Effect of root competition and shading on resprouting dynamics of Erica multiflora L.

Abstract. Resprouting from underground structures is one of the main regeneration strategies of Mediterranean shrubs after aerial biomass disturbance such as fire or clear-cutting to reduce fire risk. In order to study the effect of root competition and shading (simulated shoot competition) on Erica multiflora, growth, morphology, flowering performance and sprout size variability during resprouting, a factorial field experiment was conducted in which neighbours around target plants were eliminated and plants were shaded with mesh for two years. Root competition reduced sprout recruitment and sprout density (number of sprouts per unit stump area) more strongly than did shading. The negative effect of root competition on sprout biomass was constant with time, while the reduction due to shading increased with time. There was an interaction between root competition and shading on the biomass of sprouts 22 months after treatment: genets without root competition and shading were four times larger than in any other treatment. Both shading and root competition also decreased percentage branching but did not modify maximum sprout height. Only shading decreased the leaf/shoot biomass ratio and the percentage of flowering genets. One year after resprouting, root competition counteracted the effect of shading on inducing sprout biomass variability within the genet because it decreased sprout density. 22 months after treatment, sprout biomass variability was not affected by any main effect. The results suggest that competition among sprouts within the genet is asymmetric. However, shading by genet neighbours may not always increase sprout biomass variability if root competition is also severe.     

Resprouting of Erica multiflora after experimental fire treatments

Abstract. The effect of fire intensity - both temperature and duration - on the resprouting pattern of the evergreen Mediterranean shrub Erica multiflora in relation to plant size, was experimentally investigated by subjecting plants to the flame of a propane torch, and observing mortality and resprouting after 5 and 20 months. Pre-treatment plant size was not important in determining post-fire plant survival, but it did influence the resprouting vigour, increasingly so with time. High temperatures induced higher mortality rates within populations, but duration of fire did not effect mortality. Biomass of resprouts was lower following more intense fire treatments, but this effect progressively disappeared over time, except in plants subjected to the most intense fire treatment. This is probably because of the increasing importance of the below-ground organs for the regeneration of the above-ground biomass. Some of the plants which were clipped but not exposed to fire also died 20 months after treatment. The effect of clipping onmortality andresprout-ing response, estimated as biomass of resprouts, was not significantly different from the effect induced by either low or medium temperature treatments, but was significantly different when compared with the effect of high-temperature treatments. Field observations show that the establishment of seedlings of E. multiflora is rare both after fire and between fires. Thus, our data support the idea that both a single fire or clipping can diminish the population size of a resprouting species. We conclude that fire may have a stochastic effect on E. multiflora populations, due to the variation in fire intensity existing within a single burning stand.     

Fire intensity and herbivory effects on postfire resprouting of Adenostoma fasciculatum in southern California chaparral

Summary Resprouting is the main regeneration mechanism after fire in Mediterranean-type ecosystems. Herbivores play an important role in controlling postfire seedling establishment, but their influence on regeneration by resprouting is less well known. To study the effects of fire intensity on resprouting of Adenostoma fasciculatum in southern California chaparral, and its interaction with herbivory, we conducted an experimental burn at three levels of fire intensity. We found that increasing fire intensity increased plant mortality, reduced the number of resprouts per plant, and delayed the time of resprouting. Herbivory increased with fire intensity, and was related to the time of resprouting. Plants resprouting later in the season and out of synchrony with the main flush were attacked more readily by herbivores. Post-resprouting mortality also increased with fire intensity and was significantly associated with herbivory in the higher fire intensity plots. Fire intensity effects on chaparral regeneration by resprouting may be farreaching through effects on the population structure, resprout production, and growth of Adenostoma fasciculatum.     

