Vascular Plant Species Richness Research Articles

Quantitative evaluation of the drivers of species richness in a Mediterranean ecosystem (Cape, South Africa).

Mediterranean ecosystems have a high vascular plant species richness (SR) relative to their surface area. This SR, representing the balance between speciation and extinction, has been attributed to multiple mechanisms that result in both high rates of speciation and/or low rates of extinction. An abiding question is, however, what is special about Mediterranean ecosystems that enables this high SR? Apart from the long-term climatic stability of the region, SR has also been related to resource availability, the many individuals hypothesis, resource spatial heterogeneity, temporal heterogeneity and biotic feedbacks. Spatial patterns of species richness were related to climatic, edaphic and biotic variables and to spatial variability within the Greater Cape Floristic Region (GCFR) of South Africa. Boosted regression tree models were used to explore the strength of relationships between SR and environmental predictors related to each hypothesized mechanism. Water availability (i.e. precipitation) was a stronger predictor of SR than potential evapotranspiration or temperature. Scarcity of nutrients was also related to SR. There was no indication that SR was related to the density of individuals and only temporal heterogeneity induced by fire was related to SR. Spatial heterogeneities of climatic, edaphic and biotic variables were strongly associated with SR. Biotic interactions remain difficult to assess, although we have some evidence for a putative role in regulating SR. While the lack of ecosystem-resetting disturbances (e.g. glaciation) is undoubtedly a key requirement for high species accumulation, predictably, no one explanation holds the key to understanding SR. In the GCFR high SR is the product of a combination of adequate water, nutrient scarcity, spatial and temporal heterogeneity, and possibly biotic feedbacks.

The Historic Square Foot Dataset – Outstanding small‐scale richness in Swiss grasslands around the year 1900

AbstractGrasslands host a significant share of Europe's species diversity but are among the most threatened vegetation types of the continent. Resurvey studies can help to understand patterns and drivers of changes in grassland diversity and species composition. However, most resurveys are based on local or regional data, and hardly reach back more than eight decades. Here, we publish and describe the Historic Square Foot Dataset, comprising 580 0.09‐m2 and 43 1‐m2 vegetation plots carefully sampled between 1884 and 1931, covering a wide range of grassland types across Switzerland. We provide the plots as an open‐access data set with coordinates, relocation accuracy and fractional aboveground biomass per vascular plant species. We assigned EUNIS habitat types to most plots. Mean vascular plant species richness in 0.09 m2 was 19.7, with a maximum of 47. This is considerably more than the present‐day world record of 43 species for this plot size. Historically, species richness did not vary with elevation, differing from the unimodal relationship found today. The data set provides unique insight into how grasslands in Central Europe looked more than 100 years ago, thus offering manifold options for studies on the development of grassland biodiversity and productivity.

Broadleaved trees enhance biodiversity of the understorey vegetation in boreal forests

Understorey vegetation constitutes a remarkable part of the total biodiversity of boreal forests. Mixing broadleaved trees in coniferous forests has been shown to enhance vascular plant abundance and species richness, while high stand density has a counteracting effect. However, more information is needed on how environmental factors modify these biodiversity responses.We investigated how the proportion of broadleaved trees of total basal area, tree species richness, stand density, and shrub cover were reflected in the number of vascular plant species and percentage cover of herbs and bilberry (Vaccinium myrtillus). We also studied the response of site fertility indicators, i.e. C:N ratio and extractable calcium concentration in the soil organic layer, to broadleaved species in mixed-forests.The study was based on the data of understorey vegetation, soil, and stand properties in forests on mineral soil, inventoried on a systematic sample plot network in Finland in 2006. We used a subset of 307 plots in the hemi-southern and middle boreal zones and divided the plots either to xeric or mesic types. We used generalized additive models in analysing the data.Birches (Betula sp.) were the main broadleaved species. Vascular species richness and herb cover generally increased with increasing proportions of broadleaved trees and tree species number both on mesic and xeric sites but decreased with increasing stand density on mesic sites. An increase in proportion of broadleaved trees and stand density resulted in decreased bilberry cover in the southern boreal zone, probably due to stand shading, but in increased cover in the middle boreal zone. Vegetation responses to increasing shrub cover often showed unimodal shape. As increase of proportion of broadleaved trees correlated positively with calcium and negatively with C:N of the organic layer, we suggest that nutrient input from easily decomposable birch leaf litter promotes species richness and herb cover via improved nutrient availability in the soil.Our results indicate that many stand characteristics determining understorey biodiversity can be directed by forest management regimes. Generally, slight increase of broadleaved trees benefitted the understory plant richness, given that stand density is not too high. Because site type and zone controlled many responses, we suggest that it would be beneficial to have habitat and zone-specific instructions in forest management practices that conserve understorey vegetation and its multi-purpose ecosystem services.

