Litter layers decomposition

The process of forest litter decomposition is one of the key processes leading to the redistribution of Cs among the ecosystem components. It is affected by two major factors the rate of decomposition, which is dependent on the composition of the litter and the time since the introduction of Cs, which determines the level of decomposition of the uppermost, most heavily contaminated layer. The distribution of i Cs between the separate litter layers is important, since Of and Oh are critical for the roots of many undergrowth plant species (such as V. myrtillus, V. vitis-idaea, V. uUginosu and L. palustre ) and fungal saprotrophs (Clitocybe,... 

The decomposition of tree leaves is not entirely confined to the litter layer on the forest floor. Leaves and needles are invaded by bacteria and fungi even as they grow these microorganisms may be either pathogens or saprophytes. ... 

Figure 14.10. Principal component analysis of Py-FI mass spectra of (a) cold and (b) hot water extracts from the sequence of organic litter layers Oi-Oe-Oa in a beech stand (Fagus sylvat-ica) obtained before (-pre) and after (-post) aerobic incubation. The arrows indicate changes due to progressive decomposition top-down in the litter profile. Reprinted from Landgraf, D., Leinweber, P, and Makeschin, F. (2006). Cold and hot water extractable organic matter as indicators of litter decomposition in forest soils. Journal of Plant Nutrition and Soil Science 169,76-82, with permission of Wiley-VCH.

Figure 12 Decomposition dynamics of Spruce needles as indicated by increasing depth in the litter layers (S, L, FI, F2, and Fb). Fb = F layer that has been invaded by white-rot fungi (after Gourbiere, 1982).

Production of roots on top of the mineral soil has been explained as a consequence of the low nutrient availability in Amazon forests (Herrera et al. 1978, Cuevas and Medina 1983, Medina and Cuevas 1989). Vertical root distribution results from differential nutrient availability in the soil profile (Berish 1982, Berish and Ewel 1988). Shallow rooted systems may be a result of litter and soil organic matter production and decomposition rates in systems where nutrient input from litter exceeds that of nutrient release by soil weathering, as is the case of Ca, Mg, and P in terra firme forests (Medina and Cuevas 1989). In the Middle Caqueta region of Colombia, for example, Ca and Mg concentrations in the L and F layers are between 15 and 20 times higher than in the mineral soil (Duivenvoorden and Lips 1995). 

Soil stratification. The layers of a typical soil, which make up a soil profile, are illustrated in a general way in Figure 1.18. It is clear that the upper layers of the profile are enriched in organic matter in various stages of decomposition. The topmost horizon, 01, consists of relatively unaltered organic litter in the 02 horizon,... 

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