Herbivore Exclusion Research Articles

Challenges to Seagrass Restoration in the Indian River Lagoon, Florida

Seagrasses provide valuable ecosystem services, including improved water quality, carbon sequestration, and sediment stabilization. Unfortunately, these critical habitats are declining globally due to a range of anthropogenic impacts. Restoration practitioners have made efforts to mitigate loss through the introduction of seagrass transplants. However, seagrass restoration has low success rates and is plagued by water quality concerns and ecosystem degradation. Studies to improve seagrass restoration efforts have targeted different functional taxa to allow for greater stability and recovery of threatened ecosystems, and excluded macro-grazers to limit losses to newly established and restored seagrasses. We hypothesized greater seagrass (Halodule wrightii) health when restored in conjunction with hard clams (Mercenaria mercenaria) and protected from grazers using herbivore exclusion devices (HEDs) in the Indian River Lagoon (IRL), Florida. While our study experienced high rates of seagrass mortality, we were able to observe significant differences in seagrass health between IRL sub-lagoons and observed the positive effects of HEDs on seagrass health. The observed high species mortality highlights how restoration in the IRL is hindered by biotic and abiotic stressors, site selection, and a lack of clear restoration protocols. As we see ongoing declines in water quality and loss of foundational species, informed site selection, greater understanding of grazer presence, and multi-species restoration will provide an informed approach for future seagrass restoration projects globally.

Mitigation of disease and browsing impacts, and translocation, supports post-fire threatened flora recovery

Context For plant species that have evolved in fire-prone environments, declines after wildfires are often driven by the combination of fire and other threatening processes. Mitigating the impacts of these threatening processes can sometimes effectively support post-fire population recovery. Aims We test the effectiveness of: (1) phosphite application to mitigate Phytophthora dieback; (2) fencing to exclude browsing by mammalian herbivores; and (3) translocation to sites where threats can be practically managed, for conservation of threatened flora affected by wildfires in 2018 and 2019 in the Stirling Range (Koi Kyeunu-ruff), south-western Australia. Methods Survival of Phytophthora-susceptible flora was compared in repeatedly sampled plots from prior to and after wildfire and ± recurrent phosphite application. Survival and growth of browsing-susceptible flora was compared post-fire in fenced and control plots. Survival, growth and flowering was compared between wild populations recruiting after wildfire and translocated populations. Key results Phosphite application increased survival of most Phytophthora-susceptible flora. Fencing led to greater growth and often increased survival. Translocated populations, with supplemental water, had greater growth rates and earlier flowering than wild populations, and a non-significant trend for higher survival. Conclusions These findings provide strong evidence supporting continuation of phosphite application, herbivore exclusion and translocation for post-fire recovery of the threatened flora of the Stirling Range. Implications With increasing wildfire extent, frequency and impact across the globe, successful management of non-fire threats will be crucial for post-fire conservation of threatened flora, with the approaches proving effective in this study likely to have conservation value elsewhere.

Severely degraded high mountain vegetation recovers under different levels of wild herbivore grazing pressure, 1991–2021

Context It is important to understand the way in which wild herbivore grazing affects decadal vegetation dynamics after cessation of unnatural disturbances, especially in a context of climate change. Aims We investigated the decadal effects of different grazing regimes on treeless subalpine vegetation recovery from stock grazing and burning, on sites of different environmental character and initial state. Methods At each of four sites, two fenced areas that excluded mammalian herbivores, two that allowed in only rabbits and two grazed control plots were monitored every 5 years between 1991 and 2021. General linear models were developed to explain variation in change over the 30 years in different cover types. The years in which peak and trough values occurred were also determined, as were the incidence and direction of differences between treatments in sites and years. Key results There was marked variation in change over 30 years between the sites and lifeforms. Exclusion of mammalian herbivores increased the slow rate of revegetation. There was little effect from rabbits by themselves. Unexpectedly, the cover of both short and tall herbs was not promoted by grazing exclusion. Short term climatic variation affected some cover types, with many peaks and troughs in the dry year of 2001, but it was not possible to disentangle decades scale climate change effects from the process of recovery after disturbance. Conclusions The slight increase in revegetation rates in the absence of native herbivores and rabbits does not justify culling. Restoration interventions appear to be unnecessary. The prospect of increasing fire incidence and deer numbers suggests that it is desirable to continue monitoring the plots.

