Floral Density Research Articles

Variation in flower morphology associated with higher bee diversity in urban green spaces.

Urbanization is a leading threat to biodiversity, but scientifically informed management of urban ecosystems can mitigate negative impacts. For wild bees, which are declining worldwide, careful consideration of flower choice in public and private green spaces could help preserve their diversity. While floral density and species richness are both linked to wild bee diversity, the mechanisms underlying these relationships are not fully understood. Here, we tested two hypotheses relating the influence of floral trait composition to bee species richness, which we have termed the within-trait diversity and optimal floral trait hypotheses. Specifically, we assessed whether variation in bee richness relates to variation in the weighted variance (trait diversity) and mean (optimal trait) of floral traits observed in urban green spaces across the city of Montreal, Canada. Our analyses focused on two floral traits relating to pollinator feeding success: nectar sugar concentration and corolla length. After accounting for variation in floral density among sites, bee richness was positively related to community-weighted variance in corolla length, supporting the within-trait diversity hypothesis. These findings suggest that management practices that increase the diversity of flower morphologies in urban green spaces can promote the persistence of wild bee communities in cities.

Variation in insect community structure between natural and constructed tidal marshes

Abstract Insects perform important ecological roles that influence ecosystem functions, including primary production and nutrient cycling. Likewise, wetland ecosystems perform important functions and provide numerous services, yet they are highly vulnerable to loss. Wetland restoration and construction can provide habitat for insects and other organisms and recover ecosystem functions. While the community structure of plants and non‐insect macroinvertebrates in restored and constructed wetlands often fails to recover to comparable levels of reference wetlands, less is known about the recovery of insect communities in restored wetlands. We aimed to determine if differences in biological structure (i.e., plant biomass and soil organic matter) between one reference and two constructed Juncus roemerianus‐dominated tidal marshes extend to their respective insect communities. We classified insect communities into taxonomic families and functional feeding groups in one reference marsh and two constructed marshes in Alabama, USA. Sampling methods included replicated pan trapping, line‐transect netting, floral observations and floral clippings. We also conducted light trapping at one site per marsh. All insect taxa and functional groups were identified monthly from April to October 2021 and analysed for taxon richness, abundance and H′ diversity. Floral density and herbivory scars on J. roemerianus shoots were also measured during flowering and peak growing seasons, respectively. While insect abundance and taxon richness were similar among sites, the reference marsh generally supported a more diverse insect community than the constructed marshes, although nocturnal flying insects were less diverse. Additionally, temporal shifts in community composition, based on relative abundances of insect taxa and functional feeding groups, differed among marshes, likely reflecting differences in habitats in the surrounding landscapes of each site. By comparing structural differences (i.e., taxonomic and functional) of insect communities in reference and constructed marshes, we can further understand the community composition of an understudied group of organisms, thereby informing restoration strategies to recover habitat and support the health of tidal marshes.

Effects of short- and long-term experimental warming on plant–pollinator interactions and floral rewards in the Low Arctic

Plant phenological and growth responses to experimental warming are widely documented, but less is known about warming effects on plant–pollinator interactions. We investigated the effects of short- and long-term passive warming on flowering phenology, insect visitation, fruit production, and floral rewards in the Low Arctic in northern Alaska. To better understand the role of insect visitors in plant reproductive success, we quantified pollen loads on floral visitors and tested for pollen limitation in four species. Long-term warming advanced flowering onset in evergreen shrubs and forbs. Warming, in general, increased the duration of flowering for forbs, evergreen shrubs, and deciduous shrubs. Considering all growth forms together, long-term warming increased floral density. This pattern was primarily driven by deciduous and evergreen shrubs. Dipterans accounted for more visits than Hymenopterans, although Hymenopterans had higher pollen loads. Insect exclusion and warming decreased fruit set in the forb, Bistorta officinalis Delarbre. Nectar volume in the deciduous shrub, Vaccinium uliginosum, was higher in the warmed plots than the control, but nectar quality did not differ. Advanced flowering onset, longer flowering duration, and increased flower density and nectar volume may have important implications for the pollinator community, warranting further research on long-term warming effects on tundra ecosystems.

