Significant and persistent impact of timber harvesting on soil microbial communities in Northern coniferous forests

Forest ecosystems have integral roles in climate stability, biodiversity and economic development. Soil stewardship is essential for sustainable forest management. Organic matter (OM) removal and soil compaction are key disturbances associated with forest harvesting, but their impacts on forest ecosystems are not well understood. Because microbiological processes regulate soil ecology and biogeochemistry, microbial community structure might serve as indicator of forest ecosystem status, revealing changes in nutrient and energy flow patterns before they have irreversible effects on long-term soil productivity. We applied massively parallel pyrosequencing of over 4.6 million ribosomal marker sequences to assess the impact of OM removal and soil compaction on bacterial and fungal communities in a field experiment replicated at six forest sites in British Columbia, Canada. More than a decade after harvesting, diversity and structure of soil bacterial and fungal communities remained significantly altered by harvesting disturbances, with individual taxonomic groups responding differentially to varied levels of the disturbances. Plant symbionts, like ectomycorrhizal fungi, and saprobic taxa, such as ascomycetes and actinomycetes, were among the most sensitive to harvesting disturbances. Given their significant ecological roles in forest development, the fate of these taxa might be critical for sustainability of forest ecosystems. Although abundant bacterial populations were ubiquitous, abundant fungal populations often revealed a patchy distribution, consistent with their higher sensitivity to the examined soil disturbances. These results establish a comprehensive inventory of bacterial and fungal community composition in northern coniferous forests and demonstrate the long-term response of their structure to key disturbances associated with forest harvesting.     

Spatial and typological structure and organization of bird communities in the Lower Amur region

Exemplified by the Lower Amur region, the bird distribution over various habitats from undisturbed to urban ones is described on the basis of the results of long-term investigations. The trends of territorial changes in overall characteristics of bird complexes are established. The spatial-typological structure of bird complexes and the main structure-forming environmental factors are revealed, and their role in the organization of bird communities in the Lower Amur Region is estimated.     

Stream meanders increase insectivorous bird abundance in riparian deciduous forests

Adult aquatic insects emerging from streams are a fundamental resource sustaining riparian bird communities in broad-leaved deciduous forests. We investigated how stream geomorphology affects the aquatic insect flux and insectivorous bird abundance in 26 riparian-forest plots during spring season in northern Japan. Lateral dispersal of emergent aquatic insects into the riparian forest exponentially decreased with distance from the stream. Similar to aquatic insect distribution, flycatchers and gleaners concentrated their foraging attacks around the stream channel, preying intensively upon emergent aquatic insects. In contrast, bark probers consumed fewer emergent aquatic insects. The abundance of flycatchers and gleaners was closely related to stream geomorphology, whereas that of bark probers was associated with snag density in the study plots. A path analysis showed that the study plots with longer stream channels had greater aquatic insect abundance. This can be interpreted as a consequence of the increased amount of both stream edge and stream surface, where emergent aquatic insects readily penetrate. The increased flux of aquatic insects by stream meanders elevated gleaner abundance in the study plots. In addition, their abundance was directly affected by stream length per se. On the other hand, flycatcher abundance was only directly affected by stream length. Flycatchers, which mainly consumed emergent aquatic insects in the air, may have increased in response to the increase in suitable foraging sites (i.e., open spaces adjacent to perches) accompanying longer stream channels. Although the causal links affecting bird abundance differed among guilds, meandering streams apparently support abundant insectivorous birds in riparian forests. Therefore, to conserve riparian bird communities, it will be necessary to maintain the functions of stream geomorphology that affect the magnitude of energy transfer across the forest-stream interface.     

