Fruticose Research Articles

Radionuclides, Macro- and Microelements in the Thalli of Taiga Fruticose Lichens of the European Northeast

Radionuclides, Macro- and Microelements in the Thalli of Taiga Fruticose Lichens of the European Northeast

Quantitation of Usnic acid from three Usnea species, its commercial formulations Using High-Performance Thin-Layer Chromatography-Mass Spectrometry (HPTLC-MS) and their metabolite profiling using UPLC-QTof-MSE.

The genus Usnea (Parmeliaceae; lichenized Ascomycetes) is pale grayish-green fruticose lichens which grow as leafless mini-shrubs and comprise about 360 species. Most of the Usnea species are edible and is utilized in preparation of traditional foods as well as in medicines to combat wide range of ailments. The goal of this work was to quantify usnic acid in three Usnea spp. [Usnea ghattensis (UG), Usnea orientalis (UO) and Usnea undulata (UU)] using HPTLC-MS and chemical profiling of acetone extracts using UPLC-QTof-MSE resulted in the identification of sixteen compounds based on their MS/MS fragmentation patterns. Hyphenated techniques, HPTLC-MS and UPLC-QTof-MSE have been proposed to quantify usnic acid and analysis of metabolites in the crude extracts qualitatively. This method allowed tentative characterization of metabolites from Usnea spp. The quantification study showed the excellent linearity of the usnic acid at 0.25-1 µg/band with a correlation coefficient r 2>0.99, and LOD, LOQ was found to be 51.7 and 156.6 ng/band, respectively. Further, UPLC-QTof-MSE analysis of crude extract led identification of lichen substances through their exact molecular masses and MS/MS fragmentation studies. The present study summarizes HPTLC method for quantification of usnic acid in three different Usnea spp. Along with two herbal formulations containing Usnea spp. as the ingredient and developed method was validated as per the ICH guidelines and further UPLC-QTof-MSE analysis provides characterization of the sixteen different secondary metabolites based on their mass fragmentation studies. Rapid HPTLC method for quantification of usnic acid in three different Usnea spp. along with two herbal formulations and metabolite profiling using UPLC-QTof-MSE.

Evidence for the translocation of fixed N in the N2-fixing lichen Stereocaulon vesuvianum.

The fruticose lichen Stereocaulon vesuvianum is among the most abundant and widespread lichens in upland Britain. It typically produces cephalodia (nodules) that contain the cyanobacterium Stigonema, which can fix atmospheric nitrogen. However, over much of England, Wales, and southern Scotland S. vesuvianum no longer produces cephalodia and does not fix nitrogen, a morphological change linked to elevated atmospheric nitrogen deposition. This provided a unique opportunity to compare the 15N natural abundance signatures in N2-fixing and non-N2-fixing lichen populations, keeping in mind that fixed nitrogen has a 15N content close to that of atmospheric N2 while, in comparison, several components of atmospheric combined N (e.g. nitrate and ammonium in precipitation) tend to be 15N depleted. We found that in N2-fixing samples, there was a steep gradient in 15N relative abundance in the terminal 15 mm of thallus branches (pseudopodetia), changing from 15N depleted tissues at 10-15 mm below the tips to values close to that of atmospheric N2 at the apices while in non-N2-fixing samples thallus branches were uniformly 15N depleted. The 15N gradient in N2-fixing material could not be explained by the presence of cephalodia since these are more abundant towards branch bases. The data provide the first evidence in lichens of translocation of recently fixed N to sink regions of active growth and production of asexual reproductive propagules, bringing lichens into line with N source-sink relationships in N2-fixing plant symbioses.

