The influence of deer browsing on the reproductive biology of Canada yew (Taxus canadensis marsh.)

Summary Canada yew (Taxus canadensis) populations currently browsed by white-tailed deer (Odocoileus virginianus) or browsed by deer in the past had significantly lower production of male strobili, female strobili, and seeds than unbrowsed yew populations. Exclosure studies showed that protected yews produced significantly more male and female strobili than unprotected yews, but only after several years of protection. Seed production did not respond as readily to protection from deer perhaps because of reduced pollination levels in browsed yew populations. Previously unbrowsed yews were clipped at different levels of removal of available browse (control (no removal), 25%, 50%, 75%, and 100% removal) to simulate deer browsing. Reduction in male strobilus production was linearly related to clipping intensity in three years of observation. Female strobilus production was significantly reduced only at the 100% level of removal. Intermediate levels of clipping may have even stimulated production of female strobili. Analysis of covariance, with previous year's branch production as the covariate, showed no significant effect of clipping on male strobilus production except in the 100% removal group. Female strobilus production showed no such covariance with branch production. Effects of clipping on seed production could not be reliably assessed in 1984 and 1985 due to low seed production. Seed production in 1986 was significantly reduced only in the 100% removal group. Field observations of deer browsing of Canada yew indicate that 100% levels of removal are typical of natural levels of browsing.     

The influence of deer browsing on the reproductive biology of Canada yew (Taxus canadensis marsh.)

Summary Browsed Canada yew (Taxus canadensis) populations have a higher proportion of males and a lower proportion of monoecious plants than unbrowsed yew populations. The proportion of monoecious plants increases with time following protection from browsing suggesting that deer browsing causes male-biased sex expression in Canada yew. In contrast, results from comparing browsed and unbrowsed populations, exclosure studies, and browse simulation experiments indicate that strobilus ratios and phenotypic gender of browsed yews may be female-biased. In part, these results correspond to the influence of size on sex expression in Canada yew; small yews tend to be male, but if monoecious, have female-biased strobilus ratios. Large yews are monoecious, but have male-biased strobilus ratios. There is, however, no consistent relationship between size and gender in Canada yew, suggesting that in some circumstances, yews shift allocation to female function in response to browsing.     

The evolution of nettle resistance to heavy deer browsing

We examined whether heavy browsing by sika deer, Cervus nippon Temminck, changed morphological characteristics of a Japanese nettle, Urtica thunbergiana Sieb. et Zucc., in Nara Park, where a large population of sika deer has been maintained for more than 1,200 years. Wild nettles of Nara Park exhibited smaller leaf area, 11–223 times more stinging hairs per leaf, and 58–630-times higher stinging hair densities than those of other areas where there was no evidence of sika deer browsing. There were no significant differences in stinging hair length between the areas. Nettles from Nara Park that were cultivated from seeds in a greenhouse retained a larger number and higher density of stinging hairs. In the field, nettles of Nara Park were less frequently browsed by sika deer and showed higher survivorship than nettles that were transplanted from an unbrowsed area into Nara Park. These results indicate that: (1) the U. thunbergiana population of Nara Park has an extremely high stinging hair density compared with those of unbrowsed areas; (2) this characteristic has a genetic basis, and (3) stinging hairs serve as a defensive structure against sika deer, contributing to an increase in survivorship. Thus, we conclude that a U. thunbergiana population in Nara Park, with extremely high stinging hair densities, has evolved through natural selection due to heavy browsing by sika deer.     

Ungulate browsing affects subsequent insect feeding on a shared food plant,bilberry (Vaccinium myrtillus)

Browsing by ungulates may induce plant responses and affect subsequent plant food quality for other animals. Populations of many deer species have increased to unprecedented levels in Europe and North America. In Norway, population densities of red deer (Cervus elaphus) have increased over the past decades, but little is known about how increased deer browsing pressure may change the palatability of key food plants for other taxa in the boreal ecosystem. We conducted a cafeteria experiment to assess if long-term deer-browsing intensity affected the palatability of bilberry (Vaccinium myrtillus) leaves for leaf-eating larvae (mainly Lepidoptera). We found that leaf-eating insect larvae preferred bilberry leaves from the lightly browsed bilberry plants; the larvae consumed twice as much leaf biomass from the lightly browsed plants than from the unbrowsed and moderately browsed ones, and four times more than from highly browsed plants. Larvae never selected leaves from highly browsed plants as their first choice. Our study suggests that browsing-induced changes in the quality of shared food plants may be important in mediating indirect interactions between browsers of widely separated taxa. Whereas low levels of long-term red deer browsing increases the palatability of bilberry leaves for leaf-eating larvae, high browsing pressure reduces food consumption. Whether changes in palatability lead to changes in population densities of leaf-eating larvae remains to be studied, but any such adverse effects could have cascading ecological consequences for insectivorous birds and mammals.     

