Effects Of Grazing Research Articles

Effects of grazing and climate change on aboveground standing biomass and sheep live weight changes in the desert steppe in Inner Mongolia, China

CONTEXTThe Stipa breviflora desert steppe ecosystem is fragile and sensitive to climate change and grazing disturbance. Previous studies have reported the effects of climate change and grazing on aboveground standing biomass of the plant community and sheep live weight, however, the interaction between climate change and grazing remains unclear. Process models have become ideal tools for the evaluation of the effects of grazing management practices under climate change. OBJECTIVEWe used the Soil-Plant-Atmosphere Continuum System (SPACSYS) model to investigate aboveground standing biomass and the live weight of sheep in the desert steppe of Inner Mongolia under future climate change scenarios and different grazing management. The results will be used to inform adaptive management strategies. METHODSThe grazing experiment consisted of four treatments: no grazing (0 sheep ha−1 half year−1), light stocking rate (0.91 sheep ha−1 half year−1), moderate stocking rate (1.82 sheep ha−1 half year−1), and high stocking rate (2.71 sheep ha−1 half year−1). We used observed data on soil temperature, soil volumetric water content, changes to sheep live weight, and aboveground standing biomass of plant community to provide parameterization and validation for the SPACSYS model. We then predicted aboveground standing biomass of the plant community and sheep live weight changes for different grazing management under three representative concentration pathways (RCP) scenarios (RCP 2.6, RCP 4.5, and RCP 8.5) from 2021 to 2100. RESULTS AND CONCLUSIONSModerate and high stocking rates decreased aboveground standing biomass and sheep live weight changes more than the light stocking rate. A light stocking rate can maintain higher aboveground standing biomass and sheep live weight as well as meet production requirements. Therefore, a light stocking rate is a potentially effective management approach to improve food production security and combat global climate change in the desert steppe. SIGNIFICANCEThe model can inform management strategies for grazing in the desert steppe under climate change, supporting efforts to maintain the stability of the steppe ecosystem and increase economic benefits, while also providing a theoretical basis for adaptive management in the desert steppe.

Influence of the Keystone Grazer, Sesarma reticulatum, on the Hydrology and Organic Matter Cycling in Salt Marshes of the Southeastern USA

AbstractIn salt marshes of the Southeastern USA, purple marsh crabs (Sesarma reticulatum), hereafter Sesarma, aggregate in grazing and burrowing fronts at the heads of tidal creeks, accelerating creek incision into marsh platforms. We explored the effects of this keystone grazer and sediment engineer on salt marsh sediment accumulation, hydrology, and carbon (C) and nitrogen (N) turnover using radionuclides (210Pb and 7Be), total hydrolyzable amino acids (THAA), and C and N stable isotopes (δ13C and δ15N) in sediment from paired Sesarma-grazed and un-grazed creeks. Sesarma-grazed-creek sediments exhibited greater bioturbation and tidal inundation compared to sediments in un-grazed creeks, as indicated by larger 210Pb and 7Be inventories. Total organic carbon (TOC) to total nitrogen (TN) weight ratios (C:N) were higher and δ15N values were lower in grazed-creek sediments than in un-grazed-creek sediments, suggesting Sesarma remove and assimilate N in their tissues, and excrete N with lower δ15N values into sediments. In support of this inference, the percent total carbon (TC) and percent TOC declined by nearly half, percent TN decreased by ~ 80%, and the C:N ratio exhibited a ~ threefold increase between Sesarma fore-gut and hind-gut contents. An estimated 91% of Sesarma’s diet was derived from Spartina alterniflora, the region’s dominant salt marsh plant. We found that, as Sesarma grazing fronts progress across marsh landscapes, they enhance the decay of Spartina-derived organic matter and prolong marsh tidal inundation. These findings highlight the need to better account for the effects of keystone grazers and sediment engineers, like Sesarma, in estimates of the stability and size of blue C stores in coastal wetlands.

