Environmental gradients and optimal fixation time revealed with DNA metabarcoding of benthic sample fixative.

Assessments of biodiversity and ecosystem status can benefit from DNA metabarcoding as a means to streamline sample processing and specimen identification. Moreover, processing the fixation medium instead of the precious material introduces straightforward protocols that allow subsequent focus on certain organisms detected among the preserved specimens. In this study, we present a proof of concept via the analysis of freshwater invertebrate samples from the Tatra Mountain lakes (Slovakia).

The concentration of organic nitrogen in mountain lakes is increasing as a result of reduced acid deposition and climate change.

The ionic and nutrient composition of mountain lakes recovering from atmospheric acidification is increasingly influenced by climate change (increasing air temperature and frequency of heavy rainfall events). We investigated the evolution of organic nitrogen (ON), dissolved organic carbon (DOC) and phosphorus (P) concentrations in alpine lakes in the Tatra Mountains (Central Europe) between 1993 and 2023, resulting from changes in climate and the ionic composition of atmospheric deposition. Our results suggest that the decreasing acidity of precipitation and the climatically induced increasing frequency of heavy rainfall events and air temperatures fluctuating around the freezing point have the potential to increase ON concentrations in alpine lakes despite decreasing deposition of inorganic N.

Cold mountain stream chironomids (Diptera) of the genus Diamesa indicate both historical and recent climate change.

Chironomids of the genus Diamesa (Meigen, 1835, Diptera: Chironomidae) inhabit cold, oxygen-rich running waters. We have investigated the presence of Diamesa and other freshwater macroinvertebrates at 22 stream sampling sites in 3 European high mountain regions (the Central Pyrenees, the Ötztal Alps, and the Tatra Mountains) to establish suitable temperature conditions for Diamesa dominance. It has been generally accepted that their high abundance was linked to the presence of glaciers; however, we have shown that in the Tatra Mountains, where there are no glaciers, the conditions for the dominance of Diamesa species are created due to permanent snowfields, the geographical orientation of the valley and shading by the surrounding high peaks.

Undeveloped till soils in scree areas are an overlooked important phosphorus source for waters in alpine catchments.

Scree deposits in alpine catchments contain undeveloped till soils that are "hidden" between and under stones. These scree areas have no vegetation except for sparse lichen patches on stone surfaces, but the soils exhibit biological activity and active cycling of nitrogen (N), phosphorus (P), and organic carbon (C). We compared the chemical and biochemical properties of till soils in the scree areas (scree soils) with developed soils in alpine meadows (meadow soils) of 14 catchments in the alpine zone of the Tatra Mountains.

Carbon and nutrient pools and fluxes in unmanaged mountain Norway spruce forests, and losses after natural tree dieback.

Forest areas infected by insects are increasing in Europe and North America due to accelerating climate change. A 2000-2020 mass budget study on major elements (C, N, P, Ca, Mg, K) in the atmosphere-plant-soil-water systems of two unmanaged catchments enabled us to evaluate changes in pools and fluxes related to tree dieback and long-term accumulation/losses during the post-glacial period. A bark-beetle outbreak killed >75 % of all trees in a mature mountain spruce forest in one catchment and all dead biomass was left on site.

Surviving trees are key elements in the fate of ectomycorrhizal community after severe bark-beetle forest disturbance.

Bark beetle disturbances are a critical event in the life cycle of Norway spruce forests. However, our knowledge of their effects on ectomycorrhizal fungi (EMF), which play a key role in forest productivity and nutrient cycling, is still incomplete. Special attention has been paid to the dynamics and diversity of EMF communities in managed forests, but studies dealing with disturbed natural stands are underrepresented.

Accelerated recovery of lake macroinvertebrates in the third decade since the reversal of acidification.

Chemical reversal from acidification has been progressing in European freshwaters since the late 1980s, responding to successful control of atmospheric pollution by acidifying emissions. However, biological recovery is often delayed after improvements in water composition. We studied macroinvertebrate recovery from acidification in eight glacial lakes in the Bohemian Forest (central Europe) between 1999 and 2019.

