No abstract

No abstract

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.

No abstract

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.