Floristic distinctiveness and endemic richness of woody plants highlight the biodiversity value of the herriza among all Mediterranean heathlands

Background: Heathlands are relatively abundant in the landscape of the western Mediterranean region, especially in the Strait of Gibraltar region, where it is locally known as herriza. They are associated with a mild Mediterranean climate regime and with acid, nutrient-poor soils. They harbour a high plant diversity, often viewed as a consequence of the transition between European Atlantic heathland and Mediterranean sclerophyllous shrubland floras.

Aims: To determine whether species-rich Mediterranean heathlands, including the herriza, constitute distinct heathland formations rather than transitional vegetation units between Atlantic heathlands and Mediterranean garrigue shrublands.

Methods: We quantified species richness, endemism and analysed the β-diversity of the woody component of Mediterranean heathland communities throughout its geographic range, with special emphasis on the Strait of Gibraltar region.

Results: Mediterranean heathlands, including the herriza, are not transitional communities between Atlantic heathlands and Mediterranean shrublands. Woody species richness and, particularly, endemic richness was the highest in the herriza.

Conclusions: The high biodiversity values of the herriza are a likely consequence of the ecological singularity of the Strait of Gibraltar region and its known role as a glacial refugium. Despite its treeless feature, the herriza deserves special recognition and protection from both in its European and North African extension.     

Flower resource and land management drives hoverfly communities and bee abundance in seminatural and agricultural grasslands

Pollination is a key ecosystem service, and appropriate management, particularly in agricultural systems, is essential to maintain a diversity of pollinator guilds. However, management recommendations frequently focus on maintaining plant communities, with the assumption that associated invertebrate populations will be sustained. We tested whether plant community, flower resources, and soil moisture would influence hoverfly (Syrphidae) abundance and species richness in floristically‐rich seminatural and floristically impoverished agricultural grassland communities in Wales (U.K.) and compared these to two Hymenoptera genera, Bombus, and Lasioglossum. Interactions between environmental variables were tested using generalized linear modeling, and hoverfly community composition examined using canonical correspondence analysis. There was no difference in hoverfly abundance, species richness, or bee abundance, between grassland types. There was a positive association between hoverfly abundance, species richness, and flower abundance in unimproved grasslands. However, this was not evident in agriculturally improved grassland, possibly reflecting intrinsically low flower resource in these habitats, or the presence of plant species with low or relatively inaccessible nectar resources. There was no association between soil moisture content and hoverfly abundance or species richness. Hoverfly community composition was influenced by agricultural improvement and the amount of flower resource. Hoverfly species with semiaquatic larvae were associated with both seminatural and agricultural wet grasslands, possibly because of localized larval habitat. Despite the absence of differences in hoverfly abundance and species richness, distinct hoverfly communities are associated with marshy grasslands, agriculturally improved marshy grasslands, and unimproved dry grasslands, but not with improved dry grasslands. Grassland plant community cannot be used as a proxy for pollinator community. Management of grasslands should aim to maximize the pollinator feeding resource, as well as maintain plant communities. Retaining waterlogged ground may enhance the number of hoverflies with semiaquatic larvae.     

Plant richness and composition in hardwood forest understories vary along an acidic deposition and soil-chemical gradient in the northeastern United States

Aims

A century of atmospheric deposition of sulfur and nitrogen has acidified soils and undermined the health and recruitment of foundational tree species in the northeastern US. However, effects of acidic deposition on the forest understory plant communities of this region are poorly documented. We investigated how forest understory plant species composition and richness varied across gradients of acidic deposition and soil acidity in the Adirondack Mountains of New York State.

Methods

We surveyed understory vegetation and soils in hardwood forests on 20 small watersheds and built models of community composition and richness as functions of soil chemistry, nitrogen and sulfur deposition, and other environmental variables.

Results

Community composition varied significantly with gradients of acidic deposition, soil acidity, and base cation availability (63% variance explained). Several species increased with soil acidity while others decreased. Understory plant richness decreased significantly with increasing soil acidity (r?=?0.60). The best multivariate regression model to predict richness (p?<?0.001, adjusted-R²?=?0.60) reflected positive effects of pH and carbon-to-nitrogen ratio (C:N).

Conclusions

The relationship we found between understory plant communities and a soil-chemical gradient, suggests that soil acidification can reduce diversity and alter the composition of these communities in northern hardwood forests exposed to acidic deposition.

