Changes In Plant Species Composition Research Articles

Vegetation responses to snow cover removal and rainfall reduction in subalpine grasslands: Insights from a 4-year field experiment in the Spanish Pyrenees

ABSTRACT Reduced precipitation as well as warming may result in less snow accumulation in seasonally snow-covered areas, leading to lower minimum soil temperatures and more frequent and severe soil frosts. Therefore, plant stress is increased not only by drought in warmer months, but also by increased exposure to frost in cooler periods. We conducted a 4-year field experiment to evaluate the effects of diminished snowpack accumulation (through snow removal) and rainfall reduction (through rain-out shelters) on aboveground plant productivity, diversity and species composition of two subalpine grassland plant communities from the central region of the Spanish Pyrenees. We found that the snow removal treatment decreased minimum soil temperature by 0.5°C. Plant diversity decreased by 16 percent, although this effect was only observed in one of the grasslands studied. Aboveground primary productivity seemed to be unaffected. In contrast, we found that the rainfall reduction treatment negatively affected aboveground productivity of leguminous forb species, yet no effect on plant diversity was observed. Both treatments were important drivers of changes in plant species composition. Overall, our results suggest that the resilience of subalpine grasslands to snow cover removal and rainfall reduction treatments may depend on the specific community composition and dominant plant groups.

Fire-modulated fluctuations in nutrient availability stimulate biome-scale floristic turnover in time, and elevated species richness, in low-nutrient fynbos heathland.

In many systems, postfire vegetation recovery is characterized by temporal changes in plant species composition and richness. We attribute this to changes in resource availability with time since fire, with the magnitude of species turnover determined by the degree of resource limitation. Here, we test the hypothesis that postfire species turnover in South African fynbos heathland is powered by fire-modulated changes in nutrient availability, with the magnitude of turnover in nutrient-constrained fynbos being greater than in fertile renosterveld shrubland. We also test the hypothesis that floristic overlaps between fynbos and renosterveld are attributable to nutritional augmentation of fynbos soils immediately after fire. We use vegetation survey data from two sites on the Cape Peninsula to compare changes in species richness and composition with time since fire. Fynbos communities display a clear decline in species richness with time since fire, whereas no such decline is apparent in renosterveld. In fynbos, declining species richness is associated with declines in the richness of plant families having high foliar concentrations of nitrogen, phosphorus and potassium and possessing attributes that are nutritionally costly. In contrast, families that dominate late-succession fynbos possess adaptations for the acquisition and retention of sparse nutrients. At the family level, recently burnt fynbos is compositionally more similar to renosterveld than is mature fynbos. Our data suggest that nutritionally driven species turnover contributes significantly to fynbos community richness. We propose that the extremely low baseline fertility of fynbos soils serves to lengthen the nutritional resource axis along which species can differentiate and coexist, thereby providing the opportunity for low-nutrient extremophiles to coexist spatially with species adapted to more fertile soil. This mechanism has the potential to operate in any resource-constrained system in which episodic disturbance affects resource availability.

Homogenization and species compositional shifts in subalpine vegetation during the 60-year period

Subalpine and alpine plant communities are considered highly sensitive and hence endangered by global changes. In central Europe, the highly sensitive habitats are also influenced by human activities: land use, industrial pollution, and tourism. That is especially true for subalpine plant communities formed on mid-latitude mountains during specific postglacial development. Our study aimed to (1) document changes in cover and plant species diversity between the past (1950s and 1970s) and present (2019) and (2) reveal differences in the functional composition of the species among the studied periods. In 2019, quasi-permanent marked plots originally surveyed in the 1950s and 1970s were resurveyed at Králický Sněžník (Śnieżnik Kłodski) Mountains, the High Sudetes Mts.. We assessed temporal changes in plant species composition, species cover, functional groups, growth forms, and degree of specialization. We found homogenization of the vegetation over time and changes in the cover of specific functional groups that were attributed to environmental factors connected with the cessation of historical land use, atmospheric deposition, and climate change. Implementing a suitable combination of mowing and grazing to support diversity, and to prevent homogenization of vegetation is highly recommended.

What is a suitable management for Typha latifolia control in wet meadows?

