Spatial pattern and seed dispersal of Lithospermum caroliniense on Lake Huron sand dunes

1985 ◽  
Vol 63 (1) ◽  
pp. 125-132 ◽  
Author(s):  
Irene L. Westelaken ◽  
M. A. Maun

Studies on spatial pattern and seed dispersal of Lithospermum caroliniense (Walt.) MacMill. on Lake Huron sand dunes revealed that the ratio of pin to thrum plants was approximately 1: 1 on the south slope of the first dune ridge and slack. However, thrum plants had a higher proportion than pin plants on the crest of the dune ridge. The density of plants was highest on the south slope as compared with the other topographical zones. The spatial pattern of plants was nonrandom and plants were clustered in each of the three topographical zones. Most dispersed seeds of L. caroliniense remained within 1 m of the parent plant. The seed dispersal was not radially symmetrical around the parent plant. The steepness of the dune slope affected the dispersal distance of some propagules. Some seeds were retained on the parent, but few of these seeds were normal. About 40 to 64% of the recovered seeds contained holes in the seed coat. Eight months after marking, about one-third of the original marked seeds were still intact.

1985 ◽  
Vol 36 (6) ◽  
pp. 791 ◽  
Author(s):  
AR Harradine

After 3 years of spread from sown infestations, slender thistle density in spring was 0.12 and 4.67 plants m-2 for plots in which the ground cover was dominated by cocksfoot and annual grass species, respectively. On plots maintained free of plants other than slender thistle ('bare plots'), the corresponding density was 47.31 plants m-2. Slender thistle seed was dispersed at least 10 m from the parent plant in the first year of seeding and plants were evenly spread over the bare plots after 2 years. After 3 years, slender thistle ingress was still occurring on the other plots. The results indicate the importance of ground cover, either of living plants or of litter, in reducing seedling establishment and seed dispersal of slender thistle.


1989 ◽  
Vol 67 (4) ◽  
pp. 1267-1270 ◽  
Author(s):  
M. A. Maun

Changes in vegetation and physiography of Lake Huron shoreline were studied by recording total counts and by comparing photographs taken in 1977, 1985, and 1987. In 1977, a large number of annual and biennial plant species such as Cakile edentula, Corispermum hyssopifolium, Salsola kali, Euphorbia polygonifolia, Artemisia campestris, and Oenothera biennis were found growing in association with two perennial grasses, Calamovilfa longifolia and Andropogon scoparius. Ammophila breviligulata was absent at that time, but became abundant through establishment of ramets from rhizome fragments after the storms of 1979 and 1981. Two damaging storms, one in October 1986 and the second in April 1987, wiped out almost all of Ammophila breviligulata, leaving a few remnant shoots among clumps of Calamovilfa longifolia. Observations suggest that the low density (two shoots∙m−2) of Ammophila breviligulata tillers among Calamovilfa longifolia populations on the first dune ridge has resulted from landward extensions of plagiotropic rhizomes from the once abundant Ammophila breviligulata populations on the lakeward end of the beach.


2016 ◽  
Vol 36 (21) ◽  
Author(s):  
张博 ZHANG Bo ◽  
石子俊 SHI Zijun ◽  
陈晓宁 CHEN Xiaoning ◽  
侯祥 HOU Xiang ◽  
王京 WANG Jing ◽  
...  

2020 ◽  
Vol 12 (4) ◽  
pp. 27
Author(s):  
Michael Barnes SJ

This article considers the theme of discernment in the tradition of Ignatian spirituality emanating from the Spiritual Exercises of St Ignatius of Loyola (1491-1556), the founder of the Society of Jesus (Jesuits). After a brief introduction which addresses the central problematic of bad influences that manifest themselves as good, the article turns to the life and work of two Jesuits, the 16th C English missionary to India, Thomas Stephens and the 20th C French historian and cultural critic, Michel de Certeau. Both kept up a constant dialogue with local culture in which they sought authenticity in their response to ‘events’, whether a hideous massacre which shaped the pastoral commitment and writing of Stephens in the south of the Portuguese enclave of Goa or the 1968 student-led protests in Paris that so much affected the thinking of de Certeau. Very different in terms of personal background and contemporary experience, they both share in a tradition of discernment as a virtuous response to what both would understand as the ‘wisdom of the Spirit’ revealed in their personal interactions with ‘the other’.


2021 ◽  
Author(s):  
Pedro Jiménez-Guerrero ◽  
Nuno Ratola

AbstractThe atmospheric concentration of persistent organic pollutants (and of polycyclic aromatic hydrocarbons, PAHs, in particular) is closely related to climate change and climatic fluctuations, which are likely to influence contaminant’s transport pathways and transfer processes. Predicting how climate variability alters PAHs concentrations in the atmosphere still poses an exceptional challenge. In this sense, the main objective of this contribution is to assess the relationship between the North Atlantic Oscillation (NAO) index and the mean concentration of benzo[a]pyrene (BaP, the most studied PAH congener) in a domain covering Europe, with an emphasis on the effect of regional-scale processes. A numerical simulation for a present climate period of 30 years was performed using a regional chemistry transport model with a 25 km spatial resolution (horizontal), higher than those commonly applied. The results show an important seasonal behaviour, with a remarkable spatial pattern of difference between the north and the south of the domain. In winter, higher BaP ground levels are found during the NAO+ phase for the Mediterranean basin, while the spatial pattern of this feature (higher BaP levels during NAO+ phases) moves northwards in summer. These results show deviations up to and sometimes over 100% in the BaP mean concentrations, but statistically significant signals (p<0.1) of lower changes (20–40% variations in the signal) are found for the north of the domain in winter and for the south in summer.


2021 ◽  
Author(s):  
Loreto Martínez‐Baroja ◽  
Lorenzo Pérez‐Camacho ◽  
Pedro Villar‐Salvador ◽  
Salvador Rebollo ◽  
Alexandro B. Leverkus ◽  
...  

Prospects ◽  
1982 ◽  
Vol 7 ◽  
pp. 249-266
Author(s):  
Lewis P. Simpson

No scene in Faulkner is more compelling than the one that transpires on a “long still hot weary dead September afternoon” in Yoknapatawpha County, Mississippi, toward the end of the first decade of this century. Quentin Compson sits with Miss Rosa Coldfield in a “dim airless room” still called “the office because her father called it that,” and listens to Miss Rosa tell her version of the story of the “demon” Sutpen and his plantation, Sutpen's Hundred. As she talks “in that grim haggard amazed voice”—“vanishing into and then out of the long intervals like a stream, a trickle running from patch to patch of dried sand”—the 22-year-old Mississippi youth discovers he is hearing not Miss Rosa but the voices of “two separate Quentins.” One voice is that of the “Quentin preparing for Harvard in the South, the deep South dead since 1865 and peopled with garrulous baffled ghosts.” The other voice is that of the Quentin “who was still too young to deserve yet to be a ghost, but nevertheless having to be one for all that, since he was born and bred in the deep South the same as she [Miss Rosa] was.” The two Quentins talk “to one another in the long silence of notpeople, in notlanguage: It seems that this demon—his name was Sutpen—(Colonel Sutpen)—Colonel Sutpen. Who came out of nowhere and without warning upon the land with a band of strange niggers and built a plantation”.


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