     

Grazing effects on plant diversity in the endemic Erica mackayana heathland community of north-west Spain

Background: Large areas of heathland landscapes in Galicia, north-west Spain, have traditionally been extensively grazed by free-ranging cattle and wild ponies. Recently, a large reduction in the number of these larger herbivores has been observed, with unknown consequences for the habitat.

Aims: To evaluate the effects of grazing and herbivore density on plant diversity, community composition and vegetation structure of the endemic wet heathlands dominated by Erica mackayana in Galicia.

Methods: Field sampling of vascular plants, generalised linear models (GLMs), non-metric multidimensional distance scaling (NMDS).

Results: Grazed sites had significantly higher total and rare species richness and diversity than ungrazed sites. Higher densities of cattle resulted in lower numbers of rare species, while wild pony density had no effect on rare species richness. In grazed sites, vegetation was lower with greater variation in height, resulting in greater heterogeneity of the habitat. Precipitation and summer temperatures were related to plant diversity, mainly beta diversity. Soil organic matter negatively correlated with rare species.

Discussion: Grazing, mostly by wild ponies, was demonstrated to be positively related to plant diversity and vegetation structure. Lack of grazing or high cattle densities resulted in a negative effect on total and rare species richness and diversity. Future climate change may negatively affect heathland plant diversity. Galician wild ponies represent a unique case of sustainable management of a wild species and an invaluable cultural heritage. Moreover, they have a significant role in maintaining the endemic E. mackayana heathlands, what would justify specific conservation actions for these large herbivores.     

Floristic diversity and the richness of locally endangered plant species of semi-natural grasslands under different management practices,southern Kyushu,Japan

Background: The rapid decline of semi-natural grasslands in Japan threatens many relic and endemic plant species. There is insufficient knowledge on how the impacts of land-use changes and management of grasslands have been affecting grassland ecosystems and what conservation measures may be taken to conserve as much of the existing plant diversity as possible.

Aim: We assessed the existing management regimes for their suitability for conserving Red Data Book (RDB) species.

Methods: We conducted our study in four districts of Kushima, Kyushu, south-west Japan, with different land-use histories. We compared species richness, plant density and abundance in six grassland types: regularly burnt, regularly mown, paddy levee, roadside, landslip and wetland communities in a total of 289 1 m x 1 m quadrats, recorded in172 grassland patches. Species richness plant density and abundance were analysed with special reference to RDB species under different land use history.

Results: Species richness of grasslands did not differ across different land use histories, yet our analysis showed that the reduced area of grasslands markedly affected the density of RDB species. Grassland types differed in their ability to support RDB species: regularly burnt grasslands were the richest in RDB species and poorest in alien species, followed by regularly mown grasslands, paddy levees, landslip, wetland and roadside communities.

Conclusions: Traditional management regimes, such as regular burning or mowing of grasslands have the best potential for conserving RDB species, and thus should be part of conservation management practices of semi-natural grasslands.     

Influence of soil and microclimate on species composition and grass encroachment in heath succession

Aims and Methods Mostly due to land use changes, European heathlands have become increasingly rare. In addition, the increasing amount of atmospheric nitrogen deposition has resulted in an encroachment of grasses and a loss in species diversity. Despite many investigations, information about the precise environmental parameters that determine the development and maintenance of heathland vegetation is still insufficient. In order to determine the environmental factors that control heath succession and grass encroachment, and to develop appropriate management schemes, we studied the influence of several soil and microclimate parameters on species composition and vegetation characteristics in five successional stages in a coastal heathland on the island of Hiddensee, north-east Germany, where the encroachment of Carex arenaria has become a major problem.Important findings We recorded the highest plant species richness in grey dune and birch forest plots, while the encroachment of C. arenaria let to a significant decline in plant species richness. The most important environmental factors influencing species richness and distribution of single species were microclimate, soil moisture, soil pH and the C/N ratio. While many studies reported the importance of differences in nutrient availability, we found no significant correlations between soil nutrient availability and vegetation pattern. Environmental conditions in dense C. arenaria stands, especially soil properties (e.g. soil pH), showed great differences in comparison to the other successional stages. However, no correlations between the encroachment of C. arenaria and single environmental factors were found. Our results show that not only soil nutrients are important abiotic factors in heaths but that also microclimate and soil moisture play an important role and that many factors are involved in heath succession and in the promotion of grass encroachment. Management plans for the conservation and restoration of heathlands should therefore focus on the specific site conditions and should take several abiotic and biotic factors into account.     