Multiple global change factors cause declines of a temperate bryophyte

ABSTRACT Background Climate change, nutrient enrichment and land use have been predicted to alter bryophyte abundance and performance; we expect these factors to interact, yet experiments addressing their joint effects are missing. Aims We tested the responses of Brachythecium rutabulum, a common temperate moss species, to single and combined effects of future climatic conditions, grazing, light limitation and nutrient enrichment. We predicted that future climatic conditions, intense grazing, light limitation and nutrient enrichment have all negative effects on the survival and photosynthetic condition of B. rutabulum, and their joint effects become strong even if individual factors have only weak effects (multiple stress hypothesis). Methods We measured after two growing seasons biomass and chlorophyll fluorescence of transplanted moss colonies in full-factorial treatments of fertilisation, exclusion of sheep grazing and light amendment by LED lamps, replicated in ambient and future climatic conditions. Results Future climate and fertilisation had negligible effects on colony biomass and chlorophyll fluorescence of bryophyte colonies, whereas light amendment had positive effect on chlorophyll fluorescence and grazing exclusion had positive effect on colony biomass. Colony biomass and chlorophyll fluorescence decreased with increasing number of global change factors. Conclusion Supporting the multiple stress hypothesis, individually weak global change factors can combine to strong joint effects.

Testing effects of bottom-up factors, grazing, and competition on New Zealand rocky intertidal algal communities.

Top-down and bottom-up factors and their interaction highlight the interdependence of resources and consumer impacts on food webs and ecosystems. Variation in the strength of upwelling-mediated ecological controls (i.e., light availability and herbivory) between early and late succession stages is less well understood from the standpoint of influencing algal functional group composition. We experimentally tested the effect of light, grazing, and disturbance on rocky intertidal turf-forming algal communities. Studies were conducted on the South Island of New Zealand at Raramai on the east coast (a persistent downwelling region) and Twelve Mile Beach on the west coast (an intermittent upwelling region). Herbivory, light availability, and algal cover were manipulated and percent cover of major macroalgal functional groups and sessile invertebrates were measured monthly from October 2017 to March 2018. By distinguishing between algal functional groups and including different starting conditions in our design, we found that the mosaic-like pattern of bare rock intermingled with diverse turf-forming algae at Twelve Mile Beach was driven by a complex array of species interactions, including grazing, predation, preemptive competition and interference competition, colonization rates, and these interactions were modulated by light availability and other environmental conditions. Raramai results contrasted with those at Twelve Mile Beach in showing stronger effects of grazing and relatively weak effects of other interactions, low colonization rates of invertebrates, and light effects limited to crustose algae. Our study highlights the potential importance of an upwelling-mediated 3-way interaction among herbivory, light availability, and preemption in structuring contrasting low rocky intertidal macroalgal communities.

Intensive pasture management alters the composition and structure of plant-pollinator interactions in Sibiu, Romania.

Land management change towards intensive grazing has been shown to alter plant and pollinator communities and the structure of plant-pollinator interactions in different ways across the world. Land-use intensification in Eastern Europe is shifting highly diverse, traditionally managed hay meadows towards intensive pastures, but few studies have examined how this influences plant-pollinator networks. We hypothesized that the effects of intensive grazing on networks will depend on how plant communities and their floral traits change. We investigated plant and pollinator diversity and composition and the structure of plant-pollinator interactions near Sibiu, Romania at sites that were traditionally managed as hay meadows or intensive pastures. We quantified the identity and abundance of flowering plants, and used transect walks to observe pollinator genera interacting with flowering plant species. We evaluated the effects of management on diversity, composition and several indices of network structure. Pollinator but not plant diversity declined in pastures and both plant and pollinator taxonomic composition shifted. Functional diversity and composition remained unchanged, with rather specialized flowers having been found to dominate in both hay meadows and pastures. Apis mellifera was found to be the most abundant pollinator. Its foraging preferences played a crucial role in shaping plant-pollinator network structure. Apis mellifera thus preferred the highly abundant Dorycnium herbaceum in hay meadows, leading to hay meadows networks with lower Shannon diversity and interaction evenness. In pastures, however, it preferred less abundant and more generalized flower resources. With pollinators being overall less abundant and more generalized in pastures, we found that niche overlap between plants was higher. With both hay meadows and pastures being dominated by plant species with similar floral traits, shifts in pollinator preferences seem to have driven the observed changes in plant-pollinator interaction networks. We thus conclude that the effects of grazing on pollinators and their interactions are likely to depend on the traits of plant species present in different management types as well as on the effects of grazing on plant community composition. We thereby highlight the need for better understanding how floral abundance shapes pollinator visitation rates and how floral traits may influence this relationship.