AbstractAimTypha latifolia causes serious problems in wet meadows by overgrowing and suppressing other native plants. To determine suitable management for T. latifolia control, we addressed the following question: What are the effects of long‐term cutting at different frequencies (once or twice per year and no management) and biomass removal on cover and other characteristics of T. latifolia, and on sward productivity and plant species composition?LocationMalá Strana nature reserve, Jizerské hory Mountains, Czechia.MethodsA long‐term experiment arranged in a randomised block design with three blocks was established in 2005. Data were collected from five treatments: unmanaged control; cutting once a year in June without biomass removal and with biomass removal; cutting twice per year in June and August without biomass removal and with biomass removal. Percentage cover of T. latifolia and other vascular plant species was visually estimated and T. latifolia characteristics (tiller density, height, dry‐matter biomass [DMB] yield and litter), sward height and DMB yield were measured during 2005–2018 at the end of June.Results and DiscussionRegular cutting once or twice per year regardless of cut biomass removal led to reductions in tiller density, height, litter and DMB yield of T. latifolia. Biomass removal had only a slight tendency to affect T. latifolia characteristics. The higher frequency of cutting significantly decreased the mean T. latifolia cover, litter and DMB yield. Cutting once or twice per year regardless of biomass removal led to successive changes in plant species composition but had no effect on the species richness and evenness.ConclusionsCutting at least once per year without biomass removal seems to be sufficient to achieve a decrease in DMB yield and litter of T. latifolia plants, and thereby maintain the wet‐meadow vegetation without loss of species richness and also preventing the overgrowth of shrubs and trees.

Biodiversity-Based Empirical Critical Loads of Nitrogen Deposition in the Athabasca Oil Sands Region

Anthropogenic nitrogen (N) emissions can have considerable effects on terrestrial ecosystems, with chronic N deposition leading to changes in plant species composition. The Athabasca Oil Sands Region (AOSR) represents a large point source of N emissions, which has prompted concern for surrounding habitats. The objective of this study was to determine the relative importance of N deposition as a driver of plant species community composition against bioclimatic and soil chemical variables. Further, we sought to identify community thresholds in plant species composition across a N deposition gradient. This assessment was performed for 46 Jack pine (Pinus banksiana Lamb.)-dominant forest sites surrounding the AOSR spanning Alberta and Saskatchewan. In total, 35 environmental variables were evaluated using redundancy analysis (RDA), followed by gradient forest analysis applied to plant species abundance data. Soil chemical variables accounted for just over 26% of the total explainable variation in the dataset, followed by bioclimatic variables (19%) and deposition variables (5%), but joint effects between variables also explained a significant portion of the total variation (p < 0.001). Total deposited nitrogen (TDN), and sulphur (TDS) along with bioclimatic and soil chemical variables, were identified as important variables in gradient forest analysis. A single, definitive threshold across TDN was identified at approximately 5.6 kg N ha−1 yr−1 (while a TDS threshold was found at 14.4 kg S ha−1 yr−1). The TDN threshold range was associated primarily with changepoints for several vascular species (Pyrola asarifolia, Pyrola chlorantha, Cornus canadensis, and Arctostaphylos uva-ursi) and bryophyte and lichen species (Pleurozium schreberi, Vulpicida pinastri, and Dicranum polysetum). These results suggest that across Jack pine-dominant forests surrounding the AOSR, the biodiversity-based empirical critical load of nutrient N is 5.6 kg N ha−1 yr−1.

Yellow-legged gull populations (Larus michahellis) link the history of landfills to soil eutrophication and time-related vegetation changes on small Mediterranean islands

