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In weed biocontrol, the release of multiple candidates has been proposed as a way to increase herbivore load and thus impact on the target weed. However, the use of multiple herbivorous species may reduce overall herbivore load due to interspecific interactions. We assessed whether a combined application of two Pyropteron spp. (Lepidoptera: Sesiidae) with root-boring larvae can increase larval infestation rate and impact on two Rumex weeds (Caryophyllales: Polygonaceae). In a laboratory assay (‘behavioural experiment’), interference competition was assessed by comparing the survival of a single larva (no competition), of four conspecific larvae (intraspecific competition) and of two larvae of each species (interspecific competition). In a common garden study (‘infestation and impact experiment’), the outcomes of competitive interactions were assessed on potted plants with single and mixed species applications of the two Pyropteron species using a replacement design. In the behavioural experiment, larval survival was similarly reduced under intra- and interspecific competition compared to no competition, suggesting strong interference competition among larvae independent of the Pyropteron species. In the infestation and impact experiment, mixed application did only scarcely increase herbivore load. Increased herbivore load was found to increase root decay when applied in an inundative approach by placing eggs directly on Rumex plants. However, a joint application of two Pyropteron species did not increase the impact. We propose that detailed behavioural and impact studies be conducted to assess the likely outcome of using multiple candidates in biocontrol programs to minimize associated risks with multiple species introductions.

An earlier version of this article was a keynote presentation at the 29th General Meeting of the European Grassland Federation hosted by France in 2022 (www.europeangrassland.org).; International audience; Climate change associated with a greater variability of inter-and intra-annual droughts and the occurrence of extreme events act in combination to challenge semi-natural and sown productive grasslands in Europe. Successful plant strategies under drought strongly depend on stress intensity. Drought resistance to maintain leaf growth under moderate stress trades off with drought survival after growth cessation under life-threatening drought. Substantial intra-specific variability exists in key forage grasses originating from the Mediterranean to the cool-temperate climates and represents a great potential for adaptation of future ecotypes and cultivars to a larger range of drought intensities. Plant species diversity offers an opportunity to stabilize forage production in two ways. First, growth reduction under stress is significantly smaller for diverse compared to simple plant communities because the former offers the opportunity to include drought-resistant (or drought-surviving) species. Second, positive interactions among species increase ecosystem functioning of more diverse plant communities under moderate drought, allowing them to compensate for drought-induced yield reductions. Currently, available cultivars of perennial forage species adapted to dry climate are still rare and only a few forage species are used in productive systems. Thus, both intra-and inter-specific plant diversity should be better valued to reduce vulnerability and increase resilience of productive grasslands.

The degree to which elevated CO

Experiments show that elevated atmospheric CO2 (eCO2) often enhances plant photosynthesis and productivity, yet this effect varies substantially and may be climate sensitive. Understanding if, where and how water supply regulates CO2 enhancement is critical for projecting terrestrial responses to increasing atmospheric CO2 and climate change. Here, using data from 14 long-term ecosystem-scale CO2 experiments, we show that the eCO2 enhancement of annual aboveground net primary productivity is sensitive to annual precipitation and that this sensitivity differs between woody and grassland ecosystems. During wetter years, CO2 enhancement increases in woody ecosystems but declines in grass-dominated systems. Consistent with this difference, woody ecosystems can increase leaf area index in wetter years more effectively under eCO2 than can grassland ecosystems. Overall, and across different precipitation regimes, woody systems had markedly stronger CO2 enhancement (24%) than grasslands (13%). We developed an empirical relationship to quantify aboveground net primary productivity enhancement on the basis of changes in leaf area index, providing a new approach for evaluating eCO2 impacts on the productivity of terrestrial ecosystems.

1. Green alder shrubs Alnus viridis increasingly overgrow European mountain pastures but hinder natural forest succession. This nitrogen-fixing, autochthonous invasive species has numerous negative effects including the loss of biodiversity and landscape aesthetic, eutrophication of soils and downstream waters, and greenhouse gas emission. Over centuries, A. viridis encroachment was impeded by grazing livestock, particularly goats. However, in modern agriculture, livestock numbers decreased on remote mountain pastures and goat farming became unprofitable. 2. A grazing experiment tested if hardy breeds of the more economically attractive livestock species, cattle and sheep can replace goats as A. viridis antagonists. On a subalpine pasture heavily encroached by A. viridis, space use and debarking (bark foraging) by Dexter cattle, Engadine sheep and Pfauen goats were analysed using GPS tracking and vegetation mapping. 3. Dexter cattle used space least evenly (Camargo evenness: cattle = 0.39; sheep = 0.52; and goats = 0.47) and preferred flat slopes and open pastures. They spent least time foraging in A. viridis stands (relative presence while foraging: cattle = 0.55; sheep = 0.76; and goats = 0.80). Dexter cattle did not debark any A. viridis, but damaged shrubs by trampling. 4. Engadine sheep visited A. viridis stands nearly as often as goats, but preferred flat slopes, short vegetation and shrub edges more clearly than goats. This sheep breed debarked significantly more A. viridis branches (average 244 branches per paddock; 7.4% of all A. viridis branches) than goats (45; 0.8%). Goats preferred mountain-ash shrubs Sorbus aucuparia covering only 2% of the shrub layer. 5. Synthesis and applications. Green alder shrubs, controlled by goats traditionally, overgrow valuable mountain pasture ecosystems today. Cattle, kept instead of goats, may slow down but not hinder shrub encroachment, because they avoid shrub stands and do not debark green alder. However, this study is the first to show that Engadine sheep are even better suited for green alder clearance than goats. Moreover, if management goals include forest re-establishment, Engadine sheep outperform goats, because they debark green alder (which hinders forest regeneration), but do not destroy elderberry—a valuable forest pioneer. Hardy breeds are an important tool to maintain biodiverse, open pastures, restore natural mountain forests and mitigate the negative environmental effects of shrub encroachment., Journal of Applied Ecology, 59 (5), ISSN:0021-8901, ISSN:1365-2664

