Scots Pine Ecosystems Research Articles

Changes in top soil properties of forest soils in north-eastern Germany due to long-term element accumulation

Three Scots pine (Pinus sylvestris L.) ecosystems (Rosa, Taura, and Neuglobsow) along a former deposition gradient (sulfur and alkaline dust) in the new federal states of Germany were investigated since 1993. Although deposition rates were drastically decreased after the unification of Germany, element output rates from formerly impacted sites are still high. Both field measurements and laboratory studies show that the organic surface layers release high amounts of sulfur clearly exceeding present input rates. Therefore, accumulated element stores and top soil properties were analyzed. Amounts of water soluble sulfate and dissolved organic sulfur as determined in batch experiments reflect the former deposition gradient and a specific spatial accumulation pattern within the stands. pH, base saturation and C:N ratio in the top soil are clearly influenced by the former pattern of alkaline dust and sulfur deposition. Undisturbed soil columns from the top soils were taken from all sites to investigate element output rates under controlled conditions and at different temperatures. At 5 °C, both calcium and sulfate output decreases in the order Rosa (1.27 mmol m−2 d−1; 0.25 mmol m−2 d−1) > Taura (0.30 mmol m−2 d−1; 0.22 mmol m−2 d−1) > Neuglobsow (0.12 mmol m−2 d−1; 0.12 mmol m−2 d−1). Output rates increase considerably at higher temperature. Mineralization of organic matter seems to be the key process in mobilization of accumulated elements. The rate of mineralization itself and the mechanisms to buffer the acidity produced by both N and S mineralization is affected by the different deposition history of the sites and by the changes in top soil properties induced by the long-term deposition impact. Due to the high element stores accumulated during the period of high deposition rates, the organic surface layer provides a large sulfur pool that will be released mainly by mineralization resulting in long-term sulfate leaching and the risk for future (re)acidification of soils and waters.

Abundance, diversity, and vitality of mycorrhizae of Scots pine (Pinus sylvestris L.) in lignite recultivation sites.

Scots pine (Pinus sylvestris L.) stands cover large areas in the Lusatian and the Middle German lignite mining districts. Due to adverse chemical substrate conditions, the root systems of the trees are restricted to the ameliorated top-spoil and the organic forest floor layers. To investigate functioning of fine root systems under the prevailing site factors, we studied mycorrhizal colonization rate and frequency as well as mycorrhizal diversity, vitality and growth phases in Scots pine ecosystems along a chronosequence in both mining districts. Mycorrhizal rate was close to 100% in both districts. Mycorrhizal abundance was higher in the organic forest floor layer than the mineral soil layer. In total, 25 morphotypes were recorded. Diversity differed between the districts. The mycorrhizae of Amphinema byssoides, Tuber puberulum, Pinirhiza discolor, Pinirhiza cf. bicolorata and E-type were present in both mining areas. These morphotypes are typical of nutrient-rich soils with high pH values. Compared with the undisturbed sites, vitality of mycorrhizae was very high at the test sites on spoil substrate, correlating with the high growth dynamics of mycorrhizae at recultivation sites. A relatively high carbon flow to the mycorrhizal root systems at these sites seems likely. Thus, mycorrhizal root systems are able to cope with the ameliorated top-spoil and the organic layer. The main reason for the adaptation is the large number of ectomycorrhizal fungal species available in this area where Pinus sylvestris is indigenous.

