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We have synthesized available data for calcium (Ca) dynamics in decomposing foliar litter of mainly pine (Pinus), spruce (Picea), and birch (Betula) species to determine patterns of Ca concentration with climate in newly shed litter and its dynamics in decomposing litter as well as a possible role for Ca as regards limit values. Initial Ca concentration was negatively related to mean annual precipitation (MAP) with different relationships among genera. A limited data set showed a positive relationship across species (p In decomposing litter, Ca concentration followed a negative quadratic (Ca = a + t − t2) function and had a maximum, which was variable. The Ca maximum concentration during decomposition was positively related to initial Ca concentration both within and among species. Separate linear relationships based on species were combined into one, in common for all investigated species and genera (R2 = 0.914, n = 63, p Limit values for decomposition were positively related to maximum Ca concentration at p Calcium net release started directly after the incubation and was linear to accumulated mass loss of litter, giving a slope coefficient for each study. The net release rates were linear to initial Ca concentration both within and across species/genera. All studies combined gave a negative linear relationship (R2 = 0.894, n = 67, p

The aim of this paper is to evaluate relationships between decomposition rates of Scots pine (Pinus sylvestris) and lodgepole pine (Pinus contorta var. contorta) needle litter in the late stage of ...

We have reviewed the literature on the role of manganese (Mn) in the litter fall-to-humus subsystem. Available data gives a focus on North European coniferous forests. Manganese concentrations in p ...

Nitrogen (N) and phosphorus (P) and N:P ratio in terrestrial plants and the patterns at a large geographical scale are an important issue in ecological stoichiometry. In particular, it is essential to know that for a single species, how the N:P stoichiometry varies with climatic factors in the context of global warming. Our analysis was based on a data set including 2583 observations at 441 sites on nutritional status of Norway spruce ( Picea abies L.) located in European counties (including Austria, Belgium, Bulgaria, Czech Rep., Finland, Germany, Ireland, Italy, Lithuania, Norway, Slovak Rep., Slovenia, United Kingdom). Our objectives are to demonstrate how leaf N and P concentration and N:P ratio in Norway spruce vary with altitude (ALT), latitude (LAT), longitude (LON), mean annual temperature (MAT) and mean annual precipitation (MAP) across Europe. The results showed that for 1-year-old needles of Norway spruce, the N and P concentration were 13.28 mg g −1 , 1.41 mg g −1 and the N:P ratio was 9.76. Leaf N displayed a convex curve pattern with increasing MAT and decreasing LAT from the boreal Europe to the Mediterranean area. The N concentration and N:P generally reached peak at about 7 °C in MAT or 53° N in LAT. The N:P ratio varied non-linearly with LAT and MAP, but linearly with MAT. Leaf N concentration and N:P ratio decreased linearly with increasing ALT in temperate European area. Across Europe, that the patterns of leaf N and N:P ratio were mainly driven by climate-related geochemistry and plant physiology, but also greatly impacted by anthropogenic N deposition.

Information on soil carbon sequestration and its interaction with nitrogen availability is rather limited, since soil processes account for the most significant unknowns in the C and N cycles. In this paper we compare three completely different approaches to calculate carbon sequestration in forest soils. The first approach is the limit-value concept, in which the soil carbon accumulation is estimated by multiplying the annual litter fall with the recalcitrant fraction of the decomposing plant litter, which depends on the nitrogen and calcium content in the litter. The second approach is the N-balance method, where carbon sequestration is calculated from the nitrogen retention in the soil multiplied with the present soil C/N ratio in organic layer and mineral topsoil. The third approach is the dynamic SMART2 model in combination with an empirical approach to assess litter fall inputs. The comparison is done by first validating the methods at three chronosequences with measured C pools, two in Denmark and one in Sweden, and then application on 192 intensive monitoring plots located in the Northern and Western part of Europe. Considering all three chronosequences, the N-balance method was generally most in accordance with the C pool measurements, although the SMART2 model was also quite consistent with the measurements at two chronosequences. The limit-value approach generally overestimated the soil carbon sequestration. At the intensive monitoring plots, the limit-value concept calculated the highest carbon sequestration, ranging from 160 to 978 kg ha−1 year−1, followed by the N-balance method which ranged from 0 to 535 kg ha−1 year−1. With SMART2 we calculated the lowest carbon sequestration from −30 to 254 kg ha−1 year−1. All the three approaches found lower carbon sequestration at a latitude from 60 to 70° compared to latitudes from 40 to 50 and from 50 to 60. Considering the validation of the three approaches, the range in results from both the N-balance method and SMART2 model seems most appropriate.

