Tomáš Picek

Heterotrophic Fixation of CO2 in Soil

The occurrence of heterotrophic CO2 fixation by soil microorganisms was tested in several mineral soils differing in pH and two artificial soils (a mixture of silica sand, alfalfa powder, and nutrient medium inoculated with a soil suspension). Soils were incubated at ambient (∼0.05 vol%) and elevated (∼5 vol%) CO2 concentrations under aerobic conditions for up to 21 days. CO2 fixation was detected using either a technique for determining the natural abundance of 13C or by measuring the distribution of labeled 14C-CO2 in soil and bacteria. The effects of elevated CO2 on microbial biomass (direct counts, chloroform fumigation extraction method), composition of microbial community (phospholipid fatty acids), microbial activity (respiration, dehydrogenase activity), and turnover rate were also measured. Heterotrophic CO2 fixation was proven in all soils under study, being higher in neutral soils. The main portion of the fixed CO2 (98–99%) was found in extracellular metabolites while only ∼1% CO2 was incorporated into microbial cells. High CO2 concentration always induced an increase in microbial activity, changes in the composition of the microbial community, and a decrease in microbial turnover. The results suggest that heterotrophic CO2 fixation could be a widespread process in soils.

Chemical and Biochemical Characteristics of Alpine Soils in the Tatra Mountains and their Correlation with Lake Water Quality

AbstractSoils and lakes were sampled in fifteen catchments in the alpinezone of the Tatra Mountains (Slovak-Polish border) to evaluate the dependence of lake water chemistry on soil properties. The amount of soil in alpine meadows varied from 38 to 255 kg m-2 (dry weight soil <2 mm; average of 121 kg m-2). The average cation exchange capacity (CEC) was 12 eq m-2, average base saturation was 12%, and average

Different temperature sensitivity and kinetics of soil enzymes indicate seasonal shifts in C, N and P nutrient stoichiometry in acid forest soil

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Ecological implications of organic carbon dynamics in the traps of aquatic carnivorous Utricularia plants

was 4.0. Moraine areas had, on average, 13 kg m-2 of <2 mm soil in small deposits between stones. Their chemical properties were similar to mineral horizons of alpine soils but had higher concentrations of P forms. Soil composition was spatially uniform, having coefficientsof variation of all parameters between 5 and 115%, and did not exhibit significant differences between the catchments or along the elevation gradient. Variation in pools of soil constituents was ∼2-fold higher. Soil organic matter concentration was theparameter that most strongly and positively correlated with N, P, S, CEC, exchangeable base cations, exchangeable acidity, and all biochemical parameters (C, N, and P in microbial biomass and C and N mineralisation rates). Lake water concentrations of organic C, N, and total P were positively correlated (P < 0.01) with the pool of soil organic matter in the catchments, while NO3- concentrations were negatively correlated (P < 0.001). No correlations were found between C, N, and P concentrations in lakes and soil chemistry, indicating the dominant role of soil quantity over quality for surface water composition in the Tatra lakes. Relatively high concentrations of Ca2+, Na+, SO42-, reactive Si, and acid neutralising capacity in some lakes were not explained by soil characteristics, and were more probably related to bedrock composition and structure.

Methane and carbon dioxide flux in the profile of wood ant (Formica aquilonia) nests and the surrounding forest floor during a laboratory incubation

Background: Northern peatlands are known for having significant stocks of terrestrial soil carbon (C). However, little is known about how peatlands function under various land uses and what impacts land-use change has on their functioning in central Europe. Aim: The objective of our study was to quantify the variability and controls of typical plant communities in terms of C gas dynamics on bogs and fens affected by a changed hydrological regime in the Bohemian Forest, Czech Republic. Methods: Carbon dioxide (CO2) exchange and methane emissions (CH4) were measured in bogs (pristine, drained, restored) and in fens (pristine, drained) during the 2009 growing season. We applied cluster analysis to define plant communities and non-linear response models to quantify the variation in CO2 dynamics among the communities. Results : Drainage had a strong impact on vegetation; forest and meadows species were dominant on drained peatland sites and the vascular green area was higher than on pristine sites. The net ecosystem CO2 exchange (NEE) varied from –27 to 241 g CO2–C m−2 per growing season on the bogs and from 27 to 153 g m−2 on the fens. The most-drained parts of the bog and fen with the most changed vegetation structure acted as both net C sources and very weak C sinks; however, areas dominated by Molinia caerulea acted as a strong C sink. Plant communities on the wetter parts of drained sites had a positive seasonal NEE, comparable with NEE on pristine sites. Seasonal CH4 emissions were relatively low (0–9 g CH4–C m−2) at all sites and did not influence net C balance, with the exception of pristine fen where CH4 emissions with average 90 g C m−2 led to a negative total growing season C balance. Water regime restoration caused neither a significant change in plant composition nor any major changes, such as plant die-back or increased CH4 emissions during the first season after restoration. Conclusions: Our results showed that C gas fluxes, and in turn the C balance of the whole ecosystem, were largely determined by plant community type. Drainage did not necessarily lead to a negative ecosystem C balance; however, a significant change of species composition occurred on most drained areas. The less-drained parts on drained sites, where original peatland species and original functions are preserved, could facilitate future ecosystem restoration.

