High Shoot Density Research Articles

Crustal structure along the EDGE transect beneath the Kodiak shelf off Alaska derived from OBH seismic refraction data

Along the EDGE Alaska transect over the Kodiak shelf off Alaska, a deep-crustal seismic refraction experiment was carried out in 1994 using an airgun source with a high shot density and closely spaced ocean-bottom hydrophones (OBHs). These data clearly define a gently dipping plate boundary that gradually increases from 2.5° at the trench to 5° 250 km landwards of the trench beneath the shelf. A landward increase of the velocities in the subducting oceanic crust was found. The sedimentary upper plate beneath the continental slope can be divided into a young Neogene accretionary prism beneath the lower slope, and a more layered structure below the middle and upper slope, where a body with elevated velocities (4.2–5.1 km s−1) in the lower part is interpreted as well-consolidated sediment of possibly late Eocene age, acting as the backstop. Across the inner shelf between Kodiak Island and Kenai Peninsula, near-surface high velocities (> 6.0 km s−1) document a strong uplift (> 10 km) of the Mesozoic and Palaeocene accretionary complex, and furthermore suggest its seaward extension beneath the outer shelf. The most striking feature along the EDGE transect is the thick low-velocity zone (LVZ) that coincides with the arched reflectors in the lower crust beneath the Kodiak Island-Kenai Peninsula axis on the EDGE seismic reflection data. This LVZ is interpreted as indicating underplated low-velocity rocks, which contribute the same volume of new material as the frontal accretion to the continent, the growth of which is rapid, totalling 4200 km2 across the Kodiak shelf since Eocene times. A calculation of the material balance shows that an underplating of underthrust sediment alone may not account for the huge volume of the underplated low-velocity rocks. We speculate that the underplating of continental fragment, or more likely seamounts or plateau, may be involved in continental growth

Production and population ecology of Phyllospadix iwatensis Makino. II. Comparative studies on leaf characteristics, foliage structure and biomass change in an intertidal and subtidal zone

A seagrass in Japan, Phyllospadix iwatensis Makino, is distributed in the lower intertidal zone and upper subtidal zone making a dense population on the Choshi coast, Japan. Intertidal P. iwatensis is able to receive sufficient light for photosynthesis but experienced severe exposure to the air, which decreased a large amount of aboveground biomass in April to June (i.e. the daytime exposure season). Subtidal P. iwatensis was never exposed throughout the year and the aboveground biomass increased gradually over the daytime exposure season. However, the maximum aboveground biomass and shoot density of the subtidal plant never exceeded that of the intertidal plant. The dense foliage, large aboveground biomass and high shoot density of both intertidal and subtidal plants is likely to be an adaptation to heavy water movement, but the subtidal plants always received insufficient light for photosynthesis as a result of having dense foliage, particularly in turbid water. In choppy and swell sea, P. iwatensis did not seem to be adapted to growing in the subtidal zone where there was shortage of light.

Crustal structure of the Middle American Trench off Costa Rica from wide‐angle seismic data

Off Costa Rica seismic wide‐angle experiments were made using marine seismic sources of high shot density and ocean bottom hydrophones (OBH) and land stations for recording. Three profiles perpendicular to the Middle American Trench (MAT) and one parallel to it are presented here. The coverage from closely spaced OBH, and structural constraints from the coincident near‐vertical reflection seismic survey provided detailed velocity depth distributions. Over 4.0 km/s velocities were found directly underlying the thick continental margin sediment in a margin wedge that extends from below the coastal area seaward within 10 km from the MAT axis. The interpretation of the wide‐angle data required a low velocity zone (LVZ) between the upper and lower plate, indicating its nature as subducted and underplated sediment. The velocity depth distributions support the hypothesis that the continental margin wedge off Costa Rica is most likely an offshore extension of the Nicoya complex ophiolitic rocks, which are exposed along the coast. The subduction of the sediments seems very efficient and the accretionary prism appears to be confined to the lower slope.