Vegetation change in acidic dry grasslands in Moravia (Czech Republic) over three decades: Slow decrease in habitat quality after grazing cessation

Aims

Shallow soils on acidic bedrock in dry areas of Central Europe support dry grasslands and heathlands that were formerly used as extensive pastures. These habitats are of high conservation value, but their abandonment in the 20th century triggered slow natural succession that poses a threat to specialized plant species. We asked how this vegetation and its plant diversity have changed over the past three decades and whether protected areas have positively affected habitat quality.

Location

Southwestern and central Moravia, Czech Republic.

Methods

In 2018–2019, we resurveyed 94 vegetation plots first sampled in 1986–1991 at 47 acidic dry grassland and heathland sites. We compared the number of all vascular plant species, Red List species and alien species per plot using parametric and non-parametric tests, life-form spectra using the chi-square test, species composition using detrended correspondence analysis, and indicator values using a permutation test. We also compared these changes between sites within and outside protected areas.

Results

Vegetation changes over the past three decades have been relatively small. However, we detected a decrease in total species richness, the number of Red List species and the number of characteristic species of dry grasslands. Neophytes were infrequent, while archaeophytes increased slightly. The competitive tall grass Arrhenatherum elatius, annual species and young woody plants increased in abundance or newly established at many sites. Indicator values did not change except for a slight increase in nutrient values. These negative trends occurred both within and outside protected areas but were more pronounced outside.

Conclusions

Formerly grazed acidic dry grasslands and heathlands in Moravia are slowly losing habitat specialists, including threatened plant species, and are increasingly dominated by Arrhenatherum elatius. Conservation management, especially cutting in protected areas, slows down the negative trends of decline in plant diversity and habitat quality but is insufficient to halt these processes completely.     

Plant communities,species richness and their environmental correlates in the sandy heaths of Little Desert National Park,Victoria

Plant community composition and its likely environmental controls were investigated for 200 sample plots (each 100 m²) from Mediterranean-type vegetation in the Little Desert National Park, Victoria. TWINSPAN classification revealed four readily identifiable vegetation types; mallee-broombush, heathland, stringybark open woodland, and an assemblage intermediate between mallee-broombush and heathland referred to here as broom-heath. Mallee-broombush was found on Parilla Sands characterized by high Ca levels relative to heathland and stringybark open woodlands on unconsolidated Lowan Sands. The first axis of a 2 dimensional non-metric MDS ordination also divided heathlands (high axis scores) from mallee-broombush (low scores), while the second separated these vegetation types from stringybark woodlands and broom-heath. Vector-fitting revealed significant correlations between the locations of samples in ordination space and exchangeable soil Ca, soil colour, aspect and Shannon–Weiner diversity. Highest species richness/diversity was associated with the ecotonal area between Parilla and Lowan Sands (i.e. broom-heath) where a number of species characteristic of different assemblages had overlapping ranges. The fire-sensitive conifer, Callitris rhomboidea, was preferentially located in stringybark woodland and broom-heath vegetation types. Its presence was positively associated with high species richness and aspects having a southerly component. Four Callitris stands sampled for population structure were all > 40 years old and showed evidence of interfire recruitment from seeds released by old, serotinous cones. Overall, results suggest that variations in plant community composition and structure in the eastern block of the Little Desert are primarily due to variations in soil properties associated with the distribution of the two dominant substrate types, Parilla Sand and Lowan Sand. However, the interplay of topography and fire behaviour has probably been more important than substrate type in determining the distribution and population structure of longer-lived, fire-sensitive species such as Callitris rhomboidea.     

The Relation Between Unpalatable Species, Nutrients and Plant Species Richness in Swiss Montane Pastures

