Mesotrophic Soils Research Articles

PLANT COVER OF THE LOCAL LANDSCAPE RESERVE «HARIACHYI URBAN» (CHERNIVTSI CITY)

The results of the studies of forest communities on the local landscape reserve «Hariachyi Urban» (Chernivtsi city) are presented. It was established that forest vegetation divided into 2 alliances, and 2 orders of the class Carpino-Fagetea sylvaticae Jakucs ex Passarge 1968. These communities represent 2 habitat types from the Annex I of the Habitats Directive: 9130 Asperulo-Fagetum beech forests and 9170 Galio-Carpinetum oak-hornbeam forests, and 2 biotope types from the Resolution 4 of the Bern Convention: G1.6: Beech forests (Fagus woodland) and G1.A1 Quer-cus – Fraxinus – Carpinus betulus woodland on eutrophic and mesotrophic soils, respectively. Also, coenoses men-tioned in the «Green Book of Ukraine» (2009), e.i. common oak forests (Querceta roboris) with common ivy (Hedera helix) domination, are presented here. So, it confirms an important role of this local reserve for biodiversity conserva-tion. According to the literature and herbaria (CHER) data, since the 2nd half of the 19th century, 18 rare plant species listed in the «Red Data Book of Ukraine» (2009) were noticed for this area. For 13 species, the current localities have not been confirmed. Among them, 8 species were associated with grassland, that have not been preserved here, and 5 species were sylvatic. During the last 50 years, 5 plants species from the «Red Data Book of Ukraine» (2009) have been found on the studied area, and only 3 species were confirmed in this study. In studied plant communities, 8 alien plant species were noticed, which indicate the increasing of adventitization rate. Therefore, changes in forest plant communities can be traced in direction of the disappearance of rare plant spe-cies caused by the destruction of landscapes, fragmentation and degradation of preserved natural biotopes, and in-tensification of recreational activity. In addition, increasing of the synanthropization rate and expansion of alien plant species, including species with a high invasive potential, are observed. The initiated inventory studies of the floristic and coenotic diversity in the local reserve will serve as the basis for organizing its phytodiversity state moni-toring.

Effect of Bark-Stripping on Mechanical Stability of Norway Spruce

The increasing effects of storms are considered the main abiotic disturbance affecting forest ecosystems. Bark-stripping damage from the growing ungulate populations, in turn, are among the main biotic risks, which might burden the stability of trees and stands. Therefore, the aim of our study is to estimate the effect of cervid bark-stripping on the mechanical stability of Norway spruce using a static tree-pulling test. For the test, eight damaged and 11 undamaged canopy trees were selected from a 40-year old stand (plantation with 1 × 3 m spacing) growing on mineral mesotrophic soil. The selected trees were bark-stripped 7–9 years prior to the experiment. Uprooting was the most frequent type of failure; only two trees broke at the stem. For the damaged trees, the resistance to pulling was significantly reduced (p-value < 0.001). Stem volume and presence of bark-stripping were the best linear predictors of the basal bending moment at the primary failure (irreversible deformation of wood structure) and secondary failure (collapse of the tree). A significant (p-value < 0.001) interaction between stem–wood volume and presence of bark-stripping was observed for primary failure, indicating a size-dependent reduction of stability of the damaged trees. Such interaction lacked significance (p-value = 0.43) for the secondary failure (mostly uprooting), indicating a decrease in stability irrespectively of tree size. Somewhat surprisingly, the decrease in the overall mechanical stability of the bark-stripped trees appeared not to be related to a direct reduction of the strength of the stems, but rather to physiological effects such as altered allocation of carbon, increased drought stress because of interfered hydraulic conductance of wood, or secondary infestation. The reduced stability also suggests that bark-stripped trees can act as the weak spots decreasing the collective stability of stands in the long term, thus increasing the susceptibility to storms.

