Effects of urbanization on ground beetle assemblages (Coleoptera, Carabidae) of grassland habitats in western Canada

We pitfall-trapped carabid beetles across an urban-rural gradient in central Alberta, Canada to assess the relative contributions of landscape structure and habitat quality in explaining variation in composition of assemblages. The gradient ranged from the "urban" zone in the city of Edmonton, through a "suburban" zone just outside the city, into a "rural" zone 25–60 km east of the city. We trapped beetles at three replicated sites for each of two habitats (unmanaged grasslands and highly managed graveyards) in each of the three zones. Most of the 24 species (3162 individuals) captured were commonly associated with open habitats. Pterostichus melanarius , an introduced species, made up 80% of the total catch. Carabid assemblages of grasslands and graveyards were distinct, with lower species richness and lower catch rates of native, introduced and brachypterous carabids in graveyards. Graveyard assemblages also had proportionally fewer brachypterous carabid individuals (32 vs 52%) and species (20 vs 36%), suggesting that populations recruit locally from elsewhere after disturbances. Native carabids were least abundant in the urban areas. Brachypterous carabids were similarly abundant across the gradient, but more occurred in the urban zone than elsewhere (32 vs 5–10%). Samples from graveyards were characterized by lower beta diversity (variation among samples) than those from grasslands, but beta diversity was more-or-less equally variable across the gradient within habitats. The amount of unmanaged grassland habitat and the degree of urbanization significantly influence carabid assemblages, and therefore are relevant to management and conservation of urban grassland areas.     

The value of semi-natural grasslands for the conservation of carabid beetles in long-term managed forested landscapes

Species rich semi-natural grasslands are disappearing across Europe, affecting invertebrate diversity negatively. In NW Spain, the recent abandonment of traditional farming practices and the gradual decrease in grazing pressures are reducing the number and extent of montane grasslands. In this context, we investigated the composition of carabid beetle (Coleoptera, Carabidae) assemblages that inhabit semi-natural grasslands situated in long-term managed oak and beech forested landscapes. According to their spatial arrangement, the studied grasslands were classified into: (1) interior or gap grasslands (small and completely surrounded by continuous forest) and (2) exterior grasslands (large and connected to a variety of habitat types). Our results indicate that, within each forested landscape, the gap and exterior grasslands harboured particular carabid assemblages (i.e. exclusive or abundantly collected species), which were also distinct from the surrounding forest carabid fauna. Dissimilarities between gap and exterior grasslands in each landscape suggest great carabid diversity at the regional scale. We also detected species-specific responses as several carabids were mainly associated with gap or exterior grasslands. Consequently, in highly modified forested landscapes, semi-natural grassland remnants may constitute great value for the protection of the carabid fauna. Specifically, we recommend conservation strategies that preserve variety in grassland features and maintain proper management activities to prevent the loss of specialised species and a decrease in regional carabid diversity.     

The impact of shrub encroachment on savanna bird diversity from local to regional scale

Aim  Evidence is accumulating of a general increase in woody cover of many savanna regions of the world. Little is known about the consequences of this widespread and fundamental ecosystem structural shift on biodiversity.
Location  South Africa.
Methods  We assessed the potential response of bird species to shrub encroachment in a South African savanna by censusing bird species in five habitats along a gradient of increasing shrub cover, from grassland/open woodland to shrubland dominated by various shrub species. We also explored historical bird species population trends across southern Africa during the second half of the 20th century to determine if any quantifiable shifts had occurred that support an ongoing impact of shrub encroachment at the regional scale.
Results  At the local scale, species richness peaked at intermediate levels of shrub cover. Bird species composition showed high turnover along the gradient, suggesting that widespread shrub encroachment is likely to lead to the loss of certain species with a concomitant decline in bird species richness at the landscape scale. Finally, savanna bird species responded to changes in vegetation structure rather than vegetation species composition: bird assemblages were very similar in shrublands dominated by Acacia mellifera and those dominated by Tarchonanthus camphoratus .
Main conclusions  Shrub encroachment might have a bigger impact on bird diversity in grassland than in open woodland, regardless of the shrub species. Species recorded in our study area were associated with historical population changes at the scale of southern Africa suggesting that shrub encroachment could be one of the main drivers of bird population dynamics in southern African savannas. If current trends continue, the persistence of several southern African bird species associated with open savanna might be jeopardized regionally.     