The degree to which elevated CO2 concentrations (e[CO2]) increase the amount of carbon (C) assimilated by vegetation plays a key role in climate change. However, due to the short-term nature of CO2 enrichment experiments and the lack of reconciliation between different ecological scales, the effect of e[CO2] on plant biomass stocks remains a major uncertainty in future climate projections. Here, we review the effect of e[CO2] on plant biomass across multiple levels of ecological organization, scaling from physiological responses to changes in population-, community-, ecosystem-, and global-scale dynamics. We find that evidence for a sustained biomass response to e[CO2] varies across ecological scales, leading to diverging conclusions about the responses of individuals, populations, communities, and ecosystems. While the distinct focus of every scale reveals new mechanisms driving biomass accumulation under e[CO2], none of them provides a full picture of all relevant processes. For example, while physiological evidence suggests a possible long-term basis for increased biomass accumulation under e[CO2] through sustained photosynthetic stimulation, population-scale evidence indicates that a possible e[CO2]-induced increase in mortality rates might potentially outweigh the effect of increases in plant growth rates on biomass levels. Evidence at the global scale may indicate that e[CO2] has contributed to increased biomass cover over recent decades, but due to the difficulty to disentangle the effect of e[CO2] from a variety of climatic and land-use-related drivers of plant biomass stocks, it remains unclear whether nutrient limitations or other ecological mechanisms operating at finer scales will dampen the e[CO2] effect over time. By exploring these discrepancies, we identify key research gaps in our understanding of the effect of e[CO2] on plant biomass and highlight the need to integrate knowledge across scales of ecological organization so that large-scale modeling can represent the finer-scale mechanisms needed to constrain our understanding of future terrestrial C storage.

Compared to monocultures, multi‐species swards have demonstrated numerous positive diversity effects on aboveground plant performance, such as yield, N concentration, and even legacy effects on a following crop. Whether such diversity effects are seen in the soil microbiome is currently unclear. In a field experiment, we analyzed the effect that three plant species (a grass, forb, and legume), and mixtures of these, had on soil fungal and bacterial community structures, as well as their associated legacy effects under a following crop, the grass Lolium multiflorum. We utilized six sward types, three monocultures (Lolium perenne, Cichorium intybus and Trifolium pratense), two bi‐species mixtures, and a mixture of the three species. Soil samples were taken from these swards in March (at the end of a three year conditioning phase) and in June, August, and September after L. multiflorum was established, that is, the legacy samplings. When present, the differing monocultures had a significant effect on various aspects of the fungal community: structure, OTU richness, the relative abundance of the phylum Glomeromycota, and indicator OTUs. The effect on bacterial community structure was not as strong. In the multi‐species swards, a blending of individual plant species monoculture effects (identity effect) was seen in (a) fungal and bacterial community structure and (b) fungal OTU richness and the relative abundance of the Glomeromycota. This would indicate that plant species identity, rather than diversity effects (i.e., the interactions among the plant species), was the stronger determinant. During the legacy samplings, structural patterns in the fungal and bacterial communities associated with the previous swards were retained, but the effect faded with time. These results highlight that plant species identity can be a strong driver of soil microbial community structures. They also suggest that their legacy effect on the soil microbiome may play a crucial role in following crop performance., We investigated the effect of differing plant functional types, that is, grass, forb, and legume as well as various combinations of these, and their associated legacy effects on microbial community structure using amplicon‐based metagenomics.

Proanthocyanidins (PAs) in forages may be present in either soluble (S-PA) or non-extractable (NE-PA) form. Despite potential benefits of the NE-PA in ruminant nutrition, few studies have analyzed NE-PA in forages. This study examined the impact of a range of conditions on S-PA as well as protein- and fiber-bound PA (the NE-PA fractions) in sainfoin (Onobrychis viciifolia). Thus, five sainfoin accessions in either generative or vegetative stage were subjected to drought for 18 weeks and sampled repeatedly for PA analysis. Drought-stressed plants increased S-PAs on average by 59% across all accessions yet only in the vegetative stage. In contrast, NE-PA concentrations were generally lower (on average 15% of the total PAs) and unaffected by drought. Thus, for sainfoin, the low and stable concentration of NE-PAs across accessions, growth stages, and drought conditions should have a low, predictable impact on the future sainfoin analyses and feeding studies.

Aims We investigated the legacy effects of a previous ley’s legume proportion on the performance of a following grass crop in a rotation. Methods In April 2015, a pure Lolium multiflorum L. crop was sown after the removal of legume containing swards (0–100% legumes), and was harvested four times over the following one-year period (3 times in 2015 and once the following April 2016). Labeled 15N fertilizer (50 kg N ha−1) was applied during the 2nd and 3rd re-growth periods to determine N fluxes. Results Across the one-year period, a significant legume-legacy induced increase in biomass yield of L. multiflorum was observed over the entire range of previous legume proportions when compared against the non-legume ley, the effect being 2.15 and 1.73 t ha−1 (P ≤ 0.001 each) in swards with 50% and 100% previous legume proportion, respectively, or up to +31%. The legume-legacy effect on biomass yield was most pronounced at the 1st harvest (June) and persisted into the 2nd harvest in August (P ≤ 0.05 both, over the entire range of previous legume proportion), though was no longer evident at the 3rd harvest (September). Importantly, the legume-legacy effect returned in the 4th harvest in April (P ≤ 0.05). Examining the source of N contributing to N yield confirmed that more N was derived from the soil at harvest 1 and 2 for previous legume containing leys (P ≤ 0.001) compared to those which contained no legumes, with a significant increase still seen for legume mixtures at harvest 3 (P ≤ 0.01). Conclusions The results demonstrate a sustained soil-transferred performance-enhancing legacy effect on a following crop in a rotation, with previous legume proportions of 50% having a comparable effect compared with that of a previous legume monoculture.

