Relationships Between Climate and Flowering of Eight Herbs in a Swedish Deciduous Forest

Effects of annual variation in rainfall, temperature and humidityon flowering abundance of eight temperate woodland plants (Anemonenemorosa, Cardamine bulbifera, Lamiastrum galeobdolon,Oxalisacetosella , Ranunculus ficaria, Stellaria holostea, Viola reichenbachianaand Viola riviniana) were studied during 12 consecutive years(1989–2000) in a hornbeam (Carpinus betulus) forest insoutheast Sweden. Above-average rainfall/humidity in late summerto early autumn of the preceding year increased flowering abundancein L. galeobdolon, O. acetosella, V. reichenbachiana, V. rivinianaand, especially, in R. ficaria, but not in S. holostea and A.nemorosa. Moreover, flowering of R. ficaria and O. acetosellawas positively related to rainfall/humidity during several partsof, or the entire, preceding year. On the contrary, floweringof S. holostea and A. nemorosa was closely related to low valuesof rainfall/humidity in autumn and/or winter of the precedingyear and also to low humidity in the current year in A. nemorosa.Two long periods (3–4 years) of increasing rainfall deficitcoincided with decreasing flowering abundance in most of thespecies, but not with decreasing vegetative development. Temperaturevariability was less consistently related to flowering. A coolperiod during the preceding summer or autumn seemed importantfor flowering in L. galeobdolon, O. acetosella and the Violaspecies, although these relations were, at least partly, causedby interactions with rainfall/humidity. No significant (P <0.05) correlations were found between flowering and the conditionsprevailing in April to May—the main flowering season—ofthe current year. Copyright 2001 Annals of Botany Company Climate, flowering, rainfall, temperature, Anemone nemorosa, Cardamine bulbifera, Lamiastrum galeobdolon, Oxalis acetosella, Ranunculus ficaria, Stellaria holostea, Viola reichenbachiana, Viola riviniana     

Disturbances by human trampling alter the performance,sexual reproduction and genetic diversity in a clonal woodland herb

Disturbances play a major role in structuring the community composition in a variety of ecosystems. The potential impact of disturbances on sexual reproduction and genetic diversity of plants has so far received little attention. We examined the effects of disturbance by human trampling on the performance, sexual reproduction and clonal diversity in the woodland herb Anemone nemorosa in six sites disturbed by intensive recreational activities and in six undisturbed sites in suburban forests in Switzerland. Disturbance by human trampling decreased shoot height of A. nemorosa and altered the size-dependent flowering probability function. Furthermore, in disturbed sites an increased percentage of aborted seeds was found, resulting in a reduced sexual reproductive potential of A. nemorosa populations. Both clonal and genetic diversity of A. nemorosa were reduced in disturbed sites. Our study shows for the first time that disturbance by human trampling can decrease the genetic diversity in a clonal woodland plant. This suggests that genetic aspects of woodland plants should be considered in restoring degenerated forest sites.     

For she that hath, to her shall be given…Implications of flowering in Anemone nemorosa L

We looked for life‐history trade‐offs between flowering, vegetative growth and somatic maintenance in the common woodland herb Anemone nemorosa. A. nemorosa forms a horizontal rhizome system consisting of previously formed annual segments and terminated by a flowering or non‐flowering shoot. Resources acquired by the aboveground parts are used for flowering, seed production, storage and growth of the annual segments. Resources stored in the rhizome during the growing period are used for preformation of buds, somatic maintenance between two growing periods and development of aboveground parts in the following spring. We hypothesised that the decision to invest in flower buds depends on the amount of resources stored in the recently formed annual segment. We also hypothesised a trade‐off between flowering and segment growth and, finally, as a consequence, we expected individual rhizomes to alternate between the flowering and the non‐flowering state. We found that segments producing flower buds were significantly longer than non‐flowering segments, indicating that resource level influences the function of the preformed buds. Contrary to our expectations, we found flowering rhizomes produced longer annual segments than non‐flowering rhizomes. We suggest the larger leaf area of flowering rhizomes and occasional abortion of flowers or seeds as possible mechanisms behind this pattern. Our study shows that even though the decision to produce a flower bud is taken in another time‐frame than that in which the actual flowering and fruiting takes place, an ostensibly inexpedient decision is changed to a neutral or even an advantageous incident.     