Cotton-Grass and Blueberry have Opposite Effect on Peat Characteristics and Nutrient Transformation in Peatland

Acid forest soils in the Bohemian Forest in Central Europe are biogeochemically imbalanced in organic C, N and P processing. We hypothesized that these imbalances can be due to different temperature sensitivities of soil enzyme activities and their affinities to substrate in litter and organic soil horizons. We measured potential activities of five main soil enzymes (β-glucosidase, cellobiohydrolase, Leu-aminopeptidase, Ala-aminopeptidase, and phosphatase) responsible for organic carbon, nitrogen and phosphorus acquisition. We also modeled potential in situ enzyme activities and nutrient release based on continuous in situ temperature measurements. We determined basic kinetic parameters (Km, Vmax), enzyme efficiencies (kcat) and temperature sensitivities (Ea and Q10) according to Michaelis–Menten kinetic and modified Arrhenius models. Our results showed significant differences in substrate affinities between the litter and organic soil horizons. Higher aminopeptidase affinity (lower Km) in the litter soil horizon can lead to leaching of peptidic compounds to lower soil horizons. β-Glucosidase and phosphatase showed high temperature response following the Arrhenius model. However, both aminopeptidases showed no or even decreased activity with increasing temperature. The aminopeptidase temperature insensitivity means that peptidic compounds are degraded at the same or even lower rate in warmer and colder periods of the year in acid forest soils. This imbalance results in different release of available nutrients from plant litter and soil organic matter which may affect bacterial and fungal community composition and nutrient leaching from these ecosystems.

Seasonal and Spatial Dynamics of Gas Ebullition in a Temperate Water‐Storage Reservoir

Plant–microbe interactions actively control nitrogen (N) cycling in the ecosystem. We hypothesize that the investment into exudation and the coupling of plant–microbe N cycling will be larger in competitive plants compared to the more conservative species. Root exudation of competitive (Glyceria maxima) and conservative (Carex acuta) plants was estimated by 13C-CO2 labeling. Seasonal changes in plant, microbial, and soil soluble N pools as well as potential net microbial N transformations were determined to interconnect the C and N cycling within grassland ecosystems dominated by these species. We showed that competitive Glyceria, as compared to conservative Carex, appears to affect soil N cycling through a more direct temporal and spatial influence on soil microbes due to a larger investment into root exudation. This makes the system highly dynamic, with faster soil N cycling and pronounced seasonal N redistribution between plants and microbes. The conservative Carex, irrespective of its larger root system, invested less C to exudation. In this case, the plant–microbe relationships appear to be less-coupled in time and space with the plant N supply likely relying mainly on the relatively slow microbial mineralization of organic matter than on rhizosphere priming effect. We showed that differences in soil N cycling associated with competitive versus conservative plants are closely connected with their different investments into root exudation, which govern the coupling of plant–microbe interactions in time and space.

Species effects and seasonal trends on plant efflux quantity and quality in a spruce swamp forest

Rootless aquatic carnivorous Utricularia exude up to 25% of their photosynthates into the trap lumen, which also harbours a complex microbial community thought to play a role in enhancing Utricularia nutrient acquisition. We investigated the composition of organic carbon in the trap fluid, its availability for microbial uptake, the influence of plant nutrient status and trap age on its biodegradability, and the composition of prokaryotic assemblages within the traps of three aquatic Utricularia species. Using ion chromatography and basal respiration rate measurements we confirmed that up to 30% of total dissolved organic carbon in Utricularia trap fluid in oligotrophic conditions was easily biodegradable compounds commonly found in plant root exudates (mainly glucose, fructose and lactate). The proportion of these compounds and their microbial utilisation decreased with increasing mineral nutrient supply and trap age. Fluorescence in situ hybridisation analyses showed that microbial trap assemblages are dominated by alpha and beta Proteobacteria, and that the assemblage composition is affected by changes in the ambient mineral nutrient supply. We suggest that organic carbon dynamics within the traps, involving both the plant and associated microbial assemblages, underlies the acquisition of key nutrients by Utricularia and may help explain the evolutionary success of the genus.