Dispersal mediates trophic interactions and habitat connectivity to alter metacommunity composition.

Dispersal contributes vitally to metacommunity structure. However, interactions between dispersal and other key processes have rarely been explored, particularly in the context of multitrophic metacommunities. We investigated such a metacommunity in naturally fragmented habitats populated by butterfly species (whose dispersal capacities were previously assessed), flowering plants, and butterfly predators. Using data on butterfly species abundance, floral abundance, and predation (on experimentally placed clay butterfly models), we asked how dispersal ability mediates interactions with predators, mutualists, and the landscape matrix. In contrast to expectations, high densities of strong dispersers were found in more isolated sites and sites with low floral resource density, while intermediate dispersers maintained similar densities across isolation and floral gradients, and higher densities of poor dispersers were found in more connected sites and sites with higher floral density. These findings raise questions about how strong dispersers experience the landscape matrix and the quality of isolated and low-resource sites. Strong dispersers were able to escape habitat patches with high predation, while intermediate dispersers maintained similar densities along a predation gradient, and poor dispersers occurred at high densities in these patches, exposing them to interactions with predators. This work demonstrates that species that vary in dispersal capacities interact differently with predators and mutualist partners in a landscape context, shaping metacommunity composition.

In search of enhanced material: Kalanchoe ×toelkenii (Crassulaceae subfam. Kalanchooideae), a new South African nothospecies derived from Kalanchoe ×gunniae × K. sexangularis

Considerable investment in the breeding of enhanced material of Kalanchoe (Crassulaceae subfam. Kalanchooideae) has resulted in several new nothospecies introduced from South Africa, all of which provide additional horticultural possibilities, especially under irrigation-limited conditions. Kalanchoe ×toelkenii, derived from K. ×gunniae back-crossed with K. sexangularis, is described here as a further large-growing nothospecies with improved inflorescence spread and floral density.

Social but not solitary bee abundance tracks pollen protein accumulation in forest canopy gaps

Abstract Forest restoration projects that create canopy gaps can promote floral diversity and may provide reservoirs for bee–flower interactions. However, periods of bee activity must match availability of floral nutrition for bees to benefit from these effects. We model variation in canopy gap size, floral density, pollen protein and bee and floral traits to test the hypothesis that patterns of floral visitation in bee–flower interactions are predicted by patch structure, variation in bee life histories and floral phenotypes. Canopy gap size did not predict overlap of foraging bee abundances and floral protein, but bee life‐history traits did. Foraging activity of large ground‐nesting bees matched accumulation of protein density, whereas activity of small cavity‐nesting bees and kleptoparasitic species preceded peak protein density. Floral visual traits predicted visitation rates, with more interactions for taller species with large floral displays. Both native and invasive species have high nutritional value for bees in canopy gaps and can support frequent and rich interactions. Landscapes with both weedy and native floral species may have higher phenological diversity and provide more foraging opportunities for early‐season bees. We conclude that canopy gap creation is likely to have similar impacts on bee–flower interactions regardless of gap size, but activity periods of larger bees are more aligned with pollen protein density than activity of small bees, and floral visual displays are decoupled from pollen protein content.

Floral resources encourage colonisation and use of green roofs by invertebrates

Green roof retrofits offer a promising avenue to increase greenspace and thus biodiversity in the city. The successful colonisation and establishment of plants and animals on green roofs is limited by the location and context of the green roof. Here we use a before, after, control, impact (BACI) design to monitor the colonisation of a new retrofit roof in Melbourne CBD. We find that colonisation for some taxa occurs rapidly, with honeybees (Apis mellifera) arriving four days after flowers had been planted. Other insect taxa, such as native bees, did not colonise the impact roof but were present on the green roof reference site, which was lower in height and planted with native plants. Invertebrate abundance increased for all sites after the retrofit was built, however this sampling period was in late spring when more insects are expected to be active. Bird richness and abundance didn’t change in response to roof greening, but invertebrate richness was significantly higher on reference sites and increased after the green roof retrofit was built for the impact site. There was an apparent ‘spill over’ effect onto the nearby green roof control, which also increased in invertebrate diversity. Overall, invertebrate composition across roof types was driven by floral density. Floral density and richness increased on the impact roof as vegetation matured, subsequently correlating with higher abundance and richness of invertebrates. We use these findings to discuss colonisation of green roofs and argue for strategic placement of new green roof retrofits to maximise their biodiversity potential.

