Changes in forest soils and vegetation in Søgne, southern Norway, during a 20 year period

An investigation of the edaphic conditions and the vegetation of 21 fixed plots in Søgne municipality, Vest-Agder, South Norway was carried out in 1967-69 and 1987. Loss on ignition, pH, total nitrogen, total exchangeable bases, base saturation, exchangeable hydrogen, sodium, potassium, magnesium, calcium and manganese was analysed. The species composition of vascular plants was investigated. The total cover of the bottom layer was scored.
The soil pH had decreased in the more basic soils but had increased in the more acidic soils. The organic content had increased and base saturation had decreased in most samples. Na⁺ had increased in more than half of the plots, Ca²⁺ and Mg²⁺ had not changed, and K⁺ and Mn²⁺ had decreased in most plots. Salt depositions from the neighbouring North Sea and leaching from the soil accounted for these changes. In many of the parameters opposite changes were found in the poorer soils compared to the richer soils. In the field layer Deschampsia flexuosa, Convallaria majalis had increased, and Oxalis acetocella, Galium odoratum had decreased. The cover of cryptogams had decreased in most of the plots.     

Vegetation ordination at the southern Chihuahuan Desert (San Luis Potosi,Mexico)

Cover data for 93 perennial plant species from fifty 1 ha sites, were used to ordinate desert vegetation in relation to 50 environmental variables at El Huizache Corridor. Cumulative variance recovered in the Bray and Curtis variance-regression ordination was substantial (80%). Community structure of desert plant communities at El Huizache Corridor may be influenced primarily by a combination of landscape and edaphic variables, which in turn may determine the distribution and abundance of moisture and nutrients, and perhaps promote habitat specialization and or competitive exclusion. Secondly, to a lesser extent, climate variables could be influencing community organization at small scale gradients, the longer the gradient the more relevant climatic factors become. First axis represented a landscape gradient; it was positively correlated to exposure, geology, slope angle, rocks, stoniness, iron, January mean temperature, and organic matter content; it was negatively correlated with latitude, longitude, soil depth, and potassium content. The second axis represented mainly a climatic gradient; it was positively correlated with mean precipitation of January, February, July, August, September, November, December, annual mean precipitation, Lang's Index, organic matter content, and stoniness. The third axis represented an edaphic gradient; it was positively correlated with electrical conductivity, Mn, Zn and elevation, and negatively correlated with pH, nitrates, Ca, and disturbance. These findings should guide conservation efforts to maintain species diversity and endemism at this area. This revised version was published online in June 2006 with corrections to the Cover Date.     

Fine Root Distribution in a Lower Montane Rain Forest of Panama

In a Panamanian lower montane rain forest we: (1) analyzed the vertical and horizontal distribution of fine roots; and (2) assessed the relationship of fine root mass to thickness of the soil organic layer, soil pH, and soil-extractable nitrogen. The soil in the study area has developed on volcanic ash deposits and was classified as Hapludand. In randomly distributed samples, the median fine root mass (biomass and necromass, diam ≤ 2 mm) to a depth of 100 cm mineral soil was 544 g/m², 41 percent of which was found in the organic layer. Fine root mass was approximately twice as high in the vicinity of stems of the tree species Oreomunnea mexicana (1069 g/m²) and the palm species Colpothrinax aphanopetala (1169 g/m²) and was associated with thick organic layers. The median thickness of the soil organic layer in a larger random sample ( N = 64) was 8 cm with a considerable variation (interquartile range: 7 cm). In these samples, the density of fine root biomass was correlated with the concentration of extractable nitrogen ( r = 0.33, P = 0.011), and on an areal basis, fine root biomass in the organic layer increased with increasing thickness of the organic layer ( r = 0.63, P < 0.001) and decreasing pH_KCl ( r =−0.33, P < 0.01). Fine root biomass in the upper mineral soil did not show significant correlations with any of the studied parameters.     

Prediction of macrofungal occurrence in Swedish beech forests from soil and litter variable models

The spatial distribution of 49 macrofungal species in Swedish beech forests was related to the statistical variation in 31 edaphic variables. In order to reduce the multicollinearity problem, the variables were transformed into eight principal components, PCs, which are used in two-group discriminant analysis (on absence/presence patterns) and multiple regression analysis (on number of fruit-bodies). The results suggested that base saturation and organic matter content are of outstanding importance. However, significant relationships were also found with other variables, i.e. Cd or Zn in soil and litter, soil nitrogen mineralization rate, and Na or S in litter. One interesting interpretation of the results is that fungi do not only respond to the main variables of a gradient (soil pH, organic mater, base saturation) but also to other variables. Attempts were made to interpret the PCs to characterize fungal occurrence from the models they formed.     

