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Peat bogs have accumulated more atmospheric carbon (C) than any other terrestrial ecosystem today. Most of this C is associated with peat moss ( Sphagnum) litter. Atmospheric nitrogen (N) deposition can decrease Sphagnum production, compromising the C sequestration capacity of peat bogs. The mechanisms underlying the reduced production are uncertain, necessitating multifactorial experiments., We investigated whether glasshouse experiments are reliable proxies for field experiments for assessing interactions between N deposition and environment as controls on Sphagnum N concentration and production. We performed a meta-analysis over 115 glasshouse experiments and 107 field experiments., We found that glasshouse and field experiments gave similar qualitative and quantitative estimates of changes in Sphagnum N concentration in response to N application. However, glasshouse-based estimates of changes in production - even qualitative assessments - diverged from field experiments owing to a stronger N effect on production response in absence of vascular plants in the glasshouse, and a weaker N effect on production response in presence of vascular plants compared to field experiments., Thus, although we need glasshouse experiments to study how interacting environmental factors affect the response of Sphagnum to increased N deposition, we need field experiments to properly quantify these effects. [ABSTRACT FROM AUTHOR]

Net primary production (NPP) of the forest moss Hylocomium splendensincreased significantly along an elevational gradient in the southern Alps of Italy. Extracellularly bound metals (Al, Ca, Co, Cr, Fe, Ni, Mo, Ni, Pb) showed declining concentrations in moss tissue with increasing altitude, presumably because the amount of exchange sites on the cell wall increases less than total biomass. Concentrations of intracellular elements did not vary (Cd, Cu, Mg, Na, Zn), or even increased (K) with altitude. The observed patterns were always independentof precipitation amount and soil concentrations of exchangeable elements. A higher soil nutrient status only enhanced K uptake by the moss. We concluded that variations in moss NPP, associated with elevational gradients, may significantly affect estimates of atmospheric deposition based on moss analysis in mountainous regions. [ABSTRACT FROM AUTHOR]

A survey of heavy metal deposition in the mountainous territories ofNorthern Italy was carried out in 1995-96. Moss samples (mainly Hylocomium splendens) were collected in a dense network of sites (about 3.2 sites/1000 km2) and the data of metal concentrations inmoss tissues were statistically correlated with environmental and climatic factors, as well as with bulk deposition of elements and elemental concentrations in the soil. Three main geographic patterns of metal concentration in mosses could be defined: (1) Fe, Ni, and Cr, allderived both by soil particulates and anthropogenic emissions connected with ferrous metal manufacturing, were mostly concentrated in Northwestern Italy; (2) Cu and Zn, as typical multi-source elements, showed rather high concentrations with little ranges of variation over the whole area and small peaks reflecting local source points; (3) Cd and Pb reflected long-distance transport and showed highest concentrations in the regions with highest precipitation, especially in the Eastern Alps. [ABSTRACT FROM AUTHOR]

Abstract: In peatlands the reduced decomposition rate of plant litter is the fundamental mechanism making these peat-accumulating ecosystems effective carbon sinks. A better knowledge of litter decomposition and nutrient cycling is thus crucial to improve our predictions of the effects of anthropogenic perturbation on the capacity of peatlands to continue to behave as carbon sinks. We investigated patterns of plant litter decomposition and nutrient release along a minerotrophic–ombrotrophic gradient in a bog on the south-eastern Alps of Italy. We determined mass loss as well as P, N, K, and C release of seven vascular plant species and four moss species after 1 year in both native and transplanted habitats. Hence, differences in litter decay were supposed to reflect the degree of adaptability of microbial communities to litter quality. Polyphenols/nutrient and C/nutrient quotients appeared as the main parameters accounting for decomposition rates of Sphagnum litter. In particular, litter of minerotrophic Sphagnum species decomposed always faster than litter of ombrotrophic Sphagnum species, both in native and transplanted habitats. Decomposition rates of vascular plant litter in native habitats were always higher than the corresponding mass loss rates of Sphagnum litter. Minerotrophic forbs showed the fastest decomposition both in native and transplanted habitats in accordance with low C/P and C/N litter quotients. On the other hand, C/P quotient seems to play a primary role also in controlling decomposition of graminoids. Decomposition of deciduous and evergreen shrubs was negatively related to their high lignin content. Nitrogen release from Sphagnum litter was primarily controlled by C/N quotient, so that minerotrophic Sphagnum litter released more N than ombrotrophic Sphagnum litter. Overall, we observed slower N release from litter of ombrotrophic vascular plant species compared to minerotrophic vascular plant species. No single chemical parameter could predict the variability associated with different functional groups. The release of K was very high compared to all the other nutrients and rather similar between ombrotrophic and minerotrophic litter types. In Sphagnum litter, a higher C/P quotient was associated with a slower P mineralisation, whereas a faster P release from vascular plant litter seems primarily associated with lower C/P and polyphenols/P quotients. [Copyright &y& Elsevier]