Jan Frouz

Soil food web properties explain ecosystem services across European land use systems

Intensive land use reduces the diversity and abundance of many soil biota, with consequences for the processes that they govern and the ecosystem services that these processes underpin. Relationships between soil biota and ecosystem processes have mostly been found in laboratory experiments and rarely are found in the field. Here, we quantified, across four countries of contrasting climatic and soil conditions in Europe, how differences in soil food web composition resulting from land use systems (intensive wheat rotation, extensive rotation, and permanent grassland) influence the functioning of soils and the ecosystem services that they deliver. Intensive wheat rotation consistently reduced the biomass of all components of the soil food web across all countries. Soil food web properties strongly and consistently predicted processes of C and N cycling across land use systems and geographic locations, and they were a better predictor of these processes than land use. Processes of carbon loss increased with soil food web properties that correlated with soil C content, such as earthworm biomass and fungal/bacterial energy channel ratio, and were greatest in permanent grassland. In contrast, processes of N cycling were explained by soil food web properties independent of land use, such as arbuscular mycorrhizal fungi and bacterial channel biomass. Our quantification of the contribution of soil organisms to processes of C and N cycling across land use systems and geographic locations shows that soil biota need to be included in C and N cycling models and highlights the need to map and conserve soil biodiversity across the world.

Soil biota and upper soil layer development in two contrasting post-mining chronosequences

Abstract Density and community composition of a wide spectrum of soil organisms (fungi, algae, testate amoebae, nematodes, enchytraeids, lumbricids, oribatid mites, diplopods, terrestrial isopods, collembolans and dipteran larvae), direct counts of bacteria, rate of cellulose decomposition and microstructure of upper soil layers were studied in two chronosequences of plots reclaimed from open-cast coal mining near Cottbus (Germany) and near Sokolov (Czech Republic). German plots were characterized by acidic sandy soils and afforested with pine, while the Czech plots possessed alkaline clay soils and were afforested with alder. In both chronosequences, density and species richness in most of investigated groups of soil biota gradually increased with increasing succession age. Typical pioneer species were found in initial stands of both chronosequences. Nevertheless, the initial stands supported poorer assemblages of soil biota in the Cottbus area than did those in the Sokolov area. The Cottbus area was characterized by a moor type of humus and by gradual uniform increase of abundances and species numbers of most studied groups of soil biota. On the contrary, moder type of humus and a more variable pattern of soil biota development during the course of succession were found in the Sokolov area. Slower development of soil biota in initial stages of succession in Cottbus is caused by unfavourable physical and chemical conditions of heap substrates, and by lower input and poor quality of litter in pine plantations.

Intensive agriculture reduces soil biodiversity across Europe

Soil biodiversity plays a key role in regulating the processes that underpin the delivery of ecosystem goods and services in terrestrial ecosystems. Agricultural intensification is known to change the diversity of individual groups of soil biota, but less is known about how intensification affects biodiversity of the soil food web as a whole, and whether or not these effects may be generalized across regions. We examined biodiversity in soil food webs from grasslands, extensive, and intensive rotations in four agricultural regions across Europe: in Sweden, the UK, the Czech Republic and Greece. Effects of land-use intensity were quantified based on structure and diversity among functional groups in the soil food web, as well as on community-weighted mean body mass of soil fauna. We also elucidate land-use intensity effects on diversity of taxonomic units within taxonomic groups of soil fauna. We found that between regions soil food web diversity measures were variable, but that increasing land-use intensity caused highly consistent responses. In particular, land-use intensification reduced the complexity in the soil food webs, as well as the community-weighted mean body mass of soil fauna. In all regions across Europe, species richness of earthworms, Collembolans, and oribatid mites was negatively affected by increased land-use intensity. The taxonomic distinctness, which is a measure of taxonomic relatedness of species in a community that is independent of species richness, was also reduced by land-use intensification. We conclude that intensive agriculture reduces soil biodiversity, making soil food webs less diverse and composed of smaller bodied organisms. Land-use intensification results in fewer functional groups of soil biota with fewer and taxonomically more closely related species. We discuss how these changes in soil biodiversity due to land-use intensification may threaten the functioning of soil in agricultural production systems.

