Grassland In Germany Research Articles

Relationships between species richness and biomass production are context dependent in grasslands differing in land-use and seed addition

Despite evidence from grasslands experiments suggesting that plant species loss reduces biomass production, the strength of biodiversity-ecosystem functioning relationships in managed grasslands is still debated. High land-use intensity and reduced species pools are often suggested to make relationships between biodiversity and productivity less positive or even negative, but concrete evidence is still scarce. We investigated biodiversity-productivity relationships over two years in 150 managed grasslands in Germany. Specifically, we distinguished between relationships of biodiversity and biomass production in managed grasslands (1) varying in land-use intensity (e.g. of mowing, grazing and/or fertilization), (2) where land-use intensity is experimentally reduced, and (3) where additionally to land-use reductions, species pools are enlarged by seed addition. Among grasslands varying in land-use intensity, we found negative biodiversity-productivity relationships. Land-use reduction weakened these relationships, towards neutral, and sometimes, even positive relationships. Seed addition reduced species pool limitations, but this did not strengthen biodiversity-productivity relationships. Our findings indicate that land-use intensity is an important factor explaining the predominantly negative biodiversity-productivity relationships in managed grasslands. While we did not find that species pool limitations weakened biodiversity-productivity relationships, our results are based on a two-year-old experiment, possibly such effects are only visible in the long-term. Ultimately, advancing insights on biodiversity-ecosystem functioning relationships helps us to understand under which conditions agricultural production may benefit from promoting biodiversity.

Full-cycle greenhouse gas balance of a Sphagnum paludiculture site on former bog grassland in Germany

Growing Sphagnum on rewetted bogs (=Sphagnum paludiculture) is an alternative to drainage-based land use because it retains its value as productive land while mitigating greenhouse gas (GHG) emissions. However, studies on GHG exchange covering the full production system and cycle are missing. Here, we combined data of the establishment phase with newly recorded data of a 7-year old Sphagnum paludiculture site in Germany including partial Sphagnum harvest. GHGs were measured with closed chambers at all elements of the system (production fields, ditches, causeways).Over the full production cycle, the production fields were GHG sinks with −3.2 ± 4.2 t ha−1 a−1 (in CO2-eq), while ditches represented sources emitting 13.8 ± 11.5 t ha−1 a−1. New measurements on the causeway indicated that it was a stronger GHG source with 29.3 ± 9.8 t ha−1 a−1 than previously assumed from literature values. Corrected for the area share of its elements and including the partial Sphagnum harvest (in dry mass) of ~13.8 ± 0.6 t ha−1 (=average 7-year CO2 emissions of 3.3 ± 0.1 t ha−1 a−1), the site was a GHG source of 10.7 ± 4.6 t ha−1 a−1, thus reducing emissions by ~20 t ha−1 a−1 compared to the German emission factor for grassland on drained organic soils. Per ton harvested dry biomass, the paludiculture site emitted 9.9 ± 4.6 t of CO2-eq. The causeways were the major contributor to the warming, calling for reducing causeway area in Sphagnum paludicultures. Future ‘best-practice’ could realistically comprise areal shares of 80 % production fields, 5 % ditches, 15 % causeways and a full Sphagnum harvest with the uppermost 5 cm remaining on site for recovery. In this scenario the site would emit CO2-eq emissions of 4.3 ± 1.9 t ha−1 a−1 or 0.9 ± 2.1 t per ton harvested dry mass.