Effects of competition,herbivory and substrate disturbance on growth and size structure in pin cherry (Prunus pensylvanica L.) seedlings

We examined separate and interactive effects of intraspecific competition, vertebrate browsing and substrate disturbance on the growth and size structure of pin cherry (Prunus pensylvanica L.) in the first two seasons of growth after clearcutting, in a hardwoods forest in New Hampshire, United States. Over the 15-month study period, 97.5% of 1801 individuals survived, and mean plant height increased from 4-fold at high density to 5-fold at low density. Relative height growth was significantly lower at higher plant densities in two of the three growth periods examined. Vertebrate browsers (moose and deer) significantly preferred taller plants. Browsed plants had higher relative height growth following browsing than unbrowsed plants (compensatory growth) at low and intermediate densities. The degree of compensation declined with density and compensation was not significant at the highest density level. At low and intermediate densities, plants browsed early in life regained height dominance through compensatory growth; they failed to regain dominance at high density. Because compensatory growth tended to offset the effects of size-selective browsing, there was no difference in the degree of size inequality between browsed and unbrowsed plots. However, size inequality increased with plant density. Substrate disturbance caused by logging had no significant effects on either relative height growth or size inequality. The slope of the relationship between relative height growth and initial height increased significantly with density and time, and was higher in unbrowsed than in browsed plots, suggesting that competition among plants was size-asymmetric. Despite the preference of browsers for large plants, there was a clear net growth advantage for plants of large initial size, when the effects of competition, browsing and compensatory growth were combined. The interactive effects of density and browsing demonstrate the importance of a multifactorial approach to the analysis of individual plant performance and population structure.     

Long-term impacts of goat browsing on bush-clump dynamics in a semi-arid subtropical savanna

The effects of 16 years of continuous browsing by goats in a South African savanna at stocking rates intended for bush control were compared with plots unbrowsed for the same period of time. Differences in bush-clump density, structure and species composition were recorded. Bush-clump density did not differ between browsed and unbrowsed plots. Within individual bush-clumps, browsing was shown to impact more on structure than species composition, with smaller, shorter bush-clumps, containing fewer species but much greater stem-densities. Although species presence/absence was little affected by browsing, many species showed differences in abundance, growth and location within browsed and unbrowsed bush-clumps. Species reduced in abundance in browsed plots included Cussonia spicata, Ehretia rigida, Grewia occidentalis, Jasminum angulare and Senecio linifolius. Several species showed reduced growth in browsed plots, particularly those located at bush-clump edges. The relatively unpreferred Aloe ferox was a notable exception. Although browsing had little effect on the composition of the main clump founding species, emergents or late arrivals, there were twice as many single plants in browsed plots and emergence of several species was restricted to the middle of bush-clumps. Comparison of our findings with aerial photographic evidence and other literature suggest that browsing alone is unlikely to significantly reduce scrub cover, although it can clearly control further expansion. Combinations of fire and browsing, rather than one factor alone, are considered likely to act fastest and most effectively to significantly reduce or remove scrub cover altogether.     

Ungulate browsing in winter reduces the growth of <Emphasis Type="Italic">Fraxinus</Emphasis> and <Emphasis Type="Italic">Acer</Emphasis> saplings in subsequent unbrowsed years

