Effects of tree species and topography on soil chemistry, litter quality, and decomposition in Northeast Turkey

Leaf litters from beech (Fagus orientalis Lipsky.) and oak (Quercus robur L.), and needle litters from fir (Abies nordmanniana Spach.) and pine (Pinus sylvestris L.) trees were collected from north-facing site and south-facing site and at three slope positions (top, middle and bottom) on each aspect that varied in soil chemical characteristics (soil pH, cation exchange capacity and base saturation). The litters were analysed for initial total carbon, nitrogen, acid detergent fibre, lignin and cellulose concentrations. Nitrogen, acid detergent fibre and lignin concentrations and carbon:nitrogen and lignin:nitrogen ratios varied significantly within and between species according to soil chemical characteristics on aspects and slope positions. Litter decomposition was studied in the field using the litterbag technique. The litters were placed on two aspects and at three slopes on each aspect in October 2001, and were sampled every 6-month for 2 years. The main effects of aspect, species and slope position on decomposition rates were all statistically significant. Oak leaf litter showed highest decomposition rates, followed by pine, fir and beech litter, and the litters placed on north-facing site decomposed faster than those on the south-facing site. The litters placed at the top slope position decomposed slower than at those at either the bottom or middle positions. Initial lignin concentrations explained most of the variation in decomposition rates between species, and within species for the aspects and the slope positions, but the explained variance showed differences between aspects and slope positions. This result illustrates the important point that litter quality may define the potential rates of microbial decomposition but these are significantly influenced by the biotic and abiotic environment in which decomposition takes place.     

Geographic origin of Pinus sylvestris populations influences the effects of air pollution on flowering and growth

Flowering and height growth of 20 Scots pine (Pinus sylvestris L.) populations from 10 countries were analyzed at two replicated provenance sites established in 1984 in western Poland. One site was 2 km from a phosphate fertilizer factory that emits SO₂ and fluorides, and the other 12 km to the southeast in an area free of acute air pollution levels was treated as a control. Slow-growing populations from the southern (40 to 45°N) and northern (58 to 61°N) part of the species range exhibited relatively smaller air pollutioninduced growth reductions than those from the central part of the range (45 to 58°N). Trees growing in the control area started flowering 4 yrs earlier than those at the polluted site. The percent of trees flowering at the control site differed significantly among provenances in both 1988 and 1990. The mean percent of trees with flowers was three times lower at the polluted site. The least sensitive southern and northern provenances in terms of pollutioninduced reductions in growth exhibited the largest pollution-induced decreases in flowering. These findings indicate that the sensitivity of vegetative organs to air pollution stress is not always paralleled by the sensitivity of reproductive organs.     

The effect of stand structure and tree species composition on epiphytic bryophytes in mixed deciduous-coniferous forests of Western Hungary

The effect of tree species, stand structure, landscape and historical variables was studied on the species composition, species richness and cover of epiphytic bryophyte assemblages in mixed deciduous-coniferous forests of Western Hungary. Stand and tree level assemblages were analyzed by ordinations and generalized linear modeling in 35 70-110 year old stands of different management regimes.Bryophytes showed a considerable preference to different host trees, so that stand level diversity of bryophyte assemblages was determined mainly by tree species diversity, and their composition by tree species composition. Cover and diversity of epiphytic bryophytes were the highest on oaks (Quercus petraea and Quercus robur), and the lowest on Scotch pine (Pinus sylvestris). The presence of sapling (shrub) layer increased, whereas a large number of medium sized trees decreased bryophyte species richness in this study. Tree size was much less influential which is explained by the lack of large, veteran trees. Forest management maintaining tree species diversity, structural heterogeneity and temporal continuity of the stands could considerably contribute to the conservation of this organism group. Selective cutting is more appropriate for these conservational purposes than shelterwood management system.     