Flooding Length Mediates Fencing and Grazing Effects on Soil Respiration in Meadow Steppe.

Grassland management affects soil respiration (Rs, consists of heterotrophic respiration and autotrophic respiration) through soil micro-ecological processes, such as hydrothermal, plant root, organic carbon decomposition and microbial activity. Flooding, an irregular phenomenon in grasslands, may strongly regulate the response of soil respiration and its components to grassland management, but the regulatory mechanism remains unclear. We conducted a 3-year experiment by grassland management (fencing and grazing) and flooding conditions (no flooding (NF), short-term flooding (STF) and long-term flooding (LTF)) to study their effects on Rs and its components in a meadow steppe in the Hui River basin of Hulunbuir. We found differences in the patterns of Rs and its components under grassland management and flooding conditions. In 2021-2023, the temporal trends of Rs, heterotrophic respiration (Rh) and autotrophic respiration (Ra) were generally consistent, with peaks occurring on days 190-220, and the peaks of grazing were higher than that of fencing. In NF, Rs of grazed grassland was significantly higher than that of fenced grassland in 2021-2022 (p < 0.05). In STF and LTF, there was no significant difference in Rs between fenced and grazed grassland (p > 0.05). The dependence of Rs on soil temperature (ST) decreased with increasing flooding duration, and the dependence of Rs on ST of grazed grassland was higher than fenced grassland under NF and STF, but there was no difference between fenced grassland and grazed grassland under LTF. In addition, Rh was more sensitive to ST than Ra. This may be due to the different pathways of ST effects on Rs under grazing in different flooding conditions. Our study indicates that the effect of flooding on Rs is the key to the rational use of grassland under future climate change. To reduce regional carbon emissions, we recommend grazing on flooding grassland and fencing on no-flooding grassland.

Modeling the effect of grazing on carbon and water use efficiencies in grasslands on the Qinghai–Tibet Plateau

BackgroundCarbon and water use efficiencies (CUE and WUE, respectively) are vital indicators of the adaptability of plants to environmental conditions. However, the effects of grazing and climate change on the spatiotemporal changes in CUE and WUE in Qinghai–Tibet Plateau grasslands (QTPG) are still unclear.ResultsUsing the enhanced Biome-BGCMuSo model in combination with observed data, we estimated and analyzed the spatiotemporal variations in CUE and WUE and their responses to grazing in QTPG from 1979 to 2018. The mean annual CUE was 0.7066 in QTPG from 1979 to 2018 under the actual climate scenario. In general, the grassland CUE was low in the southeast and high in the northwest. Grazing generally decreased CUE in QTPG from 1979 to 2018, and there was an increasing trend in the difference in CUE between the grazing and nongrazing scenarios. The difference in CUE was generally greater in the northwest than in the southeast. The mean annual WUE was 0.5591 g C/kg H2O in QTPG from 1979 to 2018 under the actual climate scenario. After 2000, the grassland WUE exhibited a fluctuating upward trend. In general, the grassland WUE was greater in the southeast than in the northwest. Grazing generally decreased WUE in QTPG from 1979 to 2018, and there was an increasing trend in the difference in WUE between the grazing and nongrazing scenarios. The difference in WUE was generally greater in the northwest than in the southeast.ConclusionsThe findings of this study suggested that the spatiotemporal changes in CUE and WUE in QTPG were closely related to changes in the natural environment and grazing management.

How Do Nitrogen Deposition, Mowing, and Deer Grazing Drive Vegetation Changes on Dune Heaths?

