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Stable isotopes are increasingly being used in many scientific fields, including environmental sciences. In this study we measured the variation in the stable hydrogen and oxygen isotope composition of fog water, rain water (in the form of bulk falling precipitation) and throughfall water in the Sumava (the Bohemian Forest), Krkonose (the Giant Mts.) and Jizerske hory (the Jizera Mts.) Mts. in October-November 2017. In total, 46 cumulative two-week samples were collected and analysed. Our results indicate that the overall stable hydrogen and oxygen isotope composition of fog and rain samples differed significantly, fog being isotopically enriched in the heavier isotopes 2H and 18O relative to rain. In contrast to our assumption, throughfall water was generally depleted in the heavier isotopes 2H and 18O relative to rainwater. Hence, the simple mixing model for most samples yielded an unrealistic percentage outside the reasonable range of 0–100%. For few samples, however, the estimated contribution of fog to throughfall ranged between 3 and 8% based on δ2H and 4 and 7% based on δ 18O, which is lower than that estimated for the same mountain regions by other authors using different methods and significantly lower than that reported for mountain ranges in neighbouring countries. Although using stable isotopes is a promising tool for determining the contribution of fog to the hydrological budget when assessing atmospheric deposition, the critical limitations are in the collection, manipulation and storing of the samples.

Soils represent important pools of soil organic carbon (SOC) that can be greatly influenced by labile C inputs, which are expected to increase in future due to CO2 enrichment of atmosphere and a concomitant rise in plant primary productivity. Studying effects of variable labile C inputs on SOC pool helps to understand how soils respond to global change. However, this knowledge is missing for coniferous forest soils despite being widespread throughout the northern temperate zone. We conducted a 7-month field manipulation experiment to study the effects of variable labile C inputs (simulated by additions of C4 sucrose) on the C content in soil fractions and on microbial abundance in the organic (O), surface mineral (A), and subsoil mineral (B) horizons of a temperate coniferous forest soil. SOC in less-protected soil fractions and total organic C were substantially decreased by labile C additions that simulated future increases in C inputs. The SOC losses were comparable between the A and B horizon (40% vs. 30%). However, because sucrose availability estimated from its incorporation into soil fractions and microbial biomass sharply decreased with soil depth, the loss of C was higher in the B than in the A horizon when related to the amount of sucrose added. Utilization of sucrose was highest by fungi in the O horizon and by bacteria in the mineral soil horizons. The results indicate that future increases in labile C inputs to coniferous forest soils will cause rapid and substantial losses of SOC in both the surface and subsoil mineral horizons.

Labile C input to the soil can cause the priming effect (PE) that in turn changes the soil organic C (SOC) content. However, little information is available to predict the magnitude of the PE in different soils, especially under concurrent changes in nutrient inputs. We took advantage of a natural gradient in labile C input in the surroundings of wood ant nests in a temperate coniferous forest which arises through the long-term effects of wood ant foraging on the inputs of honeydew to soil. We collected soils from the surface mineral horizon (high-SOC content) (A horizon) and the subsoil mineral horizon (low-SOC content) (B horizon) at 4 m (low labile C input and higher SOC content) and 70 m (high labile C input and lower SOC content) from four nests. In a 6-month laboratory microcosm experiment, we monitored microbial activity and PE as affected by no nutrient addition (control) or fortnightly additions of labile C alone or in combination with N and/or P (C, CN, CP, CNP). Microbial activity and PE after C addition increased more at 70 m than at 4 m in the B horizon, that is, were higher with a lower SOC content. However, microbial activity and PE in the B horizon were not affected by additions of N and/or P with C. In the A horizon, microbial activity and PE were lower after combined CN addition but increased by combined CP addition relative to C addition alone. In conclusion, labile C inputs had a larger effect on decomposition and PE in low-SOC than high-SOC soils, whereas N and P inputs had greater effects in high-SOC soils than in low-SOC soils. This suggests that low-SOC soils such as those subjected to a high long-term labile C input or those from the subsoil mineral horizon might be more susceptible to increase microbial activity in relation to changes in labile C inputs but less susceptible in relation to changes in N and P inputs relative to high-SOC soils.