Aquatic quillworts, and under acidic stress-A review from a temperate refuge.

Quillworts () represent highly specialized flora of softwater lakes, that is, freshwater ecosystems potentially sensitive to acidification. In this paper, we combine a review of previous studies and our new results to address unrecognized reproduction strategies of quillworts to overcome long-term environmental stresses. These strategies play an important role in the plant's ability to overcome atmospheric acidification of freshwaters, protecting the plants until their environment can recover.

Soil warming during winter period enhanced soil N and P availability and leaching in alpine grasslands: A transplant study.

Alpine meadows are strongly affected by climate change. Increasing air temperature prolongs the growing season and together with changing precipitation patterns alters soil temperature during winter. To estimate the effect of climate change on soil nutrient cycling, we conducted a field experiment.

Cleaner air reveals growing influence of climate on dissolved organic carbon trends in northern headwaters.

Surface water browning, the result of increasing concentrations of dissolved organic matter (DOM), has been widespread in northern ecosystems in recent decades. Here, we assess a database of 426 undisturbed headwater lakes and streams in Europe and North America for evidence of trends in DOM between 1990 and 2016. We describe contrasting changes in DOM trends in Europe (decelerating) and North America (accelerating), which are consistent with organic matter solubility responses to declines in sulfate deposition.

Forest damage and subsequent recovery alter the water composition in mountain lake catchments.

Forest damage by insect infestation directly affects the trees themselves, but also indirectly affects water quality via soil processes. The changes in water composition may undergo different pathways depending on site-specific characteristics and forest components, especially the proportion of coniferous and deciduous trees. Here, we test whether changes in forest components and the intensity of disturbance can predict the chemical properties of water outflow from affected lake catchments.

Identifying factors that affect mountain lake sensitivity to atmospheric nitrogen deposition across multiple scales.

Increased nitrogen (N) deposition rates over the past century have affected both North American and European mountain lake ecosystems. Ecological sensitivity of mountain lakes to N deposition varies, however, because chemical and biological responses are modulated by local watershed and lake properties. We evaluated predictors of mountain lake sensitivity to atmospheric N deposition across North American and European mountain ranges and included as response variables dissolved inorganic N (DIN = NNH + NNO) concentrations and phytoplankton biomass.

Diverse effects of accelerating climate change on chemical recovery of alpine lakes from acidic deposition in soil-rich versus scree-rich catchments.

The current recovery of mountain lakes from atmospheric acidification is increasingly affected (both accelerated and/or delayed) by climate change. We evaluated long-term trends in the ionic composition of 30 lakes situated in the alpine zone of the Tatra Mountains, and compared the rates of their recovery with model (MAGIC) simulations done 20 years ago for the 2003-2020 period. The observed recovery was faster than the model forecast, due to greater reductions in acidic deposition than projected.

Disruptions and re-establishment of the calcium-bicarbonate equilibrium in freshwaters.

During recent decades, increasing anthropogenic activities have affected natural ionic composition, including the strongest and most common relationship between ionic concentrations in the majority of natural global freshwaters, i.e., the Ca-ANC (acid neutralizing capacity) equilibrium.

Changes in microclimate and hydrology in an unmanaged mountain forest catchment after insect-induced tree dieback.

Hydrological and microclimatic changes after insect-induced tree dieback were evaluated in an unmanaged central European mountain (Plešné, PL) forest and compared to climate-related changes in a similar, but almost intact (Čertovo, CT) control forest during two decades. From 2004 to 2008, 93% of Norway spruce trees were killed by a bark beetle outbreak, and the entire PL area was left to subsequent natural development. We observed that (1) climate-related increases in daily mean air temperature (2 m above ground) were 1.

Solar Radiation as the Likely Cause of Acid-Soluble Rare-Earth Elements in Sediments of Fresh Water Humic Lakes.

We studied photochemically induced precipitation of rare-earth elements (REEs) in water from a tributary to Plešné Lake and a tributary to Jiřická Pond, Czech Republic. Both tributaries had high concentrations of dissolved organic matter (∼1.8 mmol C L).

Widespread diminishing anthropogenic effects on calcium in freshwaters.

