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Grazing, fire, and climate shape mesic grassland communities. With global change altering all three factors, understanding how grasslands respond to changes in these combined drivers may aid in projecting future changes in grassland ecosystems. We manipulated rainfall and simulated grazing (clipping) in two long-term fire experiments in mesic grasslands in North America (NA) and South Africa (SA). Despite their common drivers, grasslands in NA and SA differ in evolutionary history. Therefore, we expected community structure and production in NA and SA to respond differently to fire, grazing, and drought. Specifically, we hypothesized that NA plant community composition and production would be more responsive than the SA plant communities to changes in the drivers and their interactions, and that despite this expected stability of SA grasslands, drought would be the dominant factor controlling production, but grazing would play the primary role in determining community composition at both sites. Contrary to our hypothesis, NA and SA grasslands generally responded similarly to grazing, drought, and fire. Grazing increased diversity, decreased grass cover and production, and decreased belowground biomass at both sites. Drought alone minimally impacted plant community structure, and we saw similar treatment interactions at the two sites. Drought was not the primary driver of grassland productivity, but instead drought effects were similar to or less than grazing and fire. Even though these grasslands differed in evolutionary history, they responded similarly to our fire, grazing, and climate manipulations. Overall, we found community and ecosystem convergence in NA and SA grasslands. Grazing and fire are as important as climate in controlling mesic grassland ecosystems on both continents.

Little is currently known about how climate modulates the relationship between plant diversity and soil organic carbon and the mechanisms involved. Yet, this knowledge is of crucial importance in times of climate change and biodiversity loss. Here, we show that plant diversity is positively correlated with soil carbon content and soil carbon-to-nitrogen ratio across 84 grasslands on six continents that span wide climate gradients. The relationships between plant diversity and soil carbon as well as plant diversity and soil organic matter quality (carbon-to-nitrogen ratio) are particularly strong in warm and arid climates. While plant biomass is positively correlated with soil carbon, plant biomass is not significantly correlated with plant diversity. Our results indicate that plant diversity influences soil carbon storage not via the quantity of organic matter (plant biomass) inputs to soil, but through the quality of organic matter. The study implies that ecosystem management that restores plant diversity likely enhances soil carbon sequestration, particularly in warm and arid climates.

Random species loss has been shown experimentally to reduce ecosystem function, sometimes more than other anthropogenic environmental changes. Yet, controversy surrounds the importance of this finding for natural systems where species loss is non‐random. We compiled data from 16 multi‐year experiments located at a single native tallgrass prairie site. These experiments included responses to 11 anthropogenic environmental changes, as well as non‐random biodiversity loss either the removal of uncommon/rare plant species or the most common (dominant) species. As predicted by the mass ratio hypothesis, loss of a dominant species had large impacts on productivity that were comparable to other anthropogenic drivers. In contrast, the loss of uncommon/rare species had small effects on productivity despite having the largest effects on species richness. The anthropogenic drivers that had the largest effects on productivity nitrogen, irrigation, and fire experienced not only loss of species but also significant changes in the abundance and identity of dominant species. Synthesis. These results suggest that mass ratio effects, rather than species loss per se, are an important determinant of ecosystem function with environmental change. The mass ratio effects, rather than richness loss, determine ecosystem function with environmental change.

Univariate and multivariate methods are commonly used to explore the spatial and temporal dynamics of ecological communities, but each has limitations, including oversimplification or ion of communities. Rank abundance curves (RACs) potentially integrate these existing methodologies by detailing species‐level community changes. Here, we had three goals: first, to simplify analysis of community dynamics by developing a coordinated set of R functions, and second, to demystify the relationships among univariate, multivariate, and RACs measures, and examine how each is influenced by the community parameters as well as data collection methods. We developed new functions for studying temporal changes and spatial differences in RACs in an update to the R package library(“codyn”), alongside other new functions to calculate univariate and multivariate measures of community dynamics. We also developed a new approach to studying changes in the shape of RAC curves. The R package update presented here increases the accessibility of univariate and multivariate measures of community change over time and difference over space. Next, we use simulated and real data to assess the RAC and multivariate measures that are output from our new functions, studying (1) if they are influenced by species richness and evenness, temporal turnover, and spatial variability and (2) how the measures are related to each other. Lastly, we explore the use of the measures with an example from a long‐term nutrient addition experiment. We find that the RAC and multivariate measures are not sensitive to species richness and evenness and that all the measures detail unique aspects of temporal change or spatial differences. We also find that species reordering is the strongest correlate of a multivariate measure of compositional change and explains most community change observed in long‐term nutrient addition experiment. Overall, we show that species reordering is potentially an understudied determinant of community changes over time or differences between treatments. The functions developed here should enhance the use of RACs to further explore the dynamics of ecological communities.

