Changes in the Structure of Tall Tussock Grasslands and Infestation by Species of

A plant sociological survey of tall-tussock grasslands in the Mackenzie country was repeated after an interval of 26-28 years. Changes in physiognomy of the grasslands which have been inferred from earlier studies have been found to be continuing on many sites. A noteworthy feature of most sites has been a reduction in number of indigenous species found. An increase in abundance of Hieracium pilosella or H. praealtum has occurred at most sites. About 140 species and 9 variables from 53 sites were interrelated in a direct unimodal ordination (canonical correspondence analysis). Ordination results of the 1960s and the 1989 data were compared and interpreted with respect to spread of Hieracium pilosella and H. praealtum. The dynamics of Hieracium infestation was studied within changing community structure. A distinct trend is demonstrated of increasing infestation with increasing grassland degradation.     

Interaction between Some Pasture Species and 2

Possible control options are investigated for the introduced Hieracium weeds, particular problems in South Island high country, New Zealand. In a pot experiment regression of input to output ratios of above ground biomass over successive harvests, from binary mixtures was used to determine the competitive interaction between 13 pasture species and two Hieracium species, H. pilosella and H. praealtum, in a low fertility soil. Treatments also included a factorial of presence or absence of compartments separating root and shoots of species. Species differed in their mean growth rate, relative to Hieracium species. The ranking of mean growth rate relative to H. pilosella was Trifolium repens (best), Bromus inermis, Sanguisorba minor, Festuca novaezelandiae, F. rubra, Arrhenatherum elatius, Anthoxanthum odoratum, Lotus corniculatus, Hypochoeris radicata, Trifolium repens, T. hybridum, T. medium and Astragalus cicer. Shoot partitions decreased Hieracium's interaction with white clover while root partitions increased interaction with B. inermis. However, the rates were not related to the proportion of Hieracium in the mixtures, indicating a general lack of specific competitive effects against Hieracium.     

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.     

Influence of pastoral management on plant biodiversity in a depleted short tussock grassland, Mackenzie Basin

This study investigated the effects of different management inputs (fertiliser and seed) and grazing patterns on plant biodiversity in a short tussock grassland with a strong Hieracium pilosella component. Cover abundance of vascular and non-vascular plants and environmental variables were measured in 32 10×10-m plots located in five blocks with different management treatments. Ordination of the floristic data separated the block with the highest management inputs from other blocks. Several adventive species were significantly more abundant in this block, while several native species were either absent or uncommon, but were significantly more abundant in other study blocks. H. pilosella was significantly more abundant in blocks with lower management inputs. Diversity was significantly higher in the block with the highest management inputs. The native tussock Poa colensoi had significantly greater cover abundance while Festuca novae-zelandiae tussocks were significantly taller in this block. Our results suggest that high management inputs reduce the abundance of H. pilosella and diversity of native species, but increase the abundance of other adventive species and the cover and vigour of native tussocks. Our results highlight an interesting management conundrum for short tussock grasslands. No-input management is likely to result in a decline in native biodiversity, as well as production values, as H. pilosella mats deplete soil nutrients and restrict regeneration of native species. However, input of fertiliser and adventive seeds to enhance production values, although resulting in an increase in the vigour and abundance of some native species (mainly tussocks) and a reduction in H. pilosella abundance, will also result in a decline in overall native species richness.     

Rapid short-tussock grassland decline with and without grazing, Marlborough, New Zealand

Species abundance, species richness, and ground cover were measured over 10 years on nine paired grazed and exclosure plots in short-tussock grassland in the early stages of invasion by Hieracium species. With and without grazing, H. pilosella and H. caespitosum increased markedly and H. lepidulum increased locally. In contrast, 50% of all other common species and species groups, and total, native, and exotic species richness declined significantly. Exclusion increased or had no effect on rates of increase in Hieracium species and rates of decline in short tussocks, and did not reduce rates of decline in other species. Exclusion had no effect on decline in native species richness, but mainly accelerated declines in total and exotic richness. Declines in 13 key vegetation variables were significantly predicted by increase in Hieracium abundance, suggesting competitive exclusion. With or without grazing, Hieracium species will become more dominant and other species will continue to decline. The effects of large herbivores on plant species diversity can often be predicted from site productivity. Our results indicate the need also to account for species origin, spatial scale, time, and exotic invasion.     