Inventarisasi Awal Liken Langka, Sensitif dan Toleran sebagai Bioindikator Polutan di Kabupaten Belitung Barat

The existence and population conditions of the rare, sensitive or tolerant lichens of Lobaria, Coccocarpia, Coenogonium, Dictyonema, Pseudocyphellaria, Sticta, Usnea, Leptogium, and Parmotrema tinctorum are not yet known in West Belitung Regency, so this research needs to be carried out. The method used in this research was exploratory descriptive with survey techniques and purposive sampling. The number of target lichen thallus was calculated from the entire area of the tree trunk with a height of 0-1.5 m. The lichens found in the Gunung Tajam area were Coccocarpia sp. with the highest number of thallus and the highest frequency of thallus (0.8%), followed by Coenogonium sp., Leptogium sp., and Usnea sp. with the same frequency of thallus (0.4%) while in the Batu Mentas area lichens were not found as the research target, but was dominated by fruticose lichen. Parmotrema tinctorum, the tolerant lichen, was not found at either location. The presence of sensitive lichens and the absence of tolerant lichens does not indicate that the locations have good air quality. It is recommended that the lichen population, especially P. tinctorum, be studied further so that air quality can be easily confirmed through the diversity and population of the lichens.

The Depside Derivative Pericodepside Inhibits Cancer Cell Metastasis and Proliferation by Suppressing Epithelial-Mesenchymal Transition.

A depside derivative, named pericodepside (2), along with the known depside proatranorin III (1), was isolated from the solid cultivation of an Ascochyta rabiei strain that heterologously expresses atr1 and atr2 that are involved in the biosynthesis of atranorin in a fruticose lichen, Stereocaulon alpinum. The structure of 2 was determined by 1D and 2D NMR and MS spectroscopic data. The structure of 2 consisted of a depside-pericosine conjugate, with the depside moiety being identical to that found in 1, suggesting that 1 acted as an intermediate during the formation of 2 through the esterification process. Pericodepside (2) strongly suppressed cell invasion and proliferation by inhibiting epithelial-mesenchymal transition and the transcriptional activities of β-catenin, STAT, and NF-κB in U87 (glioma cancer), MCF-7 (breast cancer), and PC3 (prostate cancer) cell lines.

Influence of Orographic Factors on the Distribution of Lichens in the Franz Josef Land Archipelago.

During a geobotanical study of the Franz Josef Land archipelago, 111 lichen species were recorded on 130 sample plots. The significance of orographic factors in the distribution of lichens was assessed using principal component analysis (PCA) and multiple regression analysis. It was found that the absolute altitude and distance from the glacier are of the greatest importance for crustose lichens, while for fruticose lichens, the most critical factors were the slope exposure and steepness. Along the altitudinal gradient, the number of species decreased (from 88 to 25). The highest number of species (90) was recorded at distances of 0.1 to 1.0 km from the glacier edge, which is explained by the unstable species composition of areas recently released from under the glacier. The number of species in all groups generally decreased (from 81 to 52) with increasing slope steepness. With an increasing heat supply of slopes (on a gradient from northern to southern), the number of species steadily increased in all groups (from 39 to 75). The low sum of the explained variance values for the first two PCA components (21%) characterizes the specificity of the natural environment of polar deserts, where there is no leading environmental factor.

Non-photochemical quenching may contribute to the dominance of the pale mat-forming lichen Cladonia stellaris over the sympatric melanic Cetraria islandica.

The mat-forming fruticose lichens Cladonia stellaris and Cetraria islandica frequently co-occur on soils in sun-exposed boreal, subarctic, and alpine ecosystems. While the dominant reindeer lichen Cladonia lacks a cortex but produces the light-reflecting pale pigment usnic acid on its surface, the common but patchier Cetraria has a firm cortex sealed by the light-absorbing pigment melanin. By measuring reflectance spectra, high-light tolerance, photosynthetic responses, and chlorophyll fluorescence in sympatric populations of these lichens differing in fungal pigments, we aimed to study how they cope with high light while hydrated. Specimens of the two species tolerated high light equally well but with different protective mechanisms. The mycobiont of the melanic species efficiently absorbed excess light, consistent with a lower need for its photobiont to protect itself by non-photochemical quenching (NPQ). By contrast, usnic acid screened light at 450-700nm by reflectance and absorbed shorter wavelengths. The ecorticate usnic species with less efficient fungal light screening exhibited a consistently lower light compensation point and higher CO2 uptake rates than the melanic lichen. In both species, steady state NPQ rapidly increased at increasing light with no signs of light saturation. To compensate for less internal shading causing light fluctuations with a larger amplitude, the usnic lichen photobiont adjusted to changing light by faster induction and faster relaxation of NPQ rapidly transforming excess excitation energy to less damaging heat. The high and flexible NPQ tracking fluctuations in solar radiation probably contributes to the strong dominance of the usnic mat-forming Cladonia in open lichen-dominated heaths.

