Decomposition of beech leaves (Fagus sylvatica) and spruce needles (Picea abies) in pure and mixed stands of beech and spruce

The decomposition of spruce needles and beech leaves was investigated in a 30- and 120-yr-old beech, spruce and mixed (beech/spruce) forest using 1 mm mesh litterbags. The mass loss, content of C, N and water and microbial biomass, basal respiration and specific respiration of the litter materials were analyzed after exposure for 1.5, 3, 6, 9, 12, 18 and 24 months in the field. Decomposition of both types of litter was faster in beech than in spruce stands and after 24 months loss of C from litter materials was at a maximum in beech stands (>60%) and considerably less in the spruce and mixed stands (ca. 40%). Generally, spruce needles decomposed more rapidly than beech leaves, but the faster decay was not associated with higher N concentrations. Rather, N was accumulated more rapidly in beech leaves. Concomitantly, in beech stands microbial biomass of beech leaves exceeded that of spruce needles indicating that beech leaves consist of more favorable resources for microorganisms than spruce needles. Differences in decomposition between beech leaves and spruce needles were most pronounced in beech stands, intermediate in mixed stands and least pronounced in spruce stands. Decomposition, N content and microbial biomass in litter materials exposed in the 120-yr-old stand consistently exceeded that in the 30-yr-old stand indicating adverse conditions for litter decay in regrowing stands. Generally, mixed stands ranked intermediate between spruce and beech monocultures for most of the variables measured indicating that the adverse conditions for litter decay and microorganisms in spruce forest are effectively counteracted by admixture of beech to spruce monocultures. It is concluded that the accumulation of litter materials in spruce forests is not due to the recalcitrance of spruce needles to decay. Rather, adverse environmental conditions such as high polyphenol contents in the litter layer of spruce stands retard decomposition processes; spruce needles appear to be more sensitive to this retardation than beech leaves.     

Vertical distribution of Collembola (Hexapoda) and their food resources in organic horizons of beech forests

 Micro-samples of the surface organic horizons of 13 beech forests in Belgium were fixed immediately after collection in ethanol. Collembola (6255 animals) were sorted directly from micro-samples in the laboratory using a dissecting microscope, while the litter/soil matrix was analysed semi-quantitatively. The vertical distribution of Collembolan species was studied by correspondence analysis. Gut contents of animals were examined under a light microscope and their composition was compared with that of the matrix. A consistent association was found between the vertical distribution of gut contents and that of food resources in the immediate proximity of animals. Species differed in their feeding habits but most of them ingested a wide spectrum of food items. Plasticity in the food regime according to depth could be demonstrated in members of the Onychiuridae family. Received: 11 January 1999     

Microbial response to exudates in the rhizosphere of young beech trees (Fagus sylvatica L.) after dormancy

Plants act as an important link between atmosphere and soil: CO2 is transformed into carbohydrates by photosynthesis. These assimilates are distributed within the plant and translocated via roots into the rhizosphere and soil microorganisms. In this study, 3 year old European beech trees (Fagus sylvatica L.) were exposed after the chilling period to an enriched ¹³C–CO₂ atmosphere (δ¹³C = 60‰ – 80‰) at the time point when leaves development started. Temporal dynamics of assimilated carbon distribution in different plant parts, as well as into dissolved organic carbon and microbial communities in the rhizosphere and bulk soil have been investigated for a 20 days period. Photosynthetically fixed carbon could be traced into plant tissue, dissolved organic carbon and total microbial biomass, where it was utilized by different microbial communities. Due to carbon allocation into the rhizosphere, nutrient stress decreased; exudates were preferentially used by Gram-negative bacteria and (mycorrhizal) fungi, resulting in an enhanced growth. Other microorganisms, like Gram-positive bacteria and mainly micro eucaryotes benefited from the exudates via food web development. Overall our results indicate a fast turnover of exudates and the development of initial food web structures. Additionally a transport of assimilated carbon into bulk soil by (mycrorhizal) fungi was observed.     

