Field Layer Cover Research Articles

Alpine restoration: planting and seeding of native species facilitate vegetation recovery

Vegetation recovery in severely disturbed alpine ecosystems can be accelerated through active restoration measures. This study evaluated the short‐term effects of two restoration treatments, planting of propagated native Salix (willow) shrubs in three different densities (1, 2.5, and 4 plants/m2) and seeding of the native grass Festuca ovina (sheep fescue), in a disturbed alpine heathland. We evaluated natural vegetation recovery (i.e. vegetation cover, vascular plant species richness, and Salix recruitment) in permanent plots, 5 years after the implementation of restoration measures. The results showed that both treatments had positive but different effects on vegetation recovery; Salix plantings (with densities ≥2.5 plants/m2) increased vascular plant species richness and recruitment of Salix seedlings, whereas seeding of F. ovina increased bottom and field layer cover. Our results also show the importance of soil conditions for vegetation recovery, as moister plots with a higher percentage of fine soil substrate had a higher vegetation cover and vascular plant species richness. This study shows that different restoration treatments can work complementary and also highlights the importance of considering different indicators of vegetation recovery when evaluating the effectiveness of restoration measures.

Tree height as the main factor causing disappearance of the terricolous lichens in the lichen Scots pine forests

The lichen Scots pine forests habitats are undergoing rapid disappearance across Europe. Due to the semi-natural character of this habitat and an increase of the nitrification as a result of air pollution, determination of factors responsible for the decrease in lichen field layer cover requires a comprehensive approach. Our study aimed to investigate environmental factors necessary for the determination of active protection measures in order to maintain this vulnerable habitat. Specifically, we aimed to investigate: 1) the environmental factors influencing lichen cover in the lichen Scots pine forests of Bory Tucholskie National Park; 2) the differences in habitat variables between sites with lichen-rich and bryophyte-rich field layers. In our study, we used vegetation and microhabitat properties data collected over three years of surveys, as well as ALS LiDAR data. Our results indicated that lichen and bryophyte cover, tree height, tree cover, thickness of organic matter layer, soil temperature and soil water content differed between lichen-rich and bryophyte-rich sites. We found a significant negative relationship between lichen cover recorded within the field layer and tree height. The lichen-rich field layer developed better in areas with lower tree height and thinner layer of organic matter, which created a favorable habitat conditions for lichen development. Our research revealed the previously unknown impact of tree height for the development of lichen field layer. These findings can be used to plan the active conservation measures of lichen Scots pine forests.

Ecosystem restoration in fire-managed savanna woodlands: Effects on biodiversity, local livelihoods and fire intensity

Ethiopia aims to restore 15 million ha degraded forests and woodlands, but effects on the potentially contrasting goals of long-term carbon storage, biodiversity and sustainable livelihoods are unknown. To quantify the effects of grazing exclusion on vegetation and fire behaviour, we established six 30 × 30 m fenced exclosures with grazed controls, in a mesic wooded savanna. Experimental burns were done after 1.5 years. Tree seedlings were few but more common inside fences. Field layer cover and biomass increased inside fences, and grass species increased in numbers and cover. Fire intensity was higher inside fences, killing shrubs and saplings but not mature trees. Interviews confirmed that overgrazing has resulted in “cool fires”, causing shrub encroachment. High-intensity fires occurred in the 1980s after a zoonotic disease killed most livestock. Short-term increase in carbon storage through fire and grazing exclusion may lead to loss of pasture, and in the long-term increased wildfire risk.

Quantifying suitable late summer brood habitats for willow ptarmigan in Norway

BackgroundHabitat models provide information about which habitat management should target to avoid species extinctions or range contractions. The willow ptarmigan inhabits alpine- and arctic tundra habitats in the northern hemisphere and is listed as near threatened (NT) in the Norwegian red list due to declining population size. Habitat alteration is one of several factors affecting willow ptarmigan populations, but there is a lack of studies quantifying and describing habitat selection in willow ptarmigan. We used data from an extensive line transect survey program from 2014 to 2017 to develop resource selection functions (RSF) for willow ptarmigan in Norway. The selection coefficients for the RSF were estimated using a mixed-effects logistic regression model fitted with random intercepts for each area. We predicted relative probability of selection across Norway and quantile-binned the predictions in 10 RSF bins ranging from low-(1) to high-(10) relative probability of selection.ResultsRandom cross-validation suggest that our models were highly predictive, but validation based spatial blocking revealed that the predictability was better in southern parts of Norway compared to the northernmost region. Willow ptarmigan selected for herb-rich meadows and avoided lichen rich heathlands. There was generally stronger selection for vegetation types with dense field layer and for rich bogs and avoidance of vegetation types with sparse field layer cover and for lowland forest. Further, willow ptarmigan selected for areas around the timberline and for intermediate slopes. Mapping of the RSF showed that 60% of Norway is in the lowest ranked RSF bin and only 2% in the highest ranked RSF bin.ConclusionsWillow ptarmigan selected for vegetation types with dense field layer and bogs at intermediate slopes around the timberline. Selection coincides with previous habitat selection studies on willow ptarmigan. This is the first attempt to assess and quantify habitat selection for willow ptarmigan at a large scale using data from line transect distance sampling surveys. Spatial variation in predictability suggests that habitat selection in late summer might vary from north to south. The resource selection map can be a useful tool when planning harvest quotas and habitat interventions in alpine areas.

