Questions: What are the factors limiting the establishment of hemiparasitic Rhinanthus spp., ecosystem engineers promoting diversity and stability of communities, in restoration of species-rich meadows? How can these constraints be overcome?Location: Czech Republic, Central Europe.Methods: Sowing of Rhinanthus seeds in grasslands of different history, biotic and abiotic properties accompanied by a variety of management practices. Followed by consequent monitoring of establishment and population dynamics and synthesis of relevant literature resources.Conclusion: Mowing or grazing, litter removal, proper timing of sowing, and use of the seeds from local seed sources should considerably increase probability of Rhinanthus successful introduction. However, stochastic events like adverse weather conditions or damage through herbivory make the prediction of introduction success difficult.

Summary Dominance of native or alien competitive plants causes competitive exclusion of subordinate species and represents a major mechanism reducing biodiversity following land‐use changes. The successful competitive strategies may, however, be interfered with by parasitic plants, which withdraw resources from other plants' vasculature. Parasitism may strongly reduce the growth of the dominants, which may facilitate regeneration of other species and consequently trigger restoration of natural communities of high diversity. Here, we aim to provide robust empirical evidence demonstrating this restoration potential of parasitic plants. We present a case study testing suppressive effects of hemiparasitic Rhinanthus alectorolophus on competitive grass Calamagrostis epigejos. In recent decades, C. epigejos has invaded many high‐nature‐value semi‐natural grasslands of Central Europe, which is one of the prominent factors causing their biodiversity decline. We conducted three manipulative field experiments testing the effect of sowing of R. alectorolophus in different vegetation types infested by C. epigejos. Rhinanthus sowing was compared to different mowing treatments recommended as the ‘best practice’ management at respective sites. Rhinanthus alectorolophus established itself in most C. epigejos‐dominated plots where sown. Calamagrostis epigejos was virtually exterminated in 2 years in two of the experiments (dry meadow and industrial area). In the wet‐meadow experiment, the suppressive effect was variable as a result of uneven establishment success of Rhinanthus. In this experiment increased mowing intensity had an additional suppressive effect on C. epigejos. Rhinanthus also increased regeneration potential of other species by a temporary reduction of vegetation density. Restoration of target vegetation composition was, however, dependent on community context. Synthesis and applications. We demonstrated that hemiparasitic Rhinanthus alectorolophus is an accessible and efficient tool for targeted biological control of Calamagrostis epigejos, with a great potential to restore infested grassland vegetation. The strong effect of Rhinanthus is caused by interference with the underground storage and clonal growth strategy of Calamagrostis epigejos, which are both traits that underlie its competitive ability. The potential of native parasitic plants should be considered in restoration management of sites infested by competitive dominants, either alien or native.

Plant variation in nutrient concentrations encompasses two major axes. The first is connected to nitrogen (N) and phosphorus (P), reflects growth rate and has been designated as the leaf economics spectrum (LES) while the second follows the gradient in calcium (Ca) and magnesium (Mg) and mirrors cell structural differences. Here, we tested in grasslands whether the sum Ca + Mg concentrations is a better indicator of digestibility than LES constituents. Structural equation modelling revealed that the total effect size of N (0.30) on digestibility was much lower than that of Ca + Mg (0.58). The N effect originated predominantly from sampling date (biomass ageing), while the Ca + Mg effect largely from phylogenetic composition (proportion of monocots). Thus, plant variation in partially substitutable divalent cations seems to play a significant role in biomass digestion by ruminants. This finding contests, together with litter decomposition studies, the prominent role of the LES for understanding both fundamental ecological processes.

