Intensive Grassland Management Research Articles

Sustainable land management enhances ecological and economic multifunctionality under ambient and future climate

The currently dominant types of land management are threatening the multifunctionality of ecosystems, which is vital for human well-being. Here, we present a novel ecological-economic assessment of how multifunctionality of agroecosystems in Central Germany depends on land-use type and climate. Our analysis includes 14 ecosystem variables in a large-scale field experiment with five different land-use types under two different climate scenarios (ambient and future climate). We consider ecological multifunctionality measures using averaging approaches with different weights, reflecting preferences of four relevant stakeholders based on adapted survey data. Additionally, we propose an economic multifunctionality measure based on the aggregate economic value of ecosystem services. Results show that intensive management and future climate decrease ecological multifunctionality for most scenarios in both grassland and cropland. Only under a weighting based on farmers’ preferences, intensively-managed grassland shows higher multifunctionality than sustainably-managed grassland. The economic multifunctionality measure is about ~1.7 to 1.9 times higher for sustainable, compared to intensive, management for both grassland and cropland. Soil biodiversity correlates positively with ecological multifunctionality and is expected to be one of its drivers. As the currently prevailing land management provides high multifunctionality for farmers, but not for society at large, we suggest to promote and economically incentivise sustainable land management that enhances both ecological and economic multifunctionality, also under future climatic conditions.

A Review and Analysis of Rangeland and Wildland Soil Health

Soil health is focused on intensively managed (IM) soils (often farmed soils), by-passing extensively managed (EM) soils (range lands, deserts, shrub lands, tundra). High economic value products are generated by IM systems. Many EM lands are of cultural, recreational, scenic, or scientific value. However, and despite the fact that they provide forage for domestic and wild animals, they are not always of high economic value. IM and EM soils are evaluated on the same health scales. The contention herein is all soils formed under soil state conditions under the absence of human interventions are inherently healthy. But a given soil has dynamic properties that determine its management as IM or EM. An EM sagebrush steppe soil may be deemed unhealthy as a result of low organic matter and short growing season. An IM grassland steppe soil is healthy as a result of high organic matter and a long growing season. The sagebrush soil, however, provides habitat for culturally important sage grouse. The grassland soil may provide, when plowed, habitat for economically important soybeans. Soil taxonomies can be used to establish inherent health of undisturbed soils. Determining a soil’s dynamic nature is a different construct. Here, four different sets of EM soils were evaluated to showcase their diversity, evaluate levels of health and display their often-unconventional dynamic characteristics. An argument is made that a soil’s health, an inherent condition, is not the same as its dynamic condition (potential to produce goods and services). Soil health changes are usually slowly driven by soil state factors but can be dramatically changed by humans. Otherwise, soil health can be viewed as a near constant ecosystem attribute. The dynamic nature of soils change according to needs placed by humans. EM soils may be healthy but lack attention since their dynamic nature is not traditional and often of low economic value. Evaluation of soil health and dynamic value on EM lands is often exacerbated by information absence. Strategies to circumvent this include sampling design, reference sites and standardized ways of EM soil health determination. A case is made that baselines of soil health can be taken from soil surveys, taxonomic names, and soil data from map units, where such information exists. Certified supplementary information is ambiguously available, but may be crucial. Outdoor living laboratories that feature inherent soil health and dynamic soil alternatives may help circumvent information voids.

Land management shapes drought responses of dominant soil microbial taxa across grasslands.

Soil microbial communities are dominated by a relatively small number of taxa that may play outsized roles in ecosystem functioning, yet little is known about their capacities to resist and recover from climate extremes such as drought, or how environmental context mediates those responses. Here, we imposed an in situ experimental drought across 30 diverse UK grassland sites with contrasting management intensities and found that: (1) the majority of dominant bacterial (85%) and fungal (89%) taxa exhibit resistant or opportunistic drought strategies, possibly contributing to their ubiquity and dominance across sites; and (2) intensive grassland management decreases the proportion of drought-sensitive and non-resilient dominant bacteria-likely via alleviation of nutrient limitation and pH-related stress under fertilisation and liming-but has the opposite impact on dominant fungi. Our results suggest a potential mechanism by which intensive management promotes bacteria over fungi under drought with implications for soil functioning.

