Contributions of a global network of tree diversity experiments to sustainable forest plantations

status: publishe

Belowground Biodiversity Relates Positively to Ecosystem Services of European Forests

Environmental Biolog

Nitrosomonas europaea-like bacteria detected as the dominant b-subclass Proteobacteria ammonia oxidisers in reference and limed acid forest soils

Net nitrification in intact soil cores and the community of ammonia-oxidising bacteria were studied in acid Norway spruce (Picea abies (L.) Karst) and sessile oak (Quercus petraea (Matt. Lieb.)) soils (Haute Ardenne, east Belgium) 18 months after treatment with 5tha1 dolomite lime. Liming caused a significant increase in nitrification in the upper soil layers (0.15m) of both stands. DGGE (denaturing gradient gel electrophoresis) profiling after -subclass ammonia oxidiser-specific polymerase chain reaction (PCR), combined with hybridisation and sequencing of excised DGGE bands revealed a dominance of Nitrosomonas europaea-like sequences, independent of soil horizon, tree species and lime treatment. A minority Nitrosospira-like population was detected, which showed affinity to nitrosospiras previously detected in acid soil. These results contrast with several reports suggesting a dominance of Nitrosospira-like organisms among ammonia oxidiser communities in acid soils. [KEYWORDS: 16S rDNA; DGGE; Picea abies; Quercus petraea; Nitrification; Dolomite lime]

Comparaison des peuplements de diatomées épilithiques de ruisseaux acides en milieu forestier soumis à un amendement de dolomie (Massif Ardennais, Belgique)

Trois à cinq ans après un amendement de dolomie (carbonate calco-magnésien) réalisé en Belgique sur certains bassins versants forestiers du massif ardennais, les diatomées épilithiques ont été prélevées dans deux ruisseaux situés en zone amendée et dans deux ruisseaux en zone non amendée afin de déceler les éventuels changements induits dans les peuplements algaux. On observe des assemblages à Eunotia typiques des eaux acides. L'espèce dominante est Eunotia exigua, souvent accompagnée par E. rhomboidea ou E. bilunaris. Dans le cadre de cette étude, aucune influence propre à l'amendement n'a pu être mise en évidence par l'étude de ces bioindicateurs

Elevated atmospheric CO2 in open top chambers increases net nitrification and potential denitrification

The control of soil nitrogen (N) availability under elevated atmospheric CO2 is central to predicting changes in ecosystem carbon (C) storage and primary productivity. The effects of elevated CO2 on belowground processes have so far attracted limited research and they are assumed to be controlled by indirect effects through changes in plant physiology and chemistry. In this study, we investigated the effects of a 4-year exposure to elevated CO2 (ambient + 400 mumol mol(-1) ) in open top chambers under Scots pine (Pinus sylvestris L) seedlings on soil microbial processes of nitrification and denitrification. Potential denitrification (DP) and potential N-2 O emissions were significantly higher in soils from the elevated CO2 treatment, probably regulated indirectly by the changes in soil conditions (increased pH, C availability and NO3 (-) production). Net N mineralization was mainly accounted for by nitrate production. Nitrate production was significantly larger for soil from the elevated CO2 treatment in the field when incubated in the laboratory under elevated CO2 (increase of 100%), but there was no effect when incubated under ambient CO2 . Net nitrate production of the soil originating from the ambient CO2 treatment in the field was not influenced by laboratory incubation conditions. These results indicate that a direct effect of elevated atmospheric CO2 on soil microbial processes might take place. We hypothesize that physiological adaptation or selection of nitrifiers could occur under elevated CO2 through higher soil CO2 concentrations. Alternatively, lower microbial NH4 assimilation under elevated CO2 might explain the higher net nitrification. We conclude that elevated atmospheric CO2 has a major direct effect on the soil microbial processes of nitrification and denitrification despite generally higher soil CO2 concentrations compared to atmospheric concentrations