Heathland vegetation has undergone significant changes in the past century, e.g., due to airborne pollutants and a lack of proper management. Understanding the interactions between these factors in combination is pivotal for heathland conservation. Here, we studied the vegetation changes at a dune heath in a four-year manipulation experiment analysing the combined effects of nitrogen deposition, mowing, and deer grazing. Our results showed no significant effect of nitrogen deposition and deer grazing on plant growth and cover of dwarf shrubs within the experimental plots. However, high loads of nitrogen decreased bryophyte cover and increased the growth and cover of sand sedge Carex arenaria L. Mowing adversely affected the dwarf shrub community, e.g., the dwarf shrub species crowberry Empetrum nigrum L., and facilitated increased cover and plant growth of graminoids. Plant growth and the cover of C. arenaria increased in plots without deer grazing, whereas bryophyte cover decreased significantly without grazing. We do not recommend intensive mowing of vegetation as a conservation method for dune heaths because it promotes graminoids. From a conservation aspect, it is essential to consider the effect of deer on heathlands because they both impede some species and benefit others and mitigate the adverse effects of nitrogen deposition on dune heaths.

Strands of connection: unraveling livestock grazing effects on orb-weaver spiders

Studies on the effects of grazing disturbances in grasslands have shown mixed results for spider diversity, mainly regarding their guilds. While ungrazing, low, and moderate grazing potentially enhance the diversity of orb-weavers in spider communities, heavy grazing seems to reduce species’ richness. On the population level though, studies of orb-weavers are scarce, and the effects of grazing in natural grasslands are unknown. In this way, we investigated the effects of different grazing levels on population persistence of orb-weaver spiders, hypothesizing that low to intermediate disturbances benefit populations. We predict that high grazing, due to the removal of vegetation structure, will negatively affect the occupancy and abundance of orb-weavers. For that, we experimentally controlled grazing pressure and obtained population occurrence and counts of two orb-weaver spider species, Argiope argentata and Alpaida quadrilorata. We found that A. argentata was negatively affected by grazing, as it relies on higher vegetation for web-building. In contrast, A. quadrilorata, which occurs in cattle-resistant rosette plants, showed no effects of grazing. Implications for insect conservation: Our study emphasizes the need for balanced grazing practices and habitat conservation to protect orb-weaver spiders and other arthropods, as well as species-specific effects for species from the same guild, underscoring their ecological significance in maintaining ecosystem stability.

Grazing effect on different forage species in yield of soybean-pasture succession

Integrated crop-livestock systems play a crucial hole on sustainable intensification due simultaneous increase the land use efficiency and minimize nutrient leaching due an intensification of nutrient cycling. However, these benefits depend on a good planning and management of the production system. The main objective of this study was to investigate biomass composition, soybean yield and beef cattle performance using three distinct forage cultivars within two cropping systems: Integrated Crop-Livestock System (ICLS) and the Pure Crop System (CS). The three forage cultivars used were: Urochloa ruziziensis, Urochloa brizantha cv. Xaraés, and Megathyrsus maximus cv. BRS Quênia. The experimental area was split into 24 plots, with each plot assigned one of the cropping systems and a specific forage cultivar. The ICLS involved soybean cultivation during spring-summer followed by cattle grazing during the autumn-winter. Conversely, the CS functioned as a pure crop system, utilizing soybean cultivation alongside forage as a cover crop. Soybean yield did not differ between ICLS and CS, neither between forage cultivars (4110 ± 627.0 kg ha−1). Animal performance did not differ between forage cultivars, resulting in average daily gain equals to 0.538 ± 0.316 kg of BW day−1. Animal production per area also was not affected by forage cultivars, yielding 145.0 ± 56.8 kg of BW ha−1. For comparison between systems, beef cattle production was converted in soybean equivalent based on commodities values. ICLS proportionated an increment of 624 ± 135 kg ha−1 per year of soybean equivalent yield, representing 15% increase in land use efficiency compared to the CS system. Therefore, beef cattle grazing in off-season of cash crops can enhance the sustainable intensification of food production. The forage species choice seems not be a paramount question for this model of ICLS.