About two important paradigms of modern geobotany: supracenotic organization and phylocenogenesis

In the 20th century, many brilliant personalities enriched not only domestic, but also world science, including V N. Sukachev, E. M. Lavrenko, V B. Sochava. In general, paradigms are important in the development of science as examples of problem posing models or new approaches to the implementation of ideas. The paradigm of the spatial organization of phytosystems from the standpoint of a universal scientific approach is affirmed in the triad of the process of cognition: see - describe - explain. It reflects the concept of the spatial-structural approach in geobotany. To the question - why, the meaning of the explanatory paradigm of the process of cognition is focused. As an example, the results of our studies of the vegetation of the upland terraces of the Altai Mountains. Based on the analysis of their most important features of the structure and modes of operation, a schematic diagram of the types of interaction of elements of the terraced slope was created, which made it possible to reach a forecast in the dynamics of their development. The paradigm of adaptive morphogenesis of plants in ecosystems, landscape and topolithogenic spheres is expressed in the triad of relationships: the center of ore genesis - geochemical anomaly - adaptive morphogenesis. This is the basis of the biogeochemical conditionality of florogenesis, which means the prospects for research into the latest foci of speciation -the formation of endemic species and communities of vegetation. Thus, we established selective accumulation of gold (Au) by fruticose lichens in the communities of taiga larch forests of the Ilchir tract in the foothills of the Kitoi bald mountains (Eastern Sayan). The selective accumulation of elements in phytocenoses indicates the biogeochemical conditionality of florogenesis. An endemic cryophyte-steppe association with Festuca komarovii Krivot. is described. Phylocenogenesis as a process of adaptive morphogenesis of biosystems is the growth point of geobotany, and its result - speciation and cenogenesis are realized in complex geobotanical studies.

Mercury content and elemental composition of fruticose lichens from Nahuel Huapi National park (Patagonia, Argentina): Time trends in transplanted and in situ grown thalli

Lichens have a unique structure involving the symbiosis of fungus and algae and can grow on almost any type of substrate. They absorb gases, water, nutrients and pollutants through their cortex, and thus are good indicators of environmental processes, enabling the biomonitoring of environmental pollutants. These organisms are widely distributed; however, as certain species do not occur in some areas, transplants are commonly used to monitor air pollution. In this study, transplants of the fruticose species Protousnea magellanica were set up at the EMMA Station (Global Mercury Observation System, GMOS) located at a suburban site of San Carlos de Bariloche city within Nahuel Huapi National Park (North Patagonia, Argentina). The transplants were used to assess the uptake of certain elements, particularly the accumulation of mercury. Periodic samplings of the transplanted species P. magellanica and the naturally occurring Usnea pusilla were performed concurrently at the experimental site over 483 days of experimental exposure. The elemental composition and concentration of the thalli of these species were determined by Neutron Activation Analysis in a nuclear reactor. Atmospheric mercury concentration (Gaseous Elemental Mercury, GEM) was monitored at the EMMA Station by an automated cold vapor atomic fluorescence system (Tekran 2537B). Mercury concentrations in the lichens were at least three orders of magnitude higher than atmospheric mercury levels (0.80–0.94 ng/m3, ppt), highlighting the accumulation capacity of these organisms. Concentrations found in P. magellanica thalli (0.080–0.327 μg/g dry weight, ppm) lay within the range of values reported previously in lichens from the Nahuel Huapi National Park with low anthropogenic impact. During experimental exposure both lichen species displayed the same trend in Hg content. Total Hg increased from T0 to T1 (day 25) and then decreased up to approximately T4 (day 385). In U. pusilla, the positive relationship between Hg content and lithophilic elements such as La, suggested preferential Hg uptake from airborne particles (deposited dust).

