For the restoration of biodiversity in agricultural grasslands, it is essential to understand how management acts as an ecological filter on the resident species. Mowing constitutes such a filter: ...only species that possess functional traits enabling them to withstand its consequences can persist in the community. We investigated how the timing of mowing modulates this filtering effect for insects. We predicted that two traits drive species responses. Species with larval development within the meadow vegetation will suffer more from mowing than species whose larvae develop in or on the ground, or outside the meadows, while species with a later phenology should benefit from later mowing. We conducted a five-year experiment, replicated at 12 sites across the Swiss lowlands, applying three different mowing regimes to lowintensity hay meadows: (1) first cut of the year not earlier than 15 June (control regime); (2) the first cut delayed until 15 July; and (3) leaving an uncut grass refuge on 10–20% of the meadow area (after earliest first cut on 15 June). Before the first cut in years 4 or 5, we sampled larvae of Lepidoptera and sawflies, and adults of moths, parasitoid wasps, wild bees, hoverflies, ground beetles, and rove beetles. Overall, before the first cut of the year, abundances of species with vegetation-dwelling larvae were higher in meadows with delayed mowing or an uncut grass refuge, with some taxon-specific variation. In contrast, species whose larval development is independent of the meadow vegetation showed no differences in abundance between mowing regimes. Species richness did not differ among regimes. For species with vegetation-dwelling larvae, a fourth-corner analysis showed an association between early phenology and the control regime. No associations were found for the other functional groups. Our results show that slight modifications of mowing regimes, easily implementable in agri-environmental policy schemes, can boost invertebrate abundance, potentially benefitting insectivorous vertebrates.
ABSTRACT
Burning has commonly been used to increase forage production and nutrients cycling in grasslands. However, its long‐term effects on soil organic carbon (SOC) and nitrogen (N) pools within ...the aggregates and the relation between aggregates‐associated SOC and soil CO2 emissions need further appraisal. This study evaluated the effects of 64 years of annual burning on SOC and N dynamics compared to annual mowing and undisturbed treatments in a grassland experiment established in 1950. Soils were sampled from four depths representing the upper 30 cm layer and fractionated into macroaggregates, microaggregates and silt + clay fractions. The macroaggregates were further fractionated into three occluded fractions. The SOC in the bulk soil and aggregates were correlated to soil CO2 effluxes measured under field conditions. Compared to the undisturbed treatment, annual burning decreased aggregates stability, SOC and N in the upper 30 cm layer by 8%, 5% and 12%, respectively. Grassland mowing induced greater aggregates stability than burning only in the upper 5 cm. Burning also decreased SOC in the large macroaggregates (e.g., 0–5 cm) compared to mowing and the undisturbed grasslands but proportionally increased the microaggregates and their associated SOC. Soil N associated with aggregates decreased largely following grassland burning, for example, by 8.8‐fold in the microaggregates within the large macroaggregates at 20–30 cm compared to the undisturbed grassland. Burning also increased soil CO2 emissions by 33 and 16% compared to undisturbed and mowing, respectively. The combustion of fresh C and soil organic matter by fire is likely responsible for the low soil aggregation, high SOC and N losses under burned grassland. These results suggested a direct link between grass burning and SOC losses, a key component for escalating climate change severity. Therefore, less frequent burning or a rotation of burning and mowing should be investigated for sustainable grasslands management.
A 64‐years of annual burning caused significant loss of soil organic carbon and nitrogen content compared to annual mowing and undisturbed grasslands. These results were mainly explained by the adverse effect of fire on soil aggregates stability. In addition to soil carbon and nitrogen losses, fire also produces more greenhouse gases, i.e., COx, NxO and CH4, during biomass burning suggesting a significant impact on global warming. Hence, grassland burning could increase grass quality and prevent bush encroachments; integrating other management such as mowing, rest, or controlled grazing with burning could be investigated for grassland and environmental conservations.
Mowing is a common practice in grassland management. It removes the majority of current year's aboveground plant biomass and thus substantial amounts of nutrients residing in plant tissues. The ...responses of plant aboveground biomass and nutrients to mowing stubble height is of great importance for developing sustainable mowing regimes, however, they are not well understood. We studied the effects of 4-year annual mowing at different height on plant aboveground biomass, plant N, P and N:P ratio, and soil nutrients in an Inner Mongolian steppe. Six stubble heights were set respectively at 14 cm (M14), 12 cm (M12), 10 cm (M10), 8 cm (M8), 6 cm (M6) and less than 0.3 cm (M0) height to ground surface. A no-mowing treatment (CK) was also included, making seven treatments. The results show that plant biomass production increased under light mowing (stubble height > 12 cm) but decreased under heavy mowing (stubble height < 6 cm), and the optimal stubble height for sustainable mowing was 6–12 cm. Plant N and P concentrations increased with mowing intensity (i.e. with the decrease of mowing stubble height). Plant N:P ratio decreased for some species, but no a directional change was detected in plant N:P ratio at the community level, nor in soil organic carbon and nutrient concentrations across the stubble height treatments. Our results indicate that plant biomass and N & P respond quickly to mowing height, whereas the response of soil chemical properties is insignificant over the 4-year period. To elucidate variation of species compensatory growth along mowing intensity gradient and the mutual feedback mechanism of soil-plant in mowing grassland, long-term study at permanent sites with changing stubble heights should be strengthened.