Competition regulates mango fruiting above a floral density threshold

Mango flowering is interannually variable and temperature dependent. Flowering intensity declines with increasing pre-flowering temperatures associated with global warming, potentially limiting yields. Additionally, floral density that does not contribute to greater yield represents an unnecessary drain on plant resources such as nutrients, water, and carbohydrates. This can lead to reduced fruit bearing capacity in later stages of cropping or contribute to interannual yield variation.The objective of this work was to identify the floral density compensation point (FDCP), above which additional flowering becomes redundant, and below which surplus carbohydrates are partitioned to existing flowers, fruit, vegetative growth, or stored. Over two growing seasons, the number of inflorescences on 32 Calypso® mango trees in Dimbulah, Australia were thinned by up to 95%, resulting in floral densities between 0.09 and 4.14 inflorescences per trunk cross sectional area (cm2). Fruit yield, number, composition, vegetative growth, and starch concentration in terminal growth units were measured for each of the trees.Calypso® mango trees have excess floral density, beyond the maximum fruit biomass the tree can support to harvest. Below the FDCP, the tree is unable to compensate for low numbers of inflorescences, and floral density was strongly positively correlated with fruit number and yield, and strongly negatively correlated with fruit per panicle and total soluble solids concentration of ripe fruit. Above the FDCP fruit yield, number and total soluble solids concentration were only weakly related to floral density as they appear limited by carbohydrate availability rather than flowering. Fruit weight, vegetative regrowth of fruiting and non-fruiting terminals, and the starch concentration in terminal growth units were less dependent upon the FDCP and changed continuously across the floral densities evaluated. This information will be valuable for managing mango flowering under current and future climates.

Pollen limitation and context‐dependent alleviating mechanisms in a co‐flowering alpine grassland community

The consequences of community metrics (e.g. co‐flowering diversity and floral density) and plant traits (e.g. pollinator dependency and trait similarity) on pollen limitation (PL) may depend on pollinator‐mediated competitive or facilitative interactions among plants in co‐flowering communities, which could vary with community contexts (i.e. different altitude communities) and under human disturbances (e.g. livestock grazing). However, the mechanisms to alleviate PL under different contexts, considering pollinator‐mediated interactions among neighboring plants are unclear. We investigated PL under grazing versus ungrazing conditions in low versus high altitude alpine meadows on the Tibetan Plateau to uncover the underlying mechanisms mediating PL associated with livestock grazing. We found that PL is prevalent in alpine grasslands, irrespective of community contexts. Grazing exclusion decreased PL in the two sites but in different ways. At the high‐altitude site, PL was reduced by the exclusion of grazers through increased trait similarity (suggesting facilitation). While PL was reduced by decreased trait similarity (suggesting competition avoidance) under grazing exclusion at the low‐altitude site. Our results provide a mechanistic understanding of PL in co‐flowering alpine grassland communities under distinct human disturbances at different altitudes, emphasizing the role of pollinator‐mediated interactions among plants on plant reproductive success.

Native and introduced pollinators vary in their seasonal floral resource visitation and selection between native and exotic plant species