Direct and understorey-mediated indirect effects of human-induced environmental changes on litter decomposition in temperate forest

Human-induced environmental changes in temperature, light availability due to forest canopy management, nitrogen deposition, and land-use legacies can alter ecosystem processes such as litter decomposition. These influences can be both direct and indirect via altering the performance of understorey vegetation. To identify the direct and indirect effects of environmental changes on litter decomposition, we performed an experiment with standardised green and rooibos teas. The experiment was conducted in a temperate mixed deciduous forest, and treatments (temperature, light, and nitrogen) were applied to mesocosms filled with ancient and post-agricultural forest soil. Both green tea and rooibos teas were more rapidly decomposed in oligotrophic soil than in eutrophic soil. The direct effects of the treatments on litter decomposition varied among the two litter types, incubation times, and soil fertility groups. Warming and agricultural legacy had a negative direct effect on the decomposition of the green tea in the high soil fertility treatment during the early decomposition stage. In contrast, agricultural legacy had a positive direct effect on the decomposition of rooibos tea. Soil enriched with nitrogen had a negative direct effect on the decomposition of green tea in mesotrophic soil in the early decomposition stage and on rooibos tea in later stage. The indirect effects of the treatments were consistently negative, as treatments (especially the temperature and light treatments in the early decomposition stage) had a positive effect on plant cover, which negatively affected litter decomposition. Our results indicate that warming, increased nitrogen deposition, and land use legacy can directly stimulate the decomposition of labile litter on more fertile soils. Furthermore, warming and increased light had stronger positive direct effects on understorey herbaceous cover, which leads to slower decomposition rates, especially in more fertile soils. Therefore, the indirect effects of environmental changes related to the understorey layer on litter decomposition can be more important than their direct effects, thus should not be overlooked.

Trophic conditions of forest soils of the Pieniny National Park, southern Poland

Abstract The primary objective of this study was to characterise the edaphic conditions of forest areas in the Pieniny National Park (PNP), and to describe the dependencies between properties of forest soils and types of forest plant communities. The “Soil Trophic Index” (SIGg) for mountainous areas was applied. The evaluation of the trophism for 74 forest monitoring employed the soil trophic index for mountainous areas SIGg or SIGgo. Plant communities in the forest monitoring areas were classified according to the Braun-Blanquet’s phytosociological method. Soils of PNP present in the forest monitoring areas were mostly classified as eutrophic brown soils (72.9%), rendzinas (10.8%), brown rendzinas (5.41%), and rubble initial soils (5.41%). Pararendzinas, dystrophic brown soils, and gley soils were less common (total below 5.5%). In the forest monitoring areas of PNP, eutrophic soils predominate over mesotrophic soils. High SIGg index of the soils is caused by high values of acidity and nitrogen content. The Carpathian beech forest Dentario glandulosae-Fagetum and thermophilic beech forest Carici albae-Fagetum associations are characterised by high naturalness and compatibility of theoretical habitats. The soils of the Carpathian fir forest Dentario glandulosae-Fagetum abietetosum subcommunity is characterised by a higher share of silt and clay particles and lower acidity as compared to the Carpathian beech forest Dentario glandulosae-Fagetum typicum subcommunity. The soils of the forest monitoring areas in PNP stand out in terms of their fertility against forest soils in other mountainous areas in Poland.

Is the positive response of seed germination to plant-derived smoke associated with plant traits?

