Soil fertility determines whether ectomycorrhizal fungi accelerate or decelerate decomposition in a temperate forest.

Ectomycorrhizal (ECM) fungi can both accelerate and decelerate decomposition of organic matter in forest soils, but a mechanistic understanding of this differential influence is limited. Here, we tested how ECM fungi affect decomposition along a natural fertility gradient in a temperate forest of European beech. Trees were girdled to reduce belowground carbon supply to the soil. Girdling shifted soil fungal community composition and decreased hyphal biomass production and soil CO2 efflux, indicating a reduced ECM fungal activity. Girdling also affected decomposition processes, but the effects depended on fertility. Our results indicate that ECM fungi decelerate decomposition under conditions of low fertility while under conditions of high fertility ECM fungi and their host roots have an accelerating effect. We conclude that both acceleration and deceleration of decomposition of organic matter by ECM fungi can occur within a forest, with soil fertility determining the direction and magnitude of these effects. We suggest a positive feedback between fertility, stand productivity and soil carbon and nitrogen dynamics that is mediated to a large extent by ECM fungi.

Natural disturbance regimes as a guide for sustainable forest management in Europe.

In Europe, forest management has controlled forest dynamics to sustain commodity production over multiple centuries. Yet over-regulation for growth and yield diminishes resilience to environmental stress as well as threatens biodiversity, leading to increasing forest susceptibility to an array of disturbances. These trends have stimulated interest in alternative management systems, including natural dynamics silviculture (NDS). NDS aims to emulate natural disturbance dynamics at stand and landscape scales through silvicultural manipulations of forest structure and landscape patterns. We adapted a "Comparability Index" (CI) to assess convergence/divergence between natural disturbances and forest management effects. We extended the original CI concept based on disturbance size and frequency by adding the residual structure of canopy trees after a disturbance as a third dimension. We populated the model by compiling data on natural disturbance dynamics and management from 13 countries in Europe, covering four major forest types (i.e., spruce, beech, oak, and pine-dominated forests). We found that natural disturbances are highly variable in size, frequency, and residual structure, but European forest management fails to encompass this complexity. Silviculture in Europe is skewed toward even-aged systems, used predominately (72.9% of management) across the countries assessed. The residual structure proved crucial in the comparison of natural disturbances and silvicultural systems. CI indicated the highest congruence between uneven-aged silvicultural systems and key natural disturbance attributes. Even so, uneven-aged practices emulated only a portion of the complexity associated with natural disturbance effects. The remaining silvicultural systems perform poorly in terms of retention compared to tree survivorship after natural disturbances. We suggest that NDS can enrich Europe's portfolio of management systems, for example where wood production is not the primary objective. NDS is especially relevant to forests managed for habitat quality, risk reduction, and a variety of ecosystem services. We suggest a holistic approach integrating NDS with more conventional practices.

Soil fertility relates to fungal-mediated decomposition and organic matter turnover in a temperate mountain forest.

Fungi are known to exert a significant influence over soil organic matter (SOM) turnover, however understanding of the effects of fungal community structure on SOM dynamics and its consequences for ecosystem fertility is fragmentary. Here we studied soil fungal guilds and SOM decomposition processes along a fertility gradient in a temperate mountain beech forest. High-throughput sequencing was used to investigate fungal communities. Carbon and nitrogen stocks, enzymatic activity and microbial respiration were measured. While ectomycorrhizal fungal abundance was not related to fertility, saprotrophic ascomycetes showed higher relative abundances under more fertile conditions. The activity of oxidising enzymes and respiration rates in mineral soil were related positively to fertility and saprotrophic fungi. In addition, organic layer carbon and nitrogen stocks were lower on the more fertile plots, although tree biomass and litter input were higher. Together, the results indicated a faster SOM turnover at the fertile end of the gradient. We suggest that there is a positive feedback mechanism between SOM turnover and fertility that is mediated by soil fungi to a significant extent. By underlining the importance of fungi for soil fertility and plant growth, these findings furthermore emphasise the dependency of carbon cycling on fungal communities below ground.

High Fungal Diversity but Low Seasonal Dynamics and Ectomycorrhizal Abundance in a Mountain Beech Forest.