Short-term effects of liming and vitality fertilization on forest soil and nutrient leaching in a Scots pine ecosystem in Norway

The effects of liming and vitality fertilization on soil acidity, base cations and nutrient leaching were examined after four growing seasons in a Scots pine ecosystem in southern Norway. A randomized block field experiment was established in 1992 on a sandy, well drained, fluvial plain with a weakly podzolized soil (Cambic Arenosol). The Scots pine ( Pinus sylvestris L.) stand was by then 33 years old at breast height and had a medium site index class. The treatments consisted of a single application of 3000 kg lime or dolomite per hectare, or 6000 kg dolomite ha −1, and some of the plots were also fertilized with a combination of various amounts of KCl, superphosphate, kieserite, NH 4NO 3 or borax. In 1992 before the liming, the forest soil examined was highly acidic and nutrient-poor with fairly low reserves of exchangeable Mg and with a high pool of exchangeable Al. The most distinct liming effects such as an increase in soil pH and base saturation took place in the humus layer, where the highest portion of applied Ca and Mg was recovered. The treatment effects of lime were most evident, and these have spread more deeply into the soil than the effects of dolomite. The fast-release fertilizers increased the pools of exchangeable K and Mg down to at least 22 cm soil depth for the optimal treatment (no. 6), while the soil pH dropped 0.2 units in the upper part of the mineral soil. The pool of easily soluble P increased in the humus and eluvial horizon for this treatment too. A relatively small part of the added K and nearly half of the P addition could be recovered in the soil, while the B retention was very low. A great part of the applied N had been incorporated in the soil organic matter. There were clear treatment effects on the soil solution concentrations below the main root depth (80 cm) for all measured elements, except Al. About one-fourth to one-third of the highest added amounts of N, K, Mg, S and B were leached and slightly more than 10% of the added Ca was leached. The leaching was driven by the leaching of the anions of N and S.

Fire and site type effects on the long-term carbon and nitrogen balance in pristine Siberian Scots pine forests

Effects of fire and site type on carbon (C) and nitrogen (N) balances were determined by following the change of total and component C and N pools along four chronosequences of fire-prone Siberian Scots pine ecosystems. These differed in the mean return interval of surface fires (unburned – moderately burned, 40 years – heavily burned, 25 years) and site quality (lichen versus Vaccinium site type). Of the Vaccinium site type (higher site quality) only a moderately burned chronosequence was studied. A total of 22 even-aged stands were investigated with stand ages ranging from 2 to 383 years. The C balance was dominated by the opposing dynamics of coarse woody debris (CWD) and biomass and could be divided into three phases: (1) Young stands (up to 40 years)acted as a net source for C of 6-10 mol C m-2 year-1 because the previous generation CWD pool originating from stand-replacing crown fires decayed much faster than biomass increased. During this period the C pool in the unburned lichen type chronosequence decreased from 807 to 480 mol C m-2. (2) Middle aged stands (40-100 years) being in a stage of maximum biomass accumulation were a net sink of 8-10 mol C m-2 year-1. (3)Maturestands (100 to > 350 years) continued to sequester C at a lower rate (0.8-2.5mol C m-2 year-1). Differences in the rates of C sequestration during the two later phases could be explained by the complex interaction between surface fire regime and site type. Recurrent surface fires resulted in enhanced mortality and regularly redistributed C from the living to the CWD pool thereby lowering the rate of C sequestration. Site quality determined the potential to recover from disturbance by fire events. Differences in site type did not correlate with soil and total ecosystem N pool size. However, the N status of needles as well as the N pool of physiologically active tissue was highest in the stands of the Vaccinium type. The “woody” C pool (biomass + CWD) was sensitive to differences in surface fire regime and site type. It was lowest in the heavily burned lichen type chronosequence (297 ± 108 mol C m-2), intermediate in the unburned and moderately burned lichen type chronosequence (571 ± 179 mol C m-2) and highest in the moderately burned Vaccinium type chronosequence (810 ± 334 mol C m-2). In contrast, the total soil C pool (organic plus mineral layer down to a depth of 25 cm) was independent of stand age, surface fire regimeand site type and fluctuated around a value of 250 mol C m-2. The organic layer C pool oscillated in response to recurring surface fires and its C pool was dependent on time since fire increasing at a rate of about 1.5 mol C m-2 year-during the first 40 years and then reaching a plateau of 170 mol C m-2. The total ecosystem N pool was 7.4 ± 1.5 mol N m-2 on average of which only 25 % were stored in biomass or coarse woody debris. Total ecosystem N was independent of stand age, surface fire regime and site type. No correlation was found between total ecosystem C and N pools. Average total ecosystem C:N ratio was 114 ± 35 mol C mol N-1. A conceptual model illustrating how changes in the regime of stand-replacing crown fires and recurrent surface fires and changes in site quality interact in determining the long-term C balance in Siberian Scots pine forests is presented.