Effects of artificial pollination and herbivore exclusion on the fruit set and seed production of the golden orchid Cephalanthera falcata in Japan

Effects of artificial pollination and herbivore exclusion on the fruit set and seed production of the golden orchid Cephalanthera falcata in Japan

The effect of livestock grazing on plant diversity and productivity of mountainous grasslands in South America - A meta-analysis.

Mountainous grasslands in South America, characterized by their high diversity, provide a wide range of contributions to people, including water regulation, soil erosion prevention, livestock feed provision, and preservation of cultural heritage. Prior research has highlighted the significant role of grazing in shaping the diversity and productivity of grassland ecosystems, especially in highly productive, eutrophic systems. In such environments, grazing has been demonstrated to restore grassland plant diversity by reducing primary productivity. However, it remains unclear whether these findings are applicable to South American mountainous grasslands, where plants are adapted to different environmental conditions. To address this uncertainty, we conducted a meta-analysis of experiments excluding livestock grazing to assess its impact on plant diversity and productivity across mountainous grasslands in South America. In alignment with studies in temperate grasslands, our findings indicated that herbivore exclusion resulted in increased aboveground biomass but reduced species richness and Shannon diversity. The effects of grazing exclusion became more pronounced with longer durations of exclusion; nevertheless, they remained resilient to various climatic conditions, including mean annual precipitation and mean annual temperature, as well as the evolutionary history of grazing. In contrast to results observed in temperate grasslands, the reduction in species richness due to herbivore exclusion was not associated with increased aboveground biomass. This suggests that the processes governing (sub)tropical grassland plant diversity may differ from those in temperate grasslands. Consequently, further research is necessary to better understand the specific factors influencing plant diversity and productivity in South American montane grasslands and to elucidate the ecological implications of herbivore exclusion in these unique ecosystems.

Restoring landscape burning is compatible with conservation and livestock production in a southeast Australian grassland fragment

Abstract Lowland grassland fragments in southeast Australia are valued for both sheep grazing and conservation. Many fragments are now rarely burnt, despite being shaped by millennia of Aboriginal fire‐use. Restoring fire could potentially reduce fuels, control exotic plant species, promote native species and renew Aboriginal cultural burning. However, this requires understanding of how fire and large herbivores, both native and exotic, are coupled and influence vegetation. We implemented a single round of low‐intensity experimental burns in an area of remnant grassland and patchy eucalypt woodlands in Tasmania that is managed for conservation, albeit intermittently grazed by sheep, as well as by native and exotic wild herbivores. We compared herbivore activity between burnt and unburnt areas over 2 years using cameras and scat transects, and assessed how fire and herbivory influenced herbaceous biomass and the cover of broad vegetation classes with and without herbivore exclusion. Contrary to expectations, burnt areas did not disproportionately attract the main herbivores: domestic sheep, introduced deer and native wallabies. In the predominant grassy sward, grazing and fire both reduced herbaceous biomass but we found no support for our hypothesis that grazing reduces biomass more strongly after burning. This contrasts with isolated patches of Poa tussock grassland, where fire reduced biomass much more strongly than grazing, and grazing effects on biomass were more pronounced following burning. The cover of broad vegetation classes was little affected by burning, but excluding herbivores increased exotic grass cover in both burnt and unburnt plots. Practical implication. In degraded fragments of lowland native grassland, burning and grazing do not necessarily act as strongly synergistic disturbances. Grazing by sheep and wild herbivores can help to control exotic grasses and reduce herbaceous biomass, although burning is much more effective than grazing for reducing biomass of unpalatable Poa tussock grassland. Our results suggest that returning occasional low‐intensity fires to our study system, and other degraded grassland‐woodland fragments, can be compatible with livestock production and conservation goals, but this requires caution and adaptive management.