Responses of ground flora to coppice management in an English woodland – a study using permanent quadrats

Changes in the ground flora in sweet chestnut (Castaneasativa) woodland were studied over 11 years usingpermanent quadrats in two coppiced plots and one plot in a ride widened by treeremoval. Light and temperature were also recorded. The temperature range wasgreater in the ride than in the coppice plots. Light reaching the woodland floorin summer fell to less than 1% of incident radiation at later stages of thecoppice cycle. Species richness peaked in the second and third year aftercoppicing and then declined in both the coppice plots and the ride. A similarpattern was seen in total percentage frequency of cover. The dominant species,Anemone nemorosa, showed little response to the coppicecycle in terms of frequency, but showed a fourfold increase in floweringintensity in the second and third year following coppicing. Other speciesgenerally declined in frequency through the coppice cycle, and flowering waslargely suppressed in the later stages. The results are discussed in relation toalternative methods of woodland management.     

Effects of Photoperiod and Temperature on Shoot, Root and Rhizome Growth in ThreeLotus uliginosusSchkuhr Populations

The growth of three populations of greater lotus (Lotus uliginosusSchkuhrsyn.L. pedunculatusCav.) was compared at photoperiods of 10,12 and 14 h at a maximum day/minimum night temperature of 21/16°C and at maximum day/minimum night temperatures of 27/22,21/16, 18/13 and 15/10 °C at a photoperiod of 12 h. Shortdays (10 h) favoured root and rhizome development compared tolong days (14 h). A temperature regime of 15/10 °C restrictedrhizome development compared to the 18/13 and 21/16 °C regimes.Shoot growth was restricted at the highest temperature regime(27/22 °C). The cultivar Sharnae had fewer, but heavier,rhizomes than Grasslands Maku; this may indicate adaptationto the dry summers at its site of origin (Algarve, Portugal).The response of rhizome growth to temperature and photoperiodexplains part of the performance of greater lotus in the fieldat a wide range of latitudes. Grazing management to encouragethe persistence ofL. uliginosusin pasture in temperate environmentsmay include the exclusion of grazing livestock in autumn. Inthe sub-tropics, monitoring of rhizome production in the fieldwould be required before deciding the appropriate time intervalbetween grazing.Copyright 1998 Annals of Botany Company Lotus uliginosus(Schkuhr); greater lotus; temperature; daylength; shoots; roots; rhizomes.     

Le comportement parasitaire de Sclerotinia tuberosa (hedw.) Fuckel sur Anemone nemorosa L. Etude en microscopie photonique et electronique a balayage

Résumé Des rhizomes d'Anemone nemorosa infectés par Sclerotinia tuberosa ont été trouvés dans le sol. Ils ont été étudiés macroscopiquement, en microscopie photonique et en microscopie électronique à balayage. Des infections artificielles ont été réalisées in vitro. Un manchon mycélien entoure le rhizome, et des coussinets d'infection se forment au contact de la cuticule où ils émettent des filaments d'infection qui traversent les couches cuticulaires successivement sécrétées par l'hôte. La colonisation des tissus du rhizome se fait par voie intracellulaire, des appressoria simples servant à franchir les parois cellulaires, mais aussi par voie intercellulaire si l'infection débute au niveau d'une blessure du rhizome. Les mécanismes observés sont en accord avec les préférences nutritionnelles du champignon en culture pure.

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Rhizomes of Anemone nemorosa infected by Sclerotinia tuberosa have been found in soil. They have been studied macroscopically and by means of light and scanning electron microscopy. In addition artificial infections have been produced in vitro. Fungal hyphae coat the rhizome with a mycelial muff. Infection cushions develop near the cuticle, and they produce infection threads which penetrate through it. The colonization of the host plant tissues goes on either by intracellularly — the hyphae then go from cell to cell, perforating the cell walls by mean of simple appressoria — or by intercellularly — especially when the infection is initiated by a wound in the rhizome. The infection mechanisms observed here fit well with the nutritional requirements of the fungus in pure culture.