Plant–community responses to shrub cover in a páramo grassland released from grazing and burning

Shrub encroachment can follow grazing or burning release in páramo grasslands. While encroachment decreases herbaceous species richness in some grassland systems, the effects of this process on the herbaceous community in páramo grasslands are currently unknown. We collected data on shrub cover, herbaceous‐species cover and species composition in a páramo grassland 12 years after release from burning and cattle grazing near Zuleta, Ecuador. Topographic and soil measures were also included as predictor variables of differences in community composition. Contrary to studies in other systems, shrub cover did not have a significant effect on herbaceous‐species richness, whereas shrub‐species richness significantly increased with shrub cover. However, shrub cover was associated with significant shifts in herbaceous–community composition. Most notably, there was an increase in some shade‐tolerant forbs and tall‐statured wetland grasses with increasing shrub cover, and a corresponding decrease in some short‐statured grasses and early successional forbs. These results could indicate that the ameliorative effects of shrubs (e.g. frost and wind protection) in harsh alpine environments may partially compensate for the expected competitive effect of shrubs due to shading.     

The spatial distribution of birds and carabid beetles in pine plantation forests: the role of landscape composition and structure

Aim To evaluate the joint and independent effects of spatial location, landscape composition and landscape structure on the distribution patterns of bird and carabid beetle assemblages in a mosaic landscape dominated by pine plantation forests. Location A continuous 3000‐ha landscape mosaic with native maritime pine Pinus pinaster plantations of different ages, deciduous woodlands and open habitats, located in the Landes de Gascogne forest of south‐western France. Methods We sampled breeding birds by 20‐min point counts and carabid beetles by pitfall trapping using a systematic grid sampling of 200 points every 400 m over the whole landscape. Explanatory variables were composed of three data sets derived from GIS habitat mapping: (1) spatial variables (polynomial terms of geographical coordinates of samples), (2) landscape composition as the percentage cover of the six main habitats, and (3) landscape structure metrics including indices of fragmentation and spatial heterogeneity. We used canonical correspondence analysis with variance partitioning to evaluate the joint and independent effects of the three sets of variables on the ordination of species assemblages. Moran's I correlograms and Mantel tests were used to assess for spatial structure in species distribution and relationships with separate landscape attributes. Results Landscape composition was the main factor explaining the distribution patterns of birds and carabids at the mesoscale of 400 × 400 m. Independent effects of spatial variables and landscape structure were still significant for bird assemblages once landscape composition was controlled for, but not for carabid assemblages. Spatial distributions of birds and carabids were primarily influenced by the amount of heathlands, young pine plantations, herbaceous firebreaks and deciduous woodlands. Deciduous woodland species had positive responses to edge density, while open habitat species were positively associated with mean patch area. Main conclusions Forest birds were favoured by an increase in deciduous woodland cover and landscape heterogeneity, but there was no evidence for a similar effect on carabid beetles. Fragmentation of open habitats negatively affected both early‐successional birds and carabids, specialist species being restricted to large heathlands and young plantations. Several birds of conservation concern were associated with mosaics of woodlands and grasslands, especially meadows and firebreaks. Conserving biodiversity in mosaic plantation landscapes could be achieved by the maintenance of a significant amount of early‐successional habitats and deciduous woodland patches within a conifer plantation matrix.     

Shrub encroachment alters composition and diversity of ant communities in abandoned grasslands of western Carpathians

Invasions of woody species into grasslands abandoned by agriculture are a global phenomenon, but their effects on diversity of other taxa have been rarely investigated across both regional and local scales. We quantified how shrub encroachment affected the activity, composition, and diversity of ant communities in managed and abandoned grasslands in western Carpathians of Central Europe across four regions and four shrub encroachment stages in each region. We surveyed ant communities on 48 sites in total, with each encroachment stage replicated three times in each region and twelve times overall. We used pitfall traps to sample ants over three years (2008, 2009, 2011) and identified 9,254 ant workers belonging to 33 species in total. Although the epigaeic activity and composition of ant communities varied with region, abandoned grasslands supported a greater species richness of ants than managed grasslands regardless of the region, and especially so in more advanced shrub encroachment stages. Since the woody colonization within grasslands was moderate even in the advanced encroachment stages (on average ~40 % of grassland colonized by woody species), it allowed coexistence of forest specialists (e.g. Temnothorax crassispinus) with species typical of open grasslands, thus increasing overall ant diversity. Managed grasslands were not only less species rich compared to abandoned grasslands, but they were characterized by different species (e.g. Lasius niger, Myrmica rugulosa). The differences in ant communities between managed and abandoned grasslands are likely to cause differences in ecological functions mediated by ants (e.g. predation of arthropods or plant seed dispersal).     

