Hieracium Pilosella Research Articles

Competition among three dune species: the impact of water availability on below–ground processes

We studied competitive interactions among three species (Corynephorus canescens, Hieracium pilosella and Carex arenaria) of different early successional stages on sand dunes. Our study focused on the influence of competition and water availability on biomass allocation patterns and the plasticity of root responses. Plants were grown for one growing season in a simple additive (target–neighbour) design under low or ambient water supply. Overall competition intensity (e.g., above–and below–ground), as well as root competition alone, were compared using control plants grown without competitors. Our results show high competition intensity leading to an average target plant biomass reduction of 56 relative to controls. Competition was mostly below–ground. With increasing water availability, the competitive effect of H. pilosella on both of the other species decreased significantly. All other tested species combinations were not influenced by water availability. Soil moisture seemed to be a key factor determining the plasticity of root responses. Under limited water availability, strong competitors caused a significant decrease of response ratio (lnRR) based on root: shoot ratios for H. pilosella and C. arenaria and a decrease in lnRR based on specific root length (SRL) for C. arenaria. Under sufficient water supply, however, there was no significant effect of competition on root: shoot ratios for any of the species and only C. arenaria in competition with C. canescens showed a lower lnRR based on SRL. These water–related, species–specific changes of root morphology and allocation patterns may point to an adaptive response to competition.

Optimum reproduction and dispersal strategies of a clonal plant in a metapopulation: a simulation study with Hieracium pilosella

Clonal spread is favoured in many plants at the expense of seed production in order to expand rapidly into open habitats or to occupy space by forming dense patches. However, for the dynamics of a population in a patchy landscape seed dispersal remains important even for clonal plants. We used a spatially explicit individual-based metapopulation model to examine the consequences of two trade-offs in Hieracium pilosella L: first, between vegetative and sexual reproduction, and second, between short and far-distance dispersal of seeds. Our main question was, what are the environmental conditions that cause a mixed strategy of vegetative and sexual reproduction to be optimal. The model was parameterised with field data on local population dynamics of H. pilosella. Patch dynamics were given firstly by disturbance events that opened patches in a matrix of a clonal grass that were colonisable for H. pilosella, and secondly by the gradual disappearance of H. pilosella patches due to the expanding grass. Simulations revealed opposing selection pressures on traits determined by the two trade-offs. Vegetative reproduction is favoured by local dynamics, i.e. the need for maintenance and expansion of established populations, whereas seed production is favoured by the necessity to colonise empty habitats. Similar pressures act on the proportion of seeds dispersed over short and far distances. Optimum reproductive and dispersal strategies depended on habitat quality (determined by seedling establishment probability), the fraction of dispersed seeds, and the fraction of seeds lost on unsuitable ground. Under habitat conditions supporting moderate to low seedling establishment, between 20% and 40% of reproductive effort in H. pilosella should be devoted to sexual reproduction with at least 10% of the seeds dispersed over distances suitable to attain empty patches. We conclude that in a spatially heterogeneous landscape sexual seed production in a clonal plant is advantageous even at the expense of local vegetative growth.

Interspecific hybridization among Hieracium species in New Zealand: evidence from flow cytometry.

Hieracium pilosella: (Asteraceae) was accidentally introduced to New Zealand about 100 years ago. Since then it has become an aggressive weed, and an unexpected degree of genetic and genome size variation has been detected; features that might result from interspecies hybridization. We investigated the possibility that H. pilosella has hybridized with related taxa. Of the four other subgenus Pilosella species introduced to New Zealand, H. praealtum is the most abundant and, on morphological and distributional evidence, most likely to be the other parent. Flow cytometry was used to estimate relative genome size for 156 Hieracium plants collected from the wild. Plants assigned to either parental or hybrid morphotypes were found to comprise tetraploid and pentaploid individuals using genome size measurements, and this was confirmed with direct mitotic chromosome counts for a subset of plants. The haploid DNA content of H. praealtum was approximately 22% larger than that of H. pilosella. Putative hybrids that were tetraploid had mean genome sizes equivalent to two H. pilosella and two H. praealtum haploid chromosome sets, implying they were hybrids arising from the fertilization of two reduced gametes. Similar results were obtained from tetraploid hybrids produced by controlled pollination. However, the majority of field hybrids were pentaploid with a genome size equivalent to four H. pilosella and one H. praealtum haploid chromosome sets. We infer that these are not first-generation hybrids but represent successful backcrossing with H. pilosella and/or hybrid-hybrid crossing, and that sexual tetraploid hybrids have been the parents. We note that populations putatively of H. pilosella often comprise apomictic pentaploid hybrids. Significantly, our data indicate the emergence of sexual hybrids that provide further opportunity for gene flow among taxa in this complex.