Ramet size equalisation in a clonal plant, Phragmites australis.

The influence of shading from older generations of dead culms (standing litter) on density, growth rate and development of size structure at the ramet level was investigated in a pure stand of Phragmites australis by experimental neutral shading of plots after removal of standing litter. Initial differences in height distribution between autumn and spring cohorts disappeared in the course of shoot growth. The Gini coefficients of shoot heights and estimated shoot weights indicated that the size structure of the shoots became more equal with increasing mean size in both shaded and unshaded plots. Relative growth rate for height (RHGR) and weight of individual shoots was negatively related to shoot size during the early and presumably storage-dependent growth period, suggesting a strong support for growth of smaller shoots. No etiolation was indicated by mean or maximum height in shaded and unshaded plots, or by the relationship between shoot height and weight. Mean shoot density was significantly lower in shaded than in unshaded plots in one of two shade treatment years. A regression model indicated a small but significant effect of shoot density on the approximately linear relationship between RHGR and the logarithm of height. The growth rate of small shoots was slightly larger at low than at high shoot density. Therefore, it is suggested that the shade from standing litter in P. australis stands can decrease shoot natality in the spring cohort, and thereby increase the support to fewer small shoots.

Polychaete Depth Distribution in a Posidonia oceanica Bed (Rhizome and Matte Strata) and Neighbouring Soft and Hard Bottoms

Abstract. The study was carried out in a Posidonia oceanica bed and in the neighbouring sandy and rocky bottoms, at Ponza Island (Central Tyrrhenian Sea), in order to investigate the distributional pattern of the polychaete community at different depths. A total of 15232 individuals of polychaetes belonging to 218 species was collected and three new species of Syllidae were found. The polychaete community of the matte can be clearly distinguished from the neighbouring communities; this is due to the high species richness in Posidonia, which is related to the heterogeneity of the biotope. In the Posidonia bed the shallow stations (1 m and 5 m depth) were the richest in terms of species numbers and individuals due to the high shoot density of the seagrass bed. In the shallow waters polychaete community structure changed according to the different exposure to water movement. Rocky bottom species, which preferentially inhabit crevices, were more abundant in the matte exposed to water movement (5–10 m depth). In contrast, soft‐bottom species were more abundant in the sheltered zone (1 m depth) as well as in the deeper zone due to the reduction of the Posidonia bed.

A mathematical model of carbon acquisition and utilisation by kiwifruit vines

A mathematical model of carbon acquisition and utilisation by a kiwifruit ( Actinidia deliciosa) vine during the growing season is described. The model includes specific features of deciduous fruit crops, such as maintenance of perennial biomass, growth of deciduous tissues, and hydrolysis, and restoration of carbon reserves. Canopy net photosynthesis is computed hourly according to incident radiation, solar angle, radiation attenuation through the canopy, radiation response of photosynthesis and leaf area, and summed to generate daily totals. Daily maintenance respiration is estimated using mean daily ambient temperature and biomass carbon and nitrogen contents. Daily carbon demands for biomass synthesis, including the costs of growth respiration, are estimated using potential growth rates for individual organs. The daily availability of carbon for partitioning is that from 7-day running means of daily photosynthesis and reserve hydrolysis. Carbon is partitioned first for maintenance of existing biomass, and then remaining carbon is partitioned fro growth of individual organs according to their respective sink strengths which, in turn, depend on their potential relative growth rates. A simulation of the seasonal carbon balance for a kiwifruit vine growing at Hamilton (New Zealand) indicated that maximum depletion of carbon reserves during spring was 103 g C m −2. Biomass synthesis for an entire growing season totalled 225 g C m −2 for the shoot (including the leaves), 319 g C m −2 for the fruit, and 58 g C m −2 for the fibrous roots. Biomass synthesis for the fibrous roots was very similar to simulated sensccene. Biomass synthesis of all vine components was limited by carbon supply, and the seasonal patterns of carbon allocation for growth of vine organs closely resembled field measurements reported elsewhere. Simulated carbon acquisition (photosynthesis) totalled 1773 g C m −2 for the growing season. For the whole vine, the carbon cost of maintenance exceeded that for growth. Synthesis and maintenance of shoots accounted for 40% of total carbon utilisation, while that for fruit accounted for 33%. Varying the fruit number led to proportionally similar changes in simulated total fruit biomass, so that average fruit size was relatively insensitive to fruit number. However, allocation of carbon for fibrous root growth and regeneration of reserves decreased with increasing fruit number. While simulated photosynthesis increased with shoot number and hence leaf area, the marginal gains at high shoot densities were less than the marginal costs of tissue synthesis and maintenance. Hence the optimum leaf area (M 2 m −2 ground areas), associated with maximum allocation of carbon to fruit growth and regeneration of reserves was about 3.5. The main advantages of this model include the value for identifying critical components of the whole plant C economy, the capacity to integrate plant—environment interactions at the whole plant level, and the potential for application to other deciduous fruit crops. A major limitation of the model at present is the lack of adequate published data for testing and validation.

