Factors at multiple scales influence the composition of terricolous lichen communities in temperate semi-arid sandy grasslands

Inland dune ecosystems are rich in terricolous lichen species. However, these communities are sensitive to human activities, both locally and globally. Since terricolous lichens have a dominant role in semi-arid sandy grasslands, it is important to explore the composition of their communities and the environmental factors affecting them. We studied the structure of the terricolous lichen assemblages of calcareous grassland in an inland duneland ecosystem by comparing the lichen communities of arid and humid dune sides on two sites with different disturbance histories. Microcoenological data were collected according to the Braun-Blanquet method. Environmental variables include the cover of bare soil, moss, litter, herb cover and height of herbs. We investigated the relationship of these variables and the presence and absence data of terricolous lichen species to sites and dune side. We found that the site had a significant effect on species richness that might reflect the different types and severity of previous disturbance events at the studied sites. On a smaller, ‘dune’ scale, in general lower herb cover and height and a higher moss cover were characteristic of arid dune sides. Most of the frequent species were negatively affected by higher moss cover. Some lichen species were more abundant (e.g. Cladonia furcata) or found only (e.g. Xanthoparmelia subdiffluens, Gyalolechia fulgens) on arid dune sides, while others preferred (e.g. C. pyxidata) or occurred only on (e.g. Peltigera species, C. rei) humid sides. It was observed that the impact of the dune side on several variables differed between sites. The diverse microhabitat types, microclimate and landscape structure, results in species-rich and valuable terricolous lichen communities forming in inland dune ecosystems.

Succession of Xeric Calcareous Grassland Toward Thermophilous Oak Forest: The Case of Abava Valley, West Latvia

The succession of semi-natural xeric calcareous grassland plant communities toward deciduous forest communities is poorly studied in Latvia. There is insufficient knowledge on the natural transformation of dry calcareous grasslands of Festuco-Brometea into thermophilous quasi-climax oak forest communities of Quercetea pubescentis that are very rare in Latvia. In this paper, a geobotanical study is presented that included studies of soils, tree age, spatial pattern of trees, vegetation composition of different succession stages, and analysis of environmental factors. The study was conducted in the Abava Valley, West Latvia, an area that is unique with species-rich xeric calcareous Festuco-Brometea grasslands, thermophilous oak forests dominated by Quercus robur, and intermediate secondary succession stages with young to medium-aged Juniperus communis and Pinus sylvestris formations.

Local and landscape responses of biodiversity in calcareous grasslands

Across Europe, calcareous grasslands become increasingly fragmented and their quality deteriorates through abandonment and land use intensification, both affecting biodiversity. Here, we investigated local and landscape effects on diversity patterns of several taxonomic groups in a landscape of highly fragmented calcareous grassland remnants. We surveyed 31 grassland fragments near Göttingen, Germany, in spring and summer 2017 for vascular plants, butterflies and birds, with sampling effort adapted to fragment area. Through regression modelling, we tested relationships between species richness and fragment size (from 314 to 51,395 m2), successional stage, habitat connectivity and the per cent cover of arable land in the landscape at several radii. We detected 283 plant species, 53 butterfly species and 70 bird species. Of these, 59 plant species, 19 butterfly species and 9 bird species were grassland specialists. Larger fragments supported twice the species richness of plants than small ones, and hosted more species of butterflies, but not of birds. Larger grassland fragments contained more grassland specialist plants, but not butterfly or bird specialists. Increasing amounts of arable land in the landscape from 20 to 90% was related to the loss of a third of species of plants, and less so, of butterflies, but not of birds. Per cent cover of arable land negatively correlated to richness of grassland specialist plants and butterflies, but positively to grassland specialist birds. We found no effect by successional stages and habitat connectivity. Our multi-taxa approach highlights the need for conservation management at the local scale, complemented by measures at the landscape scale.

Carbon storage in phosphorus limited grasslands may decline in response to elevated nitrogen deposition: a long term field manipulation and modelling study

<p>In ecosystems where nitrogen (N) limits plant productivity, N deposition can stimulate plant growth, and consequently, promote carbon (C) sequestration by increasing input of detrital C and other forms of plant C to the soil. However, other forms of nutrient limitation such as phosphorus (P) limitation and N-P co-limitation are widespread and may increase in prevalence with N deposition. Our understanding of how terrestrial ecosystem C, N and P cycling may be affected by N deposition when N is not the sole limiting resource is fairly limited. In this work, we investigate the consequences of enhanced N addition on C, N and P cycling in grasslands that exhibit contrasting forms of nutrient limitation.</p><p>We do so by collecting data from a long-term nutrient manipulation experiment on two N-P co-limited grasslands; an acidic grassland of stronger N-limitation and a calcareous grassland of stronger P limitation, and integrating this into a mechanistic C, N and P cycling model (N14CP). To simulate the experimental grasslands and explore the role of P access mechanisms in determining ecosystem state, we allowed P access to vary, and compared the outputs to plant-soil C, N and P data. Combinations of organic P access and inorganic P availability most closely representing data were used to simulate the grasslands and quantify their temporal response to nutrient manipulation.</p><p>The modelled grasslands showed contrasting responses to simulated N deposition. In the acidic grassland, N addition greatly increased C stocks by stimulating biomass productivity, but the same N treatments reduced the organic C pool in the calcareous grassland. Nitrogen deposition exacerbated P limitation in the calcareous grassland by reducing the size of the bioavailable P pool to plants, reducing biomass input to the soil C pool. Plant acquisition of organic P played an important role in determining the nutrient conditions of the grasslands, as both simulated grasslands increased organic P uptake to meet enhanced P demand driven by N deposition. Greater access to organic P in the acidic grassland prevented a shift to P limitation under elevated levels of N deposition, but organic P access was too low in the calcareous grassland to prevent worsening P limitation.</p><p>We conclude that grasslands of differing limiting nutrients may respond to N deposition in contrasting ways, and stress that as N deposition shifts ecosystems toward P limitation, a globally important carbon sink risks degradation.</p>