Browsing by ungulates has become a hotly debated issue in many European mountain forests in the past century. Acer pseudoplatanus L. and Fraxinus excelsior L. are broadleaved tree species that are preferentially browsed by roe deer (Capreolus capreolus) in central Europe. We analyzed growth data from shaded saplings of both tree species to quantify the extent to which height growth after game browsing is reduced in subsequent, unbrowsed years in forest stands. Sixty saplings of F. excelsior and A. pseudoplatanus from forest stands at Albisriederberg (Switzerland) were available to us that had been dissected into pieces that then were split in the middle for counting tree rings and assessing ungulate damage. We fitted the von Bertalanffy growth equation to these height growth data and included a reduction factor for winter browsing. Both tree species showed significantly reduced height growth in unbrowsed years after one to several browsing events in winter, and this effect increased with the number of browsing events. Saplings with a high growth rate showed a higher growth reduction. After winter browsing, height growth of A. pseudoplatanus saplings was less affected in unbrowsed years than that of F. excelsior saplings. We conclude that browsed saplings of these species in forest stands are not able to compensate browsing-induced height loss, but that height differences between browsed and unbrowsed saplings probably increase over time. A comparison between our analysis and the parameters estimated using equations published by Eiberle for predicting age at 130 cm height suggests that our parameter values are rather conservative estimates of the growth reduction effect after winter browsing. Neither F. excelsior nor A. pseudoplatanus show a distinct pattern in browsing-induced growth reduction with respect to soil moisture, nutrient level, and altitude. We thus conclude that our results are likely to be valid for a wide range of forested sites.     

The influence of dominant shrubs,fire, and time since fire on soil seed banks in mixed chaparral

The composition and density of soil seed banks beneath co-occurring Adenostoma fasciculatum and Ceanothus greggii shrubs from three chaparral stands last burned 9, 35 and 85 years before 1986 were investigated. The overall density of seeds in the soil, as estimated by germinations under greenhouse conditions, increased with time since fire (ca. 8000 to 25000/m²). However, this increase was due entirely to the accumulation of A. fasciculatum seed in the soil (ca. 2000 to 21000/m²). In contrast, the density of C. greggii seed was different in each of the three stands, but was not correlated with time since fire: maximum densities were recorded from the 35 year old stand (ca. 2000/m²).A total of 31 taxa germinated and 17 occurred in sufficient numbers to be analyzed statistically. Germinable seed densities of three herb species were not influenced by soil source (beneath A. fasciculatum or C. greggii), time since fire, or the direct effects of a controlled fire treatment. Germinable seed densities of a further nine species were significantly influenced by the elapsed time since stands last burned. The densities of four decreased and five increased. Four of the species that increased in seed density over the three stands were annuals, suggesting that the chaparral sub-canopy habitat is not as unfavorable for annuals as is often assumed. The fire treatment decreased germinable seed densities of four annual species by 40–70%, but increased the germinable seed densities of the shrubs A. fasciculatum and C. greggii, and the annual Phacelia brachyloba. Our results indicate that seeds of A. fasciculatum will increase in the soil bank for at least 85 years after fire in chaparral where it is dominant. In contrast, seed reserves of C. greggii appear to be influenced primarily by site-specific patterns of seed production and by the intensity of post-dispersal seed predation.     

Black bears Ursus americanus are effective seed dispersers,with a little help from their friends

Black bears Ursus americanus are generally considered effective seed dispersal agents for fleshy‐fruited plants because they can consume hundreds of fruits at once and have large home ranges. Although seedlings can emerge from faecal piles, establishment of such seedlings seems to be infrequent. Removal of seeds from faeces by rodents is often considered seed predation. We show that removal of seeds from bear faeces by seed‐caching rodents in the Sierra Nevada, USA, represents a second phase of seed dispersal that benefits some fleshy‐fruited plants. Using Trail Master infrared cameras to photograph animals and scandium‐46, a gamma‐emitting radionuclide, to track seeds, we determined that deer mice Peromyscus maniculatus removed seeds from bear faeces and cached them in soil. Caches typically contained 1–3 seeds buried 5–10 mm deep. These seeds escaped several sources of mortality by being moved to relatively safe locations, but deer mice also eventually eat many of the cached seeds. A field germination study confirmed that seed burial increased seedling emergence. Rodents removed seeds in bear faeces more quickly than those in bird faeces in one year, but seeds in bird faeces were removed faster in another year. Results varied across two years, probably because of availability of alternative food sources or changes in deer mice population sizes. The two‐phase seed dispersal syndrome described here may be important in understanding seed dispersal by carnivores and large ungulates that produce large faecal deposits containing many relatively large seeds.     