Seabird colonies have a strong influence on both the physical and chemical soil parameters and plant communities of the islands where they settle to nest. Scientists have studied the effects of the demographic explosion of seabird populations, but few have explored the long-term effects when the colonies were in decline. The aim of this study was to investigate diachronic changes over a 24 year period of soil parameters, floristic composition and plant functionnal types (Raunkiaer growth forms and Grime life strategies) up to the decrease of the number of nesting yellow-legged gulls (Larus michahellis Naumann, 1840) on Mediterranean islands. We used 78 permanent plots to survey the vegetation and the soil parameters on 9 islands and one mainland area within the Calanques National Park (south east of France), for three periods (i.e., 1997, 2008, 2021).Since 1997, the increase of nesting gulls has caused a nitrogen and pH increase and organic carbon and C/N ratio decrease, although the values were still higher than mainland plots without nesting gulls. This has led to changes in plant species composition e.g., higher values of N favouring the development of ruderal plant species, still present in high frequency in 2021. Furthermore, plant species highly tolerant to disturbances (i.e., R Grime strategy) in harsh environments were still favoured even after the decline of gull abundance. However, both the frequency of the chamaephytes and the vegetation cover has increased with the decline of gull colony. In 2021, measures of trace elements' concentrations and calculation of pollution load index (Cu, Pb and Zn) reveals relatively low multi-contamination levels on the mainland and the archipelagos.On naturally oligotrophic and semi-arid Mediterranean islands, gull colonies induce a persistent alteration in soil characteristics that still influences plant communities (composition and functional types), 11 years after the decline in bird abundance.

Screening plant growth-promoting bacteria from the rhizosphere of invasive weed Ageratina adenophora for crop growth.

Plant-growth promoting rhizobacteria (PGPR) play a vital role in soil fertility and crop production. The rhizosphere of many crop plants has been well documented by screening PGPR for their plant-growth promoting (PGP) mechanisms. However, the rhizosphere of grass species that may act as potential habitats for novel PGPR remains relatively unexplored. Ageratina adenophora is a noxious weed that has invaded more than 40 tropical and subtropical countries in Asia, Oceania, Africa, and Europe. Its presence has led to changes in plant species composition, reducing their biodiversity and destroying ecosystem function. In this study, we screened 1,200 bacterial strains isolated from the rhizosphere soil of A. adenophora in three floristic regions in Yunnan Province, China. Samples were screened for their in vitro ability for N-fixation, production of the plant growth regulator indole-3-acetic acid (IAA), and the synthesis of 1-amino-cyclopropane-1-carboxylate (ACC) deaminase, which controls the levels of ethylene in developing plant roots. We found that 144 strains showed at least one of these PGP attributes. 16S rRNA gene sequencing showed that most (62.5%) of the samples were bacteria closely related to members of the genera Pseudomonas (27 strains), Providencia (20 strains), Chryseobacterium (14 strains), Ensifer (12 strains), Enterobacter (nine strains), and Hafnia (eight strains). Their abundance and biodiversity in the soil of individual floristic regions correlate positively with the invasion history of A. adenophora. From these PGP bacterial strains, KM_A34 (Pantoea agglomerans), KM_C04 (Enterobacter asburiae), and KM_A57 (Pseudomonas putida), which had the greatest in vitro ability of N-fixation, and IAA and ACC deaminase production, respectively, were selected. The strains were evaluated for their effect on the seed germination and growth of soybean, faba bean, pea, wheat, and Chinese cabbage other than A. adenophora. Chamber experiments showed these strains significantly (P < 0.05) increased (14.2-43.4% over the controls) germination rates of the soybean, faba bean, pea, and/or Chinese cabbage seeds. They also reduced relative seed germination times (20.8-48.8% over the controls) of soy bean, faba bean and/or wheat seeds. Greenhouse pot experiments showed that they significantly (P < 0.05) promoted the aboveground and belowground height of plant foliage (12.1-23.1% and 11.5-31.4% over the controls, respectively) and/or the dry weights (16.1-33.5% and 10.6-23.4% over the controls, respectively) of the soy bean, faba bean, pea, wheat and/or Chinese cabbage. These data indicate that the rhizosphere microbiota of A. adenophora contain a PGPR pool that may be used as bioinoculants to improve the growth and productivity of these crops.