Microhabitats of Collembola (Insecta: Entognatha) in beech and spruce forests and their influence on biodiversity

Collembolan communities were studied in 41 microhabitats in beech and spruce forests of south ( ofín and umava) and central (Jevany) Bohemia. The communities of Collembola were analysed using TWINSPAN and CANOCO programs. The aim of this study was to establish differences between patch (microhatitat) communities and the main forest community in spruce and beech forests, the differences between both types of forests and among different regions of Bohemia. Further questions were: is there a difference in microhabitat communities during secondary forest succession? do some species live exclusively in one or few microhabitats? and does microhabitat diversity influence the biodiversity in forest soils? Material comprising  25 590 specimens of Collembola belonging to 142 species was analysed. Highly significant differences were determined between microhabitat communities in beech and spruce forests, as well as among forests in different regions of Bohemia. Significant differences were also found among microhabitats in forests of different ages. Also, some microhabitat communities of Collembola, e.g. moss on boulders, were significantly different from their main forest community. Certain collembolan species existed exclusively in one or two microhabitats. Patches therefore influenced substantially biodiversity in these forest soils.     

Changes in enzyme activities of spruce (Picea balfouriana) forest soil as related to burning in the eastern Qinghai-Tibetan Plateau

The effect of forest fire on soil enzyme activity of spruce (Picea balfouriana) forest in the eastern Qinghai-Tibetan Plateau was assessed. Six specific enzymes were chosen for investigation: invertase, acid phosphatase, proteinase, catalase, peroxidase and polyphenoloxidase. It was found that the activities of invertase and proteinase were reduced by burning, but the activities of acid phosphatase, polyphenoloxidase and peroxidase increased. Meanwhile, burning significantly (P < 0.05) resulted in the decrease of concentrations of available N and K of 0–20 cm depth layer soil, and significantly (P < 0.05) decreased concentrations of organic matter content, total N and P, as well as available N, P and K in soil at both 20–40 and 40–60 cm depths except for available P at 20–40 cm soil depth. These results illustrated that burning could influence the enzyme activities and chemical properties of soil not only of upper but also lower soil layers. Correlation analysis indicated that invertase activities in 0–20 cm depth layer soil were significantly positively correlated with organic matter, total N and P, as well as available N and P. Furthermore, all six enzymes studied were sensitive to fire disturbance, and thus could be used as indicators of soil quality. Our study also showed that soil enzyme activities were associated with soil depth, decreasing from top to bottom in both burned and unburned spruce forests. The distribution pattern of soil enzyme activities suggested that the rate of organic matter decomposition and nutrient cycling depended on soil depth, which had important structural and functional characteristics in nutrient cycling dynamics and implications in plantation nutrient management. The finding that burning effects on enzyme activities and soil properties between different soil layers were homogenized was attributed to the 8-years’ regeneration of forest after burning.     

Carbon dioxide emissions of soils under pure and mixed stands of beech and spruce, affected by decomposing foliage litter mixtures