The Performance of Perforated Completions in Gas Reservoirs

Summary A finite-element program was used to study the influence of shot density, perforation length, phasing angle, formation permeability, formation anisotropy, and turbulence factor on the performance of perforated completions in gas reservoirs. The results indicate that when permeability is low (< 10 md), turbulence effects are negligible, and perforation length and phasing angle affect productivity ratio. In anisotropic formations, high shot density (≥ 12 shots/ft [39 shots/m]) with deep penetration (≤ 15 in. [38 cm]) is required for the well to perform better than an openhole completion. Turbulence effects can cause up to 75% loss in production in high-permeability formations. The nomograph presented can be used to predict productivity ratios and skin factors in gas reservoirs.

Fine-scale spatial distribution of leaves and shoots of two chalk grassland perennials

The fine-scale spatial distribution of leaves and shoots of Brachypodium pinnatum and Carex flacca, two rhizomatous graminoids, was investigated in two chalk grasslands in South Limburg (The Netherlands). The objective was to examine whether leaves and shoots of Brachypodium, a dominant species, had a regular distribution on a small scale, as has been suggested for other clonal species that form high-density stands. Patterns were compared to Carex, which is never found to be as abundant as Brachypodium. The number of shoots and leaf contacts were counted in small quadrats, grouped in a grid. Using Moran's I analysis for autocorrelation, it appeared that leaves and shoots of both species were arranged in clumps, and that these clumps were randomly distributed across the soil surface. Shoot clumps in Carex were smaller in diameter and not as pronounced as those in Brachypodium. In most cases, patterns of leaves and shoots were positively correlated, indicating that leaves were predominantly positioned above and around the groups of quadrats where the shoots were attached. However, in dense stands of Brachypodium the positions of leaf clumps were not correlated to those of shoot clumps. This is a result of the tall growth form of this species and its high shoot densities, and it is suggested that this will be a characteristic of any species that dominates a dense stand.

Linear and Radial Flow Targets for Characterizing Downhole Flow in Perforations

Summary Two types of sandstone targets are commonly used to test flow efficiency of shaped-charge jet perforations: "linear" targets, in which flow enters only the unperforated end of the cylindrical sample, and "radial" targets, in which flow enters through the end and sides of the sample. To determine which of these targets best represents downhole conditions, the flow distribution along the length of a perforation has been studied by three-dimensional (3D) finite-element analyses. Linear and radial laboratory targets have been compared with downhole perforations under varying conditions. For ideal perforations, the low-shot-density (LSD) case is adequately represented by the radial target, while the high-shot-density (HSD) case falls between the two targets. With realistic crushed and damaged zones, the HSD case closely matches the linear target, and the LSD case falls between the two targets.