The impact of grazing on spatial variability of humus profile properties in a grass-encroached Scots pine ecosystem

Grazing is often used in management of grass-encroached Scots pine ( Pinus sylvestris) forests in The Netherlands, because it is thought to increase diversity of vegetation and humus profiles. To test this hypothesis, two 1 ha plots in a primary pine stand on drift sand were grazed for 7 years at high and moderate intensities. The humus profiles of these two sites and of a control site were sampled at various scales to assess changes in grass biomass, thickness of ectorganic horizons, organic matter stocks, root stocks, and pH. Whether grazed or not, site factors such as slope angle and aspect, distance to trees and parent material did not explain the spatial variability of the plots. Spatial variability could be linked to the tussock structure of the grass layer. With continued grazing, ectorganic horizons became more compact (particularly the F horizon), stocks of organic matter increased, grass biomass decreased, variances tended to decrease and ranges tended to increase. These results suggest that at the landscape scale, where much variation in grazing intensity can be expected, spatial variability of humus profile properties and thus site diversity will increase. However, grazing intensities in the experiment were far greater than those normally employed in management of grass-encroached forests. Therefore grazing will scarcely affect site diversity, unless grazing variability is enhanced by special treatments, such as temporary fencing to create locally high grazing intensities.

Metal and macronutrient fluxes in heavy-metal polluted Scots pine ecosystems in SW Finland

Cu, Ni, Zn, SO 4–S and macronutrient fluxes in Scots pine ecosystems were investigated during 1992–1996 at distances of 0.5, 4 and 8 km from the Harjavalta Cu–Ni smelter, SW Finland. The flux of water percolating down to a soil depth of 5 cm at 0.5 km was more than double that at 4 and 8 km. There was a net loss of Zn from the 40-cm thick soil layer, but a net gain for Cu, Ni and SO 4–S. Copper was more strongly retained in the organic layer than Ni. Cu, Ni and Zn fluxes at 0.5 km were extremely large compared to those at 4 and 8 km. The fluxes of Ca, Mg, K and PO 4–P to a depth of 5 cm at 0.5 km distance were much higher than the input via bulk precipitation, and the flux of Mg higher than the input in throughfall. There was a net loss of Mg and K at a depth of 40 cm compared to the input via bulk precipitation.

Soil solution chemistry and element budgets of three Scots pine ecosystems along a deposition gradient in north-eastern Germany

Since 1993 we are studying three Scots pine ecosystems along a deposition gradient in north-eastern Germany (formerly GDR). Dramatic reductions of pollutant emissions are reported for the period since 1989/90. S-deposition is high at the sites Roesa and Taura (25 kg S ha−1yr−1) compared to Neuglobsow. Inputs of basic cations, especially Ca, by alkaline dust immissions decrease in the order Roesa > Taura > Neuglobsow. The soil solution data show high concentrations of Ca and SO4 at Roesa decreasing drastically along the deposition gradient. The elevated pH values reflect the impact of alkaline dust deposition particularly in the organic surface layer at Roesa. The site Taura received less base cation deposition and is marked by the lowest pH values throughout the soil profile combined with increased Al concentrations in the solution of the mineral soil. Thus, the composition of the soil solutions clearly reflects the different deposition regimes of the past. The element budgets show that large amounts of base cations, sulfur, and, at Taura, also aluminum are actually released from the soils that were previously stored.