Changes in vegetation states in grazed and ungrazed Mackenzie Basin grasslands, New Zealand, 1990-2000

Changes in vegetation from 1990 to 2000 were examined at 10 high country localities, representing four grassland types: fescue tussock (Festuca novae-zelandiae), snow tussock (Chionochloa rigida), red tussock (C. rubra), and silver tussock (Poa cita). At each locality, three treatments were established: ambient sheep+rabbit grazing, rabbit grazing only, and no grazing. The mutivariate methods of classification and ordination were used on individual-quadrat cover data to define vegetation states and to examine transitions between them over time. Vegetation states in quadrats already dominated by Hieracium pilosella(> 50% cover) in 1990 showed little change in species composition regardless of grassland type and grazing treatment. In fescue tussock grassland, H. pilosellaincreased regardless of grazing treatment in states with low initial H. pilosellacover (< 5%), while the cover of Carex colensoi, Aira caryophyllea and Rumex acetosella decreased. In the single silver tussock locality, Poa citadecreased markedly in the ungrazed treatment as adventive species such as Dactylis glomerataand Echium vulgare increased. However, Poa citaalso decreased, probably due to drought, in the grazed treatment. Snow tussock and red tussock grassland states were more stable than those in short tussock grasslands, but there was also a general trend towards increasing H. pilosellacover in intertussock vegetation regardless of treatment. However, at one snow tussock locality, transitions from H. piloselladominated to C. rigida-dominated states occurred in ungrazed quadrats, while the reverse occurred in grazed vegetation. Implications for the management of tussock grasslands for conservation are discussed.     

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.     

Intraspecific adoption and foster feeding of fledglings in the North Island robin

We sampled soils and vegetation within and outside two sheep and rabbit exclosures, fenced in 1979, on steep sunny and shady slopes at 770 m altitude on seasonally-dry pastoral steeplands. The vegetation of sunny aspects was characterised by higher floristic diversity, annual species, and low plant cover. Here the exotic grass Anthoxanthum odoratum dominated on grazed treatments, and the exotic forb Hieracium pilosella on ungrazed. Shady aspects supported fewer, and almost entirely perennial, species. Here Hieracium pilosella dominated grazed treatments, but co-dominated with the exotic forb H. praealtum and the native grass Festuca novae-zelandiae on ungrazed treatments. There was 43% more biomass in exclosures (P < 0.01). Most of the biomass difference (4285 kg/ha) was from greater root mass (2400 kg/ha). 1385 kg/ha of the difference was from herbage and the remainder (500 kg/ha) from litter. Exclosures had 50 to 100% more Ca, Mg, K and P in the biomass (P < 0.05), but the effect on soils was limited to significantly higher concentrations of total N (P < 0.05) and exchangeable Mg (P < 0.01) in 0-7.5 cm soils. We conclude that stopping grazing for 16 years on seasonally-dry steeplands results in greater plant cover, approximately double the biomass of standing vegetation, greater biomass in roots, and more biomass nutrients relative to grazed areas. However, it does not favour native species and has little effect on soil nutrients or soil carbon. Stopping grazing alone therefore cannot be regarded as a comprehensive short- or medium-term vegetation or soil rehabilitation option.     