Relationships between seed germination response to plant-derived smoke and various plant traits (habitat requirements, life form, seed morphology, seed bank type) were analysed for 97 species of the Hungarian flora using published data. It was hypothesized that smoke-responsive species – those displaying enhanced germination in response to smoke – differ from non-responsive species – smoke having an indifferent or inhibitory effect on germination – in habitat requirements and/or certain life history traits. To our knowledge, no such comparison has previously been reported for a European flora. We found that species indicating disturbance and those preferring soils rich or moderately rich in nitrogen were more frequent in the smoke-responsive group (80% and 41%, respectively) than in the non-responsive group, while the non-responsive group contained a high percentage of natural species (i.e. species dominant or characteristic in natural plant communities; 47%) and species indicative of nutrient poor (38%) or (sub)mesotrophic (38%) soils. Annuals or biennials (67%) dominated the smoke-responsive group, whereas in the non-responsive group these short-lived species and perennial herbs were equally abundant (43% each). There was a tendency for higher frequency of long-term persistent seed bank among smoke-responsive species (78%) than in the non-responsive group (54%). These findings suggest that smoke-stimulated germination is associated with only a few specific plant traits for species from a semiarid temperate region of Europe, but highlight the frequent occurrence of smoke-enhanced germination among short-lived, nitrophilous or disturbance tolerant species. These results can contribute to a better understanding of post-fire regeneration of plant communities, and could also be considered during vegetation restoration or weed management.

Determinants of the Fynbos/Succulent Karoo biome boundary: Insights from a reciprocal transplant experiment

Boundaries between Fynbos and Succulent Karoo vegetation in the Greater Cape Floristic Region are frequently characterised by sharp transitions from sandy, dystrophic to loamy, mesotrophic soils, together with a more gradual climate transition from cooler, wetter conditions typical of Fynbos at higher elevations to warmer, drier conditions at lower elevations typical of Succulent Karoo. There is very high species turnover across these boundaries, providing an opportunity to disentangle the relative roles of climate and soil type in determining the biome boundary. A fully reciprocal transplant approach was employed here to investigate this question, using three species from each biome occurring naturally in close proximity at Jonaskop, Western Cape. Greenhouse-germinated and established seedlings of all species were planted into both sandy, dystrophic and loamy, mesotrophic soils typical of each biome at four sites along an elevational transect (elevations 545m, 744m, 953m, 1303m) at Jonaskop, and their growth and survivorship monitored for 7months.At least one site on the elevation gradient represented annual climate rainfall and temperature conditions during the experimental period typical of the range edge for each of the selected species, this typically being the lowest elevation site (warm×dry) for Fynbos species (Protea humiflora, P. magnifica and P. amplexicaulis), and the highest elevation site (cool×wet) for Succulent Karoo species (Ruschia lineolata, Drosanthemum speciosum and Pteronia incana). Fynbos species showed significant adverse responses to loamy mesotrophic soil, with highly significant reductions in growth and high and rapid rates of mortality relative to their native soil. Fynbos species showed somewhat reduced growth and survival at the lowest elevation when grown in native soils, but demonstrated significant interaction between soil type and elevation with much lower growth and survival at the lowest elevation on the loamy soils. Surprisingly, all the Fynbos species showed reductions in growth and survival at the highest elevation, with significant reductions in two of the three species. Succulent Karoo species, by contrast, showed very few significant performance differences between soil types and few significant soil×elevation interactive effects, but did show significant growth and survival responses to elevation, with high growth and survival at mid-level elevations, far higher than their natural extent at the site.These results suggest that the selected Succulent Karoo species are neither edaphically nor climatically constrained from establishing and growing in sandy dystrophic soils and cool climates typical of the Fynbos vegetation along this elevation gradient, but that Fynbos species are strongly limited both edaphically and climatically from growing under conditions typical of the Succulent Karoo. We propose that Succulent Karoo elements may be excluded competitively or through disturbance from colonising sandy dystrophic soils at higher elevations in Fynbos vegetation, with fire regime most likely responsible for maintaining the sharply delineated boundaries between these biomes. This is because fire would strongly exclude non-fire adapted Succulent Karoo species at and above the biome boundary, while loamy soils and climate together would strongly exclude Fynbos species from the heavier soils of the Succulent Karoo. The relative climate and soil affinities of these biomes, accentuated by the role of fire, could therefore provide a coherent explanation for biome boundaries in the Greater Cape Floristic Region. We note however that the limited species selection in this study precludes a conclusive general result, and that several interesting questions remain about soil, climate and disturbance determinants across this biome boundary.