EFFECTS OF COMPETITION AND DISTURBANCE ON THE RESPROUTING PERFORMANCE OF THE MEDITERRANEAN SHRUB ERICA MULTIFLORA L. (ERICACEAE)

Two field experiments were designed to evaluate the importance of competition, fire, repeated disturbance, and their interactions on the vegetative and reproductive performance of the Mediterranean shrub Erica multiflora over a 2.5-yr period. In a burn experiment, fire was applied to the ground-level stumps of previously clipped 13-yr-old plants with a propane torch and competition was diminished by removal of neighboring plants. Fire resulted in a reduction of sprout vigor and biomass of flowers; mature neighbors also reduced E. multiflora sprout vigor and flowering. The interaction between fire and competition was nonsignificant. In a stand burned by a wildfire we studied the effects of regenerating neighbors on target plants by removing all neighbors or only Quercus coccifera, the most dominant species in the burned stand. In this stand we also simulated herbivory by repeatedly clipping the sprouts of E. multiflora. Regenerating neighbors did not affect target plant sprout vigor after the wildfire, but did cause a decrease in the biomass of flowers per plant. Survival decreased after repeated clipping but was not affected by neighborhood treatment. The results suggest that the importance of competition on resprouting vigor was temporally variable. Variables related to plant size rather than species determined competitive superiority: resprouting neighbors did not affect resprouting performance of target plants, but mature neighbors did. In nature, fire may directly reduce vegetative and reproductive biomass by the heating effect. But it may have an indirect positive effect on biomass, by reducing competition among plants. Frequent disturbances that removed aboveground biomass of E. multiflora had a detrimental effect on target plant survival independent of neighborhood effect.     

Regeneration of a dominant Mediterranean dwarf-shrub after fire

Abstract. The regeneration after fire of the dominant east Mediterranean dwarf-shrub Sarcopoterium spinosum was studied under various habitat and geographic conditions in northern Israel, northern Crete and the Aegean coast of Turkey. Age structures of regenerating stands were determined 3–9 yr after fire on 13 1 mx 1 m sample stands by analysis of growth rings in the taproot crown of 874 plants. S. spinosum regenerated either by massive seedling recruitment in some habitats or by resprouting from surviving meristems in others. This versatility facilitates adaptation of the species to widely different environmental conditions and is a factor in the maintenance of its dominance after fire at occupied sites. In the years after fire, the growth of younger plants within the stand at all sites was severely suppressed by the older shrubs. Consequently, the age structure of the stands was dominated by one or two older cohorts that became established soon after fire. In addition, on most habitats, older shrubs (usually older than 6 yr) were often composed of clusters of plants that suggested clonal proliferation of ramets. The strongly peaked age structure, together with the appearance of clonal regeneration on the older plants, suggests that subsequent maintenance of the stand was not dependent on recurrent seedling recruitment. This can explain the persistence of S. spinosum in stands of herbaceous vegetation despite the extreme sensitivity of the seedlings to competition under such conditions.     

The role of tree sprouts in the restoration of stand structure and species diversity in tropical moist forest after slash-and-burn agriculture in Eastern Paraguay

The contribution of tree sprouts to the recovery of tropical moist forest in Eastern Paraguay after swidden agriculture was examined in 2–15 yr old forest fallows and compared with sprouting in mature forest. The proportion of stems of sprout origin, as individuals arising from stumps or lower parts of live stems ( 1 m), in the stem density declined from 59.5% (stems 1–4.9 cm DBH) and 21.0% (stems 5 cm DBH) in the young regrowth stands (2–5 yr old) to 32.9% and 19.6%, respectively in the older regrowth stands (10 and 15 yr old). Sprouts were absent in the mature forest. Out of 58 species sampled in the regrowth stands, 28 occured both as resprouts and seed regeneration, 7 were only found as resprouts, and 23 were only present as seed-established individuals. No significant relationship was found between the successional status or the growth form of species and apparent resprouting capacity. Seed-established individuals of Trema micrantha were predominant in the two and three-year old regrowth stands. In the more advanced successional stages, T. micrantha was replaced by Cecropia pachystachia and other secondary species. Species richness increased during succession. Species-abundance distribution in the successional stands followed a log series pattern, whereas the mature forest showed a log normal distribution. Floristic similarity to the mature forest, calculated with the qualitative Soerensen index, increased from 0.45 (1–4.9 cm DBH) in the young regrowth stands to 0.52 in the older regrowth stands. In the tree stratum ( 5 cm DBH), however, floristic composition approached only 0.28 in the younger regrowth stands and 0.44 in the older regrowth stands, respectively that of the mature forest.     