Reproductive strategy and population variability in the facultative apomict Hieracium pilosella (Asteraceae)

Molecular studies of apomictic plant species often detect more genotypic variation than predicted from their assumed reproductive mode. The two most commonly invoked mechanisms to explain these high levels of variation are recombination, via facultative sexuality, and mutation. The potential for sexual reproduction in the facultative apomict Hieracium pilosella (Asteraceae) was determined at three field sites by artificially pollinating with the closely related, but morphologically distinct, H. aurantiacum. The level of genotypic variation at the three sites was recorded using inter-simple sequence repeats (ISSRs). There was a significant, positive relationship between the measured potential for sexual reproduction and population genotypic variability, indicating that sex has played a role in the structuring of these populations; however, a causal relationship cannot be stated because of the use of regression. We also applied the recently developed method of compatibility analysis. Compatibility analysis can determine, using the occurrence of "character incompatibilities," whether patterns of variation observed in populations are most parsimoniously explained by mutation or recombination. Compatibility analysis also indicated that sexual reproduction had played a role in generating genotypic diversity in these populations. Combining these different types of data may give a greater understanding of the potential for the generation of genotypic diversity in facultative apomictic populations.

Chloroplast DNA diversity of Hieracium Pilosella (Asteraceae) introduced to New Zealand: reticulation, hybridization, and invasion

The European hawkweed Hieracium pilosella is a successful invader and a troublesome weed in New Zealand. The systematics of the genus Hieracium is extremely complex and contentious, probably due to recent speciation, hybridization, polyploidy, and diverse reproductive strategies. In the first chloroplast DNA survey of the group, we sequenced 285 plants (including H. pilosella and 12 other species of subgenus Pilosella) from New Zealand and Europe for 900 bp of trnL-trnF. Eleven haplotypes were identified with much sharing among species. Three haplotypes (A, D, G) were found in seven, three, and four species, respectively, but two species (H. lactucella and H. auricula) had single, private haplotypes. Our cpDNA data for subgenus Pilosella are consistent with the group's having incomplete lineage sorting and/or recent reticulate evolution. Six haplotypes were identified in H. pilosella, four of these unique to this taxon in our sample. In New Zealand, haplotype A was common and occurred in plants of different ploidy (i.e., 4×, 5×, 6×), whereas haplotypes C, B, and M were restricted to 4×, 5×, and 6× plants, respectively. The distribution of haplotype variation suggests that some or all of the H. pilosella seeds accidentally introduced into New Zealand probably came from east Europe rather than the United Kingdom and that a minimum of four lineages were introduced. Within New Zealand, hybridization of H. pilosella with a related taxon (probably H. praealtum) has occurred at least three times, involving both obligate sexual tetraploids and facultative apomictic pentaploids of H. pilosella.

Temporal responses over 30 years to removal of grazing from a mid‐altitude snow tussock grassland reserve, Lammerlaw Ecological Region, New Zealand

