Decomposition of European beech and Black pine foliar litter along an Alpine elevation gradient: Mass loss and molecular characteristics

Litter decomposition is an important process in global carbon (C) and nutrient cycles. The objective of this study was to evaluate the role of climate on litter decomposition along an altitudinal gradient in a temperate Alpine region, and to characterize the decompositional stages of the litter material with Fourier-transform mid-infrared spectroscopy (FT-MIR). Foliar litter of European beech (Fagus sylvatica) and Black pine (Pinus nigra) was incubated in litterbags during two years in the Hochschwab massif of the Northern Limestone Alps of Austria. Six incubation sites were selected following an altitudinal/climatic transect from 1900 to 900meters above sea level (masl), with soil properties (carbon:nitrogen—C:N ratios and pH) being strongly influenced by vegetation. The results indicated that the climatic gradient played only a secondary role for decomposition rates. First year mass loss of both litter types was positively related to soil C:N ratio, which was the major explanatory variable in multiple regression analysis. For second year mass loss, soil pH appeared to be a determinant factor, while altitude was the least related parameter. The FT-MIR spectra of the remaining litter did not follow typical patterns of decomposing organic matter (OM) in forest litter horizons. A strong increase of most band areas—particularly those at 1515, 1420, 1270, and 1230cm−1—suggested the accumulation of lignin in the remaining litter. We conclude that the effect of climate on litter mass loss can be offset by differences in soil parameters, possibly through related soil microbial populations. ► soil C:N ratio exhibited the strongest correlation with litter mass loss ► the climatic gradient played only a secondary role for decomposition rates ► FT-MIR spectra suggested accumulation of lignin in the remaining litter