Forests on steep slopes constitute a significant proportion of European mountain areas and are important as production and protection forests. This study describes the soil fungal community structure in a European beech-dominated mountain forest stands in the Northern Calcareous Alps and investigates how it is determined by season and soil properties. Samples were collected at high spatial resolution in an area of ca. 100 m × 700 m in May (spring) and August (summer). Illumina MiSeq high-throughput sequencing of the ITS2-region revealed distinct patterns for the soil fungal communities. In contrast to other studies from temperate European beech forest stands, Ascomycota dominated the highly diverse fungal community, while ectomycorrhizal fungi were of lower abundance. Russulaceae, which are often among the dominant ectomycorrhizal fungi associated with European beech, were absent from all samples. Potentially plant pathogenic fungi were more prevalent than previously reported. Only subtle seasonal differences were found between fungal communities in spring and summer. Especially, dominant saprotrophic taxa were largely unaffected by season, while slightly stronger effects were observed for ectomycorrhizal fungi. Soil characteristics like pH and organic carbon content, on the other hand, strongly shaped abundant taxa among the saprotrophic fungal community.

Clinical and radiological results after Internal Brace suture versus the all-inside reconstruction technique in anterior cruciate ligament tears 12 to 18 months after index surgery.

BACKGROUND: Anterior cruciate ligament (ACL) injury can lead to reduced function, meniscal lesions, and early joint degeneration. Preservation of a torn ACL using the Internal Brace technique might re-establish normal knee kinematics, avoid donor-site morbidity due to tendon harvesting, and potentially maintain proprioception of the knee. METHODS: Fifty subjects were recruited for this study between December 2015 and October 2016. Two groups of individuals who sustained a unilateral ACL rupture were included: those who underwent surgery with preservation of the injured ACL (Internal Brace technique; IB) and those who underwent ACL reconstruction using a hamstring tendon graft (all-inside technique; AI). Subjective self-administered scores were used: the German version of the IKDC Subjective Knee Form (International Knee Documentation Committee), the German version of the WOMAC (Western Ontario and McMaster Universities Arthritis Index), SF-36 (short form), the German version of the KOOS (Knee Osteoarthritis Outcome Score), and the German version of themodified Lysholm Score by Lysholm and Gillquist. Anterior tibial translation was assessed using the KT-1000 Arthrometer (KT-1000 Knee Ligament Arthrometer, MEDmetric Corp., San Diego, CA, USA). Magnetic resonance evaluation was performed in all cases. RESULTS: Twenty-three subjects (46 %) were men, and the mean age was 34.7 years. The objective IKDC scores were "normal" in 15 and 14 patients, "nearly normal" in 11 and 7 patients, and "abnormal" in 1 and 2 patients, in the IB and AI groups, respectively. KT-1000 assessment showed a sideto-side difference of more than 3 mm on maximum manual testing in 11 (44 %) and 6 subjects (28.6 %) in the IB and AI groups, respectively. In the postoperative MRI, 20 (74 %) and 22 subjects (96 %) in the IB and AI groups had an intact ACL. Anterior tibial translation was significantly higher in the IB group compared with the AI group in the manual maximum test. CONCLUSIONS: Preservation of the native ACL with the Internal Brace primary repair technique can achieve comparable results to ACL reconstruction using Hamstring autografts over a short term. Clinically relevant limitations such as a higher incidence of pathologic laxity, with patients more prone to pivot-shift phenomenon were observed during the study period.

Combined forest and soil management after a catastrophic event.

At the end of October 2018, a storm of unprecedented strength severely damaged the forests of the eastern sector of the Italian Alps. The affected forest area covers 42,500 ha. The president of one of the damaged regions asked for help from the University of Padua. After eight months of discussion, the authors of this article wrote a consensus text. The sometimes asper debate brought to light some crucial aspects: 1) even experienced specialists may have various opinions based on scientific knowledge that lead to conflicting proposals for action. For some of them there is evidence that to restore a destroyed natural environment it is more judicious to do nothing; 2) the soil corresponds to a living structure and every ecosystem's management should be based on it; 3) faced with a catastrophe, people and politicians find themselves unarmed, also because they rarely have the scientific background to understand natural processes. Yet politicians are the only persons who make the key decisions that drive the economy in play and therefore determine the near future of our planet. This article is an attempt to respond directly to a governor with a degree in animal production science, who formally and prudently asked a university department called "Land, Environment, Agriculture and Forestry" for help before taking decisions; 4) the authors also propose an artistic interpretation of facts (uncontrolled storm) and conclusions (listen to the soil). Briefly, the authors identify the soil as an indispensable source for the renewal of the destroyed forest, give indications on how to prepare a map of the soils of the damaged region, and suggest to anchor on this soil map a series of silvicultural and soil management actions that will promote the soil conservation and the faster recovery of the natural dynamic stability and resilience. ELECTRONIC SUPPLEMENTARY MATERIAL: Supplementary material is available for this article at 10.1007/s11629-019-5890-0 and is accessible for authorized users.

Functional performance testing and return to sport criteria in patients after anterior cruciate ligament injury 12-18 months after index surgery: A cross-sectional observational study.