Ecodiagrams of common species of the forest herb layer in the Roztocze National Park

The paper presents in graphic standardised form ("ecodiagrams") the conditions in which 24 common species of the herb layer of forest communities occur in the Roztocze National Park. After determining the soil type, its mechanical composition, active and exchangeable acidity, humus content and the content in the rhizosphere layer of nutrient components essential for plants, such as P, K, Na, Ca. Mg. AI, ammonium nitrogen and nitrate nitrogen, the habitats of common plants of the forest from the class <em>Querco-Fagetea</em> were classified as meso-, eu-meso- and cutrophic. Forest plants connected with communities from the class <em>Vaccinio-Piceetea (Hierncium lachenalii</em> Gmel., <em>Melampyrum pratense</em> L., <em>Trientalis eurnpaea</em> L., <em>Vaccinium myrtillus</em> L.) are generally associated with fresh, moderately poor and quite frequently also mesotrophic soils. Only <em>Vaccinium vitis-idaea</em> L. is a local species of dry hungry soils, poor in mineral and organic components. The group of accompanying species such as <em>Fragaria vesca</em> L., <em>Galium vernum</em> Scop., <em>Luzula pilosa</em> (L.) Willd., <em>Mycelis ruralis</em> (L.) Dum. and <em>Oxalis ucetosella</em> L.. show a much wider ecological amplitude-from oligotrophic to eutrophic habitats.

A STUDY IN AN AREA OF TRANSITION BETWEEN SEASONALLY DRY TROPICAL FOREST AND MESOTROPHIC CERRADÃO, IN MATO GROSSO DO SUL, SOUTHWESTERN BRAZIL

This study describes the tree vegetation and soils occurring in a seasonally dry tropical forest (SDTF) and mesotrophic cerradão transition in southwestern Brazil. All trees ≥ 5 cm diameter were measured in 20 plots of 20 × 25 m, 10 in SDTF, and 10 in mesotrophic cerradão. Ten soil samples of 0−20 cm depth were made per plot and mixed in plot groups to produce two composite samples. A total of 71 species was recorded. Anadenanthera colubrina had the highest importance values in both formations. Differences in soil fertility were found between SDTFs (eutrophic soils) and mesotrophic cerradão (mesotrophic soils). A non-metric multidimensional scaling and cluster analysis confirmed the soil fertility segregation, and also showed an agreement between soil fertility and variance in species composition gradients. The mesotrophic cerradão showed higher species richness since it also includes many species typical of more dystrophic and open forms of Cerrado.

STRUCTURE AND FLORISTICS OF THE ARBOREAL COMPONENT OF A DYSTROPHIC CERRADÃO AND COMPARISON WITH OTHER CERRADÕES IN CENTRAL BRAZIL

This study describes the structure of the arboreal plant community in a cerradão fragment located at the Serra de Caldas Novas State Park, Goiás, central Brazil. It also compares the collected data with information from 10 other cerradão sites on dystrophic and mesotrophic soils. All trees of 4.77 cm or more diameter at breast height, in twenty-five 20 m × 20 m plots, were surveyed. Soil samples were analysed to determine the availability of nutrients. The vegetation had a discontinuous canopy, with a high density of small and medium-sized trees, and the soil was classified as dystrophic according to nutrient availability. Under ordination using Detrended Correspondence Analysis, species characteristic of the study site, such as Sclerolobium paniculatum and Emmotum nitens, were positioned in the central portion, while cosmopolitan species formed distinct groups, separated along the two axes. The community showed a low level of similarity in comparison to cerradões reported in the literature in other parts of Brazil, having more than 50% similarity only with three geographically close sites.