Moss invasion in a dune ecosystem influences ground-dwelling arthropod community structure and reduces soil biological activity

One of the most invasive moss species worldwide is Campylopus introflexus, which can change vegetation and habitat conditions of native ecosystems (dunes, heathland). However, the impact of the moss on the community structure of multiple arthropod taxa and ecosystem functions is still poorly understood. For a better understanding of impacts of invasive species, scientific studies are needed which explicitly define the investigated impact. We defined impact based on the most recently recommended categories: ‘directionality’, ‘classification and measurement’, ‘ecological or socio-economic changes’, and ‘scale’. We investigated the impact of C. introflexus on a wide range of ground-dwelling arthropods (pitfall traps) and on soil biological activity (bait-lamina test) by comparing invaded and uninvaded grey dunes in a field observational study on the island of Hiddensee, Germany. We found that the moss and the associated habitat modifications influenced the arthropod community structure. The effects on arthropod densities were taxon-specific and were positive (Coleoptera, Formicidae, Opiliones) or neutral (Araneae, Orthoptera). For Collembola and Isopoda we assumed an indirectly negative effect of the moss due to associated lower field layer cover and soil moisture. C. introflexus drastically reduced the soil biological activity, which was about six times lower in invaded grey dunes. The reduced soil moisture associated with the moss invasion was identified as the main driver of the shifts in community structure and soil biological activity. By explicitly defining ‘impact’ in our study, we add to recent discussions within invasion ecology about invasive species impacts. Our study demonstrates the importance of cross-taxon approaches which include key ecosystem processes such as soil biological activity and therefore contributes to the progress towards the general understanding of plant invasion impacts.

Modelling habitat use of Tetrao urogallus L. in Austria for conservation issues

Loss and deterioration of habitats are major threats for Tetrao urogallus in central Europe, where forests are highly fragmented and forest practices have distinctly changed during the last decades. Habitat models are important tools for conservation planning, often relying on presence–absence data. We mapped indirect signs of Tetrao urogallus presence as well as habitat variables over a series of seven study areas in the Austrian Alps, situated on limestone and on silicate rock. We modelled habitat use of Tetrao urogallus with one parametric approach (binary logistic regression) and two machine learning classification algorithms (classification trees and random forests) for both geological substrata separately. All three modelling approaches performed equally well in terms of accuracy or predictive power, but differed in model calibration. Three variables significantly contributed to all three habitat models on limestone and on silicate substrate, respectively, i.e. the cover of field-layer, the cover of dwarf shrubs and the proportion of deciduous trees in forest stands on limestone and the cover of field-layer, the canopy cover and the occurrence of Abies alba and/or Pinus sylvestris in forest stands on silicate rock. Some variables like the cover of Rubus sp. appeared in several models, which are not frequently mentioned in other studies. There have been some explanatory variables, which would have been missed, when applying just one single modelling approach, for example the occurrence of forest edges, the availability of canopy gaps and the supply of ant hills. Our results suggest differing habitat management strategies on limestone and on silicate rock. Considering the large spatial requirements of Tetrao urogallus the necessity of active habitat management for Tetrao urogallus becomes obvious.