OBJECTIVES: Objective return to sport (RTS) criteria after anterior cruciate ligament (ACL) injury are lacking. Study purposes were (1) to report Limb Symmetry Index (LSI) values achieved in a test battery, (2) to detect how many subjects meet RTS criteria 12-18 months post-operative and (3) to identify whether patient-administered scores predict RTS criteria. DESIGN: Observer-blinded, cross-sectional observational study. SETTING: Traumacenter Linz, Austria. PARTICIPANTS: Eighty-eight subjects (48 females; mean (SD) age: 34.73 (10.8) years); Twenty-five had undergone ACL repair (IB), 21 ACL reconstruction (AI). Forty-two healthy subjects served as control. MAIN OUTCOME MEASURES: Participants were evaluated using a single-leg hop test battery. The variable of interest was meeting the RTS criteria by reaching defined cut-off values. Logistic regression was used to investigate the relationship between subjective scores (IKDC, WOMAC, KOOS, Lysholm) and fulfillment of RTS criteria. Additionally, subjective physical activity and anterior knee translation were assessed. RESULTS: Thirty-six percent of IB patients and 28.6% of AI patients met RTS criteria. None of the included scores produced significant odds to predict RTS. CONCLUSIONS: Subjective scores, clinical examinations and fulfillment of RTS criteria did not differ significantly between groups. Maximum anterior translation revealed a significant difference (p = 0.009) in favor of the AI group.

Reference values for fatigued versus non-fatigued limb symmetry index measured by a newly designed single-leg hop test battery in healthy subjects: a pilot study.

PURPOSE: There is sparse evidence for return to sport criteria after knee injury. Functional performance deficits, particularly in fatigued muscular condition, should be verified prior to the attempt to return to high-risk pivoting sports. The purpose of this study was to generate reference values for the limb symmetry index (LSI) of healthy subjects in fatigued and non-fatigued muscular condition in a newly designed test battery. METHODS: Forty-two healthy subjects [22 females, 20 males; mean (SD) age 30.4 (6.6) years] were evaluated using a test battery consisting of an isometric strength test, a series of five single-leg hop tests and an integrated fatigue protocol. Subjective physical activity was assessed with the Tegner Activity Scale (TAS). The cut-off values for healthy subjects were calculated considering the fifth percentile as the minimum reference value for the LSI and single-leg hop distance. RESULTS: The mean (SD) overall LSI was 98.8% (4.6). No significant gender or age specific differences in limb symmetry were observed. The comparison of the non-fatigued LSI with the overall LSI revealed no clinically relevant change due to muscular fatigue. Repeated measures ANOVA revealed a significant within effect on fatigue/non-fatigue condition (F(1,38) = 18.000; p < 0.001, η2 = 0.321) on absolute single-leg hop distance. Moreover, a significant between effect on the TAS-parameter (F(1,38) = 5.928; p = 0.020, η2 = 0.135 between: TAS ≤ 5/TAS > 5) and on gender (F(1,38) = 23.956; p < 0.001, η2 = 0.387) could be detected. CONCLUSIONS: The absolute jumping distance in the single-leg hop for distance was significantly reduced due to fatigue. No clinically relevant effect of muscular fatigue was observed on limb symmetry in our study sample. Gender and physical activity are important factors to be considered when interpreting reference values.

The impacts of climate change and disturbance on spatio-temporal trajectories of biodiversity in a temperate forest landscape.

1. The ongoing changes to climate challenge the conservation of forest biodiversity. Yet, in thermally limited systems, such as temperate forests, not all species groups might be affected negatively. Furthermore, simultaneous changes in the disturbance regime have the potential to mitigate climate-related impacts on forest species. Here, we (i) investigated the potential long-term effect of climate change on biodiversity in a mountain forest landscape, (ii) assessed the effects of different disturbance frequencies, severities and sizes and (iii) identified biodiversity hotspots at the landscape scale to facilitate conservation management. 2. We employed the model iLand to dynamically simulate the tree vegetation on 13 865 ha of the Kalkalpen National Park in Austria over 1000 years, and investigated 36 unique combinations of different disturbance and climate scenarios. We used simulated changes in tree cover and composition as well as projected temperature and precipitation to predict changes in the diversity of Araneae, Carabidae, ground vegetation, Hemiptera, Hymenoptera, Mollusca, saproxylic beetles, Symphyta and Syrphidae, using empirical response functions. 3. Our findings revealed widely varying responses of biodiversity indicators to climate change. Five indicators showed overall negative effects, with Carabidae, saproxylic beetles and tree species diversity projected to decrease by more than 33%. Six indicators responded positively to climate change, with Hymenoptera, Mollusca and Syrphidae diversity projected to increase more than twofold. 4. Disturbances were generally beneficial for the studied indicators of biodiversity. Our results indicated that increasing disturbance frequency and severity have a positive effect on biodiversity, while increasing disturbance size has a moderately negative effect. Spatial hotspots of biodiversity were currently found in low- to mid-elevation areas of the mountainous study landscape, but shifted to higher-elevation zones under changing climate conditions. 5.Synthesis and applications. Our results highlight that intensifying disturbance regimes may alleviate some of the impacts of climate change on forest biodiversity. However, the projected shift in biodiversity hotspots is a challenge for static conservation areas. In this regard, overlapping hotspots under current and expected future conditions highlight priority areas for robust conservation management.