Contrasting effects of sheep and cattle grazing on foliar fungal diseases by changing plant community characteristics

Abstract Pathogens are ubiquitous in ecosystems and play a key role in affecting host community structure. In grasslands, large grazing animals such as cattle and sheep have been shown to affect foliar fungal pathogens. However, theory and empirical studies have come to conflicting conclusions because grazers can directly and indirectly impact pathogens through a wide variety of mechanisms and various grazers may impact pathogens in different ways. A better understanding of the mechanisms by which grazers impact pathogens is important for a fundamental understanding of herbivore pathogen interactions and also to optimise grazing managements to reduce pathogen outbreaks. Here, we investigate multiple mechanisms by which livestock grazing impacts foliar fungal pathogens in grasslands. We integrate a large‐scale grazing experiment, with a removal experiment manipulating plant density and litter biomass, to identify direct and indirect effects of two herbivores on pathogens with different life histories (biotrophs and necrotrophs), in a temperate grassland in northeast China. We found that grazing by cattle and sheep had contrasting impacts: cattle grazing significantly reduced pathogen load, of both biotrophs and necrotrophs, whereas sheep grazing increased biotrophic pathogen load, but did not affect the necrotrophs. The grazing effects were mostly indirect and mediated by different impacts of the herbivores on plant community structure. Cattle grazing reduced pathogen load because it reduced the abundance of susceptible, fast‐growing plants, and the overall density of plants, while sheep grazing increased pathogen infection because it reduced the abundance of resistant plant species. Plant diversity also reduced pathogen infection but these effects were independent of the herbivores. Our results show that different herbivores can have contrasting impacts on pathogen infection through contrasting impacts on host community competence. This suggests the importance of considering multiple mechanisms simultaneously to evaluate the impact of herbivores on host‐pathogen interactions. Read the free Plain Language Summary for this article on the Journal blog.

Re-oligotrophication and warming stabilize phytoplankton networks

Phytoplankton taxa are strongly interconnected as a network, which could show temporal dynamics and non-linear responses to changes in drivers at both seasonal and long-term scale. Using a high quality dataset of 20 Danish lakes (1989–2008), we applied extended Local Similarity Analysis to construct temporal network of phytoplankton communities for each lake, obtained sub-network for each sampling month, and then measured indices of network complexity and stability for each sub-network. We assessed how lake re-oligotrophication, climate warming and grazers influenced the temporal dynamics on network complexity and stability of phytoplankton community covering three aspects: seasonal trends, long-term trends and detrended variability. We found strong seasonality for the complexity and stability of phytoplankton network, an increasing trend for the average degree, modularity, nestedness, persistence and robustness, and a decreasing trend for connectance, negative:positive interactions and vulnerability. Our study revealed a cascading effect of lake re-oligotrophication, climate warming and zooplankton grazers on phytoplankton network stability through changes in network complexity characterizing diversity, interactions and topography. Network stability of phytoplankton increased with average degree, modularity, nestedness and decreased with connectance and negative:positive interactions. Oligotrophication and warming stabilized the phytoplankton network (enhanced robustness, persistence and decreased vulnerability) by enhancing its average degree, modularity, nestedness and by reducing its connectance, while zooplankton richness promoted stability of phytoplankton network through increases in average degree and decreases in negative interactions. Our results further indicate that the stabilization effects might lead to more closed, compartmentalized and nested interconnections especially in the deeper lakes, in the warmer seasons and during bloom periods. From a temporal dynamic network view, our findings highlight stabilization of the phytoplankton community as an adaptive response to lake re-oligotrophication, climate warming and grazers.

Synergistic effects of anthropogenic disturbances on giant pandas

AbstractLivestock grazing and the collection of bamboo shoots are the main threats to giant panda (Ailuropoda melanoleuca) habitat in the Liangshan Mountains in China. It is important to clarify the effect of these disturbances to the giant panda to formulate targeted management policies. Based on species distribution models and daily activity models, we investigated the effects of livestock grazing and bamboo shoot collection on giant pandas from May 2021 to July 2022. Our results indicated the giant panda's suitable habitat in the reserve covered 51.83 km2 (15.02% of the reserve area). Grazing and bamboo shoot collection led to losses of 19.08 km2 and 7.68 km2 of suitable habitat, respectively. Together, the 2 activities resulted in a loss of 28.35 km2 of suitable habitat, which was more than half of the area of panda habitat. The areas of suitable habitat for giant pandas significantly overlapped with the areas affected by both disturbances. Giant pandas did not show significant differences in daily activity rhythms under a single disturbance, but the daily activity rhythms of giant pandas differed when we compared the area combining the 2 disturbances with the undisturbed area. Our study reveals that the anthropogenic disturbances in the reserve have varying effects on the suitable habitat range and daily activity rhythm of giant pandas and evidence of a synergistic effect. Therefore, when formulating relevant conservation policies, it is important to fully evaluate the extent and characteristics of anthropogenic disturbances in shaping the population distribution and habitat preferences of the giant panda and other wildlife to enhance the efficacy of conservation management practices.

