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The objective of this work was to evaluate the C and N stocks and organic-C fractions in soil under mixed forest stands of Scots pine (Pinus sylvestris L.) and Sessile oak (Quercus petraea [Matt.] Liebl.) of different ages in NE Germany. Treatments consisted of pure pine (age 102 y), and pine (age 90-102 y) mixed with 10-, 35-, 106-, and 124-y-old oak trees. After sampling O layers, soils in the mineral layer were taken at two different depths (0-10 and 10-20 cm). Oak admixture did not affect total organic-C (TOC) and N stocks considering the different layers separately. However, when the sum of TOC stocks in the organic and mineral layers was considered, TOC stocks decreased with increasing in oak age (r 2 = 0.58, p < 0.10). The microbial C (C MB ) was not directly correlated with increase of oak age, however, it was positively related with presence of oak species. There was an increase in the percentage of the C MB -to-TOC ratio with increase of oak-tree ages. On average, light-fraction C (C LF ) comprised 68% of the soil TOC in upper layer corresponding to the highest C pool in the upper layer. C LF and heavy-fraction C (C HF ) were not directly affected by the admixture of oak trees in both layers. The C HF accounted on average for 30% and 59% of the TOC at 0-10 and 10-20 cm depths, respectively. Despite low clay contents in the studied soils, the differences in the DCB-extractable Fe and Al affected the concentrations of the C HF and TOC in the 10-20 cm layers (p < 0.05). Admixture of oak in pine stands contributed to reduce topsoil C stocks, probably due to higher soil organic matter turnover promoted by higher quality of oak litter.

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The objectives of the work were to study phosphorus (P) dynamics in postmining soils under short rotation coppices at different stages of Robinia pseudoacacia L. growth (2, 3, 4, and 14 years old). From the results obtained, the amount of total P, total organic P, plant available P, and P stock increased with increasing age of R. pseudoacacia. However, values were very low compared to that recommended for optimum plant growth, reflecting a general deficit in P. Additionally, the P sorption and desorption processes were investigated. The total P sorption capacity obtained from the laboratory experiments was on average, 2.5 times greater for soils under the oldest R. pseudoacacia than values measured at the younger sites. Values of P saturation factor ( ) were comparatively lower compared to that reported in the literature. This may be attributed primarily to the less P saturation of the postmining soils, coupled with rather small contents of oxalate iron (Fe ox ) and aluminium (Al ox ) (sum of 47 mmol kg −1 ). Results demonstrate significant difference between 2 and 14 years old R. pseudoacacia; thus establishing of short rotation coppice (SRC) on degraded marginal sites may be a valuable method of soil reclamations.

Differences in soil P among silvopasture, grassland, and arable lands have been well established. Nevertheless, most of the reports compare soil properties under long‐term sites. Thus, there exists little information on the effect of the conversion of silvopasture to arable or grassland use on soil P pools. The objective of the study was to determine the impact of converting silvopasture system (SP) into arable cropping and grassland system on the distribution of P pools and potential P bioavailability. We compared the following systems: SP system, SP converted to arable cropland (SP‐AL), SP converted to grassland (SP‐GL), and for comparative purposes, a long‐term arable cropland (AL). The P fractionation was performed by a sequential extraction scheme, using acid and alkaline extractants on samples collected from the 0–10 and 10–20 cm soil layers. It was assumed that the large variations in soil‐P fractionations are caused by the different management practices associated with land conversion. The results of P fractionation showed a dominance of calcium‐bound P, HCl‐extractable Pi constituted up to 36% of the soil total P (TP). However, the type of land use did not affect this P fraction. On the other hand, the reduction in labile‐Pi and NaOH‐Pi fractions observed at the SP‐AL site may have led to the decline in readily available P. The soil total organic P (TPo) content was 8% and 17% lower at SP‐AL compared to SP and SP‐GL site, respectively. Labile organic‐P (labile‐Po) content was markedly higher at SP site compared to arable soils, and was ≈ 10% of TPo. The NaOH‐Po constituted the highest fraction of the organic‐P pool (55%–79% of TPo) across all the study systems, and was positively correlated with TPo (p < 0.01). The study indicates that conversion of SP system in temperate regions to arable cropping with conventional tillage seems to result in the reduction of P availability compared to SP, indicating SP as an important land‐use practice.