Spatial patterns of vascular plant species richness in Poland - a data set

Recognition of species richness spatial patterns is important for nature conservation and theoretical studies. Inventorying species richness, especially at a larger spatial extent is challenging, thus different data sources are joined and harmonized to obtain a comprehensive data set. Here we present a new data set showing vascular plant species richness in Poland based on a grid of 10 × 10 km squares. The data set was created using data from two sources: the Atlas of Distribution of Vascular Plants in Poland and the Polish Vegetation Database. Using this data set, we analysed 2,160 species with taxonomical nomenclature according to the Euro + Med PlantBase checklist in 3,283 squares covering the entire territory of Poland (ca. 312,000 km2). The species were divided into groups according to their status and frequency of distribution, and the statistics for each square were obtained. For purposes of analysis, sampling bias was assessed. The data set promotes theoretical analysis on species richness and reinforces the planning of nature conservations.

Patterns of species richness and beta diversity of vascular plants along elevation gradient in Brazilian páramo

Patterns of species richness and beta diversity of vascular plants along elevation gradient in Brazilian páramo

Recovery of vegetation on former alpine roads: how long does it take?

Alpine areas worldwide are under heavy land‐use pressure and degradation. Active restoration treatments can contribute to accelerating recovery of degraded areas. However, monitoring data are needed to understand the contribution of restoration treatments to long‐term management and to predict time to recovery (TR). In this study, we used monitoring data on removed roads in an alpine area in Norway to investigate TR of three vegetation‐based indicators. Four restoration treatments were tested: 1) removal of added gravel down to original terrain surface, and stirring of topsoil; 2) adding fertilizer to the stirred topsoil; 3) adding seeds to the fertilized topsoil; and 4) no removal of added gravel, but stirring of top layer (gravel and soil). The restoration of roads took place in 2002, and monitoring of permanent plots was carried out in 2004, 2009, 2014, and 2019. Reference plots in intact vegetation next to removed roads were monitored in 2014 and 2019. We used species composition and species richness of vascular plants as well as total vegetation cover as indicators of restoration outcome and investigated predicted TR for these indicators under different restoration treatments. Species composition changed significantly with time since restoration in all treatments, approaching that of the reference vegetation. The recovery of species composition was slowest in fertilized and seeded plots, where estimated TR was 2–3 times longer (> 45 years) than in the other treatments (< 20 years). Species richness of vascular plants was restored quickly (< 5 years) within all restoration treatments, whereas recovery of vegetation cover varied more (20–30 years). Our study confirms that vegetation recovery in alpine environments is a long‐term process, but that adding seeds and nutrients is unnecessary for, and even inhibits, the recovery of narrow, disturbed sites such as former roads.

Rapid response of vascular plants and insects to restoration of montane grasslands