Monitoring of five representative sites in the 144‐ha Black Rock Scientific Reserve of mid‐altitude (690–770 m) narrow‐leaved snow tussock (Chionochloa rigida) grassland over the 30 years since its establishment has revealed, contrary to an early prediction, significant increases in both cover and height of snow tussock. By contrast, co‐dominant shrubs have shown only a slight, generally nonsignificant gain, with Dracophyllum longifolium rather than the predicted Hebe odora as the only significant increaser. Several sub‐dominant shrubs (Coprosma cheesemanii, Leucopogon colensoi, Gaultheria macro stigma) plus some mosses (Hypnum cupressiforme) and lichens (Cladia retipora, Stereocaulon ramulosum) have increased significantly while some rosette herbs (Brachyglottis bellidioides, Oreomyrrhis colensoi, Plantago novae‐zelandiae, and the adventive Hypochoeris radicata) have declined. The generally aggressive exotic flatweed Hieracium pilosella remains as yet a minor component. These changes in subcanopy cover probably reflect the obvious increase in shade and dampness of the micro‐habitat. The height‐frequency sampling indicates an overall decline in vascular species diversity since losses have significantly exceeded gains over the 30‐year period of monitoring. Our results confirm that low‐ to mid‐altitude snow tussock grassland ecosystems can be sustained for at least several decades, for their conservation, landscape, and water yield values. We question the interpretation of a general lack of tussock grassland below treeline in immediate pre‐human times, and its widespread downslope replacement of forest following Polynesian fires, since it is at variance with the known ecology of the dominant grass species, evidence from relevant pollen records, and results from the present study. Rather, we interpret the available evidence as indicative of succession to a vegetation mosaic of non‐woody and woody dominants related to physiography and disturbance, as currently being debated for north‐western Europe. We hypothesise that such a mosaic would more closely reflect the pre‐human situation below treeline which would have been moulded by periodic fire and avian and invertebrate herbivory, in the absence of land mammals.

Life history and description of the preimaginal stages of <i>Scythris siccella</i> (Zeller, 1839) (Lepidoptera: Scythrididae)

Egg, second, and last instar larvae, as well as pupa of Scythris siccella (Zeller, 1839) are described and illustrated in detail. Life history of this scythridid species is also presented. The eggs are laid singly or in small groups. The larva mines leaves of Hieracium pilosella and Rumex acetosella; it lives in sandcovered silken tubes attached to food plant. The full-grown larva is 8–10 mm long, and pupation takes place in a dense cocoon encrusted with grains of sand. The adults fly in one generation, from the end of May to the end of July. In Poland, Scythris siccella (Zeller) inhabits open, lowland dunes with xerothermic vegetation.

The discrepancy between food plant preferance and suitability in the moth <i>Dysauxes ancilla</i>

Abstract. Growth responses to and preference for different food plants were studied in larvae of the geographically isolated Swedish population of the moth Dysauxes ancilla. Laboratory rearing of D. ancilla larvae showed that, besides a mixed diet, four species from different plant families supported development to the adult moth. There was a significant suitability order among these species according to higher female adult weight and shorter development time; mixed diet and Calluna vulgaris > Hieracium pilosella > Thymus serpyllum > Brachytecium sp. However, these species were not top ranked in preference trials by the larvae. Instead larvae preferred Rumex acetosella, a plant that did not support development to adult moth as a single food source. This discrepancy between larval performance and preference may be explained by advantages from food mixing by the polyphagous larvae; an improved nutrient balance, a possibility of diluting toxic secondary substances and of switching foods to fit changing physiological needs. In Nature other factors such as microclimatic conditions, predators and parasitoids probably also influence the foraging behaviour of D. ancilla larvae.

A Case of Reversal: The Evolution and Maintenance of Sexuals from Parthenogenetic Clones inHieracium pilosella

We provide evidence for the origin of sexual individuals from parthenogenetic progenitors in natural populations. We demonstrate that this reversal has occurred independently in three geographically separated populations of the Asteraceous polyploid, Hieracium pilosella. We used chromosome counts and flow cytometry to determine ploidy and crossing experiments and flow cytometry to confirm sexuality. Inter–simple sequence repeat and allozyme markers demonstrated that the sexuals at each site were more closely related to their parthenogenetic neighbors than to sexuals at other sites. The same markers were used to estimate levels of ramet diversity, which were equally high among the parthenogens and sexuals. The observation that sexuals were always tetraploid is possibly explained by their having arisen through a rare sexual event, the fusion of two reduced (2x) gametes from pentaploid, facultatively apomictic parents. Such a reversal from almost total clonality to obligate sexual reproduction is unusual, an...