Regeneration of mixed deciduous forest in a Dutch forest-heathland, following a reduction of ungulate densities

The conversion of single-species coniferous forest stands into mixed stands by promoting the natural regeneration of indigenous broadleaved tree species was studied in a forest-heathland on the Veluwe, in the central part of the Netherlands. Red deer (Cervus elaphus), roe deer (Capreolus capreolus) and wild boar (Sus scrofa) had a large impact on regeneration dynamics, as was established by comparing 20 pairs of fenced and unfenced plots (40 × 40 m) during a 10-year period. A fivefold reduction of total herbivore biomass to 500 kg per km², resulted in a strong increase of shrub and tree sapling numbers in all vegetation types. However, height growth of the most palatable broadleaved tree species was still strongly impeded. Under the present-day grazing pressure, Scots pine (Pinus sylvestris) and beech (Fagus sylvatica) will become the dominant canopy species in the forests in the near future. It is argued that the most browse-sensitive woody species such as pedunculate and sessile oak (Quercus robur and Q. petraea) will successfully regenerate, only if temporal and spatial variation in browsing pressure is allowed to occur.     

Bryophyte species richness on boulders: relationship to area, habitat diversity and canopy tree species

Bryophytes growing on siliceous boulders (diameter 50-200 cm) were studied in two forests in east-central Sweden to investigate the influence of different canopy tree species on the bryophyte species richness. Granite boulders lying below crowns of Ulmus glabra (elm), Fraxinus excelsior (ash), Acer platanoides (maple), Quercus robur (oak), Betula pendula (birch), and Picea abies (Norway spruce) were studied in two mixed stands. Both boulder area and within-boulder habitat diversity were positively related to species richness. Boulders below the base-rich deciduous trees F. excelsior, U. glabra and A. platanoides held roughly twice as many species as those below P. abies, with Q. robur and B. pendula as intermediates. The rank order among trees was as expected from bark pH and litter decomposability in the literature. We also used sample plots to investigate species richness at a smaller scale. Within plots, intermediate levels of litter, inclination and exposed rock promoted species richness, and also the covering tree species had an effect. Individual plots were on average not more species-rich on large boulders than on small ones. This leads us to conclude that population extinctions on the plot-level, and re-colonisations from other parts of the boulder, are less important for species richness than within-boulder habitat diversity. Since species richness was lower under P. abies it is important to favour a diversity of tree species and to include base-rich deciduous trees in otherwise homogeneous Picea forests.     

Carbon and nitrogen transfer in leaf litter mixtures

The decomposition rate of litter mixtures can differ from that expected on the basis of the decomposition rate of the individual components. This difference may be linked to nitrogen (N) transfer from high-N to low-N components. Transfer of N is probably also associated with transfer of C, but the extent and direction of this C transfer are unknown. This study examined transfer and loss in laboratory microcosms of C and N from two mixed litter species (Scots pine, Pinus sylvestris L. and maize, Zea mays L.), which have natural isotopic differences in ¹³C. Half the material was ¹⁵N-labelled and the plants were fertilised or unfertilised. Substantial bidirectional transfer of C and N occurred between the litters, with net transfer of C from pine to maize litter and net transfer of N from high-N to low-N litter. Mixtures of fertilised and unfertilised plant litter showed higher than expected C losses and net transfer of N. Mixtures with litters from the same fertilisation treatment had small or insignificant net transfer of N and their C losses did not differ from values estimated using the decomposition rates of the pure litters.     

Nitrogen and phosphorus dynamics in foliage and twig of pitch pine and Japanese larch plantations in relation to fertilization

Seasonal foliage and twig nitrogen (N) and phosphorus (P) dynamics were determined for 40‐year‐old pitch pine (Pinus rigida Mill.) and Japanese larch (Larix leptolepis Gord.) plantations established on similar soils in central Korea. Also, the effects of three levels of N plus P fertilizers on N and P retranslocation were evaluated. In general, Japanese larch had significantly higher current foliage N and P concentrations than pitch pine, and N and P concentrations were higher in foliage than those in twigs for both study species. Foliage N and P concentrations were highest in mid‐growing season and lowest in autumn whereas twig N and P concentrations increased during foliage senescence, suggesting that twig served as a storage tissue. We did not find differences in foliage N and P retranslocation between pitch pine and Japanese larch; current foliage N and P retranslocation of the control trees were 35% and 56% for pitch pine, and 39% and 59% for Japanese larch, respectively. There were no consistent patterns in foliage and twig N and P retranslocation following fertilization.     