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Avec la collaboration technique de D. Bernillon     

The effects of phosphorus nutrition and soil pH on the growth of some ancient woodland indicator plants and their interaction with competitor species

The forest under-storey herbs Anemone nemorosa, Lamiastrum galeobdolon and Veronica montana are generally considered indicator species of old, broadleaved woodland sites where the soil fertility is often low. In a glasshouse bioassay, however, all three species not only showed large positive growth responses to supplied P concentrations (0–10mgL ^–1) solutions, but also tolerated high P concentrations (20–40mgL ^–1), well above those normally found in their natural habitat. Plants responded by raising the concentrations of P in their shoot and root tissues and increasing their biomass, resulting in an increased P uptake. A shade-tolerant competitor species, Urtica dioica, also grew vigorously across the full range of P concentrations, restricting the growth of the woodland species. This emphasises the difficulty of establishing semi-natural woodland vegetation in the presence of competitor species, for example in situations where new woodlands are planted on fertile ex-agricultural soils containing large residual concentrations of P. The influence of soil pH on the growth and nutrient relations of A. nemorosa, L. galeobdolon, V. montana, Poa trivialisandU. dioicawas determined in a separate experiment using an ex-arable soil as the growing medium with pH levels adjusted from 7.4 to 5.8 and 4.3 respectively. Acidifying the soil enhanced growth, but reduced the concentrations of N, P and K in the leaves of all three woodland species, probably due to dilution of these minerals in the increased dry matter production. The competitor species (P. trivialis and U. dioica) responded in similar manner to the woodland indicator species. These results suggest that manipulating soil pH as a means of facilitating the establishment of woodland indicator species in new farm woods is unlikely, in the short term, to be effective where competitor species are present.     

Nectar production in the pollen flower of Anemone nemorosa in comparison with other Ranunculaceae and Magnolia (Magnoliaceae)

The observation that the flowers of Anemone nemorosa offer nectar to pollinating bee-flies (Bombylius major) prompted this investigation into the site of nectar secretion and nectary tissue. To allow comparison on a broader basis, other nectar-secreting pollen flowers of the Ranunculaceae and Magnolia (Magnoliaceae) were included in the analysis. The contradictory information available on the function of the mouthparts of bee-flies during nectar and pollen feeding motivated us to investigate the proboscis structure in detail by SEM. Our investigations in Anemone nemorosa proved, for the first time, nectar secretion in the genus Anemone s.s. (i.e. other than the Pulsatilla group) and in addition, within the family, a new type of a carpellary nectary. The latter is an epithelial nectary involving the whole epidermis of the ovarian part of the carpel. The nectary of Anemone nemorosa resembles that of Magnolia (e.g. M. stellata), which we re-investigated. In both Anemone nemorosa and Magnolia stellata, nectar production is limited mainly to the female phase of the proterogynous flower. In this way, the attractiveness of the flower is also assured in the non-pollen presenting phase. Especially in Magnolia, with its numerous carpels arranged on a cone-like receptacle, the economic disadvantage of a choricarpous- compared to a coenocarpous-gynoecium is compensated for by nectar secretion by each carpel. When licking up the nectar droplets from the carpel surfaces, contact of the insect's body with each stigma may be achieved.     

The use of open-top chambers in forests for evaluating warming effects on herbaceous understorey plants

Open-top chambers (OTCs) are widely used experimental warming devices in open-field ecosystems such as tundra and alpine heath. However, knowledge of their performance in temperate deciduous forest ecosystems is largely lacking. The application of OTCs in forests might become important in the future since the effects of climate warming on growth, reproduction, and future distribution of understorey forest herbs have rarely been investigated. Therefore, polycarbonate OTCs covered with (OTCs+GF) and without permeable polypropylene GardenFleece (OTCs−GF) were installed in a temperate deciduous forest to create an experimental warming gradient. Short-term responses in phenology, growth, and reproduction of a model understorey forest herb (Anemone nemorosa L.) to OTC installation were determined. In a second growing season, an in-depth study of multiple abiotic conditions inside OTCs−GF was performed. Both OTCs+GF and OTCs−GF raised air and soil temperature in a realistic manner (ca. +0.4°C to +1.15°C), but OTCs−GF only in the leafless period (up to +1.5°C monthly average soil temperature). The early flowering forest herb A. nemorosa also showed a clear phenotypic response to OTC installation. Based on these facts and the large ecological drawbacks associated with OTCs+GF (mostly in connection with a higher relative air humidity and a lower light quantity) and very modest abiotic changes in OTCs−GF, we encourage the use of OTCs−GF in deciduous forest ecosystems for evaluating climate-warming effects on early flowering understorey forest herbs. There is also a potential to use this warming method on later flowering species, but this needs further research.     

