Forb Community Research Articles

Plant functional group interactions intensify with warming in alpine grasslands

Plant–plant interactions regulate plant community structure and function. Shifts in these interactions due to global climate change, mediated through disproportional increases of certain species or functional groups, may strongly affect plant community properties. Still, we lack knowledge of community‐level effects of climate‐driven changes in biotic interactions. We examined plant community interactions by experimentally removing a dominant functional group, graminoids, in semi‐natural grasslands in Southern Norway. To test whether the effect of graminoid removal varied with climate, the experiment was replicated across broad‐scale temperature and precipitation gradients. To quantify community‐level interactions across sites, we tested for changes in the remaining vascular community (i.e. forbs) cover, richness, evenness, and functional traits reflecting leaf‐economic investment and plant size over five years. The effect of graminoid removal on forb community structure and functioning varied over time, and along the climate gradients. Forb cover increased in response to graminoid removal, especially at warmer sites. Species richness increased following removal irrespective of climate, whilst evenness increased under warmer and wetter conditions irrespective of removal. No climate or removal effect was found for species turnover. Functional trait responses varied along the precipitation gradient – compared to controls, forb mean SLA decreased in drier conditions after graminoid removal. Leaf thickness increased under cooler and drier conditions irrespective of removal. These community structure alterations demonstrate stronger competitive interactions between forbs and graminoids under warmer conditions, whilst functional trait responses indicate a facilitative effect of graminoids under drier conditions. This indicates that both competition and facilitation regulate plant communities, suggesting complexity when scaling from populations to communities. Finally, both temperature and precipitation determine the direction and intensity of biotic interactions, with ecosystem‐wide implications for forb persistence and ecosystem functioning under future climates. Further work is needed to generalise the role of changing interactions in mediating community responses to climate change.

Assessment of Ecosystem Services Provided by Macrophytes in Southern Baltic and Southern Mediterranean Coastal Lagoons

The ecological importance of macrophytes is well known and reflected in nature protection law, for example, as a key biological quality element. However, the socio-economic role, such as the impact of macrophyte presence on recreational activities, is often overlooked. The purpose of this study was to assess the human benefits (or ecosystem services) provided by macrophytes. We developed a list of 25 macrophyte ecosystem services and 79 assessment indicators based on expert knowledge and literature data. First, hypothetical scenarios of coastal lagoons were developed to assess the impact of different ecological states (i.e., macrophyte coverage) and management measures (i.e., fisheries) on the ecosystem service provision. Scenario assessments were carried out by stakeholder workshops and literature search. Second, the ecosystem service potential of submerged and emergent macrophyte habitats were assessed by macrophyte experts and literature data. Results showed that cultural services are most important in terms of the overall actual provision of ecosystem services (scenario assessment) but also showing highest potential of the hypothetical ecosystem service provision (habitat assessment). Highest overall potential is shown for reeds and tall forb communities (83 out of maximum 125), followed by seagrass beds (71) and seaweed communities (61). Our ecosystem service assessment approaches (i.e., scenario and habitat-based) using socio-cultural data (i.e., stakeholders and experts-based) and biophysical data (i.e., indicators-based) can serve as supportive tools for coastal management and policy implementation visualizing the benefits of macrophytes to humans.

Lower diversity of forbs in prairie restoration alters pollinator communities but not structural characteristics of plant–pollinator networks

Reestablishment of native plant communities is often the primary focus of ecological restoration. This is especially true for prairie restoration, which often struggles to establish diverse forb communities. An often‐overlooked component in plant reestablishment is pollinators, with 85% of forbs requiring pollination for seed reproduction. A deeper understanding of the relationship between plant and pollinator communities could improve prairie restoration success. Our goal was to determine if prairie restoration is successfully reestablishing forb and pollinator communities and their interactions by measuring plant–pollinator networks. We hypothesized that both forb and pollinator communities would be less diverse and abundant in restoration sites compared to intact prairie remnants, and that as a result, plant–pollinator networks in restoration sites would have higher nestedness and connectance, but lower modularity and network specialization than remnant sites. To test this, we measured plant–pollinator networks and forb communities from June to September 2020 at three restored and three remnant Palouse Prairie sites in eastern Washington, United States. We found that although restored sites had lower species richness of forbs and pollinators and different community composition, forb and pollinator abundance was comparable between treatments. Forb abundance in restored sites was equivalent to prairie remnants due to the presence of invasive forbs. However, these differences in community composition and diversity did not appear to impact network metrics including nestedness, connectance, modularity, and network specialization, which were similar between remnant and restored sites. Our results suggest that the structural characteristics of plant–pollinator networks can be maintained by different plant communities.