Chromosomes carrying meiotic avoidance loci in three apomictic eudicot Hieracium subgenus Pilosella species share structural features with two monocot apomicts

The LOSS OF APOMEIOSIS (LOA) locus is one of two dominant loci known to control apomixis in the eudicot Hieracium praealtum. LOA stimulates the differentiation of somatic aposporous initial cells after the initiation of meiosis in ovules. Aposporous initial cells undergo nuclear proliferation close to sexual megaspores, forming unreduced aposporous embryo sacs, and the sexual program ceases. LOA-linked genetic markers were used to isolate 1.2 Mb of LOA-associated DNAs from H. praealtum. Physical mapping defined the genomic region essential for LOA function between two markers, flanking 400 kb of identified sequence and central unknown sequences. Cytogenetic and sequence analyses revealed that the LOA locus is located on a single chromosome near the tip of the long arm and surrounded by extensive, abundant complex repeat and transposon sequences. Chromosomal features and LOA-linked markers are conserved in aposporous Hieracium caespitosum and Hieracium piloselloides but absent in sexual Hieracium pilosella. Their absence in apomictic Hieracium aurantiacum suggests that meiotic avoidance may have evolved independently in aposporous subgenus Pilosella species. The structure of the hemizygous chromosomal region containing the LOA locus in the three Hieracium subgenus Pilosella species resembles that of the hemizygous apospory-specific genomic regions in monocot Pennisetum squamulatum and Cenchrus ciliaris. Analyses of partial DNA sequences at these loci show no obvious conservation, indicating that they are unlikely to share a common ancestral origin. This suggests convergent evolution of repeat-rich hemizygous chromosomal regions containing apospory loci in these monocot and eudicot species, which may be required for the function and maintenance of the trait.     

Factors predisposing short-tussock grasslands to

The effects of environment and management on the composition of short-tussock grasslands and the abundance of the invasive weed Hieracium pilosella were investigated in two small catchments. Species composition and site factors were recorded on a total of 182 plots and the management history of each catchment was reviewed. H. pilosella was present on >80% of all plots, but was at an early stage of invasion in one catchment (<5% cover) and dominant in the other (25% cover). Classification and ordination revealed strong between-catchment differences in community composition that reflected differences in environment (soil fertility and rainfall), disturbance history (animal populations and burning), and the stage of invasion by H. pilosella. In both catchments H. pilosella tended to be least abundant on the wettest, driest, and most fertile soils. However, such relationships were weak. Generalised additive models and regression showed that in the earlier stage of invasion individual site factors explained less than 20% of the variation in H. pilosella cover. Topographic position and slope (both indicative of soil moisture) were the most significant combined predictors, but together explained only 32% of the variation. In the later stage of invasion individual factors explained up to 33% of the variation. Topsoil sulphur, slope, and topsoil calcium were the most significant combined predictors, but together explained only 53% of the variation. Between-catchment comparisons highlighted the inter-related roles of environment, disturbance history, geographic location, availability of H. pilosella propagules, and stage of invasion in more fully explaining the abundance of H. pilosella. Of five models that have been proposed for Hieracium invasion, the: "grassland decline" model best incorporated the inter-related factors that influence spatial and temporal variation in H. pilosella abundance in the study area. This model concentrates on identifying predisposing and trigger factors that increase the likelihood of invasion and accounts for multiple causes and interactions by specifying five key factors that influence the ability of a plant species to invade existing vegetation: environment, disturbance, vegetation structure and composition, life history attributes of the invader, and the availability of invading propagules. The model potentially provides a comprehensive framework for evaluating the causes of Hieracium invasion, targeting research effort, and developing sustainable management strategies.     

Population genetic structure of a colonising, triploid weed, Hieracium lepidulum

Understanding the breeding system and population genetic structure of invasive weed species is important for biocontrol, and contributes to our understanding of the evolutionary processes associated with invasions. Hieracium lepidulum is an invasive weed in New Zealand, colonising a diverse range of habitats including native Nothofagus forest, pine plantations, scrubland and tussock grassland. It is competing with native subalpine and alpine grassland and herbfield vegetation. H. lepidulum is a triploid, diplosporous apomict, so theoretically all seed is clonal, and there is limited potential for the creation of variation through recombination. We used intersimple sequence repeats (ISSRs) to determine the population genetic structure of New Zealand populations of H. lepidulum. ISSR analysis of five populations from two regions in the South Island demonstrated high intrapopulation genotypic diversity, and high interpopulation genetic structuring; PhiST = 0.54 over all five populations. No private alleles were found in any of the five populations, and allelic differentiation was correlated to geographic distance. Cladistic compatibility analysis indicated that both recombination and mutation were important in the creation of genotypic diversity. Our data will contribute to any biocontrol program developed for H. lepidulum. It will also be a baseline data set for future comparisons of genetic structure during the course of H. lepidulum invasions.     