Large herbivores affect the stoichiometry of nutrients in a regenerating woodland ecosystem

Previous studies on the effects of herbivores on nutrient cycling have given little consideration to the relationship between soil nitrogen (N) and phosphorus (P) availability. Here we examined how browsing by red deer influences the relative availability of N and P in a regenerating woodland ecosystem. We found that removal of browsing by fencing for 14 years led to a shift from N toward P limitation of the dominant tree species Betula pubescens . This was evidenced by a significant increase in foliar N:P ratio of B. pubescens as a result of removal of browsing; mean N:P ratio of foliage from browsed areas was 13.2 suggesting that trees growing in browsed areas were N limited, whereas foliage from unbrowsed areas had a mean N:P ratio of 15.8, suggesting that these areas were more P limited. Further evidence of a shift toward P limitation in unbrowsed areas came from the finding that root uptake of labelled ³²P was significantly greater in roots collected from unbrowsed than browsed trees. Soil phosphatase activity did not significantly differ between browsed and unbrowsed areas. Our data indicate therefore that herbivores have the potential to significantly affect the stoichiometry of N and P in forest ecosystems.     

Experimental studies of seed predation in old-fields

Summary In a pair of experiments conducted in old-field habitats in southwestern Michigan (USA), we examined rates of seed loss to post-dispersal predators (ants and rodents). Seeds from 4–6 species of biennial plants were tested over a range of seed densities and habitat types. We found that seed removal was significantly higher in vegetated habitats than in areas of disturbed soil (both simulated small-animal diggings and a plowed field). In the undisturbed vegetation, seed losses ranged from 1–20% of seeds removed/day.An exclosure experiment demonstrated that ants and rodents foraged selectively for seeds of the six plant species tested. Rodents (Peromyscus maniculatus) fed preferentially on species producing large seeds (predominantly Tragopogon dubius). Ants (Myrmica lobicornus) foraged on smaller seeds, although their foraging preferences were not based strictly on seed size.Seed density had only a minor effect on predation rate over the range of densities tested. Predators, instead appeared to treat each experimental group of seeds as a single prey patch. Consequently, predation intensity was quite variable over distances of <20 m within a relatively homogeneous section of habitat.These field experiments provide initial estimates of seed losses to post-dispersal predators in old-field habitats. Rates of seed loss were generally less than those reported from desert or semi-arid habitats. However, for some old-field species, seed losses averaged an appreciable 10–20% day. The selective nature of the seed predators, plusthe relative patchiness of predation intensity in space, suggest that postdispersal seed predation can play a role in determining the distribution and/or abundance of old-field herbs.     

Two-phase seed dispersal: linking the effects of frugivorous birds and seed-caching rodents

Frugivorous birds disperse the seeds of many fruit-bearing plants, but the fate of seeds after defecation or regurgitation is often unknown. Some rodents gather and scatter hoard seeds, and some of these may be overlooked, germinate, and establish plants. We show that these two disparate modes of seed dispersal are linked in some plants. Rodents removed large (>25 mg) seeds from simulated bird feces (pseudofeces) at rates of 8–50%/day and scatter hoarded them in soil. Ants (Formica sibylla) also harvested some seeds and carried them to their nests. Rodents carried seeds 2.5±3.2 m to cache sites (maximum 12 m) and buried seeds at 8±7 mm depth. Enclosure studies suggest that yellow pine chipmunks (Tamias amoenus) and deer mice (Peromyscus maniculatus) made the caches. In spring, some seeds germinated from rodent caches and established seedlings, but no seedlings established directly from pseudofeces. This form of two-phase seed dispersal is important because each phase offers different benefits to plants. Frugivory by birds permits relatively long-range dispersal and potential colonization of new sites, whereas rodent caching moves seeds from exposed, low-quality sites (bird feces on the ground surface) to a soil environment that may help maintain seed viability and promote successful seedling establishment.     