In agriculturally marginal areas, the control of unpalatable weeds on species rich pastures may become problematic due to agricultural and socio-economic developments. It is unclear how increased dominance of unpalatable species would affect the botanical diversity of these grasslands. We investigated whether there was any relationship between plant species diversity and the abundance of unpalatable species and whether soil conditions affected this relationship. In three species-rich montane pastures in western Switzerland, we related plant species richness to soil attributes, the relative cover of all unpalatable species and the relative cover of the locally dominant, toxic Veratrum album in 25 plots of 4 m². We furthermore determined species richness in small transects through patches of V. album. Species richness was significantly lower in and near (≤ 0.3 m) patches of V. album. At the field scale, plant species richness was best described by total soil N:P ratio (positive relation) in one site and the relative abundance of unpalatable species (negative relation) and soil N:P ratio (positive relation) in a second site. In the third site, species richness was not significantly related to any measured variable. Vegetation diversity (Simpson's D) was negatively related to the relative abundance of unpalatable species in one site and positively related to pH in another site. The results suggest that no single factor can explain plant species richness and diversity in montane pastures. At very high densities unpalatable species can have adverse effects but soil nutrient status appears to be a more general determinant of plant species richness. Conservation efforts should give priority to the prevention of intensification of these pastures.     

Salt spray and edaphic factors maintain dwarf stature and community composition in coastal sandplain heathlands

North American coastal sandplain heathlands are unique in species composition and vegetation, but the extent to which edaphic factors influence the structure of these communities is currently debated. It was hypothesized that salt spray and edaphic factors maintain the dwarf stature and community composition of heathlands by limiting plant growth and excluding competitively dominant woody species close to the ocean. Field surveys were carried out to investigate the spatial patterns of salt spray accumulation, soil salt and soil moisture. High salt spray correlated significantly with increased leaf necrosis and water stress in Myrica pensylvanica and with decreased plant height. Plant community composition changed across a salt spray and soil gradient, as well. Distinctive sub-communities were identified that separated according to soil salt and soil moisture but salt spray was the main factor affecting sites occupied only by heathland vegetation. Results from this study suggest that salt spray suppresses the growth of heathland plants in close proximity to the ocean, and therefore maintains the low stature in these dwarf shrublands. This research also demonstrates that the physical environment influences the community structure in heathlands, particularly by limiting tree species from growing in high salt spray, low water availability sites.     

The consequences of multiple resource shifts on the productivity and composition of alpine tundra communities: inferences from a long-term snow and nutrient manipulation experiment

Background: Gradients in the amounts and duration of snowpack and resulting soil moisture gradients have been associated with different plant communities across alpine landscapes.

Aims: The extent to which snow additions could alter plant community structure, both alone and in combination with nitrogen (N) and phosphorus (P) additions, provided an empirical assessment of the strength of these variables on structuring the plant communities of the alpine tundra at Niwot Ridge, Colorado Front Range.

Methods: A long-term snow fence was used to study vegetation changes in responses to snowpack, both alone and in conjunction with nutrient amendments, in plots established in dry and moist meadow communities in the alpine belt. Species richness, diversity, evenness and dissimilarity were evaluated after 20 years of treatments.

Results: Snow additions, alone, reduced species richness and altered species composition in dry meadow plots, but not in moist meadow; more plant species were found in the snow-impacted areas than in nearby controls. Changes in plant community structure to N and N + P additions were influenced by snow additions. Above-ground plant productivity in plots not naturally affected by snow accumulation was not increased, and the positive responses of plant species to nutrient additions were reduced by snow addition. Plant species showed individualistic responses to changes in snow and nutrients, and indirect evidence suggested that competitive interactions mediated responses. A Permanova analysis demonstrated that community dissimilarity was affected by snow, N, and P additions, but with these responses differing by community type for snow and N. Snow influenced community patterns generated by N, and finally, the communities impacted by N + P were significantly different than those affected by the individual nutrients.

Conclusions: These results show that changes in snow cover over a 20-year interval produce measureable changes in community composition that concurrently influence and are influenced by soil nutrient availability. Dry meadow communities exhibit more sensitivity to increases in snow cover whereas moist meadow communities appear more sensitive to N enrichment. This study shows that the dynamics of multiple limiting resources influence both the productivity and composition of alpine plant communities, with, species, life form, and functional traits mediating these responses.     

Plant community response to nitrogen and phosphorus enrichment varies across an alpine tundra moisture gradient

Background: The extent to which nutrient availability influences plant community composition and dynamics has been a focus of ecological enquiry for decades.

Aims: Results from a long-term nitrogen (N) and phosphorus (P) addition experiment in alpine tundra were used to evaluate the importance of the two nutrients in structuring plant communities in three communities that differed in their snow cover amounts and duration and soil moisture characteristics.

Methods: A factorial N and P experiment was established in three meadows differing in initial vegetation composition and soil moisture. Plant and soil characteristics were measured after 20 years, and the dissimilarity among meadows and treatments were measured using permutational analysis of variance.