1. Anthropocene defaunation is the global phenomenon of human-induced animal biodiversity loss. Understanding the patterns and process of defaunation is critical to predict outcomes for wildlife populations and cascading consequences for ecosystem function and human welfare. 2. We investigated a defaunation gradient in north-eastern Gabon by establishing 24 transects at varying distances (2-30 km) to rural villages and surveying the abundance and composition of vertebrate communities. Distance from village was positively correlated with observations of hunting (shotgun shells, campfires, hunters), making it a good proxy for hunting pressure. 3. Species diversity declined significantly with proximity to village, with mammal richness increasing by roughly 1-5 species every 10 km travelled away from a village. Compared to forest far from villages, the wildlife community near villages consisted of higher abundances of large birds and rodents and lower abundances of large mammals like monkeys and ungulates. 4. Distance to nearest village emerged as a key driver of the relative abundance of five of the six taxonomic guilds, indicating that the top-down force of hunting strongly influences large vertebrate community composition and structure. Several measures of vegetation structure also explained animal abundance, but these varied across taxonomic guilds. Forest elephants were the exception: no measured variable or combination of variables explained variation in elephant abundances. 5. Synthesis and applications. Hunting is concentrated within 10 km around villages, creating a hunting halo characterized by heavily altered animal communities composed of relatively small-bodied species. Although the strongest anthropogenic effects are relatively distance-limited, the linear increase in species richness shown here even at distances 30 km from villages suggests that hunting may have altered vertebrate abundances across the entire landscape. Central African forests store > 25% of the carbon in tropical forests and are home to 3000 endemic species, but roughly 53% of the region lies within the village hunting halo. Resource management strategies should take into account this hunting-induced spatial variation in animal communities. Near villages, resource management should focus on sustainable community-led hunting programmes that provide long-term supplies of wild meat to rural people. Resource management far from villages should focus on law enforcement and promoting industry practices that maintain remote tracts of land to preserve ecosystem services like carbon storage and biodiversity.