Ants of Central Altai: Spatial-typological structure and classification of communities

The basic features of spatial differentiation of ant communities were studied based on quantitative counts in all the landscapes of Central Altai. Gradual changes in the structure of ant communities on altitudinal belts were observed, as well as the mosaic patterns of the complexes determined by the variations in meso- and microclimatic conditions within the belt. The main trends in the correlated changes of ant communities and environmental factors were revealed. Classification of ant communities which may form the basis for the legend of a medium-scale map was made using multidimensional factor analysis. The specific features of the spatial differentiation of ant communities in Central Altai, as well as those in Northeast Altai studied earlier, are largely determined by fluctuations in the hydrothermal conditions of these regions. Among the anthropogenic factors, the most significant one in both provinces is transformation of habitats caused by plowing, stocking, annual mowing, and construction.     

浙江天童常绿阔叶林、常绿针叶林与落叶阔叶林的C:N:P化学计量特征

以浙江天童常绿阔叶林、常绿针叶林和落叶阔叶林为对象, 通过对叶片和凋落物C:N:P比率与N、P重吸收的研究, 揭示3种植被类型N、P养分限制和N、P重吸收的内在联系。结果显示: 1)叶片C:N:P在常绿阔叶林为758:18:1, 在常绿针叶林为678:14:1, 在落叶阔叶林为338:11:1; 凋落物C:N:P在常绿阔叶林为777:13:1, 常绿针叶林为691:14:1, 落叶阔叶林为567:14:1; 2)常绿阔叶林和常绿针叶林叶片与凋落物C:N均显著高于落叶阔叶林; 叶片C:P在常绿阔叶林最高, 常绿针叶林中等, 落叶阔叶林最低, 常绿阔叶林和常绿针叶林凋落物C:P显著高于落叶阔叶林; 叶片N:P比也是常绿阔叶林最高、常绿针叶林次之, 落叶阔叶林最低, 但常绿阔叶林凋落物N:P最低; 3)植被叶片N、P含量间(N为x, P为y)的II类线性回归斜率显著大于1 (p < 0.05), 表明叶片P含量的增加可显著提高叶片N含量; 凋落物N、P含量的回归斜率约等于1, 反映了凋落物中单位P含量与单位N含量间的等速损耗关系; 4)常绿阔叶林N重吸收率显著高于常绿针叶林与落叶阔叶林, 落叶阔叶林P重吸收率显著高于常绿阔叶林和常绿针叶林。虽然植被的N:P指示常绿阔叶林受P限制, 落叶阔叶林受N限制, 常绿针叶林受N、P的共同限制, 但是N、P重吸收研究结果表明: 受N素限制的常绿阔叶林具有高的N重吸收率, 受P限制的落叶阔叶林并不具有高的P重吸收率。可见, 较高的N、P养分转移率可能不是植物对N、P养分胁迫的一种重要适应机制, 是物种固有的特征。     

Spatio-temporal organization of the bird communities in two Mediterranean montane forests

Seasonal changes of bird communities and use of foraging substrates by the birds were studied in two forests with contrasting vegetation structure in montane and subalpine levels of central Spanish mountains throughout complete annual cycles. Common factors contributing most to foraging segregation among species were found to be the foraging on the ground vs that on vegetation and use of proximal vs distal tree parts. A complete dissimilarity exists between the composition of the respective foliage-gleaning guilds, the converse being true for the trunk-searchers.
Temporal distribution of bird species is to a great extent determined by their use of space, thus existing a gradient of seasonality with maxima for ground-searchers, minima for trunk-gleaners and intermediate positions for foliage-gleaners. A close relationship among temporal variability, mean annual density and niche breadth is found for the subalpine pinewood community, but not for that from the montane oakwood, this being related with their contrasting migratory patterns and the structural stability of vegetation in each wood. The pattern of covariation in community parameters mirrors the summed response of individual bird species to the changing environmental conditions. Increases in community richness, density and diversity are related to temporal invasion by ground and foliage-gleaners of these highly seasonal Mediterranean habitats.     