IntroductionIndustrialization has ushered in massive changes in agriculture. Particularly in low mountain ranges, large-scale afforestation with Norway spruce on traditionally managed, semi-natural grasslands has caused a severe decline in biodiversity. Tree removal, hay transfer and resumption of grazing or mowing are typical measures to re-create species-rich grasslands. The aim of this study was to use vascular plants and three insect taxa (leafhoppers, true bugs, and grasshoppers) as bioindicators to evaluate the success of montane grassland restoration on former spruce forests in Central Europe. In addition, we intended to identify the drivers of species richness within the studied grasslands in order to derive suitable recommendations for habitat management.MethodsWe analyzed two different treatments: (i) grazed restoration sites where trees had been cut and species-rich green hay had been applied (N = 9) and (ii) target sites with a long continuity of low-intensity grazing (N = 9).Results and DiscussionOur study revealed that all studied taxa responded rapidly to the restoration measures. After a development period of 3 to 5 years, we found no differences in species richness and diversity of leafhoppers, true bugs and grasshoppers (all, target and threatened species). In addition, non-metric multidimensional scaling showed a large overlap in species composition between restoration and target grasslands. Among target and threatened species, vascular plants displayed the same pattern as insects and reached similar values when comparing the two treatments. However, total species richness and diversity of vascular plants were still higher on the target sites and species composition overlapped only partially. Grazing intensity was the predictor with the highest explanatory power in multivariable (Generalized) Linear Mixed-effects Models, being negatively related to species richness of leafhoppers and true bugs. We conclude that the measures implemented were effective in re-establishing target communities of different taxa. The transfer of seed-containing hay enabled or accelerated the development of the vegetation. Insects, on the other hand, were able to recolonize the restored grasslands on their own, given that these sites were embedded in a network of species-rich grasslands. With regard to insects (e.g., leafhoppers and true bugs), it should be ensured that grazing is applied at low intensity.

High vascular plant species richness in the Usumacinta River Basin: a comprehensive floristic checklist for a natural region in the Mesoamerican biodiversity hotspot

Background: Mesoamerica is one of the most important biodiversity hotspots on the planet. Despite significant efforts made over two centuries to contribute to the floristic knowledge of this region, our understanding of its flora is still scattered and uneven.
 Questions: What is the magnitude of the vascular plant species richness in the Usumacinta River Basin?
 Study site and dates: Usumacinta River Basin (Guatemala and Mexico), 1838-2018.
 Methods: We compiled the checklist by systematizing the floristic information acquired from various sources derived from numerous floristic and ecological studies.
 Results: We recorded 6,977 species, 1,892 genera and 274 families. The largest numbers of species (5,746) and records (58,859) correspond to the Mexican portion of the Usumacinta River Basin, compared to its Guatemalan counterpart (4,445 species and 19,952 records). The most species-rich families were Orchidaceae (598 species), Fabaceae (512), and Asteraceae (476). The prevalence of these and all other families with significant contributions to the flora varied among three elevation-defined sectors into which the Usumacinta River Basin was subdivided (lower, middle, and upper basin).
 Conclusions: The Usumacinta River Basin is a strategic region for plant biodiversity conservation as it hosts almost one third of all vascular plant species known for Mesoamerica and ca. 6 % of the entire flora in the Americas. Further botanical exploration should focus on those areas of the basin for which little or no information is available in order to gain a better appreciation of its flora.

The effect of grassland type and proximity to the city center on urban soil and vegetation coverage

Urban soils with associated vegetation are important components of urban ecosystems, providing multiple regulating and supporting ecosystem services. This study aimed to analyze the differences in the soil chemistry and vegetation of urban grasslands considering urbanization gradient and urban grassland type (UGT). We hypothesized that the chemical properties of soil, such as metal content, as well as vegetation traits, differ according to grassland type (lawns, grasslands in parks, grasslands on river embankments, and roadsides) and the location of grassland patches (city center versus peripheries). Our samples included 94 UGT patches which each patch represented by four square sampling plots sized 1 m2. The results showed high differentiation of measured traits unrelated to UGT and location. The exception was K content, with a relatively high concentration in lawns, and some metals (Cd, Cu, Pb, Zn), with higher concentrations in the city center than in the peripheries. We found two grassland patches located in the city center where the concentrations of Pb, Zn, and Cu exceeded the level authorized by Polish standards. In the case of vegetation traits, the variability was not structured considering the UGT and location of the patches, except for bare soil cover, which was higher in lawns in the city center compared to embankments in the peripheries. We observed correlations between vegetation traits and soil chemical properties. The vascular plant species richness decreased when N, P, and C content, along with an increase in grass cover and a decrease in herbs.