The distribution and abundance of

We examined the distribution and abundance of the invasive Hieracium species (hawkweeds) in the dry grasslands of the Upper Waitaki Basin (Canterbury) and Otago, using measures of Hieracium species frequency and hawkweed cover from 301 vegetation plots. Average hawkweed cover was significantly less in Otago than Canterbury. Hawkweed cover was also lower on drier sites, with hawkweeds having less cover at lower elevation, on more xeric sites and, in Canterbury, on soils with a lower moisture holding capacity. Environmental variables (elevation, moisture index, soil class, and measures of rabbit activity and the amount of recent pasture development) explained 43% of the variation in hawkweed cover in Canterbury, but only 25% in Otago. Furthermore, having controlled for environmental differences among plots, hawkweed cover in Otago was significantly spatially autocorrelated such that plots on the same property had similar hawkweed cover, but tended to differ from plots on other properties. This pattern is consistent with the hypothesis that variation in property management influenced the degree of hawkweed infestation. However, the same pattern was not found in Canterbury. We propose a general model to explain the observed patterns. The probability that a site will be invaded by hawkweeds is a function of: (1) the suitability of the site for hawkweed establishment (a function of the environment and past management), and (2) the size of the hawkweed propagule rain. The probability of hawkweed invasion is high when one or both of these variables have high values. Following initial invasion, there will be more local propagules coming from newly established plants and hawkweed cover at a site will increase, eventually stabilising at a level predictable from the environmental conditions at the site. This model predicts that the sites most suited for hawkweed establishment would be invaded first and fill the quickest. These susceptible sites would then serve as foci, providing propagules for subsequent hawkweed spread into adjacent, less invasion prone areas. The model predicts that the initial increase in hawkweed cover at a site should be exponential, and that there should be a lag in hawkweed spread whereby less susceptible sites are invaded later or at a slower rate. Both predictions are supported by data from monitoring trials. The model can explain the lower abundance of hawkweeds, the less predictable distribution of hawkweeds in relation to environmental variables, and the significant spatial autocorrelation in hawkweed cover in Otago compared to Canterbury, if hawkweed invasion in Otago is less complete than in Canterbury.     

Rabbit bait-take from plastic bait stations

Hybridisation is a rare event in facultatively apomictic species. We report the recovery of two hybrids from reciprocal crosses between the facultatively apomictic species Hieracium praealtum and H. caespitosum. Both parents were tetraploid (2n=4x=36). H. caespitosum x H. praealtum (CR6) was a hexaploid (2n=6x=54) and an apomict. The increased ploidy number is evidence of a BIII hybrid origin, having arisen from the fusion of a reduced and an unreduced gamete. In contrast, the hybrid recovered from the reciprocal cross H. praealtum x H. caespitosum (RC4) was a tetraploid and therefore probably arose as a BII hybrid fi-em the fusion of two reduced gametes. Further evidence for this is the expression of sexuality in this plant. As apomixis in Hieracium is thought to be determined by a single dominant locus, a sexual plant is consistent with a model of inheritance where this represents the putative homozygous recessive phenotype. The formation of a sexual plant from the hybridisation of apomicts has potentially significant evolutionary implications. The formation of an interspecific BIII hybrid has not previously been recorded.     

