nutrition in temperate forests and reducing pollution of groundwater. Our findings strongly urge forestry experts to carefully assess site conditions and foster mixtures with European beech when planting Douglas fir.
•Tree species affect nitrogen cycling; Douglas fir can increase nitrate concentrations in soil solution, posing a risk for nitrate leaching.•When mixed with European beech, nitrate concentrations remain low.•On sandy, poorer sites, nitrate leaching was much lower than on loamy sites.•P-limitation of Douglas fir caused reduced N uptake, leading to N accumulation in soil solution.•Nitrate production by microorganisms was likely stimulated under Douglas fir.
Key message
In mixed combinations, the negative impact of water reduction and N addition is mitigated for
F. sylvatica
, but not for conifers.
Insight into the responses of trees in mixed and ...monospecific cultivation to water scarcity and nitrogen (N) excess is necessary to recommend suitable tree mixtures for future European forests. Our aim was to investigate the impact of water reduction, N addition or water reduction + N addition in comparison with control (well-watered, no excess N) on mycorrhizal roots and biomass of three temperate forest species (
Fagus sylvatica
Fs,
Picea abies
Pa, and
Pseudotsuga menziesii
Pm) grown in monospecific (FsFs, PaPa, PmPm) and mixed combinations (PaFs, PmFs). We predicted the probability of the responses with a Bayesian approach. Mycorrhizal colonization declined marginally for
P. menziesii
in PmFs under water reduction. Under water reduction and N addition combined, we found a decline in root tip vitality of
F. sylvatica
in PaFs and of
P. abies
in PaPa.
F. sylvatica
shoot biomass declined under water reduction + N addition in the monospecific combination.
P. abies
and
P. menziesii
had lower root biomass in mixture with
F. sylvatica
under water reduction + N addition and under water reduction as single factor, respectively. With water reduction and N addition,
P. menziesii
performed better than
P. abies
in terms of biomass production.
F. sylvatica
had a growth advantage in mixture with conifers instead of conspecifics. These findings suggest that young trees show rapid and interspecific responses to species mixing and water + N availability. The selection of suitable tree species should, therefore, consider their interactive responses to changing abiotic factors.
To increase the resilience of forests to drought and other hazards, foresters are increasingly planting mixed stands. This requires knowledge about the drought response of tree species in pure and ...mixed-culture neighborhoods. In addition, drought frequently interacts with continued atmospheric nitrogen (N) deposition. To disentangle these factors for European beech, Norway spruce and Douglas fir, we conducted a replicated 3-factorial sapling growth experiment with three moisture levels, (high, medium, and low), two N levels (high and ambient), and pure and mixed-culture neighborhoods. We measured biomass, stomatal conductance (GS), shoot water potential (at predawn: ΨPD, midday, and turgor loss point: ΨTLP), branch xylem embolism resistance (Ψ50) and minimum epidermal conductance (Gmin). The three species differed most with respect to Gmin (10-fold higher in beech than in the conifers), hydroscape area (larger in beech), and the time elapsed to reach stomatal closure (TΨGS90) and ΨTLP (TTLP; shorter in beech), while Ψ50 and ΨTLP were remarkably similar. Neighborhood (pure vs mixed-culture) influenced biomass production, water status and hydraulic traits, notably GS (higher in Douglas fir, but lower in spruce and beech, in mixtures than pure culture), hydraulic safety margin (smaller for beech in mixtures), and TΨGS90 and TTLP (shorter for spruce in mixture). High N generally increased GS, but no consistent N effects on leaf water status and hydraulic traits were detected, suggesting that neighbor identity had a larger effect on plant water relations than N availability. We conclude that both tree neighborhood and N availability modulate the drought response of beech, spruce, and Douglas fir. Species mixing can alleviate the drought stress of some species, but often by disadvantaging other species. Thus, our study suggests that stabilizing and building resilience of production forests against a drier and warmer climate may depend primarily on the right species choice; species mixing can support the agenda.
Abstract Key message Differences in architectural traits of European beech saplings submitted to different levels of competition intensity and neighborhood diversity show a shift toward lateral ...growth exploration for overtopped trees but less expressed apical control is maintained for beech grown with conifers. Abstract Crown plasticity is a fundamental process to optimize the acquisition of light in forests, where it is often the limiting factor for growth. The processes leading to crown dynamics in response to biotic interaction are controlled by the competitive status of a tree, as well as the species diversity of the neighborhood. Yet, the ontogenic diversity of the different branches leading to crown structure makes it difficult to model crown plasticity. In this study, we used single-image photogrammetry and a semi-automatic topology reconstruction software to map the architecture of 3-year-old European beech trees ( Fagus sylvatica L.) grown in pure pots or mixed with Douglas fir ( Pseudotsuga menziesii (Mirbel) F ranco) or Norway spruce ( Picea abies L. H.K arst ). Further, we investigated the effect of competition intensity (estimated with height rank) and neighbourhood diversity on architectural traits. To do so, we quantified the mean volume, slenderness, number of branches, branching rate, internode length, and diameter ratio for each stem and branch, up to the order three. Overtopped trees developed fewer branches and biomass but allocated more biomass to branches of a higher order than to the stem. The increase in the ramification of the stem and the diameter ratio of the first-order branches for overtopped trees indicate a shift in the growth strategy and a decrease in apical control. As competition intensity and neighbour identity have opposite effects on stem traits, it seems that the positive effect of plant diversity on growth can be attributed to the intrinsic effects of species identity rather than to competition release.
Sir, We report the case of a 51-year-old woman who was admitted to the emergency department at the University Hospital Center Zagreb, Croatia, presenting with progressively worsening headache, ...nausea, dizziness, and ataxia. 4,5 Our patient had coincidental vestibular schwannoma, a condition known to be associated with changes in CSF dynamics and hydrocephalus - it is possible that the schwannoma acted as a predisposing condition and the viral infection triggered the acute hydrocephalus. Steininger C, Kundi M, Aberle SW, Aberle JH, Popow-Kraupp T. Effectiveness of reverse transcription-PCR, virus isolation, and enzyme-linked immunosorbent assay for diagnosis of influenza A virus infection in different age groups.
Spinal cord lipomas are rare and benign tumors which may cause progressive neurological deficits due to their local expansion. We present the case of a 59-year-old male patient with severe ...lumbosacral pain and slowly progressive paresis of the right leg, misdiagnosed with degenerative spine disease. Repeated magnetic resonance (MR) T1-weighted images of the thoracic spine suggested a subacute intramedullary hematoma. Due to progression of the neurological deficit, the patient was referred to a neurosurgeon, who indicated surgical evacuation of the hematoma. The intraoperative finding revealed an intramedullary spinal cord lipoma, which was later confirmed by histological analysis. Since subacute intramedullary hematomas and intramedullary spinal cord lipomas present with similar clinical and radiological features, diffusion-weighted MR imaging should be used to distinguish these entities.
Despite growing popularity of endovascular techniques, certain subsets of patients with cerebrovascular compromise may benefit from bypass surgery. We present four cases in which pending ischemic ...lesion was prevented by (1) A3 resection and reanastomosis following falx meningioma removal, (2) rescue superficial temporal artery–middle cerebral artery (STA-MCA) bypass after pituitary adenoma surgery, (3) STA-MCA bypass for chronic internal carotid artery occlusion, and (4) external carotid artery-MCA bypass using radial artery grafting. Following the procedure, there were no further clinical or radiological deteriorations and long-term patency was confirmed in all four cases.
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