Insect herbivores and the nutrient flow from the canopy to the soil in coniferous and deciduous forests

Phytophagous insects can have severe impacts on forested ecosystems in outbreak situations but their contribution to flows of energy and matter is otherwise not so well known. Identifying the role of phytophagous insects in forested ecosystems is partly hindered by the difficulty of combining results from population and community ecology with those from ecosystem ecology. In our study we compared the effects of aphids and leaf-feeding lepidopterous larvae on the epiphytic micro-organisms in the canopies of spruce, beech and oak, and on the vertical flow of energy and nutrients from the canopies down to the forest floor. We particularly searched for patterns resulting from endemic herbivory rather than outbreak situations. Excreta of lepidopterous larvae and aphids promoted the growth of epiphytic micro-organisms (bacteria, yeasts, filamentous fungi) on needles and leaves, which suggests that micro-organisms were energy limited. Leachates from needles and leaves of infested trees contained higher concentrations of dissolved organic C and lower concentrations of NH₄-N and NO₃-N, relative to uninfested trees. The seasonal abundance of herbivores and micro-organisms significantly affected the dynamics of throughfall chemistry; for instance, concentrations of inorganic N were lower underneath infested than uninfested trees during June and July. There was little difference between the chemistry of soil solutions collected from the forest floor beneath infested and uninfested trees. Thus, under moderate to low levels of infestation the effects of above-ground herbivory seems to be obscured in the soil through buffering biological processes.     

Mechanisms regulating bird predation on a herbivorous Larva guild in boreal coniferous forests

Bird predation was previously found to considerably reduce the abundance of the herbivorous insect larva guild feeding on bilberry Vacanium myrtillus within boreal coniferous forests In this follow-up study, interest was focused on determining whether female pied flycatchers Ficedula hypoleuca tend to use the field layer more frequently than other types of feeding niches In addition, the degree to which the conspicuousness of a larva increases the risk of its being preyed upon by birds was evaluated in order to further understand the mechanisms regulating the bird predation effect Larval predation risks were measured by presenting larvae with contrasting characteristics to seven captured female flycatchers
Female flycatchers hunted more frequently in the tree and field layers than in the air However, the relative degree of utilization of the tree and field layer varied considerably between years, with use of field layer being positively related to the abundance of insect larvae on bilberry
Large larvae did not suffer higher bird predation than small larvae when both size classes were presented to the birds on bilberry Larvae that crawl on leaves and stems during feeding (high degree of exposure) were preyed upon more than larvae that feed between leaves they have spun together (low degree of exposure) No difference in larval predation risk was found between sawflies and geometrids, the two taxa represented in the exposed feeder group However, dark geometrids suffered higher predation than green sawflies and green geometrids
My findings suggest that the herbivorous larva guild constitutes an abundant food resource frequently utilized by small bird predators However, certain members of the guild appeared to be preyed upon more than other members Thus the risk for predation seems to be highest for dark geometnds followed in decreasing order by green geometrids. sawflies pyralids, and tortricids     

Simulation and scaling of temporal variation in gross primary production for coniferous and deciduous temperate forests

Observations of ecosystem net carbon dioxide exchange obtained with eddy covariance techniques over a 4‐year period at spruce, beech and pine forest sites were used to derive time series data for gross primary production (GPP) and ecosystem respiration (R_eco). A detailed canopy gas exchange model (PROXEL_NEE) was inverted at half‐hour time step to estimate seasonal changes in carboxylation capacity and light utilization efficiency of the forest canopies. The parameter estimates were then used further to develop a time‐dependent modifier of physiological activity in the daily time step gas exchange model of Chen et al. (1999) , previously used for regional simulations in BOREAS. The daily model was run under a variety of assumptions and the results emphasize the need in future analyses: (1) to focus on time‐dependent seasonal changes in canopy physiology as well as in leaf area index, (2) to compare time courses of physiological change in different habitats in terms of recognizable cardinal points in the seasonal course, and (3) to develop methods for utilizing information on seasonal changes in physiology in regional and continental carbon budget simulations. The results suggest that the daily model with appropriate seasonal adjustments for physiological process regulation should be an efficient tool for use in conjunction with remote sensing for regional evaluation of global change scenarios.     