Labile carbon (C) input to soils is expected to affect soil organic matter (SOM) decomposition and soil organic C (SOC) stocks in temperate coniferous forests. We hypothesized that the SOM decomposition rate, C content in soil fractions, and microbial and faunal abundance and activity were increased along the gradient in labile C input around wood ant nests. Three distances from the nest that differed in annual labile C input to soil were selected: 4 m with 6379 mg C m−2, 30 m with 9060 mg C m−2, and 70 m with 9215 mg C m−2. Soil from the organic horizon (Oe+Oa), surface mineral horizon (A), and subsoil mineral horizon (B) was analyzed for C content in soil fractions and for activity and abundance of soil microorganisms and fauna. In addition, a 1-year litter-bag and soil-bag decomposition experiment was conducted. Although the rate of soil decomposition did not differ along the labile C input gradient, the rate of litter decomposition in the B horizon increased as labile C input increased with distance from the nest. Correspondingly, the C content in bulk soil and in the labile and less-protected soil fractions in the B horizon decreased as labile C input increased. We infer that, because the O and A horizons are less C-limited than the B horizon, the changes in the labile C input along the gradient affected the B horizon more than the surface O and A horizons. However, soil microbial and faunal activity and abundances were not consistently affected by the gradient. Apparently, C stocks in soil fractions are more important for microbial and faunal communities than labile C inputs. Although the results indicate that SOC content changes very slowly in the coniferous forest soil of the current study, increases in the input of natural labile C leads to decreases in the SOC stock in the B horizon. By increasing the labile C input to temperate forest soils, future increases in atmospheric CO2 concentration may therefore lead to a significant loss of SOC in deep soil layers.

Wood ants are common in temperate forests, and while building their nests and foraging for food, they transfer large amounts of organic matter and nutrients. Here, we tested the hypothesis that wood ants generate natural gradients of labile carbon (C) inputs into the soil surrounding their nests. We selected five medium-sized wood ant (Formica aquilonia) nests in a coniferous temperate forest and established sampling points at distances of 4, 30 and 70 m from each nest. Throughfall (honeydew + aboveground vegetation leachates) and litterfall were collected regularly during a vegetative season and were analysed for labile organic C content. In addition, soil from the organic horizon (Oe + Oa), surface mineral horizon (A) and subsoil mineral horizon (B) was collected and analysed for organic matter and nutrient contents. The labile C input in throughfall increased with distance from the nest (it was 1.5-fold greater at 70 m than at 4 m). C input changed during the vegetative season and was highest in June. Litterfall was not affected by the distance from the nest. Organic matter and nutrient contents were unaffected by distance from the nest in surface soil horizons but were significantly higher near the nest (4 m) than 70 m from the nest in the subsoil mineral horizon, suggesting that surface soils are less affected by the labile C inputs than subsoils. Finally, we suggest that the gradients in labile C input surrounding wood ant nests can be used to study the effects of labile C input changes on soil properties.

Factors shaping community structure of soil microbiota have been intensively studied; however, the pattern in community composition and structure of soil microbiota at large geographical scales and factors regulating its metabolic activity remains poorly understood. Here, we used a field transplantation experiments to investigate the effects of substrate and climatic conditions on basal soil respiration, microbial biomass C and diversity of soil microbiota by comparing local and transplanted soils along a latitudinal gradient. Soil samples collected in April 2008 at donor site (Sokolov, Czech Republic) in Central Europe were gamma-ray sterilized and transplanted to receptor sites in Europe and the USA in May and early June 2008. Soil samples were taken in June 2009 after one year of exposure and immediately prepared for laboratory analysis. Basal soil respiration in local soils increased from 22 to 42 mg CO2-C kg−1 h−1 with latitude while basal soil respiration in transplanted soils decreased with latitude from 32 to 19 mg CO2-C kg−1 h−1. The microbial biomass C in both transplanted and local soils decreased with latitude. Content of fungal and bacterial phospholipid fatty acids increased nearly twice with latitude in local soils. Shannon diversity index of fungal community decreased from 2.5 to 1.2 along the latitudinal gradient in transplanted soils while local soils increased from 0.9 to 2.4 with latitude. Based on our results, microbial activity is driven mainly by changes of the soil substrate along latitudinal and climatic gradients while microbial biomass is driven more by global climatic factors itself. The diversity of soil microbial communities is mostly affected by latitudinal and climatic factors while community structure is mostly shaped by substrate quality.

Microbial interconnections in soil are pivotal to ecosystem services and restoration. However, little is known about how soil microbial interconnections respond to slash-and-burn agriculture and to the subsequent ecosystem restoration after the practice. Here, we used amplicon sequencing and co-occurrence network analyses to explore the interconnections within soil bacterial and fungal communities in response to slash-and-burn practice and a spontaneous restoration (spanning ca. 60 years) of tropical forests after the practice, in Papua New Guinea. We found significantly higher complexity and greater variations in fungal networks than in those of bacteria, despite no significant changes observed in bacterial or fungal networks across successional stages. Within most successional stages, bacterial core co-occurrences (co-occurrences consistently present across all sub-networks in a stage) were more frequent than those of fungi, indicating higher stability of interconnections between bacteria along succession. The stable interconnections occurred frequently between bacterial taxa (i.e. Sporosarcina, Acidimicrobiale and Bacillaceae) and between ectomycorrhizal fungi (Boletaceae and Russula ochroleuca), implying important ecological roles of these taxa in the ecosystem restoration. Collectively, our results provide new insight into microbial interconnections in response to slash-and-burn agriculture and the subsequent ecosystem restoration, thus promoting a better understanding of microbial roles in ecosystem services and restoration.