Grasslands comprised of grass-legume mixtures could become a substitute for nitrogen fertiliser through biological nitrogen fixation (BNF) which in turn can reduce nitrous oxide emissions directly from soils without negative impacts on productivity. Models can test how legumes can be used to meet environmental and production goals, but many models used to simulate greenhouse gas (GHG) emissions from grasslands have either a poor representation of grass-legume mixtures and BNF, or poor validation of these features. Our objective is to examine how such systems are currently represented in two process-based biogeochemical models, APSIM and DayCent, when compared against an experimental dataset with different grass-legume mixtures at three nitrogen (N) fertiliser rates. Here, we propose a novel approach for coupling DayCent, a single species model to APSIM, a multi-species model, to increase the capability of DayCent when representing a range of grass-legume fractions. While dependent on specific assumptions, both models can capture the key aspects of the grass-legume growth, including biomass production and BNF and to correctly simulate the interactions between changing legume and grass fractions, particularly mixtures with a high clover fraction. Our work suggests that single species models should not be used for grass-legume mixtures beyond about 30% legume content, unless using a similar approach to that adopted here.

Grass-legume mixtures characterized by high productivity, efficient nitrogen (N) use and strong weed suppression were proposed to increase sustainability of grassland production. Adding competitive forbs to grassclover mixtures can be expected to further enhance the high productivity of grass-clover mixtures. This study investigates whether and to what extent adding forbs to a grass-clover mixture results in yield gains, and estimates the contributions of forb species (identity effect) and interactions with the grass-clover mixture (diversity effect) to these gains. It further examines the effectiveness of weed suppression in forb-containing grass-clover mixtures. Fifteen pure and mixed stands, all comprising the grass Lolium perenne L. and the legume Trifolium pratense L., and one or three competitive forb species (Cichorium intybus L., Carum carvi L., Plantago lanceolata L.) were established in a two-year field experiment and fertilised at two levels of N application. The diversity effect between P. lanceolata and the L. perenne-T. pratense mixture and a strong identity effect of P. lanceolata jointly contributed to yield gains of 10–21% over the binary L. perenne-T. pratense reference mixture for a wide range of P. lanceolata proportions across years and N fertilisation levels. In contrast, comparably smaller diversity and/or identity effects of C. intybus and C. carvi resulted in maximal yield gains of 5% and 7%, respectively, occurring at a narrower proportional range, but also in yield losses at high forb proportion. Including up to 80% forb in the L. perenne-T. pratense mixture effectively maintained weed suppression, but the degree of weed suppression decreased with increasing forb proportion in the following year. Including selected forbs, especially P. lanceolata, in productive grass-clover mixtures is promising for further enhancing productivity, meanwhile effectively suppressing short-term weed growth in intensively managed grasslands.

Introduction Reoccurring drought events can severely restrict forage production. However, experimentally drought stressed temperate forage grasslands have recently been reported to recover quickly after drought stress and re-wetting (DRW) and to be even more productive after drought than non-drought stressed control plots (Hofer et al., 2017; Hahn et al., in press). Although several studies show increased nutrient availability and microbial activity after DRW in grasslands (Bünemann et al., 2013; Sundert et al., 2020), an in-depth understanding if or how these mechanisms determine forage yield recovery is still missing.Methods This study examined the effect of a 2-month experimental summer drought under different nitrogen (N) fertilizer applications on the recovery of high-input Lolium perenne swards after re-wetting. Yield performance, physiology, nutrient availability and soil microbial activity were assessed over 2 years during and after the drought treatment. In addition, a post-drought transplantation experiment of control and DRW soil and plants withdrawn from the field was conducted to disentangle plant physiological and soil nutrient cycling effects on yield recovery after drought.Results Under all N applications, DRW outperformed the control yield in the field and showed higher N mineralization rates and higher soil N and K availabilities. Transplanted DRW plants showed longer but thinner leaves and decreased yields compared to control plants, irrespective of the soil’s DRW treatment. In contrast, DRW soils induced strongly increased L. perenne yields (on average +25%) compared to control soils. In summary, our data show that despite impaired plant growth after DRW, formerly drought stressed swards surpass control yields by profiting of higher mineralization rates and higher nutrient availability.ReferencesBünemann EK, Keller B, Hoop D, Jud K, Boivin P, Frossard E (2013) Increased availability of phosphorus after drying and rewetting of a grassland soil: processes and plant use. Plant and Soil 370: 511–526Hahn C, Lüscher A, Ernst-HaslerS, Suter M, Kahmen A (in press) Timing of drought in the growing season and strong legacy effects determine the annual productivity of temperate grasses in a changing climate. Biogeosciences.Hofer D, Suter M, Buchmann N, Lüscher A (2017) Nitrogen status of functionally different forage species explains resistance to severe drought and post-drought overcompensation. Agriculture, Ecosystems & Environment 236: 312–322Sundert KV, Brune V, Bahn M, Deutschmann M, Hasibeder R, Nijs I, Vicca S (2020) Post-drought rewetting triggers substantial K release and shifts in leaf stoichiometry in managed and abandoned mountain grasslands. Plant Soil 448: 353–368

Assessing the overall performance of ecosystems requires a quantitative evaluation of multifunctionality. We investigated plant species diversity effects on individual functions and overall multifunctionality in a grassland experiment with sown monocultures and mixtures comprising four key grass and legume species. Nitrogen fertilisation rates were 50, 150, and 450 kg N ha−1 yr−1 (N50, N150, N450). Ten functions were measured representing forage production, N cycling, and forage quality, all being related to either productivity or environmental footprint. Multifunctionality was analysed by a novel approach using the mean log response ratio across functions. Over three experimental years, mixture effects benefited all forage production and N cycling functions, while sustaining high forage quality. Thus, mixture effects did not provoke any trade-off among the analysed functions. High N fertilisation rates generally diminished mixture benefits. Multifunctionality of four-species mixtures was considerably enhanced, and mixture overall performance was up to 1.9 (N50), 1.8 (N150), and 1.6 times (N450) higher than in averaged monocultures. Multifunctionality of four-species mixtures at N50 was at least as high as in grass monocultures at N450. Sown grass–legume mixtures combining few complementary species at low to moderate N fertilisation sustain high multifunctionality and are a ‘ready-to-use’ option for the sustainable intensification of agriculture.