Plant diversity enhanced nematode-based soil quality indices and changed soil nematode community structure in intensively-managed agricultural grasslands

Plant productivity, decomposition and nutrient cycling are controlled by plant-soil-biota interactions. However, it remains poorly understood how plant species diversity impacts belowground communities that modulate these processes in intensively-managed grassland systems. In managed grassland communities comprising species selected for agronomic performance, we investigated how plant species diversity affected the soil nematode community and associated ecological indices with a focus on assessing aboveground-belowground interactions. A total of 27 nematode taxa were identified from 61 experimental field plots in which plant species diversity was systematically manipulated from a pool of six plant species within three functional groups (FGs; grasses, legumes, herbs). In general, there were strong effects of plant species identity on the nematode community; interspecific interaction effects did not consistently occur, but where they did were best related to plant community evenness. The equi-proportional six-species plant community had a significantly higher nematode diversity, maturity index (MI), structure index (SI) and proportion of sensitive taxa (omnivore and predators) but a lower enrichment index (EI) than the individual monocultures. The two legumes (Trifolium pratense and Trifolium repens) had the highest EI but lowest abundance of fungivores and channel index, indicating a bacterial-dominated decomposition pathway. Moreover, the community structure of nematodes in the equi-proportional six-species community was significantly different from that in the monocultures. This change in community structure was associated with factors highly correlated with plant diversity, including higher aboveground biomass yield and total nitrogen in harvested biomass as well as lower biomass of weed species. Overall, our results show that multi-species forage sward mixtures that include grasses, legumes, and herbs can have a positive effect on the soil nematode community and nematode-based soil quality indices. This is of practical relevance for farmers and for EU agricultural policy targeted at sustainability, soil health and farming for biodiversity benefits.

Intensive grassland management disrupts below-ground multi-trophic resource transfer in response to drought

Modification of soil food webs by land management may alter the response of ecosystem processes to climate extremes, but empirical support is limited and the mechanisms involved remain unclear. Here we quantify how grassland management modifies the transfer of recent photosynthates and soil nitrogen through plants and soil food webs during a post-drought period in a controlled field experiment, using in situ 13C and 15N pulse-labelling in intensively and extensively managed fields. We show that intensive management decrease plant carbon (C) capture and its transfer through components of food webs and soil respiration compared to extensive management. We observe a legacy effect of drought on C transfer pathways mainly in intensively managed grasslands, by increasing plant C assimilation and 13C released as soil CO2 efflux but decreasing its transfer to roots, bacteria and Collembola. Our work provides insight into the interactive effects of grassland management and drought on C transfer pathways, and highlights that capture and rapid transfer of photosynthates through multi-trophic networks are key for maintaining grassland resistance to drought.

A multimodality test outperforms three machine learning classifiers for identifying and mapping paddocks using time series satellite imagery

Rotational grazing in paddocks is a strong indicator of intensive grassland management. Uncertainty in the extent of grassland management intensity is a reported source of uncertainty in greenhouse gas budgeting. This article outlines a method of detecting paddock locations in Sentinel 2 satellite imagery using a statistical multimodality test. The test was compared to three machine learning algorithms (support vector machine, random forest and extreme gradient boosting). Photographic records of the Eurostat 2018 LUCAS survey were used as ground truth data to confirm the presence or absence of paddocks. The multimodality test achieved an overall accuracy of 88.4% versus the best machine learning accuracy of 82.4%. The test was also used to map paddock occurrence at a regional scale in the Republic of Ireland. Overall map accuracy was 85.7% versus validation data. The test can be applied in temperate grasslands with pre-mapped field boundaries where rotational grazing is practiced.