Mapping land-use intensity of grasslands in Germany with machine learning and Sentinel-2 time series

Information on grassland land-use intensity (LUI) is crucial for understanding trends and dynamics in biodiversity, ecosystem functioning, earth system science and environmental monitoring. LUI is a major driver for numerous environmental processes and indicators, such as primary production, nitrogen deposition and resilience to climate extremes. However, large extent, high resolution data on grassland LUI is rare. New satellite generations, such as Copernicus Sentinel-2, enable a spatially comprehensive detection of the mainly subtle changes induced by land-use intensification by their fine spatial and temporal resolution. We developed a methodology quantifying key parameters of grassland LUI such as grazing intensity, mowing frequency and fertiliser application across Germany using Convolutional Neural Networks (CNN) on Sentinel-2 satellite data with 20 m × 20 m spatial resolution. Subsequently, these land-use components were used to calculate a continuous LUI index. Predictions of LUI and its components were validated using comprehensive in situ grassland management data. A feature contribution analysis using Shapley values substantiates the applicability of the methodology by revealing a high relevance of springtime satellite observations and spectral bands related to vegetation health and structure. We achieved an overall classification accuracy of up to 66% for grazing intensity, 68% for mowing, 85% for fertilisation and an r2 of 0.82 for subsequently depicting LUI. We evaluated the methodology's robustness with a spatial 3-fold cross-validation by training and predicting on geographically distinctly separated regions. Spatial transferability was assessed by delineating the models' area of applicability. The presented methodology enables a high resolution, large extent mapping of land-use intensity of grasslands.

Detection of Grassland Mowing Events for Germany by Combining Sentinel-1 and Sentinel-2 Time Series

Grasslands cover one-third of the agricultural area in Germany and play an important economic role by providing fodder for livestock. In addition, they fulfill important ecosystem services, such as carbon storage, water purification, and the provision of habitats. These ecosystem services usually depend on the grassland management. In central Europe, grasslands are grazed and/or mown, whereby the management type and intensity vary in space and time. Spatial information on the mowing timing and frequency on larger scales are usually not available but would be required in order to assess the ecosystem services, species composition, and grassland yields. Time series of high-resolution satellite remote sensing data can be used to analyze the temporal and spatial dynamics of grasslands. Within this study, we aim to overcome the drawbacks identified by previous studies, such as optical data availability and the lack of comprehensive reference data, by testing the time series of various Sentinel-2 (S2) and Sentinal-1 (S1) parameters and combinations of them in order to detect mowing events in Germany in 2019. We developed a threshold-based algorithm by using information from a comprehensive reference dataset of heterogeneously managed grassland parcels in Germany, obtained by RGB cameras. The developed approach using the enhanced vegetation index (EVI) derived from S2 led to a successful mowing event detection in Germany (60.3% of mowing events detected, F1-Score = 0.64). However, events shortly before, during, or shortly after cloud gaps were missed and in regions with lower S2 orbit coverage fewer mowing events were detected. Therefore, S1-based backscatter, InSAR, and PolSAR features were investigated during S2 data gaps. From these, the PolSAR entropy detected mowing events most reliably. For a focus region, we tested an integrated approach by combining S2 and S1 parameters. This approach detected additional mowing events, but also led to many false positive events, resulting in a reduction in the F1-Score (from 0.65 of S2 to 0.61 of S2 + S1 for the focus region). According to our analysis, a majority of grasslands in Germany are only mown zero to two times (around 84%) and are probably additionally used for grazing. A small proportion is mown more often than four times (3%). Regions with a generally higher grassland mowing frequency are located in southern, south-eastern, and northern Germany.