The frequency of extreme weather events, such as droughts, is assumed to increase and lead to alterations in ecosystem productivity and thus the terrestrial carbon cycle. Although grasslands typically show reduced productivity in response to drought, the effects of drought on grassland productivity have been shown to vary strongly. Here we tested, in a 2-year field experiment, if the resistance and the recovery of grasses to drought varies throughout a growing season and if the timing of the drought influences drought-induced reductions in annual aboveground net primary production (ANPP) of grasses. For the experiment we grew six temperate and perennial C3 grass species and cultivars in a field as pure stands. The grasses were cut six times during the growing season and subject to 10 week drought treatments that occurred either in the spring, the summer or the fall. Averaged across all grasses, drought-induced losses in productivity in spring were smaller (−20 % to −51 %) than in summer and fall (−77 % to −87 %). This suggests a higher resistance to drought in spring when plants are in their reproductive stage and their productivity is the highest. After the release from drought, we found no prolonged suppression in growth. In contrast, post-drought growth rates of formerly drought-stressed swards outperformed the growth rates of the control swards. The strong overcompensation in growth after the drought release resulted in relatively small overall drought-induced losses in annual ANPP that ranged from −4 % to −14 % and were not affected by the timing of the drought event. In summary, our results show that (i) the resistance in growth rates of grasses to drought varies across the season and is increased during the reproductive phenological stage when growth rates are highest; (ii) that the positive legacy effects of drought indicate a high recovery potential of temperate grasses to drought; and (iii) that the high recovery can compensate for immediate drought effects on total annual biomass production to a significant extent.

Experiments show that elevated atmospheric CO

Comprehensive mapping of Ecosystem Services (ES) is necessary to understand the impact of global change on crucial ES and to find strategies to sustain human wellbeing. Economic valuation of ES further translates their biophysical values into monetary values, which are then comparable across different ES and easily understandable to decision makers. However, a comprehensive synthesis of methods to measure ES indicators in grasslands, a central element of many landscapes around the globe, is still lacking, hampering the implementation of grassland ES-multifunctionality surveys. To identify suitable and recommendable methods, we reviewed the literature and evaluated labor intensiveness, equipment costs and predictive power of all methods. To facilitate the translation of biophysical ES into monetary terms, we further provide an overview of available methods for the economic valuation of ES. This review resulted in a toolbox comprising 85 plot-scale methods for assessing 29 different ES indicators for 21 provisioning, regulating, supporting or cultural ES. The available methods to measure ES indicators vary widely in labor intensiveness, costs, and predictive power. Based on this synthesis, we recommend 1) to choose direct over indirect methods and ES indicators, 2) to use the most accurate methods to estimate ES indicators, 3) to take into account that one ES indicator can have implications for more than one final ES, and 4) to utilize the wealth of available methods and indicators to assess as many ES for ES-multifunctionality studies as possible, especially including cultural ES. Moreover, the overview of approaches that can be used for the economic valuation of different grassland ES shall facilitate economic ES-multifunctionality assessments. Thus, this methodological guidance will considerably support researchers and stakeholders in setting up ES comprehensive assessments and monitoring schemes in grasslands and shall ultimately help overcome incomplete or superficial surveys based on single or few ES only., Ecosystem Services, 52, ISSN:2212-0416

Proanthocyanidins (PAs) in forages may be present in either soluble (S-PA) or non-extractable (NE-PA) form. Despite potential benefits of the NE-PA in ruminant nutrition, few studies have analyzed NE-PA in forages. This study examined the impact of a range of conditions on S-PA as well as protein- and fiber-bound PA (the NE-PA fractions) in sainfoin (

The frequency of extreme weather events, such as droughts, is assumed to increase leading to alterations of ecosystem productivity and thus the terrestrial carbon cycle. Although grasslands typically show reduced productivity in response to drought, their effects have been shown to vary quite dramatically. Here we tested in a two-year field experiment, if the resistance and the resilience of grasses towards drought varies throughout a growing season and if the timing of drought, thus, influences drought-induced reductions in annual net primary production (NPP) of grasses. For the experiment we grew six temperate and perennial C3 grass species in a field as monocultures. The grasses were cut six times during the growing season and subject to 10-week drought treatments that occurred either in the spring, the summer or the fall. Across all species, drought-induced losses of productivity were smaller (−20 % to −51 %) than in summer and fall (−77 % to −87 %). This suggests a higher resistance to drought in spring when the productivity of the grasses is the highest and plants are in their reproductive stage. After the release of drought, we found no prolonged suppression of growth. In contrast, post-drought growth rates of formerly drought-stressed swards outperformed the growth rates of the control swards. In 2014, the overcompensation after drought release was similar in all seasons, but differed in 2015. The strong overcompensation of growth after drought release resulted in relatively small overall drought-induced losses of annual ANPP that ranged between −4 % to −14 % and were not affected by the timing of the drought event. Our results show that (i) the resistance of growth rates in grasses to drought varies across the season and is positively correlated with growth rates in the control, (ii) that positive legacy effects of drought indicate a high resilience of temperate grasses to drought, and (iii) that the high resilience can compensate immediate drought effects on total annual biomass production to a large extent.