Estimates of atmospheric deposition and canopy exchange for three common tree species in the Netherlands

During one year, dry and wet deposition onto thirty forest stands is studied by sampling throughfall and bulk precipitation. Nine measurement sites are situated in Douglas fir (Pseudotsuga menziesii Mirb. Franco) stands, ten in Scotch pine (Pinus sylvestris L.) and eleven in Oak (Quercus robur L.) stands. Because the stands are situated in each other's proximity (i.e. within a radius of approximately 1.4 km) it is assumed that they experience an approximately equal air pollution load. For the acidifying compounds SO₄ ^2?, NO₃ ^? and NH₄ ⁺ spatial variability in wet deposition was small within the area studied. Dry deposition, as estimated by net throughfall, displayed a much higher spatial variability. Significant differences existed between tree species and growing seasons. Douglas fir mostly displayed the highest, Oak the lowest and Scotch pine intermediate values for net throughfall fluxes of acidifying compounds. The annual net throughfall fluxes for nitrogen compounds were significantly higher for the coniferous tree species than the broadleaved tree species. For SO₄ ^2?, however, Oak showed a relatively high throughfall flux during the summer. By comparing the temporal pattern of net throughfall fluxes between the three tree species it was concluded that considerable canopy leaching occurred for SO₄ ^2?, Mg⁺, PO₄ ^3?, HCO₃ ^? and K⁺ in Oak stands during the sprouting of leaves in spring. From surface wash experiments in the laboratory it is concluded that canopy leaching of these ions may also be enhanced when Oak leaves are infected by Oak mildew, a fungal disease caused by the fungus Microshaera aliphilitoides.     

How do coniferous needle tannins influence C and N transformations in birch humus layer?

The aim of this study was to explore the response of C and N transformations in the humus layer under silver birch (Betula pendula Roth) to compounds, especially condensed tannins, of different molecular weight extracted and fractioned from Norway spruce (Picea abies (L.) Karst) and Scots pine (Pinus sylvestris L.) needles. Lighter fractions containing tannin monomers and dimers as well as many other compounds, and heavier fractions consisting predominantly of polymerized condensed tannins, were added to samples taken from the humus layer of birch stand. The effects of the spruce and pine fractions were mostly similar, but some differences in magnitude were observed; our results indicated that lighter fractions of pine were easier for microbes to degrade and use than lighter fractions of spruce. Lighter fractions of both tree species increased soil respiration and decreased net N mineralization, while heavier fractions inhibited respiration and increased net N mineralization. Microbial biomass C was not clearly affected by any of the treatments, but with some of the pine fractions the amount of N in the microbial biomass was increased. Comparison of the effects of fractions in birch and in spruce and pine soils, which were studied earlier, showed no major differences between the effects of the fractions in birch and in their own soils, but gave some indication of adaptation.     

Nitrogen and phosphorus transformations in the rhizospheres of three tree species in a nutrient-poor sandy soil

We examined acid phosphatase activity (APA), N mineralization and nitrification rates, available N and P, and microbial biomass C, N and P in rhizosphere and bulk soils of 18-year-old Siberian elm (Ulmus pumila), Simon poplar (Populus simonii) and Mongolian pine (Pinus sylvestris var. mongolica) plantations on a nutrient-poor sandy soil in Northeast China. The main objective was to compare the rhizosphere effects of different tree species on N and P cycling under nutrient-deficient conditions. All tree species had the similar pattern but considerably different magnitude of rhizosphere effects. The APA, potential net N mineralization and nitrification rates increased significantly (by 27–60%, 110–188% and 106–142% respectively across the three species) in rhizosphere soil compared to bulk soil. This led to significantly higher Olsen-P and NH₄⁺-N concentrations in rhizosphere soil, whereas NO₃⁻-N concentration was significantly lower in rhizosphere soil owing to increased microbial immobilization and root uptake. Microbial biomass C and N generally increased while microbial biomass P remained constant in rhizosphere soil relative to bulk soil, indicating the N-limited rather than P-limited microbial growth. Rhizosphere effects on P transformation were most pronounced for Siberian elm, while rhizosphere effects on N transformation were most pronounced for Mongolian pine, implying the different capacities of these species to acquire nutrients.     

