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The purpose of this study was to understand the variation in root litter mass‐loss rates in a climatic transect across a large region ranging from the Arctic Circle (66°N) in Scandinavia to Berlin (52°N) in north‐east Germany, dominated by coniferous monocultural forests. To investigate the combined influence of litter quality and climate, data were used from 37 sites and plots at which root litters of three coniferous species (Pinus sylvestris, Pinus contorta and Picea abies) had been incubated. In spite of the considerable climatic differences among sites, there were no strong relationships between any climatic variable and the lst‐yr mass loss (range 17.0–40.9%). For the lst‐yr mass loss, the average annual temperature was the most rate‐regulating factor for all litter combined, with a value for R 2 adj of 0.186. Substrate quality also had an influence. Thus, for the whole region lignin concentration was significant, with a value for R 2 adj of 0.142. For the separated groups of pine and spruce stands ...

Scots pine (Pinus sylvestris) and lodgepole pine (Pinus contorta) needle litters were compared in terms of nutrient composition and its change during decomposition. Initial nutrient composition differed between the species, with lodgepole pine needle litter having significantly higher concentrations of P, Mg and Mn. However, no difference was found for concentrations of N, Ca or K. Increases in concentrations of N, P and K during decomposition were significant in both litter types. For Ca the pattern of concentration changes followed a quadratic function as decomposition proceeded. Concentrations of Mg and Mn decreased in lodgepole pine needle litter. In Scots pine litter there was also an initial decrease, but it was followed by an increase in most incubations. For both Mg and Mn, changes in concentrations during decomposition differed significantly between species. In the late decomposition stages, concentrations of ME and Mn became similar in both litter types. Nutrient concentrations generated by the models were compared with those of the humus (F and H) layer in the stands. The model was quite accurate in predicting concentrations of N and P for both species and the concentration of Mg for lodgepole pine. By contrast, it was not accurate in predicting concentrations of Ca and Mn. Nutrient release was estimated for the two species using both measured litterfall data and long-term estimates, and regression models were used to predict concentration changes. Rates of release of P, Mg and Mn in the lodgepole pine stands were found to be about twice as high compared with those in Scots pine. Calcium was also released to a greater extent although the difference was not significant.

This synthesis paper presents a model for estimating the buildup of soil organic matter in various types of coniferous forests. The knowledge used was obtained from a well‐studied forest with good Iitterfall data, decomposition information and validation measurements of the soil organic matter layer. By constructing a simple model for litterfall, and the information on maximum decomposition levels for litter, we could estimate the annual increase in soil organic matter and extend this to encompass stand age. The validation measurement and the estimated amount of soil organic matter differed by about 8 or 26% over a 120‐yr period, depending on the litterfall model. The estimated increased storage of soil organic matter as a consequence of climate change was found to be drastic. We thus found that the soil organic matter layer would grow about four times as fast as a result of the needle component only. This estimate was based on a comparison between latitudes with a difference of 17°.

We investigated the long‐term net dynamics of N, P, S, K, Ca, Mg and Mn in decomposing litter. Green and brown needles of Scots pine (P. sylvestris L.) lodgepole pine (Pinus contorta), as well as green and brown leaves of white birch (Betula pubescens) and leaves of grey alder (Alnus incana) were incubated for up to 4 years in a 130‐year‐old Scots pine forest. The concentrations of N and S increased linearly with accumulated mass loss, also P concentrations increased linearly after an initial leaching. Moreover, the rate of increase in N concentrations appeared to be proportional to the initial concentration. After the increase, N and P concentrations reached a phase in which they remained constant or declined slightly. Concentrations of Mg and K decreased with accumulated mass loss, especially in litter types with high initial concentrations of these elements. For Mn the pattern was similar but less pronounced. The relationship between Ca concentrations and accumulated mass loss was largely negative, res...

Temporal patterns of changes in nutrient dynamics were followed in decomposing Picea abies needle litter in a long‐term optimum nutrition field experiment using N and P fertilizer. Nutrient‐poor brown and nutrient‐rich green needle litter were incubated in both control plots and fertilized ones. As decomposition proceeded, we could distinguish two groups of nutrients, one for which a clear effect of fertilizer was seen (N, P, Mg) and one for which no clear effect or any clear pattern caused by the fertilizer was seen (K, Ca, Mn). Concentrations of N and P increased and were linearly related to the accumulated mass loss and their dynamics was clearly affected by the fertilizer, viz. the concentrations increased faster in the fertilized plot. Concentrations of Mg decreased linearly in relation to the accumulated mass loss and for the nutrient‐poor brown litter the decrease rate in concentration was lower in the fertilized plot. No effect was seen of the green needle litter. For Ca the concentration increase...