Fertilisation is a common practise in grass production systems performed to increase primary production, a supporting ecosystem service essential for other services. However, different fungal groups, like saprothropic fungi (SF) and the obligate symbionts arbuscular mycorrhizal fungi (AMF), have potential differential response to the fertilizer concentration and composition. Three controlled field experiments were utilised in our study, two medium-term (6 years) in the south of Sweden (SE) and one long-term experiment (46 year) in Switzerland (CH), all sampled in 2018. The Swedish sites included the same two factor treatment, i.e. four different plant mixtures and two (SE-Lanna) or three (SE-Alnarp) nitrogen fertilization levels (0, 60, 120 kg ha-1 yr-1); while the Swiss experiment included different proportions of N, P and K fertilization under different cutting regimes (CH-Bremgarten). The PLFA and NLFA (phospholipid- and neutral lipid fatty acid) analysis was used to estimate the fungal biomass (SF+AMF). The application of N was associated with a decrease in the AMF biomass, with significant effects with the application of 60 and 120 kg N ha-1 in SE-Alnarp, and 75 and 150 kg N ha-1 in CH-Bremgarten. On the other hand, the SF biomass was only negatively affected by the N fertilization in SE-Lanna (60 kg N ha-1) under the plant mixture that showed the biggest SF biomass in the unfertilized plot; and by the highest application of N in CH-Bremgarten. Our findings indicate that nitrogen fertilization influences microbial community structure and reduces the abundance of AMF, with these being more sensitive than SF to fertilizer application.

Grasslands cover a major share of the world’s agricultural area and are important for global food security. Plant species diversity in grasslands is known to increase and stabilize biomass yields. We economically evaluate these effects, using a rich dataset from 16 intensively managed grassland sites across Europe. We extend earlier research by accounting for plant species diversity effects on both quantity and quality of yields. Consequently, we can express plant species diversity effects in terms of milk production potential yields per hectare and potential revenues thereof. Plant species diversity not only increased milk production potential yields and thus revenues, but also reduced production risks. Thus, increasing plant species diversity resulted in higher certainty equivalents, for example, the certainty equivalent rose by +29% when comparing the average mixture to the average monoculture. For risk averse decision makers, this gain in certainty equivalent was mainly due to the increase in revenues (accounting for 90%) compared to the total insurance value (accounting for 10%). Overall, we show that farmers benefit economically from plant species diversity and that even a moderate increase in this diversity contributes to more stable grassland-based production. Thus, our results are highly relevant for future sustainable intensification of grassland-based production.

Abandonment of pastures and successional shrub expansion are widespread in European mountain regions. Moderate shrub encroachment is perceived beneficial for plant diversity by adding new species without outcompeting existing ones, yet systematic evidence is missing. We surveyed vegetation along 24 transects from open pasture into shrubland across the Swiss Alps using a new protocol distinguishing different spatial scales, shrub cover of each plot (2 x 2 m) and larger-scale zonal cover along the transect. Data were analysed using generalized linear models of shrub cover, shrub species and environmental conditions, such as geology, aspect or soil. Most shrub communities were dominated byAlnus viridis(62% of transects) andPinus mugo(25%), and the rest by other shrub species (13%). These dominant shrub species explained vegetation response to shrub cover well, without need of environmental variables in the model. Compared to open pasture,A. viridisresulted in an immediate linear decline in plant species richness and a marginal increase in beta-diversity (maximally + 10% at 35% cover). DenseA. viridishosted 62% less species than open pasture. InP. mugo,species richness remained stable until 40% shrub cover and dropped thereafter; beta-diversity peaked at 35% cover. Hence, scatteredP. mugoincreases beta-diversity without impairing species richness. In transects dominated by other shrubs, species richness and beta-diversity peaked at 40-60% shrub cover (+ 23% both).A. viridisreduced species richness in a larger area around the shrubs thanP. mugo. Therefore, effects of shrub encroachment on plant diversity cannot be generalized and depend on dominant shrub species., Alpine Botany, 130 (2), ISSN:1664-2201, ISSN:1664-221X

BACKGROUND AND AIMS: Grassland-based livestock systems in cool maritime regions are commonly dominated by grass monocultures receiving relatively high levels of fertilizer. The current study investigated whether grass–legume mixtures can improve the productivity, resource efficiency and robustness of yield persistence of cultivated grassland under extreme growing conditions over a period of 5 years. METHODS: Monocultures and mixtures of two grasses (Phleum pratense and Festuca pratensis) and two legumes (Trifolium pratense and Trifolium repens), one of which was fast establishing and the other temporally persistent, were sown in a field trial. Relative abundance of the four species in the mixtures was systematically varied at sowing. The plots were maintained under three N levels (20, 70 and 220 kg N ha(–1) year(–1)) and harvested twice a year for five consecutive years. Yields of individual species and interactions between all species present were modelled to estimate the species diversity effects. KEY RESULTS: Significant positive diversity effects in all individual years and averaged across the 5 years were observed. Across years, the four-species equi-proportional mixture was 71 % (N20: 20 kg N ha(–1) year(–1)) and 51 % (N70: 70 kg N ha(–1) year(–1)) more productive than the average of monocultures, and the highest yielding mixture was 36 % (N20) and 39 % (N70) more productive than the highest yielding monoculture. Importantly, diversity effects were also evident at low relative abundances of either species group, grasses or legumes in the mixture. Mixtures suppressed weeds significantly better than monocultures consistently during the course of the experiment at all N levels. CONCLUSIONS: The results show that even in the less productive agricultural systems in the cool maritime regions grass–legume mixtures can contribute substantially and persistently to a more sustainable agriculture. Positive grass–legume interactions suggest that symbiotic N(2) fixation is maintained even under these marginal conditions, provided that adapted species and cultivars are used.

Climate change is predicted to result in more severe weather events, including drought, which will affect forage production in agricultural grasslands. We evaluated the effects of an experimentally imposed drought on yields of monocultures and mixtures of intensively managed grassland communities comprising four species with contrasting functional traits (Lolium perenne L., Cichorium intybus L., Trifolium repens L., Trifolium pratense L.). Complete exclusion of precipitation was implemented in a common field experiment at two sites, resulting in an experimental drought at Wexford (Ireland) and Zurich (Switzerland). In the individual harvest at the end of the drought event, very strong yield reductions (up to −87%) occurred across all communities. In contrast, drought effects on annual yields of averaged monocultures and the equi-proportional four-species mixture were only −9% and −12%, respectively. These losses were much smaller than the yield advantage due to mixtures, which were 31% under drought and 34% under rainfed conditions. The large effect of mixtures on annual yield is attributed to complementarity among species with contrasting functional traits, and to mixture effects being active over the whole growing season and under drought. We attribute these relatively small drought effects on annual yield to the immediate recovery in harvest yields when soil water supply increased after the drought (resilience), the buffering effect of soil water at the beginning of rain exclusion, and the relatively long growing season that diluted the short-term effect of the drought event.