Population dynamics of the Corncrake Crex crex in Slovenia in the 1992–2021 period

Abstract The first national Corncrake Crex crex survey in Slovenia was performed in 1992/93, followed by further five in 1999, 2004, 2010, 2015 and 2020. In 2004, annual monitoring of eight most important Corncrake Natura 2000 sites (SPAs) began. Both datasets showed a moderate population decline since 1992. After Slovenia’s accession to the EU in 2004, Corncrake population steeply declined at SPA Breginjski Stol and moderately declined at SPA Dobrava - Jovsi due to scrub encroachment, whereas moderate decline at SPA Ljubljansko barje can be attributed mostly to intensive grassland management and the conversion of grasslands to arable land, resulting in nest and habitat destruction. In 2020, the number of calling males in Slovenia was smaller by 55 % compared to 1999, when the highest number ever was recorded (683). The highest average number of Corncrakes in the 1992–2021 period was counted at SPA Ljubljansko barje (139 calling males/year), whereas the smallest number was recorded at SPA Snežnik - Pivka (8 calling males/year). A comparison of target values for Corncrake population size on individual SPAs from the national Natura 2000 management programme for the 2015–2020 period with counted population sizes showed that, with the exception of SPA Lake Cerknica, all SPAs are falling behind the target values by 32–90%, depending on the site. Likewise, the majority of sites are far from reaching target values for the enrolment of agri-environmental measure VTR (first cut after 1 Aug). The article also discusses the weaknesses of current VTR, its reform in 2021, as well as other potential measures and financial sources for Corncrake conservation.

The costs of diversity: higher prices for more diverse grassland seed mixtures

Globally, we face a dramatic biodiversity loss in agricultural systems as well as severe ecosystem degradation. In grasslands, higher biodiversity in terms of plant diversity was shown to increase the diversity of higher trophic levels and provide benefits for farmers such as higher and more stable yields. However, we lack a systematic overview of costs for more diverse seed mixtures, which are an essential tool in maintaining and increasing plant diversity in grasslands. We here investigated the prices and characteristics of 262 commercially available seed mixtures from six German or Swiss online shops and quantified the relationships between seed mixture prices and plant diversity. The most frequent seed mixtures contained 1–10 species and were designed for rather intensive grassland management. On the contrary, a smaller set of seed mixtures with particularly high plant diversity (>30 species), usually of native ecotypes, were offered for restoration purposes. More diverse seed mixtures were also more expensive. For example, a seed mixture with 10 or 30 species was on average +63% or +387% more expensive, respectively, than a product containing only one species. The relationship between plant diversity and seed mixture prices per ha was related to other seed mixture characteristics, of which plant provenance (i.e. native ecotypes vs. cultivars) was particularly important for the price. Seed mixtures containing only native ecotypes had considerably higher prices per ha (⩾+75%) than those including cultivars. In conclusion, increasing biodiversity in grasslands can be costly. These costs need to be considered when making recommendations to farmers and other stakeholders. Measures to reduce such costs for maintaining and/or increasing plant diversity could promote establishment of grasslands with higher plant diversity, facilitate the restoration of semi-natural grasslands, and contribute to solving the biodiversity crisis in agroecosystems.

Grassland soil organic carbon stocks along management intensity and warming gradients

AbstractGrasslands are a major terrestrial ecosystem type and store large amounts of soil organic carbon (SOC) per unit area. Quantitative and mechanistic knowledge on the effects of management on SOC stocks in grasslands is limited. Also, climate change can be seen as an indirect anthropogenic threat to SOC stocks, with warming effects on grassland SOC being currently understudied. Here, several studies investigating the effects of management and warming on SOC stocks are summarised, with a central to northern European focus. SOC sequestration increased with management intensity, i.e. cutting frequency and mineral fertilisation, even without external C inputs. This was partly explicable by increased productivity in more intensively managed grasslands. In addition, the availability of nutrients was found to foster microbial anabolism, leading to a more efficient build‐up of SOC in fertilised as compared to unfertilised soils. Interestingly, the addition of 1 kg nitrogen as NPK fertiliser consistently led to approximately 1 kg of additional SOC. Sequestration of SOC might thus compensate for a major part of the increased greenhouse gas emissions associated with highly intensive grassland management. Including perennial grasses in agricultural crop rotations is multi‐beneficial and proved to be a very efficient measure to increase SOC stocks. At the same time, soil warming depleted SOC, both in natural subarctic as well as in managed temperate grasslands. Climate change can thus be expected to counterbalance efforts of SOC build‐up to some extent. Future research should focus on the interactive effects of climate change and management, which will be important for future management decisions.