Ungulate herbivores promote contrasting modifications of soil properties and organic carbon stabilization in a grazed grassland versus rewilded woodland environment

Large vertebrate herbivores are ecosystem engineers, provoking cascading effects on soil properties through modifications of plant communities as well as direct modulation of organic matter incorporated into soils. However, most studies have been carried out with domestic ungulates in grasslands, and the effects which predominate in grasslands may not be generalizable to other ecosystems. It is not well understood how trophic rewilding with wild ungulates may affect soil processes, especially in non-grassland systems albeit rewilding of natural areas is a process associated with larger trends of land abandonment, shrub encroachment or land use change. In this study we investigated ungulate herbivore exclusion in two geographically and pedo-climatically equivalent but ecologically distinct contexts: a Mediterranean grassland with domesticated herbivores, and a reforested area populated by a community of wild ungulates. In each context, long-term herbivore exclusion zones were used to understand the effect of herbivores on soil properties and particularly on soil organic carbon (SOC). Samples from the topsoil (0–5 cm) were taken inside and outside the exclosures distributed between the two contexts, and ecosystem-level effects and responses to grazing were investigated. We found that soil properties’ response to grazing depended on the ecological context in which the grazing occurred. SOC contents in the grassland increased by up to 37% with grazing, while grazing reduced SOC concentrations by 23% in the rewilded area. In both cases, grazing was also associated with significant alterations of soil microbial biomass, the microbial metabolic quotient (qCO2), and aggregate stability, but the effects were opposite: On one hand, domesticated herbivores in the grassland positively influenced carbon stabilization which was strongly associated with soil microbial processes and characteristics, and additionally the proportion of stable macroaggregates was increased. In contrast, wild ungulate herbivory in the forest ecosystem reduced SOC concentrations, accompanied by decreased microbial biomass and increased microbial maintenance costs, and stable macroaggregates were reduced. The results indicate the importance of ecological context in determining the effect of herbivores on soil properties and processes and suggest that the directionality of effects on SOC may change owing to the predominance of different mechanisms of SOC stabilization. Consequently, this study provides evidence that the management of ungulates in rangelands or forests can be associated with different outcomes as related to crucial soil properties such as SOC contents and aggregation.

Native herbivore browsing alters plant physical and chemical traits in a eucalypt forest understory

AbstractMacropods exhibit selective herbivory on plant traits within and between species and hence can alter plant trait variation. In this study, we asked what are the effects of macropod herbivory on intraspecific variation in plant traits of forest understory species? We tested the effects of herbivory by macropods on eight plant traits, in nine understory species using a herbivore exclusion experiment. Generalized linear mixed models were used to test for differences between herbivory treatments in trait means as well as variation within species and at the community level. Macropod herbivory resulted in differences in either the mean trait value or trait variance within a species for seven of the eight tested plant traits. Macropod exclusion resulted in larger dimensions of size for most species, as well as changes in specific leaf area, moisture content, and carbon content of leaves. Further, community‐weighted means of specific leaf area, moisture content, and leaf nitrogen were lower in the presence of macropods. Plant trait variance was altered for three of the seven community‐weighted traits. This study demonstrates a mechanism through which macropods can drive changes in the traits of understory plant species. Plant traits have been linked to various larger scale ecological processes including ecosystem flammability, nutrient cycling, response to global change, and habitat suitability for other organisms. Therefore, herbivore‐induced changes in plant trait variation and community composition could have important flow‐on effects for other environmental processes and hence should be considered in management decisions regarding fire‐prone ecosystems.

Herbivore exclusion stabilizes alpine grassland biomass production across spatial scales.

There is growing evidence that land-use management practices such as livestock grazing can strongly impact the local diversity, functioning, and stability of grassland communities. However, whether these impacts depend on environmental condition and propagate to larger spatial scales remains unclear. Using an 8-year grassland exclosure experiment conducted at nine sites in the Tibetan Plateau covering a large precipitation gradient, we found that herbivore exclusion increased the temporal stability of alpine grassland biomass production at both the local and larger (site) spatial scales. Higher local community stability was attributed to greater stability of dominant species, whereas higher stability at the larger scale was linked to higher spatial asynchrony of productivity among local communities. Additionally, sites with higher mean annual precipitation had lower dominant species stability and lower grassland stability at both the spatial scales considered. Our study provides novel evidence that livestock grazing can impair grassland stability across spatial scales and climatic gradients.