Aims Belowground legume nitrogen (N) composed of roots and rhizodeposition is an important N input to soils, but published data of belowground N vary broadly, probably due to extrapolation from short-term experiments and dissimilar growing conditions. We quantified belowground N inputs of red clover (Trifolium pratense L.) during two consecutive years in a clover-grass sward along a soil nutrient availability gradient. Methods We established a red clover-perennial ryegrass (Lolium perenne L.) model sward in microplots located in field plots of the DOK experiment, which has a 33-year history of organic and conventional cropping, resulting in a soil nutrient availability gradient. Four treatments were examined: the zero fertilisation control, bio-organic with half and full dose manure application, and the conventional system with mineral fertilisation at full dose. We studied the development of clover aboveground and belowground N using multiple pulse 15N urea leaf labelling. Results Belowground clover N increased over time and with rising nutrient availability and was proportional to aboveground clover N at all times. Belowground clover N amounted to 40% of aboveground clover N during two consecutive years, irrespective of the nutrient availability status. Belowground clover N development was initially dominated by fast root growth, followed by enhanced root turnover during the second year. Potassium availability limited clover growth and total N accumulation in treatments with low nutrient availability. Conclusions Belowground red clover N inputs could be estimated from aboveground N by a constant factor of 0.4, regardless of the nutrient availability and cultivation time. Root turnover led to a distinct absolute increase of N rhizodeposition over time. Hence, N rhizodeposition, with an 80% share of belowground N, was the predominant N pool at the end of the second year.

Publisher's version (útgefin grein), Grassland diversity can support sustainable intensification of grassland production through increased yields, reduced inputs and limited weed invasion. We report the effects of diversity on weed suppression from 3 years of a 31-site continental-scale field experiment. At each site, 15 grassland communities comprising four monocultures and 11 four-species mixtures based on a wide range of species' proportions were sown at two densities and managed by cutting. Forage species were selected according to two crossed functional traits, “method of nitrogen acquisition” and “pattern of temporal development”. Across sites, years and sown densities, annual weed biomass in mixtures and monocultures was 0.5 and 2.0 t DM ha−1 (7% and 33% of total biomass respectively). Over 95% of mixtures had weed biomass lower than the average of monocultures, and in two-thirds of cases, lower than in the most suppressive monoculture (transgressive suppression). Suppression was significantly transgressive for 58% of site-years. Transgressive suppression by mixtures was maintained across years, independent of site productivity. Based on models, average weed biomass in mixture over the whole experiment was 52% less (95% confidence interval: 30%–75%) than in the most suppressive monoculture. Transgressive suppression of weed biomass was significant at each year across all mixtures and for each mixture. Weed biomass was consistently low across all mixtures and years and was in some cases significantly but not largely different from that in the equiproportional mixture. The average variability (standard deviation) of annual weed biomass within a site was much lower for mixtures (0.42) than for monocultures (1.77). Synthesis and applications. Weed invasion can be diminished through a combination of forage species selected for complementarity and persistence traits in systems designed to reduce reliance on fertiliser nitrogen. In this study, effects of diversity on weed suppression were consistently strong across mixtures varying widely in species' proportions and over time. The level of weed biomass did not vary greatly across mixtures varying widely in proportions of sown species. These diversity benefits in intensively managed grasslands are relevant for the sustainable intensification of agriculture and, importantly, are achievable through practical farm-scale actions., We thank the many colleagues who have assisted this work. We thank M. Coll for her early contribution. Co-ordination of this project was supported by the EU Commission through COST Action 852 ‘Quality legume-based forage systems for contrasting environments’. M.T.S., R.L. and A.R. were supported by the Spanish Ministry of the Economy and Competitiveness through projects CARBOAGROPAS (CGL2006-13555- C03- 01/ BOS) and BIOGEI (CGL2013-49142- C2- 1- R) and the Ministry of the Environment through OPS (209/PC08/3-08.2). L.K. was supported by an award from Science Foundation Ireland (09/RFP/EOB2546). A.L., J.A.F., J.C. and M.S. were partly supported by the EU FP7 project ‘AnimalChange’ under grant agreement no. 266018.

Weeds in intensively managed grassland can result in substantial losses of forage yield and quality. We studied whether weeds could be suppressed sustainably by use of functionally diverse grassland mixtures with high resource capture and biomass yield. To this aim, growth of planted phytometers and of spontaneously establishing, unsown species were evaluated. To represent weeds, seedlings of five model species were grown up as phytometer plants in stands of forage leys under two precipitation regimes. Ley stands comprised monocultures and mixtures of two and four species with distinctly differing plant functional traits (PFTs) related to nitrogen (N) acquisition and rooting depth, including: Lolium perenne L. (PFT: non-N2-fixing, shallow-rooted), Cichorium intybus L. (non-N2-fixing, deep-rooted), Trifolium repens L. (N2-fixing, shallow-rooted), and Trifolium pratense L. (N2-fixing, deep-rooted). Five PFTs were measured from these ley species: leaf dry matter content, specific leaf area, leaf N and carbon (C) content, and the leaf C:N ratio. Survival of phytometer plants and biomass of unsown species was measured under rainfed conditions and during an experimentally induced, nine-week summer drought with complete rain exclusion. Mixtures with high functional dispersion (calculated from PFTs) and biomass yield suppressed phytometer plants and unsown species significantly more than mixtures with low functional dispersion. Under rainfed conditions, fourteen weeks after planting, survival of phytometer plants was 32% in the four-species mixture with the highest functional dispersion, while survival was 68% averaged across monocultures, the stands with the lowest functional dispersion. Surviving individuals had significantly smaller tiller number and rosette diameter in mixtures than in monocultures. Biomass of unsown species was 3.6 kg ha−1 in the four-species mixture, but was 13.0 kg ha−1 in averaged monocultures. The suppressive effect was equally apparent under drought conditions, where, at the end of the drought period, phytometer survival was 16% and 47% in the four-species mixture and averaged monocultures, respectively. During a six-week post-drought period, the suppressive effect of ley mixtures on phytometer plants was sustained. The strong suppressive effect of ley mixtures was explained by their superior capture for light and plant-available soil N. We conclude that cropping functionally diverse grassland mixtures could be a sustainable strategy to enhance weed suppression under rainfed and drought conditions.