Differential Responses to Photoperiods in Monoecious and DioeciousHydrilla verticillata

Growth and morphology of two U.S. hydrilla biotypes grown under 10- and 16-h photoperiods in outdoor aquaria were investigated. The dioecious hydrilla biotype elongated extensively under both photoperiods and reached the water surface within 2 to 3 weeks after planting. In contrast, the monoecious biotype grew more densely near the sediment, primarily by producing a high number of horizontal stems, root crowns, and higher shoot densities. Monoecious hydrilla grown from tubers produced new tubers after 4 weeks of exposure to the 10-h photoperiod, and the number of tubers produced was five- to sevenfold higher in the monoecious than in the dioecious biotype. Furthermore, monoecious hydrilla produced tubers under both 10- and 16-h photoperiods, with tuber production much higher under the shorter photoperiod. Dioecious hydrilla grown from tubers under similar conditions produced new tubers after 8 weeks only under the 10-h photoperiod. No tubers were produced by the dioecious biotype throughout a 10-week exposure to the 16-h photoperiod.

Comparative Turfgrass Evapotranspiration Rates and Associated Plant Morphological Characteristics

Since water costs are projected to increase substantially, and water availability for turfgrass culture will become more limiting, there is a need for a detailed characterization of water use rates among turfgrass species. The evapotranspiration (ET) rates of 11 C‐4 warm‐season turfgrasses and one C‐3 cool‐season turfgrass were evaluated in minilysimeters with fritted clay as the rooting medium utilizing the water balance method. Turf plots of 1.5 × 1.5 m were constructed to ensure a natural environment surrounding each lysimeter. Evapotranspiration rates plus six morphological characteristics of each species were measured under nonlimiting soil moisture. Significant differences in ET rates were observed both among and within genera. ‘Texas Common’ buffalograss [Buchloe dactyloides (Nutt.) Engelm], ‘Georgia Common’ centipedegrass [Eremochloa ophiuroides (Munro.) Hack], ‘Arizona Common’ bermudagrass [Cynodon dactylon (L.) Pers.], ‘Tifgreen’ and ‘Tifway’ bermudagrasses [C. dactylon (L.) Pers. × C. transvaalensis Davy], and ‘Adalayd’ seashore paspalum (Paspalum vaginatum Sw.) had low ET rates; while ‘Emerald’ zoysiagrass (Zoysia japonica Steud. × Z. tenuifolia Willd. ex Trin.) was characterized as having a medium ET rate. ‘Texas Common’ St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] and ‘Meyer’ zoysiagrass (Z. japonica Steud.) possessed medium low ET rates. However, a 1‐yr study showed that ‘Kentucky 31’ tall fescue (Festuca arundinacea Schreb.) and ‘Argentine’ bahiagrass (Paspalum notatum Flugg.) had medium ET rates, and ‘Common’ blue grama [Bouteloua gracilis (H.B.K.) Lag. ex Steud.] possessed a medium low ET rate. Those grasses with comparatively lower ET rates were generally characterized by (i) a high canopy resistance, including a high shoot density and relatively horizontal leaf orientation; and (ii) a low leaf area, including a slow vertical leaf extension rate and a narrow leaf texture.

Shoot Spacing and Canopy Light Microclimate

The light microclimate of a range of shoot densities (5 - 74 shoots/m) was measured for the cultivar Gewürztraminer. The shoots were trained vertically up or down on four different trellis systems. Theoretical analysis showed that leaf layer number (LLN) varies linearly with the ratio of leaf area to shoot length, mean leaf angle, and shoot density. Low shoot densities (&lt; 10 shoots/m) produced open canopies with a high proportion of canopy gaps, and most leaves and fruit were well exposed to sunlight. High shoot densities (&gt; 30 shoots/m) produced canopies with no gaps, and the majority of fruit and leaves were interior and shaded. Such canopies were characterized by low interior values of photosynthetic photon fluence rate, shortwave radiation, and red to far red ratio. A shoot density of <i>ca</i> 15 shoots/m appears optimal for this variety and location to maintain an adequate canopy microclimate. Closer shoot spacing causes undesirable shading, and wider spacing causes incomplete radiation interception. This paper discusses a range of canopy light measurement methods, both direct and indirect. Of the indirect methods, point quadrat analysis, visual assessment, and measurement of sunfleck length were all quick and simple and produced results related to more time-consuming direct methods with light meters.