Effects of disturbance caused by traditional Spanish rural land use on the regeneration of Cytisus multiflorus

Abstract. Cytisus multiflorus is a leguminous matorral shrub native to the NW Iberian Peninsula, where it is one of the most important species in the extension of matorral at the expense of set-aside agricultural land. Dehesas have traditionally been used for extensive livestock raising and matorral was periodically burnt, cut or pulled out. The two latter practices are now out of use. However, burning is more frequent than in the past. The effects of fire, cutting, and pulling out of C. multiflorus on its regeneration was studied in order to ascertain whether the presently increasing distribution of the species relates to fire-stimulated regeneration or to the reduction of other traditional practices. Three years after treatment two sets of parameters were determined: 1. Plant origin: seedlings and different ramet types (ramets=resprout clumps), density, weight, and biomass as well as the percentage of resprouting. 2. Seed persistence at various soil depths. The possible mechanisms of breaking dormancy and plant emergence in different years after fire were studied in other experiments. The results suggest that the regeneration mechanism in C. multiflorus is stimulated by fire, but it is not an exclusive relationship. Stimulation occurs also after other disturbances leading to the total elimination of aerial biomass. The present expansion of the species does not appear to result from the abandonment of some traditional practices, such as cutting or pulling out, but from frequent fires (resulting in aerial-biomass elimination).     

Sprout initiation and growth for three years after cutting in an abandoned secondary forest in Kyoto,Japan

Secondary forests in Japan have been abandoned and the ecosystem has degraded since the high economic growth period. We carried out cutting in January in three small areas of a long-abandoned secondary forest and investigated the sprout initiation and growth of woody plants for three years in order to reveal the early stage of sprout regeneration and to understand the sprouting ability and characteristics of each species for effective management. The percentage of sprouted stumps and the number of sprouting shoots was substantially maximized in autumn in the first year. These results suggest that autumn monitoring in the first year after cutting shows the maximum percentage of sprouted stumps and the maximum sprout number when cutting was conducted in the dormant season. With regards to species characteristics, Eurya japonica showed a low percentage of sprouted stumps in the lower plot, where the mean diameter at breast height for this species was smaller than in the other plots. The sprouting ability of E. japonica was deemed to be influenced by parent tree size. Ilex pedunculosa and Lyonia ovalifolia var. elliptica had high percentages of sprouted stumps and many sprouts. These species are useful for obtaining sprouting shoots (e.g., for firewood), but it is difficult to control their sprouting.     

Resprouting in the Mediterranean‐type shrub Erica australis afffected by soil resource availability