Nitrification and nitrous oxide production potentials in aerobic soil samples from the soil profile of a Finnish coniferous site receiving high ammonium deposition

Abstract Using aerobic soil slurry technique nitrification and nitrous oxide production were studied in samples from a pine site in Western Finland. The site received atmospheric ammonium deposition of 7–33 kg N ha⁻¹ a⁻¹ from a mink farm. The experiments with soil slurries showed that the nitrification potential in the litter layer was higher at pH 6 than at pH 4. However, the nitrification potentials in the samples from the organic and mineral horizons at pH 6 and 4 were almost equal. Also N₂O was produced at a higher rate at pH 6 than at pH 4 in slurries of the litter layer samples. The reverse was true for samples from the organic and mineral horizons. The highest N₂O production and nitrification rates were measured in the suspensions of litter layer samples. Nitrification activity in field-moist soil samples was lower than the activity in the slurries indicating that the availability of ammonium limited nitrification in these soils. Acetylene (2.5 kPa) retarded nitrification activity (70-–100%) and N₂O production (40 – 90%) in soil slurries. Acetylene inhibited the N₂O production by 40–60% during the first 3 days after its addition to field-moist samples incubated in aerobic atmosphere. After 3 days the inhibition became much lower (4–5%). The results indicate that, in soil profiles of boreal coniferous forests receiving ammonium deposition, chemolithotrophic nitrification may have importance in the N₂O production, and that changes in soil pH affect differently nitrification as well as N₂O production in litter and deeper soil layers.     

The vegetation of the Farasān Islands,Red Sea,Saudi Arabia

Abstract. Classification of the vegetation of the Farasān Islands using TWINSPAN technique resulted in the recognition of seven community types associated with seven different habitat types: silty runnels, palm orchards, rocky plains, rocky plateau crevices, coastal sand dunes, sand plains, and mangroves. These communities were dominated or co-dominated by 13 perennial species; 87 associate species were recorded in the study area with chamaephytes dominating the life-form spectrum. Canonical Correspondence Analysis (CCA) indicated that organic carbon, soil moisture, silt, electrical conductivity and calcium carbonate were the major edaphic gradients controlling the distribution of the plant communities on the Farasān Islands. Higher species richness was recorded in the plant communities inhabiting the palm orchards, the crevices of the rocky plateau, silty runnels, rocky plains and rocky plateau, while those of the mangrove and sand formations (dunes and plains) showed a lower species richness. Soil texture and organic matter are the main factors promoting species diversity in the more diversified habitats, while high salinity and calcium carbonate are the main factors associated with lower species diversity in the less diversified habitats of the study area.     

Soil pH and organic matter content add explanatory power to Northern Lapwing Vanellus vanellus distribution models and suggest soil amendment as a conservation measure on upland farmland

Habitat associations of farmland birds are well studied, yet few have considered relationships between species distribution and soil properties. Charadriiform waders (shorebirds) depend upon penetrable soils, rich in invertebrate prey. Many species, such as the Northern Lapwing Vanellus vanellus, have undergone severe declines across Europe, despite being targeted by agri‐environment measures. This study assessed whether there were additive effects of soil variables (depth, pH and organic matter content) in explaining Lapwing distribution, after controlling for known habitat relationships, at 89 farmland sites across Scotland. The addition of these soil variables and their association with elevation improved model fit by 55%, in comparison with models containing only previously established habitat relationships. Lapwing density was greatest at sites at higher elevation, but only those with less peaty and less acidic soil. Lapwing distribution is being constrained between intensively managed lowland farmland with favourable soil conditions and upland sites where lower management intensity favours Lapwings but edaphic conditions limit their distribution. Trials of soil amendments such as liming are needed on higher elevation grassland sites to test whether they could contribute to conservation management for breeding Lapwings and other species of conservation concern that depend upon soil‐dwelling invertebrates in grassland soils, such as Eurasian Curlew Numenius arquata, Common Starling Sturnus vulgaris and Ring Ouzel Turdus torquatus. Results from such trials could support improvement and targeting of agri‐environment schemes and other conservation measures in upland grassland systems.     