By extrapolation of measured mass‐loss values, maximum values for accumulated litter‐mass loss were estimated by using a nonlinear statistical model. This model predicted that the proportion of mass lost through decomposition should be on the average about 85% for Scots pine needle litter and for lodgepole pine needles the corresponding value was almost 100%. The single incubations of Scots pine and lodgepole pine needle litter were made simultaneously and in parallel plots and could thus be compared pairwise. When thus compared, the limit values (asymptotic values) were significantly different in five cases out of six—the exception being a short measurement series. Lodgepole pine is an introduced species in this system.

The chemical composition of the falling litter was investigated over the different fertilization regimes. The nitrogen concentration in the needle litter increased with dosage of nitrogen fertilizer. Nitrogen concentration in needle litter was positively correlated to those of lignin, sulfur and calcium, but negatively to those of zinc, aluminum, and manganese. Phosphorus concentrations were negatively correlated to those of lignin, manganese, zinc, calcium and magnesium. Concentrations of sulfur were negatively correlated to concentrations of zinc, calcium, aluminum, magnesium and boron. The decomposition patterns of Norway spruce needle litter were followed in an optimum nutrition field experiment. Control plots and plots given high dosages of nitrogen and phosphorus fertilizer were used. As decomposition proceeded soluble substances disappeared quickly and the concentration of soluble substances consequently decreased fast. Lignin, being a recalcitrant compound, increased in concentration and the conce...

The concentration of live fungal biomass (FDA mycelium) was investigated in seven chemically very different litter types, i.e. grey alder leaves, green and brown leaves of white birch, green and brown needles of both Scots pine and lodgepole pine. Concentration of FDA mycelium in the litters changed with the season, being low during the dry late summer and relatively higher during the more rainy, wet autumn. During autumns, when moisture was not limiting, lignin concentration and live fungal biomass were negatively related. It was concluded that the concentration of live fungal biomass in litter decreased linearly as the lignin concentration increased and thus also decreased linearly to decomposition level of the litter.

A comparison was made for chemical composition and mass‐loss rates between needle litters from Scots pine and lodgepole pine during a four‐year period. Initial chemical composition differed. Thus lodgepole pine needle litter had higher concentrations of sulfuric‐acid lignin, phosphorus, magnesium and manganese, whereas Scots pine needles were richer in soluble substances. No difference between species was noted in concentrations of nitrogen, calcium and potassium. In the early stages of decomposition ( 300 days) there was no difference in the decomposition rate. Combining both species, mass‐loss rates were positively correlated to concentrations of water solubles and nitrogen, and negatively correlated to those of lignin. Mass‐loss rate was correlated to phosphorus concentrations only within species. For lodgepole pine needles the early phase of decomposition appeared to be c...

The climatic influence on plant litter decomposition has been successfully correlated on a regional level by using estimated actual evapotranspiration (AET) and annual mass loss. This approach was applied to decomposition studies carried out in a transect along Sweden with litter incubated in four different forest types. A unified needle litter was used and among 14 Scots pine sites about 80% of the mass‐loss rate could be explained. A simple model was made on the influence of both climate and nutrient concentrations (nitrogen and phosphorus) on mass‐loss rate. About 90% of the first‐year mass loss could be explained by this approach. As early decomposition stages were studied (

Decomposition of Scots pine needle litter originating from five stands treated with different amounts of nitrogen fertilizer was measured over a 4‐year period in a mature Scots pine forest. The litter types, which differed in initial concentrations of nitrogen, phosphorus, potassium, and sulfur, but not in gross organic composition, were studied with respect to mass loss, ingrowth of total fungal mycelium, and net release of nutrients. During the first year of decomposition, rates of mass loss and ingrowth of fungal mycelium were highest in the nutrient‐rich litter. Phosphorus concentration was found to be the main factor affecting mass‐loss rate, and the rate of fungal ingrowth was positively correlated with initial nitrogen concentration. After this initial period, decomposition rates decreased, and after 4 years, accumulated mass loss and amounts of fungal mycelium were similar in all five litter types. These findings may be due, in part, to a lower rate of lignin decomposition in nitrogen‐enriched lit...

The chemical fixation of l5N‐ammonia by partly decomposed Scots pine needle litter was studied. The material had been extracted with water using ultra‐sound treatment. This treatment, together with the addition of HgCl2 had killed microorganisms and prevented microbial activity. Fixation of 15N‐ammonia decreased with increasing accumulated mass loss and was inversely proportional to concentrations of sulfuric‐acid lignin as well as to concentrations of total nitrogen.

In northern coniferous forests nutrient release from litter occurs primarily in late stages of decomposition when mainly extensively lignified parts remain. An important regulating factor in these ...

The effect on litter decomposition rates was studied after annual additions for four years to the forest floor of sulfuric acid (64 kg S.ha−1), sulfur powder (64 kg S.ha−1), and in the first year l...