Soil Amendment Improves Tree Growth and Soil Carbon and Nitrogen Pools in Mongolian Pine Plantations on Post‐Mining Land in Northeast China

Mining activities leave large areas of post‐mining lands to be reclaimed. Increases in soil C and N pools and N availability are important to successfully reestablish trees on post‐mining land. In this study, we determined C and N concentrations and natural stable isotope of ¹³C and ¹⁵N in soil and plant in Mongolian pine (Pinus sylvestris L. var. mongolica Litv.) plantations 8 years after establishment on non‐mined land (NM), post‐mining land without soil amendment (NAM), and post‐mining land with soil amendment (AM) in a placer gold mining region of Northeast China. We found that the growth of Mongolian pine was significantly slower on NAM as compared with NM (decreasing by 73% in tree height and 63% in basal diameter), but tree growth improved on AM. Soil C and N concentrations, plant N concentration, and soil δ¹⁵N value decreased in the order of NM > AM > NAM, implying that soil N availability decreased in post‐mining land, but soil amendment could increase soil N availability. However, the values of δ¹⁵N in plant tissues of Mongolian pine were higher on NAM than on NM and AM, suggesting that soil inorganic N form absorbed by trees might be changed when trees were directly planted on post‐mining land with lower soil N availability. In addition, the values of δ¹³C in 1‐ and 2‐year‐old leaves of Mongolian pine were lowest when planted on NAM, indicating a decrease in intrinsic water‐use efficiency of Mongolian pine. Our results suggest that soil amendment helps us establish forests successfully on post‐mining lands. Copyright © 2015 John Wiley & Sons, Ltd.     

Microbial biomass and activity in soil and litter underPinus sylvestris, Picea abies andBetula pendula at originally similar field afforestation sites

Microbial biomass C and N, and activities related to C and N cycles, were compared in needle and leaf litter, and in the uppermost 10 cm of soil under the litter layer in Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies L.) and silver birch (Betula pendula L.) stands, planted on originally similar field afforestation sites 23–24 years ago. The ground vegetation was differentiated under different tree species, consisting of grasses and herbs under birch and pine, and mosses or no vegetation with a thick layer of needles under spruce. The C:N ratio of the soils was 13–21 and the soil pH_{CaCl 2} 3.8–5.2. Both showed little variation under different tree species. Microbial biomass C and N, C mineralization, net ammonification, reduction) did not differ significantly in soil under different tree species either. Birch leaf litter had a higher pH_{CaCl 2} (5.9) than spruce and pine needle litter (pH 5.0 and 4.8, respectively). The C:N ratio of spruce needles was 30, and was considerably higher in pine needles (69) and birch leaves (54). Birch leaves tended to have the highest microbial biomass C and C mineralization. Spruce needles appeared to have the highest microbial biomass N and net formation of mineral N, whereas formation of mineral N in pine needles and birch leaves was negligible. Microbial biomass C and N were of the same order of magnitude in the soil and litter samples but C mineralization was tenfold higher in the litter samples.     

Pine processionary caterpillar Thaumetopoea pityocampa as a new threat for relict Mediterranean Scots pine forests under climatic warming

The wide distribution of Scots pine (Pinus sylvestris L.) in Europe includes two relict populations in southern Spain (Sierra Nevada and Sierra de Baza), belonging to the subspecies nevadensis. These populations are isolated in high mountains, which tends to protect them from the attack of a severe defoliating Mediterranean pest, the pine processionary moth Thaumetopoea pityocampa. However, as a consequence of climate change, the pine processionary caterpillar has increasingly attacked populations of this pine in recent years. This work describes the detrimental effects of defoliation by the pine processionary caterpillar in P. sylvestris subsp. nevadensis in Sierra Nevada. Defoliation strongly reduced pine growth as well as all the reproductive parameters measured (female and male cone production, mature cone size, seed production and seed weight), in addition to some deaths. If winter temperatures continue to increase, the pine processionary caterpillar will have a dangerous impact in these relict pine populations, by further reducing the pine's weak regeneration capacity. We suggest some mitigation actions based on managing habitat structure, in order to reduce or avoid such negative impacts.     