Variation in albedo and other vegetation characteristics in non-forested northern ecosystems: the role of lichens and mosses

Vegetation has a profound impact on climate through complex interactions and feedback loops, where especially regulation of albedo, the ratio of reflected to incoming solar radiation, is important at high latitudes. How vegetation albedo varies along environmental gradients in tundra ecosystems is still not well understood, particularly for ecosystems dominated by nonvascular vegetation. We studied broadband shortwave albedo of open boreal, arctic, and alpine ecosystems over a 2000 km long latitudinal gradient (60° N–79° N) and contrasted this against species composition, vegetation greenness (normalised difference vegetation index—NDVI), momentary ecosystem CO2 fluxes and reindeer (Rangifer tarandus) grazing pressure. High cover of pale terricolous fruticose lichens was the single most important predictor for vegetation albedo, which had a maximum value of 0.389 under clear sky conditions and solar zenith angle 60°. To our knowledge, this is the highest broadband albedo recorded for a vegetated surface. NDVI was negatively correlated to lichen biomass (rs = −0.56), and albedo (rs = −0.19). Gross primary production and ecosystem respiration varied considerably less between plots and vegetation types than albedo. While it is well-known that Rangifer affects climate-relevant aboveground biomass, we here show that its regulation of surface albedo in northern ecosystems may also be of high importance for land-atmosphere interactions. The data presented here thus advocate for an increased understanding of the important and complex role of herbivores and lichen cover in climate-vegetation interactions.

Plant potential and ecological and economic suitability of reindeer pastures on the right bank of the Norilsk River

Purpose : identification of plant potential, ecological and economic suitability of deer pastures of the forest-tundra zone located in the zone of anthropogenic influence Material and methods . Ground geobotanical survey of the vegetation cover of deer pastures was carried out by route method in accordance with the method of geobotanical studies. The ecological and economic value of each type of pasture was determined based on the data of the ecological and economic classification of deer pastures in the north. Results . 25 species of reindeer pastures are described on the right bank of the Norilsk River in the northwestern part of the Putorana Plateau. On the basis of signs of uniformity in the structure of vegetation (proximity of species composition, similarity of vertical and horizontal structures), they are combined into 4 types: tundra, swamps, shrubs and light forests. Tundra (30.9%) and shrub (27.6%) types of pastures dominate. The most important feature is the active participation in the structure of phytocenoses of shrubs (Betula nana s. str, Salix glauca s. str, S. lanata s. str.) and shrubs (Ledum palustre. Vaccinium uliginosum s. str, V. vitis-idaea s. str.). Green fodder is most nutritious in the first half of summer. The nutritional value of fruticose lichens does not change during the year. Reindeer pastures with lichen cover and high (from 5 to 12 o-days/ha) reindeer capacity during the snowy period occupy insignificant (24.3%) areas. Basically, these are willow and dwarf dwarf shrub-lichen tundras and larch sparse forests of dwarf-shrub moss-lichen. The participation of lichens in the ground cover of plant communities does not exceed 25–35%. The following lichen species have been recorded: Cladonia arbuscula, C. stellaris, C. rangiferina, C. cornuta, C. deformis, C. mitis, Cetraria cucullata, and C. islandica. The most widespread species of the genus Cetraria: Cetraria islandica and C. cucullata, with a clear advantage of the latter. The main forage species of the genus Cladonia (Cladonia arbuscula, C. stellaris, C. rangiferina) are not widely distributed. Pastures with a high (from 9 o-days/ha to 14 o-days/ha) reindeer capacity in the summer, early autumn and late spring periods prevail in the study area. Basically, these are communities of shrub and marsh types. Shrubs (Salix glauca s. str, S. lanata s. str., S. hastata, Betula nana s. str.), shrubs (Salix reticulata, Vaccinium vitis-idaea s. str.) and forbs (species of the genera Petasites, Pedicularis, Astragalus, Hedysarum, Equisetum, Bistorta).

