Geology topics
J. A. Allen
Publications and source records attributed to J. A. Allen.
Intraspecific variation in the response of Taxodium distichum seedlings to salinity
Seedlings of 15 open-pollinated families of baldcypress (Taxodium distichum) were tested for their tolerance to combined salinty and flooding stress. Ten of the families were from coastal locations in Louisiana or Alabama, USA, that were slightly brackish. The other families were from locations not affected by saltwater intrusion. Five salinity levels were investigated--0,2,4,6, and 8 g -1 artificial seawater -- all with flooding to approximately 5 cm above the soil surface. Survival, height growth, leaf area and total biomass all declined with increasing salinity. Significant variation was found among salinity levels, families, and salinity x family interactions for leaf area and total biomass. Two tolerance indices were also developed to compare family response with salinity. In general, families from brackish sources had greater total biomass, leaf area, and tolerance index values than families from freshwater sources at the higher slainity levels. A selection and breeding program designed to develop moderately salt-tolerant baldcypress seedlings for use in wetland restoration projects and other applications appears to be well-justified.
Prospects for increasing the salt tolerance of forest trees: A review
Three major themes related to the improvement of salt tolerance in forest tree species are examined. First, evidence demonstrating that substantial intraspecific variation in salt tolerance exists in many species is presented. This evidence is important because it suggests that efforts to improve salt tolerance through conventional plant breeding techniques are justified. Second, the physiological and genetic mechanisms controlling salt tolerance are discussed briefly. Although salt tolerance involves the integration of numerous physiological processes, there is considerable evidence that differences in the ability to exclude Na + and Cl - from leaves are the most important factors underlying intraspecific differences in tolerance . It is also becoming apparent that, although salt tolerance is a multigenic trait, major genes play an important role. Third, progress to date in improving salt tolerance of forest tree species is assessed. Compared with agricultural crops, relatively little progress has been made with either conventional or biotechnological methods, but field trials designed to test clones identified as salt tolerant in screening trials are underway now in several countries. We conclude that there is justification for cautious optimism about the prospects for improving salt tolerance in forest tree species. © 1994 Heron Publishing.
Control of pest species: Tree shelters help protect seedlings from nutria
Various methods of nutria preventative techniques were tested in attempts to curb the loss of seedlings due to nutria capturing. The results of testing possibly indicate that tree shelters have real potential for use in forest restoration projects on sites with moderate nutria populations. Tree shelters may even prove effective on sites with high nutria populations, as long as alternative food supplies are available.
Establishment of bottomland oak plantations on the Yazoo National Wildlife Refuge complex
Stocking, height and diameter growth, and invasion of both herbaceous and woody plant species are reported for 5 direct seeded and 5 planted seedling stands of bottomland oaks, all of which were between 4 and 8 years old. Stocking was generally higher in the planted seedling stands. Both height and diameter growth were substantially higher in the planted seedling stands. Low stocking and poor growth, especially for the direct seeded stands, was associated with medium-textured soils and a heavy cover of Johnson grass ( Sorghum halepense ) and goldenrod ( Solidago altissima ). Invasion of woody species was heavily dominated by light-seeded species, and was highest in stands close to mature trees.
Fuelwood production and use in rural Swaziland: a case-study of two communities
Information of fuelwood consumption and the local production of wood was collected in two small rural communities in Swaziland. Fuelwood consumption was estimated to be 0.77 t persona??1 yeara??1 in one community (Sigombeni), and 0.63 t persona??1 in the other (Bhekinkhosi). Bhekinkhosi was found to be experiencing a significant fuelwood production/consumption deficit and it expected that Sigombeni will also experience fuelwood deficits by 1990. Individual farm woodlots provided the largest proportion of annual woody biomass production in both areas, accounting for 45% of all profuction in Sigombeni and 73% in Bhekinkhosi. Thirty-seven percent of all farms in Sigombeni and 23% in Bhekinkhosi had woodlots. Virtually all these woodlots consisted primarily of black or green wattle and were established by direct seeding. Two types of community woodlots were identified a?? those established when the area was a private farm and those established with government assistance. The first type of community woodlots was found only in Sigombeni, where it accounted for at least 20% of annual fuelwood production. Community wooslots established with government assistance were an insignificant source of fuelwood in both areas. At an estimated cost of nearly US $500 haa??1, community woodlots planted with government assistance are far more expensive to establish than individual farm woodlots which require no monetary expenditure, assuming local collection of seed. The results indicate a need to increase the local production of fuelwood in rural Swaziland and that encouraging the establishment of onfarm woodlots may be the most effective means of increasing production.
Bulletin of the United States Geological and Geographical Survey of the Territories: Volume IV, Number 4
Table of Contents ART. XXXII.---The Fossil Insects of the Green River Shales. By Samuel H. Scudder, Cambridge, Mass.....747-776 ART. XXXIII.---Report on the Collection of Fishes made by Dr. Elllott Cones, U.S.A., in Dakota and Montana, during the seasons of 1873 and 1874. By DavidS. Jordan, M.D......777-800 ART. XXXIV.----Catalogue of Phraenogamous and Vascular Cryptogamous Plants collected during the summers of 1873 and 1874, in Dakota and Montana, along the forty-ninth parallel, by Dr. Elliott Cones, U.S.A.; with which are incorporated those collected in the same region at the same times by Mr. George M. Dawson. By Prof. J. W. Chickering.....801-830 ART. XXXV.-----On some Striking Products of Erosion in Colorado. By F.M. Endlich, S.N.D......831-864 ART. XXXVI.----Paleontological Papers No.8: Remarks upon the Laramie Group. By C.A. White, M.D......865-876 ART. XXXVII.---Synonymatic List of the American Sciuri, or Arboreal Squirrels. By J.A. Allen. (See p. 905.).....877-887 Index.....889-908
I. Sexual, individual, and geographical variation in leucosticte tephrocotis, II.Geographical variation among North American mammals, especially in respect to size
Having recently had an opportunity (through the kindness of Professor Baird) of studying with some care the magnificent series of skulls of the North American Mammalia belonging to the National Museum (amounting often to eighty or a hundred specimens of a single species), I have been strongly impressed with the different degrees of variability exhibited by the representatives of the species and genera of even the same family. The variation in size, for instance, with latitude, in the Wolves and Foxes is surprisingly great, amounting in some species (as will be shown later) to 25 per cent. of the average size of the species, while in other species of the Ferae it is almost nil . Contrary to the general supposition, the variation in size among representatives of the same species is not always a decrease with the decrease of the latitude of the locality, but is in some cases exactly the reverse, in some species there being a very considerable and indisputable increase southward . This, for instance, is very markedly true of some species of Felis and in Procyon lotor . Consequently, the very generally-received impression that in North America the species of Mammalia diminish in size southward, or with the decrease in the latitude (and altitude) of the locality, requires modification. While such is generally the case, the reverse of this too often occurs, with occasional instances also of a total absence of variation in size with locality, to be considered as forming "the exceptions" necessary to "prove the rule".