Forest age and topographic position jointly shape the species richness and composition of vascular plants in karstic habitats

Key messageDolines may provide important safe havens for many plant species and play a key role in maintaining biodiversity. The combined effects of forest age and topographic position influence the biodiversity patterns of these unique habitats. Forest managers, conservationists, and researchers need to work together in order to maintain the species richness and composition of these habitats under environmental changes.ContextDolines are the most prominent geomorphological features in many karst landscapes that may provide important microhabitats for many species.AimsWe aim to contribute to a better understanding of how forest age and topographic position influence the plant species richness and composition of vascular plants within doline habitats.MethodsWe studied the effects of forest age (four age classes: from 5- to 10-year-old stands to more than 90-year-old stands), topographic position (south-facing slope, bottom, and north-facing slope), and their interaction on the distribution of vascular plants and mean Ellenberg indicator values in dolines using detrended correspondence analysis and mixed-effects models. Diagnostic species for the forest age classes and topographic positions were also determined.ResultsDifferent groups of vascular plant species usually showed significant preferences for certain topographic positions and/or forest age classes in dolines. In general, the number of species in all studied groups of plants increased after a few years of canopy removal. The number of plant species in almost all groups was lowest in dolines covered with 40–45-year-old forests. The moist and nutrient-rich doline bottoms covered with 90–120-year-old forests harboured many climate change vulnerable plant species.ConclusionsForest age and topographic position considerably influence the species richness and composition of vascular plants in dolines; therefore, forest managers and conservationists need to consider their potential impacts when evaluating the effects of climate warming on karst landscapes.

How arsenic contamination influences downslope wetland plant and microbial community structure and function

Mine tailings are prevalent worldwide and can adversely impact adjacent ecosystems, including wetlands. This study investigated the impact of gold (Au) mine tailings contamination on peatland soil and pore water geochemistry, vegetation and microbial communities, and microbial carbon (C) cycling. Maximum arsenic (As) concentrations in peat and pore water reached 20,137 mg kg−1 and 16,730 μg L−1, respectively, but decreased by two orders of magnitude along a 128 m gradient extending from the tailings into the wetland. Carbon and other macronutrient (N, P, K) concentrations in peat and pore water significantly increased with distance from contamination. Relative percent cover and species richness of vascular and non-vascular plants significantly increased with distance into the wetland, with higher non-vascular richness being found at intermediate distances before transitioning to a vascular plant dominated community. Bacterial and archaeal community composition exhibited a decreased proportion of members of the phylum Acidobacteria (notably of the order Acidobacteriales) and increased diversity and richness of methanogens across a larger range of orders farther from the tailings source, an indication of microbial C-cycling potential. Consistent with changes in microbial communities, in vitro microbial CH4 production potential significantly increased with distance from the contaminant source. This study demonstrates both the profound negative impact that metalliferous tailings contamination can have on above and belowground communities in peatlands, and the value of wetland preservation and restoration.

Area, environmental heterogeneity, scale and the conservation of alpine diversity

AbstractAimArea and environmental heterogeneity together explain most patterns of species diversity but disentangling their relative importance has been difficult. Here, we empirically examined this relationship and parsed their relative importance, and that of the heterogeneity—effective area trade‐off, at different spatial scales and in different spatial representations in simulations.LocationAlpine grasslands of 23 mountain ranges of southern and central Europe.TaxonVascular plants.MethodsWe developed metrics of climatic and edaphic heterogeneity, using principal components analyses and the shoelace algorithm, and added elevation range. We applied commonality analysis to partition the unique and shared explanation of the observed vascular plant species richness among selected metrics. A simulation was developed to separate the relative importance of area and heterogeneity at different extents and representations of spatial nestedness, and the heterogeneity—effective area trade‐off was evaluated by altering spatial discreteness.ResultsThe explanation of the observed regional richness was shared by area and heterogeneity. The simulation revealed that heterogeneity was consistently more important, but less so among smaller areas. This qualitative pattern was maintained regardless of whether and how nestedness was represented. The heterogeneity–effective area trade‐off occurred in a few simulations of more discrete habitats.Main ConclusionsScale dependence may account for discrepancies among past empirical studies wherein environmental heterogeneity has usually outweighed area in the explanation of species richness; and it is not affected by nestedness. The potential heterogeneity–effective area trade‐off may be limited to locations where the environmental heterogeneity is quite discrete or if the added environment is beyond the niches of any species in the potential pool. The significant importance of area per se in small territories indicates that microrefugia, even with an unlikely full range of heterogeneity, will suffer local extinctions in the face of climate change.