Abstract Anthropogenic pressures on native ecosystems have resulted in numerous functional and compositional changes, creating novel ecosystems with new interactions between native and exotic species. How native species utilize these resources is crucial for their management in altered landscapes and the promotion of their essential ecosystem services. We compared seasonal floral selection between European honey bees and their most phylogenetically similar native component in our study region, bumble bees, in North American grasslands with high densities of exotic plant species. Additionally, we determined whether floral species richness, total flowering density, native floral density or exotic floral density best explained the abundance of both groups. Selection analyses revealed that honey bees and native bumble bees differed in selection between native and non‐native floral resource availability, with any significant selection of honey bees being for exotic plants while native bumble bees selected for native plants. Native forb presence and floral richness best explained the variation in bumble bee abundance, while honey bee abundance was associated with flowering densities in the early and mid‐seasons and floral richness in both the early and late seasons. Despite their generalist diets, we emphasize the importance of native floral availability for bumble bee foraging in novel grassland landscapes and the importance of exotic plants to support honey bee production. Synthesis and applications. Our results indicate that pollinator forage management should differ for non‐native and native species, despite morphological and life‐history similarities. However, greater floral diversity provides a common management focus that can benefit honey bees and bumble bees in particular seasonal periods. Our results suggest that management actions promoting resource diversity can benefit functionally different species. In grasslands, implementing disturbance processes that can favour floral expression (e.g. fire; grazing) can support bumble bees of conservation concern and agriculturally important bees simultaneously.

Differences in individual flowering time change pollen limitation and seed set in three montane wildflowers.

Changes to flowering time caused by climate change could affects plant fecundity, but studies that compare the individual-level responses of phenologically distinct, co-occurring species are lacking. We assessed how variation in floral phenology affects the fecundity of individuals from three montane species with different seasonal flowering times, including in snowmelt acceleration treatments to increase variability in phenology. We collected floral phenology and seed set data for individuals of three montane plant species (Mertensia fusiformis, Delphinium nuttallianum, Potentilla pulcherrima). To examine the drivers of seed set, we measured conspecific floral density and conducted pollen limitation experiments to isolate pollination function. We advanced the phenology of plant communities in a controlled large-scale snowmelt acceleration experiment. Differences in individual phenology relative to the rest of the population affected fecundity in our focal species, but effects were species-specific. For our early-season species, individuals that bloomed later than the population peak bloom had increased fecundity, while for our midseason species, simply blooming before or after the population peak increased individual fecundity. For our late-season species, blooming earlier than the population peak increased fecundity. The early and midseason species were pollen-limited, and conspecific density affected seed set only for our early-season species. Our study shows that variation in individual phenology affects fecundity in three phenologically distinct montane species, and that pollen limitation may be more influential than conspecific density. Our results suggest that individual-level changes in phenology are important to consider for understanding plant reproductive success.

Enhanced urban roadside vegetation increases pollinator abundance whereas landscape characteristics drive pollination

Roads cause pollution, habitat degradation and fragmentation, while recent studies report that roadside vegetation can benefit plant and insect diversity. However, the factors that drive effects of roadside vegetation on pollinator abundance and pollination need further attention. Our main interest in this study was to evaluate urban roadside enhancement by identifying direct and indirect effects of local resource availability and landscape characteristics on pollinator abundance and quality of pollination, by using functionally different phytometer plants. Thus, we established 34 species-rich wildflower patches along urban roads, and monitored flowering species and floral density at the local scale. At the landscape scale we measured the amount of impervious surface within a radius of 500 m around the wildflower patches, as well as edge density of all major land-use types, and distance to the city center. As control, we used 34 patches with existing species-poor roadside green. The abundance of pollinators, i.e., honeybees, wild bees, and hoverflies, was sampled with colored pan traps. Pollination was monitored based on fruit number and weight of three phytometer species, i.e., Fragaria × ananassa, Ranunculus acris, and Trifolium pratense, that differ in flower morphology and color, and attract different pollinators. Pollinator abundance was positively related to local richness of flowering plants and floral density. At the landscape scale, pollinator abundance was positively related to the proportion of impervious surface but negatively to edge density. Phytometer-specific effects on pollination were moderated by landscape characteristics: Fruit mass of F. x. ananassa was highest in the inner city, fruit number of R. acris was lower in areas with high edge density, whereas in T. pratense fruit number increased with edge density, and was negatively related with the proportion of impervious surface. There were no indirect effects of local and landscape factors via pollinator abundance on pollination. The study of the three phytometer species revealed that roadside enhancement can directly support fruit production in wild plants and crops in cities. Thereby, different landscape characteristics influenced the quality of fruit set, which also depended on individual plant reproductive adaptations. This stresses the importance of using a set of complementary phytometer species in pollination experiments, especially to gain insights into ecosystem functioning at coarser spatial scales.