The contrasted impacts of grasshoppers on soil microbial activities in function of primary production and herbivore diet

Herbivory can have contrasted impacts on soil microbes and nutrient cycling, which has stimulated the development of conceptual frameworks exploring the links between below- and aboveground processes. The “productivity model” predicts that herbivores stimulate microbial activities and accelerate nutrient mineralization in productive ecosystems, while they have an opposite effect in less productive ecosystems. In parallel, the “diet model” predicts that herbivores feeding on conservative plants accelerate nutrient cycling while those feeding on exploitative plants decelerate nutrient cycling, due to changes in litter inputs. Since these two frameworks can lead to conflicting predictions in some cases, experimental evidence combining herbivore diet and plant productivity is required. During two consecutive years, we conducted an experiment controlling the presence of three grasshopper species consuming either grasses, forbs or both in twelve natural and managed alpine grasslands with contrasted productivities. In order to assess the effects of herbivory on soil microbes, we measured their extracellular enzymatic activities, biomass and potential nitrogen mineralization (PNM). Soil and vegetation were also characterized to test how much they modulated the effects of herbivory on microbes. Contrary to the predictions of the diet model, the effects of herbivory on microbial characteristics did not depend on the herbivores diet, but were influenced by primary production, though in a way that differed from the productivity model. The most productive sites were constituted by exploitative plant species which depleted N resources in the soil, and by microbes producing relatively few extracellular enzymes, leading to a lower PNM. Herbivory increased microbial biomass and decreased the production of extracellular enzymes in those sites, possibly through the stimulation of root exudates produced by exploitative species. The least productive sites were characterized by conservative plants, high soil C content, and by microbes having a resource acquisition strategy (more extracellular enzymes, higher PNM). Herbivory decreased microbial biomass and increased the production of extracellular enzymes in those sites. This pattern can be explained by the loss of carbon associated with insect respiration, which increases the resource requirements of microbes and by a lower production of root exudates by conservative species. Therefore, the effects of two years of herbivory on soil microbes were at odds with the productivity model, which focuses instead on longer term effects corresponding to herbivory-induced changes in plant species composition. This highlights the multidimensional feature of the impacts of herbivory on ecosystem functioning, both in space and time.

Long-term effects of environmental alterations in protected grasslands – Land-use history determines changes in plant species composition

Nutrient-poor, semi-natural grasslands are among the most species-rich ecosystems across Europe. However, due to the transition from pre-industrial farming to modern agriculture, the extent of such grasslands has greatly decreased and the remaining patches have often suffered from habitat deterioration. Here, we analysed the effects of land-use and climate change as well as of nitrogen deposition on plant communities of dry (sand) (n = 118) and wet grasslands (n = 30) in a protected area, representative for the NE German young moraine landscape. Our study revealed that over a time period of 25 years, plant species composition in protected grasslands has changed considerably. Overall, plant species richness increased in both dry and wet grasslands from 1994 to 2019. The number of threatened species, however, decreased in dry but increased in wet grasslands. Land-use history was identified as the major driver of changes in species composition within the studied semi-natural grasslands. In wet grasslands, after >30 years of abandonment prior to the first survey, species-rich communities such as the Molinietalia have successfully been restored through the re-introduction of continuous, low-intensity management (mostly mowing once in late summer) shortly before the first survey. This has led to an increase of often threatened, light-demanding species of nutrient-poor wet grasslands. In dry grasslands, however, changes in vegetation were often contrary to those in wet grasslands; for example dry grasslands exhibited an increase in the nitrogen indicator value while it decreased in wet grasslands. Overall, open, nutrient-poor dry grasslands rich in stress-tolerant and often threatened species have been replaced by dense, more mesophytic grasslands with competitive generalists and some ruderal annuals. These successional changes were caused in particular by (i) an increase in abandonment on the least productive soils, (ii) undergrazing in permanent pastures and (iii) an insufficient time period since the re-introduction of grazing combined with a too low grazing pressure in new pastures on more productive soils. Nitrogen deposition was a further driver, especially on more acidic, dry soils. Additionally, grassland ruderalization was favoured by cropping of some plots and climate change since warm winters and severe summer droughts have led to an increase of annual ruderal species.