Predicting the Impact of the Biocontrol Agent Aulacidea subterminalis (Cynipidae) on Growth of Hieracium pilosella (Asteraceae) under Differing Environmental Conditions in New Zealand

A gall wasp, Aulacidea subterminalis, was released into the field in New Zealand in 1999 for biocontrol of the grassland weed Hieracium pilosella. To predict its likely impact in the field, the effect of the gall wasp on plant growth was measured under stress-free conditions in a shade house trial with potted plants. Plants with galls showed a reduction in stolon length of 75%. They had slightly lower total dry matter and reduced root weight. In a glasshouse experiment to measure the impact of water stress, nutrient stress, and plant competition on growth of H. pilosella and performance of the gall wasp, the number and mean diameter of gall clusters were not significantly different between treatment and control plants. However, galled plants produced more, but shorter, stolons in all stress treatments, and stolons that were more branched in nutrient- and water-stressed plants, than ungalled plants. Under the plant competition treatment, total stolon length relative to biomass was greater with, than without, wasps, indicating that stolons were thinner. Galling by A. subterminalis is likely to reduce vegetative reproduction of H. pilosella whether or not the plants are stressed, indicating that the wasp may be a successful biocontrol agent.

On the economy and safety of hollow non‐septate peduncles

We examined the allometry and mechanical properties of the peduncles of Hieracium pilosella and other species in the Asteraceae (H. aurantiacum, Taraxicum officinale, Tragopogon pratensi) to evaluate the hypothesis that tapered, tubular, and non-septate peduncles optimize the trade-offs among stem biomass allocation, elevating flowers and thus their wind-dispersed fruits, and the requirement for a factor of safety against mechanical failure. This hypothesis was evaluated by comparing peduncle morphometry (e.g., biomass M(s), floral biomass M(f), and length L) and mechanical properties (e.g., bending rigidity EI) for populations growing in windy and wind-sheltered sites as well as transplants between sites. Regardless of ambient wind speeds, M(s) ∝ L(4/3) and EI ∝ L(11/4) ∝ M(s)(5/3), whereas M(f) /M(s) ∝ L(-1.15), i.e., peduncles disproportionately increase in their biomass as they increase in length, but mechanically support a disproportionately smaller floral biomass relative to their biomass. Calculations show that the tall peduncles from wind-sheltered sites have a larger fruit dispersal range and a lower factor of safety than the shorter peduncles produced in open sites. These and other observations are interpreted to indicate that tubular peduncles enhance relative fitness in terms of propagule dispersal (but not propagule number per stem) while maintaining a sufficient factor of safety against mechanical failure.

Population dynamics in mature stands of Hieracium pilosella in New Zealand

The dynamics of a mature population of Hieracium pilosella under four different treatments (± irrigation, ± fertiliser, ± defoliation, and ± fungicide & insecticide, in a full factorial design) were compared in the Mackenzie Basin, New Zealand. H. pilosella had been growing at the site for at least 30 years. Recorded variables included rosette density, inflorescence and stolon production, recruitment and mortality, and plant cover. The population appears to be regulated through density-dependent mortality interacting with density-independent reproduction. In the treated plots, irrigation and fertiliser had the greatest effects, increasing both the proportion of established rosettes producing stolons and stolon length. Irrigation also increased the likelihood of a daughter rosette becoming reproductive and decreased inflorescence abortion. Fertiliser increased the probability of an established rosette reproducing and the number of daughter rosettes produced. In unmanipulated plots H. pilosella appeared to be at or near an equilibrium density of ca. 3200 rosettes m−2, but over longer time scales the low reproductive rates shown in this study may presage slow population decline due to plant-induced environmental degradation.

Briza media L.