Abstract. Soil resource availability may affect plant regeneration by resprouting in disturbed environments directly, by affecting plant growth rates, or indirectly by determining allocation to storage in the resprouting organs. Allocation to storage may be higher in stressful, low resource‐supply soils, but under such conditions plant growth rates may be lower. These factors could act in opposite directions leading to poorly known effects on resprouting. This paper analyses the role played by soil resources in the production and growth of resprouts after removal of above‐ground plant tissues in the Mediterranean shrub Erica australis. At 13 sites, differing in substrate, we cut the base of the stems of six plants of E. australis and allowed them to resprout and grow for two years. Soils were chemically analysed and plant water potential measured during the summer at all sites to characterize soil resource availability. We used stepwise regression analysis to determine the relationships between the resprouting response [mean site values of the number of resprouts (RN), maximum length (RML) and biomass (RB)] and soil nutrient content and plant water potential at each site. During the first two years of resprouting there were statistically significant differences among sites in the variables characterizing the resprouting response. RML was always different among sites and had little relationship with lignotuber area. RN was less different among sites and was always positively correlated with lignotuber area. RB was different among sites after the two years of growth. During the first months of resprouting, RN and RML were highly and positively related to the water status of the plant during summer. At later dates soil fertility variables came into play, explaining significant amounts of variance of the resprouting variables. Soil extractable cations content was the main variable accounting for RML and RB. Our results indicate that resprout growth of E. australis is positively affected by high water availability at the beginning of the resprouting response and negatively so by high soil extractable cation content at later periods. Some of these factors had previously shown to be related, with an opposite sign, to the development of a relatively larger lignotuber. Indeed, RML and RB measured in the second year of resprouting were significantly and negatively correlated with some indices of biomass allocation to the lignotuber at each site. This indicates that sites favouring allocation to the resprouting organ may not favour resprout growth.     

天童几种常绿阔叶林优势种在砍伐后萌枝更新的初步研究

对以萌生方式形成的木荷、石栎、苦槠、栲树、米槠植株的根桩和萌枝状况进行了调查及测量。结果显示各种类萌枝数的大小顺序是:木荷>苦槠>石栎>米槠>栲树;结合萌枝状况可以推断萌枝能力的大小顺序应该是:木荷>苦槠>石栎>栲树>米槠。砍伐对木荷、石栎、苦槠、栲树、米槠萌芽更新都会造成影响,对栲树、米槠影响更大,而对木荷、石栎、苦槠影响较小。从植物萌生角度来说,这是形成研究地区大面积的以木荷、石栎、苦槠为优势种组成的次生灌丛的主要原因。     

Comparative genet survival after fire in woody Mediterranean species

Summary Using data from three fires in northeastern Spain, we tested a condition necessary to support the idea that fire has been a factor in the evolution of the resprouting habit: populations of all resprouting species within a community should show high levels of genet survival after fires and show a low coefficient of variation. Species with high mean survival values were:Quercus ilex L.,Phillyrea latifolia L., andViburnum tinus L., with 88, 86 and 83% survival respectively; these groups had resprouts emerging from rootcrowns. Then followedArbutus unedo L. (75%),Pistacia lentiscus L. (73%),Erica arborea L. (77%),Erica multiflora L. (57%) andJuniperus oxycedrus L. (55%). This last group had resprouts from lignotubers or burls. These two groups also differed in the variability around the mean: the first showed a lower coefficient of variation, 6–12, and the second ranged from 19 to 26. Slope exposure had no significant influence on the process of resprouting, but soil depth did, with precipitation as a covariate. In the shallow soil category, the difference in genet survival between southern and northern exposures was 14% (71% vs. 57%); while the difference in the deep soil category was low, 5% (87% vs. 82%). There was no significant interaction. The component of variance for soils was larger than that for species-specific effects; substantial overlap of the within-species variance indicated that species responded as if they were a single hypothetical population, in which most of the variation in chances of survival was due to the soil conditions. The possession of the resprouting habit did not ensure a high performance. Hence, we find weak support for fire as a factor in the evolution of the resprouting habit.     

Regeneration after fire in Triodia R. Br.