Developing understanding of biotic turnover

Over the last 50 years A.A. Titlyanova with her colleagues from the Laboratory of Biogeocenology in the Institute of Soil Science and Agrochemistry of the Siberian Branch of the Russian Academy of Sciences has been actively studying biotic turnover components and processes: the flow of carbon and its stocks in various ecosystem blocks were estimated, and turnover regimes revealed. The performed field experiments showed that the nearer an ecosystem is to the stationary state, the more closed its biotic turnover becomes, and the lesser role is played by abiotic processes. The studies in diverse ecosystems confirmed that climatic and weather conditions, soil properties as well as ecosystem’s relief position and exposition are the main factors driving the net primary production of grassland ecosystems. The article presents and discuss earlier results about phytomass dynamics and provides estimates of the net primary production, both above- and belowground. The belowground plant organs, i.e. roots and rhizomes, preserve life of a grassland ecosystem under any climatic conditions. Sustainability of grasslands in time depends on the changes in plant species composition, diverse survival strategies, high productivity of the dominant plant species, soil seed bank and their aeolian and water transportation from other ecosystems, rapid release of nutrients from residues by mineralization. Analysis of different successions in ecosystems allowed concluding that the number of succession types is higher than only two main types of primary and secondary succession. The primary succession refers only to those successions that occur by spontaneous revegetation at sites without any history of previous vegetation, whereas the secondary successions are more diverse and include pyrogenic (renovating succession), pasture (continuous and reversible), abandoned field successions and others. Not only the biotic turnover, but strong in- and outcoming flows of matter and energy operate in each and every ecosystem. Presently turnover can be better described as a network of diversified processes, rather than a circle per se.

Grazing season regulates plant community structure and production by altering plant litter mass in a typical steppe

AbstractAimsGrazing different grasslands with seasonal changes is the tradition in pastoral systems in natural grassland regions worldwide. The effects and mechanisms of different grazing seasons on semi‐arid steppe vegetation are less explored on the Mongolian Plateau. Therefore, we assessed the impact and underlying mechanisms of grazing seasons on grassland community structure and production.LocationXilingol, Inner Mongolia, China.MethodsWe conducted a three‐year experiment to investigate the effects of grazing in four different seasons under the same grazing intensities on plant community structure and production in a typical steppe rangeland. The experiment was a random‐block design, with 20 grassland paddocks of 50 m × 50 m, representing five treatments (i.e., early spring, summer, autumn, mid‐winter, and no grazing), replicated by four blocks. We monitored the changes in soil properties, plant litter mass (i.e., standing dead biomass and dead plant material on the soil surface) and plant species composition and production across grazing treatments.ResultsPlant community height and above‐ground biomass were higher under early spring and winter grazing than autumn and summer grazing and no grazing. This divergence in plant community structure was mainly mediated by the seasonal patterns of plant litter mass across the grazing regimes. A high plant litter mass enhanced soil moisture by accumulating snow in winter and reducing soil evaporation during the growing season, which benefit plant growth. The removal of plant litter before the growing season increased the reception of solar radiation, thus improving soil temperature and plant production. The changes in community microenvironment and selective grazing led to the changes in plant species composition especially under summer and autumn grazing.ConclusionsOur results imply that grazing in winter or in early spring before plants start to turn green is more efficient than the complete animal exclusion for the natural recovery of degraded grassland in Inner Mongolia. It is suitable to incorporate cold‐season grazing in the development of sustainable grassland management systems.

Lessons from a next generation carbon ranching experiment

Identifying grazing practices that maximize food production and soil carbon sequestration is of global importance. Currently, we cannot reliably predict which grazing practice will accrue the most soil organic carbon (SOC) partly because of confusion created by an abundance of low-quality experiments. Data quality has likely suffered because adequate treatment replication requires a lot of land, meaningful scale introduces heterogeneity among replicates, and pre-existing differences are often not taken into account. Here we tested the effects of five grazing treatments on SOC stocks with a gold standard randomized controlled trial (RCT) with pre-treatment data. Treatments were no grazing, severe summer grazing, moderate fall grazing, severe fall grazing, and the conventional approach for the system of moderate summer grazing. Because grazing experiments are often little-replicated, we also gauged the dependence of results on pre-treatment data by comparing the results of analyses with vs without pre-treatment data. We also tested for relationships between plant (root biomass, plant species composition) and soil properties (mass, nitrogen concentration) and SOC. After applying treatments for 5-yr, the no grazing and severe summer and fall grazing treatments accrued 0.85 to 1.22 kg × m−2 (0–60 cm soil depth) more SOC than conventional moderate summer grazing and represent appreciable (i.e. >4 per mille per yr) increases in SOC stocks. Furthermore, the entire portfolio of new grazing practices increased SOC accrual compared to conventional management. Given the divergent characteristics of the newly applied practices, sustainable accrual of SOC may depend on management heterogeneity. Accrual of SOC was likely driven by a reduction in SOC mineralization related to increased soil density and nitrogen, decreased root biomass, and change in plant species composition. Our findings counter the prevailing view that plant material inputs are the primary driver of SOC accrual in grazing lands. In other words, SOC accrual was mainly associated with indicators of decreased SOC mineralization (C outputs). We also found unique results for analyses with and without pre-treatment data, thereby indicating the risk of unreliable results for little-replicated RCTs without pre-treatment data. Robust generalizations on grazing practices that will reliably and sustainably maximize the rate of SOC accrual for a specific system, climate and timeline are still lacking, but further focus on factors affecting SOC mineralization will facilitate their development.