CONSUMPTION OF THE LICHEN ROCCELLA GRACILIS BY THE LARGE GROUND-FINCH GEOSPIZA MAGNIROSTRIS ON THE ISLAND OF DAPHNE MAJOR (GALÁPAGOS)

This note reports a trophic interaction of a passerine consuming lichens. On the islet of Daphne Major (Galápagos Archipelago), we made five observations of the Large Ground-Finch Geospiza magnirostris eating the fruticose lichen Roccella gracilis. This is an example of how island birds broaden their feeding niche in resource-poor environments.

Selecting the species to be used in lichen transplant surveys of air pollution in Tunisia

This study was undertaken with the aim of selecting one or more lichen species that are the most suitable for transplant-based surveys of air pollution in Tunisia, in areas where the local native lichen vegetation is scanty or missing at all. To this purpose, four epiphytic (tree inhabiting) lichen species (Evernia prunastri, Flavoparmelia caperata, Parmotrema perlatum, Ramalina farinacea) were collected from the Babouch forests, a remote and unpolluted area of NW Tunisia, and analyzed for their content of potentially toxic elements (PTEs), namely Al, As, Cd, Cr, Cu, Fe, Ni, Pb, Sb, and Zn, by ICP-MS. Moreover, also the physiological status of the lichen samples was evaluated by measuring their chlorophyll content, photosynthetic efficiency, and spectral reflectance. The results indicated a remarkable contribution of airborne soil and dust particles to the total PTE content, especially for the foliose species F. caperata and P. perlatum. The fruticose lichens E. prunastri and R. farinacea had a lower and similar content of PTEs, and hence were regarded as more suitable to be used in transplant studies, since are able to detect even minimal accumulation amounts. All lichen species were healthy, as emerged from the analysis of physiological parameters.

Nowe stanowiska Evernia divaricata (L.) Ach. w zachodniej Polsce

A new locality of a rare fruticose lichen species Evernia divaricata in the western part of Poland was found in the vicinity of two cities: Gubin and Twardogóra. Single specimens of this epiphytic lichen, grew on larch and birch. The thalli were healthy and well developed. Evernia divaricata is under strict legal protection and considered an endangered species in Poland (the CR category in the „Red List of Polish Lichens”). In the last dozen or so years, over a dozen new localities of E. divaricata have been found in the country, which usually grew in the company of other lichens very sensitive to air pollution, e.g. from the genus Usnea. These taxa are a testimony to the increasing process of recolonization.

Ecolichenology of Eastern Ghats diversity against climatic fluctuations in Kolli Hills, India

Abstract. Subbaiyan R, Ganesan A, Dhanuskodi S. 2023. Ecolichenology of Eastern Ghats diversity against climatic fluctuations in Kolli Hills, India. Biodiversitas 24: 625-635. Lichens are major components of earthbound and marine environments. A lichen is a symbiotic form of algae and fungi adapted to survive in different altitudes and environmental conditions. The lichen morphology is divided into three, based on their habitat: crustose, foliose, and fruticose lichens. Eastern Ghats (EG) contribute significantly to both the endemicity and species richness of the Indian region. However, EG forests are relatively unexplored and have received less conservation consideration than the Western Ghats. Unexplored Eastern Ghats were studied to analyze the ecolichenology against climatic fluctuations. The objective of this paper is to build a stock of epiphytic lichens within the Kolli slopes. Kolli Hills are one of the ancient richest floral and faunal biodiversity hotspots of Eastern Ghats. It is assessed from the year 2018 to that 2021 with different climatic seasonal variations. The least diversity was found with the Arthonioid > Usneoid > Scaly > Ramalinoid types. Highly denser than the Parmelioid foliose and Usneoid, the Ramlinoid species was rich in numbers with healthy thallus. The population was stopped, or the least amount of thallus growth was noticed from the high rainfall season and gradual reduction in the summer. The Ramalinoid and Parmelioid lichens were found to be easy identifiers. The richness was reduced dependently and independently with nature. The health of lichens was encountered with only morphological appurtenance. Based on the lichen group, the maximum distribution was observed in Usneoid and Ramalinoid categories. The last distribution was found with Leprose and Scaly lichens. The forest wealth was described with the denser lichen patches and the shrinkages of Parmelioid lichens, especially the Dirinaria and Parmoterma, acting as a wealth analysis tool of the forest ecosystems.