Large-scale habitat selection by parrots in New Caledonia

Habitat studies are important for conservation, particularly for parrots, as many are threatened and their ecological requirements are often poorly known. Our aim was to contribute to the conservation of parrots in New Caledonia by examining their selection of habitat at a large scale. From 2002 to 2010, we documented 1,357 encounters with New Caledonian Parakeets (Cyanoramphus saisseti), Horned Parakeets (Eunymphicus cornutus), and New Caledonian Rainbow Lorikeets (Trichoglossus haematodus deplanchii) throughout mainland New Caledonia. We used GIS to infer habitat selection in relation to vegetation, forest cover, forest size, altitude, rainfall, and soil. New Caledonian Parakeets selected forested areas with oligotrophic soils, particularly those from ultramafic substrates. Horned Parakeets selected habitats with a high proportion of rainforest, as well as oligotrophic soils on metamorphic substrates, yet soil fertility was less important for them. Both parakeet species favoured large forests, and appeared to avoid areas with low forest cover. Altitude had a relatively minor influence upon habitat selection by parakeets. Rainbow Lorikeets favoured areas at low altitudes with minimal rainfall and mesotrophic soils, although they were not influenced by soil fertility to the same degree as the parakeets. We consider rainforests on oligotrophic soils at intermediate altitudes (200–800 m) to be most important for parrot conservation in New Caledonia, as these habitats are likely to support significant parakeet populations.

P15 Maternal mortality due to arterial hypertension in São Paulo City (Brazil)

Relationships between seed germination response to plant-derived smoke and various plant traits (habitat requirements, life form, seed morphology, seed bank type) were analysed for 97 species of the Hungarian flora using published data. It was hypothesized that smoke-responsive species – those displaying enhanced germination in response to smoke – differ from non-responsive species – smoke having an indifferent or inhibitory effect on germination – in habitat requirements and/or certain life history traits. To our knowledge, no such comparison has previously been reported for a European flora. We found that species indicating disturbance and those preferring soils rich or moderately rich in nitrogen were more frequent in the smoke-responsive group (80% and 41%, respectively) than in the non-responsive group, while the non-responsive group contained a high percentage of natural species (i.e. species dominant or characteristic in natural plant communities; 47%) and species indicative of nutrient poor (38%) or (sub)mesotrophic (38%) soils. Annuals or biennials (67%) dominated the smoke-responsive group, whereas in the non-responsive group these short-lived species and perennial herbs were equally abundant (43% each). There was a tendency for higher frequency of long-term persistent seed bank among smoke-responsive species (78%) than in the non-responsive group (54%). These findings suggest that smoke-stimulated germination is associated with only a few specific plant traits for species from a semiarid temperate region of Europe, but highlight the frequent occurrence of smoke-enhanced germination among short-lived, nitrophilous or disturbance tolerant species. These results can contribute to a better understanding of post-fire regeneration of plant communities, and could also be considered during vegetation restoration or weed management.

P13 The recurrence risk of severe de novo preeclampsia in singleton pregnancies: a population-based cohort

Relationships between seed germination response to plant-derived smoke and various plant traits (habitat requirements, life form, seed morphology, seed bank type) were analysed for 97 species of the Hungarian flora using published data. It was hypothesized that smoke-responsive species – those displaying enhanced germination in response to smoke – differ from non-responsive species – smoke having an indifferent or inhibitory effect on germination – in habitat requirements and/or certain life history traits. To our knowledge, no such comparison has previously been reported for a European flora. We found that species indicating disturbance and those preferring soils rich or moderately rich in nitrogen were more frequent in the smoke-responsive group (80% and 41%, respectively) than in the non-responsive group, while the non-responsive group contained a high percentage of natural species (i.e. species dominant or characteristic in natural plant communities; 47%) and species indicative of nutrient poor (38%) or (sub)mesotrophic (38%) soils. Annuals or biennials (67%) dominated the smoke-responsive group, whereas in the non-responsive group these short-lived species and perennial herbs were equally abundant (43% each). There was a tendency for higher frequency of long-term persistent seed bank among smoke-responsive species (78%) than in the non-responsive group (54%). These findings suggest that smoke-stimulated germination is associated with only a few specific plant traits for species from a semiarid temperate region of Europe, but highlight the frequent occurrence of smoke-enhanced germination among short-lived, nitrophilous or disturbance tolerant species. These results can contribute to a better understanding of post-fire regeneration of plant communities, and could also be considered during vegetation restoration or weed management.