Substrate influences ecophysiological performance of tree seedlings.

Unfavourable soil conditions frequently limit tree regeneration in mountain forests on calcareous bedrock. Rocky, shallow organic soils on dolomite pose a particular problem for tree regeneration due to commonly restricted water and nutrient supplies. Moreover, an often dense layer of understorey vegetation competes for the limited resources available. Hence, an array of interacting factors impairs tree seedlings' performance on dolomite, but there is little information on the ecophysiological mechanisms. We studied the effects of substrate, competing vegetation and foliar nutrient concentrations on the photosynthetic rate (A), stomatal conductance (gs) and leaf water potentials (ψ) of sycamore (Acer pseudoplatanus L.), beech (Fagus sylvatica L.), spruce [Picea abies (L.) Karst.] and larch (Larix decidua Mill.) under controlled (well-watered/drought-stressed) conditions and under prevailing field conditions. While A and gs of well-watered spruce in the pot experiment were reduced by the mineral substrate, the organic dolomite substrate with dense competing vegetation reduced gs and ψ of sycamore, spruce and larch under drought-stressed conditions in the field. For sycamore and spruce, A and gs were strongly correlated with foliar nitrogen (N) and potassium (K) concentrations in the pot experiment. In contrast, soil water primarily affected beech and larch. Finally, dense competing vegetation negatively affected A and gs of spruce and A of larch on dolomite. Our results highlight the critical role of N, K and water availability for tree seedlings in shallow soils on calcareous bedrock. On these sites, natural tree regeneration is at particular risk from episodic drought, a likely consequence of climate change.

Do water-limiting conditions predispose Norway spruce to bark beetle attack?

Drought is considered to enhance susceptibility of Norway spruce (Picea abies) to infestations by the Eurasian spruce bark beetle (Ips typographus, Coleoptera: Curculionidae), although empirical evidence is scarce. We studied the impact of experimentally induced drought on tree water status and constitutive resin flow, and how physiological stress affects host acceptance and resistance. We established rain-out shelters to induce both severe (two full-cover plots) and moderate (two semi-cover plots) drought stress. In total, 18 sample trees, which were divided equally between the above treatment plots and two control plots, were investigated. Infestation was controlled experimentally using a novel 'attack box' method. Treatments influenced the ratios of successful and defended attacks, but predisposition of trees to infestation appeared to be mainly driven by variations in stress status of the individual trees over time. With increasingly negative twig water potentials and decreasing resin exudation, the defence capability of the spruce trees decreased. We provide empirical evidence that water-limiting conditions impair Norway spruce resistance to bark beetle attack. Yet, at the same time our data point to reduced host acceptance by I. typographus with more extreme drought stress, indicated by strongly negative pre-dawn twig water potentials.

Modeling of nitrogen dynamics in an Austrian alpine forest ecosystem on calcareous soils: a scenario-based risk assessment under changing environmental conditions.

We modeled the behavior of an Austrian alpine forest ecosystem on calcareous soils under changing climate and atmospheric nitrogen deposition scenarios. The change of nitrate leaching, emission rates of nitrogen compounds, and forest productivity were calculated using four process-oriented models for the periods 1998-2002 and 2048-2052. Each model reflects with high detail a segment of the ecosystem: PnET-N-DNDC (photosynthesis-evapotranspiration-nitrification-denitrification-decomposition; short-term nitrogen cycling), BROOK90 (water balance for small and homogenous forest watersheds), HYDRUS (water flux in complex and heterogenous soils), and PICUS v1.3 (forest productivity). The nitrogen balance model (NBM) combines the individual results into a comprehensive picture and extends the specific values beyond the limits of the individual models. The evaluation of the findings was outlined with TRACE, a model enabling a long-term prognosis of nitrogen cycling in annual time steps. Temperature increase and nitrogen input are influenced by various components and processes of the forest ecosystem. An increase of the temperature of 2.5 degrees C led to an enhancement of the N2O emission rates and affected the mineralization and the nitrification rates with the consequence of increased nitrate leaching into the subsoil. Enhanced nitrogen input also showed notable effects on nitrate leaching.