Variation in breeding system among populations of the common woodland herbAnemone nemorosa (Ranunculaceae)

Recent studies of germination in natural habitats, of genetic variation within populations and of the relative proportion of vegetative and sexual reproduction in the clonal plant speciesAnemone nemorosa suggest that sexual recruitment by seeds from outcrossed flowers is important for the maintenance of this species' populations. Because published reports on its breeding system are controversial, pollination experiments were performed in five natural populations ofA. nemorosa. Differences in ovule number per flower were recorded among populations, but they were not related to obvious habitat differences. Seed/ovule-ratios were significantly higher after open pollination and artificial crossing than after either artificial or spontaneous selfing. Populations had no effect on seed/ovuleratios. Different breeding indices indicated thatA. nemorosa is mainly self-incompatible. Nevertheless, some seed set also occurred after selfing, and both artificial and spontaneous selfing exhibited higher variation in seed/ovule-ratios than open pollination and artificial crossing. Continuous variation in seed/ovule-ratios after selfing suggested that the expression and effectiveness of the self-incompatibility system ofA. nemorosa is influenced by both genetic variation and phenotypic plasticity.     

Colonization of secondary woodlands by Anemone nemorosa

Migration of the herb species Anemone nemorosa from older woodlands into adjacent, recently established deciduous woodlands on former arable land was studied. The wood anemone had colonized part of all studied recent woods, varying in age between 30 and 75 years. Cover of A. nemorosa in the recent woods decreased with increasing distance from the older woodland at all sites but one, indicating dispersal limitation during colonization. The advancing edge of most populations was characterized by negative logarithmic decrease in cover with establishment of isolated pioneer individuals and later gradual infill between pioneers. Migration rates were calculated by three methods. The mean migration rate of A. nemorosa based on observed maximum cover in the recent woods was 0.20 m year¹, 0.40 m year^-1 based on half maximum cover and 0.85 m year¹ based on the individual found farthest from the former woodland border. The calculated migration rates were consistently higher than the rate of possible rhizome growth. Seed dispersal and establishment is thus very important for colonization of new woodlands. Migration rates increased with tree canopy cover–especially cover of broad-leaved species with quickly decomposing litter–and with soil pH. Migration rates decreased with increasing grass cover in the field layer. These differences in migration rates may be due to increased micro-site availability for establishment at high canopy cover, low grass cover and high soil pH. Our results show that the wood anemone generally colonizes recent woods from nearby source populations. However, colonization proceeds relatively slowly and is limited by both seed dispersal and availability of suitable micro-sites. Gradients in abundance of A. nemorosa within secondary woods may be detectable for long periods of time and indicate the recent origin of a woodland.     

A population approach to vegetation structure

Abstract

A synthesis is presented of some research results on the structure and dynamics of populations with respect to the phytocoenosis structure. The first aspects to be considered are concerned with the dynamism, distribution and reproductive strategy of Anemone nemorosa: the vegetation structure either favors or inhibits the various reproductive strategies, thereby influencing the distribution pattern of the species. The second area of the present study is the demography and quantitative structure of Cytisus sessilifolius populations with respect to the problematic of secondary successions: the first results obtained open up interesting prospectives on the relationship between the vegetation dynamics and the frutescent populations structure.     

Estimation of the relative importance of sexual and vegetative reproduction in the clonal woodland herb Anemone nemorosa

Anemone nemorosa is a perennial rhizomatous plant of European woodlands. The “probability of clonal identity” method estimated the relative proportion of sexual to vegetative reproduction in this species to be 4.4% from allozyme genotype distributions. This result is congruent with investigations on the germination, short-term demography, population genetics, and breeding system of this species, and supports the hypothesis that even low levels of seedling recruitment can maintain considerable intrapopulational genetic diversity. Received: 2 March 1998 / Accepted: 24 July 1998     