Changes in the abundance of keystone forest floor species in response to changes of forest structure

AbstractQuestionDoes the abundance of keystone forest floor species change in response to changes in the forest structure?LocationSwedenMethodsWe used data from theSwedishNationalForest Inventory to investigate changes in the abundance of three common species, as well as the total abundance of all understorey vascular plants (the field layer) in forests in the boreal and temperate parts ofSweden.GLMs andGAMs were used to relate species abundance and temporal changes in abundances to forest structure and forest structural change.ResultsProductivity, measured as the site index, was the most important determinant of individual species' abundance. The volume ofPicea abies, the density of tree stems and forest age were among the most important forest structural variables. We found that the dwarf shrubVaccinium myrtillus, the narrow‐leaved grasses (mainlyAvenella flexuosa) and the total field layer cover decreased in borealSweden from 1994 through 2010 and that these changes coincided with an increase in forest density and with a reduction in forest age.ConclusionsChanges inSwedish forests to higher tree layer density and younger age appear to contribute significantly to current changes in forest floor vegetation. The use of more intensive thinning practices to reduce the total density of the forest and to increase the proportion of broad‐leaved tree species andPinus sylvestriswould favour the forest floor species in this study. Moreover, increasing forest age (i.e. the length of rotation periods) might favourV. myrtillusin particular, for which the time since disturbance is important for the recovery of pre‐disturbance abundance. However, increased thinning intensity and forest age will reduce the potential for wood production, implying a trade‐off between production of wood and maintenance of well‐developed forest floor vegetation.

Recent patterns of change in vegetation structure and tree composition of British broadleaved woodland: evidence from large-scale surveys

Evidence is presented of widespread changes in structure and species composition between the 1980s and 2003–2004 from surveys of 249 British broadleaved woodlands. Structural components examined include canopy cover, vertical vegetation profiles, field-layer cover and deadwood abundance. Woods were located in 13 geographical localities and the patterns of change were examined for each locality as well as across all woods. Changes were not uniform throughout the localities; overall, there were significant decreases in canopy cover and increases in sub-canopy (2–10 m) cover. Changes in 0.5–2 m vegetation cover showed strong geographic patterns, increasing in western localities, but declining or showing no change in eastern localities. There were significant increases in canopy ash Fraxinus excelsior and decreases in oak Quercus robur/petraea. Shrub layer ash and honeysuckle Lonicera periclymenum increased while birch Betula spp. hawthorn Crataegus monogyna and hazel Corylus avellana declined. Within the field layer, both bracken Pteridium aquilinum and herbs increased. Overall, deadwood generally increased. Changes were consistent with reductions in active woodland management and changes in grazing and browsing pressure. These findings have important implications for sustainable active management of British broadleaved woodlands to meet silvicultural and biodiversity objectives.

Scale dependency of species composition and environmental variables in the strata of a deciduous forest

We conducted a field study to determine whether species composition and environmental relationships were scale dependent among the strata of a temperate deciduous forest. We compiled tree basal area, woody understory density, field layer cover and three environmental variables from 378 permanent plots in ten 7–386 ha sites in the 294,455 ha Shawnee National Forest, southern Illinois, USA. The effect of changing sample foci (area of inference) without changing the extent (geographic space) on the relationship between species composition and environmental factors was quantified using Non-metric Multidimensional Scaling (NMDS) and Procrustes analysis separately for each stratum. Species composition-environment relationships showed a separation of sites based on their geographic location and bedrock. Species data collected from these heterogeneous and hierarchically structured habitats across scales exhibited varying degree of specialization depending on the habitat. NMDS showed that the species composition-e...

Nest orientation and hatching success in the tree pipit Anthus trivialis

Many open‐nesting bird species orient their nests relative to surrounding vegetation to avoid adverse environmental conditions. In eastern England, tree pipit Anthus trivialis nests predominantly faced east, an orientation that provided shelter from prevailing WSW winds, allowed warming by the morning sun and which, together with relatively high field layer cover, shaded nest contents from the midday sun. Mean orientation moved from south to north through the breeding season as temperatures increased, suggesting that solar radiation was a key influence on nest placement for tree pipits in the study area. Tree pipit nests with eastward orientations experienced better hatching success than those in less‐preferred orientations and it is suggested that this was due to their thermal advantages. In contrast, nest orientation had no influence on nestling survival.

An analysis of central Alpine capercaillie spring habitat at the forest stand scale

We investigated the small-scale habitat selection of capercaillie ( Tetrao urogallus) with respect to forest stand composition and topographic characteristics in managed alpine forests of the central Alps in eastern Switzerland. In 12 study areas, we compared 184 study plots in forests stands used (presence) or unused (absence) by the species in spring. A logistic regression model with four predictor variables correctly classified 68.5% of the study plots for capercaillie presence or absence. The model was validated with a 5-fold data-splitting procedure. Four forest stand variables significantly contributed to the model: canopy cover, field-layer cover, the number of basal-branched solitary trees and stand structure. We could not confirm a direct response of capercaillie to bilberry cover in the study areas although bilberry was more abundant in presence plots. Our model is a practical tool for forest managers in the central Alps to assess the abundance and distribution of suitable habitat patches, to monitor trends in habitat suitability dynamics, and to increase the vegetation-related carrying capacity for capercaillie by improving vegetation structure. Suitable capercaillie habitat is characterised by an intermediate canopy cover (30–60%), a well-developed field-layer and the presence of several basal-branched solitary trees. The model is partly based on forest stand variables used in national and regional inventories. However, the inventories would be improved for conservation purposes if information on basal-branched solitary trees as well as field-layer type and composition, preferably the abundance of Ericaceae, Vaccinium and Rubus species, were also collected.