A loosely tufted perennial with short rhizomes from which arise vegetative shoots. Culms 15-60 (-100) cm high, slender, erect, 2-3-noded, solitary, smooth. Leaves with dull glaucous to mid-green adaxial and abaxial surfaces, hairless; blades usually 4-20 (-28) cm long, 2-4 (-7) mm wide, with minute acroscopic teeth on the margins, with a slender boat-shaped tip; ribs numerous, closely packed, less obvious on the abaxial surface; sheaths smooth, entire, soon splitting, dark reddish-brown at base; ligules up to 1.5 mm long, membranous, blunt with irregular margins. Culm leaves 3 or 4, uppermost with long sheaths. Panicles 410 (-18) cm long, lax, roughly pyramidal, with up to 20 branches, and up to 60 spikelets, sparsely divided, spreading, with scabrous hair-like pedicels 5-20 (-50) mm long and slightly thickened below the spikelets. Spikelets 4-7 mm long and wide, loosely scattered and drooping, broadly elliptic to broadly ovate, laterally compressed, generally purplish-brown, usually breaking up at maturity beneath the lemmas but many spikelets remaining undispersed on the branches and shed from the panicle intact, 4-9 (-12)-flowered. Glumes slightly unequal, deeply concave, hooded at the apex, boat-shaped, 2.5-3.5 mm long, with 3-5 veins, firmly membranous, dull-purple with white and shiny margins. Lemmas 3.7-4.1 mm, strongly cordate at the base, bluntly keeled in the lower half, closely overlapping, rounded on the back, with 7-9 veins, variegated purple and green, with hyaline margin. Paleas flat, thin, almost as long as the lemma, with two keels, narrowly winged. Lodicules 2, linear-lanceolate, acute. Grain enclosed within the papery lemma and palea, c. 2 mm long, rounded on the back, flattened on the front; mean oven-dry weight 0.53 mg. The root system is a dense mat of whitish fibrous roots. The primary roots are up to 1 mm in diameter and are largely unbranched, but there is a dense network of branching secondary roots. The root mass is fairly vertical with an average root length of c. 40 cm. The species produces pale brown rhizomes up to 13 cm long and 1.5 mm in diameter. Native. Subspecies media occurs throughout the range; subspecies elatior (Sibth. & Sm.) Rohlena occurs in south-east Europe.

Sexual and vegetative reproduction of Hieracium pilosella L. under competition and disturbance: a grid-based simulation model.

We used a spatially explicit simulation model to examine the relative importance of vegetative and sexual reproduction in Hieracium pilosella L. Based on an understanding of the complex life cycle of this species and on data from in situ population dynamics in a calcareous grassland in NW Switzerland, we simulated growth and the relative contribution of clonal reproduction by stolons and reproduction by seeds across a gradient of increasing soil fertility. Competition by a clonal grass resulted in nearly complete exclusion of H. pilosella from the more fertile part of the simulation plot. Under low soil fertility, when grass could not survive, H. pilosella largely persisted by vegetatively produced rosettes. This pattern of a sharp separation of both species was shifted slightly in favour of H. pilosella by introducing random disturbances. Only by adding: (1) long-distance seed dispersal, and (2) facilitation of seedling establishment in the vicinity of grass tussocks in vegetation gaps was a more realistic representation of field observations realised, with rosettes of H. pilosella grown from seeds occasionally distributed within dense grass vegetation. Phenotypic plasticity of stolon length was a decisive factor for the maintenance of H. pilosella populations. We conclude that a mixed strategy of clonal growth and reproduction by seeds in H. pilosella is necessary to maintain populations of this species in the presence of high interspecific competition and a shortage of open space.

Host range of Cheilosia urbana (Meigen) and Cheilosia psilophthalma (Becker) (Diptera: Syrphidae), candidates for the biological control of invasive alien hawkweeds (Hieracium spp., Asteraceae) in New Zealand