A Model for Growth and Self-thinning in Even-aged Monocultures of Plants

A theoretical model is derived from simple postulates to describethe rates of growth and mortality of plants in populations ofdifferent densities. The growth rate is described by a modificationof the logistic growth differential equation in which the increasein weight of an individual plant depends on its area, s_i ratherthan on its weight. The effective area for growth of a plantis reduced by an empirical function, f(s_i) with two terms: oneterm expresses the constraint imposed upon the increasing totalarea of plants by the limited physical area of the plot; theother term allows for a competitive advantage or disadvantagefor plants of varying sizes. Depending on the value of the parametercontrolling the relative competitive advantage term, intrinsicvariability between plants can be amplified or suppressed. Anindividual plant dies if the f(s_i) results in a negative growthrate for that plant. Computer simulations of the growth andsurvival of plants at different population densities were run.The results exhibit characteristics that appear realistic uponcomparison with published data: a survival of the fittest occurringduring thinning; a line of slope close to –3/2 boundingthe graphs of log weight versus log density; and the occurrenceof bimodality, associated with subsequent mortality, on frequencydistribution of log weight. computer logistic model, growth differential equation, density-effect, competition, mortality, self-thinning     

Mechanisms of Central Die-back of Reynoutria japonica in the Volcanic Desert on Mt. Fuji. A Stochastic Model Analysis of Rhizome Growth

Reynoutria japonica (Polygonaceae) is a pioneer clonal herbcolonising the volcanic desert on Mt. Fuji (height 3776 m),central Japan; establishment of secondary successional speciesoccurs only in the central die-back parts of the clonal standsofR. japonica. Clonal stands were excavated and the morphologyand growth pattern of the rhizomes were investigated with specialreference to the mechanisms of central die-back. Four morphologicalparameters, length of mother rhizomes, and number, branchingpositions and branching angle of daughter rhizomes on respectivemother rhizomes were measured or counted, and their roles inrhizome growth were examined employing a stochastic computersimulation model of the whole stand development. The simulationsclarified that, of these four parameters, the branching anglewas the most influential determinant of the whole pattern ofshoot distribution and that the central die-back was producedwhen the mean branching angle was 40° or smaller. Theseresults strongly infer that the onset of central die-back iscaused intrinsically byR. japonica itself by having the meanbranching angle of 40°. The adaptive significance of thegrowth pattern is discussed in relation to resource acquiringand habitat exploitation strategies of this species. Below-ground morphology; branching angle; central die-back; clonal plant; computer simulation; Japanese knotweed;Reynoutria japonica Houttuyn; rhizome growth pattern     

Seasonal dynamics of shoot biomass of dominant clonal herb species in an oak–hornbeam forest herb layer

Seasonal fluctuations of light availability, nutrient concentrations, and moisture affect plant population traits like density, standing biomass, and flowering. We analyzed seasonal changes of density and shoot biomass of the four most frequent herb species growing in an oak–hornbeam forest community, i.e., Anemone nemorosa, Ficaria verna, Galeobdolon luteum, and Galium odoratum. In 2010 and 2011 plant biomass was harvested from 7 to 10 randomly situated square sample plots (0.36 m²) in the homogenous oak–hornbeam forest community every week in the spring and every two weeks in the summer and autumn. The highest abundance of Anemone nemorosa reached over 1000 shoots per m², of Ficaria verna 459.5 shoots per m², of Galium odoratum 83.6 shoots per m², and of Galeobdolon luteum 98.4 shoots per m² (means for 2010 and 2011, based on all sample plots). We did not observe negative correlation between density and shoot biomass. Growth rates of vegetative shoot biomass amounted to 0.857 mg day^?1 for Anemone nemorosa, 0.467 mg day^?1 for Ficaria verna, 0.722 mg day^?1 for Galium odoratum, and 0.448 mg day^?1 for Galeobdolon luteum (means for 2010 and 2011). Spring ephemerals had much higher densities of shoots than summer-greens. Summer-greens reached higher biomass of individual shoots than spring ephemerals. Flowering shoots constituted only 4, 2, and 11% of all shoots for A. nemorosa, F. verna, and G. odoratum, respectively. More resource availability resulting in high shoot biomass did not translate to higher share of flowering shoots.