Results: Plant species richness declined uniformly across the three meadow types and in response to N and N + P additions, while both evenness and the Shannon diversity index finding indicated that nutrient additions had the highest impact on moister habitats. Overall, N impacts overshadowed changes attributed to P additions, and the N and N + P plots in wet meadow sites were the least diverse and scored the lowest dissimilarity averages among treatments. Dissimilarity estimates indicated that the control and P plots in the dry meadow community were more distinct in composition than all other plots, and especially those in the moist or wet meadows. Above-ground biomass of grasses and sedges (graminoids) increased with N additions while forbs appeared to show responses dictated in part by the graminoid responses. The most abundant grass species of moist and wet meadow, Deschampsia cespitosa, dominated N and N + P plots of the wet sites, but did not show a N response in moist areas in spite of its general abundance in moist meadow. Competition from other plant species in the moist areas likely diminished the D. cespitosa response and contributed to the resilience of the community to nutrient enrichment.

Conclusions: Initial community composition, as influenced by the specific moisture regime, appears to control the extent to which changes in nutrient resources can alter plant community structure. Long-term fertilization tends to support most but not all findings obtained from shorter-termed efforts, and wet meadows exhibit the largest changes in plant species numbers and composition when chronically enriched with N.     

Distribution and decline of endangered herbaceous heathland species in relation to the chemical composition of the soil

High atmospheric deposition of ammonium affects the physical and chemical status of the soil, increasing nitrogen availability, soil acidity and the mobilization of toxic metal ions. To investigate whether and how the decline of several herbaceous plant species in Dutch heathlands is associated with these processes, the chemical composition of the soil on which these species grow has been compared with the soil on which heathland species such asCalluna vulgaris (L.) Hull,Erica tetralix L. andMolinea caerulea (L.) Moench dominate. The discrimination between both soil types was primarily based on differences in pH (H₂O), pH (NaCl) and the aluminium/calcium ratio in the waterextracts. Within the group of endangered herbaceous heathland species these soil parameters also varied. This led to a division into 4 groups of species:

u

Dominating species growing on acid soils

Herbaceous species growing together with dominating species on acid soils

Herbaceous species growing together with dominating species on moderately acid soils

Herbaceous species growing together with dominating species on weakly acid soils.

This study indicated that, unlike the decline of heather species, the decline of herbaceous species is not likely to be due to increased competition from grass species as a result of eutrophication. Soil acidification and the changed mineral balance in the soil are most likely to be responsible for the decline of all three groups of herbaceous plant species. ei]R F Huettl     

Scale-dependent effects of land use on plant species richness of mountain grassland in the European Alps

Traditionally managed mountain grasslands in the Alps are species‐rich ecosystems that developed during centuries of livestock grazing. However, changes in land use including fertilisation of well accessible pastures and gradual abandonment of remote sites are increasingly threatening this diversity. In five regions of the Swiss and French Alps we assessed the relationship between land use, soil resource availability, cover of the unpalatable species Veratrum album, species richness and vegetation composition of mountain grasslands across four spatial scales ranging from 1 to 1000 m². Mean species richness and the increase in the number of species with increasing area were lower in intensively grazed, fertilised pastures than in traditional pastures or in abandoned pastures. Species composition of abandoned pastures differed from that of the other management types. Plant species richness was influenced by different factors at different spatial scales. At the 1 m² scale, plant species richness was negatively related to soil nitrate and influenced by the cover of V. album, depending on land use: species richness and cover of V. album were negatively correlated in abandoned pastures, but positively correlated in fertilised grasslands. At the 1000 m² scale, a negative effect of fertilization on richness was evident. These results indicate that at small scales species richness in mountain grasslands is determined by competition for light, which should be more important if nutrient availability is high, and by positive and negative interactions with unpalatable plants. In contrast, species richness at the large scale appears to be mainly influenced by land use. This result emphasizes the importance of studying such inter‐relationships at multiple scales. Our study further suggests that the maintenance of the traditional land use scheme is crucial for the conservation of plant species richness of mountain pastures as both intensification and abandonment changed species composition and reduced plant species diversity.     

Are Sulfurous Soil Amendments (S0, Fe(II)SO4, Fe(III)SO4) an Effective Tool in the Restoration of Heathland and Acidic Grassland after Four Decades of Rock Phosphate Fertilization?

