Changes in seed dispersal processes and the potential for between-patch connectivity for an arid land daisy

Dispersal is a major and critical process in population biology that has been particularly challenging to study. Animals can have major roles in seed dispersal even in species that do not appear specifically adapted to animal-aided dispersal. This can occur by two processes: direct movement of diaspores by animals and modification of landscape characteristics by animals in ways that greatly influence dispersal. We exploited the production of large, persistent dispersal structures (seed heads, henceforth) by Erodiophyllum elderi (Asteraceae), a daisy from arid Australia, to further understand secondary dispersal. Seed head dispersal on and off animal tracks in eight E. elderi patches was monitored for 9.5 months by periodically recording the location of marked seed heads. Sites were located inside a reserve that excludes sheep but not kangaroos, and in a nearby area with both kangaroos and sheep. The distance moved and likelihood of seed head movement was higher in areas with sheep, and especially along animal tracks. There was clear evidence that seed heads were channeled down animal tracks during large rainfall events. Seed head dispersal away from patches occurred to a limited extent via their physical contact with sheep and potentially via wind dispersal. Thus, the advantages of this study system allowed us to demonstrate the two postulated effects of herbivores on dispersal via direct movement of seed heads, and two distinct indirect effects through landscape modification by herbivores from the creation of animal tracks and the denudation of vegetation.Louise M. Emmerson, José M. Facelli, Peter Chesson, Hugh Possingham, and Jemery R. Da

Patchy populations in stochastic environments: Critical number of patches for persistence

We introduce a model for the dynamics of a patchy population in a stochastic environment and derive a criterion for its persistence. This criterion is based on the geometric mean (GM) through time of the spatial-arithmetic mean of growth rates. For the population to persist, the GM has to be greater than or equal to1. The GM increases with the number of patches (because the sampling error is reduced) and decreases with both the variance and the spatial covariance of growth rates. We derive analytical expressions for the minimum number of patches (and the maximum harvesting rate) required for the persistence of the population. As the magnitude of environmental fluctuations increases, the number of patches required for persistence increases, and the fraction of individuals that can be harvested decreases. The novelty of our approach is that we focus on Malthusian local population dynamics with high dispersal and strong environmental variability from year to year. Unlike previous models of patchy populations that assume an infinite number of patches, we focus specifically on the effect that the number of patches has on population persistence. Our work is therefore directly relevant to patchily distributed organisms that are restricted to a small number of habitat patches

Endotrophic mycorrhiza and the nutrition of grape vines

The roots of grape vines collected from a number of different localities throughout the Australian continent were all infected with mycorrhiza of the vesiculararbuscular type. Similarly a range of Vitis species and hybrids and a number of V. vinifera cultivars all displayed microscopic evidence of mycorrhizal infection.The growth of vine seedlings in soils sterilized either by autoclaving or by gamma irradiation was less than in similar non-sterile soil. The vine seedlings in sterile soils were not infected with mycorrhiza while those in non sterile were. Normal growth of vine seedlings in sterile soils was obtained by inoculating them with vine roots infected with live mycorrhiza. lnoculatio!1 of vine seedlings grown in sterile soils with roots containing dead mycorrhiza (autoclaved) or with filtered soil suspensions does not stimulate their growth. The shoots of vine seedlings grown In nori-sterile soil or in sterile soils and inoculated with live mycorrhiza had a significantly higher phosphorus content than seedlings not infected with mycorrhiza.i:t is suggested that in many of the habitats in which vines are grown in Australia and in Europe vesicular-arbuscular mycorrhiza aids their nutrition

The Cannon Hall Muscat grape

The Canon Hall Muscat table grape grown for export in Western Australia is consistent with the early descriptions and the present appearance of the original  Cannon Hall Muscat vine, and is clearly the same variety. It has the diploid number of chromosomes and the use of its name for tetraploid sports of Muscat of Alexandria is not justified.Die Rebensorte Cannon Hall MuscatDie Tafeltraube Canon Hall Muscat, die in Westaustralien zum Export angebaut wird, gleicht der ursprünglichen Cannon-Hall-Muscat-Rebe, da die erstgenannte eindeutig den alten Beschreibungen und dem heutigen Aussehen der letzteren entspricht. Canon Hall Muscat ist diploid, und deshalb sollte dieser Name nicht für tetraploide Mutanten von Muscat of Alexandria gebraucht werden