Coniferous forest ecosystems are important pools of soil organic carbon (SOC) in the Northern temperate zone. Needle leachates and root exudates represent a significant input of C to these soils and can differently affect soil C cycling because of their differences in chemistry and stoichiometry. This is the first study to investigate the differences in the flow of dissolved organic C (DOC) in the form of needle leachates, root exudates, and their combination through a forest mineral topsoil. We conducted a 5-month microcosm experiment with ecologically relevant additions of 13C-labelled spruce-derived substrates. The proportion of DOC lost from or incorporated into the mineral soil as microbial biomass or soil fractions (free, occluded by or adsorbed onto mineral particles) as well as differences in the priming effect (PE) caused by the two substrates were assessed. Needle leachates (higher in phenolics and C:N ratio) were less utilized by the microbial community than root exudates but caused a higher PE probably because they lacked sufficient N to satisfy microbial N demands. The addition of either substrates failed to change microbial community composition or SOC content in soil fractions. Most of the substrate C in soil fractions was stabilized by adsorption onto mineral particles. On average, 69% of the substrate C was lost via mineralization; only 0.23% via leaching. The most important C pool related to substrate C gain was the C stored in soil fractions (29%); only 1.7% was stored in the microbial biomass. A consideration of all C gains and losses indicates that the addition of spruce-derived substrates resulted in an average net substrate C retention of 31%.

The majority of studies that investigate plant functional trait effects on ecosystem properties use traits obtained from databases. However, we know little regarding their explanatory power proportionate to that of the semi-quantitative vegetation properties, and much less still is known when considering their temporal changes in a chronosequence. We determined whether soil chemical and biological properties were associated with plant functional traits, observed vegetation properties (“patch type” = bare soil, grassy, woody), and site age (10, 18, 28, and 55 years), at four spontaneously overgrown post-mining locations in the Czech Republic. Abiotic soil properties were expected to be closely related to the site age, while above and below ground macrofauna (epigeic and endogeic, respectively), mesofauna, and microbial biomass were expected to be related to the plant functional traits and patch types. Site age and plant functional traits were more important explanatory factors for most of the chemical, microbial, and macrofaunal soil properties than the patch types. Patch type was the only plant-related factor capable of explaining the mesofauna community variations. Epigeic macrofauna were found to correlate more strongly with the plant functional traits than endogeic macrofauna. The abundance of most fauna correlated positively with an increase in plant cover and litter input and was significantly higher in vegetated patches and old sites.

Topsoil layer contains various components of soil organic matter such as branches, leaves, bark, or metabolites and residues of soil biota. Soil organic matter (SOM) in forest ecosystems consists mostly of lignin, cellulose, chitin and other hydrocarbons. These compounds are decomposed mainly by soil fungi which produce extracellular enzymes to decompose wide range of organic residues. These enzymes may alter nutrient cycling and change soil properties such as water retention capacity, ion exchange capacity, formation of soil microstructure, soil microbial respiration, etc. In this study, we studied enzyme activity in the topsoil layer of postmining spoil heaps near Sokolov, Czech Republic. We investigated the effect of the following factors and their combinations on enzyme activity: i) dominant vegetation, ii) time of sampling, iii) reclamation, and iv) soil macrofauna.We measured enzyme activity in plastic mesocosms with autochthonous litter deposited on reclaimed and unreclaimed post-mining sites. We used mesocosms accessible for macrofauna (mesh size > 2 mm) and mesocosms inaccessible for macrofauna (mesh size < 2 mm). Under laboratory conditions, we measured enzyme activity (laccase, oxidase, peroxidase, Mn-peroxidase, alkaline phosphatase, acid phosphatase, endoglucanase, xylanase, cellobiohydrolase, glucosidase, xylosidase and chitinase) using buffer extraction method followed by spectrophotometric assay. We did not find any statistically significant difference between mesocosms accessible and inaccessible for fauna. However, we found significant effect of time of sampling on enzyme activity. Our results showed significant difference between reclaimed and unreclaimed post-mining sites. Reclaimed sites showed significantly higher enzyme activity than unreclaimed sites.