Growth of Loblolly Pine and White Pine after Enrichment by Nutrient Loading

Low nutrient availability often constrains the growth of young trees following planting to fields or forests. Nutrient loading of young tree seedlings increases their growth in outplanting. Loblolly pine (Pinus taeda L.) and white pine (Pinus strobus L.) were grown for one year on nutrient-loading regimes that varied from 13 to 410 mg N L^?1 in sand culture. Other nutrients varied in proportion to the nitrogen (N) concentrations. Resulting plant growth showed that an array of nutritional regimes from deficient to excessive was applied. The young plants were transplanted into containers of sandy loam and were grown for one year without fertilization. Growth of each species increased with enhanced nutrient loading. The optimum concentration of N for nutrient loading was about 1.5 to 1.8% leaf dry weight for either species. Nutrient loading during nursery culture imparts transplants with nutrient levels that will enable growth for at least a year after outplanting.     

Heavy Metals in Polish Forest Stands of Quercus Robur and Q. Petraea

This study aimed to compare concentrations of Zn, Cd, Pb and Cu in wood of Quercus robur and Q. petraea and in the soil on 21 plots in different parts of Polish lowlands. Concentrations of those metals in growth rings taken with an increment borer were measured in 20-year periods. The curves of radial distribution of heavy metals in growth rings are highly variable, but usually a greater variation was observed in sapwood than in heartwood. This attests to transport of metals in the younger, functional xylem, and confirms earlier observations. Quercus petraea accumulated significantly more Zn but less Cd than Q. robur, while concentrations of other metals were similar in both species. No significant correlations between levels of different metals in oak wood were detected, except a strong correlation between Pb and Cd. Concentrations of heavy metals in oak wood were generally not correlated with their concentrations in the soil. Most of the forest stands can be regarded as free from pollution with heavy metals.     

Determinants of soil organic matter chemistry in maritime temperate forest ecosystems

While the influence of climate, vegetation, management and abiotic site factors on total carbon budgets and turn-over is intensively assessed, the influences of these ecosystem properties on the chemical complexity of soil organic matter (SOM) remains poorly understood. This study addresses the chemical composition of NaOH-extracted SOM from maritime temperate forest sites in Flanders (Belgium) by pyrolysis-GC/MS. The studied forests were chosen based on dominant tree species (Pinus sylvestris, Fagus sylvatica, Quercus robur and Populus spp.), soil texture and soil-moisture conditions. Differences in extractable-SOM pyrolysis products were correlated to site variables including dominant tree species, management of the woody biomass, site history, soil properties, total carbon stocks and indicators for microbial activity. Despite of a typical high intercorrelation between these site variables, the influence of the dominant tree species is prominent. The extractable-SOM composition is strongly correlated to litter quality and available nutrients. In nutrient-poor forests with low litter quality, the decomposition of relatively recalcitrant compounds (i.e. short and mid-chain alkanes/alkenes and aromatic compounds) appears hampered, causing a relative accumulation of these compounds in the soil. However, if substrate quality is favorable, no accumulations of recalcitrant compounds were observed, not even under high soil-moisture conditions. Former heathland vegetation still had a profound influence on extractable-SOM chemistry of young pine forests after a minimum of 60 years.     

A seeding experiment for testing tree-community recruitment under variable environments: Implications for forest regeneration and conservation in Mediterranean habitats

As a result of historical and ecological factors, woody-plant communities are composed of species with different biogeographic origins that presumably diverge in their ability to recruit under variable environments. The aim of this study is to evaluate the conservation implications of the differences in recruitment of six tree species of different biogeographical origin coexisting in a Mediterranean mountain forest. Under field conditions, we experimentally sowed a total of 16,650 seeds belonging to two Mediterranean (Quercus ilex and Q. pyrenaica), two Sub-Mediterranean (Acer opalus subsp. granatense and Sorbus aria), and two boreo-alpine (Pinus sylvestris and Taxus baccata) species. We selected the three most common successional scenarios where seeds are dispersed (woodland, shrubland, and open areas), and half of the seeds were irrigated simulating a rainy summer in terms of Mediterranean ecosystems. Seedling survival was strongly affected by the type of habitat as well as irrigation. The recruitment of the six species was possible only in wooded areas under wet conditions (20-60%). In shrubland, only Mediterranean and Sub-Mediterranean species recruited in typical dry years (10-50%), but irrigation increased their survival (25-65%) and allowed P. sylvestris to recruit (32%). Open areas constituted the most adverse scenario for seedling recruitment, especially for non-watered seedlings (0% for boreo-alpine species, 1-24% for the rest). Overall, the benefit of a wet summer was more critical for the recruitment of boreo-alpine species (P. sylvestris and T. baccata) than for the rest, although a rainy summer is also necessary for the recruitment of A. granatense and S. aria in shrubland habitats. Our experimental results indicate that the maintenance of current species composition in Mediterranean mountain forests is critically dependent on the periodic, scattered occurrence of wet summers. From a conservational standpoint, the predictions of less rainy summers and greater aridity in the future imply a change in the relative abundance of species in the mature forest, with Mediterranean species becoming dominant and boreo-alpine species becoming even rarer and, consequently, a serious threat for the persistence of boreo-alpine species at their southern distribution limit.     