Inventory and assessment of pH in cropland and grassland soils in Germany#

AbstractBackgroundSoil pH is one of the key factors affecting soil fertility. For optimal plant growth on agricultural land, suitable liming management is recommended. The basis of appropriate soil pH management in agriculture is provided by recommendations on site‐specific optimum pH ranges and lime application.AimsThis study determined the current variability of soil pH of cropland and grassland in Germany, analysed the factors associated with this variability, evaluated pH management on German agricultural land and developed a national map of current pH values in agricultural soils.MethodsThe study mainly focused on the topsoil layers of 2197 cropland sites (0–30 cm) and 812 permanent grasslands sites (0–10 cm) in the German Agricultural Soil Inventory, but reports soil pH (CaCl2) down to 50 cm. Random forest models were applied to identify environmental and management factors related to soil pH and develop a map of pH values in agricultural topsoils in Germany. The current pH status of the sampled sites was classified in accordance with German lime requirement recommendations.ResultsThe soil pH of both land‐use types showed a bimodal distribution, with peaks at pH 6.1 and 7.3 for cropland and pH 5.0 and 7.1 for grassland. Soils with pH <5 were mainly found on sandy soils in northern Germany and acidic parent material in southern Germany. Alkaline soils predominated in central and southern Germany on loess and carbonate‐rich material. The carbonate content was the major factor explaining soil pH variability, but its effect was restricted to pH values >6. Only 35.4% of the cropland sites and 23.9% of the grassland sites were within the recommended optimum pH range. The percentage of sites below the recommended pH range was greater for grassland than for cropland (52.0% and 41.0%, respectively).ConclusionsSoil pH of German agricultural land is influenced by natural factors and pH management. The first national inventory of soil pH showed that many agricultural soils exhibited pH values lower than those recommended. More conscientious pH management could help improve soil fertility and crop yield. This should be based on the regular topsoil pH analysis conducted by most farmers every five years, together with the determination of plant‐available potassium and phosphorus in soils.

Fungus-bacterium associations are widespread in fungal cultures isolated from a semi-arid natural grassland in Germany.

We report on a study that aimed at establishing a large soil-fungal culture collection spanning a wide taxonomic diversity and systematically screening the collection for bacterial associations. Fungal cultures were isolated from soil samples obtained from a natural grassland in eastern Germany and bacterial associations were assessed by PCR-amplification and sequencing of bacterial 16S rRNA. In addition, intraspecies genetic diversities of a subset of the isolated species were estimated by double-digest restriction associated DNA sequencing. A total of 688 fungal cultures, representing at least 106 fungal species from 36 different families, were obtained and even though clonal isolates were identified in almost all fungal species subjected to ddRAD-seq, relatively high genetic diversities could be observed in some of the isolated species. A total of 69% of the fungal isolates in our collection were found to be associated with bacteria and the most commonly identified bacterial genera were Pelomonas, Enterobacter and Burkholderia. Our results indicate that bacterial associations commonly occur in soil fungi, even if antibiotics are being applied during the isolation process, and provide a basis for the use of our culture collection in ecological experiments that want to acknowledge the importance of intraspecies genetic diversity.

How land-use intensity affects sexual and parthenogenetic oribatid mites in temperate forests and grasslands in Germany

Intensive land use has been shown to alter the composition and functioning of soil communities. Due to their low dispersal ability, oribatid mites are particularly vulnerable to land-use intensification and species which are not adjusted to management-related disturbances become less abundant. We investigated how different land-use parameters in forests and grasslands affect oribatid mite diversity and abundance, with a focus on: (1) species-level impacts, by classifying species as increasing (‘winners’) or decreasing (‘losers’) in abundance with higher land-use intensity, and (2) reproductive impact, by investigating whether sexual and parthenogenetic species react differently. We collected 32,542 adult oribatid mites in 60 forests and grasslands of known land-use intensity in two regions of Germany. Diversity and total abundance as well as the proportion of sexual species were higher in forests than in grasslands. Diversity declined with higher land-use intensity in forests, but increased with higher mowing and fertilization in grasslands. Depending on land-use parameter and region, abundance either declined or remained unaffected by increasing intensity. Gravidity was higher in sexual than in parthenogenetic species and sexuals had 1.6× more eggs per gravid female. Proportions of sexual species and gravid females decreased with land-use intensity in forests, but increased with mowing in grasslands. At the species level, 75% of sexuals and 87.5% of parthenogens were ‘losers’ of higher percentages of dead wood originating from management-related disturbances. Across land-use parameters and habitats, a similar proportion of sexual and parthenogenetic oribatid mite species were ‘losers’ of high land-use intensity. However, ‘winner’ species were more common among sexuals.