Detection of Colchicum autumnale in drone images, using a machine-learning approach

Colchicum autumnale are toxic autumn-blooming flowering plants, which often grow on extensive meadows and pastures. Thus, they pose a threat to farm animals especially in hay and silage. Intensive grassland management or the use of herbicides could reduce these weeds but environment protection requirements often prohibit these measures. For this reason, a non-chemical site- or plant-specific weed control is sought, which aims only at a small area around the C. autumnale and with low impact on the surrounding flora and fauna. For this purpose, however, the exact locations of the plants must be known. In the present paper, a procedure to locate blooming C. autumnale in high-resolution drone images in the visible light range is presented. This approach relies on convolutional neural networks to detect the flower positions. The training data, which is based on hand-labeled images, is further enhanced through image augmentation. The quality of the detection was evaluated in particular for grassland sites which were not included in the training to get an estimate for how well the detector works on previously unseen sites. In this case, 88.6% of the flowers in the test dataset were detected, which makes it suitable, e.g., for applications where the training is performed by the manufacturer of an automatic treatment tool and where the practitioners apply it to their previously unseen grassland sites.

Grassland management effects on earthworm communities under ambient and future climatic conditions

AbstractThe impacts of climate change on biodiversity can be modulated by other changing environmental conditions (e.g. induced by land‐use change). The potential interactive effects of climate change and land use have rarely been studied for soil organisms. To test the effects of changing climatic conditions and land use on soil invertebrates, we examined earthworm communities across different seasons in different grassland‐use types (intensively managed grassland, extensively managed meadow and extensively managed sheep pasture). We predicted that the strength of climate change effects would vary with season and land use. Overall, extracted earthworm populations showed the strongest variations in response to the season, indicating major differences in activity patterns and extraction efficiency, whereas climate change and different grassland‐use types had fewer and weaker effects. Future climate, characterized by slightly higher precipitation in spring and autumn but a strong reduction during the summer, had positive effects on the abundance of extracted adult earthworms in spring but then reduced the abundance of active earthworms across the remaining seasons. In contrast, the total biomass of juveniles tended to be consistently lower under future climate conditions. Earthworm species responded differently to the climate change and different grassland management types, and these species‐specific responses further varied strongly across seasons. Intensive grassland management had negative effects, due to plant community composition, whereas sheep grazing favoured earthworm populations, due to dung deposition. There were only limited interactive effects between climate and land use, which thus did not support our main hypothesis. Nevertheless, these results highlight the complex and context‐dependent responses of earthworm communities and activity patterns to climate change, with potential consequences for long‐term population dynamics and crucial ecosystem functions.Highlights We explored earthworm communities in response to climate change, different grassland‐use types and seasons Climate had species‐specific effects on active earthworms, but few interactions with land‐use type Intensive grassland management decreased, but sheep grazing favoured, active earthworm populations Strong seasonal variations in earthworm activity periods will be modulated by climate change

Applying a mechanistic fermentation and digestion model for dairy cows with emission and nutrient cycling inventory and accounting methodology