Effects of Temperature and Sediment Type on Growth and Morphology of Monoecious and Dioecious Hydrilla

ABSTRACT In a five-week greenhouse investigation, variations in growth and morphology of monoecious and dioecious Hydrilla [Hydrilla verticillata (L. f.) Royle] were compared over a range of temperatures, 12 to 32 C, on an inorganic sediment and on an organic sediment. For these bio-types, total biomass production was severely restricted at 16 C and below, with thermal optima for growth occurring between 28 and 32 C. Total biomass, shoot number, and shoot length for each biotype were greater on the inorganic sediment than on the organic sediment. At higher temperatures, dioecious Hydrilla lengthened more extensively than monoecious Hydrilla; however, the latter produced higher shoot densities and tuber numbers under most experimental conditions. Monoecious Hydrilla appears to be better adapted to moderate temperatures than dioecious Hydrilla, and its potential distribution may include sediments less favorable for growth of the dioecious biotype.

Effects of Differential Defoliation on Shoot Growth, Density and Phytomass of Three Graminoids in a Calcareous Fen

Phytomass, density, growth and turnover of shoots were measured in three perennial graminoids in response to regular, single or no defoliation. Shoot demography of the two species with the shortest tiller longevities, Molinia caerulea and Schoenus ferrugineus, was readily modified by defoliation. The lack of responses in Carex fusca may be attributable to morphological constraints associated with longer-lived shoot systems. Shoot leaf areas of all three species were reduced under regular mowing, and with the exception of Carex, individual shoot phytomass declined as well. A single mowing of formerly unmowed swards caused an increase in biomass of Schoenus and Molinia, to values characteristic of unmowed plots. Shoot densities independent of treatment were highest in Schoenus, and lowest in Carex. Defoliation, irrespective of periodicity, resulted in highest shoot densities of Schoenus. Density changes in response to mowing were less pronounced in Molinia and absent in Carex. Reproductive output increased in all three species after the single mowing, thereby significantly exceeding the respective values of Molinia and Schoenus in regularly mowed plots. Reproductive output of Carex was related to age structure, rather than presence or absence of mowing. Detailed mortality studies of Schoenus showed that shoot death was highest in dense, regularly defoliated swards. Tiller dynamics of Schoenus may indicate self-thinning. The observed increases in density, reproductive output and phytomass associated with infrequent mowing suggest that aperiodical defoliation represents a compromise between accelerated shoot turnover associated with regular (annual) mowing on one hand, and inhibition due to self-shading in unmowed swards on the other.