The health condition of trees in dendropark at Faculty of Forestry – Skopje with a special focus on fungal diseases and insect pests

The Dendropark at the Faculty of Forestry in Skopje, North Macedonia, was established as an ‘outdoor museum’ with a collection of forest trees and shrub vegetation. The collection was planted in 1950 on the area of 4.05 ha, and includes 336 taxa from native Macedonian and Balkan endemic dendroflora and introduced species from around the world. The Dendropark, like the other botanical gardens all over the world, offers a unique resource that facilitate earlier detection of the potential invasive threats to forest tree species. The inventoried population includes 444 trees belonging to 43 families. The three most represented families are Pinaceae with 21 species (19.4% of the inventoried plants), Cupressaceae with 16 species (15.8%) and Rosaceae with 18 species (7.4%). The 2014 survey indicated that 33.8% of the total number of trees were rated with good health status, 1.8% as very good, 31.1% rated as fair, while 24.5% were poor. Approximately 4.1% were rated to be in a critical state (in a state of decline), and 4.7% of trees were dead. The assessment of health status of plants in the Dendropark could be used as a valuable asset to planners and decision makers and provides information about the quality, quantity and location of natural resources in urban areas. Identifying changes in plant species composition and presence of invasive pests and diseases helps maintaining healthy urban forests.

Plant beta-diversity across biomes captured by imaging spectroscopy

Monitoring the rapid and extensive changes in plant species distributions occurring worldwide requires large-scale, continuous and repeated biodiversity assessments. Imaging spectrometers are at the core of novel spaceborne sensor fleets designed for this task, but the degree to which they can capture plant species composition and diversity across ecosystems has yet to be determined. Here we use imaging spectroscopy and vegetation data collected by the National Ecological Observatory Network (NEON) to show that at the landscape level, spectral beta-diversity—calculated directly from spectral images—captures changes in plant species composition across all major biomes in the United States ranging from arctic tundra to tropical forests. At the local level, however, the relationship between spectral alpha- and plant alpha-diversity was positive only at sites with high canopy density and large plant-to-pixel size. Our study demonstrates that changes in plant species composition and diversity can be effectively and reliably assessed with imaging spectroscopy across terrestrial ecosystems at the beta-diversity scale—the spatial scale of spaceborne missions—paving the way for close-to-real-time biodiversity monitoring at the planetary level.

A hurricane alters the relationship between mangrove cover and marine subsidies.

As global change alters the composition and productivity of ecosystems, the importance of subsidies from one habitat to another may change. We experimentally manipulated black mangrove (Avicennia germinans) cover in 10 large plots and over a 5-year period (2014-2019) quantifying the effects of mangrove cover on subsidies of floating organic material (wrack) into coastal wetlands. As mangrove cover increased from 0% to 100%, wrack cover and thickness decreased by ~60%, the distance that wrack penetrated into the plots decreased by ~70%, and the percentage of the wrack trapped in the first 6 m of the plot tripled. These patterns observed during 4 "normal" years disappeared in a fifth year following Hurricane Harvey (2017), when large quantities of wrack were pushed far into the interior of all the plots, regardless of mangrove cover. Prior to the storm, the abundance of animals collected in grab samples increased with wrack biomass. Wrack composition did not affect animal abundance or composition. Experimental outplants of two types of wrack (red algae and seagrass) revealed that animal abundance and species composition varied between the fringe and interior of the plots, and between microhabitats dominated by salt marsh versus mangrove vegetation. The importance of wrack to overall carbon stocks varied as a function of autochthonous productivity: wrack inputs (per m2 ) based on survey data were greater than aboveground plant biomass in the plots (42 × 24 m) dominated by salt-marsh vegetation, but decreased to 5% of the total aboveground biomass in plots dominated by mangroves. Our results illustrate that increasing mangrove cover decreases the relative importance of marine subsidies into the intertidal at the plot level, but concentrates subsidies at the front edge of the mangrove stand. Storms, however, may temporarily override mangrove attenuation of wrack inputs. Our results highlight the importance of understanding how changes in plant species composition due to global change will impact marine subsidies and exchanges among ecosystems, and foster a broader understanding of the functional interdependence of adjacent habitats within coastal ecosystems.