In mitigating greenhouse gas (GHG) emissions and reducing the carbon footprint of dairy milk, the use of generic estimates in inventory and accounting methodology at farm level largely ignores variation of on-farm GHG emissions. The present study aimed to implement results of an extant dynamic, mechanistic Tier 3 model for enteric methane (CH4) (applied in Dutch national GHG inventory) in order to capture variation in enteric CH4 emission, and in faecal N and organic matter (OM) digestibility, ultimately required to predict manure CH4 and ammonia emission. Tier 3 model predictions were translated into calculation rules that could easily be implemented in an annual nutrient cycling assessment tool including GHG emissions, which is currently used by Dutch dairy farmers. Calculations focussed on (1) enteric CH4 emission, (2) apparent faecal OM digestibility and (3) apparent faecal N digestibility. Enteric CH4 was expressed in CH4 yield indicated with the term emission factor (EF; g CH4/kg DM) for individual dietary components and feedstuffs. Factors investigated to cover predicted variation in EF value included the level of feed intake, the type of roughage fed (proportions of grass silage and maize silage) and the quality of roughage fed. A minimum number of three classes of roughage type (i.e. 0. 40% and 80% maize silage in roughage DM) appeared necessary to obtain correspondence between interpolated EF values from EF lists and Tier 3 model predictions. A linear decline in EF value with 1% per kg increase in DM intake is adopted based on model simulations. The quality of roughage was represented by the effect of maturity of harvested grass or of the whole plant maize at cutting, based on a survey of modelling as well as experimental work. Also, predictions were assembled for apparent faecal OM digestibility which could be used in national inventory and in farm accounting. Apparent faecal N digestibility (as a major determinant of predicted urinary N excretion) was predicted, to support current Dutch national ammonia emission inventory and to correct the level of N digestibility in farm accounting. Compared to generic values or values retrieved from the Dutch feeding tables, predicted OM and N digestibility and enteric CH4 are better rooted in physiological principles and better reflect observed variation under experimental conditions. The present results apply for conditions with fairly intensive grassland management in temperate regions.

Improving phosphorus sustainability in intensively managed grasslands: The potential role of arbuscular mycorrhizal fungi

Long-term nutrient fertilization of grassland soils greatly increases plant yields but also profoundly alters ecosystem phosphorus (P) dynamics. Here, we addressed how long-term P fertilization may affect ecosystem P budget, P use efficiency (PUE) and the abundance of arbuscular mycorrhizal fungi (AMF), which play a key role in the acquisition of P by plants.We found that 47 years of organic P applications increased soil P availability and total soil P stocks up to 1600% and 400%, respectively, compared to unfertilized-control soils. Grassland soils could retain up to 62% and 48% of P applied since 1970 in organic and inorganic forms, respectively.Nutrient treatments significantly affected rates of AMF root colonization (%), which were higher in control and NPK-fertilized plots when compared to soils receiving increasing applications of organic P. Plant PUE increased with greater AMF root colonization, which remained high (i.e. 50-to-75%) even after ~50 years of continuous ‘normal’ rates of agronomic P inputs (~30 kg P ha−1 year−1). AMF abundance, however, decreased under higher P applications and we found a negative relationship between soil P availability or soil P stocks and rates of AMF root colonization. Our study demonstrates that (1) AMF root colonization is still high in soils, which have received consistent but moderate P inputs for over four decades, and (2) moderate rates of P fertilization are related to a more conservative P ecosystem budget whereby the amount of P retained in soils and up-taken by plants on an annual basis is higher than the amount of P added through fertilization. This is possible only if extra P is ‘mined’ from the soil P ‘bank’ and made available to plant uptake. We suggest that AMF could play a significant role in intensively-managed grasslands contributing to increase P sustainability by reducing the need for extra P fertilizer.

Evidence of low response of soil carbon stocks to grassland intensification

Grasslands cover more than a third of the European agricultural area and are often intensively managed to support the livestock-farming sector. Despite grassland intensification can greatly influence soil carbon (C) cycling, changes in soil C stocks both across years and at increasing soil depths remain difficult to quantify simultaneously. Here we measured spatial and temporal changes in soil C stocks to assess C stocks’ response to intensive grassland management. We measured soil C stocks (a) in a long-term nutrient fertilization experiment on permanent grassland (established in 1970), and (b) in 126 grassland fields distributed across 11 lowland farms in Northern Ireland (UK), which are associated with different frequencies of soil tillage. Using 45 years of data from the plot-scale grassland experiment we found evidence that significant changes in soil C stocks mainly occurred in the soil top 20 cm (not in deeper soils) and only between ‘extreme’ nutrient treatments (i.e. unfertilized vs. highly fertilized soils). Soil physical fractionation, radiocarbon and stable nitrogen isotope analyses all suggest that new C has accumulated in these soils but perhaps not fast enough to affect C stocks in deeper soil layers. Results at the field-scale from intensively managed grasslands show how the frequency of soil tillage neither affected soil C stocks between 0–20, 20–40 or 40–60 cm depth layers nor the C pool of different soil physical fractions at increasing soil depths. Our findings demonstrate how the response of soil C stocks to grassland intensification (i.e. C stocks response to different rates of nutrient fertilization or frequency of soil tillage) can be very slow both in time and space under cool and humid climate conditions. We suggest how the persistence of these soil C stocks under intensive grassland management offers the unique opportunity to improve nutrient use efficiency and cycling thus promoting the delivery of multiple ecosystem processes.