Composition and diversity of endolichenic microfungal communities from saxicolous lichens at Nahal Boker, the central Negev Desert, Israel

We studied the endolichenic fungal communities from saxicolous lichens occupying the cobbles at Nahal Boker, the central Negev Desert, Israel. Overall, 101 species belonging to 64 genera were isolated from 12 lichen species collected in three seasons from the south-facing slope (SFS) and north-facing slope (NFS) of the wadi. The endolichenic communities possessed a set of traits, which helped them to cope with harsh internal and external conditions. It included a prevalence of melanin-containing fungi with thick-walled and multicellular spores and a comparatively high contribution of thermotolerant species and species with meiospore-producing life cycle stage at the more microclimatically severe SFS. Species richness and isolate density of endolichenic communities was the highest in fruticose lichens with thick and wrinkled thalli, and the lowest in endolithic species possessing thin and smooth thalli. The communities from lichens formed a more diverse group than those from surrounding cobbles probably due to the influence of various species of lichens belonging to different growth forms.

Elemental Composition of Reindeer Pasture Plants and Lichens in Nadym District (Yamal-Nenets Autonomous Area)

Abstract—There are plans to expand reindeer husbandry in the Nadym District of the Yamal-Nenets Autonomous Area. For this purpose, we studied the elemental composition of the dominant species of the tundra and open boreal woodland vegetation cover. We analyzed leaves of dwarf birch (Betula nana L.), dwarf shrubs of bog blueberry (Vaccinium uliginosum L.), marsh Labrador tea (Ledum palustre L.), and leatherleaf (Chamaedaphne calyculata (L.) Moench); sphagnum moss (Sphagnum sp. L.); and fruticose lichens (Cladina stellaris (Opiz.) Brodo). The X-ray fluorescence analysis was used to obtain data on the content of Ca, K, P, Si, Mg, Na, S, Zn, Cu, Ni, Co, Fe, Mn, Cr, Ti, and Al. We defined the biogeochemical features of the reindeer forage plants. In vascular plants and sphagnum mosses, the content of almost all essential macroelements is low, while the content of most microelements (Cu, Ni, Co, Cr, and Mn) exceeds the world average values. The lichens are characterized by low concentration of Ca, K, Mg, and P, which is more than one order of magnitude lower than the world average values, and the deficiency of microelements. The results were compared with the results from similar studies in other geographical regions of the tundra zone, and it was found that tundra plants have a similar pattern of element accumulation. In particular, leaves of dwarf birch are distinguished by accumulation of Mg; the content of Al, Fe, and Si is increased in mosses; Mn is accumulated in dwarf shrubs and dwarf birch; lichens are characterized by the deficiency of most elements. Therefore, in order to prevent animal diseases, it is necessary to improve the elemental composition of reindeers feed by increasing the share of “green” forage in winter, when lichens dominate the diet.

Lichen Biomonitoring of Airborne Microplastics in Milan (N Italy).

This study investigated the deposition of airborne microplastics (MPs) in the urban area of Milan across 12 sites and at a background control site (northern Italy) using 3-month transplants of the fruticose lichen species Evernia prunastri (exposed in triplicate). The primary objective was to evaluate the use of lichen transplants for the assessment of MP deposition; as such, the study sites spanned a gradient in vehicular traffic and population density across four concentric land-use zones (i.e., urban parks, centre, semi-periphery, and periphery). A total of 149 MP particles were detected in the exposed lichen samples; 94.6% were classified as fibres and 5.4% as fragments. The control site and urban parks experienced a similar number of MPs per gram of dry lichen (20-26 MP/g), while a higher number of MPs were detected in central and peripheral areas (44-56 MP/g), with a clear increasing gradient from the city centre towards the periphery. We estimated the MP deposition in Milan to be in the range of 43-119 MPs m2/d, indicating that people living in Milan are exposed to airborne MPs, with potential health effects. This study suggests that lichens are suitable biomonitors of airborne MPs under a relatively short exposure of three months in urban environments.