Grass–legume mixtures have proven successful at improving the sustainability of grasslands. Their ability to suppress unsown species is particularly important for sainfoin (Onobrychis viciifolia), a forage crop with valuable bioactive compounds, yet low competitiveness. In this 3-year study, the suitability of six partner species cultivated in mixtures with sainfoin at different annual numbers of cuts and partner sowing densities were evaluated. Mixture yields outperformed average monoculture yields by 31%, reduced the ratio of unsown species by 65% and increased the symbiotic N2 fixation up to 158 kg ha−1. A key finding of the study was the highly differential patterns of development of the partner grass species over the 3 years. These patterns of development had a large effect on the persistency of the proportion of sainfoin in the mixtures, which varied in the third year between 17% (when grown with Dactylis glomerata) and 38% (with Lolium perenne). These findings contribute to the further development of sustainable grass–legume systems, as evidence for the successful cultivation of sainfoin as an alternative legume species can help diversification, and knowledge of mixture development supports more persistent legume proportions.

Forage species of intensively managed temperate grassland differ substantially in their drought responses. We investigated whether differences in resistance and resilience, based on biomass yield, are related to species nitrogen (N) acquisition and drought-induced N deficiency. A three-factorial field experiment was established with monocultures of four species (first factor) that differed in functional traits regarding N acquisition and rooting depth: Lolium perenne L. (shallow-rooted non-legume), Cichorium intybus L. (deep-rooted non-legume), Trifolium repens L. (shallow-rooted legume), and Trifolium pratense L. (deep-rooted legume). A ten-week summer drought was simulated (second factor) and compared to a rainfed control during two regrowths under drought and one regrowth during a subsequent six-week post-drought period. The distribution of applied fertiliser N (200 kg ha−1 year−1 in total) was manipulated (third factor) with plots receiving no N during drought or 60 kg N ha−1. Soil water availability during drought became increasingly restricted over time. Plant-available soil N was reduced up to 4- and 12-fold during the first and second regrowths under drought, respectively, but was increased up to 4-fold during the post-drought regrowth, compared to rainfed control conditions. Legumes were consistently less N-limited than non-legumes (P

Rising atmospheric carbon dioxide concentration ([CO2]) should stimulate biomass production directly via biochemical stimulation of carbon assimilation and indirectly via water savings caused by increased plant water use efficiency. Because of these water savings, the CO2 fertilisation effect should be stronger in drier sites, yet large differences among experiments in grassland biomass response to elevated CO2 appear unrelated to annual precipitation, preventing useful generalisations. Here we show that, as predicted, the impact of elevated CO2 on biomass production in 19 globally-distributed temperate grassland experiments reduces as mean precipitation in seasons other than spring increases but, unexpectedly, rises as mean spring precipitation increases. Moreover, because sites with high spring precipitation also tend to have high precipitation at other times, these effects of spring and non-spring precipitation on the CO2 response offset each other, constraining the response of ecosystem productivity to rising CO2. This explains why previous analyses were unable to discern a reliable trend between site dryness and the CO2 fertilisation effect. Thus, the CO2 fertilisation effect in temperate grasslands worldwide will be constrained by their natural rainfall seasonality such that the stimulation of biomass by rising CO2 could be substantially less than anticipated.

Climate models predict increased frequency and severity of drought events. At an Irish and Swiss site, experimental summer droughts were applied over two successive years to grassland plots sown with one, two or four grassland species with contrasting functional traits. Mean yield and plot-to-plot variance of yield were measured across harvests during drought and after a subsequent post-drought recovery period. At both sites, there was a positive relationship between species richness and yield. Under rainfed control conditions, mean yields of four-species communities were 32% (Wexford, Ireland) and 51% (Zürich, Switzerland) higher than in monocultures. This positive relationship was also evident under drought, despite significant average yield reductions (−27% at Wexford; −21% at Zürich). Four-species communities had lower plot-to-plot variance of yield compared to monoculture or two-species communities under both rainfed and drought conditions, which demonstrates higher yield stability in four-species communities. At the Swiss but not the Irish site, a high degree of species asynchrony could be identified as a mechanism underlying increased temporal stability in four-species communities. These results indicate the high potential of multi-species grasslands as an adaptation strategy against drought events and help achieve sustainable intensification under both unperturbed and perturbed environmental conditions.

Optimizing agricultural benefits of mixtures as compared to monocultures requires identification of effective combinations of plant species characteristics. To understand processes of yield formation in cultivated grasslands we assessed the effect of mixing four forage species with contrasting foliar architecture and seasonal shoot growth. The yield of each species and its seasonality, instantaneous and cumulative light interception, as well as the stratified leaf area index were measured in monocultures and 11 types of mixtures of four key species of productive temperate grasslands worldwide: Lolium perenne , Cichorium intybus , Trifolium repens and Trifolium pratense . The mixture with equal sown proportions of each species achieved 23–31% higher total yield than expected from the monocultures (mixture effect). Over the three experimental years, mixture yield was positively correlated to the seasonal asynchrony in shoot growth between component species ( r = 0.76, P L. perenne ). This leaves no potential for further improvement of light interception in mixtures. In the middle of the regrowth periods, when light interception was not yet complete, a mixture effect on instantaneous light interception was detected. However it was too small and too short-term to translate into mixture effects on light interception cumulated over the whole regrowth period. These results indicate that to achieve positive mixture effects on yield in productive cultivated grasslands, mixing species asynchronous in seasonal shoot growth is more important than mixing species with contrasting foliar architecture.