The Changing Abundance of Moths in a Tussock Grassland, 1962- 1989, and 50-Year to 70-Year Trends

Species-rich moth faunas at two sites in a montane tussock grassland at Cass show major declines in the abundance of many common species between 1961-63 and 1987-89, furthering a 50- to 70-year trend. The recent faunal record (202 species) is quantified by a 3-point light-trapping methodology based on independence of serial samples, minimised sample variability and a posteriori data standardisation. An historical record of vegetation change is also presented, pointing to a major decline in endemic herb species with the advances of an adventive grass, Agrostis capillaris. Site differences feature in the analysis of vegetation and faunal changes. At the site with the greater loss of herbs and the 93% grass cover (a doubling in 26 years), the respective abundances of common herb- and grass-feeding moth species have declined 88% and 74% since 1961-63. A greater residual floral diversity at the other site (13% herb cover, 71% grasses) has to date favoured a lesser decline in grass-feeders (56%). Data analyses suggest that few common endemic grassland moths can survive as oligophages, most depending on feeding diversity. In the face of reducing diversity, the thrust of faunal conservation in induced Agrostis associations should be to manage the vegetation using adventive animals as allies. The evidence of the study supports and extends the author's earlier conservation guidelines.     

Declining plant species richness in the tussock grasslands of Canterbury and Otago, South Island, New Zealand

We studied vegetation change on 142 permanently marked transects spread throughout tussock grasslands of Otago and Canterbury, in areas subject to both pastoral and conservation management. The transects were established between 1982 and 1986 and remeasured between 1993 and 1999, providing a record of vegetation change at each site over an interval varying from 10 to 15 years. Each transect consisted of 50 quadrats, each 0.25m(2), in which the presence of all vascular plant species had been recorded. For each transect, we calculated the change between measurements in the mean number of species recorded per quadrat, and the change in the total number of species recorded per transect. Averaged across all transects, there was a significant decline in species richness between measurements at both the quadrat and transect scales. Small herbs (those less than or equal to2 cm tall, excluding Hieracium species) showed the greatest decline. On average, more than one quarter of the small herb species present in a quadrat at the first measurement had disappeared within 10 years. Larger herbs, ferns, rushes, sedges and grasses (excluding Chionochloa species) also declined significantly in species richness, reflecting declines in the abundance of species in these groups. Woody species richness remained constant, while species in the genera Chionochloa and Hieracium increased significantly in mean quadrat species richness, reflecting increases in the abundance of these species along transects. The rate of decline in mean quadrat species richness was unrelated to changes in the abundance of either Chionochloa or Hieracium species, or to an overall increase in total vegetation cover on transects. The rate of decline in species richness was also unrelated to the level of grazing or burning between measurements. However, the rate of decline in species richness was greater at lower elevation, on schist rock and on yellow-brown and yellow-grey soils. Our results suggest that a major compositional change is occurring in these grasslands at a rate that is independent of local variation in management and independent of the widespread invasion of these grasslands by Hieracium species.     

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.     

Restoration of mountain beech (

Fire occurs relatively frequently in beech (Nothofagus) forest in drought prone eastern areas of the South Island, New Zealand. Because beech is poorly adapted to fire, and is slow to regenerate, forest is normally replaced by scrub or grassland. Seeding was investigated as a means of restoring mountain beech (N. solandri var. cliffortioides) forest after fire destroyed 300 ha of forest at Mt. Thomas, Canterbury, in 1980. A mixture of mountain beech, Leptospermum scoparium and other small tree and shrub species was sown within a year of the fire in the presence and absence of pasture species as a cover crop, and fertiliser. Seeding of mountain beech and L. scoparium was successful, but other species were of limited success. Competition from pasture species inhibited establishment of all native species. Fertiliser increased L. scoparium plant numbers in the first year but had no other beneficial effect on establishment of native species. Leptospermum scoparium provided a dense shrub cover in plots where the native species were sown in the absence of pasture species, but mountain beech had begun to overtop the shrub canopy by 20 years after seeding. Browsing by insects or small animals in the first 2 years is suggested as the main cause of mortality in mountain beech. Mountain beech seeded at 1.4 kg/ha resulted in about 1800 saplings/ha at age 20. It is suggested that seeding the wider burn area more than 2 years after the fire would have been unsuccessful because of competition from herbaceous species, especially Agrostis capillaris, which rapidly invaded the burnt area. A strategy is outlined for establishing mountain beech over large areas when limited quantities of seed are available.     

