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The chemical properties and biological activities of soils were studied in the vicinity of the medieval settlement Podkumskoe-3 in the Kislovodsk basin (Northern Caucasus, Russia). Between the 5th and 8th centuries this area was ploughed regularly, but it was then abandoned up to the present day. It has been established that past human activity leads to soil undergoing significant transformations in terms of microbial communities and enzyme activity, and that such changes are maintained over long periods. Long-term manuring in the middle of the first millennium AD led to an increase in organic carbon content and the accumulation of nitrate nitrogen. Soils of ancient abandoned fields are associated with increases in microbial biomass, number of saprotrophic bacteria, urease activity, and fungal mycelium biomass. The observed changes in the microbiological and biochemical properties of soil were conditioned by secondary anthropogenically induced succession after the abandonment of arable lands. [ABSTRACT FROM AUTHOR]

The use of biowaste compost as soil organic amendment is of great interest for soil recovery. However, there is little knowledge of detailed effects on chemical, microbial, and biochemical properties in different soil compartments (aggregate classes) following long-term amendment with biowaste compost. We studied the distribution of soil organic carbon (SOC), total nitrogen (TN), soil microbial biomass (SMB), microbial community composition and activity in bulk soils and in three water stable aggregate classes (>250, 250–53, and <53 μm), after seven years of different fertilization treatments: biowaste compost (Com), mineral NPK fertilizers (Min), biowaste compost with half-dose N fertilizer (ComN), and no fertilizers as control (Cnt). Microbial biomass was assessed through a double-stranded DNA (dsDNA) based method and enzyme activities were determined using a microplate-based fluorometric assay. Denaturing gradient electrophoresis (DGGE) fingerprinting analysis was used to study the composition of both fungal and bacterial communities. Com and ComN treatments improved significantly SOC, TN and SMB in bulk soils and in all aggregate sizes. Composition of fungal and bacterial communities shifted with biowaste compost, more in soil aggregates than in bulk soils. To this change of microbial community composition in soil aggregates, corresponded a response of enzymes activities to fertilization treatments depending on aggregate size. Com treatment caused the highest enzyme activity in microaggregates (250–53 μm), whereas ComN and Min showed, in general, a higher activity in silt plus clay sized aggregates (<53 μm). The enzymes involved in biogeochemical cycle of P, with the exception of the phytase, displayed the lowest activity in macroaggregates (>250 μm), suggesting that the intensity of this cycle is lower in this soil niche; however, they increased with C accumulation due to both biowaste compost treatments. Furthermore, fungal diversity and richness decreased with fertilization treatments in all fraction except in macroaggregates. Thus, soil aggregates regulated the feedback of chemical, biochemical and microbial properties in response to soil fertilization strategies. • Compost increases SOC, TN and ds-DNA in bulk soil and in soil aggregates. • Compost affects microbial community more in aggregates than in bulk soil. • Compost has shifted microbial composition and increased enzyme activities. • Enzyme activities respond to fertilization treatments according to aggregate size. [ABSTRACT FROM AUTHOR]

A comparative analysis of the chemical and microbiological properties of palaeosols buried beneath burial mounds (kurgans) of the Bronze Age in the desert steppe zone of Russia provides an opportunity to elucidate the precipitation pattern during cold and warm seasons. Soil salinity in the desert steppes depends on the amount of precipitation during the cold season. Snow melting provides a deep drenching of soil and leaching of toxic salts down the profile. Summer precipitation moistens several upper inches of the soil but does not affect its general chemical properties. At the same time, the state of soil microbial communities is influenced by the spring-summer moisture. The more precipitation there is during the vegetation period, the more phytomass there is, and therefore, more plant residues enter the soil, thereby causing an increase of the microbial biomass that decomposes it. The results of the study of subkurgan palaeosols buried about 4200-3900 yr BP in the desert steppe zone in the southeast of the Russian Plain show an increase of soil salinity with a simultaneous increase in the microbial biomass and number of cells that are decomposing plant residues. The hypothesis of a reduction in winter precipitations and an increase in precipitation during the warm season is assumed. These findings explain a bloom of archaeological Middle Bronze Catacomb culture in the desert steppes. The lack of snow and increased precipitation during the vegetation season affected the productivity of phytocenoses and prevented spring burns of vegetation, which provided more favourable conditions for the early cattle breeders of the catacomb Bronze Age population. [ABSTRACT FROM AUTHOR]