Summary1. Management of high-nature-value (HNV) grasslands follows agri-environmental schemes across large areas of Europe. Long-term agreements and restrictions of fertilizers cause soil nutrient impoverishment, but remarkably this quite often does not reduce biomass production. Therefore, we tested how species-rich vegetation copes with nutrient impoverishment under the most frequently used treatments, that is summer mowing and livestock grazing. 2. During 2011-2012 we studied, simultaneously, plant species composition, soil and biomass chemical properties in two equally designed experiments where mowing, grazing or leaving fallow have been applied since 2004. We asked whether soil-based (C org : N tot , plant-available P and K) and plant-based measures (N : P, N : K, K : P ratios and N-, P-, K-nutrition indices) indicate the same pattern of nutrient limitation as the observed productivity gradient. 3. Seven years of management application resulted in the lowest plant-available P under grazing and the lowest plant-available K under mowing, but neither grazed nor mown plots produced less biomass than fallow ones. Grazing supported dominance of grasses while mowing that of non-leguminous forbs. 4. Projection of nutrition indices to a common framework with nutrient ratios suggests that critical thresholds for diagnosis of nutrient limitation are a function of N deficiency. At biomass production of 2 t ha À1 a N-nutrition index of 50 yielded threshold N : P = 14Á0; hence, all our treatments with N : P of 9Á9-12Á5 should be N limited. 5. Inspecting the productivity gradient separately for each management, we found only soil C org : N tot negatively related to biomass production in mown plots indicating N limitation. However in grazed plots, positive association of biomass production with plant-available P and negative with biomass N : P and N : K suggested PK co-limitation. 6. Synthesis and applications. Mowing and grazing induced different patterns of soil nutrient impoverishment and nutrient limitation, but they did not reduce biomass production of highnature-value grasslands. Non-leguminous forbs prevailing under mowing precluded shortage of P, while grasses dominating under grazing efficiently captured N. We recommend designing agri-environmental measures that will encourage alternating mowing and grazing. This should promote coexistence of multiple forbs and grasses, balance nutrient limitation and ensure stable biomass production under future low-input scenarios.

Agri-environmental measures often require postponing of grassland defoliation until summer months. We investigated how this affects agronomic characteristics, i.e., biomass production and forage quality, in species-rich grasslands in the White Carpathian Mountains, Czech Republic. Three distinct grasslands (vegetation alliances Bromion erecti, Cynosurion cristati, Violion caninae) were selected for biomass sampling in three dates: mid-May, early June and end of June. Proportions of individual species from total biomass, biomass production, crude fibre concentration, organic matter digestibility and community functional properties (forage value, leaf dry matter content, specific leaf area) were determined. Dry matter standing biomass at the end of June was highest in Bromion with 3.5 t/ha, followed by Violion with 2.7 t/ha and Cynosurion with 2.3 t/ha. A steep decline in forage quality (increase in crude fibre and decrease in organic matter digestibility) during accumulation of aboveground biomass was recorded in formerly unmanaged Bromion grassland but remarkably not in formerly grazed Cynosurion and Violion grasslands where early spring dominants were partly replaced by later developing species, Agrostis capillaris and Trifolium spp. Abundance-weighted community functional properties were consistent with results obtained from biomass chemical analyses, thus the 'trait approach' can be used as a suitable surrogate of costly and labor-intensive laboratory procedures. Finally, we assume that the high degree of community seasonal development in Cynosurion and Violion, indicated here by a new community seasonal development index and by development in community specific leaf area, was accountable for the stabilization of forage quality later in the vegetation season.

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BackgroundCurrent plant – herbivore interaction models and experiments with mammalian herbivores grazing plant monocultures show the superiority of a maximizing forage quality strategy (MFQ) over a maximizing intake strategy (MI). However, there is a lack of evidence whether grazers comply with the model predictions under field conditions.Methodology/FindingsWe assessed diet selection of sheep (Ovis aries) using plant functional traits in productive mesic vs. low-productivity dry species-rich grasslands dominated by resource-exploitative vs. resource-conservative species respectively. Each grassland type was studied in two replicates for two years. We investigated the first grazing cycle in a set of 288 plots with a diameter of 30 cm, i.e. the size of sheep feeding station. In mesic grasslands, high plot defoliation was associated with community weighted means of leaf traits referring to high forage quality, i.e. low leaf dry matter content (LDMC) and high specific leaf area (SLA), with a high proportion of legumes and the most with high community weighted mean of forage indicator value. In contrast in dry grasslands, high community weighted mean of canopy height, an estimate of forage quantity, was the best predictor of plot defoliation. Similar differences in selection on forage quality vs. quantity were detected within plots. Sheep selected plants with higher forage indicator values than the plot specific community weighted mean of forage indicator value in mesic grasslands whereas taller plants were selected in dry grasslands. However, at this scale sheep avoided legumes and plants with higher SLA, preferred plants with higher LDMC while grazing plants with higher forage indicator values in mesic grasslands.ConclusionsOur findings indicate that MFQ appears superior over MI only in habitats with a predominance of resource-exploitative species. Furthermore, plant functional traits (LDMC, SLA, nitrogen fixer) seem to be helpful correlates of forage quality only at the community level.

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