Long-term field experiments in Germany: classification and spatial representation

Abstract. The collective analysis of long-term field experiments (LTFEs), here defined as agricultural experiments with a minimum duration of 20 years and research in the context of sustainable soil use and yield, can be used for detecting changes in soil properties and yield such as those induced by climate change. However, information about existing LTFEs is scattered, and the research data are not easily accessible. In this study, meta-information on LTFEs in Germany is compiled and their spatial representation is analyzed. The study is conducted within the framework of the BonaRes project, which, inter alia, has established a central access point for LTFE information and research data. A total of 205 LTFEs which fit to the definition above are identified. Of these, 140 LTFEs are ongoing. The land use in 168 LTFEs is arable field crops, in 34 trials grassland, in 2 trials vegetables and in 1 trial pomiculture. Field crop LTFEs are categorized into fertilization (n=158), tillage (n=38) and crop rotation (n=32; multiple nominations possible) experiments, while all grassland experiments (n=34) deal with fertilization. The spatial representation is analyzed according to the climatic water balance of the growing season (1 May to 31 October) (CWBg), the Müncheberg Soil Quality Rating (MSQR) and clay content. The results show that, in general, the LTFEs well represent the area shares of both the CWBg and the MSQR classes. Eighty-nine percent of the arable land and 65 % of the grassland in Germany are covered by the three driest CWBg classes, hosting 89 % and 71 % of the arable and grassland LTFEs, respectively. LTFEs cover all six MSQR classes but with a bias towards the high and very high soil quality classes. LTFEs on arable land are present in all clay content classes according to the European Soil Data Centre (ESDAC) but with a bias towards the clay content class 4. Grassland LTFEs show a bias towards the clay content classes 5, 6 and 7, while well representing the other clay content classes, except clay content class 3, where grassland LTFEs are completely missing. The results confirm the very high potential of LTFE data for spatially differentiated analyses and modeling. However, reuse is restricted by the difficult access to LTFE research data. The common database is an important step in overcoming this restriction.

Intra-population terpene polymorphism of Thymus pulegioides L.: Evidence for seven chemotypes in a German limestone grassland

For Thymus pulegioides L. (Lamiaceae), occurring in almost entire Europe, about 20 different essential oil chemotypes are described in approximately 25 studies. However, only few studies mention chemotype diversity on population level, describing up to five chemotypes growing together. The aim of the study was to investigate the chemotype diversity within one T. pulegioides population of a limestone grassland in Germany. Essential oil compounds from samples of 93 thyme cushions were extracted with solid phase extraction (SPE) and analysed by GC-MS. Cluster analysis and nonmetric multi-dimensional scaling (NMDS) of the samples’ essential oil composition revealed the existence of seven different chemotypes: linalyl acetate-chemotype (56 individuals), geraniol-citral-linalyl acetate-chemotype (5), geraniol-citral-chemotype (7), thymol-chemotype (8), carvacrol-chemotype (2), linalool-chemotype (1), and β-caryophyllene-germacrene D-β-bisabolene-chemotype (14). The pattern of major monoterpenes from all chemotypes could be explained by the inhibition of specific steps in monoterpene biosynthesis. The sesquiterpene-dominant chemotype might be caused by a block in a very early step of monoterpene production or a regulatory/channeling mechanism. While the geraniol-citral-linalyl acetate-chemotype has been found for the first time, the other chemotypes have been found in other regions and the β-caryophyllene-germacrene D-β-bisabolene-type is similar to other sesquiterpene chemotypes rarely found in other areas. The large intra-population chemical polymorphism in this study raises questions about the chemotype diversity of thyme in other regions of Germany and potential correlations between essential oil composition and abiotic factors or biotic interactions.

Alkaloid Concentrations of Lolium perenne Infected with Epichloë festucae var. lolii with Different Detection Methods-A Re-Evaluation of Intoxication Risk in Germany?