Multifunctional bioretention basins as urban stepping stone habitats for wildflowers and pollinators

Sustainable Urban Drainage Systems (SUDS) are increasingly used to manage precipitation events in cities and create decentralized stormwater management. To enhance ecological benefits of bioretention basins, we investigated development of native forb communities composed of 26 plant species common in northwest Europe, their provision of foraging resources, and functional connectivity between basins for pollinating insects. We used two types of engineered infiltration soil to test effects of growing conditions on plants in four basins under field conditions over three years, and in a controlled environment. Hemi-rosette grassland forbs associated with neutral to calcareous sandy soils tolerated the environmental conditions and persisted during early succession, while there was no effect of infiltration soil on community composition. Furthermore, colonisation by non-sown spontaneous plants was limited, but differed between soil types. Sown forbs and spontaneous wildflowers contributed foraging resources to local pollinators. Fluorescent dye was moved between forbs in all basins, while bi-directional dye dispersal up to 86 m demonstrated basins facilitate functional connectivity for pollinating insects whereby structurally disconnected basins contribute as stepping-stone habitat patches. Finally, in the controlled experiment testing the effect of soil types on plant growth (aboveground biomass) and reproduction (floral units) of eight native forbs, results indicated that infiltration soils should maximise organic content to enhance species richness in bioretention basins, albeit without compromising system performance. Despite low replication in the field study, we demonstrate bioretention basins can support urban biodiversity conservation by providing valuable foraging habitat and functional connectivity for pollinators while requiring minimal management.

Fecal metabarcoding of the endangered Pacific pocket mouse (Perognathus longimembris pacificus) reveals a diverse and forb rich diet that reflects local habitat availability.

Information on diet breadth and preference can assist in understanding links between food resources and population growth and inform habitat restoration for rare herbivores. We assessed the diet of the endangered Pacific pocket mouse using metabarcoding of fecal samples and compared it to plant community composition in long-term study plots in two populations on Marine Corps Base Camp Pendleton, San Diego County, CA. Fecal samples (n = 221) were collected between spring 2016 and fall 2017 during monthly live-trap surveys. Concurrently, percent cover and plant phenology were measured in plots centered on trap locations. Fecal samples were sequenced with paired-end reads of the internal transcribed spacer 2 region of the nuclear ribosomal gene, and the resulting amplicons were matched to a regionally specific database. Seventy-three plant taxa were detected, which were mostly forbs and perennial herbs (70-90%). Diet composition differed between populations, years, seasons, and plots. Overall, diet and local habitat composition in plots were significantly correlated. However, we detected some differences in above-ground seed availability and proportion in fecal samples that indicate diet preferences for some forbs, perennial herbs, and native bunch grasses over perennial shrubs and non-native grasses. This is the first study of PPM to pair plant phenology surveys with diet metabarcoding to estimate resource selection, and results suggest that managing habitat for diverse native forb communities and reducing non-native grass cover may be beneficial for this critically endangered species.

Gradient Analysis and Classification of Tall Forb Communities in the Bridger-Teton National Forest, United States

Tall forb−mixed upland−herb communities are exemplified by high plant diversity and a profusion of luxuriant wildflowers throughout subalpine mountain parklands of the interior western United States. These unique and ecologically important communities remain largely unclassified in terms of their biological and physical attributes and ecological responses to management and disturbances. Land managers need respective classifications to evaluate and guide conservation planning and management for tall forb communities where they occur. In this study, 23 sites from four subalpine areas representing reference tall forb plant communities on the Bridger-Teton National Forest were identified and selected for analysis after a sustained cessation of grazing activities. The purpose of the study was to quantitatively examine tall forb community stands and provide a basis for developing a classification system for identifying future ecological sites, which are essential in conservation planning, implementation and management, and monitoring. Seven tall forb cluster groups were identified with unique plant composition and specific environmental gradients (i.e., plant species richness, diversity indices, elevation, average annual precipitation, surficial geology, three-dimensional geomorphic descriptions, soil clay content diversity dynamics, and foliar, ground, and surface cover). Among the seven cluster groups, we identified 31 families, 112 genera, and 158 plant species on the sample sites (61 species representing native indicator reference species, 86 native secondary indicator species, and 10 introduced non-native species). Beta diversity and plant species turnover ranged from 6.7% to 41.9% among the seven cluster groups, indicating discrete differences in plant species assemblages, plant associations, and site dynamics. The seven tall forb clusters are characteristic of specific and unique plant species composition, species diversity, and environmental factors. Therefore, a specialized site approach with respective guidelines is recommended for assessing and conserving discrete tall forb ecological sites and maintaining key dominant native indicator reference species, rangeland health and proper functioning condition, and defined monitoring protocols.