Different influences of phylogenetically conserved and independent floral traits on plant functional specialization and pollination network structure.

Plant specialization and pollination network structure play important roles in community assembly. Floral traits can mediate plant-pollinator interactions and thus have important impacts on nestedness and modularity of pollination network. When such traits are phylogenetically conserved, therefore, phylogeny and traits should predict network structure to similar degrees. Moreover, conserved network structures were also found attributed to pollination syndrome or pollination system. However, we still know little about the relation between pollination syndrome and pollination network, especially under a phylogenetic framework. Herein, we established a phylogenetic framework including five floral traits (flower density, floral size, floral shape, floral symmetry, and floral color) and five species-level metrics (species strength, weighted closeness, specialization d', nestedness contribution, and modularity contribution) to test how floral traits could directly or indirectly influence species' specialization and network structure in central China. Phylogenetic signals were found in all floral traits except flower density. Structural equation model and phylogenetic structural equation model results showed that both floral size and floral density affected plant specialization and its contribution to network modularity indirectly. However, compared with phylogenetic independent flower density, phylogenetic conserved floral size had much more complexed influences, having a direct influence both on species' specialization and on modularity contribution. In this nested and modular network, abundant species with larger flowers tend to be more central and had larger values of z. Floral shape, symmetry, and color could act as co-flowering filters in pollination sharing and help to shape network modularity. Our results emphasize that phylogenetically conserved traits partially represent pollination syndrome and are important drivers for modular structure of local pollination network. This study may improve the understanding how the evolutionary history and ecological process drive local network structure and dynamics.

Habitat quality influences pollinator pathogen prevalence through both habitat-disease and biodiversity-disease pathways.

The dilution effect hypothesis posits that increasing biodiversity reduces infectious disease transmission. Here, we propose that habitat quality might modulate this negative biodiversity-disease relationship. Habitat may influence pathogen prevalence directly by affecting host traits like nutrition and immune response (we coined the term "habitat-disease relationship" to describe this phenomenon) or indirectly by changing host biodiversity (biodiversity-disease relationship). We used a path model to test the relative strength of links between habitat, biodiversity, and pathogen prevalence in a pollinator-virus system. High-quality habitat metrics were directly associated with viral prevalence, providing evidence for a habitat-disease relationship. However, the strength and direction of specific habitat effects on viral prevalence varied based on the characteristics of the habitat, host, and pathogen. In general, more natural area and richness of land-cover types were directly associated with increased viral prevalence, whereas greater floral density was associated with reduced viral prevalence. More natural habitat was also indirectly associated with reduced prevalence of two key viruses (black queen cell virus and deformed wing virus) via increased pollinator species richness, providing evidence for a habitat-mediated dilution effect on viral prevalence. Biodiversity-disease relationships varied across viruses, with the prevalence of sacbrood virus not being associated with any habitat quality or pollinator community metrics. Across all viruses and hosts, habitat-disease and biodiversity-disease paths had effects of similar magnitude on viral prevalence. Therefore, habitat quality is a key driver of variation in pathogen prevalence among communities via both direct habitat-disease and indirect biodiversity-disease pathways, though the specific patterns varied among different viruses and host species. Critically, habitat-disease relationships could either contribute to or obscure dilution effects in natural systems depending on the relative strength and direction of the habitat-disease and biodiversity-disease pathways in that host-pathogen system. Therefore, habitat may be an important driver in the complex interactions between hosts and pathogens.

Individual flowering phenology shapes plant-pollinator interactions across ecological scales affecting plant reproduction.