This paper deals with the complex issue of reversing long‐term improvements of fertility in soils derived from heathlands and acidic grasslands using sulfur‐based amendments. The experiment was conducted on a former heathland and acid grassland in the U.K. that was heavily fertilized and limed with rock phosphate, chalk, and marl. The experimental work had three aims. First, to determine whether sulfurous soil amendments are able to lower pH to a level suitable for heathland and acidic grassland re‐creation (approximately 3 pH units). Second, to determine what effect the soil amendments have on the available pool of some basic cations and some potentially toxic acidic cations that may affect the plant community. Third, to determine whether the addition of Fe to the soil system would sequester PO₄^? ions that might be liberated from rock phosphate by the experimental treatments. The application of S⁰ and Fe^(II)SO₄^? to the soil was able to reduce pH. However, only the highest S⁰ treatment (2,000 kg/ha S) lowered pH sufficiently for heathland restoration purposes but effectively so. Where pH was lowered, basic cations were lost from the exchangeable pool and replaced by acidic cations. Where Fe was added to the soil, there was no evidence of PO₄^? sequestration from soil test data (Olsen P), but sequestration was apparent because of lower foliar P in the grass sward. The ability of the forb Rumex acetosella to apparently detoxify Al³⁺, prevalent in acidified soils, appeared to give it a competitive advantage over other less tolerant species. We would anticipate further changes in plant community structure through time, driven by Al³⁺ toxicity, leading to the competitive exclusion of less tolerant species. This, we suggest, is a key abiotic driver in the restoration of biotic (acidic plant) communities.     

Fire and regeneration: the role of seed banks in the dynamics of northern heathlands

Questions: How do species composition and abundance of soil seed bank and standing vegetation vary over the course of a post‐fire succession in northern heathlands? What is the role of seed banks – do they act as a refuge for early successional species or can they simply be seen as a spillover from the extant local vegetation? Location: Coastal Calluna heathlands, Western Norway. Methods: We analysed vegetation and seed bank along a 24‐year post‐fire chronosequence. Patterns in community composition, similarity and abundances were tested using multivariate analyses, Sørensen's index of similarity, vegetation cover (%) and seedling counts. Results: The total diversity of vegetation and seed bank were 60 and 54 vascular plant taxa, respectively, with 39 shared species, resulting in 68% similarity overall. Over 24 years, the heathland community progressed from open newly burned ground via species rich graminoid‐ and herb‐dominated vegetation to mature Calluna heath. Post‐fire succession was not reflected in the seed bank. The 10 most abundant species constituted 98% of the germinated seeds. The most abundant were Calluna vulgaris (49%; 12 018 seeds m^?2) and Erica tetralix (34%; 8 414 seeds m^?2). Calluna showed significantly higher germination the first 2 years following fire. Conclusions: Vegetation species richness, ranging from 23 to 46 species yr^?1, showed a unimodal pattern over the post‐fire succession. In contrast, the seed bank species richness, ranging from 21 to 31 species yr^?1, showed no trend. This suggests that the seed bank act as a refuge; providing a constant source of recruits for species that colonise newly burned areas. The traditional management regime has not depleted or destroyed the seed banks and continued management is needed to ensure sustainability of northern heathlands.     

Species-rich Nardus stricta grasslands host a higher vascular plant diversity on calcareous than on siliceous bedrock

Background: Species-rich Nardus stricta grasslands are a priority habitat for conservation in Europe. They typically occur on siliceous substrates and less frequently are found on calcareous bedrock.

Aims: The present paper aimed to identify the environmental factors (i.e. bedrock type, topographic, and climatic factors) that are related with community diversity and to assess if differences in plant diversity between N. stricta communities on calcareous and siliceous bedrock occur. We hypothesised that Nardus grasslands on calcareous bedrock hosted a higher vascular plant diversity than those on siliceous bedrock.

Methods: Based on 579 vegetation surveys carried out in the south-western Alps, we assessed vascular plant diversity (species richness, Shannon diversity, and Pielou’s equitability index) of species-rich Nardus grasslands and compared it between N. stricta communities on calcareous and siliceous bedrock.

Results: Elevation was identified as the main factor related to species composition, while species diversity was mostly related to mean annual precipitation and bedrock type. Species richness, Shannon diversity, and Pielou’s equitability index were higher within the communities on calcareous rather than on siliceous bedrock and a total of 89 and 34 indicator species were detected, respectively.