Primary succession pathway of Norway spruce communities on land-uplift seashores

The rising Gulf of Bothnia coastlines provide sequences of primary succession. This paper, based on data from transects in northeast Sweden (63º 51’ N, 20º 43’ E), elucidates the pathway of Norway spruce community succession on ground-moraine seashores. We studied spatial and temporal variation in depth of surface organic layer, cover of field layer and bottom layer, density of spruce categories from current seedlings to mature and dead spruce, and diversity changes. We found that field layer declines in cover while bottom layer increases in cover and that field and bottom layers and spruce category diversity show unimodal trends with time of succession. Modal diversity occurred after 100 to 200 years for field- and bottom-layer types and after 200 to 230 years for spruce categories. We also found that spruce seedlings are able to colonize after only 30 to 40 years of succession (25 to 35 cm above mean sea level), that spruce category size increases with time of succession, and that spruce mortality occurs both among small-sized trees at earlier stages and among larger-sized trees at later stages approaching old-growth conditions. We present successional stages of field- and bottom-layer types, and of spruce categories, developed from TWINSPAN analyses and models of organic layer depth development over time.

The habitat requirements of hazel grouse ( Bonasa bonasia) in managed boreal forest and applicability of forest stand descriptions as a tool to identify suitable patches

We evaluated preferences of habitat variables by hazel grouse ( Bonasa bonasia) in an intensively managed boreal landscape in south-central Sweden. We surveyed 71 forest patches that varied in tree age, tree species composition, structure and field layer, as described by ordinary forest stand data. They were surveyed during autumn and spring for 2 years. A distinct difference in habitat quality, measured as amount of vertical cover and development of the field layer, was found among patches occupied during spring, patches occupied during only autumn and unoccupied patches. We found that the existing nation-wide forest stand data are adequate to select habitat patches to maintain hazel grouse in managed forested landscapes. However, the stand data would be improved if parameters concerning field-layer type, alder and field-layer cover were added. We used the results of an earlier study to predict hazel grouse occurrence in our studied patches. Unthinned middle-aged (20–69 years) or old (>90 years) stands rich in deciduous trees (5–40%), including alder, and with a rich field layer were the most often occupied patches. Moreover, the low density of hazel grouse in this landscape, compared to hazel grouse densities in less intensively managed landscapes, clearly showed the influence of forestry on the species.

Relationships between vegetation, site type and stand structure in coniferous plantations in Britain

Plant communities (ground and field layer species) within a wide range of coniferous forest stands across Britain were classified using the National Vegetation Classification, and community composition and diversity related to stand structure and site characteristics. Data were collected from 12 plantation forest sites, encompassing a range of climatic conditions (uplands, foothills, and lowlands), crop types (Scots pine, Sitka spruce, Norway spruce and Corsican pine), and crop ages (pre-thicket, mid-rotation, mature and over-mature). Vegetation communities in lowland sites were poorly correlated with semi-natural woodland analogues, with ‘goodness-of-fit’ coefficients less than 40%. The highest coefficients were obtained for mature and over-mature pine and spruce stands in the uplands and foothills climatic zones. These stands were matched most closely to semi-natural pinewoods and oakwood communities. Principal components analysis produced four summary soil vectors and four habitat structure vectors, that described 84 and 79% of the variability in the site and stand structure data, respectively. These vectors were related to plant community composition, species richness and diversity using canonical correspondence analysis and correlation analysis. Variation in community composition was related principally to a soil fertility gradient, defined by increasing pH, exchangeable Ca, and available N in NO 3 − form, coupled with decreases in soil organic matter and N in NH 4 + form. Vascular plant and bryophyte species diversity was inversely related to available N. Uplands and foothills Scots pine and Sitka spruce sites had plant communities typical of acid, infertile soils, whereas lowland Norway spruce sites had communities associated with high soil fertility. Plant community composition and diversity was also significantly related to measures of vertical stand structure. Pre-thicket plots, with high values for field layer vertical cover; had distinctive communities and were more diverse than mid-rotation and mature plots; which had high canopy cover values, and low shrub and field layer cover. A positive relationship was recorded between deadwood volume and bryophyte species diversity, with over-mature Sitka spruce stands in the uplands having particularly high volumes of deadwood due to windthrow. This influence of stand structure suggests that plant community diversity can be enhanced in commercial conifer forests by extending rotation lengths, introducing alternative silvicultural systems such as shelterwood, and increasing deadwood volumes.