The impact of cattle drinking points on aquatic macroinvertebrates in streams in south-east Ireland

Abstract Measures that prevent cattle access to watercourses are commonly implemented through agri-environment schemes, in an effort to address the objectives of the Water Framework Directive. Despite the widespread implementation, few studies have assessed the impact of cattle access to streams on aquatic macroinvertebrates. This study assessed the local-scale impact of cattle drinking points on water quality parameters (i.e. macroinvertebrate and water chemistry metrics) on 39 intensively-managed grassland farms in the south-east of Ireland. The results indicate that sites that were more than or equal to good quality upstream of cattle drinking points, were more susceptible to cattle access impacts than sites where upstream water quality was less than good. The European Court of Auditors (2011) recommended that there should be a higher rate of EU contribution for measures with higher environmental potential, in this instance, for cattle exclusion measures targeted to sites where background quality is more than or equal to good. Appropriate efforts should thus be made to incentivise farmers in good to high status sites to adopt cattle exclusion measures.

Earthworm activity and availability for meadow birds is restricted in intensively managed grasslands

Abstract Earthworms are an important prey for the endangered meadow birds of northwest Europe. Although intensive grassland management with high manure inputs generally promotes earthworm abundance, it may reduce the effective food availability for meadow birds through desiccation of the topsoil, which causes earthworms to remain deeper in the soil. We studied the response of Red Worm Lumbricus rubellus, a detritivore, and Grey Worm Aporrectodea caliginosa, a geophage, to soil moisture profiles in the field and under experimental conditions. Surfacing earthworms were counted weekly in eight intensively managed grasslands (treated with high inputs of slurry by slit injection) with variable groundwater tables in the Netherlands. At each count, soil penetration resistance, soil moisture tension and groundwater level were measured, while air temperature and humidity were obtained from a nearby weather station. The response to variation in the vertical distribution of soil moisture was also experimentally studied in the two earthworm species. In the field, earthworms’ surfacing activity at night was negatively associated with soil moisture tension and positively by relative air humidity. Surprisingly, there was no effect of groundwater level; an important management variable in meadow bird conservation. Under experimental conditions, both L. rubellus and A. caliginosa moved to deeper soil layers (>20 cm) in drier soil moisture treatments, avoiding the upper layer when moisture levels dropped below 30%. Synthesis and applications. We propose that in intensively managed grasslands with slurry application, topsoil desiccation reduces earthworm availability for meadow birds. This can be counteracted by keeping soil moisture tensions of the top soil above −15 kPa. We suggest that the late raising of groundwater tables in spring and the disturbance of the soil by slit injection of slurry increase topsoil desiccation. This decreases earthworm availability when it matters most for breeding meadow birds. Meadow bird conservation will benefit from revised manure application strategies that promote earthworm activity near or at the soil surface.

Sheep urine patch N2O emissions are lower from extensively-managed than intensively-managed grasslands