Comparison of genetic variation in populations of wild rice, Oryza rufipogon, plants and their soil seed banks

Wild rice, Oryza rufipogon, has endangered species conservation status and it is subject to in situ conservation in China. To understand the potential of the seed bank in species conservation and population restoration, this study compared the genetic diversity of O. rufipogon plants with that of its soil seed banks in two marshes. A total of 11 pairs of rice SSR primers were used and 9 were polymorphic. Allele frequencies of the seeds differed significantly from those of surface plants and varied between soil layers. Relatively more alleles and higher genetic diversity (H _e) were found in plant populations, relative to seed banks. The numbers of germinable seeds and the level of genetic variation in seed banks decreased with the increasing of soil depth, indicating a rapid seed loss. Genetic differentiation was detected between sites and between plant and seed populations, as well as among seeds of different soil strata. Rapid seed loss, partly dormancy loss, and nonrandom seed mortality are discussed as the possible contributors to the pattern of reduced genetic variation within seed banks, compared to plants. These could also be responsible for the considerable genetic differentiation between populations. The seed population held about 72% of the total genetic variation of O. rufipogon in each marsh, indicating the potential of seed banks for restoring population variabilities if the plant populations were lost.     

Trait‐mediated indirect interactions: Moose browsing increases sawfly fecundity through plant‐induced responses

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Foliar nutrients shape fungal endophyte communities in Western white pine (Pinus monticola) with implications for white-tailed deer herbivory

Asymptomatic fungal endophytes colonize tissues of woody plants worldwide, with largely unknown ecological effects. Using culture-based methods and ITS1-5.8S-ITS2 rDNA sequence analysis, we investigated differences between foliar endophyte communities in disease-resistant hybrid and wild-type Pinus monticola (Western white pine) trees with observed variation in tree growth, vigor, and browsing damage by white-tailed deer (Odocoileus virginianus). We isolated 69 phylotypes of endophytic fungi in at least 39 genera, including 26 that have not previously been reported in P. monticola. Principal components analysis revealed that endophyte communities differed between browsed seedlings, unbrowsed seedlings, and unbrowsed adult trees. Sulfur, nitrate and calcium concentrations correlated with endophyte community differences among tree groups based on a distance-based redundancy analysis. Our results indicate that foliar nutrient variation influences endophyte community assembly and deer herbivory in P. monticola on a small landscape scale (80 hectares).     

Intensity of pre‐dispersal seed predation in the invasive legume Leucaena leucocephala is limited by the duration of pod retention

Abstract The intensity of seed predation the invasive tropical legume Leucaena leucocephala by the bruchid Acanthoscelides macropthalmus was investigated in south‐eastern Queensland, Australia. The number of seeds damaged by A. macropthalmus as a proportion of total seeds available was found to increase the longer the pods remained on the tree. Seed predation ranged from a mean of 10.75% of seeds on pods that remained on the plant for 1 month and increased to 53.54% for pods that remained of the plant for 4 months. The low bruchid populations at high pod densities results in ‘predator satiation’. However, pods dehisce over time and the proportion of pods available over time to the bruchid correspondingly declines. By the time bruchid densities build up, most pods have dehisced and the seeds consequently escape predation. As a result the number of seeds lost to bruchid damage increases only marginally over time. Despite the levels of seed predation observed over the course of the study, the number of seeds in the soil seedbank almost doubled over time increasing from 8.5 seeds m^?3 to 15.5 seeds m^?3 over a 4‐month period. Levels of seed predation and addition of seeds to the soil seedbank were not correlated. The taxonomic (subspecies) status and apparency of host plants as measured by plant and patch traits (average plant height, density of podding plants and patch size) did not influence levels of seed predation. Pre‐dispersal seed predation studies need to take into account the pod/seed retention behaviour of the plant. The ability of the bruchid to regulate the invasiveness of Leucaena through influencing its demography is likely to be diminished if the insect populations cannot increase rapidly enough to use the seeds before pod dehiscence.     

Resource availability and plant diversity explain patterns of invasion of an exotic grass

Aims In this study, we examine two common invasion biology hypotheses—biotic resistance and fluctuating resource availability—to explain the patterns of invasion of an invasive grass, Microstegium vimineum.Methods We used 13-year-old deer exclosures in Great Smoky Mountains National Park, USA, to examine how chronic disturbance by deer browsing affects available resources, plant diversity, and invasion in an understory plant community. Using two replicate 1 m 2 plots in each deer browsed and unbrowsed area, we recorded each plant species present, the abundance per species, and the fractional percent cover of vegetation by the cover classes: herbaceous, woody, and graminoid. For each sample plot, we also estimated overstory canopy cover, soil moisture, total soil carbon and nitrogen, and soil pH as a measure of abiotic differences between plots.Important findings We found that plant community composition between chronically browsed and unbrowsed plots differed markedly. Plant diversity was 40% lower in browsed than in unbrowsed plots. At our sites, diversity explained 48% and woody plant cover 35% of the variation in M. vimineum abundance. In addition, we found 3.3 times less M. vimineum in the unbrowsed plots due to higher woody plant cover and plant diversity than in the browsed plots. A parsimonious explanation of these results indicate that disturbances such as herbivory may elicit multiple conditions, namely releasing available resources such as open space, light, and decreasing plant diversity, which may facilitate the proliferation of an invasive species. Finally, by testing two different hypotheses, this study addresses more recent calls to incorporate multiple hypotheses into research attempting to explain plant invasion.     