Impacts of fine sediment addition to tussock, pasture, dairy and deer farming streams in New Zealand

1. Increased fine sediment input caused by agricultural development is expected to act as a stressor for stream ecosystems. In a large‐scale field experiment, we added fine river sand to 50‐m reaches of three second‐order streams in each of four categories of catchment development (ungrazed tussock grasslands, grazed pasture, dairying and deer farming) and measured the responses of macroinvertebrates and aquatic moss. 2. Before addition, fine sediment cover differed between land uses, being lowest in tussock (7%), intermediate in pasture (30%) and dairy (47%) and highest in deer streams (88%). Sediment addition increased cover by one land‐use category (e.g. augmented sediment cover in tussock streams was similar to pre‐existing cover in pasture streams), and cover remained high in impact reaches (compared with controls) throughout the 5‐week experiment. Sediment addition did not change concentrations of phosphate, nitrate and ammonium, which were generally highest in dairy streams and lowest in tussock streams. 3. Aquatic mosses (most common in tussock, absent in dairy and deer), invertebrate density (highest in deer, lowest in tussock), taxon richness (highest in pasture, lowest in deer) and diversity (highest in pasture and tussock, lowest in dairy and deer) all differed between land uses. Sediment addition resulted in reductions of moss cover, invertebrate taxon richness and richness of Ephemeroptera, Plecoptera and Trichoptera in impact relative to control reaches. 4. The impact of sediment addition was strongest in pasture streams where pre‐existing sediment cover was moderate and richness and diversity of the invertebrate community highest. However, even in the already sediment‐rich and species‐poor deer streams, density of one common taxon was reduced significantly by sediment addition, and another two were affected in the same way in dairy streams, the second‐most intense land use. 5. Our experiment has disentangled the impact of sediment addition from other concomitant land‐use effects that could not be reliably distinguished in previous research, which has mainly consisted of correlative studies or unrealistically small‐scale experiments.     

A hay meadow in western Norway-changes in the course of a growing season

Interference of management with groups of species/single species in a hay meadow is studied in a pilot project. Plant species are recorded 3 times during growing season from 10 permanent plots at intervals along 2 transects crossing the meadow. Hult-Sernander-Du Rietz scale is used for estimating cover, and phenological phases are estimated according to Dierschke.
The hay meadow is lightly fertilized in spring, mown once late in July and grazed lightly by calves in autumn. Until 7–8 years ago the meadow was more heavily grazed by sheep both in spring and autumn.
50 species are recorded, 44 within the permanent plots, 33 are indicators of agricultural management, 21 are indicators of traditional management, and 24 are adapted to grazing. The meadow belongs to Cardamino pratensis-Conopodietum majoris, subas-sociation campanuletosum. Luzula campestre, Campanula rotundifolia, Potentilla erecta, Hypochoeris radicata and Trifolium repens vary little in cover throughout the summer. Anthoxanthum odoratum, Leucanthemum vulgare, Trifolium pratense and Agrostis capillaris have a higher cover just before mowing than afterwards. Conopodium majus is not present above ground at all in August. Rumex acetosa and Achillea millefolium have their highest cover values in August. The time of flowering varied. At the spring analysis, Ajuga pyramidalis, Anthoxantum odoratum, Luzula campestre and Plantago lanceolata flowered. The main flowering took place at the end of June, when 20 species flowered. In August the flowers of Leontodon autumnalis, Hypochoeris radicata, Potentilla erecta and Hieracium vulgatum characterized the meadow. Several hypothesis and proposals for testing of the hypothesis are put forward.