Hummock grasses in the genus Triodia R. Br. were examined at 116 recently burned locations across mainland Australia, and were recorded as regenerating by resprouting, or by seed only. Prior to this survey it was known that the capacity to resprout varies considerably in Triodia, but it was unclear whether some species might be entirely resprouting and other species entirely fire-killed; whether this might be associated with particular traits of species or particular landscape types; or whether resprouting might be more common in particular regions such as the northern monsoonal grasslands. Seven species had both fire-killed and resprouting populations represented among the sites examined. Three species [T. basedowii E. Pritzel, T. marginata N.T. Burbidge and T. melvillei (C.E. Hubbard) Lazarides] were recorded as fire-killed at all sites examined, and five species [T. bynoei (C.E. Hubbard) Lazarides, T. bunicola (S.W.L. Jacobs) Lazarides, T. intermedia Cheel, T. molesta N.T. Burbidge and T. spicata N.T. Burbidge] were recorded as resprouting at all sites. Another seven species were recorded at one site only. There was no clear overall trend for fire-killed populations to be more prevalent in south rather than north, or east vs west, or coastal vs inland parts of the continent. No clear relationships were found between regeneration strategy and site attributes. Considered as a group, resprouting species were more likely to have an open growth form than a dense growth form, whereas the opposite was true for fire-killed species. Given that no trait either of species or of landscape was found to be a consistent correlate of resprouting, a likely inference is that resprouting might vary between different fires, even for a given population at a given site. Against this inference, fire-killed populations had substantial densities of seedlings much more often. Longitudinal studies would be needed to demonstrate directly whether resprouting varied between different fires at a site, and to investigate the implications of this for maintenance or extinction of local populations.     

No allocation trade-offs between flowering and sproutingin the lignotuberous,Mediterranean shrub Erica australis

Trade-offs between allocation to sexual or vegetative regeneration capacity are well established as a driving force in the life history patterns of plants in fire-prone environments. However, it is not known whether such trade-offs exist in plants which after aboveground removing disturbances, such as fire, may regenerate by sexual (seeding) or asexual (sprouting) mechanisms. We evaluated whether in the fire-recruiting resprouter Erica australis, which after fire can regenerate by seedling establishment or resprouting, a larger investment in flowers and seeds prior to being disturbed by clipping its aboveground parts would decrease subsequent sprouting, that is, its vegetative regeneration capacity. We analysed the relationships between flower and seed production and the ensuing production and growth of sprouts of six plants from thirteen different sites in central-western Spain. We found no significant relationships between measures of sexual reproductive effort and resprout production and growth 6 months after clipping the aboveground parts of the plants. No evidence of trade-offs between sexual and asexual efforts was found. Furthermore, no significant relationship was found between lignotuber total non-structural carbohydrates and sexual reproductive effort. In addition, 2 years after the disturbance, resprout biomass was positively and significantly correlated with sexual reproductive effort prior to the disturbance. This indicates that growth of resprouts was higher at the sites where plants made a greater reproductive effort. The sites that were more favourable to producing flowers and seeds could also be more favourable to resprouting.     

Post-fire resprouting of shrubby species in Mediterranean maquis

The vegetative resprouting of mediterranean maquis shrubby species was examined eight years after fire. Post-fire regeneration occurs through the resprouting of stumps. All species (Quercus ilex L., Phillyrea latifolia L., Arbutus unedo L., Erica arborea L., Pistacia lentiscus L.) show a rapid growth in the first years after fire, and a decrease already from 4^th–5^th year.All the species survived the fire and reconstituted a community similar to that unburned in a relatively short time span.     

Bud structure and resprouting in coppiced stools of Salix viminalis L., S. eriocephala Michx., and S. amygdaloides Anders

Fast-growing willows are cultivated as coppice in short rotation biomass plantations. The production and sustainability of the system is based on the ability of trees to resprout after repeated harvesting. The large variation in coppicing ability is due to plant genotypic differences in structure and physiology as well as environmental factors. Morphological and structural prerequisites for resprouting were compared in two shrubby willows with high coppicing ability, S. viminalis and S. eriocephala, and one tree-formed species, S. amygdaloides, with low coppicing ability. The initiation and development of buds and the resprouting pattern of coppiced stools were compared. All buds were axillary in origin and showed the same principal structure consisting of one main shoot primordium and two lateral primordia. In S. viminalis and S. eriocephala the lateral buds contained several leaf primordia and sprouted shortly after the main bud. In S. amygdaloides further development of lateral buds was inhibited after formation of two budscales, and leaf primordia were not formed until the buds were forced to sprout. The number of sprouts developing after coppicing were correlated to the structure and number of buds and their position on the stools. Self-thinning rate was high and many shoots originating from lateral buds died. Most buds were located above ground on the remaining basal portions of harvested stems. No adventitious buds were found on the stools. Significantly different bud differentiation pattern and frequent sylleptic sprouting resulted in lower coppice response in S. amygdaloides compared to S. viminalis and S. eriocephala.     