Cynosurion cristati grasslands in the central Apennines (Tyrrhenian sector): A phytosociological survey in the Lepini and Prenestini mountains

Cynosurion cristati grasslands are semi‐natural habitats that have developed on mesotrophic soils with a good water supply and are found from the basal up to the mountain vegetation belts. Differences between the various communities of these grasslands in the European continent have not been fully investigated; in Italy, there is a lack of knowledge of the mesophilous pastures in the central and southern Apennines. In order to shed light on the Cynosurion hay meadows and grasslands in the central Apennines, we considered phytosociological data from the Lepini and Prenestini mountains (central Italy, Tyrrhenian sector): 58 original relevés and a synoptic table containing similar associations throughout the Italian peninsula were analysed using multivariate methods (hierarchical classifications and principal coordinates analysis). Two new associations were distinguished: Hordeum bulbosum meadows, grazed after being mown (Trifolio molinerii–Hordeetum bulbosi), and heavily grazed, unmown pastures with several thorny species (Centaureo calcitrapae–Lolietum perennis). Both these associations have been assigned to Cynosurion cristati, though they differ from the European coenoses owing to the presence of Festuco‐Brometea and Helianthemetea guttati species. Further investigations are warranted to clarify the overall syntaxonomical position of the Italian coenoses in relation to the ecological and phytogeographic variations of Cynosurion, which are considered to be related to traditional land use in mountain agricultural systems. Hay meadows, which are important elements of landscape and biodiversity conservation, particularly feel the negative effects of land abandonment and land use change.

Variability of the Molinion meadows in Slovakia

Nine vegetation types were distinguished using cluster analysis within Molinion meadows in Slovakia. Vegetation of cluster 1 occurs on most acidic soils and is characterized by the occurrence of species of the Caricion fuscae alliance and of the Nardus grasslands. Vegetation of cluster 2 is also found on rather acidic soils but in contrast to cluster 1 vegetation it contains species of base-rich sites, such as Betonica officinalis, Galium boreale or Serratula tinctoria. Vegetation of cluster 3 occurs in wet base-rich habitats and often contains species of the Caricion davallianae alliance. Species of dry and Nardus grasslands are typical for vegetation of cluster 4, which is found at the driest sites and is confined to oligotrophic sandy soils. Vegetation of clusters 5 and 6 occurs on moist mesotrophic soils. Their species composition is quite similar, the main difference being that the former includes species-poor releves and the latter includes species-rich releves. Releves of cluster 7 include species of dry grasslands and some ruderal species and represent degraded types of inundated floodplain meadows of the Deschampsion alliance. Vegetation of clusters 8 is characterized by species of the Phragmito-Magnocaricetea class and of the Deschampsion alliance, and occurs in wet nutrient-rich habitats. Vegetation of cluster 9, which usually develops from vegetation of cluster 8 due to decrease in the ground-water table, often contains species of dry grasslands and mesic meadows. Except for releves of clusters 1 and 7, all others can be assigned to the Molinietum caeruleae Koch 1926 association. Cluster 1 corresponds to the Junco effusi-Molinietum caeruleae Tuxen 1954 association. Average Ellenberg indicator values for releves, which were passively projected on the ordination biplot of detrended correspondence analysis, showed that the first ordination axis correlates with nutrients, soil base status and temperature, and second axis with moisture.