Effects of extensive grazing on the vegetation of a landscape-scale restoration site

The Wicken Fen Vision (Cambridgeshire, UK) is a landscape-scale habitat restoration project that uses process-driven, open-ended approaches to develop habitats on highly degraded and drained peat soils of former intensive arable land. The project land is extensively grazed with herds of free-roaming, minimally managed herds of Highland cattle and Konik horses. In one 119 ha area, seven 25m x 25 m grazing exclosures were erected and vascular plant species were recorded from 2007 to 2017. Plant species data were analysed to (1) compare changes in plant species composition and diversity in grazed and ungrazed areas; (2) use plant species traits and plant-environment associations to explore the nature of changes in plant composition; (3) use remote sensing to explore changes in vegetation structure; (4) examine the influence of land use histories on grazing outcomes in different parts of the site.There was a clear divergence through time between grazed and ungrazed areas, attributed to significantly greater canopy height, Ellenberg L (Light) and Ellenberg N (fertility) values within the exclosures. Species richness was significantly higher in grazed compared with ungrazed areas and species assemblages separated through the study period. After ten years, extensive free-roaming grazing has had significant impacts on vegetation structure and species richness but effects varied across the study site because of differing historical land use.

Fungal root colonization and arbuscular mycorrhizal fungi diversity in soils of grasslands with different mowing intensities

Grasslands are among the most dynamic and threatened plant communities, largely due to their dependence on management that has changed in recent decades. The intensity of human-induced disturbances (primarily removal of plant biomass by various methods) has decreased, leading to changes in plant species composition and declines in plant diversity in these communities. So far, no studies have shown how mowing affects fungal communities in both roots and soils and their relation with plant community parameters and soil chemical properties in different grassland types. We thus compared the impact of mowing intensity (low, moderate, high) on root colonization by common root-inhabiting fungi, namely arbuscular mycorrhizal fungi (AMF), dark septate endophytes (DSE), and Olpidium spp., as well as on AMF spore number, species richness and composition in soils for three seasons (spring, summer, autumn), in grasslands differing in soil moisture (wet, moderately wet, and dry). Mowing intensity had no effect on the fungal root colonization. The number of AMF spores and species, and AMF species composition did not differ between types of management as well. However, most of the fungal parameters in roots and soils varied across the types of grassland and/or seasons. Our results suggest that AMF, DSE, and Olpidium spp. colonization of plants as well as AMF diversity in soils in the studied grasslands are resilient to the mowing disturbance. This may be due to the low impact of the management on plant species richness and soil chemical properties, as well as the adaptation of these fungal communities to recurrent human-induced disturbances in semi-natural habitats.

Ongoing decline in insect-pollinated plants across Danish grasslands.

Loss of habitat, eutrophication and reduced grazing intensity are known drivers of landscape-level changes in plant species composition; however, consequences of the massive decline in insect abundance are still to be understood. Pollinator decline can reduce seed set in plants relying on insects for successful reproduction. This may result in a reduced recruitment of insect-pollinated plant species with associated changes in species composition. So far, large-scale studies addressing this issue have relied on few data points-typically consisting of 'historic' records of numbers of insect-pollinated plants compared to present-day records. Such comparisons can provide information as to whether the diversity of insect-pollinated plants has changed, but not whether the process is still ongoing. Here, we use nationwide monitoring data of plant species richness in Danish grasslands from the period 2004-2014, covering 244 grassland sites and encompassing more than 790 flowering plant species. We show an ongoing decrease in insect-pollinated, but not wind-pollinated, plant species across different habitat types. In both dry calcareous and Nardus grasslands, loss of insect-pollinated plants was greatest at sites with low grazing intensity. However, insect-pollinated plants also declined from sites with higher grazing intensity, and plants requiring more specialized insect pollination tended to decline most. In addition to changes in plant diversity driven by land-use intensification, loss of pollinators may also play a role in reducing the richness of insect-pollinated plants. Ongoing reduction in floral richness could further increase the threat to insects relying on these plants as a food source.