The impact of high-altitude ski pistes on ground-dwelling arthropods in the Alps

The development of winter sport resorts above the timberline may affect every ecosystem component. We analyzed the effect of ski-pistes on the abundance and species richness of arthropods (namely carabids, spiders, opilionids, and grasshoppers) trapped in grasslands adjacent to the ski-run, on ski-pistes and at the edge between these two habitat types. Our results showed that diversity of brachypterous carabids, spiders, and grasshoppers decreased significantly from natural grasslands to ski-pistes. This was not true for the macropterous carabid guild, which included species with contrasting ecological requirements. The analysis of indicator species (IndVal) showed that most of the species (some of them precinctive to restricted areas in the north-western Alps) had clear preferences for natural grassland and few taxa were limited to ski-pistes. Generalized linear models suggested that the local extent of grass and rock cover can significantly affect assemblages: the low grass cover of ski-pistes, in particular, was a serious hindrance to colonization by spider, grasshopper, brachypterous, and some macropterous carabid species. The results obtained, support concerns over the possible disruption of local ecosystem functionality and over the conservation of arthropod species which are endemic to restricted alpine areas. In order to retain arthropod ground-dwelling fauna we suggest that: (i) new, environmentally friendly ways of constructing pistes should be developed to preserve as much soil and grass cover as possible; (ii) existing ski-pistes should be restored through management to promote the recovery of local vegetation.     

Effects of creation of open vegetation in abandoned terraced paddy fields on carabid beetle assemblages in temperate Japan

Many paddy fields in the mountainous rural areas of Japan have been abandoned since the 1960s, and forests have regenerated on these sites. In a mountainous area on Sado Island, a large number of abandoned paddies were converted into wetlands and open terrestrial vegetation. In this study, we used pitfall traps to examine the effects of the creation of open vegetation on carabid beetle assemblages by investigating 14 sites spanning five vegetation types: six sites in secondary forests (three coppice forests and three 40‐year‐old regenerating forests on abandoned paddies), three each in clear‐cuts and paddy levees, and two in grasslands. The 14 study sites were clearly separated into two groups different in the species composition of carabid beetles: secondary forest and grassland‐levee groups. The species composition of two clear‐cut sites was similar to that of secondary forests, whereas that of the remaining one clear‐cut site was similar to that of grasslands. Analyses of species responses showed various habitat preferences, e.g., for only coppice forests, for two types of secondary forests, for secondary forests and clear‐cuts, for clear‐cuts and grasslands, and for grasslands or levees, or no clear preference. There were no characteristic species in the regenerating forests. These results suggest that the 40‐year‐old regenerating forests may sustain only a limited subset of the carabid fauna found in coppice forests and that the creation of open vegetation in the abandoned paddies enhances carabid diversity at the landscape level by raising β diversity among the different vegetation types.     

Distribution of carabid beetles (Coleoptera: Carabidae) across a forest-grassland ecotone in southwestern China

This paper studied the occurrence of carabid beetles (Coleoptera: Carabidae) in the forest edge, the adjacent forest interior, and the surrounding grassland in southwestern China. Beetles were collected with pitfall traps along five replicated transects. Forest species rarely penetrated into the grassland from the forest interior, and the grassland specialists were not found in the forest interior. The forest edge hosted additional species from the adjacent grassland that increased its overall species richness. Nearly all forest species (23 of 24 species) and grassland species (13 of 15 species) can be found in the forest edge. Carabids of the forest edge were more similar to those of the forest interior than to those of the grassland by ordination and cluster analysis. Based on the specificity and fidelity, carabids can be distinguished into five species groups: habitat generalists, grassland-associated species, forest generalists, forest specialists, and edge-associated species. Multiple linear regression analysis showed that canopy cover and/or shrub cover were the most important factors in determining the richness, abundance, and diversity of carabids. The forest edge may serve as a transition zone for dispersal and re-colonization of carabid beetles from adjacent habitats and therefore is important for natural conservation.     