Use of soil dwelling Diptera (Insecta, Diptera) as bioindicators : a review of ecological requirements and response to disturbance

Larvae of soil dwelling Diptera represent an important part of the edaphon in a wide range of ecosystems from climax forests to agroecosystems. Their abundance in soil varies from several hundred to several thousand individuals per square meter. They take part in many important biological processes in soil such as the decomposition of plant litter and nutrient cycling. Soil dwelling Diptera include groups and species that vary in size as well as in food and ecological demands. This paper summarizes data concerning their ecology and distribution in various natural and man made habitats and their reaction to stress factors. The response of a soil dwelling dipteran community can be evaluated in several ways, e.g., at the level of food web structure, species composition, or individual response of selected species. The possibilities of interpreting such data as well as perspectives for future research are discussed.

The effect of Lasius niger (Hymenoptera, Formicidae) ant nest on selected soil chemical properties

Summary The set of chemical properties: total, available and watersoluble P, total C, available K, Na, Ca and pH in H2O and KCl were studied in 64 nests of Lasius niger and in surrounding soils (control). Ant nests were located in wide range of soil conditions. Additionally, spatial distribution of those parameters was studied in three nests. The pooled average values for all investigated soil parameters, except that of Ca and C were significantly higher in the nests than in surrounding soil. At the same time, chemical properties of the nest were effected by chemical properties of surrounding soil; pH value in the nests increased in comparison to control in acidic soils but the opposite was true in alkaline soil. Content of available P in the nest was higher than in surrounding soil. As the content of available P in surrounding soil increased the enrichment of the nest (increase of available P in nest in comparison with control) was higher. Adjacent soils with low available Ca and total C supported nests that were higher in these elements while surrounding soil with higher Ca ans C supported nests that were lower in these elements. The changes in chemical properties were more pronounced in the aboveground than in the belowground part of the nest. The results indicates that the main processes taking part in chemical changes of soil in the ant nests are soil mixing due to excavation of deeper soil layers, enrichment of substrate by ants (by rest of food, excreta etc.) and interactions of nest chemistry with other physical, chemical and microbial parameters in the nest.

Application of ARDRA and PLFA analysis in characterizing the bacterial communities of the food, gut and excrement of saprophagous larvae ofPenthetria holosericea (Diptera: Bibionidae): a pilot study

Amplified ribosomal DNA restriction analysis (ARDRA) was used to compare the bacterial communities of the food, the gut sections (ceca, anterior and posterior midgut, hindgut) and the excrement of the litter feeding bibionid larvae ofPenthetria holosericea. For universal eubacterial primers ARDRA patterns were complex with only minor differences among samples. Taxon specific primers were also applied to characterize the samples. Fragment composition was transformed to presence/absence binary data and further analyzed. Cluster analysis revealed that bacterial communities of gut highly resembled each other with the exception of the ceca. ARDRA patterns of consumed leaves clustered together with the intact leaves but differed from those of the excrement. ARDRA results were compared with microbial community structure based on phospholipid fatty acid (PLFA) fingerprints. The cluster analysis of PLFA (presence/absence binary) data resulted in a pattern similar to the ARDRA data. The PCA analysis of PLFA relative content separated microbial communities into five groups: (1) anterior and posterior midgut, (2) hindgut, (3) ceca, (4) consumed and intact litter, (5) excrement. Both methods indicated that conditions in the larval gut result in formation of a specific microbial community which differs from both the food and excrement ones. Particularly ceca — (blind appendages, harbor very specific microbial community) are divided from the rest of the gut by perithropic membrane.

Influence of temperature on developmental rate, wing length, and larval head capsule size of pestiferous midge Chironomus crassicaudatus (Diptera: Chironomidae).

Abstract Larvae of Chironomus crassicaudatus Malloch were reared individually at nine constant temperatures from 12.5 to 32.5°C (2.5°C increments) for 120 d. Duration of immature stages (egg, four instars, and pupa), head capsule width of fourth instars, and wing length were recorded. Some adults emerged at all temperatures, except at 12.5°C where individuals developed to fourth instars during the experiment. Sharpe and DeMichele’s four-parameter model with high-temperature inhibition described the temperature-dependent developmental rates. The slowest development was observed at 15°C, with developmental rate peaking between 25 and 27.5°C. Developmental rate increased rapidly with increasing temperature up to 20°C, slowed between 20 and 27.5°C, and decreased at temperatures >27.5°C. No developmental inhibition at high temperatures was observed in eggs. The most apparent high-temperature inhibition of development was recorded in fourth instars, which comprised the largest proportion of developmental time. Males developed faster than females, but females had wider larval head capsules and longer wings than males. Adult size was negatively related with temperature in both sexes, but this relationship was steeper in males than in females. Larval size peaked at 20°C, whereas the head capsule width was reduced at temperatures higher and lower than 20°C.