Increasing connectivity enhances habitat specialists but simplifies plant–insect food webs

Strong declines of grassland species diversity in small and isolated grassland patches have been observed at local and landscape scales. Here, we study how plant–herbivore interaction webs and habitat specialisation of leafhopper communities change with the size of calcareous grassland fragments and landscape connectivity. We surveyed leafhoppers and plants on 14 small (0.1–0.6 ha) and 14 large (1.2–8.8 ha) semi-natural calcareous grassland fragments in Central Germany, differing in isolation from other calcareous grasslands and in the percentage of arable land in the surrounding landscape (from simple to complex landscapes). We quantified weighted trophic links between plants and their phytophagous leafhoppers for each grassland fragment. We found that large and well-connected grassland fragments harboured a high portion of specialist leafhopper species, which in turn yielded low interaction diversity and simple plant-leafhopper food webs. In contrast, small and well-connected fragments exhibited high levels of generalism, leading to higher interaction diversity. In conclusion, food web complexity appeared to be a poor indicator for the management of insect diversity, as it is driven by specialist species, which require high connectivity of large fragments in complex landscapes. We conclude that habitat specialists should be prioritized since generalist species associated with small fragments are also widespread in the surrounding landscape matrix.

Allelopathic influence of medicinal plant Filipendula vulgaris Moench on germination process

The allelopathic potential of medicinal plant Filipendula vulgaris Moench, originated from two natural habitats: calcareous grasslands and humid meadows, was investigated using radish (Raphanus sativus L. var. radicula Pers.) as a model plant. Suppression influence of aqueous extracts at concentrations: 1%, 5%, 10%, obtained separately from under and aboveground parts of the species, was studied testing germination capacity, biomass and biometry of seedling, and electrolyte leakage. Additionally, two cultivars of the radish were used to test the sensitivity of frequently used plant in the laboratory tests. This study revealed the inhibiting effect of high concentration aqueous extracts from F. vulgaris organs on the germination of radish. It was significant for seed vigour index, speed emergence, germination stress tolerance index, and mean germination time. However, the stimulating effect of 1% of aqueous extracts from dropwort roots and shoots on the germination indexes was documented. Similarly, low concentration extracts had a positive effect on seedling elongation which was visible in biometric analyses and inhibition percentage index but it was not so obvious in the biomass analyses. In general, the aboveground extracts from dropwort grown on calcareous grassland demonstrated higher allelopathic potential than extracts from underground parts and meadow habitat.

Carbon storage in phosphorus limited grasslands may decline in response to elevated nitrogen deposition: a long-term field manipulation and modelling study

In many temperate ecosystems, nitrogen (N) limits productivity, meaning anthropogenic N deposition can stimulate plant growth and subsequently carbon (C) sequestration. Phosphorus (P) and N-P co-limited grasslands are widespread, yet there is limited understanding of their responses to N deposition, which may transition more ecosystems toward P-limited or N-P co-limited states. Here, we investigate the consequences of enhanced N addition on the C-N-P pools of grasslands in different states of nutrient limitation. We explored the response of a long-term nutrient-manipulation experiment on two N-P co-limited grasslands; an acidic grassland of stronger N-limitation and a calcareous grassland of stronger P-limitation, by combining data with an integrated C-N-P cycling model (N14CP). To explore the role of P-access mechanisms in determining ecosystem state, we allowed P-access to vary, and compared the outputs to plant-soil C-N-P data. Combinations of organic P access and inorganic P availability most closely representing data were used to simulate the grasslands and quantify their temporal response to nutrient manipulation. The model suggested N additions have increased C stocks in the acidic grassland, but decreased them in the calcareous, where N provision exacerbated P-limitation and reduced biomass input to the soil. Furthermore, plant acquisition of organic P may play an important role in reducing P-limitation, as both simulated grasslands increased organic P uptake to meet P demand. We conclude that grasslands of differing limiting nutrients may respond to N deposition in contrasting ways, and stress that as N deposition shifts ecosystems toward P-limitation, a globally important carbon sink risks degradation.