Calcium (Ca) is an essential element for almost all living organisms. Here, we examined global variation and controls of freshwater Ca concentrations, using 440 599 water samples from 43 184 inland water sites in 57 countries. We found that the global median Ca concentration was 4.

The chemical composition of forest soils and their degree of acidity in Central Europe.

We conducted an extensive screening of forest soils in the whole area of the Czech Republic to determine their degree of acidification and potential degradation. Soils were sampled at 480 forest sites (in a 7 × 7 km grid covering the entire Czech Republic) from the upper 30-cm layer and included both organic and mineral horizons. Based on values of water extractable pH (pH), cation exchange capacity (CEC) and base saturation (BS), soils were divided into three categories by their degree of acidity, i.

Decreasing litterfall mercury deposition in central European coniferous forests and effects of bark beetle infestation.

We evaluated a 14-year trend (2003-2017) in mercury (Hg) concentrations and fluxes in six litterfall categories (needles, bark, twigs, cones, lichen, and a mixture of unidentified fragments) at six research plots situated in two central European unmanaged mountain forest stands, dominated by mature Norway spruce. One of the stands (catchment of Plešné Lake, PL) was infested by bark beetle and all mature spruces died at three of four research plots during the study. One PL plot and two plots in the second stand (catchment of Čertovo Lake, CT) were intact and used as a control.

Photochemical degradation of dissolved organic matter reduces the availability of phosphorus for aquatic primary producers.

In situ experiments were done to determine the effects of the photochemical degradation of dissolved organic matter (DOM) and subsequent formation of particulate matter on dissolved phosphorus (P) concentrations in surface waters. Filtered (1.2 or 0.

Factors Affecting the Leaching of Dissolved Organic Carbon after Tree Dieback in an Unmanaged European Mountain Forest.

Forest disturbances affect ecosystem biogeochemistry, water quality, and carbon cycling. We analyzed water chemistry before, during, and after a dieback event at a headwater catchment in the Bohemian Forest (central Europe) together with an un-impacted reference catchment, focusing on drivers and responses of dissolved organic carbon (DOC) leaching. We analyzed data regarding carbon input to the forest floor via litter and throughfall, changes in soil moisture and composition, streamwater chemistry, discharge, and temperature.

Multiple long-term trends and trend reversals dominate environmental conditions in a man-made freshwater reservoir.

Man-made reservoirs are common across the world and provide a wide range of ecological services. Environmental conditions in riverine reservoirs are affected by the changing climate, catchment-wide processes and manipulations with the water level, and water abstraction from the reservoir. Long-term trends of environmental conditions in reservoirs thus reflect a wider range of drivers in comparison to lakes, which makes the understanding of reservoir dynamics more challenging.

Increased spruce tree growth in Central Europe since 1960s.

Tree growth response to recent environmental changes is of key interest for forest ecology. This study addressed the following questions with respect to Norway spruce (Picea abies, L. Karst.

Long-term trends of phosphorus concentrations in an artificial lake: Socio-economic and climate drivers.

European freshwater ecosystems have undergone significant human-induced and environmentally-driven variations in nutrient export from catchments throughout the past five decades, mainly in connection with changes in land-use, agricultural practice, waste water production and treatment, and climatic conditions. We analysed the relations among concentration of total phosphorus (TP) in the Slapy Reservoir (a middle reservoir of the Vltava River Cascade, Czechia), and socio-economic and climatic factors from 1963 to 2015. The study was based on a time series analysis, using conventional statistical tools, and the identification of breaking points, using a segmented regression.

Trends in riverine element fluxes: A chronicle of regional socio-economic changes.

We show how concentrations of water solutes in the Vltava River (Czech Republic) and their riverine outputs from the catchment were modified by socio-economic changes, land use, and hydrology between 1960 and 2015. In the early 1960s, HCO and Ca were the dominant ions. During 1960-1989 (a period of planned economy with an over-use of synthetic fertilizers, excessive draining of agricultural land and little environmental protection), the riverine concentrations of strong acid anions (SAAs: SO, NO, and Cl) increased 2-4-fold and their leaching was accompanied for by a 1.