Four Eurasian Hieracium spp. (Asteraceae) are noxious weeds in New Zealand and targets for biological control. Cheilosia urbana (Meigen) and Cheilosia psilophthalma (Becker) (Diptera, Syrphidae) are univoltine, sympatric hoverflies from Central Europe which have been screened to determine their safety as biological control agents. Females of both species oviposit on Hieracium pilosella L. rosettes in April and May but their larvae occupy different feeding niches. C. urbana larvae move into the soil where they feed externally on the roots, making small holes, whereas C. psilophthalma larvae remain on and feed on the aboveground plant parts. During no-choice larval-transfer tests, neonate C. urbana larvae fed and completed development to the adult stage on eight of nine Hieracium spp. tested, whereas C. psilophthalma larvae completed development to the adult stage on all nine Hieracium spp. tested. Neither C. urbana nor C. psilophthalma developed on species from genera other than Hieracium. A successful method was developed to conduct single-choice oviposition tests with both species. Two critical test plant species outside the genus Hieracium were each offered to gravid C. urbana females in the presence of the target weed H. pilosella but none of the nontarget test plants were accepted for oviposition. The screening results indicated that both species of hoverflies are sufficiently host specific for release in New Zealand where no native Hieracium species exist. Invasive hawkweeds of Eurasian origin are also considered serious weeds in North and South Americas, where in contrast to the situation in New Zealand, native Hieracium spp. are also present. Thus, additional host specificity tests with native Hieracium species and other American Asteraceae will be necessary to determine the experimental host range of both hoverflies within the genus Hieracium and to examine whether other plant species would be at risk.

Alluvial grasslands of Canterbury and Marlborough, eastern South Island, New Zealand: Vegetation patterns and long‐term change

Grasslands of alluvial systems were studied in 35 valleys from the Mackenzie Basin in Canterbury to Marlborough in eastern South Island, New Zealand, to describe the relationship between environmental factors and vegetation types and gradients. Pastoral modification, represented by decreasing percentage of native species, was the primary determinant of the overall vegetation pattern. The least modified vegetation types, retaining native tussock canopies, were recorded on low pH, organic‐rich, phosphate‐poor soils, in higher‐rainfall reaches of valleys experiencing low summer temperatures. Secondary vegetation gradients, from Festuca matthewsii and red tussock grasslands to Festuca novae‐zelandiae grasslands, corresponded with trends from mesic intermontane to drier, more continental rainshadow climates, and from low‐lying floodplains to elevated terraces. The effects of grazing, and of the cessation of grazing, were examined at fenceline and exclosure sites. The abundance and abundance fraction of native species had decreased over time with grazing at all fenceline sites, and native species richness and native richness fraction had decreased at two sites. Grazing‐exclosed vegetation had higher native biomass than adjacent grazed vegetation at three sites, and higher percentages of native species richness at three sites. The presence or absence of native tussock grasses at the time of exclosure may be critical for post‐pastoral retention or recovery of native biomass. Trends along climate and modification gradients in the occurrence of three major introduced species were compared between valley groups. Agrostis capillaris appears to have reached its potential environmental range in most of the studied valleys. However, Festuca rubra and Hieracium pilosella may not yet occupy their potential range in the North and South Hurunui valleys in Canterbury, and in the Ahuriri, Hopkins, and Dobson valleys in the Mackenzie region.

‘Thawing’ of ‘frozen’ variation in an adventive, facultatively apomictic, clonal weed

AbstractRadiation of adventive, sexually reproducing organisms into a new environment has been well documented, but less is understood about the patterns and processes of geographical radiation in adventive species with uniparental reproduction (parthenogenesis or apomixis), usually associated with ‘frozen’ variation within maternal lineages. In this study we have used Pilosella officinarum to test the hypothesis that sexual reproduction becomes important in the radiation of adventive facultatively apomictic species. Within its native Europe P. officinarum is an extremely variable species, with eight subspecies and a range of ploidy levels. Pentaploids are always apomictic. However, early chromosome analyses of New Zealand adventive populations, carried out during the 1980s, discovered only pentaploid, apomictic clones. Similar observations were made in an early 1990s study of the same sites. Since then, a range of ploidy levels, including aneuploids, and a plethora of morphological variation, has been recorded. In this paper, we use a combination of image analysis and chromosome counts to show that sexual reproduction has become an important avenue for adaptive radiation in New Zealand populations of P. officinarum. Current populations probably comprise complex among‐subspecies hybrids, and possibly among‐species hybrids, which are at least partially capable of sexual reproduction and various forms of back‐crossing. Somatic mutation may also play an important role in creating morphological variation. DNA fingerprinting did not contribute to this study because this technique failed to distinguish between morphological types observed in the field.