Fitness of resprouters versus seeders in relation to nutrient availability in two Plantago species

Two contrasting strategies of plants from disturbed areas are reported to depend on nutrient availability. Resprouters, investing into storage and capable of vegetative regeneration after disturbance, are predicted to be enhanced in nutrient poor environments. This contrasts to seeders, which invest preferentially into seed production and regenerating only from seeds, and are thought to prevail in nutrient rich environments. To test such predicted dichotomy, we set up an experiment with two facultative resprouters with contrasting nutrient demands and assessed the fitness of individuals regenerated from seeds and root fragments in differently productive environments. We hypothesized that 1) plants with higher nutrient demands have a higher fitness as seeders irrespectable of nutrient availability and/or 2) both species will have a higher fitness as resprouters under lower nutrient availability and as seeders when nutrient availability is higher. Nutrient availability was also manipulated prior to and after disturbance to evaluate the impact of changing nutrient availability on the strategy of resprouting. The results of our pot experiment with Plantago lanceolata and Plantago media supported the first but not the second hypothesis. Moreover, high nutrient availability prior to disturbance negatively affected resprouting success, but the growth and fitness of successfully regenerated individuals were enhanced under higher nutrient availability. We concluded that resprouting from roots after disturbance is affected by nutrient availability, but this effect considerably differs between individual life-history stages.     

Population dynamics of coniferous and broad-leaved trees in a Japanese temperate mixed forest

The growth and survival of coniferous and broad-leaved trees were followed over a 5-yr period in a temperate old-growth mixed forest in Japan, and dynamic features of the forest were studied in relation to the life history of the dominants, the coniferous Abies homolepis and the broad-leaved Fagus crenata. During this period, the gap formation rate was 31m² ha^?1yr^?1, the mortality of trees > 2m high was 1.7%/yr, and the rate of loss in basal area 1.4%/yr. These values were much higher than the recruitment, 0.3%/yr, and the total growth of surviving and new trees, 0.6%/yr, owing to the inhibition of regeneration by understorey dwarf bamboo (Sasa borealis). A transition matrix model based on DBH size classes predicts that the basal area of the forest will decrease by 14% in 50 yr, but that the DBH distribution of trees > 10 cm diameter will change little. Equilibrium DBH distributions assuming recruitment being equal to mortality, were quite different between broad-leaved and coniferous trees, reflecting different survivorship curves of the two dominants. The composition and structure of the forest may change depending on the pattern and frequency of disturbances, or episodic events, notably the synchronous death of Sasa borealis.     

Regional‐Scale Variation in Litter Production and Seasonality in Tropical Dry Forests of Southern Mexico1

Highly seasonal rainfall creates a pulse of litterfall in the southern Yucatan peninsula region, with cascading effects on the timing of essential nutrient fluxes, microbial dynamics, and vegetation growth. I investigated whether forest age or a regional environmental gradient related to rainfall has a greater effect on patterns of litterfall in this increasingly human‐dominated landscape. Litterfall was sampled in 10–13 stands in each of three locations spanning a rainfall gradient of ca 900–1400 mm/yr. Litter was collected monthly from November 1998 through January 2000 in mature forests and in secondary forests aged 2–25 yr. Despite a substantial precipitation gradient, age was the only significant predictor of annual litter mass. Two‐ to five‐yr‐old forests produced significantly less litter than 12–25‐yr‐old secondary forests (4.6 vs. 6.2 Mg/ha/yr), but the difference between older secondary forests and mature forests (9 percent) was not significant. Litter production increased with rainfall, but not significantly so. The pattern of litterfall was similar across locations and age classes, with a peak during late March or early April. However, litterfall seasonality was most pronounced in the old secondary and mature forests. Litterfall was more evenly distributed throughout the year in forests under 10 yr old. Seasonality of litterfall was also less pronounced at the wettest site, with less disparity between peak litterfall and off‐peak months. Seasonality was not related to soil texture. Forest age and rainfall are important drivers of litterfall dynamics; however, both litter mass and degree of seasonality depended more strongly on forest age. Thus, the impact of land‐use change on litter nutrient cycling is as great, if not greater, than the constraint imposed by the major natural environmental factor affecting tropical dry forests.     