Effects of grazing in different intensities and 10‐year grazing exclusion on soil bacterial community composition and interaction complexity in alpine grasslands of the Qinghai‐Tibet Plateau

AbstractTo decrease the detrimental consequences of overgrazing on the sustainability of grassland ecosystems, many countries have developed policies on grazing exclusions. However, compared with grazing, how grazing exclusion modifies soil bacterial community and the associated environmental drivers is inadequately understood. Here, we studied the effects of grazing in different intensities (no grazing, light, moderate, and heavy grazing) and 10 years' grazing exclusion on soil bacteria community and associated environmental factors in the grassland of the Qinghai‐Tibet Plateau. The results showed significant changes in soil bacterial composition among all the treatments. After 10 years' grazing exclusion, the composition of the bacterial community rather than bacterial diversity was significantly different from that in grassland without grazing treatment. Under grazing exclusion, bacterial community composition was regulated by the total nitrogen and nitrate nitrogen. Grazing treatments decreased the complexity of the bacterial co‐occurrence network, but 10 years' grazing exclusion increased the complexity. This study found that grazing in different intensities substantially affected bacterial community structure and diversity, but 10 years' grazing exclusion hardly alleviated the historical grazing effects on the bacterial community structure. The findings of the study extended the understanding of how bacterial communities in grasslands respond to grazing in different intensities and grazing exclusion, providing a crucial scientific foundation for evaluating sustainable grazing management.

Effects of climate change and grazing on the soil organic carbon stock of alpine wetlands on the Tibetan Plateau from 2000 to 2018

The Tibetan Plateau has been undergoing profound warming and slight wetting over recent decades, which have contradictory effects on soil organic carbon (SOC) by enhancing plant growth and thereafter carbon input into the soil and increasing the soil organic carbon decomposition rate. In this study, we developed a SOC model (WetlandC model) for wetlands, considering the process of litterfall decomposition and parameterizing the effect of grazing on SOC accumulation. We also established a modelling framework to combine the WetlandC model with the terrestrial ecosystem model (TEM model) to simulate the changes in SOC in the alpine wetlands on the Tibetan Plateau from 2000 to 2018. The results showed that spatially, the soil organic carbon density (SOCD) of alpine wetlands was higher in the southeast and lower in the northwest, ranging from 1358.22 to 22571.81 g C m−2. Precipitation played an important role in regulating the spatial heterogeneity of SOCD. The temporal trends of SOCD varied from −55.84 to 407.59 g C m−2 yr−1, and 97.98% of the wetland area accumulated SOC. Temperature, precipitation and livestock carrying, as the top influencing factors of the temporal trend of SOCD, accounted for 35.1%, 34.5% and 30.4% of the area in the alpine wetlands, respectively. The 0–30 cm SOC stock of the alpine wetlands on the Tibetan Plateau increased from 518.06 Tg C in 2000 to 607.67 Tg C in 2018. The surface soil of alpine wetlands acted as a carbon sink of 4.98 Tg C yr−1. Our results indicated that in the context of climate change, additional soil carbon sequestration in the alpine wetlands was facilitated by enhanced plant growth, although grazing consumed the aboveground biomass. Future climate warming and wetting are likely to benefit SOC accumulation in the alpine wetlands on the Tibetan Plateau if overgrazing does not occur.