Shrub-encroachment induced alterations in input chemistry and soil microbial community affect topsoil organic carbon in an Inner Mongolian grassland

Shrub encroachment frequently occurs in arid and semi-arid grasslands worldwide and affects the regional carbon balance. Many previous studies have revealed the effects of shrub encroachment on bulk carbon content of grasslands, but molecular evidence is surprisingly lacking. In this study, we examined the chemical composition of plant tissues and soil organic carbon (SOC), and soil microbial communities to identify the effects of shrub (Caragana microphylla) encroachment on SOC storage in the top layer (0–10 cm) along a gradient of natural shrub cover in the grasslands of Inner Mongolia. We found that SOC in the shrub patches was derived mainly from leaves, whereas SOC in the grassy matrix was composed of a mixture of fresh root- and leaf-derived compounds. Compared with pure grassland, the SOC decreased by 29% in the shrub-encroached grasslands (SEGs), and this decrease was enhanced by increasing shrub cover. We also found that free lipids and lignin-derived phenols increased while the ratios of ω-C₁₈/∑C₁₈ and suberin/cutin decreased with increasing shrub cover. In addition, the ratios of fungal to bacterial phospholipid fatty acids (PLFAs) and gram-negative to gram-positive bacterial PLFAs decreased with increasing shrub cover. These results indicate that the encroachment of nitrogen-rich legume shrubs can lead to carbon loss by altering the chemical composition of plant inputs as well as the soil microbial community in grassland ecosystems.     

Progressively excluding mammals of different body size affects community and trait structure of ground beetles

Mammalian grazing induces changes in vegetation properties in grasslands, which can affect a wide variety of other animals including many arthropods. However, the impacts may depend on the type and body size of these mammals. Furthermore, how mammals influence functional trait syndromes of arthropod communities is not well known. We progressively excluded large (e.g. red deer, chamois), medium (e.g. alpine marmot, mountain hare), and small (e.g. mice) mammals using size‐selective fences in two vegetation types (short‐ and tall‐grass vegetation) of subalpine grasslands. We then assessed how these exclusions affected the community composition and functional traits of ground beetles (Coleoptera, Carabidae), and which vegetation characteristic mediated the observed effects. Total carabid biomass, the activity densities of carabids with specific traits (i.e. small eyes, short wings), the richness of small‐eyed species and the richness of herbivorous species were significantly higher when certain mammals were excluded compared to when all mammals had access, regardless of vegetation type. Excluding large and medium mammals increased the activity density of herbivorous carabid species, but only in short‐grass vegetation. Similarly, excluding large mammals (ungulates) altered carabid species composition in the short‐, but not in the tall‐grass vegetation. All these responses were related to aboveground plant biomass, but not to plant Shannon diversity or vegetation structural heterogeneity. Our results indicate that changes in aboveground plant biomass are key drivers of mammalian grazers’ influence on carabids, suggesting that bottom–up forces are important in subalpine grassland systems. The exclusion of ungulates provoked the strongest carabid response. Our results, however, also highlight the ecological significance of smaller herbivorous mammals. Our study furthermore shows that mammalian grazing not only altered carabid community composition, but also caused community‐wide functional trait shifts, which could potentially have a wider impact on species interactions and ecosystem functioning.     

Invertebrate conservation at the interface between the grassland matrix and natural Afromontane forest fragments

Diversity patterns of amphipods, carabid beetles and ants were investigated in five naturally-fragmented Afromontane forest remnants, and in the surrounding grassland matrix. Forests were architecturally similar. In contrast, grasslands surrounding these forests are subject to great differences in anthropogenic impacts. Consequently, transition from forest to grassland ranged from being abrupt (heavy disturbance) to gradual (little disturbance). Significantly different mean numbers of carabid individuals and species were captured between sites and multivariate analyses showed clear separation in carabid assemblage-structure with level of disturbance. Carabids were, furthermore, significantly more diverse in forests, compared to grasslands. Ants, however, were equally species rich between sites but were significantly more abundant and species rich in grasslands than forests. Amphipods, represented here by a single species, Talistroides africana, was significantly less abundant at highly disturbed sites and significantly more abundant in forests than grasslands. Results support the hypothesis that the dynamics of remnants are influenced by their surrounding landscape. Here, the dynamics of amphipods and carabids (predominantly forest taxa) were influenced by different disturbance regimes in grasslands surrounding these forests. Epigaeic ants, a predominantly grassland taxon here, also showed significant differences in assemblage-composition between sites with varying disturbance. Conserving Afromontane grasslands should be of prime concern because this will include the protection of forest/grassland ecotones and forest remnants.     