Soil respiration is the largest terrestrial source of CO₂ to the atmosphere. In forests, roughly half of the soil respiration is autotrophic (mainly root respiration) while the remainder is heterotrophic, originating from decomposition of soil organic matter. Decomposition is an important process for cycling of nutrients in forest ecosystems. Hence, tree species induced changes may have a great impact on atmospheric CO₂ concentrations. Since studies on the combined effects of beech-spruce mixtures are very rare, we firstly measured CO₂ emission rates in three adjacent stands of pure spruce (Picea abies), mixed spruce-beech and pure beech (Fagus sylvatica) on three base-rich sites (Flysch) and three base-poor sites (Molasse; yielding a total of 18 stands) during two summer periods using the closed chamber method. CO₂ emissions were higher on the well-aerated sandy soils on Molasse than on the clayey soils on Flysch, characterized by frequent water logging. Mean CO₂ effluxes increased from spruce (41) over the mixed (55) to the beech (59) stands on Molasse, while tree species effects were lower on Flysch (30-35, mixed > beech = spruce; all data in mg CO₂-C m⁻² h⁻¹). Secondly, we studied decomposition after fourfold litter manipulations at the 6 mixed species stands: the O_i - and O_e horizons were removed and replaced by additions of beech -, spruce - and mixed litter of the adjacent pure stands of known chemical quality and one zero addition (blank) in open rings (20 cm inner diameter), which were covered with meshes to exclude fresh litter fall. Mass loss within two years amounted to 61-68% on Flysch and 36-44% on Molasse, indicating non-additive mixed species effects (mixed litter showed highest mass loss). However, base cation release showed a linear response, increasing from the spruce - over the mixed - to the beech litter. The differences in N release (immobilization) resulted in a characteristic converging trend in C/N ratios for all litter compositions on both bedrocks during decomposition. In the summers 2006 and 2007 we measured CO₂ efflux from these manipulated areas (a closed chamber fits exactly over such a ring) as field indicator of the microbial activity. Net fluxes (subtracting the so-called blank values) are considered an indicator of litter induced changes only and increased on both bedrocks from the spruce - over the mixed - to the beech litter. According to these measurements, decomposing litter contributed between 22-32% (Flysch) and 11-28% (Molasse) to total soil respiration, strengthening its role within the global carbon cycle.     

Controls of temporal and spatial variability of methane uptake in soils of a temperate deciduous forest with different abundance of European beech (Fagus sylvatica L.)

Aerated forest soils are a significant sink for atmospheric methane (CH₄). Soil properties, local climate and tree species can affect the soil CH₄ sink. A two-year field study was conducted in a deciduous mixed forest in the Hainich National Park in Germany to quantify the sink strength of this forest for atmospheric CH₄ and to determine the key factors that control the seasonal, annual and spatial variability of CH₄ uptake by soils in this forest. Net exchange of CH₄ was measured using closed chambers on 18 plots in three stands exhibiting different beech (Fagus sylvatica L.) abundance and which differed in soil acidity, soil texture, and organic layer thickness. The annual CH₄ uptake ranged from 2.0 to 3.4 kg CH₄-C ha⁻¹. The variation of CH₄ uptake over time could be explained to a large extent (R² = 0.71, P < 0.001) by changes in soil moisture in the upper 5 cm of the mineral soil. Differences of the annual CH₄ uptake between sites were primarily caused by the spatial variability of the soil clay content at a depth of 0-5 cm (R² = 0.5, P < 0.01). The CH₄ uptake during the main growing period (May-September) increased considerably with decreasing precipitation rate. Low CH₄ uptake activity during winter was further reduced by periods with soil frost and snow cover. There was no evidence of a significant effect of soil acidity, soil nutrient availability, thickness of the humus layer or abundance of beech on net-CH₄ uptake in soils in this deciduous forest. The results show that detailed information on the spatial distribution of the clay content in the upper mineral soil is necessary for a reliable larger scale estimate of the CH₄ sink strength in this mixed deciduous forest. The results suggest that climate change will result in increasing CH₄ uptake rates in this region because of the trend to drier summers and warmer winters.     

The use of macrochaetotaxy in taxonomy of palaearctic Folsomia (Collembola, Isotomidae)

Data on the number of macrochaetae of the main segments (Th. II–Abd. IV) of the body in 76 species of Folsomia are summarised. Only thoracic tergites II—III show variation in number of macrochaetae, as the conditions 1,1, 2,2 and 1,2 were found in the material studied. The last variation was seen in three groups of species, and has probably been derived independently.     

Distribution and stand characteristics of relict populations of Mexican beech (Fagus grandifolia var. mexicana)

Fagus grandifolia var. mexicana (Mexican beech) is limited to about 10 populations (2-35 ha) in the Sierra Madre Oriental, Mexico. The objectives were to assess the current status and distribution of beech by surveying five sites. Species richness varied between three to 27 tree species in the canopy, and from nine to 29 species in the understorey. Basal area of trees?5 cm dbh varied between 27.87 and 70.98 m² ha⁻¹, and density from 370 to 1290 individual ha⁻¹. Beech represented 22-99.6% of total basal area, and 6.8-83.3% of total density. Beech dominance varied from monodominant to codominance with Carpinus caroliniana, Quercus spp., Liquidambar styraciflua, Magnolia schiedeana, and Podocarpus spp. Beech total population size ranged from 180 to 6300 trees with a total of less than 1300 individuals in four sites. Anthropogenic disturbance remains a major threat to these forests. It is uncertain whether Mexican beech will be able to survive without conservation efforts.     