Forest management affects ecosystem functioning (predation and herbivory) but not ecosystem constancy: A comparative study across four forest ecosystems around the world

Forest management can affect both the functioning and stability of ecosystems. Constancy and persistence are key factors that contribute to the overall stability of an ecosystem. These factors can be highly variable and change across forest ecosystems. We studied the effects of forest management on the strength of resource–consumer interactions (bird predation and insect herbivory) as important measures of ecosystem functioning, as well as on their constancy in time in four different forested regions globally. Within each region, we selected (i) three heavily managed or plantation forests, and (ii) three urban/peri-urban forests or urban plantings, and paired each of them with pristine/semi-natural forests. Bird predation was estimated using plasticine caterpillars of different colors. Chewer, galler, and miner herbivory on leaves were estimated for 15 plants (shrubs and trees) per study site. Constancy was quantified as the invariability of both predation and herbivory during a period of three (exceptionally two) years. We found no consistent responses of either predation or herbivory to forest management practices across study regions. Bird predation was higher in urban/peri-urban forests than in pristine/semi-natural forests in Patagonian and boreal forest, with intermediate levels of predation in managed or plantation forests. These differences might be explained by the increase of resource availability during the winters and by the higher abundances of generalist predators due to increase of temperatures (i.e., urban heat effect), for those regions where winter temperatures could be a limiting factor. Chewing insect herbivory was lower in urban/peri-urban forests, probably due to the exclusion of certain herbivores in response to warming and the higher predation pressure relative to pristine forests. No differences were found in other types of herbivory, indicating that effects of urbanization are guild-specific. In addition, we consistently found no effects of forest management practices on predation invariability and herbivory, thereby demonstrating the high constancy of ecosystem functioning to different forest management practices across regions. These findings advance our knowledge of the generalized effects of forest management on ecosystem functions and stability by establishing a connection between the ecology and management and conservation of plantations and natural forests.

Contrasting impacts of short‐ and long‐term large herbivore exclusion on understory net CO2 exchange in a boreal forest

Across boreal forests, trees are the main living biomass carbon (C) stock, but the understory vegetation can contribute significantly to the C cycling and net forest carbon dioxide (CO2) balance. The patchy understory vegetation, which consists of sunlit (i.e. lichen‐like) and shaded habitats (i.e. dwarf shrub‐like), is often altered by ungulate grazers. Grazers may influence understory CO2 exchange and, consequently, the forest CO2 balance. Grazing affects differently the biomass of slow‐growing lichens compared to the faster‐growing mosses and dwarf shrubs, and therefore the effects of grazing on CO2 exchange in the patchy understory vegetation may vary temporally. We studied how excluding grazing for short and long periods affects the CO2 exchange and vegetation biomass in the understory of an oligotrophic Scots pine forest. We measured growing season (2019, 2020) CO2 exchange across sunlit and shaded habitats inside fences that had excluded large grazers for 0–1 and 25–26 years and in the adjacent grazed area. In addition, we measured the height of understory vegetation. We found that short‐term grazer exclusion increased ecosystem CO2 source fluxes only in the shaded habitats. However, long‐term exclusion of grazing decreased CO2 net release regardless of the habitat type. Furthermore, grazer exclusion increased moss depth immediately, which coincided with an abrupt intensification of CO2 net release. Considering the impacts of grazing over both short‐ and long‐term periods may help to forecast C fluxes more accurately, which may be relevant for informed climate solutions regionally and even on a larger scale.

Long-term livestock exclusion increases plant richness and reproductive capacity in arid woodlands.