Invasive grass and litter accumulation constrain bee and plant diversity in altered grasslands

Ecologists consider biological invasions one of the primary drivers of global change. Many remaining grasslands in North America have extensive invasions of exotic grass species that have replaced native plant species. In the Northern Great Plains, exotic cool-season grasses Kentucky bluegrass (Poa pratensis) and smooth brome (Bromus inermis), paired with human alterations to the landscape and historical disturbance regimes, have resulted in functionally and structurally altered grassland plant communities. These changes may extend to impact species that rely on these plant communities, such as bees. Bees are ecologically diverse and serve important pollinator roles but are at risk from the loss and change of floral and nesting resources in plant communities. Our objectives were to determine whether Kentucky bluegrass and smooth brome alter the bee and forb species richness in invaded Northern Great Plains grasslands and how litter accumulation, grass cover, the amount of bare ground, and forb species richness interact with bee functional traits. To do this, we surveyed 67 grassland sites from 2017 to 2020 with two bee-sampling methods (268 netting and bee bowl surveys total) and vegetation cover surveys at each site. We collected 20,559 bees from 201 bee species and observed 249 forb and shrub species in vegetation surveys. Bee richness and Shannon diversity were associated with greater forb richness while forb richness was significantly lower with thicker litter depths and higher with a greater coverage of all grasses other than Kentucky bluegrass and smooth brome. Bee trait analyses showed varying relationships with plant community variables. Of these, litter depth and Kentucky bluegrass cover were associated with lower ground-nesting bee abundance while small-bodied bee abundance was positively associated with increasing bare ground. While our results support the close relationship between bee and plant diversity, we also found litter depth, in particular, contributed to the structure of these two communities. Specifically, Kentucky bluegrass and smooth brome are two exotic grass species associated with thatch-forming litter layers, especially under idle management that appear to simplify bee and forb communities. Our results make apparent the importance in maintaining structural and compositional diversity in invaded grasslands to support diverse bee communities.

Does shrub encroachment reduce foraging grass abundance through plant-plant competition in Lesotho mountain rangelands?

Shrub encroachment is understood to be an important problem facing rangeland ecosystems globally. The phenomenon is still poorly understood both in regard to its impacts (e.g., on diversity, productivity, and soil properties) and its causes. We study the impacts and causes of dwarf shrub encroachment in the highlands of Lesotho. There, shrubs have been described as indicators of generalized land degradation and soil erosion. Surprisingly, our findings show that grass abundance is not reduced by shrub abundance, but that forb abundance does decrease with shrub abundance. We suggest that not enough research has been done to examine the role of forbs in livestock diets, nor in assessing its role in plant-plant competition in grass-shrub systems. Equating shrub presence with declines in available forage may be hasty, as according to our results, grasses were not decreased by shrub expansion in this context; however, forbs are critical components of livestock diets. We propose that the role of forbs in this system should be further studied, focusing on the role that high-nutrient or N-fixing forbs could play in returning nutrients to the soil and affecting livestock grazing patterns, both of which could reduce shrub abundances and favor the establishment of a richer forb community.