Ancient settlements as natural heritage sites: the first occurrence dataset on vascular plant species from ancient settlements in the Lower Dnipro region (Ukraine).

This work is a long-term outcome of an international Ukrainian-Polish teamwork, aiming to assess the role of ancient settlements for steppe conservation and protection. The dataset contains georeferenced occurrences of vascular plant species on 18 ancient settlements (Lower Dnipro, southern Ukraine), collected during the 2015-2020 period. Additionally, to the total species list, the publication presents the taxonomic coverage (according to GBIF Backbone Taxonomy), the frequency classes of occurrences of the total taxa and the floristic differences amongst studied sites. The report also shows the high sozological value of the studied ancient settlements, the high levels of vascular plant species richness and the various means of the plant species protection (according to the Bern Convention, the Red Data Book of Ukraine and regional Red Lists). This work provides the first occurrence dataset from ancient settlements in Ukraine. The dataset includes 3,210 occurrences of vascular plants recorded during the study period of 2015-2020 conducted in the Lower Dnipro region. As ancient settlements were generally considered as steppe refuges, great attention was paid to the native steppe species, as well as to the rare components of the flora. The dataset includes 1,525 occurrences of steppe species and 87 occurrences of rare species, respectively. The dataset could be useful for further research of ancient settlements` floristic richness, but also analyses and comparison with other objects of cultural origin (e.g. kurgans, hillforts, old cemeteries, forgotten parks, sacred groves etc.).

Ecologically relevant canopy openness from hemispherical photographs

Canopy openness determines forest biodiversity, radiation regime and understorey microclimate. Traditionally, canopy openness was calculated from hemispherical photographs with a full 180° angle of view, but photographic equipment providing only narrower angles of view is increasingly used. Despite that, it is unknown how well canopy openness estimated from restricted angles of view predicts different forest characteristics. To fill this gap, we explored how different canopy openness estimates predicts vascular plant species richness and composition, in-situ measured air and soil temperature and photosynthetically active radiation across different types of European deciduous broadleaved forests. We further benchmarked performance of canopy openness against radiation site factors and evaluated accuracy of canopy openness calculation using artifitial calibration targets.Canopy openness calculated from angles of view < 180° was a better predictor of all measured variables than canopy openness from the whole hemispherical photograph. Openness from 80° - 120° angle of view best explained plant species richness, community composition, in-situ measured air and soil temperatures, and the photosynthetically active radiation. Moreover, canopy openness from a 100° angle of view predicted all variables except maximum air temperature better than the total radiation site factor. Finally, canopy openness calculated from angles of view < 120° was less affected by image quality and therefore more comparable between different photographic equipment including smartphones with an external fisheye lens.We found that canopy openness from a complete hemisphere is not required for many ecological applications. Therefore, many consumer-grade cameras and smartphones with an external fisheye lens can provide ecologically relevant canopy openness. Nevertheless, specialized cameras and fisheye lenses should still be preferred. Finally, researchers can predict plant assemblages, forest microclimate and understorey radiation regimes better if they calculate canopy openness from ∼100° angle of view rather than from the whole hemispherical photograph.

Subalpine vegetation changes in the Eastern Sudetes (1973–2021): Effects of abandonment, conservation management and avalanches