Isotopic evidence for the provenance and turnover of organic carbon by soil microorganisms in the Antarctic dry valleys

The extremely cold and arid Antarctic dry valleys are one of the most environmentally harsh terrestrial ecosystems supporting organisms in which the biogeochemical transformations of carbon are exclusively driven by microorganisms. The natural abundance of ¹³C and ¹⁵N in source organic materials and soils have been examined to obtain evidence for the provenance of the soil organic matter and the C loss as CO₂ during extended incubation (approximately 1200 days at 10°C under moist conditions) has been used to determine the potential decay of soil organic C. The organic matter in soils remote from sources of liquid water or where lacustrine productivity was low had isotope signatures characteristic of endolithic (lichen) sources, whereas at more sheltered and productive sites, the organic matter in the soils that was a mixture mainly lacustrine detritus and moss-derived organic matter. Soil organic C declined by up to 42% during extended incubation under laboratory conditions (equivalent to 50–73 years in the field on a thermal time basis), indicating relatively fast turnover, consistent with previous studies indicating mean residence times for soil organic C in dry valley soils in the range 52–123 years and also with recent inputs of relatively labile source materials.     

Simulation of nitrogen assimilation by heterotrophic soil microbial biomass

Assimilation of N by heterotrophic soil microbial biomass is associated with decomposition of organic matter in the soil. The form of N assimilated can be either low molecular weight organic N released from the breakdown of organic matter (direct assimilation), or NH⁺₄ and NO⁻₃ from the soil inorganic N pool, into which mineralized organic N is released (mineralization immobilization turnover). The kinetics of C and N turnover in soil is quantifiable by means of computer simulation models. NCSOIL was constructed to represent the two assimilation schemes. The rate of N assimilation depends on the rate of C assimilation and microbial C/N ratio, thereby rendering it independent of the assimilation scheme. However, if any of the N forms is labeled, a different amount of labeled N assimilation will be simulated by the different schemes. Experimental data on inorganic N and ¹⁵N and on organic ¹⁵N dynamics in soils incubated with ¹⁵N added as NH⁺₄ or organic N were compared with data simulated by different model schemes. Direct assimilation could not account for the amount of ¹⁵N assimilated in any of the experimental treatments. The best fit of the model to experimental data was obtained for the mineralization immobilization turnover scheme when both NH⁺₄ and NO⁻₃ were assimilated, in proportion to their concentration in the soil.     

Testing patterns of zonation in mangroves: scale dependence and environmental correlates in the Sundarbans of Bangladesh

Summary 1  Associations between abiotic variables and patterns of species distribution and abundance are a major preoccupation of community ecologists. In many habitats, this association is manifest in discrete zones of vegetation.
2  We used statistical methods to examine tree species distribution patterns in relatively undisturbed regions of the Sundarbans of Bangladesh. We tested the hypothesis that mangroves occur in discrete zones with respect to elevation. These data were gathered with explicit attention to local and regional differences in edaphic characteristics so that species-environment relationships could be analysed at several spatial scales.
3  Correlations were also assessed between mangrove species composition and edaphic variables that co-vary with elevation, i.e. salinity, field capacity, cation exchange capacity, percentage silt, and mangrove physiognomic category (slope, basin, levee and flat).
4  Quantitative statistical analysis using randomization techniques failed to detect species zonation along any of 33 individual 200-m transects, within 1-km² blocks, or within 1200-km² regions.
5  Canonical correspondence analysis relating edaphic variables to species distributions accounted for a total of only 24% of the variance in species composition.
6  Our data suggest that the absence of zonation in the Bangladesh Sundarbans reflects the underlying biology of the system and is not an artefact of long-term human disturbance.     

Soil chemistry and plant distributions in rock habitats of southern Sweden

The vascular plant flora of open land on superficial bedrock in southem Sweden (northwards to 59°N) is described and related to soil chemical properties. including soil acidity (pH), exchangeable Al, Ca, Fe, Mn, Mg, and phosphate, as well as to soil solution pH and concentrations of Al, Ca and Mg, and to the contents of soil organic matter, soil depth and bedrock types (sandstone, gneiss, granites, various dark igneous rocks and limestones). About 120 localities with totally 652 sites (4 m²) have been examined. Experimental evidence for the toxicity of acid soils and mineral nutrient deficiency of neutral and alkaline soils is related to field data. Hydrogen and Al ion toxicity in acid soils and low phosphate solubility in neutral - alkaline soils are identified as major factors limiting the field distributions of rock habitat plants. Some species (e.g., Rumex acetosella and Sedum telephium ) were limited by phosphate also in acid soils. The relative importance of H and Al ion concentrations to plant performance under variously acid soil conditions is discussed, and strong evidence is given for a decisive influence of Al ion toxicity on species diversity at pH-KCI > 4.5. The importance of grazing and former land use is considered briefly and the floristic differences between the western and the eastern half of the study area are discussed originating from differences in general distribution patterns of species and soil chemical properties.     