Community-specific patterns of nitrogen transformations along an elevational gradient in alpine and subalpine ecosystems

AimsThe aim of the study was to investigate N biogeochemistry of four neighboring, high mountain plant communities and to identify main factors which drive variability among them. We hypothesized that the vegetation types differ in terms of N transformations, and that spatial differentiation of the communities and dominant growth form can reflect an existence of several N-environments along an elevational gradient.MethodsPlant and soil N characteristics were studied in four vegetation types: heathland, scrub, sward and tall forb. Leaf nitrate reductase activity and total N were measured in the dominant species. Soil pH, total C, N, inorganic and dissolved organic N concentrations were measured. The soil net N mineralization rate was examined.ResultsThe DistLM and PERMANOVA analyses revealed that variability among the vegetation types was driven primarily by elevation, soil N–NH4+, soil pH and soil total C. We identified three distinct N-environments along an elevational gradient. The “N-poor alpine” located at the highest altitudes, strongly N-limited and dominated by dwarf-shrub. The "N-mixed subalpine" located in the middle of the gradient and covered by scrub and sward. It was characterized by moderate N turnover rate. The "N-rich subalpine" occurred at lowest locations and was covered by subalpine tall forb community. It exhibited the highest dynamics of N transformations and was rich in inorganic N.ConclusionThree main N-environments were identified: N-poor alpine, N-mixed subalpine, N-rich subalpine. Variability among the vegetation types was driven primarily by elevation, soil N–NH4+, soil pH and soil total C.

Forb composition gradients and intra-annual variation in a threatened Pacific Northwest Bunchgrass Prairie.

Grasslands are among the most threatened and least protected terrestrial biome. Grassland forbs: (1) account for most of the floral diversity; (2) are not well studied because they have been overshadowed by grass‐centered research; and (3) have been a major source for biodiversity loss. The Pacific Northwest Bunchgrass Prairie (PNB) of North America is one of the most endangered grasslands on earth. Knowledge of vegetation community dynamics in the PNB is based primarily on bunchgrasses. There is a paucity of information related to the PNB's diverse native perennial forbs (hereafter “forbs”). Consequently, PNB forb community patterns and dynamics are largely unknown. We describe forb community structure and its relationship to environmental factors and phenology. We sampled 29 plots in the Starkey Experimental Forest and Range, northeastern Oregon, at three different times during 2016 (April; May; July). Nonmetric multidimensional scaling (NMS) indicated that the dominant gradient in forb composition was related (R 2 = 0.66) to slope and soil P and K, contrasting flat, poorly drained soils (scabflats) at one end with steep, well‐drained soils at the other end. The secondary gradient (R 2 = 0.16) contrasted deeper, finer textured soils at one end with shallow, rocky soils at the other. Forb richness decreased by ~40% from April to July. NMS and Indicator Species Analysis (ISA) showed that most forbs had affinities toward spring. Ubiquitous forbs (e.g., Triteleia grandiflora, Camassia quamash) were sparse to absent by July. Contradictory to general descriptions of the PNB, forb cover and richness in drought‐prone sites were comparable to mesic sites when spring data were considered. Our findings suggest that PNB grasslands contain diverse forb communities that are structured primarily by water drainage and soil depth. Conventional sampling concomitant with peak grass biomass is insufficient to characterize PNB forb communities, particularly for scabflats and the most drought‐prone soils.

Climate mediates long‐term impacts of rodent exclusion on desert plant communities

AbstractDetermining how climate affects biotic interactions can improve understanding of drivers of context‐dependence and inform predictions of how interactions may influence plants under future climates. In arid environments, the community‐level impacts of seed predators may depend strongly on aridity; yet, long‐term studies documenting impacts of granivores on plant communities over variable climate conditions remain scarce. We evaluated how rodent exclusion interacted with climate to influence grassland and shrubland forb communities and the community‐scale distribution of seed mass over 15 years in the climatically variable northern Chihuahuan Desert. In this dynamic system, two seasonally distinct plant community phases occur annually, one in spring and the other during the summer monsoon. Rodent exclusion significantly altered the community composition of monsoon season plant communities in both grassland and shrubland, but did not affect spring plant composition. Rodents suppressed the abundance of larger‐seeded forb species and promoted smaller‐seeded species. As a consequence, rodent exclusion increased community seed mass (CWM) in monsoon forb communities, most strongly in grassland. The magnitude of impacts of rodents on seed mass varied substantially from year‐to‐year, tracking variation in climate. Specifically, rodent exclusion increased community mean seed mass the most in dry years (grassland) or in years following dry years (shrubland). Rodent exclusion had relatively weak effects on plant species diversity and richness. Our results indicate that climate interacts with the presence of rodents to structure not only the composition but also the traits of desert plant communities.