Sexual reproduction in field populations of the facultative apomict, Hieracium pilosella

Hand pollination under New Zealand field conditions of capitula from each of six populations of Hieracium pilosella (maternal parent) with the closely related but morphologically distinct H. aurantiacum produced F1 hybrids in every case. The frequency of F1 hybrid offspring among the populations ranged from 0.2 to 21.6%. Involucral bract characteristics, leaf shape, and petal colour were the most useful characters for identifying hybrid progeny. Most F1 hybrids were able to set seed by apomixis, but a sexual individual was also recovered. The discovery that both tetraploid and pentaploid H. pilosella can reproduce sexually, following artificial pollination under field conditions, in New Zealand has implications for the bio‐control of this species. Sexually reproducing plants are more likely to evolve resistance to host‐specific bio‐control agents than are apomicts. These results are part of a larger, ongoing research programme investigating the role of the environment in the expression of apomixis.

Sustainability of New Zealand high‐country pastures under contrasting development inputs. 7. Environmental gradients, plant species selection, and diversity

The change in plant species relative abundance under different fertiliser and management inputs over 19 years is reported for two grazed multiple‐species trials on a Pukaki/Tekapo high‐country soil. One trial was 30 combinations of 5 superphosphate rates (0–500 kg ha‐1 yr‐1) × 3 stocking rates × 2 stocking methods, and the second was 31 combinations of S, P (0–100 kg ha‐1 yr‐1), and micronutrient fertilisers. Both were overdrilled with a 25‐species pasture mixture. There was rapid initial separation in relative abundance of species, principally according to fertiliser level. Main features were Hieracium pilosella remaining dominant in the absence of fertiliser; the initial success of Trifolium hybridum; the dominance and long‐term persistence of Lupinus polyphyllus at low fertiliser inputs; the transition to Dactylis glomerata dominance at high fertiliser inputs following a legume phase, in the middle years; the slow vegetative increase of Trifolium ambiguum to become dominant in most of the moderate and high fertiliser treatments in the second decade; and the increase of Bromus tectorum in later years. Species distributions were predominately determined by P fertiliser rates, or P by S fertiliser interactions. The effects of different grazing managements on late spring pasture composition were small during the first decade but increased over time, with the principal changes under moderate to high rate set‐stocking. Diversity considerations showed that the number of vascular plants in a plot (n), or their proportional distribution in biomass (k diversity), gave only a weak and inconsistent correlation with secondary production (mean sheep carrying capacity), or its stability (CV of annual grazing capacity), after fertiliser and grazing management treatment effects were considered. The only significant trend was in one trial where production tended to be inversely related to the number of plant species (2.2% decrease per species).

Factors influencing abundance of butterflies and burnet moths in the uncultivated habitats of an organic farm in Denmark

Biotic and abiotic factors causing aggregations of butterflies were investigated in a variety of uncultivated habitats on an organic farm in Denmark. By combining the method of butterfly transect counting with multiple regression analysis, environmental and floral variables influencing butterfly abundance in linear and non-linear uncultivated habitats were identified. Dependent variables were: butterfly totals, Thymelicus spp. (mainly T. lineola), Aphantopus hyperantus, Maniola jurtina, Pieris rapae/napi and four mobility groups. In linear habitats, environmental variables of major importance were: insolation, width of non-crop ground vegetation and abundance of nectar sources, while in non-linear habitats these were: larval host plants, presence of stream and degree of grazing. Among the preferred nectar sources were: Knautia arvensis, Trifolium pratense, Cirsium spp. and Hieracium pilosella. Most butterfly species had significantly higher abundances in non-linear habitats compared to linear habitats. The impact of different environmental and floral variables on the butterfly fauna is discussed, emphasizing the major importance of certain habitat types and characteristics for the butterfly species inhabiting uncultivated habitats surrounded by cultivated fields.