The interrelation of Alpine topography with the micro − and mesobiota is still poorly understood. We investigated the effects of ground cover type and slope exposure on the soil microbial biomass (double-stranded DNA, ds DNA) and abundances (real time PCR, qPCR); hydrolytic enzyme activities; and enchytraeid community structure in top soils (2.5-cm increments depth) in subalpine forests in the Italian Alps. Dominant ground covers were grass, moss, litter and woody debris at the north- and the south-facing slopes. The autochthonous soil microbiota (bacteria, fungi and archaea) was quantified by qPCR in the extracellular (eDNA) and intracellular fraction (iDNA) of the total soil DNA pool. A higher eDNA/iDNA ratio indicative of lower microbial activity was recorded in the deepest layer of the grass plots at the north-facing slope. This can be related to a lower degradation of eDNA and/or to an accumulation of eDNA with increasing depth as a result of leaching. The exposure effect was enzyme-specific and higher activities occurred under woody debris primarily at the south-facing slope. These plots also showed a higher nutrient content and a greater microbial biomass assessed as ds DNA yields. Total microannelid abundance was elevated on north-facing slopes on account of strong acidity indicator species. This was related to soil pH being one unit lower compared to the south-facing slope. The thickness of the organic layer (OL + OF + OH) was elevated at the north-facing slope due to a considerably thicker OH-horizon. The vast majority of microannelids at this slope occurred in the organic layer, while at south exposure they were almost evenly distributed between the organic layer and the mineral soil (A-horizon). Exposure was found to be more determinative for the composition of microannelid assemblages than the ground cover type. [ABSTRACT FROM AUTHOR]

Due to their sensitivity to changing environmental conditions sub- and alpine soils are often monitored in the context of climate change, usually, however, neglecting slope exposure. Therefore, we set up a climosequence-approach to study the effect of exposure and, in general, climate, on the microbial biomass and microbial diversity and activity, comprising five pairs of north (N)- and south (S)-facing sites along an altitudinal gradient ranging from 1200 to 2400 m a.s.l. in the Italian Alps (Trentino Alto Adige, Italy). Soil physico-chemical properties were related to microbiological properties (microbial biomass: double strand DNA yield vs. substrate-induced respiration; diversity of bacterial, fungal and archaeal communities: genetic fingerprinting DGGE vs. real-time PCR; microbial activity: basal respiration vs. multiple hydrolytic enzyme assays) to monitor shifts in the diversity and activity of microbial communities as a function of slope exposure and to evaluate the most determinant chemical parameters shaping the soil microbiota. The exposure-effect on several hydrolytic key-enzymes was enzyme-specific: e.g. acid phosphomonoesterase potential activity was more pronounced at the N-facing slope while the activities of alkaline phosphomonoesterase, pyrophosphate-phosphodiesterase and arylsulfatase were higher at the S-facing slope. Furthermore, this exposure-effect was domain-specific: bacteria (S > N, altitude-independent); fungi (N ~ S); and archaea (N > S; altitude-dependent). Additionally, the abiotic parameters shaping the community composition were in general depending on soil depth. Our multidisciplinary approach allowed us to survey the exposure and altitudinal effects on soil physico-chemical and microbiological properties and thus unravel the complex multiple edaphic factor-effects on soil microbiota in mountain ecosystems. [ABSTRACT FROM AUTHOR]

Storage of woody biomass in large wood chip piles is unavoidable for biotechnological applications, but comes along with considerable biomass-, energy- and thus, economic losses due to exothermic reactions and microbial degradation. The homogeneous amendment of the storage piles with an alkaline stabilization agent, calcium hydroxide (Ca(OH) 2), was found to decrease dry matter loss in Picea abies; for Populus canadensis piles the effects cannot clearly be deduced. Here we investigated the bacterial and fungal communities of industrial-scale wood chip piles (250 m3) of these two different tree species and related them to physicochemical conditions and enzymatic activities after 35 and 120 d, representing short- and long-term storage of the wood chips, respectively. Coming from different wood types (hard vs. softwood), we expected the communities to converge over time, due to similar storage conditions. Despite pH posing selective pressure, we expected a minor Ca(OH) 2 effect as already known from previous studies. We found that the effectiveness of Ca(OH) 2 addition depended on the wood type that determined both the native microbial seeding community and temperature pattern of all piles, thereby exerting selective forces of differing strength. Generally, a thermophilic community consisting of single fungal and variable bacterial taxa were identified. As expected, the microbial communities from P. abies and P. canadensis converged over time. Biomass loss was connected to C-cycle related enzymatic activities and to the abundance and composition of fungal communities. Chaetomium sp. was identified as potential key taxon determining biomass degradation under the given storage conditions. [Display omitted] • Wood type determines native seeding microbiota for thermophilic storing conditions. • Microbiota from different wood types converge during storage in outdoor piles. • Single thermophilic fungi gain importance. • Ca(OH) 2 addition counteracts dry matter loss in Picea abies. [ABSTRACT FROM AUTHOR]