The soil seed bank of Triodia basedowii in relation to time since fire

Triodia basedowii seeds were found almost exclusively within Triodia hummocks, both in the centres and under the edges. Averaged over the whole ground surface, live seed densities in soil and litter were 85-263 m^?2 in stands which had been burnt 9 and > 35 years previously. These live seeds comprised only 56% of all filled grains, and in turn filled grains were present in only about 6% of all fruits. Thus > 4% of fruits contained live seeds. A site burnt 1 year previously had about 35 live seeds m^?2 still ungerminated, but at sites burnt 3 years previously none of the pre-fire seed bank was alive. After fire, juvenile plants were found predominantly around the edges of where hummocks had been before the fire, suggesting that seeds survive fires better around the edges.     

Effects of introduction and exclusion of large herbivores on small rodent communities

In this study we analysed the effects of large herbivores on smallrodent communities in different habitats using large herbivore exclosures. Westudied the effects of three year grazing introduction by red deer(Cervus elaphus L.) in previously ungrazed pine and oakwoodland and the exclusion of grazing by red deer, roe deer(Capreoluscapreolus L.) and mouflon (Ovis ammon musiminL.) in formerly, heavily grazed pine woodland and heathland. At eight exclosuresites within each habitat type, small rodents were captured with live trapsusing trapping grids. At each trapping grid, seed plots of beechnuts(Fagus sylvatica L.) and acorns (Quercusrobur L.) were placed to measure seed predation by rodents.Exclusion of grazing by large herbivores in formerly, heavily grazedhabitats had a significant effect on small rodent communities. Insideexclosureshigher densities of mainly wood mice (Apodemus sylvaticusL.) and field voles (Microtus agrestis L.) were captured.Introduction of grazing by red deer appeared to have no significant negativeeffects on small rodent communities. The seed predation intensity of beechnutsand acorns by small rodents was significantly higher in ungrazed situations,particularly in habitats that were excluded from grazing. The differencesbetween grazing introduction and exclusion effects on small rodent communitiescan be explained by differences in vegetation structure development. Therecovery of heavily browsed understory vegetation after large herbivore grazingexclusion proceeded faster than the understory degradation due to grazingintroduction. Small rodents depend on structural rich vegetations mainly forshelter. We conclude that large herbivores can have significant effects onvegetation dynamics not only via direct plant consumption but also throughindirect effects by reducing the habitat quality of small rodent habitats.     

Evaluation of potential deer browsing impact on sunflower (<Emphasis Type="Italic">Helianthus annus</Emphasis>)

Large herbivores are the key species for game management in the Central Europe. Analyses of factors affecting the feeding behaviour of herbivores and consequences of their browsing are therefore highly important both for farmers and for game managers as the protective measurements should be focused on the most threatened fields. The influence of fallow (Dama dama) and roe deer (Capreolus capreolus) browsing during vegetation period on sunflower production was studied. The experiment was carried out in 2006 on a field located near a forest complex. We marked out pairs of paired permanent plots and monitored deer impact regularly from the emergence of plants until the harvest. Herbivores damaged the sunflower intensively immediately after the emergence at the height of 1 to 2 cm above the ground. When the plants had reached approximately 15-40 cm in height, deer browsed the top shoots and as the plants grew higher the browsing was restricted to leaves or to substitute stems of the previously browsed plants. Sunflower ceased to attract big herbivores in flowering stage. Browsing significantly affected the yield of seeds. Approximately one half of the plants that had been damaged in early stage died as well as 12.5% of plants that had been damaged at second term; the rest produced substitute stems. Almost 33% of the substitute stems did not form disc florets; the second third of them formed disc florets with a diameter of 6-8 cm, and the last third set disc florets with a diameter of 8-10 cm.