Spatial-typological differentiation of clavarioid mycobiota in Northern Eurasia

The spatial heterogeneity of mycobiota species composition has been studied. Clavarioid fungi are used as a model group for mycobiota zonation of Northern Eurasia. The differences in the classification of mycobiota of these fungi resulting from the used coefficients of similarity, aggregation algorithms, and opinions of different interpreters are shown. A method of combining different classifications is proposed. A further study on a larger number of fungal groups would be more representative and would contribute to the creation of a unified biogeographic zonation of Northern Eurasia.     

Ecology of cryptogamic epiphytes and their communities in deciduous forests in mediterranean Spain

A distribution of the epiphytic bryophyte and lichen vegetation of deciduous forests from the centre and north of the supramediterranean belt from the Spanish Iberian Peninsula was established using numerrical (PCA, CCA) and traditional floristic characteristics. Four groups have been established in relation to several syntaxa. Derived by numerical classification, possible successional trends between the groups with respect to changes in moisture, light and diameter of the trees are described. Nevertheless, patterns with succession in epiphytic communities are very complex to establish.     

Plant communities in broad-leaved deciduous forests in Hordaland county, Western Norway

The vegetation of broad-leaved deciduous forests in Hordaland, Western Norway is described with regards to species composition and structure. The investigation is based on phytosociological analyses of native forest stands dominated by Corylus avellana, Fraxinus excelsior, Ulmus glabra , or Tilia cordata. Two-way-indicator analysis (TWINSPAN) and correspondence analysis (CA) are used to distinguish different vegetation types and assess possible gradients in the vegetation data. The vegetation types are discussed in relation to equivalent forest communities and to syntaxonomical units. Two forest types are described at the first hierarchical TWINSPAN level: 1) A hygrophilous and slightly thermophilous Fraxinus excelsior-Cirriphyllum piliferum forest characterised by an open tree canopy, a dense field layer of tall herbs and ferns, and a high cover of bryophytes. 2) A thermophilous and less hygrophilous Corylus avellana-Brachypodium sylvaticum forest characterised by a dense tree layer, a more open field layer with larger elements of small herbs, and a somewhat lower bryophyte cover. The CA analysis clearly separates the samples from the first TWINSPAN division along the first ordination axis. Five forest types have been described at the second hierarchical level, mainly associated with differences in mesotrophic and eutrophic species, but there is clearly a gradient structure in the species composition between these plant communities. In relation to syntaxonomy, the first TWINSPAN division supports the separation of the west Norwegian broad-leaved deciduous forests into a hygrophilous plant community, the Eurhynchio-Fraxinetum (Blom 1982) Øvstedal 1985 and a drier and more thermophilous community, the Primulo-Ulmetum (Blom 1982) Øvstedal 1985.     

The convergent trajectories of bird communities along ecological successions in european forests

Summary There is much more variation in the composition of bird communities in the earlier open and semi-open seral stages of ecological successions in forested landscapes of Europe than later on in preforested and forested climactic stages. The demonstration of this trend is achieved from the study of four habitat gradients, two in the mediterranean region (Provence and Corsica) and two in central Europe (Burgundy, France and Poland). A multivariate analysis has been used to illustrate the dynamics of communities along these succession. Displays of the results in bivariate space as well as an illustration of the distributional profiles of some of the most characteristic species show that: i) there is a discrimination between the two mediterranean gradients and the two medioeuropean ones and ii) each succession starts with a very distinct set of species and then the four gradients regularly converge in the last climactic stage where there is almost no discrimination between communities. These results are discussed in the light of the history of European biotas during the Pleistocene. The reason why there is more variation in species composition in the earlier seral stages than in the later forested stages are discussed according to current theories on the role of habitat selection on speciation processes.     

Factors affecting bird communities in fragments ofsecondary pine forests in the north-western Mediterranean basin

We assessed the influence of size, extent of isolation and vegetation structure of secondary forest fragments on the richness and species composition of breeding bird communities in a sample of pine forest fragments surrounded by an agricultural matrix in the north-western Mediterranean basin. Fragment size was the main predictor of bird’s occurrence, since it accounted for 70 % of the model variation. Isolation was also a valuable predictor of species occurrence, especially for forest specialists. Finally, subarboreal vegetation such as holm oak and a well-developed tree layer of large pines favoured forest species occurrence. Therefore, in spite of the long history of human impact, forest birds in Mediterranean mosaics are sensitive to both habitat loss and isolation of remnant patches in a similar manner to the patterns found in other temperate fragmented landscapes where human impact is more recent.     