Soil C and N responses to woody plant expansion in a mesic grassland

Changes in land management and reductions in fire frequency have contributed to increased cover of woody species in grasslands worldwide. These shifts in plant community composition have the potential to alter ecosystem function, particularly through changes in soil processes and properties. In semi-arid grasslands, the invasion of shrubs and trees is often accompanied by increases in soil resources and more rapid N and C cycling. We assessed the effects of shrub encroachment in a mesic grassland in Kansas (USA) on soil CO₂ flux, extractable inorganic N, and N mineralization beneath shrub communities (Cornus drummondii) and surrounding undisturbed grassland sites. In this study, a shift in plant community composition from grassland to shrubland resulted in a 16% decrease in annual soil CO₂ flux(4.78 kg CO₂ m^–2 year^–1 for shrub dominated sites versus 5.84 kg CO₂ m^–2 year^–1 for grassland sites) with no differences in total soil C or N or inorganic N. There was considerable variability in N mineralization rates within sites, which resulted in no overall difference in cumulative N mineralized during this study (4.09 g N m^–2 for grassland sites and 3.03 g N m^–2 for shrub islands). These results indicate that shrub encroachment into mesic grasslands does not significantly alter N availability (at least initially), but does alter C cycling by decreasing soil CO₂ flux.     

Carabid beetle (Coleoptera: Carabidae) richness and functional traits in relation to differently managed grasslands in the Alps

Species richness, composition, and functional traits of carabid beetle assemblages (Coleoptera: Carabidae) were studied in relation to different grassland management. Carabid beetles were sampled during the summers 2008 and 2009 by 165 traps located in 11 sites in the central-eastern Italian Alps. Using mixed effect models to account for potential spatial bias, we found that mown grasslands had significantly more species, a lower proportion of wingless species and a lower proportion of species with long larval development than grazed and natural grasslands. Within grazed and mown grasslands, neither cattle density nor number of cuts had any significant effect neither on species richness nor on any of the traits. The influence of grassland management can be summarised as follows: (1) grazing does not change community structure and functional traits compared to natural grasslands; (2) mowing negatively affects the carabid beetle assemblages; (3) the intensity of grazing and of cutting may not affect the structure of species assemblages of ground beetles. Our results support the hypothesis that agroecosystem practices in alpine grasslands influence carabid beetle communities. Specifically, the species with traits typical of undisturbed habitats (low dispersal abilities and long larval development) are more sensitive to perturbations (e.g. cutting). Our suggestion for agricultural and environmental planning and for conservation schemes is that the preservation of natural grasslands (e.g. forest gaps) and the implementation of grazing should be promoted during the planning of agroecosystem mosaics.     

灌丛化对黄土高原草地植物群落结构和地上生物量的影响

中国北方草地普遍出现灌丛化现象,灌丛化改变植物群落结构、植物多样性和生产力,直接影响着草地生态保护与可持续利用。该研究以黄土高原灌丛化草地为研究对象,通过植被调查,分析比较不同坡向的灌丛斑块与禾草斑块植物群落结构(物种组成、优势种及物种多样性)和地上生物量的差异。结果发现:(1)灌丛化草地不同坡向对物种多样性及地上生物量均无显著影响(P 0.1),但不同斑块植物群落结构(P=0.001)及地上生物量(P0.001)存在显著差异。(2)灌丛化草地共出现植物29种,其中禾草斑块有27种,灌丛斑块有18种;灌丛化显著改变了植物群落的物种组成,优势种由长芒草(Stipa bungeana)更替为矮脚锦鸡儿(Caragana brachypoda),且灌丛化降低了草地物种丰富度,增加了群落均匀度。(3)灌丛化显著改变了草地地上生物量,其中灌丛斑块地上生物量较禾草斑块地上生物量增加251.2 g·m~(-2),灌丛斑块中灌木/半灌木地上生物量提高了452.1 g·m~(-2),多年生丛生禾草减少了176.5 g·m~(-2),其余功能群植物的地上生物量减少了24.4 g·m~(-2)。(4)灌丛化过程(从禾草斑块—灌丛斑块)中,植物种丢失对地上生物量减少的影响较小,新增物种和群落优势种更替促进了灌木斑块地上生物量增加;虽然灌丛化导致草地地上生物量增加,但植物物种丰富度降低和优势种更替很有可能改变草地多样性和稳定性维持机制。     