     

Temperature effects on forest herbs assessed by warming and transplant experiments along a latitudinal gradient

Slow‐colonizing forest understorey plants are probably not able to rapidly adjust their distribution range following large‐scale climate change. Therefore, the acclimation potential to climate change within their actual occupied habitats will likely be key for their short‐ and long‐term persistence. We combined transplant experiments along a latitudinal gradient with open‐top chambers to assess the effects of temperature on phenology, growth and reproductive performance of multiple populations of slow‐colonizing understorey plants, using the spring flowering geophytic forb Anemone nemorosa and the early summer flowering grass Milium effusum as study species. In both species, emergence time and start of flowering clearly advanced with increasing temperatures. Vegetative growth (plant height, aboveground biomass) and reproductive success (seed mass, seed germination and germinable seed output) of A. nemorosa benefited from higher temperatures. Climate warming may thus increase future competitive ability and colonization rates of this species. Apart from the effects on phenology, growth and reproductive performance of M. effusum generally decreased when transplanted southwards (e.g., plant size and number of individuals decreased towards the south) and was probably more limited by light availability in the south. Specific leaf area of both species increased when transplanted southwards, but decreased with open‐top chamber installation in A. nemorosa. In general, individuals of both species transplanted at the home site performed best, suggesting local adaptation. We conclude that contrasting understorey plants may display divergent plasticity in response to changing temperatures which may alter future understorey community dynamics.     

Burial rituals inferred from palynological evidence: Results from a late Neolithic stone cist in southern Sweden

Soil samples from a late Neolithic stone cist in Hamneda, southern Sweden, were pollen analysed. The results of the analysis suggest that the local vegetation at the time of the burial was a half-open woodland with pasture and small-scale cereal growing, intermingled with stands ofTilia (lime),Quercus (oak) andCorylus (hazel). The analysis also gives unique information on the burial ritual. High pollen percentages ofHordeum type,Triticum type and undifferentiated Cerealia from among the shards of a pot deposited in the cist show that the pot originally contained cereal grains, bread, porridge, gruel or beer. Furthermore, the analysis shows that flowers ofAnemone nemorosa were deposited on or beneath the dead body in the cist.     

Effects of the fungal endophyte, Neotyphodium lolii, on net photosynthesis and growth rates of perennial ryegrass (Lolium perenne) are independent of In Planta endophyte concentration

• Background and Aims Neotyphodium lolii is a fungal endophyteof perennial ryegrass (Lolium perenne), improving grass fitnessthrough production of bioactive alkaloids. Neotyphodium speciescan also affect growth and physiology of their host grasses(family Poaceae, sub-family Pooideae), but little is known aboutthe mechanisms. This study examined the effect of N. lolii onnet photosynthesis (P_n) and growth rates in ryegrass genotypesdiffering in endophyte concentration in all leaf tissues. • Methods Plants from two ryegrass genotypes, Nui D andNui UIV, infected with N. lolii (E+) differing approx. 2-foldin endophyte concentration or uninfected clones thereof (E–)were grown in a controlled environment. For each genotype xendophyte treatment, plant growth rates were assessed as tilleringand leaf extension rates, and the light response of P_n, darkrespiration and transpiration measured in leaves of young (30–45d old) and old (>90 d old) plants with a single-chamber openinfrared gas-exchange system. • Key Results Neotyphodium lolii affected CO₂-limited ratesof P_n, which were approx. 17 % lower in E+ than E– plants(P < 0·05) in the young plants. Apparent photon yieldand dark respiration were unaffected by the endophyte (P >0·05). Neotyphodium lolii also decreased transpiration(P < 0·05), but only in complete darkness. There wereno endophyte effects on P_n in the old plants (P > 0·05).E+ plants grew faster immediately after replanting (P < 0·05),but had approx. 10 % lower growth rates during mid-log growth(P < 0·05) than E– plants, but there was noeffect on final plant biomass (P > 0·05). The endophyteeffects on P_n and growth tended to be more pronounced in NuiUIV, despite having a lower endophyte concentration than NuiD. • Conclusions Neotyphodium lolii affects CO₂ fixation,but not light interception and photochemistry of P_n. The impactof N. lolii on plant growth and photosynthesis is independentof endophyte concentration in the plant, suggesting that theendophyte mycelium is not simply an energy drain to the plant.However, the endophyte effects on P_n and plant growth are stronglydependent on the plant growth phase.