peer-reviewed 1.Due to climate change, an increasing frequency and severity of drought events are expected to impair grassland productivity, particularly of intensively managed temperate grasslands. 2.To assess drought impacts, a common field experiment to manipulate precipitation was set up at three sites (two Swiss and one Irish) using monocultures and mixtures with two and four key forage species. Species differed in their functional traits: a shallow-rooted non-legume (Lolium perenne L.), a deep-rooted non-legume (Cichorium intybus L.), a shallow-rooted legume (Trifolium repens L.) and a deep-rooted legume (Trifolium pratense L.). A 9-week summer drought was simulated, and soil water status, above-ground biomass yield and plant nitrogen (N) limitation were compared to a rainfed control. 3.Based on soil water measurements, the drought induced severe stress at both Swiss sites and extreme stress at the Irish site. Under severe stress, the legumes were more drought resistant and showed an average change in above-ground biomass (CAB, compared to rainfed control) of only −8% and −24% (for the two Swiss sites), while the non-legumes had an average CAB of −51% and −68%. The lower resistance of non-legumes coincided with an apparent limitation of plant N, which further increased under drought. Under extreme drought (Irish site), growth nearly ceased with an average CAB of −85%. 4.During a 6-week post-drought period with adequate water supply (Swiss sites), formerly drought-stressed species were highly resilient and either attained (legumes) or clearly outperformed (non-legumes) the yield level of the rainfed controls. This outperformance coincided with post-drought reductions in N limitation in formerly drought-stressed species. As a result, aggregated over the drought and the post-drought periods, a negative drought impact was found only for the shallow-rooted L. perenne at one of the severely stressed sites. 5.Significant overyielding by multispecies mixtures was evident under rainfed control conditions (+38% across all three sites, P < 0·05) and was equally apparent under severe drought (+50%, P < 0·05). This overyielding was greatest in mixtures with approximately equal species proportions and was sufficiently large that drought-stressed mixtures at least attained the same yield as the average of the rainfed monocultures. Under extreme drought, growth almost ceased in monocultures and mixtures. 6.Synthesis and applications. Yields of selected species of intensively managed temperate grasslands are either resistant to a single severe drought or are highly resilient as soon as soil moisture levels recover after the drought event. However, these forage species seem unable to cope with an extreme drought event. Combining species in mixtures can compensate for yield reductions caused by severe drought and it offers a practical management tool to adapt forage production to climate change. European Union Seventh Framework Programme. Grant Number: 266018

Rumex obtusifolius (Caryophyllales: Polygonaceae) is one of the most troublesome weeds in European grasslands and non-chemical control options are largely lacking. In this study, we assessed the potential of the native root-feeding specialist insect Pyropteron chrysidiforme (Lepidoptera: Sesiidae) for inundative biological control of R. obtusifolius. At multiple grassland sites, we applied P. chrysidiforme varying in developmental stage and level of protection onto R. obtusifolius to be examined in the subsequent autumn and spring. We consistently found the highest infestation resulting from the application of eggs (71 % of plants infested in autumn) with concomitantly elevated root decay and fewer rosettes compared to control plants. Moreover, in spring we found trends for associated decreases in biomass and number of shoots. Our findings support P. chrysidiforme as a promising biological control candidate of R. obtusifolius, but further investigations will be required to assess the consistency and long-term impacts of this novel approach.

Sainfoin (Onobrychis viciifolia Scop.) is a forage legume, which improves animal health and the environmental impact of livestock farming due to its proanthocyanidin content. To identify the impact of drought on acetone/water-extractable proanthocyanidin (PA) concentration and composition in the generative and vegetative stages, a rain exclosure experiment was established. Leaves of 120 plants from 5 different sainfoin accessions were sampled repeatedly and analyzed by UPLC-ESI-MS/MS. The results showed distinct differences in response to drought between vegetative and generative plants. Whereas vegetative plants showed a strong response to drought in growth (-56%) and leaf PA concentration (+46%), generative plants showed no response in growth (-2%) or PA concentration (-9%). The PA composition was stable across environments. The five accessions varied in PA concentrations and composition but showed the same pattern of response to the experimental treatments. These results show that the ontogenetic stage at which drought occurs significantly affects the plant's response.

Grasslands provide multiple Ecosystem Services (ES) such as forage provision, carbon sequestration or habitat provision. Knowledge about the trade-offs between these ES is of great importance for grassland management. Yet, the outcome of different management strategies on ES provision is highly uncertain due to spatial variability. We aim to characterize the provision (level and spatial variability) of grassland ES under various management strategies. To do so, we combine empirical data for multiple ES with spatially explicit census data on land use intensities. We analyzed the variations of five ES (forage provision, climate regulation, pollination, biodiversity conservation and outdoor recreation) using data from biodiversity fieldwork, experimental plots for carbon as well as social network data from Flickr. These data were used to calculate the distribution of modelled individual and multiple ES values from different grassland management types in a Swiss case study region using spatial explicit information for 17,383 grassland parcels. Our results show that (1) management regime and intensity levels play an important role in ES provision but their impact depends on the ES. In general, extensive management, especially in pastures, favors all ES but forage provision, whereas intensive management favors only forage provision and outdoor recreation; (2) ES potential provision varies between parcels under the same management due to the influence of environmental drivers, related to topography and landscape structure; (3) there is a trade-offs between forage provision and other ES at the cantonal level but a synergy between forage provision and biodiversity conservation within the grassland categories, due to the negative impact of elevation on both ES. Information about multiple ES provision is key to support effective agri-environmental measures and information about the spatial variability can prevent uncertain outputs of decision-making processes.

Rising atmospheric carbon dioxide concentration should stimulate biomass production directly via biochemical stimulation of carbon assimilation, and indirectly via water savings caused by increased plant water-use efficiency. Because of these water savings, the CO

Plant Ecology, 180 (1), ISSN:1385-0237, ISSN:1573-5052