Herbivore exclusion is implemented globally to recover ecosystems from grazing by introduced and native herbivores, but evidence for large-scale biodiversity benefits is inconsistent in arid ecosystems. We examined the effects of livestock exclusion on dryland plant richness and reproductive capacity. We collected data on plant species richness and seeding (reproductive capacity), rainfall, vegetation productivity and cover, soil strength and herbivore grazing intensity from 68 sites across 6500 km2 of arid Georgina gidgee (Acacia georginae) woodlands in central Australia between 2018 and 2020. Sites were on an actively grazed cattle station and two destocked conservation reserves. We used structural equation modeling to examine indirect (via soil or vegetation modification) versus direct (herbivory) effects of grazing intensity by two introduced herbivores (cattle, camels) and a native herbivore (red kangaroo), on seasonal plant species richness and seeding of all plants, and the richness and seeding of four plant groups (native grasses, forbs, annual chenopod shrubs, and palatable perennial shrubs). Non-native herbivores had a strong indirect effect on plant richness and seeding by reducing vegetative ground cover, resulting in decreased richness and seeding of native grasses and forbs. Herbivores also had small but negative direct impacts on plant richness and seeding. This direct effect was explained by reductions in annual chenopod and palatable perennial shrub richness under grazing activity. Responses to grazing were herbivore-dependent; introduced herbivore grazing reduced native plant richness and seeding, while native herbivore grazing had no significant effect on richness or seeding of different plant functional groups. Soil strength decreased under grazing by cattle but not camels or kangaroos. Cattle had direct effects on palatable perennial shrub richness and seeding, whereas camels had indirect effects, reducing richness and seeding by reducing the abundance of shrubs. We show that considering indirect pathways improves evaluations of the effects of disturbances on biodiversity, as focusing only on direct effects can mask critical mechanisms of change. Our results indicate substantial biodiversity benefits from excluding livestock and controlling camels in drylands. Reducing introduced herbivore impacts will improve soil and vegetation condition, ensure reproduction and seasonal persistence of species, and protect native plant diversity.

Loss of native herbivores triggers diversity decline of ephemeral plant communities

AbstractAimEvaluate the temporal changes in species diversity, composition, and structure of ephemeral plant communities and the seed bank in response to long‐term herbivore exclusion over 11 years in plots with and without herbivores.LocationNorth‐central Chile.MethodsWe obtained information on ephemeral vegetation cover in August and September using the intercept point method and recorded seed abundance in April. The Bosque Fray Jorge National Park Long‐Term Socio‐Ecological Research (LTSER) provided these records covering 11 years (2009–2019). From the original experiment of 20 plots, we used eight plots divided into two treatments: four plots allowed free access to all herbivores (with herbivores), while the other four plots excluded herbivores (without herbivores).ResultsWe found that Hill–Shannon diversity increased in plant communities with herbivores and a temporal increase in the cover of the dominant species, Plantago hispidula, under herbivore exclusion. In wet years, species richness and temporal turnover of plant communities increased independently of treatment. Although seed abundance differed among treatments and years, population structure remained constant over time and among treatments, suggesting that the seed bank acts as a buffer against shocks that modify plant community dynamics. Structural equation modeling revealed that precipitation, via its positive effects on Plantago hispidula, increases native plant richness to a greater extent than herbivores. However, in the absence of herbivores, precipitation directly affects native species richness. Moreover, we found that precipitation also influences the native species richness of the seed bank, both directly and indirectly, although its impacts exhibit a time lag.ConclusionsOur study demonstrates that the temporal dynamics of ephemeral plant communities and seed banks in semi‐arid ecosystems are strongly coupled to climate variability, highlighting the vulnerability of these communities to biodiversity loss and climate change.

Facilitation by pioneer trees and herbivore exclusion allow regeneration of woody species in the semiarid ecosystem of central Chile

AbstractQuestionsFacilitation by pioneer plants and herbivore exclusion may contribute to plant regeneration and restoration of degraded semiarid ecosystems. In this study we evaluated the main and interactive effects of the exclusion of large and medium‐sized mammal herbivores and the presence of the pioneer tree Vachellia caven on natural regeneration of woody species in degraded savannas.LocationTwo localities of the native sclerophyllous forest of central ChileMethodsTwelve 30 × 40 m exclosures and twelve non‐exclosure areas located near native forests were established in savannas of V. caven in each locality. Regeneration coming from seeds and resprouts was sampled both under the canopy of V. caven and without canopy in each exclosure and non‐excluded area.ResultsAfter seven years, species richness and density of older regeneration (0.5–2 m high) were positively affected by herbivore exclusion and the presence of V. caven. No significant interaction between herbivore exclusion and V. caven was observed. Younger regeneration (<0.5 m high) was positively affected by herbivore exclusion and the presence of V. caven only in some years with almost no interactive effect.ConclusionsThe exclusion of large and medium‐sized exotic herbivores and facilitation by pioneer trees are complementary for regeneration. The variable but permanent presence of younger and older regeneration within exclosures and under V. caven during the experiment may lead to an increase of density and diversity of adult plants and recovery of the native forest. However, this process may be slow due to other limiting factors, for instance, reduced precipitation associated with climate change.