Addition of coarse woody debris – The early fungal succession on Picea abies logs in managed forests and reserves

Modern forestry practices have decreased the abundance of coarse woody debris (CWD), and as a result many species that depend on dead wood are now threatened. This implies a need to develop forestry practices that maintain biodiversity. We examined the conservation value of experimental spruce logs (control logs, logs placed in natural shade, and cut tree tops) for wood-inhabiting fungi in two forest stands, one nature reserve and one mature managed forest, in each of seven forest areas in northern Sweden. Here we report the initial findings of the experiment that was established in winter 2001–2002 and data were collected in 2002, 2003 and 2006. A pre-inventory of the local species composition in 2002 revealed a higher per area species richness, including red-listed species, in reserves than in managed forests. Ordination analyses of the experimental logs showed a significant effect of area, while not of stand type in 2003. ANOVA analysis showed no significant effect of stand type on species richness and abundance. In 2006, the species assemblage started to differentiate between the two stand types and forest age, forest site type (moisture), and distance to forest reserves, all explained part of the variation, whereas the amount of CWD, and species composition at the start of the experiment only showed a marginal effect.The early successional fungal community was dominated by two functional groups, humus-decayers and white-rot species, both characterized by a rapid, early colonization and fruit-body formation on the competition-free new substrate. A similar positive response to the new substrate was also observed for the mycorrhizal species in 2006. The high frequency and early appearance of humus-decayers and mycorrhizal species that do not primarily depend upon CWD for their nutrition suggest that their formation of fruiting bodies is limited by substrate availability. Thus some mycorrhizal fungi are apparently rare due to lack of suitable substrate for fruit-body formation.Evidence of dispersal-limitation was observed in 2006. Fomitopsis pinicola, an early colonizer in boreal forests, playing a key role for other wood-inhabiting organisms, colonized significantly more logs in the reserve stands compared with the managed stands. Our data demonstrate that lack of CWD strongly affects both species that depend upon wood for nutrition and species that depend upon wood for fruit-body formation. Thus some species may show an apparent rarity due to lack of suitable substrate. We conclude that creation of CWD appears to be a useful method to maintain or restore fungal diversity in boreal coniferous forests.     

Fast and efficient discrimination of the Isotoma viridis group (Insecta: Collembola) by PCR-RFLP

Identification of collembolan species is generally based on specific morphological characters, such as chaetotaxy and pigmentation pattern. However, some specimens do not match to described characters because these refer to adult specimens, often of one specific sex, or the characters are highly variable in adults (e.g. pigmentation, setae or furcal teeth). Isozymes have frequently assisted species discrimination, and also these may vary with developmental stage or environmental conditions. For identification of single species of the Isotoma viridis group, we present both direct sequencing of the cytochrome oxidase subunit II (COII) gene and a simple DNA-based molecular method.

Five PCR primers amplifying the COII region (717 bp) of the mitochondrial DNA were used. The sequences clearly separated the species I. viridis, I. riparia and I. anglicana, irrespective of colour varieties within the first species. DNA amplification products of different species can also be distinguished by digestion with restriction endonucleases, followed by gel electrophoresis for separation of fragments. This restriction fragment length polymorphism (RFLP), obtained after digestion with the endonucleases TaqI, VspI, MvaI and Bsp143I, revealed specific fragments that separated the three species from each other. Since restriction enzymes are sensitive to single base mutations, we suggest to use a combination of enzymes with at least two species-specific restriction sites when using the RFLP technique. For the I. viridis complex, VspI and Bsp143I appear to be an appropriate combination.     