Pastoral Practices to Reverse Shrub Encroachment of Sub-Alpine Grasslands: Dung Beetles (Coleoptera,Scarabaeoidea) Respond More Quickly Than Vegetation

In recent decades, pastoral abandonment has produced profound ecological changes in the Alps. In particular, the reduction in grazing has led to extensive shrub encroachment of semi-natural grasslands, which may represent a threat to open habitat biodiversity. To reverse shrub encroachment, we assessed short-term effects of two different pastoral practices on vegetation and dung beetles (Coleoptera, Scarabaeoidea). Strategic placement of mineral mix supplements (MMS) and arrangement of temporary night camp areas (TNCA) for cattle were carried out during summer 2011 in the Val Troncea Natural Park, north-western Italian Alps. In 2012, one year after treatment, a reduction in shrub cover and an increase in bare ground cover around MMS sites was detected. A more intense effect was detected within TNCA through increases in forage pastoral value, and in the cover and height of the herbaceous layer. Immediately after treatment, changes in dung beetle diversity (total abundance, species richness, Shannon diversity, taxonomic and functional diversity) showed a limited disturbance effect caused by high cattle density. In contrast, dung beetle diversity significantly increased one year later both at MMS and TNCA sites, with a stronger effect within TNCA. Multivariate Regression Trees and associated Indicator Value analyses showed that some ecologically relevant dung beetle species preferred areas deprived of shrub vegetation. Our main conclusions are: i) TNCA are more effective than MMS in terms of changes to vegetation and dung beetles, ii) dung beetles respond more quickly than vegetation to pastoral practices, and iii) the main driver of the rapid response by dung beetles is the removal of shrubs. The resulting increase in dung beetle abundance and diversity, which are largely responsible for grassland ecosystem functioning, may have a positive effect on meso-eutrophic grassland restoration. Shrub encroachment in the Alps may therefore be reversed, and restoration of grassland enhanced, by using appropriate pastoral practices.     

Impact of the invasive moss Campylopus introflexus on carabid beetles (Coleoptera: Carabidae) and spiders (Araneae) in acidic coastal dunes at the southern Baltic Sea

Campylopus introflexus is an invasive moss in Europe and North America that is adapted to acidic and nutrient-poor sandy soils with sparse vegetation. In habitats like acidic coastal dunes (grey dunes) it can reach high densities, build dense carpets and modify habitat conditions. While the impact of the moss invasion on the vegetation is well analyzed, there is a lack of knowledge regarding possible effects on arthropods. In the present study we analyzed the impact of Campylopus introflexus on the ground-dwelling arthropods carabid beetles and spiders, as both taxa are known to be useful indicator taxa even on a small-scale level. In 2009 we compared species composition in a) invaded, moss-rich (C. introflexus) and b) native, lichen-rich (Cladonia spp.) acidic coastal dunes by using pitfall traps. A total of 1,846 carabid beetles (39 species) and 2,682 spiders (66 species) were caught. Species richness of both taxa and activity densities of spiders were lower in invaded sites. Species assemblages of carabids and spiders differed clearly between the two habitat types and single species were displaced by the moss encroachment. Phytophagous carabid beetles, web-building spiders and wolf spiders were more abundant in native, lichen-rich sites. Shifts in species composition can be explained by differences in the vegetation structure, microclimate conditions and most likely a reduced food supply in invaded sites. By forming dense carpets and covering large areas, the moss invasion strongly alters typical arthropod assemblages of endangered and protected (EU-directive) acidic coastal dunes.     

