We studied the effects of applying different composts (urban organic waste, green waste, manure and sewage sludge), mineral fertilizer and compost plus mineral fertilizer on chemical, biological and soil microbiological parameters over a 12-year period. The organic C and total N levels in soils were increased by all compost and compost + N treatments. Microbial biomass C was significantly (P £ 0.05) increased for some compost treatments. In addition, basal respiration and the metabolic quotient (qCO 2 ) were significantly higher in all soils that had received sewage sludge compost. The Shannon diversity index (H), based on community level physiological profiling, showed a higher consumption of carbon sources in soils treated with compost and compost + N compared with the control. The utilization of different guilds of carbon sources varied amongst the treatments (compost, compost + N or mineral fertilizer). Cluster analysis of polymerase chain reaction-denaturing gradient gel electrophoresis patterns showed two major clusters, the first containing the mineral fertilization and compost treatments, and the second, the composts + N treatments. No differences in bacterial community structure could be determined between the different types of compost. However, the results suggest that long-term compost treatments do have effects on the soil biota. The results indicate that the effects on the qCO 2 may be due to shifts in community composition. In this study, it was not possible to distinguish with certainty between the effects of different composts except for compost derived from sewage sludge.

We followed the changes in the protist assemblage over an annual cycle at 3 sites and different depths of Traunsee in the Austrian Alps and quantified the variability of the ciliate assemblage along successive depth and time intervals, respectively. More than 60 ciliate species were identified alive and after quantitative protargol staining (QPS). The ciliate diversity was high, and is described in detail for 50 taxa in time-depth intervals. Rimostrombidium brachykinetum/Rimostrombidium hyalinum and Balanion planctonicum were the most frequent species, accounting for 44% of the annual mean abundance and 15% of the annual mean biovolume, respectively. Our results suggested a stronger variability in the ciliate assemblage structure within seasons than along the depth gradient. Gradual changes in the assemblage structure with depths: (1) were accompanied by a decrease of algivorous and mixotrophic and an increase of bacterivorous ciliates from surface to deeper layers; (2) were highly significantly altered with steep depth gradients of their potential food resources, i.e. the biomass of heterotrophic flagellates, bacteria and algae; and (3) were related with lower significance to environmental parameters. High similarity (> 80%) between successive months was reached only when net changes in the total ciliate abundance were negligible, while a strong increase or decrease in the ciliate abundance was associated with pronounced changes in the species composition. These seasonal changes in the ciliate assemblage structure (4) were linked to shifts of algivorous and mixotrophic, but not of bacterivorous ciliates and (5) were less predictable with food resources compared to the depth gradient. The phagotrophic flagellates generally followed the seasonal and vertical patterns described for ciliates, and were shown to be important members of the planktonic food web in a cold, deep, oligotrophic lake.

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Metabolic abilities and micrfiobial community structure were investigated through three semiarid Mediterranean soils of SE Spain. The soils were (1) a Typic Calcixerept under an adult pine plantation (PP), growing on abandoned agricultural terraces; (2) a Typic Calcixeroll under a native pinewood (NP); and (3) a Typic Haploxerept covered with a grass steppe (GS). PP and NP were similar as regards their genesis, but the former used to be tilled. NP and GS were undisturbed and supported natural and seminatural vegetation, respectively. Seven samples in 10-cm depth increments were taken in triplicate along each soil profile. Community-level physiological profiles based on sole-C-source use were determined to characterize the metabolic abilities. A 16S rDNA polymerase chain reaction-denaturing gradient gel electrophoresis analysis was performed to investigate the microbial genetic structure. Plant cover and land-use history were major determinants of microbial community structure. Microbial communities residing in soils under a native pinewood, the most diverse and stable plant cover, were the most complex both metabolically and genetically. The microbial community structure distinctly changed with depth, related to the quantity and quality of total organic carbon. Both undisturbed soils showed falling gradients of metabolic and genetic complexity, which were invariably of a greater magnitude in the mature woodland than in the grass steppe. In the planted pinewood, however, the substrate-use diversity increased with depth, apparently a response to the depleted metabolic abilities within its upper layer (0-30 cm). Tilling and plant cover removal might be responsible for such a perturbation. In the same profile, molecular fingerprint patterns of the topsoil layer (0-10 cm) indicated a disturbed genetic structure that might underlie the loss of metabolic abilities. However, the genetic structure of the deeper layers of the planted and native pinewoods was not dissimilar, revealing that equivalent genetic resources perform different environmental functions under changing soil scenarios.

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During composting, the degradation of organic waste is accompanied and driven by a succession of microbial populations exhibiting a broad range of functional capabilities. Detailed inventories of the microbial communities in mature compost, however, are not available. Mature composts, originating from biowaste as well as sewage sludge and anaerobic sludge, were studied by denaturing gradient gel electrophoresis-fingerprints after polymerase chain reaction (PCR) amplification of the 16S rRNA genes using three different universal primer pairs, as well as by differential scanning calorimetry and thermogravimetry. The composts of different origin had different bacterial communities. The influence of different 16S rDNA primer sets on the same batches of compost DNA was evaluated. The clearest separation of different compost types was obtained by using the PCR primer pair 338f + 518r which is suggested for future applications. Communities from the different biowaste compost samples clustered together and could be separated from sewage sludge communities indicating the establishment of different microbial consortia. A similar differentiation of composts was found with the thermogavimetric analyses. It may thus be concluded that the resulting humus quality is closely linked to the microbial communities involved.

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