Seasonal distribution of Xenylla brevispina (Collembola) in the canopy and soil habitat of a Cryptomeria japonica plantation

We investigated the life cycle and habitat use of an arboreal collembolan species, Xenylla brevispina, in the canopy and soil of a conifer (Cryptomeria japonica D. Don) plantation. The adaptive significance of migration between arboreal and soil habitats in the maintenance of its population in relation to the vertical structure of the forest is discussed. We sampled dead branches with foliage in the canopy (canopy litter) and on the forest-floor (soil litter). X. brevispina had one generation a year throughout the 3 years of the study. The mean densities of X. brevispina were similar in the canopy litter (0.06 to 14.57 g⁻¹ dry weight) and the soil litter (0.44 to 18.99 g⁻¹ dry weight). Seasonal patterns of density and relative abundance indicate that individuals of X. brevispina in the canopy were closely associated with those in the soil. These results suggest that vertical migration between the canopy and the soil might be a strategy allowing X. brevispina to be a predominant collembolan species in this forest.     

Ecology of soil springtails (Collembola, Insecta) from pine woods and Rhododendron shrublands in the Central and Eastern Pyrenees (North Spain)

The collembological composition of samples from the Central and Western Pyrenees (Northern Spain) was studied. Soils from two biotopes (pine forest and Rhododendron shrub) were studied in Nuria and Vallibierna, using different diversity indices and multivariate analyses. Ten species were found that were endemic to the Iberian Peninsula. Three of these are exclusive to the Pyrenees: Ceratophysella elegans, Hypogastrura dasiensis and Protachorutes pyrenaeus. The greatest diversity was observed in the soils of Rhododendron, above all at Nuria. Collembola were most poorly represented in the pine forest of Vallibierna, where the endemic Hypogastrura meridionalis was the dominant species. Multivariate analyses indicated that the latter species characterizes this pine forest and separates it from all other biotopes studied. The evenness (E) was most pronounced in Nuria, where Folsomia manolachei was the characteristic species.     

Geographical barriers and ecological gradients: Geographical distribution of the subspecies and morphotypes of Deutonura deficiens Deharveng, 1979 (Collembola: Neanuridae)

This work explores the links between ecogeographical barriers and clines, and the boundaries of infraspecific biological entities. The distribution of the three subspecies and eight morphotypes of the Neanurinae Deutonura deficiens (Collembola) are mapped and commented based on 570 records. The species inhabits a wide range of forest habitats from the north of Portugal to southeastern France. The subspecies and morphotypes constitute homogeneous geographic sets arranged as a mosaic of closely related forms. A few overlapping zones between subspecies or morphotypes have been detected, some of them having the character of hybrid zones; on the whole however, overlap is small or rare and allopatry or parapatry is the general pattern. Current range boundaries of subspecies and morphotypes were found to be usually not determined by major hydrographical and topographical barriers, with the noticeable exception of the Rhône River. At subspecies level, the morphological cline of increasing tuberculization correlated to the bioclimatic gradient from Mediterranean to Atlantic climates, already recorded by Deharveng (1984. Polymorphisme et polytypisme morphologiques chez quelques Neanurinae européens. Rev. Ecol. Biol. Sol. 21, 533–562), is confirmed on the present data set. Conversely, ecological boundaries, known to constrain species distribution in many living groups of the region, do not fit the contact zones between the different morphotypes of the three subspecies of D. deficiens. The eight recognized forms appear to be at different degrees of reproductive isolation, illustrating active speciation process possibly inherited from recent ecogeographical events. A more detailed sampling on contact zones and a robust phylogenetic hypothesis are needed at this stage for progressing in our understanding of this complex pattern.     