Mycotoxins in agriculturally used plants can cause intoxication in animals and can lead to severe financial losses for farmers. The endophytic fungus Epichloë festucae var. lolii living symbiotically within the cool season grass species Lolium perenne can produce vertebrate and invertebrate toxic alkaloids. Hence, an exact quantitation of alkaloid concentrations is essential to determine intoxication risk for animals. Many studies use different methods to detect alkaloid concentrations, which complicates the comparability. In this study, we showed that alkaloid concentrations of individual plants exceeded toxicity thresholds on real world grasslands in Germany, but not on the population level. Alkaloid concentrations on five German grasslands with high alkaloid levels peaked in summer but were also below toxicity thresholds on population level. Furthermore, we showed that alkaloid concentrations follow the same seasonal trend, regardless of whether plant fresh or dry weight was used, in the field and in a common garden study. However, alkaloid concentrations were around three times higher when detected with dry weight. Finally, we showed that alkaloid concentrations can additionally be biased to different alkaloid detection methods. We highlight that toxicity risks should be analyzed using plant dry weight, but concentration trends of fresh weight are reliable.

Phosphorus enrichment in floodplain subsoils as a potential source of freshwater eutrophication

Despite decades of management efforts, freshwater eutrophication has not been effectively mitigated in each affected ecosystem. This might be due to insufficient knowledge of the sources of phosphorus (P) inputs into surface waters. We sampled 2 m-deep soil profiles in four floodplain areas under differently managed grassland in Germany under dry and moist conditions regarding soil moisture and precipitation. Four soil P fractions of decreasing solubility were determined. We found systematic enrichment of easily soluble P forms in the floodplain subsoils (average: from 87.5 cm depth). Water-soluble P in these “deep P stocks” was positively correlated with total phosphorus concentrations in the adjacent surface waters. Our data cautiously suggest increased P mobilization from deep P stocks under moist conditions. Drier conditions coincided with increased P retention, resulting in relatively large amounts of easily soluble P which could readily be desorbed and lost at the next stronger precipitation event. We found no effects of grassland management on deep P stock features and dynamics. Deep P stocks might be considered a new source of diffuse P losses from soils. To effectively mitigate freshwater eutrophication, best management practices need to be developed to minimize P transfer from deep P stocks.

Comparing experimental and field‐measured traits and their variability in Central European grassland species

AbstractQuestionsWhat are the relative effects of intra‐ and interspecific differences on variation in five functional traits measured in a garden pot experiment? Are species rankings based on trait means and intraspecific trait variability (ITV) stable across the garden experiment and field measurements?LocationExperimental garden and two grassland systems in Central Europe.MethodsWe measured five functional traits (plant height, leaf dry matter content [LDMC], leaf greenness, leaf thickness and specific leaf area SLA]) in 105 grassland species grown in a garden experiment subjected to fertilization, shading and waterlogging, complemented by a control. We also measured plant height, LDMC and SLA across grasslands in Germany, and used published values of the same traits from a field study in the Czech Republic. We then correlated speciesʼ trait means from different treatments in the experiment. We also compared garden‐ and field‐measured trait means and ITV in SLA, LDMC and plant height.ResultsMost variation in the experiment‐measured trait data was explained by interspecific differences, except for leaf greenness (where species explained less than 50% of the variance), and the treatments had little effect on close associations of trait means. Species rankings based on SLA and LDMC, but not plant height, were stable across garden and field measurements. Though garden and field‐measured ITV were positively associated with each other, the associations were not significant.ConclusionsOur study indicates that species can be stably ranked based on SLA and LDMC means across different datasets (experimental and field‐based). To what extent species vary in their functional traits under field conditions can be, however, less well predicted from experimentally measured ITV. Garden‐measured differences in ITV should be thus used with caution when associated with species’ performance and distribution patterns explored in the field.