The balance of pollination competition and facilitation among co-flowering plants and abiotic resource availability can modify plant species and individual reproduction. Floral resource succession and spatial heterogeneity modulate plant-pollinator interactions across ecological scales (individual plant, local assemblage, and interaction network of agroecological infrastructure across the farm). Intraspecific variation in flowering phenology can modulate the precise level of spatio-temporal heterogeneity in floral resources, pollen donor density, and pollinator interactions that a plant individual is exposed to, thereby affecting reproduction. We tested how abiotic resources and multi-scale plant-pollinator interactions affected individual plant seed set modulated by intraspecific variation in flowering phenology and spatio-temporal floral heterogeneity arising from agroecological infrastructure. We transplanted two focal insect-pollinated plant species (Cyanus segetum and Centaurea jacea, n=288) into agroecological infrastructure (10 sown wildflower and six legume-grass strips) across a farm-scale experiment (125 ha). We applied an individual-based phenologically explicit approach to match precisely the flowering period of plant individuals to the concomitant level of spatio-temporal heterogeneity in plant-pollinator interactions, potential pollen donors, floral resources, and abiotic conditions (temperature, water, and nitrogen). Individual plant attractiveness, assemblage floral density, and conspecific pollen donor density (C. jacea) improved seed set. Network linkage density increased focal species seed set and modified the effect of local assemblage richness and abundance on C. segetum. Mutual dependence on pollinators in networks increased C. segetum seed set, while C. jacea seed set was greatest where both specialization on pollinators and mutual dependence was high. Abiotic conditions were of little or no importance to seed set. Intra- and interspecific plant-pollinator interactions respond to spatio-temporal heterogeneity arising from agroecological management affecting wild plant species reproduction. The interplay of pollinator interactions within and between ecological scales affecting seed set implies a co-occurrence of pollinator-mediated facilitative and competitive interactions among plant species and individuals.

Direct and indirect interactions between shrubs and the flowering annual community in an arid ecosystem

Shrubs commonly shape the plant community in arid ecosystems such as deserts. Plant interactions between shrubs and the associated species can be both negative and positive, and direct and indirect. The importance of shrub effects on reproduction is also a key component of facilitation studies in deserts. Here, we tested the hypothesis that shrubs facilitate understory plant community composition and reproduction through both direct and indirect interactions mediated by the associated plant neighbourhood. Using the shrub species Larrea tridentata, we tested the effects of facilitation on understory plant density, floral density, and species richness in the Mojave Desert, California. We found that shrubs decreased the net community-wide plant assembly measures relative to open microsites including total density and species richness at the site tested. There was also evidence that shrubs directly decreased plant fitness by reducing floral density, but this effect depended on the species. The net density and diversity of the annual plant community also influenced plant and floral density under shrubs suggesting significant indirect effects between shrubs and all abundant annual plant species. While both direct and indirect interactions between shrubs and the annual plant community were species-specific, the effects of these interactions had greater impact on plant density than floral density measures. Annual plant density and to a lesser extent floral density are thus driven by both direct and indirect interactions with shrubs.

The selective advantage of mast flowering in Veratrum album subsp. oxysepalum: Implications of the predator satiation hypothesis.

Synchronous, highly variable flower or seed production among years within a population (i.e., masting) has been reported in numerous perennial plants. Although masting provides ecological advantages such as enhancing pollination efficiency and/or escape from predator attack, little is known about the degree of these advantages and variations in masting behavior among populations of conspecific plants. We determined flowering ramet density and reproductive success (fruit-set success and herbivorous damage) of a perennial herb, Veratrum album subsp. oxysepalum, across six lowland and six alpine populations in northern Japan during 2-3 years. We then analyzed the relationship between floral density and reproductive success to assess the ecological significance of mast flowering. Flowering intervals of individual plants were estimated by counting annual scars on rhizomes. Most populations had mast flowering, but the intervals between flowering for individual plants were shorter in the alpine populations than in the lowland populations. Floral damage by stem borers (dipteran larvae) and seed predation by lepidopteran larvae were intense in the lowland populations. Seed production of individual ramets increased with higher floral density owing to the effective avoidance of floral-stem damage and seed predation. Although stem borers were absent in the alpine habitat, seed predation decreased with higher floral density also in the alpine populations. Pollination success was independent of floral density in both of the alpine and lowland populations. These results strongly support the predator satiation hypothesis for mast flowering by this species.

