We would like to dedicate this paper to co-author Richard Payne. Richard was a member of a group of 8 climbers caught in an avalanche in the Himalayas at the end of May.
Correspondence
AbstractRecent studies show that soil eukaryotic diversity is immense and dominated by micro-organisms. However, it is unclear to what extent the processes that shape the distribution of diversity in plants and animals also apply to micro-organisms. Major diversification events in multicellular organisms have often been attributed to longterm climatic and geological processes, but the impact of such processes on protist diversity has received much less attention as their distribution has often been H I I I J J J J J J J J J K K K
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We measured phytomass stock and production in Western Siberian mire ecosystems (palsa, ridge, oligotrophic and mesotrophic hollows, fen). To determine the contribution of different phytomass fractions into total production, we developed a method to estimate below-ground production (BNP). Standing crop of living above-ground phytomass on treeless plots varied from 300 to 660 g m -2 , reaching maximum on palsa, where 81% of phytomass consisted of Sphagnum mosses and lichens. In the hollows and the fen, Sphagnum percentage varied from 70 to 95%. Standing crop of living below-ground phytomass varied from 325 to 1,210 g m -2 . It consisted of woody stems, stem bases, rhizomes and roots, with the latter contributing from 30 to 60%. Total production of mire ecosystems in northern taiga of Western Siberia ranged from 350 to 960 g m -2 year -1 and depended on microtopography of the ecosystem (the presence of permafrost and water table depth). Production of treeless plant communities located on the elevated sites depended on the presence of permafrost: in comparison with the ridge, palsa production was lower. Production on the low sites increased with increase pH and reached maximum (960 g m -2 year -1 ) in poor fens. Bryophytes were the major producers above ground. Their production varied from 100 to 272 g m -2 year -1 and reached maximum on ridges. BNP contributed 37-66%, increasing due to increased contribution of sedges.
Abstract. Rain-fed peatlands are dominated by peat mosses (Sphagnum sp.),
which for their growth depend on nutrients, water and CO2 uptake from
the atmosphere. As the isotopic composition of carbon (12,13C) and
oxygen (16,18O) of these Sphagnum mosses are affected by
environmental conditions, Sphagnum tissue accumulated in peat
constitutes a potential long-term archive that can be used for climate
reconstruction. However, there is inadequate understanding of how
isotope values are influenced by environmental conditions, which restricts
their current use as environmental and palaeoenvironmental indicators. Here
we tested (i) to what extent C and O isotopic variation in living tissue of
Sphagnum is species-specific and associated with local hydrological
gradients, climatic gradients (evapotranspiration, temperature,
precipitation) and elevation; (ii) whether the C isotopic signature can be a
proxy for net primary productivity (NPP) of Sphagnum; and (iii) to
what extent Sphagnum tissue δ18O tracks the
δ18O isotope signature of precipitation. In total, we analysed
337 samples from 93 sites across North America and Eurasia using two
important peat-forming Sphagnum species (S. magellanicum,
S. fuscum) common to the Holarctic realm. There were differences in
δ13C values between species. For S. magellanicum
δ13C decreased with increasing height above the water table
(HWT, R2=17 %) and was positively correlated to productivity
(R2=7 %). Together these two variables explained 46 % of the
between-site variation in δ13C values. For S. fuscum,
productivity was the only significant predictor of δ13C but
had low explanatory power (total R2=6 %). For δ18O
values, approximately 90 % of the variation was found between sites.
Globally modelled annual δ18O values in precipitation
explained 69 % of the between-site variation in tissue
δ18O. S. magellanicum showed lower
δ18O enrichment than S. fuscum (−0.83 ‰
lower). Elevation and climatic variables were weak predictors of tissue
δ18O values after controlling for δ18O values
of the precipitation. To summarize, our study provides evidence for (a) good
predictability of tissue δ18O values from modelled annual
δ18O values in precipitation, and (b) the possibility of
relating tissue δ13C values to HWT and NPP, but this appears to
be species-dependent. These results suggest that isotope composition can be
used on a large scale for climatic reconstructions but that such models
should be species-specific.
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