Due to anthropogenic pressures, only 3% of the historic extent of the biodiverse longleaf pine ecosystem remains, much of which is degraded. Fire is necessary for maintaining longleaf pine savanna structure, function, and biodiversity; however, it also creates resource constraints, as nutrients are volatilized, especially in the already nutrient‐depleted soils of many longleaf pine savannas. Nutrient limitation and subsequent competition between plants can lead to changes in species diversity and productivity. Using a multiyear, chronic nutrient addition experiment, we explore how resource limitation influences restoration outcomes in longleaf pine savannas by affecting (1) productivity, (2) biodiversity metrics, and (3) community composition. In the field, we established a factorial N and P nutrient addition (10 g m−1 year−1) experiment. Nutrient additions were administered for 4 years, and plant composition and biomass were collected yearly. We measured biomass each year by functional group and calculated diversity metrics and community composition changes. Understory productivity typically increased with N and P additions, with N × P together having no additive effect. There were several significant interacting effects of nutrient addition treatments with year on our biodiversity metrics; however, the main nutrient addition effects were not significant for any biodiversity metric. Finally, community composition was significantly different in nutrient addition plots compared to control. Our results show that xeric Sandhill longleaf pine savannas exhibit distinct responses to fertilization, as fertilization led to increased productivity of the groundcover without reducing biodiversity. Low‐level, chronic nutrient inputs could influence understory structure in ways that help meet numerous management objectives, such as promoting fire spread or increasing forage availability. However, this may also present challenges, such as encouraging woody encroachment or threatening rare species. Our findings highlight the need for context‐specific approaches to longleaf pine savanna management and a careful evaluation of how nutrient dynamics interact with long‐term conservation and restoration goals. Due to anthropogenic pressures, only 3% of the historic extent of the biodiverse longleaf pine ecosystem remains, much of which is degraded. Fire is necessary for maintaining longleaf pine savanna structure, function, and biodiversity; however, it also creates resource constraints, as nutrients are volatilized, especially in the already nutrient‐depleted soils of many longleaf pine savannas. Nutrient limitation and subsequent competition between plants can lead to changes in species diversity and productivity. Using a multiyear, chronic nutrient addition experiment, we explore how resource limitation influences restoration outcomes in longleaf pine savannas by affecting (1) productivity, (2) biodiversity metrics, and (3) community composition. In the field, we established a factorial N and P nutrient addition (10 g m−1 year−1) experiment. Nutrient additions were administered for 4 years, and plant composition and biomass were collected yearly. We measured biomass each year by functional group and calculated diversity metrics and community composition changes. Understory productivity typically increased with N and P additions, with N × P together having no additive effect. There were several significant interacting effects of nutrient addition treatments with year on our biodiversity metrics; however, the main nutrient addition effects were not significant for any biodiversity metric. Finally, community composition was significantly different in nutrient addition plots compared to control. Our results show that xeric Sandhill longleaf pine savannas exhibit distinct responses to fertilization compared to other grasslands and savannas globally, as fertilization led to increased productivity of the groundcover without reducing biodiversity. Low‐level, chronic nutrient inputs could influence understory structure in ways that help meet numerous management objectives, such as promoting fire spread or increasing forage availability. However, this may also present challenges, such as encouraging woody encroachment or threatening rare species. Our findings highlight the need for context‐specific approaches to longleaf pine savanna management and a careful evaluation of how nutrient dynamics interact with long‐term conservation and restoration goals.

Aim: Lianas are an important component of forest structure in the tropics, accounting for up to 45% of total stems. Mounting evidence that tropical forests are undergoing structural changes, with a growing abundance of lianas reducing forest carbon storage potential, imparts a sense of urgency to study the drivers that control liana abundance and biomass, particularly in Africa where data come from a few, small-scale studies. Location: Gabon, Africa. Methods: In the first countrywide study of lianas, we implemented the most ambitious, large-scale forest inventory in tropical Africa to date, quantifying the density, basal area and biomass of large lianas (≥10 cm in diameter) using a systematic, random design of 104 plots located across Gabon. Additionally, we examined the relative importance of environmental variables (mean annual precipitation, mean annual temperature, seasonality, soil nitrogen, soil fertility), disturbance (effect of gaps, forest type) and forest structure (large tree biomass) in driving macroscale variation in the abundance of large lianas. Results: In total, we surveyed 1354 large lianas, and found the density, basal area and biomass of large lianas in Gabon to be comparable to that in other tropical forests. The success of large lianas was positively related to soil N, but most strongly correlated with forest structure, particularly large tree biomass. The strength of the association between large lianas and large trees increased with tree size class. Main conclusions: Forest structure and the availability of large trees may be more important predictors of the abundance and distribution of large lianas in African tropical forests than environmental variables and disturbance. Changing environmental conditions are likely to have little direct effect on large lianas, but climate change, defaunation and land-use activities that diminish forest structure and reduce the number of large trees could have strong indirect effects on large lianas in Central African forests.