Anatomical aspects of grape berry development

The anatomical development of the sultana-grape berry has been followed from anthesis to maturity on material grown under glasshouse and field conditions including field-grown clonal lines differing in final fruit size. Fresh weight, volume, berry dimensions, moisture content and dry weight were measured on whole berries. Pericarp growth was studied at the cell level. Pericarp growth is basically responsible for the overall growth of the berry and this tissue represents 64% of the mature fruit's total volume. The period required for complete berry development (approximately 100 days) falls into two major growth periods separated by a lag phase. Before the lag phase pericarp growth results partly from cell division but mainly from cell enlargement. After the lag phase pericarp growth results entirely from cell enlargement. Cell division in the pericarp ceases about one week before the lag phase. Berry size differences between clonal lines were primarily due to differences in the size of pericarp cells. Berry size differences between fruits grown in the glasshouse and in the field at Merbein were due to differences in both pericarp cell number and cell size

Use of nitrogen and potassium reserves during growth of grape vine cuttings

Single node cuttings of dormant grape vine canes were analysed to determine the relative amounts of soluble and insoluble nitrogen, and of potassium that are stored in bark and wood and in node and internode respectively. The amounts of these constituents that can be utilized for the growth of new shoot and roots were determined in experiments in which cuttings were grown in nutrient solutions which were either complete or lacking in nitrogen or potassium. When cuttings were grown for ten weeks with no added nitrogen 87 percent of the soluble nitrogen and 43 percent of the insoluble nitrogen was utilized for new growth. When cuttings were grown with an unrestricted supply of fertilizer nitrogen 82 percent of the soluble nitrogen and 20 percent of the insoluble nitrogen was utilized for new growth during the same period. Even in vines adequately supplied with fertilizer nitrogen, stored nitrogen of the cane is used preferentially for new growth.Vine cuttings grown for ten weeks with no supplemental potassium utilized 48 percent of the potassium reserve in the dormant cane for the growth of new shoot and roots. The amount translocated to the shoots was five times the amount transferred to roots. When supplemental potassium was supplied in the nutrient solution the potassium level in plant canes (initial cutting) was increased relative to that in the original cutting with equal amounts being translocated to both shoots and roots. It would appear that in contrast to nitrogen, stored potassium is not used preferentially for the growth of new shoot and roots.Die Nutzung von Stickstoff- und Kaliumreserven beim Wachstum von RebstecklingenEinaugenstecklinge von Rebenholz, das sich in der Ruhephase befand, wurden analysiert, um die relativen Mengen von löslichem und unlöslichem Stickstoff und von Kalium zu bestimmen, die im Rinden- und Holzteil bzw. Nodus und Internodium eingelagert waren. In Nährlösungen, die entweder vollständig waren oder in denen N oder K fehlten, wurden Stecklinge angezogen und an ihnen ermittelt, in welchem Ausmaß diese Elemente für das Wachstum neuer Sprosse und Wurzeln genutzt wurden.Wuchsen die Stecklinge 10 Wochen lang ohne zusätzlichen Stickstoff, so wurden 87% des löslichen und 43% des unlöslichen Stickstoffs für das neue Wachstum genutzt. Bei unbeschränktem Vorrat an Düngerstickstoff wurden 82% des löslichen und 20% des unlöslichen Stickstoffs für das neue Wachstum während derselben Periode genutzt. Selbst in Reben, die ausreichend mit Dünger-Stickstoff versorgt waren, wurde vorzugsweise der im Holz eingelagerte Stickstoff für das neue Wachstum verwendet. Rebstecklinge, die 10 Wochen lang ohne zusätzliches Kalium wuchsen, nutzten 48% der Kalium-Reserve in dem ruhenden Rebholz für die Entwicklung neuer Sprosse und Wurzeln. In die Sprosse wurde fünf mal so viel Kalium wie in die Wurzeln befördert. Nach einem Kalium-Zusatz zur Nährlösung stieg der Kaliumgehalt im Stecklingsholz (Ausgangsholz) gegenüber dem im Ausgangsstück, wobei gleiche Mengen in Sprosse und Wurzeln befördert wurden. Es hat den Anschein, als ob bei der Bildung neuer Sprosse und Wurzeln das eingelagerte Kalium - im Gegensatz zum Stickstoff - nicht bevorzugt verwertet würde