Planting time, first‐year mowing, and seed mix design influence ecological outcomes in agroecosystem revegetation projects

The conversion of tallgrass prairie to agriculture has negatively affected provisioning of ecosystem services. Successful restoration of ecosystem services could depend on management decisions applied during revegetation projects. We examined the effects of three management decisions (seed mix design, planting time, and first‐year mowing) on targeted ecosystem services (erosion control, weed resistance, and pollinator resources). We tested three seed mixes of varying diversity and grass‐to‐forb seeding ratios: Economy mix (21 species, 3:1 grass:forb), Pollinator mix (38 species, 1:3), and Diversity mix (71 species, 1:1). We established plots at two planting times (dormant‐season and spring) with or without first‐year mowing. To assess ecosystem services, we measured stem density, canopy cover, and floral density and richness of sown species in the second year after planting. The Economy mix had the highest stem density and cover but lowest floral density and richness. The Pollinator mix had the lowest stem density and cover but highest floral density. The Diversity mix had comparable stem density and cover to the Economy mix and comparable floral density and richness to the Pollinator mix. Mowing accelerated native plant establishment in all seed mixes. Dormant‐season planting improved establishment of spring and fall forbs and favored cool‐season graminoids over warm‐season grasses. All three management decisions influenced ecosystem outcomes, and comparison to a previous study revealed these effects to be robust to variation in site and climatic conditions. We recommend a diverse, balanced seed mix design, first‐year mowing, and dormant‐season planting to improve multifunctionality of conservation projects.

Evaluating the effects of observation period, floral density, and weather conditions on the consistency and accuracy of timed pollinator counts

Insect pollinators are experiencing substantial declines as a result of habitat loss, agricultural intensification, invasive pests, and climate change. To investigate factors causing pollinator declines, evaluate the success of conservation measures, and institute long-term monitoring schemes, it is essential to validate and standardize pollinator sampling techniques. This study investigated how sampling duration, weather conditions, and abundance of floral resources influenced the results of timed pollinator counts by repeatedly sampling the same pollinator assemblage in an Irish meadow. The likelihood of detection of Apis mellifera, Bombus spp, solitary bees, and Syrphidae was strongly associated with the density of floral units or floral cover in the observation plot. Also, even though protocol criteria restricted pollinator counts to the middle of the day and benevolent weather, pollinator counts were strongly influenced by factors such as cloud cover, light levels, wind speed and relative humidity. Increasing the duration of the timed counts from 5-minutes to 30-minutes considerably increased the probability of detection of each pollinator group. Additionally, the perceived diversity of the pollinator assemblage at the meadow was markedly affected by sampling duration and floral abundance. To improve the consistency or comparability of studies using timed pollinator counts, we recommend that criteria are set restricting surveys to narrow ranges of weather conditions and floral density when possible. Additionally, pollinator field investigations or monitoring programs would benefit from a systematic evaluation of how erroneous non-detection of target taxa can be reduced to acceptable levels by modifying sampling duration.

Forgotten forbs: Standard vegetation surveys underrepresent ecologically and culturally important forbs in a threatened grassland ecosystem

AbstractForbs are a culturally and ecologically important yet poorly studied component of the Pacific Northwest Bunchgrass (PNB) ecosystem of western North America. Because many PNB forbs emerge early in the spring and senesce at the onset of summer, typical vegetation surveys, which occur mid‐summer, likely underrepresent forbs. We evaluated how the timing of vegetation sampling affected estimates of perennial forb abundance, richness, and floral density, with a focus on species that are culturally significant to Indigenous people of the region. We sampled 29 plots three times: mid‐summer (July), as well as 7 (May) and 12 (April) weeks prior. Timing had large effects on estimates, with significant declines in forb richness (42%), cover (80%), and floral density (95%) between April and July. The density of Camassia quamash and Lomatium cous, two culturally important species, declined 91% and 96%, respectively, from April to July. Nearly 65% of forbs had documented uses by Plateau Tribes. The consequences of biased estimates are significant and (1) limit our understanding of fundamental ecological processes and interactions; (2) hinder effective conservation and management because we lack information on forb abundance, status, and trends, and (3) result in disproportionately negative impacts to Indigenous communities as many forbs are important for subsistence and ceremonial purposes. Vegetation sampling during the spring months coincident with peak forb abundance, in addition to summer sampling would provide more appropriate data with which to evaluate and characterize PNB vegetation dynamics and improve our understanding, management, and conservation of native forbs.