The decomposition rate of fresh plant litter may decrease from ca. 0.1% per day in fresh litter to 0.00001 per day or lower in more completely decomposed material. This is due to changes in its organic-matter quality as the recalcitrant chemical components become enriched in the material. The decrease in decomposability (substrate quality) is complex, involving both direct chemical changes in the substrate itself and the succession in micro-organisms able to compete for the substrate with a given chemical composition. The concept ‘substrate quality’ varies among litter species, though. In fresh litter, there may be a lack of macronutrients, such as N, P, and S thus limiting the decomposition rates of, for example, the celluloses, and the rates may be positively related to, for example, the concentration of N. With the disappearance of celluloses, the concentration of the more recalcitrant compound, lignin, increases and the effects of N concentration on decomposition rates change completely. In partly decomposed litter the degradation rate of lignin determines the decomposition rate of the whole piece of litter, which now in reality is turning into soil organic matter (SOM). At this stage high N concentrations will have a rate-retarding effect on lignin degradation and thus on the litter. It appears that this total retarding effect of N may be ascribed to two different mechanisms. First, low-molecular N reacts with lignin remains creating more recalcitrant aromatic compounds, and, further, low-molecular N may repress the synthesis of lignin-degrading enzymes in white-rot fungi. The retardation of the decomposition rate may be so strong that the decomposition of the litter can be estimated to reach a limit value for total mass loss. At such a stage the litter would be close to more stabilized SOM. The limit values estimated to date range from about 45 to 100% decomposition indicating that between 0 and 55% of the litter mass should either stabilize or decompose extremely slowly. We found that N concentration had an overall effect on this limit value in no less than 130 cases investigated, meaning that the higher the N concentration in the fresh litter (the lower the C/N ratio) the more organic matter was left. The relationship could be described by a highly significant and negative linear relation. Other nutrients were also correlated to the limit value. Thus, Mn and Ca had a generally opposite effect to N, meaning that high concentrations of these nutrients were correlated to further decomposition in all studies investigated. The ‘limit-value’ concept may mean that at higher initial N concentrations, the stage with either stabilized SOM or a very low decomposition rate was reached earlier, i.e. at a lower mass loss. Such an effect would mean that in stands with N-rich litter there may be a faster humus accumulation.

The influence of experimental acidification (diluted H 2 SO 4 ) on mass-loss rates of needle and root litters was investigated in forests of Scots pine, lodgepole pine, Norway spruce and white birch located in a climatic transect through Sweden. Of the two dosages given (32 and 96 kg S ha −1 ), significant effects on mass-loss rates were observed mainly with the higher dose. When comparing the effect of acid on mass-loss rate of needle litter on all sites together for the whole 3-year period, no effect was seen. By distinguishing the different types of forest and understorey we found a significant general decrease in rate for needle litter of about 8% for the pine forest sites ( n = 10). For the spruce sites ( n = 8) and the birch sites ( n = 2) no significant effects were seen. When considering single sites after 1 year of decomposition, significant effects (rate decrease) were also found for the birch forests. At some spruce sites significant differences in mass-loss rate were seen (both rate increase and rate decrease). When a significant effect was seen its magnitude was found to be dependent on the decomposition rate (soil biological activity) of that site. For root litter the results were less clear. No significance was seen when comparing all sites together or sites of one type of forest. Significant decreases in mass-loss rate after acid treatment were, however, noted for some of the sites after different incubation periods. The patterns of dynamics of the nutrients N, P, S, K and Ca were not affected whereas those of Mg and Mn were and significantly higher release rates were found for these nutrients after acid treatment. The release rates of the nutrients N, P, S, K and Ca from litter were proportional to litter mass-loss and for the Scots pine stands this meant a decreased release rate for these nutrients.