Nutrient requirements of ephemeral plant species from wet, mesotrophic soils

Abstract. Nanocyperion plant communities occur on wet, more or less nutrient‐poor and sparsely vegetated soils in temperate climates and are characterized by tiny, very shortlived plant species. Most of these have become locally extinct. It is generally assumed that drainage and eutrophication were the most important reasons for this decrease. However, chemical analysis of soil pore water from plots on growth sites of these ephemerals showed that phosphorus availability was relatively high.In a greenhouse experiment, the growth of ephemeral species was strongly limited by the amount of available phosphorus, whereas there was little or no limitation to the growth of other plant species from this habitat. At low phosphorus concentrations, the ephemeral species reached their reproductive phase within the same period, but showed a strong reduction in the amount of flowers that were produced. We concluded that ephemeral species in particular require a minimum amount of phosphorus for reproduction. Other species on nutrient‐poor, wet soils have a longer life span and can postpone flowering in nutrient‐poor soils.In contrast to other short‐lived plant species from the same habitat, the growth of ephemeral species was barely stimulated by enhanced nitrogen availability. Apparently, the ephemerals are adapted to low nitrogen concentrations. The occurrence on nitrogen‐poor and relatively phosphorus‐rich soils suggests that this community may be very sensitive to nitrogen deposition. Reduced phosphorus availability below the minimum requirements of ephemerals, for example after acidification or the exclusion of human activities, has possibly contributed to the decrease of ephemeral plant species.

Enchytraeid communities in successional habitats (from meadow to forest)

The study was conducted in two successional series: natural on mesotrophic soils (a meadow, two birch woods and a mixed coniferous forest), and human-made on sandy soils (old field, birch plantation and pine forest). In both these series species richness and diversity of enchytraeid communities decreased with advancing succession. In the first two successional stages, enchytraeid communities showed a high degree of similarity (the meadow and 30-year-old birch thicket, ore the old field and 10-year-old birch plantation). Variation in soil in the same plant communities cause differences in animal communities. The abundance of enchytraeids varied from 14 to 51 × 103 m−2 individuals. In the majority of habitats C. sphagnetorum was the dominant species. Soil pH showed a positive correlation with species diversity and negative with number of C. sphagnetorum. The body size of this species was small at low pH (presumably as a result of frequent reproduction). It is suggested that the way of reproduction of the dominant species could confer a competitive advantage, thereby accounting for the simplification of enchytraeid communities in later stages of succession.

Recent Losses of Base Cations from Soils of Fagus sylvatica L. Stands in Northeastern France

Abstract In 1991, in order to assess changes in soil acidity, we resampled the mineral soil from 95 plots in beech forests distributed throughout northeastern France, ca. 20 years after a first sampling in 1970–1973. Changes between the two sampling dates were more conspicuous for acidic soils than for mesotrophic or calcareous soils. We observed a significant decrease in base saturation, exchangeable calcium, magnesium, and potassium in the whole profile of the acidic soils. Median cation losses calculated for these soils down to a depth of 80 cm were 18.7 kg ha−1 yr−1 for calcium, 2.7 kg ha−1 yr−1 for magnesium, and 2.4 kg ha−1 yr−1 for potassium. This loss was not reflected by changes in soil pH (measured in water extracts). The intensity of the cation losses and the analysis of the pollution climate over the last 20 years suggest that atmospheric deposition could have contributed to the observed changes.

The effects of air‐borne nitrogen pollutants on species diversity in natural and semi‐natural European vegetation