•Light mowing increase but heavy mowing decrease plant aboveground biomass.•Plant N and P contents increased significantly with mowing intensity.•Plant N:P ratio respond differently to mowing at species and community levels.•Short-term mowing had no significant effect on soil chemical properties.
The diversity and structure of plant and soil microbial communities are influenced by temporal variability in environmental conditions (e.g., precipitation); however, it is unclear whether the ...responses of these biotic communities to land use practices (e.g., N fertilization and mowing) also vary over time. Here we investigated how harvesting hay by mowing and applications of N fertilization at different rates (0, 2.5, 5, 10, 20, and 40 g N m−2 yr−1) affected plant, bacterial, and fungal communities by exploring data collected from a field experiment in a semiarid grassland in northern China over two consecutive years of 2017 and 2018. The cumulative precipitation during the growing season differed between the two studied years. The sampling year had more effect on the structure of the plant and soil microbial community than N fertilization and mowing, suggesting that the effects of land use practices varied by year, and were difficult to predict over time. The diversity of bacteria and fungi showed a different response to N fertilization and mowing between the two years. For example, in the wet year, the fungal diversity was up to 11% lower in soil that had been treated using the highest N fertilizer application than in untreated soil, but showed little variation in the dry year. The bacterial diversity was higher for all N application rates in the mown than the unmown land during the wet year, but no difference was observed during the dry year. There were more opportunistic and sensitive taxa for the two years (over 36.9% of top 10% relative abundance of bacterial and fungal taxa) than for N fertilization and mowing (below 33.0% of top 10% relative abundance of bacterial and fungal taxa). The relationships between plant and soil microbial communities differed between the two years, and were much stronger in the dry year than the wet year. We conclude that N fertilization and mowing had varying effects on plant and soil microbial communities in the study area over the two-year period. Our results also suggest that precipitation is the main control on land use-related changes in plant and soil microbial communities in semiarid ecosystems.
•Bacteria and fungi responded differently to land use drivers in two years.•N fertilization only reduced the diversity of bacteria and fungi in the wet year.•Individual microbial taxa were more responsive to year than to land use drivers.•Rainfall changes might explain the inconsistent biotic responses to land use drivers.•The linkage between plant and soil microbes was tighter in the dry than wet year.
Although 30% of the European surface area is covered with grasslands, little is known about the effect of their management on soil quality and biogeochemical cycling. Here, we analysed soil from an ...experimental site in Western France, which had been under either grazing or mowing regime for 13 years. We aimed to assess the effect of the two management practices on the biogeochemical functioning of the soil system. To this end we compared soil organic matter (SOM) composition and microbial properties at two depths. We analysed for elemental, lignin and non-cellulosic polysaccharide content and composition, microbial biomass, soil microbial respiration and enzyme activities. Our results showed higher soil organic carbon (SOC) and nitrogen contents in the surface soil under grazing as compared to mowing. Soil biogeochemical properties also differed between grazing and mowing treatments. In particular, soil under grazing showed lower lignin and higher microbial biomass. Despite the similar non-cellulosic polysaccharide content under both treatments, microbial community under mowing was characterised by higher enzyme production per microbial biomass, leading to more degraded SOM in the mowing system as compared to grazing. We conclude that grazing and mowing regimes impact differently biogeochemical soil functioning. Higher and more diverse carbon input under grazing compared to mowing may lead to enhanced substrate availability and thus more efficient microbial functioning, which could favour SOC sequestration through formation of microbial products.
•Grazing and mowing have contrasting effects on soil biogeochemical properties.•Grazing promoted more efficient microbial functioning.•Mowing leads to more degraded lignin than grazing.•Only microbial properties were sensitive to treatment effects in subsurface soil.
Road verges provide habitats that have considerable potential as a tool for pollinator conservation, especially given the significant area of land that they collectively cover. Growing societal ...interest in managing road verges for pollinators suggests an immediate need for evidence-based management guidance.
We used a formal, global literature review to assess evidence for the benefits of road verges for pollinators (as habitats and corridors), the potential negative impacts of roads on pollinators (vehicle-pollinator collisions, pollution, barriers to movement) and how to enhance road verges for pollinators through management.