Reaction of mycorrhizal and non-mycorrhizal Scots pine fine roots along a deposition gradient of air pollutants in eastern Germany

Based on an ecosystematic approach within the comprehensive SANA (Regeneration of the atmosphere above the new federal states) -project the influence of industrial air pollutants (SO2, NOx, alkaline fly ashes) on the vitality of mycorrhizae, mycorrhizal frequency, and on parameters of root growth such as root biomass and necromass and distribution of different root classes in the soil horizons was investigated. The studies were conducted in three comparable Scots pine ecosystems in eastern Germany which were exposed to different deposition loads of air pollutants during the time of the former German Democratic Republic. Site specific differences were obtained for all parameters investigated. The reference plot Neuglobsow (background deposition) revealed the highest number of vital mycorrhizae, highest mycorrhizal frequency, and largest biomass of finest roots in the humus layer. At the impact-sites Roesa and Taura (heavy and moderate deposition) located near Halle/Bitterfeld and Leipzig, the number of vital mycorrhizae was reduced and the life-span of mycorrhizae of reduced vitality was elongated. Finest root biomass and necromass of the humus layer were also lower at these plots as compared to Neuglobsow. At Neuglobsow a higher turnover of mycorrhizae and finest roots of the humus layer is assumed. The reduced growth of mycorrhizal and non-mycorrhizal finest roots at the two pollution impacted sites Roesa and Taura is seen as an adaptation mechanism of the root system to high nutrient inputs.

Fertilizer nitrogen budget in a Scots pine ecosystem attained by using root-isolated plots and15N tracer technique

The distribution and quantitative recovery of isotopically labelled fertilizer N was studied in aPinus sylvestris L. stand in central Sweden. The investigation was carried out with root-isolated plots, area 31.2 m2, having a Scots pine aged 120–140 years in the centre of each plot. The fertilizer application rate was 100 kg ammonium nitrate-N per hectare, with either ammonium or nitrate being enriched with15N. The treatments comprised both a single and a split application. The analyses of needle biomass, collected during the first growing season showed that the proportion of labelled N in Ntot was greater in current needles than in older needles. Moreover, the isotopic enrichment was higher in treatments with labelled nitrate than in those with equivalent amount of labelled ammonium. Two growing seasons after fertilization the trees were felled and the distribution of labelled N in the system was determined. The study proved that the greatest proportion of labelled N in Ntot was in the needles and shoots of current and previous year's growth. The lowest proportion of labelled N was found in the stem wood and coarse roots. The proportion of labelled N in needles and shoots showed a tendency to increase with height in the crown. As regards bark and wood, the corresponding figures increased from the base to the top of the stem, and was higher in bark than in wood. Between 12 and 28% of the supplied N was recovered in trees, half of which in the needle biomass. In the above-ground parts of the shrub layer 3 to 13% of applied N was recovered. The corresponding recovery figure in the soil varied between 37 and 59% (excluding roots, but including litter and bottom layer). Between 5–8% was recovered in roots <30 mm. On the average, 79% of the supplied N was recovered in the studied part of the system. No significant differences in total15n recovery were found between treatments with ammonium or nitrate source of N, or those with different application techniques. The labelled N not recovered in the investigated part of the system, had presumably been lost by leaching.

Pollen Analysis of Mor Humus Layers from a Native Scots Pine Ecosystem, Interpreted with Surface Samples

The pollen content of the organic layers of nine soil profiles in the Forest of Abernethy, Inverness-shire was examined. From a discussion of the process of raw humus formation, it would appear that Mor is a broadly stratified deposit in which favourable conditions exist for the preservation of pollen, although a number of factors which may lead to the deterioration of pollen, or disturbance of stratification are also considered. Pollen diagrams from Mor profiles were interpreted with the aid of surface sample data from Abernethy presented in an earlier paper, 14C-dating of soil material, and documentary evidence. It is concluded that substantial areas of Calluna-dominated heathland have existed in Abernethy since at least AD 400, and that prior to heathland formation, some parts of Abernethy may have contained vegetation consistent with the presence of Mull rather than Mor.