Evaluating CAP wildflower strips: High‐quality seed mixtures significantly improve plant diversity and related pollen and nectar resources

Abstract Flower strips are a fundamental part of agri‐environment schemes (AESs) introduced by the European Union to counteract the loss of biodiversity and related ecosystem services in agricultural landscapes. Although vegetation composition of the strips is essential for most fauna groups, comprehensive studies analysing vegetation development and influencing factors are rare. From 2017 to 2019, we investigated the vegetation composition of 40 perennial wildflower strips (WFSs) implemented in 2015 or 2016, and 20 cereal fields without WFS across Saxony‐Anhalt, Germany. We analysed environmental factors on plot (cover of grasses, shading, soil fertility) and four landscape‐scale levels (habitat diversity, proportion of WFS and open habitats). The provision of nectar and pollen resources was estimated by the newly developed Pollinator Feeding Index (PFI). All strips had been implemented by farmers as AES with species‐rich seed mixtures comprising 30 native forbs. In all study years, forb species richness, cover and related nectar and pollen supply were much higher on WFSs than on controls, confirming the effectiveness of this AES. Although sown native forbs contributed the most to the high PFI values, spontaneously established forbs expanded the total range of species considerably, especially in winter and spring. While sown forb communities remained similar over time, spontaneous forbs showed a higher species turnover. Altogether, shading and grass cover had the greatest negative effect on the performance of the sown forbs. Landscape variables had only minor effects and were inconsistent in their importance across scale levels and years. Synthesis and applications. Successfully established perennial wildflower strips (WFSs) sown with species‐rich native seed mixtures provided a forb‐rich and diverse vegetation throughout the AES funding period of 5 years. By supplying feeding resources for pollinators under various landscape situations, WFSs have significant potential to promote farmland biodiversity and related ecosystem services. We recommend the mandatory use of species‐rich wildflower mixtures for perennial flower strips and to avoid their creation in heavily shaded field edges. Advisory services for farmers are necessary to prevent failures in WFS implementation and management and to improve their ecological effectiveness.

Timing of prescribed burns impacts plant diversity but not investment in pollinator recruitment in a tallgrass prairie

AbstractPrescribed burns replicate the historic fires that played a key role in maintaining prairies. Spring‐applied burns are commonly employed for grazing and brush control and, therefore, much is known about their effects. However, prairie plants may be sensitive to the historically variable timing of burns and thus differentially respond to when prescribed burns are applied, an aspect that remains poorly understood. We performed three experimental seasonal burn treatments (summer, fall, or spring) in tallgrass prairie and examined (1) the response of the flowering forb community in terms of density and diversity, and (2) how individual milkweed plants (Asclepias spp.) invested in nectar to recruit pollinators. We found that burn timing did not affect flowering forb density but did impact flowering forb diversity: It was lowest following spring burns, whereas summer‐ and fall‐burned plots were more diverse. Nectar sucrose concentrations in milkweeds, however, were not affected by the timing of burns but rather seemed robust in their investment to recruit pollinators. Therefore, while individual plant investment strategies may be more sensitive to other factors, the timing of prescribed burns seems important in promoting flowering forb diversity, which could have important downstream consequences on the diversity of pollinators and other animal communities.

Interannual climate variability mediates changes in carbon and nitrogen pools caused by annual grass invasion in a semiarid shrubland.

Exotic plant invasions alter ecosystem properties and threaten ecosystem functions globally. Interannual climate variability (ICV) influences both plant community composition (PCC) and soil properties, and interactions between ICV and PCC may influence nitrogen (N) and carbon (C) pools. We asked how ICV and non‐native annual grass invasion covary to influence soil and plant N and C in a semiarid shrubland undergoing widespread ecosystem transformation due to invasions and altered fire regimes. We sampled four progressive stages of annual grass invasion at 20 sites across a large (25,000 km2) landscape for plant community composition, plant tissue N and C, and soil total N and C in 2013 and 2016, which followed 2 years of dry and wet conditions, respectively. Multivariate analyses and ANOVAs showed that in invasion stages where native shrub and perennial grass and forb communities were replaced by annual grass‐dominated communities, the ecosystem lost more soil N and C in wet years. Path analysis showed that high water availability led to higher herbaceous cover in all invasion stages. In stages with native shrubs and perennial grasses, higher perennial grass cover was associated with increased soil C and N, while in annual‐dominated stages, higher annual grass cover was associated with losses of soil C and N. Also, soil total C and C:N ratios were more homogeneous in annual‐dominated invasion stages as indicated by within‐site standard deviations. Loss of native shrubs and perennial grasses and forbs coupled with annual grass invasion may lead to long‐term declines in soil N and C and hamper restoration efforts. Restoration strategies that use innovative techniques and novel species to address increasing temperatures and ICV and emphasize maintaining plant community structure—shrubs, grasses, and forbs—will allow sagebrush ecosystems to maintain C sequestration, soil fertility, and soil heterogeneity.