Diversity of the European indigenous wild apple Malus sylvestris (L.) Mill. in the East Ore Mountains (Osterzgebirge), Germany: I. Morphological characterization

Malus sylvestris (L.) Mill. is the only indigenous wild apple species in Europe and recognized as rare and endangered species. An important prerequisite for the preservation of M. sylvestris is the identification of ‘true type’ M. sylvestris individuals because hybrids with cultivated apple could be also occurred. In this study variations among 625 putative M. sylvestris trees originated in the East Ore Mountains were evaluated with 20 selected morphological traits. The importance of these traits concerning the differentiation of ‘true type’ and hybrids of M. sylvestris were determined by statistical analysis. The results demonstrated a strong correlation of individual traits and those contributing mostly to variation of M. sylvestris were detected by the Principal Component Analysis. The relationship of 284 M. sylvestris, 18 M.?×?domestica, M. floribunda 821 and M. robusta 5 individuals were calculated based on the morphological data and presented in a dendrogram. The individuals grouped in two main clusters and 68 hybrids of M. sylvestris were identified. The main result of the morphological data of these hybrids indicates that the grouping is mainly based on the flower and leaf pubescence and less on the fruit size.     

Can a diazotrophic endophyte originally isolated from lodgepole pine colonize an agricultural crop (corn) and promote its growth?

Several diazotrophic Paenibacillus strains were isolated from extracts of surface-sterilized lodgepole pine seedling and tree tissues. One strain, Paenibacillus polymyxa P2b-2R, was found to fix high amounts of nitrogen when reintroduced to the gymnosperms, lodgepole pine and western red cedar. We wanted to determine if P. polymyxa P2b-2R could colonize rhizosphere and internal tissues, fix N and promote growth of corn (Zea mays L), an important agricultural crop. We inoculated corn seeds with P. polymyxa strain P2b-2R and grew seedlings for 30 days. Corn seedlings were harvested 10, 20 and 30 days after inoculation for evaluation of endophytic and rhizospheric colonization as well as nitrogen fixation and growth promotion. P2b-2R successfully colonized the rhizosphere as well as internal root tissues of corn (i.e., endophytically) with population densities near 10⁶ cfu. Corn seedling growth was promoted significantly by inoculation with P2b-2R with an increase of up to 35% in length and up to 30% in biomass after 30 days of inoculation. Seedlings inoculated with P2b-2R derived up to 20% of foliar nitrogen from atmosphere after 30 days of inoculation, which is significant considering the fact that this was a short growth trial. These results suggest that P. polymyxa P2b-2R might have a broad range of plant hosts and is able to fix N and promote the growth of at least one important agricultural crop i.e. Corn.     

Long-Term Acid Load and its Consequences in Forest Ecosystems of Saxony (Germany)

Between 1993 and 1995 a system of six intensive monitoring stations in representative stands of Norway spruce (Picea abies), sessile oak (Quercus robur) and Scots pine (Pinus sylvestris) were installed in forests of Saxony (Germany), they are integrated in the European Level II - Programme. As a complementary system, and in addition to the annual nation-wide forest decline survey, 280 sites within the forest soil condition survey (European Level I - Programme) have been examined since 1992. The results of deposition monitoring show that until 1997 the acidity in precipitation and troughfall still was very high, despite of strong reductions in industrial emissions between 1989 and 1992. The annual fluxes (hydrological year 1996) of sulphur in throughfall ranged between 16 and 77 kg-ha^-1, whereas the fluxes of total inorganic N varied between 17 and 46 kg-ha^-1. The forest soils show high degrees of acidification with only low base saturation. In most cases the nutrient status of the soils has to be improved in the course of a regeneration programme in order to rebuild more natural forest ecosystems.