Summary The effects of increased atmospheric nitrogen inputs, from both NOy and NHx, on diversity in various semi‐natural and natural ecosystems are reviewed. The severity of these impacts depends on abiotic conditions (e.g. buffering capacity, soil nutrient status and soil factors that influence the nitrification potential and nitrogen immobilization rate) in the particular system. The sensitivity of fresh water ecosystems, wetlands and bogs, species‐rich grasslands, heathlands and field layer of forests, all of which have conservational value, are discussed in detail. The most important effects of nitrogen deposition are: (i) accumulation of nitrogenous compounds resulting in enhanced availability of nitrate or ammonium; (ii) soil‐mediated effects of acidification; and (iii) increased susceptibility to secondary stress factors. Long‐term nitrogen enrichment has gradually increased the availability of nitrogen in several vegetation types, leading to competitive exclusion of characteristic species by more nitrophilic plants, especially under oligo‐ to mesotrophic soil conditions. Soil acidification (with losses of buffering capacity and increased concentrations of toxic metals) is especially important after nitrification of ammonium in weakly buffered environments: acid‐resistant plant species then become dominant at the expense of the often rare plants typical of intermediate pH. The related change in the balance between ammonium and nitrate may also affect the performance of several species. The susceptibility of plant species to secondary stress factors (pathogens; frost and drought) may be affected by air‐borne nitrogen but data are only available for a few communities (e.g. dry heathlands). Most global biodiversity is contained within natural and semi‐natural vegetation. It is thus crucial to control emissions of nitrogenous compounds to the atmosphere, in order to reduce or prevent effects on diversity in these systems. Most research has focused on acidification in forestry stands and lakes and on the effects on trees. We highlight serious gaps in knowledge of other ecosystems.

Structure, composition and small litter dynamics of a semi-deciduous forest in Mato Grosso, Brazil

Structure, floristic composition, and the dynamics of small litterfall and the litter layer were studied for one year in semi-deciduous forest in Mato Grosso, Brazil. This vegetation type is rapidly disappearing as its mesotrophic soils are much in demand for agricultural development. The field site was located at 15°42′S, 56°06′W in the cerrado (savanna) region of the seasonal tropics not far from the southern limit of the Amazonian forest. The 0.25 ha study plot contained 236 trees with a dbh ≥5 cm and a maximum height of over 20 m. Stand basal area was 21.8 ± 2.0 m2 · ha−1. Tabebuia impetiginosa, Dipteryx alata, and Astronium urundeuva were dominant among the 35 recorded tree species from 20 families. Structure and floristics of the study site were similar to semi-deciduous forest found elsewhere in Mato Grosso. Total smalllitterfall was 7.7 ± 0.3 t · ha−1 · year−1. and fell within the range reported for semi-deciduous and deciduous tropical forests. Leaf litter made up over 68% and was five times higher in the dry season than in the wet season. Mean mass of small ground litter was 3.1 ± 0.4 t · ha−1 ranging from 1.6 ± 0.1 t to 6.1 ± 0.2 t · ha−1 for the wet and dry season, respectively. Seasonality of litterfall and decomposition of leaf litter was very high compared with published data.

Water-table changes and nutritional status affect trace gas emissions from laboratory columns of peatland soils

Peatlands potentially play a significant role in the global emission of three trace gases: carbon dioxide; methane; and nitrous oxide. We investigated the effect of a relatively small lowering of the water-table (10 cm) on the emission of these gases using repacked, root-free peat columns in the laboratory with peat from a nutrient-rich (eutrophic) site and a more nutrient-poor (mesotrophic) site, respectively. At a static high water-table (at the peat surface) high rates of anaerobic CO 2 production were found, which were reflected in high (> 1.18) molar ratios of CO 2 and CH 4. A static water-table of 10 cm below soil surface led to equal (eutrophic soil) or lower CO 2 emission (mesotrophic soil) compared with the high static water-table. However, at a regularly changing water-table (between 0 and 10 cm below the peat surface), CO 2 emission at a low water-table was 1.5 (mesotrophic soil) to 3 times (eutrophic soil) higher than at a high-water table. Maximum rates of CO 2 emission from the eutrophic soil exceeded those from the mesotrophic soil, except at a static high water-table. Methane emission was about one order of magnitude lower at a low static water-table compared with the static high water-table. There was no clear effect of the nutritional status of the peat on maximum methane emission in the various water-table treatments. The nutritional status of the peat had a profound influence on the effect of water-table lowering on N 2O emission: nitrous oxide emission from the eutrophic soil was strongly increased at a low water-table, whereas there was no detectable N 2O emission from the mesotrophic soil. Despite a clear effect of the water-table treatments on both trace gas emissions and on redox potentials in the soil, no significant correlation between these variables was found in either soil type.