Density-dependent effect of allelopathy on germination and seedling emergence in two Ipomoea species

Background Density in inter and intraspecific plant-plant interactions affects the action modes of allelopathy (autotoxicity, negative and positive allelopathy). Some seeds exude compounds that inhibit the germination of others. Ipomoea murucoides and I. pauciflora are sympatric tree species that form patches at the local scale where one or the other dominates, possibly due to allelopathy in the seeds. The objective of this study was to determine the possible density-dependence of the allelopathic effect among seeds of these species through the measure of seed germination and seedling emergence. Methods In both species, allelopathy was measured as: a) germination in mixed sowing of both species at different proportions, b) germination in single-species trials at different densities after adding seed extracts of both species, and c) seedling emergence in seed mixtures of both species sown at different proportions beneath canopies of the two Ipomoea species. Results Seed germination of I. murucoides was increased by the presence of I. pauciflora and diminished at higher densities of its own seeds; however, seed germination of I. pauciflora was not affected by the presence of I. murucoides seeds. The addition of extracts (either from conspecifics or congeneric) diminished the germination of both species and at higher seed densities the germination was lower. Seedling emergence did not depend on the species under which the seeds were sown nor on the density of the seeds. Conclusions The germination experiments evidenced positive allelopathy and/or autotoxicity, while there was no evidence of allelopathic effects in seedling emergence. The allelopathic activity is reported in the seeds of these species for the first time.

Attractiveness of possum apple baits to native birds and honey bees

This study investigated the potential risks of using 1080 apple bait for possum control on nontarget species Trials were conducted using captive native birds at Orana Park and honeybees (Apis mellifera) at Halswell to determine whether these species would feed on nonpoisonous apple baits Bird species were kaka (Nestor meridionalis) kea (Nestor notabilis) kakariki (Cyanoramphus sp) silvereye (Zosterops lateralis) weka (Gallirallus australis) and kereru (Hemiphaga novaeseelandiae) Kaka kea kakariki and silvereye preferred to feed on apple bait over carrot bait spending 74100 of their feeding time on the apple bait Honeybees were not attracted to the apple bait It is concluded that there could be a greater risk to native birds when apple baits are used for possum control compared to the risk associated with using carrot bait Consequently it is recommended that aerial application of apple should not be undertaken and that apple baits should be used in bait stations only

SOME OBSERVATIONS OF PASTURE MANAGEMENT EFFECTS ON GRASS GRUB, PORINA AND EARTHWORM POPULATIONS

Changes in management practices will automatically alter the equilibrium between organisms making up the pasture ecosystem with results not necessarily beneficial to the economic production of the system. Indications of these interactions were observed and monitored in pasture management pasture species trials at Palmerston North. Grass grub attack developed more rapidly, and populations reached higher levels under rotational grazing than set stocking. Porina caterpillar populations tended to show the reverse with higher populations under set stocking than rotational grazing. Earthworm populations were higher under set stocking with a greater proportion of burrowing types, compared to rotational grazing which favoured more of the surface feeding species. These changes are discussed in terms of differences in pasture structure and defoliation patterns affecting microclimate and food supplies for the survival of these organisms. Keywords: Pasture management, rotational grazing, set stocktng, grass grub, porina, earthworms, pasture structure, pasture biomass.

Species Trials for Biomass Production on Abandoned Farmland

As part of a nationwide study of the potential for woody crops to supply biomass for energy use, we evaluated seven hardwood tree species and six hybrid poplar clones on four different sites in Vermont, with three fertilizer treatments on some sites. Not all species were evaluated on all sites. Plots containing 25 trees were replicated three or four times at each site. Trees were planted at a spacing of 0.6 x 0.6 m or 0.9 x 0.9 m and grown for 3 years. The application of fertilizer did have significant effect on height, diameter, and stem weight. Species with high yields (about 16 oven-dry t/ha/year) included four of the hybrid poplars. Silver maple, black locust, and the other two hybrid poplars yielded about 10 oven-dry t/ha/year. Based on growth alone, these species and clones were recommended for short-rotation intensive culture in areas with similar climate and growing sites. North J. Appl. For. 2:43-47, June 1985.

SPECIES TRIALS WITH OILSEED PLANTS: II. CAMELINA

Camelina, a member of the mustard family, exceeded flax and rape in yield of seed per acre at Ottawa, Ontario, and at Fort Vermilion, Alberta. The oil content of the 10 varieties in the test ranged from 34.3 to 38.7 per cent at Ottawa and from 37.1 to 42.0 per cent at Fort Vermilion. The average fatty acid composition in percentage of methyl esters was: palmitate 5.0; stearate 2.1; behenic 1.7; palmitoleic, trace; oleic 14.8; linoleic 16.4; linolenic 36.1; eicosenoic 17.5; eicosadienoic 2.3; erucic 3.7. The seed contained 33.1 per cent protein, 9.6 per cent crude fiber, only a trace of isothiocyanate, and no thiooxazolidone.Camelina matured 3 to 4 weeks earlier than flax. This is a valuable characteristic for northern areas as it would prevent damage by early fall frost and would permit extending the northern limits of the oilseed-producing area.