Temporal community stability, here defined as temporal mean divided by temporal SD, plays an important role in predicting certain ecosystem services. However, temporal stability can change with invasion, with greater abundances of invasive species potentially having greater impacts on native community stability. The exact consequences of invasion for temporal stability are unclear and, in part, depend on the particular metric of stability measured. In rangeland ecosystems, predicable forage is important for livestock production but can be threatened by invasion. Therefore, using an observational field study conducted over three years in Wyoming, we assessed which metrics of plant community stability were altered by invasion and whether those effects were mediated by two environmental variables (light and soil moisture). Bromus arvensis and Bromus tectorum are two invasive annual weeds found across US rangelands, including the northern mixed‐grass prairies of Wyoming. We established plots along natural invasion blocks of B. arvensis and B. tectorum abundance and collected plant species composition data over three growing seasons. We tested associations between seven different metrics of plant community stability and invasion by B. arvensis and B. tectorum. We found that species turnover increases with invasion by both species, while stability of forb (both brome species), C4 grass (B. arvensis only), and C3 grass (B. tectorum only) cover decreases with invasion. All metrics of stability associated with invasion supported the hypothesis of a destabilizing effect of invasion on the native plant community. Further, we found that light and soil moisture did mediate some associations between stability and invasion. Overall, our results align with previous work suggesting that invasive annual bromes can lead to decreased native plant stability, which has important implications for forage production and, thus, food security.

In areas with diverse herbivore communities such as African savannas, the frequency of disturbance by fire may alter the top–down role of different herbivore species on plant community dynamics. In a seven year experiment in the Kruger National Park, South Africa, we examined the habitat use of nine common herbivore species across annually burned, triennially burned and unburned areas. We also used two types of exclosures (plus open access controls) to examine the impacts of different herbivores on plant community dynamics across fire disturbance regimes. Full exclosures excluded all herbivores > 0.5 kg (e.g. elephant, zebra, impala) while partial exclosures allowed access only to animals with shoulder heights ≤ 0.85 m (e.g. impala, steenbok). Annual burns attracted a diverse suite of herbivores, and exclusion of larger herbivores (e.g. elephant, zebra, wildebeest) increased plant abundance. When smaller species, mainly impala, were also excluded there were declines in plant diversity, likely mediated by a decline in open space available for colonization of uncommon plant species. Unburned areas attracted the least diverse suite of herbivores, dominated by impala. Here, herbivore exclusion, especially of impala, led to strong declines in plant richness and diversity. With no fire disturbance, herbivore exclusion led to competitive exclusion via increases in plant dominance and light limitation. In contrast, on triennial burns, herbivore exclusion had no effect on plant richness or diversity, potentially due to relatively little open space for colonization across exclosure treatments but also little competitive exclusion due to the intermediate fire disturbance. Further, the diverse suite of grazers and browsers on triennial burns may have had a compensating effect of on the diversity of grasses and forbs. Ultimately, our work shows that differential disturbance regimes can result in differential consumer pressure across a landscape and result in heterogeneous patterns in top–down control of community dynamics.

The frequency and intensity of extreme climatic events such as heatwaves are predicted to increase under continued climate change and rising atmospheric CO2. Degraded and fragmented ecosystems are at particular risk of being greatly impacted by such extreme events. The longleaf pine (LLP) savanna ecosystem, once the dominant ecosystem throughout the Southeast Coastal Plains of the United States, has been reduced to a small percentage of its pre‐colonization range. While the effect of heatwaves on grassland systems has been well explored, less focus has been given to the legacy effects of previous climatic events. Through a greenhouse experiment using Schizachyrium scoparium (little bluestem), a dominant understory grass species in LLP savanna ecosystems, we aimed to study the legacy effects of heatwaves (i.e., higher temperatures and lower precipitation and humidity) across multiple plant performance metrics and stress responses. S. scoparium had a negative response to an early heatwave, showing increased mortality, smaller maximum leaf length, fewer leaves, decreased specific leaf area (SLA), decreased leaf thickness, and reduced belowground net primary productivity (NPP) when compared to plants that did not experience a heatwave. S. scoparium individuals exposed to a late heatwave had fewer leaves, reduced SLA, and thinner leaves when compared to plants that did not experience a heatwave. While plants exposed to both an early and late heatwave experienced an increase in some stress responses as observed by increased catalase activity and plant mortality, they exhibited no change in other stress responses studied (e.g., maximum leaf length, relative growth rate, productivity, leaf thickness, peroxidase levels, or fuel load). Overall, our study revealed that S. scoparium may show neutral‐to‐positive legacy effects in response to multiple heatwaves. This indicates that LLP savanna ecosystems dominated by S. scoparium may display resistance to the predicted increased frequency of heatwaves in the southeastern United States, an important outcome for the heavily degraded and endangered ecosystem.