Effects of fire on the bird communities of tropical woodlands and open forests in northern Australia

Birds were censused at 24 plots which had been subjected to 14 years of four experimental fire regimes (fire-exclusion, annual early burn, annual late burn and biennial burn) in Eucalyptus open forest and woodland at Munmarlary, Northern Territory. In addition, short-term responses of birds to fire at a savannah woodland site near Katherine were examined. At this site patches of the study area were burnt in April, June and August 1987, and birds were censused monthly over the period April to October 1987. Many bird species were attracted to areas that had been recently burnt. These were mostly granivorous species, and omnivorous and carnivorous species which fed on the ground. Influxes of these species occurred because fires increased accessibility to food by clearing the ground of its previous dense grass layer. Succession of bird species to long-unburnt areas was relatively limited, although species which fed or nested in the shrubby understorey occurred at greater densities in such areas. Frugivorous birds may become more common in areas protected from fire, thereby driving succession to monsoon vine forests from Eucalyptus forests, though, in terms of current fire regime, this process may be prohibitively slow. The hot fires of the mid to late Dry season may be less beneficial to granivores than the cooler fires typical of the early Dry. Accordingly, recent changes in the fire regime may have contributed to the decline of some bird species.     

Carbon fluxes in coniferous and deciduous forest soils

Aims

Our aims were to identify responsible factors for the site-to-site variability in soil CO₂ efflux and to assess the sources of soil CO₂ of different forest types on a regional scale.

Methods

Soil CO₂ effluxes were measured over 1–4 years in four coniferous and three deciduous forests of Bavaria, Germany, and related to climate, soil properties and forest productivity. Total belowground carbon allocation (TBCA) was assessed using soil CO₂ effluxes and aboveground litterfall. Additionally, CO₂ production of organic layers was examined over 10 months under constant conditions in an incubation experiment.

Results

Annual soil CO₂ effluxes were not different among the forest sites, but predicted effluxes at a given temperature of 10°C revealed some significant differences and correlated with the phosphorous stock of the organic layers. The incubation study indicated 50% faster decomposition of organic layers from deciduous than from coniferous forests. TBCA related to soil CO₂ efflux was smaller in the deciduous than in the coniferous forests. The ratio of TBCA to soil CO₂ efflux was positively correlated with the C stock of organic layers.

Conclusions

Our results suggest that marked differences in site characteristics have little impact on soil CO₂ effluxes at the regional scale, but the contribution of soil CO₂ sources varies among the forest types.     

Faunal diversity and vegetation structure of some deciduous forests in South Sweden

The relationships of faunal diversity and vegetation structure were studied in twenty deciduous forest plots in South Sweden, all of them managed. Following animal groups were censused: shrews (Soricidae), bats (Chiroptera), voles (Cricetidae), fieldmice (Muridae), birds (Aves), groundliving beetles (Coleoptera), spiders (Araneida), and harvestmen (Opilionidae). The analysis of the 22 vegetation variables was made by means of repeated and rotated PCA. Rarefaction was used to ordinate the bird species richness of the different forest plots.
The multivariate vegetational analysis resulted in three distinct and readily interpretable components: horizontal and vertical spatial heterogeneity, and mean basal area. The number of small mammal species (except bats) was greatest in forests with great amount of understory while the number of bat species increased with increasing mean basal area. The number of bird species in a fixed number of territories was also highly correlated with the mean basal area. Hence, maximum bird species richness was obtained in mature forests but not in those with greatest vertical heterogeneity. The invertebrate communities showed very few distinct relationships to the vegetation structure.
Dominance decreased as vegetation complexity increased. Dominance also decreased with increasing species richness in all faunal communities studied.