Stomata and starch in grape berries

Developing grape berries of the varieties Sultana and Cabernet Sauvignon were examined by light microscopy following plastic embedding. In ovaries and young berries stomata were detected by the presence of starch grains in their guard cells. In older berries lenticels formed beneath the stomata. Dependant on variety, lenticel numbers ranged between 2 and 16 per berry with up to half of these being associated with stomata. At anthesis most cells of the pericarp of grape berries contained starch granules. These disappeared as the berries grew, and at maturity they were present only in the epidermis and a few layers of sub-epidermal cells.Stomata und Stärke in TraubenbeerenDünnschnitte durch sich entwickelnde Traubenbeeren der Sorten Sultana und Cabernet Sauvignon wurden nach Einbettung in Kunstharz lichtmikroskopisch untersucht. An Fruchtknoten und jungen Beeren wurden die Stomata aufgrund der Stärkekörner in den Schließzellen aufgefunden. An älteren Beeren bildeten sich unter den Stomata Lenticellen. Je nach Sorte variierte die Anzahl der Lenticellen zwischen 2 und 16 pro Beere, wovon bis zur Hälfte mit Stomata vergesellschaftet sein konnten.Bei der Anthese enthielten die meisten Zellen des Perikarps Stärkekörner. Diese verschwanden mit fortschreitendem Beerenwachstum; bei der Reife kamen sie nur noch in der Epidermis und in einigen subepidermalen Zellschichten vor

Grape berry respiration: Effects of metabolic inhibitors

The rate of O2 uptake, respiratory quotient and the effects of metabolic inhibitors on respiration were followed throughout berry development of 4 varieties of Vitis vinifera L. No obvious differences in respiratory characteristics were found between seeded and seedless and between pigmented and nonpigmented grapes.Physiological differences between immature and maturing grape berries involve altered rates of respiration and a changed sensitivity to metabolic inhibitors. With development in all varieties there was a decline in O2 uptake on a fresh weight basis while R.Q. values rose to greater than unity. Dinitrophenol failed to stimulate O, uptake at any stage and the inhibition of O2 uptake caused by azide or DNP was more severe in mature fruit than in immature fruit. Cyanide stimulated O2 uptake in tissue slices from immature Sultana berries but inhibited O2 uptake in slices from more developed fruit.These data, coupled with the absence of any major alteration in the level of insoluble nitrogen per unit fresh weight of berry suggest that respiration is both quantitatively and qualitatively different in immature compared with maturing grape berries

Population Cycling in Space-Limited Organisms Subject to Density-Dependent Predation

We present a population model with density-dependent disturbance. The model is motivated by, and is illustrated with, data on the percentage of space covered by barnacles on quadrats of rock in the intertidal zone. The autocorrelation function observed indicates population cycling. This autocorrelation function is predicted qualitatively and quantitatively by the detailed model we present. The general version of the model suggests the following rules regarding cycling in space-limited communities subject to density-dependent disturbances. These rules may apply to any space-limited community where a density-dependent disturbance reduces population densities to very low levels, like fire or wind for plant communities. We propose that the period of the cycle will be approximately equal to the time it takes the community to reach a critical density plus the average time between disturbance events when the density is above that critical density. The cycling will only be clear from autocorrelation data if the growth process is relatively consistent, there is a critical density (which the sessile organism reaches and passes) above which the probability of disturbance increases rapidly, and the time to reach the critical density is at least twice the average time between disturbance events

Différents récits sur le départ des juifs du Maroc dans les années 1960-1970

Conservation outcomes are principally achieved through the protection of intact habitat or the restoration of degraded habitat. Restoration is generally considered a lower priority action than protection because protection is thought to provide superior outcomes, at lower costs, without the time delay required for restoration. Yet while it is broadly accepted that protected intact habitat safeguards more biodiversity and generates greater ecosystem services per unit area than restored habitat, conservation lacks a theory that can coherently compare the relative outcomes of the two actions. We use a dynamic landscape model to integrate these two actions into a unified conservation theory of protection and restoration. Using nonlinear benefit functions, we show that both actions are crucial components of a conservation strategy that seeks to optimise either biodiversity conservation or ecosystem services provision. In contrast to conservation orthodoxy, in some circumstances, restoration should be strongly preferred to protection. The relative priority of protection and restoration depends on their costs and also on the different time lags that are inherent to both protection and restoration. We derive a simple and easy-to-interpret heuristic that integrates these factors into a single equation that applies equally to biodiversity conservation and ecosystem service objectives. We use two examples to illustrate the theory: bird conservation in tropical rainforests and coastal defence provided by mangrove forests