Transplantation of soil and plant litter has been suggested as a tool to speed up the establishment of target communities during restoration. In this study, we explored the effect of transplanting soil and plant litter on plant and soil biota communities in an already afforested limestone quarry. Soil or plant litter from a mature deciduous forest was transplanted into post-mining sites overgrown by 14-year-old deciduous trees planted here as part of a past reclamation effort. In this quarry six experimental sites were set up: three sites were fully fenced, while at the other three sites only individual planted trees were protected against deer by a wire mesh tightly surrounding the tree. One site from fully protecting regime and one site from partly protecting regime was treated with either (1) soil transplant addition, (2) plant litter addition, or was (3) not treated at all. We studied microbial, plant and animal communities, the latter with an emphasis on nematodes for their bioindication potential, and compared the experimental sites with a nearby semi-natural forest (or serie of releves from target habitats in case of plants) used as reference sites. The vegetation was sampled using standard phytosociological approach, the biomass of major microbial groups was assessed using PLFA, and free-living soil nematodes, soil mesofauna (in our case mainly springtails and mites), and soil macrofauna were sorted into elcological or taxonomical groups. Only nematodes and microbial communities differed among experimental sites, but none of the studied groups showed significant differences between individual transplanted treatments and samples from reference sites. When we used Canonical correlation analysis (CCA) followed by variation partitioning, we found that transplant treatment, fencing, or their interaction explained a significant portion of data variability in all groups except macrofauna. Only plants and nematodes were significantly affected by the treatments, whereas all groups (except macrofauna) were affected by location and fencing and also by the interaction of all above mentioned factors. In cases where these interactions were significant, soil transplant treatments showed higher similarity to the reference than the control without any soil or plant litter. This suggests that soil transplantation may speed up recovery of forest soils and understorey above it in a reclaimed quarry, especially in case of plant communities, but the described effect is strongly modified by other environmental factors.

Soil microorganisms are recognized as key players in all biogeochemical cycles. However, little effort has been paid to incorporate them in predictive models for future climate change. Here, we investigated the variation of prokaryotic community composition in alpine meadow soil from the Qinghai-Tibet Plateau under dry-rewetting stress using MiSeq sequencing approach. We incubated soils treated by various frequencies of rewetting and durations of desiccation. Emission rates of methane, carbon dioxide and nitrous oxide were measured every week during five months of incubation, and soil samples were taken each month for community composition analysis. Our results revealed that soil prokaryotic community showed different response patterns to dry-wetting cycles. Diversity indices significantly increased in soils under short-term drought and soils rewetted after long-term drought. Higher niche partitioning was promoted by higher frequencies of disturbance and rapid physiological activation of inactive microbial communities during desiccation, allowing colonization by a diverse array of organisms. Null model percentage of NTI revealed a strong phylogenetic relatedness of soil prokaryotic communities across all treatments and incubation times, suggesting that desiccation and rewetting events were strong biological filters shaping community assemblies. Our results also indicated different responses of various genera belonging to same phylum. These results suggest that prokaryotes that are well adapted to extremely stressful conditions such as long-term desiccation may release more greenhouse gasses in a positive feedback loop and that this prospect should be considered when modeling climate change.

The arbuscular mycorrhizal (AM) grass Calamagrostis epigejos and predominantly ectomycorrhizal (EcM) tree Salix caprea co-occur at post-mining sites spontaneously colonized by vegetation. During succession, AM herbaceous vegetation is replaced by predominantly EcM woody species. To better understand the interaction of AM and EcM plants during vegetation transition, we studied the reciprocal effects of these species’ coexistence on their root-associated fungi (RAF). We collected root and soil samples from three different microenvironments: stand of C. epigejos, under S. caprea canopy, and contact zone where roots of the two species interacted. RAF communities and mycorrhizal colonization were determined in sampled roots, and the soil was tested for EcM and AM inoculation potentials. Although the microenvironment significantly affected composition of the RAF communities in both plant species, the effect was greater in the case of C. epigejos RAF communities than in that of S. caprea RAF communities. The presence of S. caprea also significantly decreased AM fungal abundance in soil as well as AM colonization and richness of AM fungi in C. epigejos roots. Changes observed in the abundance and community composition of AM fungi might constitute an important factor in transition from AM-dominated to EcM-dominated vegetation during succession.

In the Protected Landscape Area “Labské pískovce” (Czech Republic), there are many sandstone caves accessible by permission only and where climbing equipment is commonly required. The tradition of visiting the caves dates back to turn of the 19th and 20th centuries, and visitors traditionally record their visits in log-books. We have gathered attendance data from 12 caves from log-books and via survey (2-year form collection period). The attendance varied from less than 10 to ~650 visitors annually. Signs of inadequate behavior of visitors were observed, especially waste disposal and smoking in the caves. Sediment step-compression increased significantly the ratios of fungi/bacteria and gram-positive to gram-negative (G+/G−) phospholipid fatty acids (PLFA) as well as PLFA of actinobacteria and activities of sediment phosphatases, glucosidases, and peroxidases. The number of visitors was correlated positively with the G+/G− ratio and sediment nutrients but negatively with sediment moisture and the activity of peroxidases. The results indicate a significant effect of attendance on sediment microbial communities, most likely caused by the import of nutrients into caves. Hence, reconsideration of the cave attendance policy is recommended.