Quantitative and dynamic aspects of a mixed seagrass meadow in Papua New Guinea

Aspects of production and biomass were studied from November 1981 to November 1982 in six seagrass species which together from the mixed seagrass meadows in Papua New Guinea. These species, viz. Thalassia hemprichi (Ehrenb.) Aschers., Cymodocea serrulata (R.Br.) Aschers. et Magnus, Cymodocea rotundata Ehrenb. et Hempr. ex Aschers., Syringodium isoetifolium (Aschers.) Dandy, Halodule uninervis (Forssk.) Aschers. and Halophila ovalis (R.Br.) Hook. f. have been previously studied in monospecific seagrass beds. Thalassia hemprichii was the dominant species, followed by Syringodium isoetifolium. These two species were present in all samples and evenly distributed. Cymodocea serrulata and C. rotundata were recorded in 91 and 86%, respectively, of the quadrats sampled. The density, however, varied considerably. Shoots of the remaining two species were found in < 50% of the samples. The percentage presence increased when below-ground plant parts were taken into account. Significant differences in the shoot density were only found in Syringodium isoetifolium. The distribution of the five other species remained unchanged during the year. Annual mean shoot density amounted to 860 for Thalassia hemprichii, 2100 for Syringodium isoetifolium, 200 for Cymodocea serrulata, 250 for C. rotundata and 54 for both Halodule uninervis and Halophila ovalis. All species reached their maximum density from September to November. The mean aboveground production was 3.9 g ash-free dry weight (ADW) m −2 day −1, of which 64% was contributed by Thalassia hemprichii. Syringodium isoetifolium, which had the highest shoot density, contributed only 17%. The plastochrone interval of the leaves (PIL) was constant in all species and the mean ranged from 10.1 to 11.1 days. The PIL was virtually the same in this mixed meadows as in monospecific seagrass beds. Furthermore, the above-ground relative growth rate was constant during the year. Thalassia hemprichii was the most productive seagrass (mean 0.043 day −1), whereas the lowest mean relative production was observed for Syringodium isoetifolium (0.030 day −1). Total mean production was 6.4 g ADW m −2 day −1, of which 39% was contributed by the vertical axes, the rhizomes and the roots. The caloric production efficiency of the meadows was 0.58% of the total insolation at the water surface. Thalassia hemprichii was, because of its morphology, the stable element in the meadow. All other species were present at all times and exhibited a continuative process of recolonization.

Comparison Between Perforating System And Study Of Perforating Efficiency

The major objective of perforating is to provide an effective flow communication between wellbore and formation, and achieve adequate well productivity. Perforating techniques and equipment that are used play an important role in determining the production that results. This paper describes the various perforating system used in the oil industry, with tile guns and techniques that are commonly used, applications and limitations of each. Studies also include factors that affect the well productivity as well as other parameters that influence the decision making in chosing the right perforator/gun under existing conditions. Actual data from a local oil field are used as a case study and the performance of different shaped charge are simulated using the Schlumberger SPAN OIL software. The results agree with the previous findings, guns having high shot density. deepest penetration, best phase angle under reversepressure condition give the best productivity.

Le récif-barrière de Posidonia oceanica (L.) Delile de Santa Liberata (Toscane, Italie): cartographie et biometrie

Abstract Barrier-reef of Posidonia oceanica (L.) Delile of Santa Liberata (Tuscany, Italy): cartography and biometry. - The submerged phytocenoses of Posidonia oceanica barrier-reef in the stretch of Santa Liberata coast (Orbetello, Grosseto) have been analyzed. This work has been based on examination of aerophotogrammetric material, on specimens and records made on the spot, according to the technical descriptions on the texts. The barrier-reef presents a very high leaf shoot density and high values of leaf area index, but low values for the leaf length and high values of epiphytism have been noticed.

Effect of Shoot Density and Crop Control on Growth, Yield, Fruit Composition, and Wine Quality of ‘Seyval blanc’ Grapes

Abstract A factorialized thinning level/shoot density experiment which was started in 1980 demonstrated that ‘Seyval blanc’ grapes benefits from cluster thinning in terms of vine size maintenance, cane ripening, berry weight, and Brix. Reducing shoot density led to increased cane ripening. Concomitant increases in cluster exposure improved fruit composition and led to higher berry weights. However, maintaining reasonably high shoot densities (4 shoots/30 cm of row or more) also was essential to maintain yield and vine size, even when crop was controlled by thinning. Levels of 4 shoots/30 cm of row and 17 clusters/500 g cane prunings are recommended to maximize yield and maintain reasonable fruit quality and vine size. Postbloom cluster thinning was found to reduce the incidence of bunch rot and to reduce the production of 2nd crop in 1982, without affecting any parameters of yield or fruit composition.