Forb community response to prescribed fire, livestock grazing, and an invasive annual grass in the Pacific Northwest Bunchgrass Prairie

AbstractQuestionsGrassland degradation due to agriculture, changing fire regimes, and invasive species negatively affects forb communities. Conserving forbs and the services they provide requires a better understanding of their responses to interacting disturbances. Although fire and livestock grazing are important disturbances, their effect on forb communities in the Pacific Northwest Bunchgrass Prairies is not fully understood. Our objectives were to: (a) determine how prescribed fire and livestock grazing influence forb community composition, cover, species richness, and diversity over a 10‐year span; (b) identify indicator species for each treatment; and (c) quantify forb responses to increasing cover of the invasive grass Ventenata dubia.LocationPacific Northwest Bunchgrass Prairie, Oregon, USA.MethodsWe monitored plant responses in a manipulative study established in 2004 with four treatments (prescribed fire, livestock grazing, both fire and grazing, and a control with no fire or grazing). Fall burns occurred in 2006 and 2016.ResultsForb communities changed significantly over 10 years and were influenced more by fire than cattle grazing. Treatments involving fire were more associated with annual forbs and fewer perennial species than treatments not burned. Although forb cover was lower in grazed compared to ungrazed treatments, richness and diversity did not differ among treatments. Several fire‐adapted forb species were associated with burned treatments. Forb cover and richness was negatively correlated with Ventenata dubia cover in 2016 and 2018 when cover of this invasive species reached 20%–37%.ConclusionsWe found fall prescribed burns at a ten‐year return interval affected forb community composition and cover but not richness or diversity. Fire may promote annual and fire‐tolerant perennial forbs, but this relationship may be compromised by Ventenata dubia invasions. This study provides insights into management strategies aimed at conserving forb communities and emphasizes the need for continued monitoring of the Ventenata dubia invasion in this unique prairie.

Rolling pits of Hartmann's mountain zebra (Zebra equus hartmannae) increase vegetation diversity and landscape heterogeneity in the Pre-Namib.

Microsites created by soil‐disturbing animals are important landscape elements in arid environments. In the Pre‐Namib, dust‐bathing behavior of the near‐endemic Hartmann's mountain zebra creates unique rolling pits that persist in the landscape. However, the ecohydrological characteristics and the effects of those microsites on the vegetation and on organisms of higher trophic levels are still unknown. In our study, we characterized the soil grain size composition and infiltration properties of rolling pits and reference sites and recorded vegetation and arthropod assemblages during the rainy season of five consecutive years with different amounts of seasonal rainfall. We further used the excess green vegetation index derived from drone imagery to demonstrate the different green up and wilting of pits and references after a rainfall event. In contrast to the surrounding grassland, rolling pits had finer soil with higher nutrient content, collected runoff, showed a higher infiltration, and kept soil moisture longer. Vegetation in the rolling pits was denser, dominated by annual forbs and remained green for longer periods. The denser vegetation resulted in a slightly higher activity density of herbivorous arthropods, which in turn increased the activity density of omnivorous and predatory arthropods. In times of drought, the rolling pits could act as safe sites and refuges for forbs and arthropods. With their rolling pits, Hartmann's mountain zebras act as ecosystem engineers, contributing to the diversity of forb communities and heterogeneity of the landscape in the Pre‐Namib.

Contrasting effects of soil microbial interactions on growth-defence relationships between early- and mid-successional plant communities.