Spatio-temporal effects of selected physico-chemical variables of water, algae and sediment chemistry on the larval community of nuisance Chironomidae (Diptera) in a natural and a man-made lake in central Florida

Spatio-temporal distributions of Chironomus crassicaudatus, Chironomus decorus, Glyptotendipes paripes, Cryptochironomus fulvus and Tanypodinae midge larvae and selected associated environmental variables (physico-chemical variables of water, sediment chemistry and algal composition) were studied for one year in natural Lake Monroe and man-made Konomac Lake in central Florida. Ordination analysis (CCA with variation partitioning) showed that in each lake, sediment variables were the most important environmental variables. However, the most important proportion of species variability in pooled data from both lakes was explained by lake-specific combinations of water, sediment and algal variables. Chironomid larvae were ordinated with increasing depth as follows: G. paripes, C. fulvus, C. crassicaudatus, Tanypodinae, and C. decorus. This trend was similar for both lakes individually as well as for the pooled data. As water depth increased, organic matter content and associated metals concentrations in sediment increased. Glyptotendipes paripes displayed significant, negative correlation with water depth and sediment total carbon content, while C. decorus showed a significant positive correlation with these variables; C. crassicaudatus did not show any significant correlation with either of these variables. The algal composition in the pooled data from both lakes was another important factor affecting the larval distributions. The proportion of G. paripes and C. decorus larvae increased with filamentous algal density, and C. crassicaudatus larvae with increasing Cyanobacteria. Although both study lakes were very shallow, the effect of water depth (alone or shared with environmental variables) on chironomid larval community composition was substantially higher than the seasonality (sampling month) effect.

Horizontal and Vertical Distribution of Soil Macroarthropods Along a Spatio-Temporal Moisture Gradient in Subtropical Central Florida

Abstract Distributions of soil macroarthropods were studied monthly for 1 yr (February 2001 to January 2002) in three depth strata (0–8, 8–16, and 16–24 cm) at six sampling sites along a moisture gradient stretching from the shore of Lake Yale, central Florida, to an upland hammock. Annual mean density of total soil macroarthropods at these sites varied from 312 to 1,809 individuals/m2; highest density was recorded near the center of the gradient. The most abundant groups of soil arthropods were Isopoda, predominantly Armadillidium vulgare (Latreille), and Diptera larvae (mostly Limoniidae, Chironomidae and Bibionidae). Species of five genera of Chironomidae (Paraphaenocladius sp., Pseudosmittia sp., Metriocnemus sp., Bryophaenocladius sp., and Smittia sp.) were found. Total number of macroarthropod species at individual sites varied between 40 and 70. The majority (61–92%) of soil macroarthropods from all sites was recovered from the near-surface stratum. Proportion of soil macroarthropods found in the two deeper strata increased with distance from the shoreline, elevation above lake water level, soil carbon content, and acidity of soil. The two sites located near the shoreline were continually flooded from September to January after the lake water level increased by up to 30 cm. Two inland sites were periodically (June–September) flooded by rain water. Flooding at either site caused decreased density of soil macroarthropods, with the effect of lake flooding being more pronounced. Density of soil macroarthropods at flood-affected sites peaked during spring, whereas seasonal changes in density of these invertebrates at most upland sites were less pronounced and peaked in autumn. Results indicated that seasonal migration and recolonization by soil macroarthropods along the moisture gradient are important strategies to overcome flood-affected population losses.

The effect of litter type and macrofauna community on litter decomposition and organic matter accumulation in post-mining sites

Field microcosms consisting of mineral soil (spoil substrate) and two types of litter taken either from an unreclaimed site with spontaneously developed vegetation (mostly Salix caprea) or from an alder plantation (a mixture of Alnus glutinosa and A. incana) were exposed in spontaneously developed or reclaimed sites at a post-mining heap near Sokolov (Czech Republic) for one year. The litter types differed remarkably in C:N ratio which was 29 for spontaneous litter and 14 for alder litter. The two microcosm types were either accessible or not accessible to soil macrofauna. The effect of macrofauna exclusion on soil mixing was complex and depended on litter quality and the site that determined soil fauna composition. In reclaimed sites where macrofauna was dominated by saprophags, mainly earthworms, the macrofauna access increased soil mixing. In sites where predators dominated, the macrofauna exclusion probably suppressed fragmentation and mixing activity of the mesofauna.