A Practical Drill-Stem Testing Technique, Combining High Shot Density Underbalanced Perforating With Full Bore Test Tools

Abstract Since 1976 Gulf Canada Resources Inc. through partnership arrangements, has participated in several offshore exploratory wells drilled and tested from artificial islands and drillships in the Canadian Beaufort Sea. As an operator since 1980, Gulf has drilled and evaluated a number of additional offshore wells to depths of 4800 m (15,750 ft) in as much as 30 m (98 ft) of water. Drilling and testing procedures have been refined through years of operating in the hostile Arctic environment to maximize information obtained and to minimize rig time. This paper chronologically reviews the offshore drill-stem testing techniques utilized by Gulf during 1982 when three Beaufort Sea wells were evaluated: two from an artificial island, one from a drillship. Future well tests by Gulf will incorporate many of the concepts illustrated here, as well as some recently improved tool technology. Introduction The Beaufort Sea is one of the harshest yet most sensitive environments in the world where oil and gas exploration activities occur. The Canadian Beaufort Sea extends west from Banks Island (125 ºW) to the Yukon I Alaska border (141 ºW) and north from the coastline (69 ºN). Figure 1 shows geographically where Gulf Canada Resources Inc. has current exploration agreements, and several well locations in which Gulf has an interest. Gulf interest acreage encompasses water depths from 20 m to 100 m, with the major portion occurring between the 20 m and 50 m bathymetric contours. Environment Typical environmental conditions are as shown in Figure 2, illustrating seasonally the hours of daylight available, air temperatures, ice cover/ice concentration, precipitation and visibility. A typical drillship operating season extends from 80 to 120 days between July 1 and October 31, with artificial islands in most cases operating all year long. Governmental regulations prohibit floating drilling operations below risk hreshold depth any later than September 25; extensions however, an be granted dependent upon ice conditions. Cased hole testing has been allowed up to early November for drillship operations. Island operations have fewer restrictions, requiring suspension of activities only when environmental onditions are severe enough to affect island stability or for relief well considerations. Well Schedule Figure 2 also shows the well schedule for the Gulf-operated wells during 1982. Two different units were used to drill and test the three wells discussed in this paper. The Canmar Beaufort Island Rig No.1 was installed on Tarsiut Island in the fall of 1981 and drilled the Gulf et al. East Tarsiut N-44 vertical well during the winter of 1981–82, and the Gulf et al. East Tarsiut N-44A directional well during the summer of 1982. The Canmar Explorer 1 drillship was used on the Gulf et al. Kiggavik A-43 vertical well, also during the summer of 1982. The major difference in the two operations was the use of a land wellhead and surface BOP stack on the two island wells, while the A-43 well used a subsea wellhead and BOP stack located on the seafloor.

A multivariate approach to the problem of decline in vigour of Ammophila

On stabilized sand dunes where sand deposition has ceased, Ammophila breviligulata Fern, declines in vigour, flowers less prolifically, and often remains vegetative. Many explanations for this decline have been put forward in the past. This study has chosen a comparative multivariate approach to address the problem.For this objective, 59 random 1-m2 quadrats were laid out over a young sand dune system near Port Franks, Ontario, on the southeastern shore of Lake Huron. In each plot six environmental variables (sand deposition, sand flux, number of annual species, number of perennial species, soil temperature, and the depth of the roots) and four plant characters of A. breviligulata (flowering percentage, shoot biomass, vegetative reproduction rate, and shoot density) were recorded. The resulting data matrices were subjected to canonical correlation analysis.The results revealed that, of the environmental variables, both sand deposition and root depth had strong relationships with shoot biomass (positive), flowering (positive), and vegetative reproduction rate (negative). Competition from annuals and perennials appeared a secondary factor in the decline of A. breviligulata. Flowering was rare in high shoot density sites with low levels of sand deposition and in low density sites with greater number of annual species.