Interplay between Livestock Grazing and Aridity on the Ecological and Nutritional Value of Forage in Semi-arid Mediterranean Rangelands (NE Spain)

Rangeland-based livestock production constitutes a primary source of livelihood for many inhabitants of dryland regions. Their subsistence relies heavily on maintaining the productivity, biodiversity and services of these ecosystems. Harsh environmental conditions (e.g., drought) combined with land use intensification (e.g., overgrazing) make dryland ecosystems vulnerable and prone to degradation. However, the interplay between livestock grazing intensity and aridity conditions in driving the conservation and nutritional value of forage in arid and semi-arid rangelands is still not fully understood. In this study, we performed structural equation models (SEM) to assess the simultaneous direct and indirect effects of livestock grazing intensity and aridity level on community structure, diversity, biomass, forage production, forage C:N ratio and forage fiber composition in two semi-arid Mediterranean rangelands, NE Spain. Not surprisingly, we found that higher livestock grazing intensity led to lower community plant cover, especially when combined with higher aridity. However, both increasing grazing intensity and aridity were associated with higher forage production after one year of grazing exclusion. We did not find any adverse effect of livestock grazing on plant diversity, although plant species composition differed among grazing intensity levels. On the other hand, we found an aridity-driven trade-off in regard of the nutritional value of forage. Specifically, higher aridity was associated with a decrease in the least digestible fiber fraction (i.e., lignin) and an increase in forage C:N ratio. More interestingly, we found that livestock grazing modulated this trade-off by improving the overall forage nutritional value. Altogether, our results provide further insights into the management of semi-arid Mediterranean rangelands, pointing out that maintaining traditional rangeland-based livestock production may be a sustainable option as long as rangeland conservation (e.g., community plant cover) is not severely compromised.

Soil quality and vegetation cover characteristics as influenced by diverse grazing regimes and soil disturbance histories in a semi-arid rangeland (Iran)

This study investigates the soil functioning and regeneration processes in a semi-arid rangeland subject to an eleven-year conservation grazing (CG) program within the Gonbad paired watershed in Hamadan, Iran. Five distinct sites with varying rangeland vegetation cover were selected based on differences in grazing regimes and soil disturbance histories. These sites include: CG site with Astragalus-Artemisia vegetation (CG(A-A)); CG site with Astragalus-Bromus vegetation (CG(A-B)); CG site, easily accessible to grazing livestock, with Astragalus-Lactuca vegetation (CG(EA)); CG site with a history of past rainfed farming and Centaurea-Grasses vegetation (CG(PRF)); and free grazing (FG) site with Astragalus-Euphorbia vegetation. In addition, a long-term rainfed farming site (RF) was studied as the dominant land use. Rangeland management practices had a discernible impact on nearly all soil quality (SQ) indicators. However, due to their strong interdependence, only soil aggregate stability, carbohydrates, and phosphatase activity proved to be critical indicators representing soil functioning in the area. The general SQ index illustrated a decline in soil functioning at RF (58%), CG(PRF) (55%), FG (42%), and CG(EA) (22%) sites compared to sites classified as "good" (CG(A-A) and CG(A-B)). Total organic carbon and carbon stock were only recovered in well-restored sites, characterized by a predominance of shrubs and perennial grasses. Meanwhile, active carbon and carbohydrates revealed the positive effects of conservation grazing in moderately and poorly restored sites, characterized by a predominance of forbs and annual grasses. Our findings suggest that soil disturbance history and grazing accessibility are critical factors for successfully implementing conservation grazing management in the area.

Controlling toxic Microcystis blooms: The power of a novel microalgal predator Poteriospumella lacustris in water safety improvement

Microcystis aeruginosa blooms have become a global environmental concern. In particular, microcystins (MC) produced by algal cells pose a great threat to aquatic ecosystem security and human health. Therefore, it is necessary to develop environmentally friendly biological measures to reduce bloom hazards. In this study, a heterotrophic flagellate, NY1, that could quickly eliminate M. aeruginosa and efficiently remove MC was isolated and identified as Poteriospumella lacustris. When the initial cell density ratio of P. lacustris to M. aeruginosa was 1:200, P. lacustris rapidly ingested M. aeruginosa, and the clearance rates were more than 90 % within 24 h. P. lacustris effectively removed 83.06 % of MC (more than 200 μg/L) in 24 h and 93.88 % in 72 h. Although temperatures lower than 15 °C and acidic conditions (pH 6) slightly and temporarily inhibited the ingestion and MC removal activities of P. lacustris within 24 h of treatment, it rapidly recovered and ingested more than 90 % of M. aeruginosa and eliminated 97 % of MC within 72 h at various temperatures (15–35 °C) and different pH values (pH 6–10). The fluorescence emission-excitation matrix spectra analysis and acute toxicity test showed that P. lacustris treatment reduced dissolved organic matter (DOM) and eliminated the toxicity of M. aerugionsa culture to three representative species at different trophic levels (Photobacterium phosphoreum, Daphnia magna, and Ctenopharyngodon idellus), indicating the promising potential of P. lacustris in improving water safety. In addition to M. aeruginosa, P. lacustris ingested and digested Platymonas subcordiformis, Chlorella vulgaris, and Synechocystis sp. This study provides a natural and biological solution to global Microcystis blooms by using the grazing effect of P. lacustris to remove toxic cyanobacteria and eliminate MC and DOM, ultimately improving water quality and safety.