Target‐oriented habitat and wildlife management: estimating forage quantity and quality of semi‐natural grasslands with Sentinel‐1 and Sentinel‐2 data

AbstractSemi‐natural grasslands represent ecosystems with high biodiversity. Their conservation depends on the removal of biomass, for example, through grazing by livestock or wildlife. For this, spatially explicit information about grassland forage quantity and quality is a prerequisite for efficient management. The recent advancements of the Sentinel satellite mission offer new possibilities to support the conservation of semi‐natural grasslands. In this study, the combined use of radar (Sentinel‐1) and multispectral (Sentinel‐2) data to predict forage quantity and quality indicators of semi‐natural grassland in Germany was investigated. Field data for organic acid detergent fibre concentration (oADF), crude protein concentration (CP), compressed sward height (CSH) and standing biomass dry weight (DM) collected between 2015 and 2017 were related to remote sensing data using the random forest regression algorithm. In total, 102 optical‐ and radar‐based predictor variables were used to derive an optimized dataset, maximizing the predictive power of the respective model. High R2 values were obtained for the grassland quality indicators oADF (R2 = 0.79, RMSE = 2.29%) and CP (R2 = 0.72, RMSE = 1.70%) using 15 and 8 predictor variables respectively. Lower R2 values were achieved for the quantity indicators CSH (R2 = 0.60, RMSE = 2.77 cm) and DM (R2 = 0.45, RMSE = 90.84 g/m²). A permutation‐based variable importance measure indicated a strong contribution of simple ratio‐based optical indices to the model performance. In particular, the ratios between the narrow near‐infrared and red‐edge region were among the most important variables. The model performance for oADF, CP and CSH was only marginally increased by adding Sentinel‐1 data. For DM, no positive effect on the model performance was observed by combining Sentinel‐1 and Sentinel‐2 data. Thus, optical Sentinel‐2 data might be sufficient to accurately predict forage quality, and to some extent also quantity indicators of semi‐natural grassland.

Diverse Swards and Mixed-Grazing of Cattle and Sheep for Improved Productivity

Phytodiversity is suggested to increase primary production of grasslands. However, whether this advantage can be converted into secondary production, i.e. the performance of grazing livestock, remains an open question. Animal production of cattle and sheep can be enhanced by mixed-grazing, but, to our knowledge, this effect has never been studied in relation to phytodiversity. Therefore, a rotational grazing experiment was conducted over five years (2007-2011) on permanent grassland in Germany using sheep and cattle in mono- or mixed-grazing of swards differing in plant species richness. Chemical herbicides against dicotyledonous plant species were used to create different sward types: species-poor grass-dominated swards in contrast to untreated ‘diverse’ control swards. We found no differences in herbage production between the sward types. However, compared to the grass-dominated sward, the diverse sward showed a larger concentration of crude protein and a smaller one of acid detergent fibre in herbage dry-matter. Live weight gains of lamb production was slightly greater on the diverse-swards (P<0.05), while calf performance was unaffected by sward type. Mixed-grazing increased daily average live weight gains of suckler cows (g cow-1 d-1) (P<0.05) as well as area-related daily live weight gains (kg ha-1 d-1) and total live weight gains (kg ha-1) during the complete grazing season (P<0.001), which displays the advantage of combining livestock species due to complementary pasture use. We suggest that mixed-grazing of cattle and sheep on phytodiverse swards is particularly appropriate to enhance ecological and agronomical traits such as livestock production of grassland to improve extensive meat production in a sustainable way. Especially lamb production profited by mixed-grazing with a +17% increase in live weight gain. Compared to the grass-dominated sward, diverse-swards resulted in an average +12%-increase of live weight gains (across grazing systems and livestock species).