Contrasting effects of vegetation cover and site condition on biocrust communities in subhumid drylands

AbstractQuestionsBiocrusts perform critical functional roles in drylands, where they are regulated predominantly by differences in climate and soils. We asked whether biocrust cover and composition differ among sites of varying vegetation cover and condition.LocationSubhumid drylands in the Namoi Region, eastern Australia.MethodsWe assessed the effects of different vegetation strata (trees, shrubs, groundcover) and site vegetation condition (index of quality based on vascular plant richness, and the proportion of perennial and native vascular plants) on the cover, richness and composition of biocrust communities at 43 sites in semi‐arid eastern Australia.ResultsWoody plant cover at our sites was negatively related to biocrust cover and richness, but there was only a weak relationship between groundstorey plant cover and biocrusts, suggesting that woody plants are not facilitating biocrusts in this environment. Conversely, greater site condition was strongly associated with richer and more extensive biocrust communities, likely driven by a common response to livestock grazing intensity. There was also a significant multivariate association between biocrust composition and vegetation condition. For example, sites of poorer condition were occupied by generalist taxa, typically short mosses and squamulose lichens, while sites in better condition were characterised by a richer assemblage that included foliose and fruticose lichens, and taller, disturbance‐sensitive mosses.ConclusionsOur study provides empirical evidence of the negative relationship between woody plant cover and biocrusts (amensalism), and the filtering effect of vegetation condition on different biocrust taxa. Predicted drier climates could enhance biocrust dominance by suppressing woody plant growth, while intensified land‐use disturbances are likely to filter biocrust specialists such as fruticose and foliose lichens that are associated with sites in better condition.

Reduction in biomass of freshwater arctic vegetation by foraging and nesting hyperabundant herbivores shows recovery

AbstractArctic‐nesting geese are specialist herbivores of grasses and sedges (collectively, graminoids). Under moderate grazing pressure, these migratory herbivores can create and maintain arctic grazing lawns with high nutritional content and low aboveground biomass. Nutrient and energy subsidies from southern agricultural landscapes during winter have improved survival among populations of Ross's (Anser rossii) and lesser snow geese (Anser caerulescens caerulescens), leading to marked population growth. Resulting goose hyperabundance has raised conservation concern for resilience of arctic ecosystems to withstand cumulative and intense pressures of herbivory and nest construction. We used both design‐based (experimental herbivore exclosures) and model‐based methods to investigate changes to plant community structure in direct response to foraging and nesting by these species within the Queen Maud Gulf (Ahiak) Migratory Bird Sanctuary, Nunavut, Canada. Annual nest construction and foraging by up to ~1.3 million geese at a large colony at Karrak Lake markedly reduced aboveground biomass of forage (graminoids) and non‐forage (foliose and fruticose lichens) vegetation, with spatial variation in reduction associated with intensity of use by geese. Within vast brood‐rearing regions, foraging reduced above‐ and belowground plant biomass of lowland plant communities by 61% and 29%, respectively, between 1994 (when herbivore exclosures were established) and 2017. In addition to landscape diversity associated with abiotic properties created by geomorphic processes, long‐term herbivory by geese further increased spatial heterogeneity in vegetation at the landscape scale. Although foraging geese nearly completely depleted aboveground plant biomass in some parts of their brood‐rearing areas, belowground biomass was largely conserved, and thus, plant communities had strong potential for aboveground regeneration. We propose that the effects of high‐density nesting and foraging by Ross's and lesser snow geese in the central Canadian Arctic, while extensive, are ephemeral and prone to reversion following cessation of grazing and nesting pressure, such as that afforded by shifts in herbivore distribution or local population decline.