AbstractAimsThe summit grasslands of many European mountain ranges were historically used for summer grazing, which ceased in the 20th century. These grasslands are changing, partly through succession after abandonment and partly owing to environmental changes. Subalpine vegetation is also affected by artificially reduced avalanche frequency. Recent conservation efforts have attempted to reverse the negative trends of change. We ask: (1) How has subalpine vegetation changed following the abandonment and avalanche control? (2) Was conservation management able to reverse the post‐abandonment trend of vegetation change? (3) Did avalanche disturbance have a positive effect on plant species diversity?LocationSummit area of the Hrubý Jeseník Mountains (1,491 m a.s.l.), Eastern Sudetes, Czech Republic.MethodsVegetation plots sampled in the 1970s were resurveyed in the 2000s and again in 2021. Subalpine vegetation was classified into six types, and transitions between these types over time were quantified. Vascular plant species richness and the proportion of threatened species were compared between periods, between areas with and without conservation management, and between areas affected vs unaffected by a large avalanche from 2019. Species composition was analysed using principal coordinate analysis and distance‐based redundancy analysis.ResultsVegetation types remained relatively stable except for species‐rich grasslands, some of which changed to heathlands or tall‐forb vegetation. Some competitive species have increased, and species specialized to threatened habitats declined. Conservation management systematically implemented after 2010 slowed the decline of habitat‐specialized species but did not reverse it. Disturbance by an avalanche positively affected species richness but not the number of threatened species.ConclusionsSubalpine vegetation is slowly losing its plant diversity owing to grazing cessation and possibly acidification from past atmospheric deposition. Recently implemented conservation management and restoration of avalanche activity are essential to stop this trend, but future monitoring is needed to evaluate the success of management actions.

The diversity of resident passerine bird in the East Yunnan-Kweichow Plateau is closely related to plant species richness, vertical altitude difference and habitat area.

East Yunnan-Kweichow Plateau is rich in biodiversity in China. Complex geographical and climatic conditions and rich bird resources made this area an ideal system for studying the spatial distribution mechanism and influencing factors of birds, which were still unknown. Bird community data from 37 sites in this region were collected, including 505 bird species and 164 species of resident passerine bird, were extracted for analysis. The taxonomic diversity, phylogenetic diversity, functional diversity (FD), and community structure index were calculated. Ordinary least square (OLS), spatial autoregressive models (SAR), and structural equation model (SEM) were used to explore the relationship between bird diversity index and environmental factors which were used to describe the habitat conditions of birds. Results indicated that species richness (SR), phylogenetic diversity (PD), and FD have similar distribution patterns and are mainly affected by vascular plant species richness, habitat area, and vertical altitude difference. The phylogenetic and functional structure of bird community changed in both longitude and latitude direction, and the phylogenetic structure of community was dispersed in the west and clustered in the east, significantly related to habitat area, and vertical altitude difference, the functional structure was dispersed in all sites, significantly related to average annual precipitation. The community in the west and south of the East Yunnan-Kweichow Plateau is mainly driven by interspecific competitive, while the process in the east and north is mainly driven by environmental filtration. Distribution pattern of bird diversity was caused by the comprehensive action of various habitat factors which were mainly related to food availability and habitat heterogeneity. For maintaining the living space of birds, the protection of urban parks, wetland parks, campuses, and other urban green spaces is as important as national and provincial nature reserves. Revealing the construction mechanism and main influencing factors of bird communities in different areas is conducive to targeted protection work.

Fossombronia bracchia Cargill (Fossombroniaceae, Marchantiophyta), a new species from Western Australia

The new species, Fossombronia bracchia, from Lesueur National Park, an area of high vascular plant endemism and species richness in southwestern Western Australia, is described and illustrated; a distribution map is provided. The new species has strong morphological similarities to the South African species F. tumida.

The spatial influences of organic farming and environmental heterogeneity on biodiversity in South Australian landscapes

The potential link between certified organic farming and biodiversity and conservation remains unexplored in Australia, despite the country having the world's largest amount of certified organic farmland and unprecedented biodiversity loss. This study modelled the spatial effects of organic farming (intensity of local farming systems), environmental heterogeneity, and urbanisation on two widely studied environmental taxa — vascular plant and bird species richness (surrogate measures of biodiversity) — in South Australia, using a unique certified organic farming postcode level dataset from 2001 to 2016 (N = 5440). The spatial Durbin error model results confirmed the positive spatial congruence of organic farming with greater vascular plant species richness, whereas only weak to no significant evidence was found for bird species richness. Landscape features (habitat heterogeneity) and green vegetation (a proxy indicator of resource availability) – rather than organic farming – appeared to be most associated with bird species richness. Both plant and bird species richness were positively associated with habitat heterogeneity (land cover diversity and elevation range), plant productivity and proportion of conservation land and water bodies. Whereas, increased anthropogenic land use for cropping and horticultural farming, soil type diversity and proximity to the coast significantly reduced species richness of both taxa. The results suggest that a multi-scale spatially refined biodiversity conservation strategy, with spatial targeting that promotes low intensive farming systems and increases landscape heterogeneity to provide quality habitat (a whole of landscape approach by incorporating private agricultural landholders), could be beneficial for biodiversity conservation.