Phenological stage of tundra vegetation controls bidirectional exchange of BVOCs in a climate change experiment on a subarctic heath.

Traditionally, biogenic volatile organic compound (BVOC) emissions are often considered a unidirectional flux, from the ecosystem to the atmosphere, but recent studies clearly show the potential for bidirectional exchange. Here we aimed to investigate how warming and leaf litter addition affect the bidirectional exchange (flux) of BVOCs in a long‐term field experiment in the Subarctic. We also assessed changes in net BVOC fluxes in relation to the time of day and the influence of different plant phenological stages. The study was conducted in a full factorial experiment with open top chamber warming and annual litter addition treatments in a tundra heath in Abisko, Northern Sweden. After 18 years of treatments, ecosystem‐level net BVOC fluxes were measured in the experimental plots using proton‐transfer‐reaction time‐of‐flight mass spectrometry (PTR–ToF–MS). The warming treatment increased monoterpene and isoprene emissions by ≈50%. Increasing temperature, due to diurnal variations, can both increase BVOC emission and simultaneously, increase ecosystem uptake. For any given treatment, monoterpene, isoprene, and acetone emissions also increased with increasing ambient air temperatures caused by diurnal variability. Acetaldehyde, methanol, and sesquiterpenes decreased likely due to a deposition flux. For litter addition, only a significant indirect effect on isoprene and monoterpene fluxes (decrease by ~50%–75%) was observed. Litter addition may change soil moisture conditions, leading to changes in plant species composition and biomass, which could subsequently result in changes to BVOC emission compositions. Phenological stages significantly affected fluxes of methanol, isoprene and monoterpenes. We suggest that plant phenological stages differ in impacts on BVOC net emissions, but ambient air temperature and photosynthetically active radiation (PAR) also interact and influence BVOC net emissions differently. Our results may also suggest that BVOC fluxes are not only a response to changes in temperature and light intensity, as the circadian clock also affects emission rates.

Effects of long-term removal of sheep-grazing in a series of British upland plant communities: Insights from plant species composition and traits

Environmental and management pressures are considered a threat for preserving plant communities worldwide. Identification of long-term impacts of changing management practices on plant community composition must, therefore, be a major priority to ensure improvement in conservation value. Land abandonment/wilding is one topical area where there is little available information on long-term impacts. To address this, here, we describe plant species compositional change over relatively long-time scales in a range of four British upland communities (high-level grasslands, intermediate grasslands, blanket bogs and high-level bogs) and its relationships with a series of life-history and plant trait variables. Our aims were to determine whether the business-as-usual sheep grazing practice was maintaining these communities, and if grazing was to be removed as part of abandonment/wilding strategies, would there be a conservation benefit. We used a series of long-term experimental grazing-exclosure studies at twelve sites (>40 years) on the Moor House National Nature Reserve in northern England. Each site consisted of paired plots; i.e. sheep-grazed versus ungrazed. Our results showed that there was relatively little change in dominant plant species with most change occurring within sub-dominant species. Similarly, different temporal responses in plant species richness were detected between the experiments (richness was reduced in three experiments, only one increased). In any case, the vegetation temporal trajectories were moving in similar direction in grazed and ungrazed plots at most sites. Interestingly, blanket bog experiments showed a clear compositional convergence for both grazed and ungrazed plots, although, the between-site differences related to a combination of elevation and past burning testament. Finally, the bryophytes (especially liverworts) and lichens were the groups that contributed most to the reductions in species richness. Moreover, implementation of a no-stock grazing strategy under a land abandonment/wilding approach will not bring about much plant change in the short-term in the plant communities studied here.