Holcus

Abstract: Holcus lanatus is a grass that grows in humid, often waterlogged soils in temperate zones around the world. The purpose of this work was to identify fungal endophytes associated with its roots and leaves, and to describe the diversity and spatial distribution patterns found in its mycobiota. Holcus plants were sampled at 11 locations in western and northern Spain, and endophytes were isolated from leaves and roots of each plant. Morphological and molecular methods based on the ITS1-5.8SrRNA-ITS2 sequence were used for isolate identification. In total, 134 different species were identified, 77 occurred in leaves, 79 in roots, and 22 were common to both organs. The dominant species of the mycobiota were isolated from roots and leaves, and were species generally considered as multi-host endophytes. The species richness was similar in leaves and roots, but the composition of isolates from roots varied more among locations than in leaf mycobiotas, suggesting that soil characteristics may have strongly influenced the root mycobiota. Significant variations with respect to the composition of their mycobiota among different locations indicate that beta diversity is a first order factor governing the richness and distribution of the endophytic mycobiota in grasses.

Abstract: Plants of white clover Trifolium repens were grown under the canopies of three grass species, Lolium perenne, Agrostis tenuis and Holcus lanatus, and under simulated canopies of black polythene and controls were exposed to unfiltered natural radiation. The canopies were adjusted so that they transmitted equal intensities of Photosynthetically Active Radiation (P.A.R.). The ratio of red to far red radiation (ζ) was unchanged under the black polythene canopies but was reduced under canopies of Lolium and Agrostis and even more so under Holcus. The effect of canopy filtered radiation on the growth of clover was greatly to reduced internode length, mean number of nodes, the number of branched nodes and the number of rooted nodes and greatly to increase petiole length. The effect of canopies of Holcus was greater than that of the other grass species both in its effect on ζ and on the responses of the clover plant to its shade.

Abstract: SUMMARY (1) In a perennial grassland undergoing succession after the removal of domestic grazers, three natural processes could disrupt the canopy, and thus affect colonization. These are: canopy gap formation due to the death of individual bunchgrasses; soil disturbance by gophers; and grazing by native animals. (2) Species' abilities to colonize canopy gaps and gopher mounds were assessed in the field, with seed introduction experiments, for the five most cover-dominant grass species: Anthoxanthum odoratum, Holcus lanatus, Deschampsia holciformis, Rytidosperma pilosum (all perennial bunchgrasses) and Vulpia bromoides (an annual grass). (3) The effects of native grazers on colonization by the most abundant species, Anthoxanthum, were assessed, using grazer exclosures and seed introductions in annualdominated vegetation, where grazing activity was highest. (4) Colonization success was quantified as total leaf area, number of survivors and seed production, in sites where seeds of the colonist either fell naturally, or were introduced at natural densities. (5) The formation of canopy gaps by the death of individual bunchgrasses and soil disturbances by gophers strongly affected colonization success. The best colonizers were Anthoxanthum and Holcus, whose colonization success was increased 6-2500-fold by canopy gap formation, and 10-200-fold by the formation of gopher mounds. Few, small seedlings of Deschampsia and Rytidosperma survived in canopy gaps or on gopher mounds. Unlike Anthoxanthum and Holcus, Deschampsia and Rytidosperma did not reproduce in gaps or on mounds over a two-year period. (6) Vulpia colonists had higher seed production on mounds than the four perennials. Vulpia also colonized canopy gaps, but was excluded by perennial vegetation in the second year of growth in the gaps. (7) In annual-dominated vegetation, neither aboveground biomass nor colonization by Anthoxanthum was affected by excluding grazers. However, exclusion of grazers led to an increase in the cover of forbs after two years. Clipping aboveground vegetation allowed Rytidosperma to achieve dominance in sites where, under undisturbed conditions, it existed only as a suppressed understorey. All other perennials were negatively affected by clipping. (8) The species with the highest natural densities of seed rain also had the greatest perseed colonization success, even though negative density-dependent effects must have been

Abstract: 1. A range of nitrogen (N), phosphorus (P) and potassium (K) fertilizer treatments was applied for 4 years in a randomized block experiment to a species-rich hay meadow on peat soil, within the Somerset Moors and Levels Environmentally Sensitive Area. 2. The percentage composition of each species present was recorded in May and October each year on plots cut for hay, followed by further cuts of aftermath growth. The effects on species richness, diversity and dominance were analysed, and ordination techniques were used to investigate the effects of fertilizers on plant community composition. Data for mean annual biomass production are also presented. 3. Botanical results were compared with those of a concurrent experiment where aftermath growth was grazed. 4. P was more important than N in determining both biomass production and botanical change. In both cases, the effects were small when substantial amounts of N and K were applied without P, but when high rates of P were included biomass increased very significantly and species diversity was severely reduced, with Holcus lanatus, Rumex acetosa and Lolium perenne dominating. 5. Lolium perenne was not increased by N and modest rates of P in the absence of aftermath grazing, but dominated all fertilized plots when aftermath grazing was maintained. Agrostis canina came to dominate plots receiving 200 kg ha -1 of N with modest rates of P and K in the absence of aftermath grazing, but was negatively associated with N where the aftermath was grazed. 6. Trifolium pratense became very abundant where P and K were applied with nil or 25 kg ha -1 of N each year, both with and without aftermath grazing, but all legumes were suppressed at high rates of N, particularly in conjunction with high P. 7. Substantial botanical change occurred on unfertilized plots as a result of the cessation of aftermath grazing. These plots became dominated by Plantago lanceolata, with significant increases in Leontodon hispidus and L. autumnalis.