Conclusions: Based on our results, we suggest to protect primarily, as a habitat of priority interest, N. stricta grasslands on calcareous substrates for the higher vascular plant diversity hosted.     

Giant stem rosettes have strong facilitation effects on alpine plant communities in the tropical Andes

ABSTRACT

Background: Giant rosettes constitute one of the most distinctive growth-forms in tropical alpine ecosystems. However, their interactions with other plant species remain unexplored in high Andean páramos.

Aims: Quantify the effect of a dominant rosette (Coespeletia timotensis) on soil and microclimatic conditions and relate the impacts to plant community structure.

Methods: We analysed topsoil temperatures, soil organic matter (SOM) and plant species cover in areas adjacent to C. timotensis and paired areas outside, at three sites (4250–4360 m a.s.l.) in La Culata National Park, Venezuela. Species richness, total vegetation cover and percent cover of each species near and away from the rosettes were compared.

Results: Topsoil temperature amplitudes were lower and SOM greater near C. timotensis stems, compared to areas away from them. C. timotensis had a consistent positive effect on species richness, vegetation cover and the cover of many abundant species (including cushions and herbs).

Conclusions: The facilitation effects of C. timotensis on abiotic conditions and community structure indicate they play a key role as nurse plants, pointing to giant rosettes as foundation species for the maintenance of plant diversity in the alpine tropics.     

Plant Species Composition Effects on Belowground Properties and the Resistance and Resilience of the Soil Microflora to a Drying Disturbance

We hypothesised that plant species composition and richness would affect soil chemical and microbial community properties, and that these in turn would affect soil microbial resistance and resilience to an experimentally imposed drying disturbance. We performed a container experiment that manipulated the composition and species richness of common pasture plant species (Trifolium repens, Lolium perenne, and Plantago lanceolata) by growing them in monoculture, and in all the possible two and three-way combinations, along with an unplanted control soil. Experimental units were harvested at four different times over a 16-month period to determine the effect of plant community development and seasonal changes in temperature and moisture on belowground properties. Results showed that plant species composition influenced soil chemistry, soil microbial community properties and soil microbial resistance and resilience. Soil from planted treatments generally showed reduced soil microbial resistance to drying compared to unplanted control soils. Soils from under T. repens showed a higher resistance and resilience than the soils from under P. lanceolata, and a higher resistance than soils from under L. perenne. We suggest that differences across soils in either resource limitation or soil microbial community structure may be responsible for these results. Plant species richness rarely affected soil microbial community properties or soil microbial resistance and resilience, despite having some significant effects on plant community biomass and soil nitrogen contents in some harvests. The effect that treatments had for most variables differed between harvests, suggesting that results can be altered by the stage of plant community development or by extrinsic environmental factors that varied with harvest timing. These results in combination show that soil microbial resistance and resilience was affected by plant community composition, and the time of measurement, but was largely unrelated to plant species richness.     

Changes in species composition of European acid grasslands observed along a gradient of nitrogen deposition

Question: Which environmental variables affect floristic species composition of acid grasslands in the Atlantic biogeographic region of Europe along a gradient of atmospheric N deposition? Location: Transect across the Atlantic biogeographic region of Europe including Ireland, Great Britain, Isle of Man, France, Belgium, The Netherlands, Germany, Norway, Denmark and Sweden. Materials and Methods: In 153 acid grasslands we assessed plant and bryophyte species composition, soil chemistry (pH, base cations, metals, nitrate and ammonium concentrations, total C and N, and Olsen plant available phosphorus), climatic variables, N deposition and S deposition. Ordination and variation partitioning were used to determine the relative importance of different drivers on the species composition of the studied grasslands. Results: Climate, soil and deposition variables explained 24% of the total variation in species composition. Variance partitioning showed that soil variables explained the most variation in the data set and that climate and geographic variables accounted for slightly less variation. Deposition variables (N and S deposition) explained 9.8% of the variation in the ordination. Species positively associated with N deposition included Holcus mollis and Leontodon hispidus. Species negatively associated with N deposition included Agrostis curtisii, Leontodon autumnalis, Campanula rotundifolia and Hylocomium splendens. Conclusion: Although secondary to climate gradients and soil biogeochemistry, and not as strong as for species richness, the impact of N and S deposition on species composition can be detected in acid grasslands, influencing community composition both directly and indirectly, presumably through soil‐mediated effects.