The legacy of millennial-scale land-use practices on landscape composition, diversity and slope erosion in the subalpine areas of Eastern Carpathians, Romania

We conducted multi-proxy analyses in two subalpine lakes, Lake Gropile, in the Rodna Mountains and Lake Vinderelu in the Maramureș Mountains, the Eastern Carpathians, Romania, to investigate the effect of different land-use practices on landscape composition, diversity and slope erosion. In the case of Lake Gropile, results evidenced a more extended tree and shrub cover and high fire activity between 6400 and 2800 cal yr BP, accompanied by reduced soil erosion, which appeared more strongly regulated by climatic conditions. Anthropogenic impact became evident 2800 years ago, when landscape openness, pasturing, and disturbance of soil cover increased and intensified over the last four centuries. In the case of Lake Vinderelu, intensified burning was followed by grazing around 1200–1100 cal yr BP and continued throughout the last millennium. Results also highlight the site-specific effects of land-use on vegetation composition and landscape diversity. For Lake Vinderelu, a combined effect of local burning and grazing in removing shrub cover appear to be the main drivers of changes in landscape diversity and structure. At Lake Gropile, fire was more connected to shrub cover changes while grazing to herbaceous cover diversity. Moderate to low grazing appeared to benefit both subalpine ecosystems, creating rich grassland-shrub mosaic communities, while overgrazing reduced landscape diversity and exacerbated erosion. Our findings document the millennial-scale legacy of land-use practices on the subalpine landscapes in this region. We propose that these semi-natural ecosystems hold important ecological and cultural value, and recommend their maintenance through controlled, low intensity pasturing and/or burning.

Contrasting roles of fungal and oomycete pathogens in mediating nitrogen addition and winter grazing effects on biomass.

Both bottom-up and top-down processes modulate plant communities. Fungal and oomycete pathogens are most common in global grasslands, and due to differences in their physiology, function, host range, and life cycles, they may differentially affect plants (in both intensity and direction). However, how fungal and oomycete pathogens regulate bottom-up and top-down effects on plant community biomass remains unclear. To this end, we conducted a 3-year field experiment in an alpine meadow incorporating mammalian herbivore exclosure, fungicide/oomyceticide application, and nitrogen addition treatments. We arranged 12 blocks with half randomly assigned to be mammalian herbivore exclosures (fenced to exclude grazing sheep), and the other half were fenced most of the year but not in winter (winter grazing control). Six 2.5 × 2.5 m square plots were established in each block, with each of the six plots assigned as control, nitrogen addition, fungicide application, oomyceticide application, nitrogen addition + fungicide application, and nitrogen addition + oomyceticide application. We found that fungicide application significantly increased plant community biomass (mainly Poaceae species) under nitrogen addition and promoted the bottom-up effect of nitrogen addition on plant community biomass by altering the community-weighted mean of plant height (via species turnover). Meanwhile, oomyceticide application significantly increased plant community biomass (mainly Poaceae species) when mammalian herbivores were excluded and weakened the top-down effect of winter grazing on plant community biomass by driving intraspecific variation in plant height. Our results highlight that fungal and oomycete pathogens play important (but differing) roles in mediating the effects of nutrient availability and higher trophic levels on plant community biomass. Mechanistically, we demonstrated that plant pathogen-related modulation of plant community biomass is achieved by alterations to plant height. Overall, this study combines both community and disease ecology to reveal complex interactions among higher trophic levels and their potential impacts on terrestrial ecosystem functioning under human disturbance.