Oribatid mite and collembolan diversity, density and community structure in a moder beech forest (Fagus sylvatica): effects of mechanical perturbations

The effects of mechanical perturbations on two soil microarthropod communities (oribatid mites and collembolans) were investigated in a moder beech forest on sandstone. We disturbed the soil matrix by sieving and mixing the litter and soil of the moder profile. The top litter layer (L material) and the deep mineral soil (Bv) remained intact. Three amounts of disturbance were established: a single perturbation, perturbations once every 2 months (60 d) and once every 2 weeks (14 d). Densities of most groups of oribatid mites and all groups of collembolans declined in the disturbance treatments. In most cases, densities were lowest in the strong perturbation treatment (14 d). Desmonomata were the only group of oribatid mites that benefited from intermediate amounts of disturbance but not from the strongest disturbance. Also, disturbances reduced diversity of oribatid mites and collembolans. According to their sensitivity to disturbances oribatid mites ranked Poronota=Enarthronota=Suctobelbidae (the most sensitive)>Oppiidae>Tectocepheus>Desmonomata. The ranking of collembolans was Folsomia (the most sensitive)>Hypogastruridae/Neanuridae>Onychiuridae=Isotomidae>Entomobryidae. Generally, tolerance of disturbance was wider for oribatid mites than for collembolans. The results indicate that disturbances such as mixing of litter and soil and comminution of litter material strongly affect the density and diversity of soil microarthropods. However, they also indicate that the soil microarthropod community is resistant to weaker disturbances. In the field, mechanical disturbances are often caused by burrowing of earthworms. Our results suggest that the high density of microarthropods in moder soils may be due to the low intensities of mechanical disturbances by earthworms.     

Molecular phylogeny of three subfamilies of the Neanuridae (Insecta, Collembola) and the position of the antarctic species Friesea grisea Schäffer.

The nuclear 28S rRNA and the mitochondrial COII gene were used to establish phylogenetic relationships among species of the family Neanuridae, with special emphasis on species of the subfamily Neanurinae. Phylogenetic analysis was conducted using genetic distances, parsimony and likelihood methods. The D3-D5 fragment of the rRNA gene was very conserved, both in sequence and in secondary structure features. This fragment supplied little information on relationships at this level. The phylogenetic reconstruction based on 1st and 2nd codon positions of the COII gene was partly in accordance with morphological data, but it was discordant for the placement of some species. Relationships among the subfamilies Frieseinae, represented by the Antarctic species Friesea grisea, Pseudachorutinae and Neanurinae were uncertain. The subfamily Neanurinae and its tribes Neanurini and Paleonurini were shown as monophyletic taxa. Relationships between three species of the genus Bilobella were in accordance with morphological and biochemical data. Relationships between genera within the Neanurini were more controversial. In accordance with morphological hypotheses, a basal position of Thaumanura was suggested, but the molecular data placed Neanura muscorum in a derived position, in sharp contrast with morphological evidence. A close relationship was suggested between Deutonura conjuncta, Cansilianura malatestai and Lathriopyga longiseta. The disagreement between molecular and morphological data suggests that one or both data sets might be affected by a certain degree of homoplasy and that these data should be interpreted with caution in phylogenetic reconstructions.     

Improvement of earthworm (Lumbricidae) community and activity in mine soils from open-cast coal mining by the application of different organic waste materials

Earthworms are important members of the decomposer food web in a wide range of sites. Previous field investigations on the development of earthworm populations of mine soils in the Lusatian coal mining region, Germany, have shown quite small population densities in quaternary sands and less or even no earthworms present in sandy soils derived from tertiary deposits. The aim of the present investigation was to improve the development of earthworm populations in mine soils from tertiary deposits by applying various types and amounts of organic waste residues, such as sewage sludge, composted sewage sludge, and green waste derived compost. Additionally, we were interested in the stimulation effect of organic waste materials on parameters of earthworm activity, such as food consumption and burrowing activity. The investigations were carried out in field mesocosms and laboratory experiments (microcosms; observation cages). In general, the population density, fresh biomass, food consumption, and the burrowing activity of earthworms were significantly improved by the application of the various organic waste materials compared with mineral fertilizers. Fresh sewage sludge in addition to composted sewage sludge were found to be the most favourable organic waste residues compared with green waste derived composts. The addition of brown coal sludge to sewage sludge did not reduced the stimulation effect. There was considerable variation in the population structure of a defined earthworm community which was exposed in the mesocosms during a two year period in relation to the types and amounts of the organic waste materials applied.