Large herbivore diversity slows sea ice-associated decline in arctic tundra diversity.

Biodiversity is declining globally in response to multiple human stressors, including climate forcing. Nonetheless, local diversity trends are inconsistent in some taxa, obscuring contributions of local processes to global patterns. Arctic tundra diversity, including plants, fungi, and lichens, declined during a 15-year experiment that combined warming with exclusion of large herbivores known to influence tundra vegetation composition. Tundra diversity declined regardless of experimental treatment, as background growing season temperatures rose with sea ice loss. However, diversity declined slower with large herbivores than without them. This difference was associated with an increase in effective diversity of large herbivores as formerly abundant caribou declined and muskoxen increased. Efforts that promote herbivore diversity, such as rewilding, may help mitigate impacts of warming on tundra diversity.

Size-biased compositional impacts of small mammal herbivores in an old-field plant community

Plant species height (mature height), which strongly correlates with other measures of size, is widely considered an important functional trait. Taller species contribute greatly to ecosystem function and are frequently identified as strong competitors. Additionally, important ecological processes like self-thinning scale with plant species size. In spite of the clear functional importance of species size, evidence for size-based plant community assembly rules has been scant. While herbivory can be species specific and there are reasons why herbivores may target larger plant species, it is unknown whether herbivory has size-biased impacts on species composition. In an old-field plant community, we compared plant species composition in herbivore exclusion (caged) and control plots over five years to test whether herbivore activity favors species at one end of the size spectrum. Across 5 years, smaller species were modestly, but consistently, underrepresented in caged plots compared to control plots. This underrepresentation of relatively smaller plant species in caged plots, where seedling herbivory was greatly diminished, was driven by lower small plant species richness and abundance in those plots; the abundance and richness of tall species did not differ across treatments. Our findings demonstrate that reducing herbivore activity in our study community modestly but consistently altered plant species composition, slightly favoring larger species. There was no evidence that larger species are preferentially targeted by herbivores. Some research suggests, although it will require further investigation, that seedling herbivory, regardless of the species eaten, produces vegetation gaps that small plant species are more successful in colonizing.

Litter accumulation, not light limitation, drives early plant recruitment

Abstract Theory predicts a decline in grassland diversity under nutrient enrichment and loss of herbivory, and one possible cause is hampered seedling recruitment. Two potential drivers for reduced diversity at the seedling level are diminished light availability caused by surrounding vegetation and accumulation of dead biomass. To test the importance of these two mechanisms on early recruitment, we added seeds of 15 herbaceous grassland plant species and monitored sown and natural seedling emergence during one growing season in a full factorial field experiment with light addition and litter removal under fertilization and exclusion of mammalian herbivores in an experimental grassland in Central Germany. We used modern LED lamps, mimicking the spectrum of natural sun light, to provide light to small‐statured understorey plants. This novel experimental set‐up allowed us to specifically disentangle the roles of light limitation and litter accumulation independently and in combination. In general, herbivore exclusion, but not fertilization increased the amount of litter biomass. Litter removal increased seedling number and richness by 83% and 33%, respectively, while light addition had no significant main effect on seedling recruitment, nor did it interact with any other factors, and did not affect recruitment even when litter was removed. In addition, fertilization had a negative and herbivore exclusion a negligible impact on recruitment, and these effects were independent of litter removal. Furthermore, seedling number and richness were unrelated to light intensity and quality, litter depth, soil moisture, temperature and C:N ratio. Synthesis: These results provide novel insights into the role of light limitation versus litter accumulation driving early recruitment and help understanding the mechanisms that affect diversity in grassland communities via recruitment. Our results highlight the detrimental role of litter accumulation as opposed to surrounding vegetation induced light deficiency driving early recruitment from seeds and call for management actions that reduce the amount of litter when maintaining or restoring diversity.