Winter warming is ecologically more relevant than summer warming in a cool-temperate grassland

Climate change affects all seasons, but warming is more pronounced in winter than summer at mid- and high latitudes. Winter warming can have profound ecological effects, which are rarely compared to the effects of summer warming, and causal explanations are not well established. We compared mild aboveground infrared warming in winter to warming in summer in a semi-natural, cool-temperate grassland in Germany for four years. Aboveground plant biomass increased following winter warming (+18%) and was unaffected by summer warming. Winter warming affected the composition of the plant community more than summer warming, favoring productive species. Winter warming increased soil respiration more than summer warming. Prolonged growing seasons and changes in plant-community composition accounted for the increased aboveground biomass production. Winter warming stimulated ecological processes, despite causing frost damage to plant roots and microorganisms during an extremely cold period when warming reduced the thermal insulation provided by snow. Future warming beyond such intermittent frosts may therefore further increase the accelerating effects of winter warming on ecological processes.

Closing the N-Budget: How Simulated Groundwater-Borne Nitrate Supply Affects Plant Growth and Greenhouse Gas Emissions on Temperate Grassland

European groundwater reservoirs are frequently subject to reactive nitrogen pollution (Nr) owing to the intensive use of nitrogen (N) fertilizer and animal manure in agriculture. Besides its risk on human health, groundwater Nr loading also affects the carbon (C) and N cycle of associated ecosystems. For a temperate grassland in Germany, the long-term (12 years) annual average exports of Nr in form of harvest exceeded Nr inputs via fertilization and deposition by more than 50 kgN ha−1. We hypothesize that the resulting deficit in the N budget of the plant-soil system could be closed by Nr input via the groundwater. To test this hypothesis, the ecosystem model LandscapeDNDC was used to simulate the C and N cycle of the respective grassland under different model setups, i.e., with and without additional Nr inputs via groundwater transport. Simulated plant nitrate uptake compensated the measured N deficit for 2 of 3 plots and lead to substantial improvements regarding the match between simulated and observed plant biomass and CO2 emission. This suggests that the C and N cycle of the investigated grassland were influenced by Nr inputs via groundwater transport. We also found that inputs of nitrate-rich groundwater increased the modelled nitrous oxide (N2O) emissions, while soil water content was not affected.

Direct and indirect effects of land use on bryophytes in grasslands

Land-use intensification is the major threat for biodiversity in agricultural grasslands, and fertilization has been suggested as the most important driver. A common explanation for the decline of bryophyte diversity with higher land-use intensity is an indirect negative effect via the increase in vascular plant productivity, which reduces light levels for bryophytes. However, direct negative effects of land-use intensification may also be important. Here, we disentangle direct and vascular plant biomass mediated indirect effects of land use on bryophytes. We analyzed two complementary datasets from agricultural grasslands, an observational study across 144 differently managed grasslands in Germany and an experimental fertilization and irrigation study of eleven grasslands in the Swiss Alps. We found that bryophyte richness and cover strongly declined with land-use intensity and in particular with fertilization. However, structural equation modelling revealed that although both direct and indirect effects were important, the direct negative effect of fertilization was even stronger than the indirect effect mediated by increased plant biomass. Thus, our results challenge the widespread view that the negative effects of fertilization are mostly indirect and mediated via increased light competition with vascular plants. Our study shows that land use intensification reduces bryophyte diversity through several different mechanisms. Therefore, only low-intensity management with limited fertilizer inputs will allow the maintenance of bryophyte-rich grasslands.

Contribution of the soil seed bank to the restoration of temperate grasslands by mechanical sward disturbance

The restoration of grasslands is one of the primary targets of nature conservation. An easy tool to stimulate the growth of plant species currently absent from the aboveground vegetation but hidden in the “dark”, is to make use of the soil seed bank. Here, seeds of rare and endangered species may still be present. However, the potential contribution of soil seed banks to effective grasslands restoration still remains unclear, as some but not many valuable species built up a persistent seed bank. To evaluate the potential of the soil seed bank for grassland restoration, we installed an experiment in 73 differently managed grasslands in Germany, where the seed bank was activated by mechanical sward disturbance. We also determined the species richness, the density of viable seeds, and the functional composition of seed banks and monitored the regeneration of the aboveground vegetation over two seasons. Our results show that sward disturbance led to an activation of the soil seed banks, which, however, contributed only little to the revegetation after sward disturbance. In addition, the severe impoverishment of the soil seed bank indicated a restricted potential for the restoration of temperate grasslands. Nevertheless, the activation of the soil seed bank increased not only the richness of arable weeds but also slightly the richness of typical grassland species. We conclude that only in recently improved and strongly species‐impoverished grasslands, sward disturbance alone might be able to slightly increase plant species richness. To achieve a distinct increase in species richness, additional diaspore transfer is needed.