Land-use intensification reduces multi-taxa diversity patterns of Small Woodlots Outside Forests in a Mediterranean area

Land-use intensification exacerbates landscape fragmentation, increasing the negative effects on biodiversity. In this context, the biodiversity value of Trees Outside Forests (TOF; scattered trees, tree lines and small woodlots) is often overlooked by landscape planning and conservation programs, which typically focus on protecting larger and more intact areas. More empirical studies on taxa inhabiting TOF are needed to support and promote their conservation in human-altered lands.However, we are not aware of any study focusing on multiple taxa living in small woodlots outside forests (SWOFs) in the Mediterranean basin. We investigated how diversity patterns of multiple taxa in SWOFs respond to a land-use intensification gradient, from natural areas to more disturbed ones (agricultural and urban areas), in a Mediterranean biodiversity hotspot.We explored the influence of land-use types on species richness and composition of vascular plants and six ground-dwelling invertebrate groups (pseudoscorpions, spiders, darkling beetles, rove beetles, ground beetles, and ants). Species composition was more sensitive than species richness to land-use change, highlighting the need to consider a suitable measure for interpreting ecological processes. We observed a strong influence of land use embedding SWOFs on the mean composition and beta diversity of taxa: land-use intensification led to a general homogenization of diversity patterns, especially among agricultural and urban areas. In our study area, vascular plants responded more sensitively to land-use change than invertebrates. For most invertebrates: the higher the land-use intensity, the lower the species composition dissimilarity due to the dominance of good dispersers or disturbance-tolerant species. More vagile species and disturbance-tolerant species can move across open habitats and colonize new areas, reducing compositional differences and potentially boosting species pools. We demonstrated that SWOFs play a key role in supporting viable populations of invertebrates, also in human-altered lands, underlining the need to promote their conservation in this Mediterranean fragmented landscape to avoid homogenization from driving a generalized biodiversity loss.

Interactive effects of precipitation and above canopy nitrogen deposition on understorey vascular plants in a jack pine (Pinus banksiana) forest in northern Alberta, Canada

Elevated nitrogen (N) deposition in the bituminous sands region of northern Alberta, Canada is localized but expected to increase over time. Here we seek to determine the effects of above canopy N deposition on understorey vascular plants in a jack pine (Pinus banksiana) stand in a five-year experimental study. Aqueous N (ammonium nitrate) was applied four times annually (May through October) via helicopter above the canopy between 2011 and 2015 across a narrow but environmentally relevant N deposition gradient (0, 5, 10, 15, 20 and 25 kg N ha−1 yr−1). Changes in vascular plant species richness, diversity and total vascular cover were best explained by throughfall water flux, but the positive responses to precipitation decreased with increasing N application. Arctostaphylos uva-ursi and Maianthemum canadense showed positive cover increases in wet years; however, the positive cover expansion at ≥5 kg N ha−1 yr−1 treatments was suppressed relative to controls. Total cover expansion was muted in low precipitation years in treatments ≥10 kg N ha−1 yr−1. In contrast, Vaccinium vitis-idaea cover changes ≥10 kg N ha−1 yr−1 were consistently negative. There were no differences in soil net N mineralization rates, plant foliar N or NO3− leaching among treatments. We conjecture the extensive moss/lichen layer of the forest floor that accumulates most of incoming N in throughfall allows them to outcompete vascular plants for water during higher precipitation years, effectively reducing vascular cover expansion relative to controls. This work suggests the response of vascular plants in xeric jack pine ecosystems may interact with climate and these interactions should be considered in risk assessment studies.