Differential responses to defoliation frequency in little bluestem (<Emphasis Type="Italic">Schizachyrium scoparium</Emphasis>) in tallgrass prairie: implications for herbivory tolerance and avoidance

Plant responses to herbivory are complex. In grasses, relative growth rate (RGR), seed, and vegetative reproduction, resource allocation, and architecture vary differentially and often nonlinearly with grazing intensity. High grazing tolerance may be achieved through compensatory photosynthesis and leaf growth, or through demographic mechanisms such as activation of a belowground dormant bud bank. This study assessed the relationship between grazing frequency and responses of Schizachyrium scoparium (little bluestem) in a tallgrass prairie, and examined the roles of tiller growth, reproduction, and bud (meristem) populations in its persistence under grazing. Genets were subjected to varying simulated grazing frequencies for a period of 2 years. Strong differential responses were observed among plant traits. RGR, biomass, and flowering showed strong nonlinear reductions in response to increasing clipping frequency, with no evidence of threshold effects. However, meristem density was unaffected, and plants maintained a large bud bank across all clipping treatments. Tiller natality decreased initially, but increased with >4 clippings, suggesting that declines in tiller RGR are partially offset by increasing tiller natality, and that variation in genet size is driven more by demography than by variation in individual tiller growth. Increased grazing frequency also resulted in differential activation of buds at different positions (emerging within vs. outside the subtending leaf sheath), explaining the shift to a more prostrate growth form observed in many caespitose grasses under persistent grazing. Thus, although this grass species lacks the capacity for compensatory foliage re-growth, the maintenance of a large dormant bud bank and the differential activation of buds in different positions contribute to its grazing tolerance and avoidance, respectively, and its long-term persistence in grazed grasslands.     

Intraspecific competition and light effect on reproduction of Ligularia virgaurea,an invasive native alpine grassland clonal herb

The relationship between sexual reproduction and clonal growth in clonal plants often shows up at the ramet level. However, only a few studies focus on the relationship at the genet level, which could finally account for evolution. The sexual reproduction and clonal growth of Ligularia virgaurea, a perennial herb widely distributed in the alpine grasslands of the Qinghai‐Tibetan Plateau of China, were studied under different competition intensities and light conditions at the genet level through a potted experiment. The results showed that: (1) sexual reproduction did not depend on density or light, and increasing clonal growth with decreasing density and increasing light intensity indicated that intraspecific competition and light intensity may affect the clonal life history of L. virgaurea; (2) both sexual reproduction and clonal growth show a positive linear relationship with genet size under different densities and light conditions; (3) a threshold size is required for sexual reproduction and no evidence of a threshold size for clonal growth under different densities and light conditions; (4) light level affected the allocation of total biomass to clonal and sexual structures, with less allocation to clonal structures and more allocation to sexual structures in full sunlight than in shade; (5) light determined the onset of sexual reproduction, and the genets in the shade required a smaller threshold size for sexual reproduction to occur than the plants in full sunlight; and (6) no evidence was found of trade‐offs between clonal growth and sexual reproduction under different densities and light conditions at the genet level, and the positive correlation between two reproductive modes indicated that these are two integrated processes. Clonal growth in this species may be viewed as a growth strategy that tends to maximize genet fitness.