Restoration Practices Have Positive Effects on Breeding Bird Species of Concern in the Chihuahuan Desert

Woody plant encroachment into grasslands is a global concern. Efforts to restore grasslands often assume that removal of woody plants benefits biodiversity but assumptions are rarely tested. In the Chihuahuan Desert of the Southwestern United States, we tested whether abundances of grassland specialist bird species would be greater in plant communities resulting from treatment with herbicides to remove encroaching shrubs compared with untreated shrub‐dominated areas that represented pre‐treatment conditions. In 2010, we surveyed breeding birds and vegetation at 16 treated–untreated pairs. In 2011, we expanded the survey effort to 21 treated–untreated pairs, seven unpaired treatment areas, and five reference grassland areas. Vegetation in treatment areas had higher perennial grass foliar and basal cover and lower shrub foliar cover compared with untreated areas. Several regionally declining grassland specialists exhibited higher occurrence and relative abundance in treated areas. A shrubland specialist, however, was associated with untreated areas and may be negatively impacted by shrub removal. Bird community composition differed between treated and untreated areas in both years. Our results indicate that shrub removal can have positive effects on grassland specialist bird species, but that a mosaic of treated and untreated areas might be most beneficial for regional biodiversity .     

Epiphytic lichens on Juniperus communis – an unexplored component of biodiversity in threatened alvar grassland

Semi‐natural grasslands, among them thin‐soil calcareous grasslands (alvars), have great conservation value but have become increasingly rare in Europe. The main threat to alvar grasslands is the encroachment by juniper Juniperus communis and therefore it is usually removed during the restoration practice. Juniper can also be a host plant for many epiphytic lichens, but its role as a phorophyte is poorly known. We studied epiphytic lichen diversity on 126 junipers in 17 sites in western Estonia and found 140 lichenized taxa including several rare and red‐listed species. Using indirect and direct multivariate analyses (DCA, pCCA) and general linear models we revealed that both habitat and phorophyte properties affect lichen assemblies on juniper. Lichen species richness per site showed a unimodal relationship with compound factors of site productivity and juniper characteristics (stem circumference and juniper width). Lichen species richness per phorophyte was increasing with its size and with the proportion of dead branches, and was twice higher in plate alvars than in ryhk alvars. Also, the species composition in plate alvars differed from ryhk alvars by having 42 characteristic lichen species in plate alvars vs three indicators of ryhk alvars. The composition of lichens was significantly influenced by encroachment of alvars, e.g. by high juniper cover and shrub layer height, as well as by the proportion of dead branches and stem circumference of juniper. We conclude that the epiphytic lichen assemblies on junipers are threatened by grassland encroachment similarly to ground layer lichen assemblies. We suggest that some old and scencent junipers should be preserved during the restoration of alvar grasslands.     

小叶锦鸡儿灌丛化对典型草原群落结构与生态系统功能的影响

草原灌丛化是全球干旱半干旱地区面临的重要生态问题。灌丛化对草原生态系统结构与功能的影响较为复杂, 有待于在更广泛的区域开展研究。该研究在内蒙古锡林郭勒典型草原选择轻度、中度和重度灌丛化草地, 通过群落调查, 结合植物功能性状和土壤理化性质观测, 研究了小叶锦鸡儿(Caragana microphylla)灌丛化对草原群落结构(物种多样性、功能多样性和功能群组成)和生态系统功能(初级生产力、植被和土壤养分库)的影响。结果表明: 1)不同程度灌丛化草地的物种丰富度、功能性状多样性和群落加权性状平均值差异显著, 其中, 中度灌丛化草地的物种多样性和功能多样性较高, 表明一定程度的灌丛化有利于生物多样性维持。2)重度灌丛化草地的地上净初级生产力(ANPP)显著高于轻度和中度灌丛化草地, 其原因主要是随着灌丛化程度加剧, 群落内一/二年生草本植物显著增加, 而多年生禾草和多年生杂类草显著减少。三个灌丛化草地的植被叶片和土壤碳、氮库差异均不显著。3)灌丛化对草原生态系统功能包括ANPP、植被和土壤养分库均没有直接的影响, 而是通过影响功能群组成、土壤理化性质和功能多样性, 间接地影响生态系统功能; 灌丛化导致功能群发生替代和土壤旱碱化是最重要的生物和非生物因素。