Effects of Nitrogen Deposition: Results of a Temporal-Spatial Analysis of Deciduous Forests in South Sweden

Abstract: We studied permanent plots in deciduous forests in two provinces of South Sweden, Skåne (127 plots) and Småland (116 plots). Vegetation data were sampled in 1983 and 1993 and used to calculate weighted averages of Ellenberg indicator values for light, reaction (pH) and nitrogen. Soil samples were collected from all plots in 1993 for determination of pH, organic matter content and potential net nitrogen mineralization (minN). Data on minN were also available for 66 plots in Skåne from 1983. Nitrogen deposition is considerably higher in Skåne than in Småland. The same holds true for total minN, minNH₄⁺, minNO₃^-_-, and the proportion of total minN due to nitrate (nitrification ratio). According to the comparison of average Ellenberg indicator values between 1983 and 1993, the stands had become darker (not in the heavily managed plots), more acid and nitrogen rich, except at the most acid sites where only minor changes could be observed. The nitrification ratio was significantly higher in 1993 than in 1983. Mean soil nitrification ratios were determined for the most common species in both regions. The means were higher in Skåne than in Småland. It is likely that nitrogen deposition causes an increase in nitrification rate and nitrification ratio. This ratio is a significant determinant of the species composition in deciduous forests.     

In vitro studies on sulphate reduction and acidification in sediments of shallow soft water lakes

SUMMARY. 1. The sulphate reduction capacity of six shallow soft water sediments, differing in pH and organic matter content, was studied under controlled pH adjustments ranging from pH 3 to pH 8.
2. In the acid sediments, relatively rich in organic matter, the sulphate reduction capacity reached values of 0.09-0.12 μmol g⁻¹ d⁻¹. In the circumneutral mineral sediments the values ranged between 0.04 and 0.08 μmol g⁻¹ d⁻¹.
3. The latter group of sediments was very sensitive to the effects of experimental acidification as sulphate reduction was almost fully inhibited when pH decreased from 7 to 5. In the acid sediments inhibition occurred at lower pH values, in the range pH 5 to pH 3.
4. Sulphate reduction governed the production of free sulphides, whereas putrefaction processes were only of minor importance. It is suggested that in acid sediments, relatively rich in organic matter, the sulphate reducing bacterial population is less sensitive to acidification than in circumneutral mineral sediments.
5. The presence of organic matter appeared to be important in counteracting the inhibiting effects of acidification on sulphate reduction. This is important for the in situ sulphate reduction in sediments of soft waters which become enriched with organic matter during the long-term process of acidification.     

Multivariate approach to the classification and ordination of the forest ecosystem of Nandiar valley western Himalayas

QuestionsDoes the vegetation composition of the forests of Nandiar Valley correlate with climatic, topographic and edaphic variables? Is it possible to identify plant communities through indicator species in relation to environmental gradients? Can this approach of classification and ordination will be helpful for conservation planning?LocationForests of Nandiar Valley, Moist temperate Western Himalayas Pakistan.MethodsEighty stands were selected for quantitative and qualitative characteristic of vegetation between an elevations of 525–3817 m. Species composition was recorded by using 400 m long transects. GPS, climatic, edaphic and topographic data were recorded for each sampling site. The relationship between habitat types, species composition and distribution along with climatic, edaphic and topographic variables were analyzed using TWINSPAN, Cluster analysis and DCA ordination.ResultsSum 325 vascular plants species belonging to 97 families were recorded. Diversity index and species richness was maximum in the moist temperate zone. Classification and ordination showed that the variance in species data was 7.07. Two-ways indicator species analysis classified the vegetation into eight plant communities. Indicator species analysis revealed that slope aspect, wind speed, temperature, dew point, wet bulb, pH, organic matter and phosphorous were the strongest parameters (p ≤ 0.05) determining plant community composition and indicator species in each habitat. The results also show the strength of the environment – species relationship using Monte Carlo procedures. DCA ordination grouped different species having similar habitat and habitats having common species.ConclusionsThe multivariate analysis of the vegetation along with environmental variables of Nandiar valley confirmed the indicators of each sort of vegetation communities/microclimatic zones which could further be used in conservation planning and management not only in studied area but also in the adjacent regions as well as in the areas exhibit similar sort of climatic, edaphic and topographic conditions.     