Relationships between insect diversity and habitat characteristics in plantation forests

A methodological approach to the identification of biodiversity indicators in commercial forest stands is illustrated by analysis of the relationships between syrphid (hoverflies) and carabid (ground beetles) community composition and diversity, and stand structure and field layer vegetation. Data were collected from 12 commercial forest sites encompassing a range of climatic conditions and different crop types (Scots pine, Sitka spruce, Norway spruce and Corsican pine) across the UK. Comparisons were also made between unmanaged semi-natural Scots pine woods and Scots pine plantations. For both syrphids and carabids, no differences in species richness and diversity were recorded between semi-natural stands and plantations; one rare syrphid considered to be restricted to semi-natural pine stands was also found in spruce. Syrphid species diversity and richness was higher in southern spruce sites than in the northern sites. Northern sites had distinctive carabid communities, as did sites in the New Forest, a large ancient woodland in southern England. Of the measured habitat variables, vertical stand structure showed the best correlation with species richness and diversity of both carabids and syrphids. Richness and diversity were less in stands with high vertical cover values for canopy layers. Stands with higher field layer cover supported greater syrphid diversity, but lower carabid diversity. Measures of stand structure could be used as potential indicators of syrphid and carabid diversity, but additional habitat parameters also need to be tested.

Vegetation‐environment relationships of old‐growth spruce forest vegetation in Østmarka Nature Reserve, SE Norway, and comparison of three ordination methods

The relationship between vegetation and environmental variables has been studied in 100 sample plots, each 0.25 m2, in old‐growth spruce forest at Høgkollen, ØOstmarka Nature Reserve, SE Norway. Each sample plot was supplied with measurements of 13 environmental and 5 biotic variables. Parallel application of three ordination techniques, PCA, DCA and LNMDS, resulted in different sample plot configurations. PCA performed poorest due to strong influence of outliers and circumstantial evidence indicated better performance of LNMDS than DCA. Statistical analyses of the relationships between vegetation and ecological data revealed a parallel gradient in soil moisture (decreasing) and canopy closure (increasing) as the most important for differentiation of the vegetation. Species number and field layer cover decreased, while bottom layer cover increased, due to increasing cover of Dicranum majus, with decreasing soil moisture and increasing canopy closure. Constrained canonical correspondence analysis (CCA) was used to partition the variation of the species‐sample plot matrix into spatial, environmental and unexplained variation, and combinations. The fraction of unexplained variation was high (80.9 %), most likely due to small sample plot size and short gradient lengths. Most of the explained variation was attributable to environmental factors alone (54.5%). Only 6.3% was shared between environmental and spatial variation, which indicated minor importance of broad‐scale and geographically structured environmental variation. Strictly spatial variation constituted 39.3%. However, the spatially structured environmental variation was low, so the causes of spatial variation were likely not to be found among the measured environmental variables.

Fungi-vegetation relationships in aPinus sylvestrisforest in central Norway

The macrofungal Basidiomycete community of a Pinus sylvestris forest was investigated in 50 plots, 2 × 2 m, to see how vegetation composition and space influenced the distribution of saprotrophic and ectomycorrhizal fungi. Mantel tests and partial Mantel tests revealed a relationship between total cover of the field layer and mycorrhizal fungi, and total cover of the bottom layer and saprotrophic fungi. These results are consistent with the predictions that mycorrhizal fungi are mainly influenced by plant species present in the root zone, whereas saprotrophic fungi are mainly influenced by the plant species of the bottom layer. Variation in the abundance of tree species did not influence the distribution of macrofungal species at this scale. The spatial patterns of fungal distribution found in this study did not deviate significantly from a random distribution. Indirect ordination showed that the ectomycorrhizal fungi mainly responded to a gradient in cover of the field layer, whereas the saprotrophs seemed to respond to a complex gradient of cover of field and bottom layer, moisture, and paludification. A direct ordination using both vegetation and fungi descriptors indicated that some of the covariation in the saprotrophic fungi and the bottom layer might be coordinated responses to changes in the field layer. A considerably higher β diversity was found among the fungi than in the vegetation. Key words: basidiomycetes, saprotrophic fungi, mycorrhizal fungi, fungi–vegetation relationships, Mantel test, ordination.