We identified, reviewed and synthesised 140 relevant studies. Overall, the literature review demonstrated that: (i) road verges are often hotspots of flowers and pollinators (well established), (ii) traffic and road pollution can cause mortality and other negative impacts on pollinators (well established), but available evidence suggests that the benefits of road verges to pollinators far outweigh the costs (established but incomplete), and (iii) road verges can be enhanced for pollinators through strategic management (well established). Future research should address the lack of holistic and large-scale understanding of the net effects of road verges on pollinators.
We provide management recommendations for enhancing both individual road verges for pollinators (e.g. optimised mowing regimes) and entire road networks (e.g. prioritising enhancement of verges with the greatest capacity to benefit pollinators), and highlight three of the most strongly supported recommendations: (i) creating high quality habitats on new and existing road verges, (ii) reducing mowing frequency to 0–2 cuts/year and (iii) reducing impacts of street lighting.
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•Road verges have considerable potential to be used for pollinator conservation.•Verges can be hotspots of flowers and pollinators in managed landscapes.•Traffic and road pollution can cause mortality and other impacts on pollinators.•Evidence suggests the benefits of road verges to pollinators outweigh the costs.•Road verges can be enhanced for pollinators through strategic management.
Micro-scale management of cultural landscapes with species-rich grasslands requires the operation of extensive, traditional land-use systems. These social-ecological systems are under increasing ...pressure of interacting drivers that impact on farmers' individual decisions and force them to make trade-offs. We aimed to reveal the local understanding of driver interactions and related trade-offs focusing on a key element of a traditional social-ecological system. We studied the time of hay-mowing using participatory observation (105 field days), semi-structured interviews (n = 85), and focus group discussions (n = 2), analyzing the interacting IPBES-defined drivers that influence the choice of the time of mowing and related trade-offs in a small-scale community in a mountainous landscape (Gyimes, Transylvania, Romania) from the 1950s to the present. Local farmers perceived a number of direct and indirect drivers, as ecological, socio-cultural, economic, and political changes affected the optimal and actual time of mowing and increased the number of trade-offs. The most important factors were (1) the quality of the hay; (2) long-term yield stability by ensuring seed ripening, and (3) qualifying for financial support from agri-environment-climate schemes. Direct drivers influenced the phenology of vegetation and thus the time of mowing, while indirect social, cultural, and political drivers only impacted on the latter. The complexity of driver and trade-off interactions increased through time making adaptation more difficult. While farmers were navigating through the increased complexity, an informal social institution that previously optimized the work forces of farms gradually disappeared. The cumulative effects of drivers and trade-offs decreased the economic and social viability of the system. Our results suggest that the local community's adaptive capacity has been drastically weakened. We argue that more flexible and adaptive regulations are needed to assure the continuity and ongoing adaptation of this and other Eastern-Central-European, centuries-old but still existing traditional management systems, which created and maintain high nature-value cultural landscapes.
•Grassland and farmland birds have experienced severe declines in recent decades.•Drivers are habitat loss, mowing/harvesting, disturbance, pesticides, food supply.•Pesticides and mowing/harvesting ...have the most consistently negative effects.
Globally, agriculture has intensified during the past 50 years due to increased mechanization, changes in the timing of farming operations, grassland conversion to cropland, and increased agrochemical inputs. Birds associated with farmlands and grasslands in North America have experienced severe declines over the last several decades, prompting the need for a comprehensive review of the drivers, mechanisms and magnitude of effects on bird populations. Here we evaluated changes in North American farmland bird populations over time and conducted a systematic review and analysis of the published literature to identify the major causes. Based on North American Breeding Bird Survey data, populations of 57 of 77 (74%) farmland-associated species decreased from 1966 to 2013. Multiple species exhibited highly congruent declines during the 1960s-1980s − a period with rapid changes in farming practices to low tillage systems, heavy pesticide use and widespread conversion of grassland habitat to cropland. The most severe declines occurred in aerial insectivorous birds (average change of −39.5% from 1966 to 2013), followed by grassland (‐20.8%) and shrubland (‐16.5%) bird species. Direct agricultural drivers impacting bird abundance, survival, and reproduction include loss of natural habitats, interference from farming equipment, and direct mortality or sublethal effects from pesticide exposure. Subtle interference with behaviour or physiology are reported through indirect drivers such as reduced food supplies, sublethal pesticide toxicity, habitat fragmentation and alteration, and disturbance. Indirect effects are likely significant for many species, particularly aerial insectivores, but detailed mechanistic studies are lacking. Our review of 122 studies found that pesticides (42% of all studies), followed by habitat loss or alterations (27%), were most predominant in negatively affecting farmland birds, with pesticides (93% negative) and mowing/harvesting (81% negative) having the most consistently negative effects. Modifications to farmland management such as reducing pesticide inputs through integrated pest management and maintaining or restoring uncultivated field margins and native habitat could positively influence farmland birds without significantly reducing agricultural crop yields.
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