A large number of sheep graze extensively managed grasslands, including upland and hill areas. Excretal deposition of nitrogen (N) to upland soil is a potentially large source of the powerful greenhouse gas (GHG), nitrous oxide (N2O), however, few studies have assessed urine-patch N2O emissions from upland areas. Current default excretal N2O emission factors (EFs) are based on intensively managed lowland systems, with cattle excreta as the N source. We hypothesised that N2O emissions could differ substantially from those of lowland systems, due to differences in soil type, climate, topography, pasture composition and management factors along altitudinal and productivity gradients. We investigated N2O emission factors across two seasons (spring and autumn), for an extensive semi-improved, temperate grassland using IPCC-compliant and representative sheep urine patches (in terms of urine chemical composition, urine patch size and N loading rates). An automated GHG monitoring system provided high-frequency GHG data from sheep urine patches (756 and 1112 kg N ha−1 applied in spring and autumn, respectively), reference artificial sheep urine patches (1066 and 1004 kg N ha−1 applied in spring and autumn, respectively) and control treatments. In spring, urine patch N2O emission factors were −0.02 ± 0.04 (artificial sheep urine) and 0.03 ± 0.09% (real sheep urine) of the applied N; in autumn emission factors were 0.02 ± 0.03 (artificial sheep urine) and 0.08 ± 0.04% (real sheep urine) of the applied N. These values are much lower than default inventory values (1% of applied N) for excreta deposited by grazing livestock. There was a greater pasture foliar N content following urine application in spring as opposed to autumn, and a significantly longer residence time of extractable mineral N in autumn. Our findings demonstrate the importance of generating country-specific N2O EFs based on altitude/productivity gradients of livestock production, with implications for national inventories and the accuracy of sustainability metrics of lamb produced in the UK uplands.

Effects of mowing, grazing and fertilization on soil seed banks in temperate grasslands in Central Europe

Soil seed banks support the recovery of plant species and communities after disturbances. Against the background of increasing disturbance frequencies due to current changes in climate and land use, the importance of seed banks to maintain ecosystem functioning of grasslands is likely to increase. This makes seed bank ecology a highly relevant topic of studies on ecosystem functioning. One of the main drivers of seed bank composition and density in grasslands is the current management. Although highly intensive grassland management can affect soil seed banks negatively, it is still unclear which component of management – fertilization, mowing or grazing – is the most influential. We studied soil seed banks of 73 mesic grasslands, which were arranged along a gradient of land-use intensity, by two seasonally differing surveys. Grasslands generally exhibited rather poor seed banks with low numbers of species and seedlings. Both were even lower in spring compared to autumn sampling. Grassland management turned out to affect soil seed banks in a complex way, via direct and indirect paths. While intensive mowing and fertilization decreased species richness and seedling density, grazing intensity increased species richness in the seed bank. Thus, land-use intensity, an index calculated as a sum of all three components, had highly ambivalent effects on seed banks. We conclude that the positive effect of grazing on soil seed banks makes pastures more resilient towards mechanic disturbances as compared to meadows.

Bacterial communities in soil become sensitive to drought under intensive grazing

Increasing climatic and anthropogenic pressures on soil ecosystems are expected to create a global patchwork of disturbance scenarios. Some regions will be strongly impacted by climate change, others by agricultural intensification, and others by both. Soil microbial communities are integral components of terrestrial ecosystems, but their responses to multiple perturbations are poorly understood. Here, we exposed soils from sustainably- or intensively-managed grasslands in an agro-silvo-pastoral oak woodland to month-long intensified drought and flood simulation treatments in a controlled mesocosm setting. We monitored the response of the bacterial communities at the end of one month as well as during the following month of recovery. The communities in sustainably-managed plots under all precipitation regimes were richer and more diverse than those in intensively-managed plots, and contained a lower proportion of rapidly-growing taxa. Soils from both land managements exhibited changes in bacterial community composition in response to flooding, but only intensively-managed soils were affected by drought. The ecologies of bacteria favored by both drought and flood point to both opportunism and stress tolerance as key traits shaping the community following disturbance. Finally, the response of several taxa (i.e. Chloracidobacteria RB41, Janthinobacterium sp.) to precipitation depended on land management, suggesting that the community itself affected individual disturbance responses. Our findings provide an in-depth view of the complexity of soil bacterial community responses to climatic and anthropogenic pressures in time, and highlight the potential of these stressors to have multiplicative effects on the soil biota.

Biodiversity effects on ecosystem functioning in a 15-year grassland experiment: Patterns, mechanisms, and open questions

Biodiversity effects on ecosystem functioning in a 15-year grassland experiment: Patterns, mechanisms, and open questions