Summary Plants allocate resources to processes related to growth and enemy defence. Simultaneously, they interact with complex soil microbiomes that also affect plant performance. While the influence of individual microbial groups on single plants is increasingly studied, effects of microbial interactions on growth, defence and growth–defence relationships remain unknown, especially at the plant community level.We investigated how three microbial groups (bacteria, fungi, protists), alone and in full‐factorial combinations, affect plant performance and potential growth–defence relationships by measuring phenolics composition in early‐ and mid‐successional grass and forb communities in a glasshouse experiment.Microbial groups did not affect plant growth and only fungi increased defence compounds in early‐ and mid‐successional forbs, while grasses were not affected. Shoot biomass–defence relationships were negatively correlated in most microbial treatments in early‐successional forbs, but positively in several microbial treatments in mid‐successional forbs. The growth–defence relationship was generally negative in early‐successional but not in mid‐successional grasses. The presence of different microbiomes commonly removed the observed growth–defence relationships.We conclude that soil microorganisms and their interactions can shift growth–defence relationships differentially for plant functional groups and the relationships vary between successional stages. Microbial interaction‐induced growth–defence shifts might therefore underlie distinct plant strategies and fitness.

Effects of plant diversity on semiarid grassland stability depends on functional group composition and dynamics under N and P addition

Exogenous fertilization could efficiently improve grassland productivity and promote grassland restoration. Increasing fertilization may profoundly affect community stability, whereas the underlying compensatory dynamics among functional groups in regulating grassland stability remain unclear. Three different grasslands, annuals forb (AF) community, perennial grass (PG) community and perennial forb (PF) community, on semiarid Loess Plateau were selected. We designed a 3-year split-plot experiment (main-plot: 0, 25, 50, and 100 kg N ha−1 yr−1; subplot: 0, 20, 40 and 80 kg P2O5 ha−1 yr−1) to explore how N and P addition affects community stability and its relationship with species richness, species asynchrony and functional group stability. Temporal stability differed largely between functional groups under N and P addition, perennial forbs or grasses had higher stability than perennial legumes or annuals and biennials. Decreased stability of PG and PF communities was primarily due to reduced species asynchrony under N addition alone, while it attributed to increased dominance of perennial legumes after P addition alone. 50 and 100 kg N ha−1 yr−1 combined with P addition significantly increased dominance of annuals and biennials, but decreased stability of annuals and biennials, which caused significant declines in stability of the three communities. Significant species richness decline induced by N and P addition only occurred in AF community, which suppressed AF community stability through reducing species asynchrony. AF community stability was regulated by additively negative effect of diversity decline and decreased annuals and biennials stability. Whereas, in PG and PF communities, nutrient-induced changes of functional groups stability were the main driver of community stability rather than diversity. Our study highlights the role of functional group composition and dynamics in regulating the effects of diversity on community stability and rational N and P combined addition was essential for conserving stability of different grasslands on semiarid Loess Plateau.

The Effects of Continuous and Rotational Livestock Grazing on Forb Quality and Quantity: Implications for Pronghorn Habitat Management

Pronghorn (Antilocapra americana) evolved in grasslands with a diet composed of highly nutritious forbs. However, pronghorn habitat throughout North America has been lost to fragmentation and degradation. Additionally, the effects different cattle grazing regimes have on forb biomass, protein, and energy production for pronghorn are not well known in West Texas. We sampled forbs during the growing season in the months of September 2018 and 2019 to assess the effects of different cattle grazing regimes on forbs. We hypothesized rotational grazing would increase the nutritional quality of the forb community and overall forb production, compared to continuous grazing and no grazing. We randomly sampled pastures subject to continuous and rotational grazing, as well as ungrazed exclosures using 100, 96, and 64 1 m2 plots, respectively. We collected all forbs in each plot and analyzed differences in nutritional composition and biomass production using redundancy analysis. We found that the effects of grazing varied by year. In wetter conditions, rotational grazing exhibited higher forb quality and biomass, while exclusion from grazing exhibited these results under drier conditions. The knowledge gained from this study helps resource professionals and landowners understand how cattle grazing affects forbs for pronghorn. This knowledge may be used to improve the suitability of pronghorn habitat through cattle grazing regimes.

Drought tolerant forb flora of a semi-arid protected savanna in the Lowveld of South Africa

Background: Increased frequency and intensity of droughts related to climate change are predicted to induce pressure on herbaceous communities. Considering that forbs contribute significantly to savanna ecosystem resilience, we investigated forb communities of a protected semi-arid savanna during an extensive drought.Objective: We identified drought-tolerant species with their related functional traits.Results: Drought-tolerant forb flora comprised of several plant families and species with overlapping traits, of which the ability to resprout was related to perennials, whereas succulence and prostrate growth form were typical annual forb dominance traits.Conclusion: Results highlight the functional importance of forbs and their resilience to drought events in protected areas.