Miscanthus establishment and management on permanent grassland in southwest Germany

The intensification of livestock farming and use of arable forage crops has led to a decrease in the area of grassland used for animal husbandry. One potentially profitable use of this grassland is the production of biomass for bioenergy. The C4 grass miscanthus (Miscanthus spp.) is considered an important biomass resource for bioenergy production; however, its cultivation is currently limited by the shortage of suitable agricultural land. The establishment of miscanthus on permanent grassland, at low densities and without destruction of the existing vegetation, could be an interesting option to consider. In this way, the expansion of miscanthus cultivation could be combined with grassland maintenance. Conventional tilling practices in miscanthus establishment (ploughing and herbicide application) on meadows can lead to loss of biodiversity. The aim of this study was to investigate efficient no-till practices for establishment and maintenance of several miscanthus genotypes on permanent grassland in Germany, focusing on the methods to improve establishment success and biomass production potential of miscanthus-supplemented grassland. A field trial was conducted at two sites to assess the effect of genotype, grassland pre-treatment (through temporary suppression of existing vegetation to reduce initial competition) and management (harvest frequencies) on miscanthus establishment and growth in grassland stands. An additional experiment with two miscanthus genotypes was set up to assess the effect of propagation method (rhizomes or pre-grown plantlets) on miscanthus establishment on grassland. Successful miscanthus establishment was achieved with no-till planting and grassland pre-treatment. Overall, miscanthus genotypes with tall, thick shoots performed better on grassland than those with short, thin shoots. Higher establishment rates were achieved through the transplanting of rhizome-derived (pre-grown) plantlets than with direct planting of rhizomes. Cutting the grassland vegetation to a stubble height of 5cm and spraying herbicide in narrow strips before introducing miscanthus had beneficial effects on its establishment, without significant negative impact on grassland productivity. In the first three years of the study, two biomass harvests per growing season allowed a good total biomass yield from grassland to be achieved without significant impact on miscanthus growth.

A coupled hydrological-plant growth model for simulating the effect of elevated CO2 on a temperate grassland

Elevated CO2 (eCO2) reduces transpiration at the leaf level by inducing stomatal closure. However, this water saving effect might be offset at the canopy level by increased leaf area as a consequence of eCO2 fertilization. To investigate this bi-directional effect, we coupled a plant growth and a soil hydrological model. The model performance and the uncertainty in model parameters were checked using a 13year data set of a Free Air Carbon dioxide Enrichment (FACE) experiment on grassland in Germany. We found a good agreement of simulated and observed data for soil moisture and total above-ground dry biomass (TAB) under ambient CO2 (∼395ppm) and eCO2 (∼480ppm). Optima for soil and plant growth model parameters were identified, which can be used in future studies. Our study presents a robust modelling approach for the investigation of effects of eCO2 on grassland biomass and water dynamics. We show an offset of the stomatal water saving effect at the canopy level because of a significant increase in TAB (6.5%, p<0.001) leading to an increase in transpiration by +3.0±6.0mm, though insignificant (p=0.1). However, the increased water loss through transpiration was counteracted by a significant decrease in soil evaporation (−2.1±1.7mm, p<0.01) as a consequence of higher TAB. Hence, evapotranspiration was not affected by the increased eCO2 (+0.9±4.9mm, p=0.5). This in turn led to a significantly better performance of the water use efficiency by 5.2% (p<0.001). Our results indicate that mown, temperate grasslands can benefit from an increasing biomass production while maintaining water consumption at the +20% increase of eCO2 studied.