Drivers of the microbial metabolic quotient across global grasslands

AbstractAimThe microbial metabolic quotient (MMQ; mg CO2‐C/mg MBC/h), defined as the amount of microbial CO2 respired (MR; mg CO2‐C/kg soil/h) per unit of microbial biomass C (MBC; mg C/kg soil), is a key parameter for understanding the microbial regulation of the carbon (C) cycle, including soil C sequestration. Here, we experimentally tested hypotheses about the individual and interactive effects of multiple nutrient addition (nitrogen + phosphorus + potassium + micronutrients) and herbivore exclusion on MR, MBC and MMQ across 23 sites (five continents). Our sites encompassed a wide range of edaphoclimatic conditions; thus, we assessed which edaphoclimatic variables affected MMQ the most and how they interacted with our treatments.LocationAustralia, Asia, Europe, North/South America.Time period2015–2016.Major taxaSoil microbes.MethodsSoils were collected from plots with established experimental treatments. MR was assessed in a 5‐week laboratory incubation without glucose addition, MBC via substrate‐induced respiration. MMQ was calculated as MR/MBC and corrected for soil temperatures (MMQsoil). Using linear mixed effects models (LMMs) and structural equation models (SEMs), we analysed how edaphoclimatic characteristics and treatments interactively affected MMQsoil.ResultsMMQsoil was higher in locations with higher mean annual temperature, lower water holding capacity and lower soil organic C concentration, but did not respond to our treatments across sites as neither MR nor MBC changed. We attributed this relative homeostasis to our treatments to the modulating influence of edaphoclimatic variables. For example, herbivore exclusion, regardless of fertilization, led to greater MMQsoil only at sites with lower soil organic C (< 1.7%).Main conclusionsOur results pinpoint the main variables related to MMQsoil across grasslands and emphasize the importance of the local edaphoclimatic conditions in controlling the response of the C cycle to anthropogenic stressors. By testing hypotheses about MMQsoil across global edaphoclimatic gradients, this work also helps to align the conflicting results of prior studies.

Herbivores regulate native–alien plants dynamics in sub‐Antarctic beech (Nothofagus antarctica) forests of Tierra del Fuego, Argentina

AbstractQuestionsWhat is the role of native and domestic herbivores in native–alien vegetation changes in sub‐Antarctic forests? Does herbivory suppression increase native while reducing alien species diversity?LocationCentral–eastern Tierra del Fuego Island, Argentina.MethodsIn four sites, we set up three different treatments: excluded grazing by livestock (cattle), by livestock and native (guanaco) herbivores, and grazed control plots in Nothofagus antarctica forests. We then monitored the dynamics of understorey native and alien plants (species richness, abundance) of dicots, monocots, and ferns over 6 years. Generalized Linear Mixed Models were used to determine the effects of herbivore exclusion and time on species richness and abundance. In addition, we calculated the abundance rate of change to quantify temporal dynamics.ResultsOverall species richness did not change in the exclusion plots, but native and alien abundances were affected by herbivory and time since exclusion. The abundance of native monocots changed after herbivore exclusion, increasing its dominance significantly inside exclusion plots. However, the cessation of herbivory did not reduce alien species in general. Only alien dicots significantly declined in the livestock exclusion treatment. Further, we found that the two dominant alien grass species (Holcus lanatus and Poa pratensis) respond differently to grazing exclusion, and their response was modulated by forest basal area.ConclusionsOur results indicate that cattle and guanaco grazing had variable effects on native and alien plants, and that herbivore exclusion has a substantially positive effect on native grasses. However, the magnitude of temporal changes was more significant for vegetation richness and abundance than the effect of exclusion treatments. Herbivore exclusions can initiate a rapid recovery of compositional attributes of native vegetation in N. antarctica forests grazed by livestock.

Herbivore exclusion and water availability improve success across 76 translocations of 50 threatened plant species in a biodiversity hotspot with a Mediterranean climate

Herbivore exclusion and water availability improve success across 76 translocations of 50 threatened plant species in a biodiversity hotspot with a Mediterranean climate