Numerical abundance of myxomycetes (myxogastrids) in soils in the West of England

Abstract A most-probable-number technique was used to quantify the abundance of myxomycetes (myxogastrids) in soil samples taken from 23 'Sites of Special Scientific Interest' and one other site in the West of England. Associated organisms and soil conditions were also recorded. Sixteen of the 24 sites yielded myxomycete plasmodium-forming units (PFUs) in numbers averaging 230 cm⁻³ fresh soil. Where detectable in samples of grassland soil, the numbers ranged from 20–2750 cm⁻³, in woodland soil from 20–800 cm⁻³, and in sand dunes from 80–400 cm⁻³. Repeated sampling revealed changing numbers at single sites. The abundance of PFUs was correlated positively with numbers of soil amoebae, ciliates and nematodes, and with levels of magnesium and soil density, and negatively with organic matter content and levels of NH₄-nitrogen and phosphate. Each PFU probably corresponded to one or several uninucleate cells in the soil rather than to a plasmodium.     

Edaphic adaptation maintains the coexistence of two cryptic species on serpentine soils

? Premise of the study: Divergent edaphic adaptation can contribute to reproductive isolation and coexistence between closely related species, yet we know little about how small-scale continuous edaphic gradients contribute to this phenomenon. We investigated edaphic adaptation between two cryptic species of California wildflower, Lasthenia californica and L. gracilis (Asteraceae), which grow in close parapatry on serpentine soil. ? Methods: We reciprocally transplanted both species into the center of each species' habitat and the transition zone between species. We quantified multiple components of fitness and used aster models to predict fitness based on environmental variables. We sampled soil across the ridge throughout the growing season to document edaphic changes through time. We sampled naturally germinating seedlings to determine whether there was dispersal into the adjacent habitat and to help pinpoint the timing of any selection against migrants. ? Key results: We documented within-serpentine adaptation contributing to habitat isolation between close relatives. Both species were adapted to the edaphic conditions in their native region and suffered fitness trade-offs when moved outside that region. However, observed fitness values did not perfectly match those predicted by edaphic variables alone, indicating that other factors, such as competition, also contributed to plant fitness. Soil water content and concentrations of calcium, magnesium, sodium, and potassium were likely drivers of differential fitness. Plants either had limited dispersal ability or migrants experienced early-season mortality outside their native region. ? Conclusions: Demonstrating that continuous habitats can support differently adapted, yet closely related, taxa is important to a broader understanding of how species are generated and maintained in nature.     

Microbial transformation of labile dissolved organic matter into humic-like matter in seawater

Abstract Microbial transformation of labile, low molecular weight dissolved organic matter (DOM) into dissolved humic matter (DHM) was studied in seawater. Surface water samples were amended with [¹⁴C into ¹⁴CO₂, TO¹⁴C (total organic ¹⁴C), and PO¹⁴C (particulate organic ¹⁴C), was measured over time in confined samples. The humic and non-humic fractions of DO¹⁴C (dissolved organic ¹⁴C) were separated according to a common operational definition of DHM based on adsorption on XAD-8 macroporous resin. Both TO¹⁴C and non-humic DO¹⁴C decreased during the experiments. However, ¹⁴C-labelled DHM increased during the first week of the incubations, to a level where it comprised 15% of the TO¹⁴C remaining in the samples, or 3% of the initially added ¹⁴C. Towards the end of experiments (ca 70 days), the humic fraction of DO¹⁴C gradually approached the background level of poisoned control samples. Provided that the XAD-8 operational definition of DHM is accepted, this study indicates that humic matter may be formed in seawater within days from labile monomers such as glucose.     

Ecological Wood Anatomy of Avicennia marina

The soil physicochemical indexes including edaphic pH values, edaphic salinity and soil nutrient indexes were determined in 8 Avicennia marina populations located in national nature reserve of Shenzhen of Guangzhou Province. The morphological characters in secondary xylem of Amarina populations corresponding to soil sampling which represented different habitats were surveyed by means of light microscopy and electronic microscopy. Some common specialized wood structures in Amarina growing in different habitais can be observed which suggest they function as safely conducting water under high negative pressure and are thus adaptive to intertidal habitats．These characteristics include the occurrence of: (1) some fibriform vessel elements; (2) vessel vestures and helical structures on vessel walls; (3) parenchyma cells contain lots of starch grains;(4) included phloem. Soil organic matter and soil total salt have significant effect on quantitative wood anatomical features by the stepwise regression analysis.With the increase of soil salinity and soil organic matter content which suggest occurrence of more and more serious “physiological drought”, Amarina is characterized by a higher porosity.and double thickness of vessel wall making contact with an adjacent vessel. The trends inferred that variations in the quantitative wood anatomical features of Amarina growing at different sites are adaptive to heterogenous habitats in the intertidal areas.