Abundance Of Cones Research Articles

Spatial pattern of coniferous and deciduous forest patches in an Eastern North America agricultural landscape : the influence of land use and physical attributes

In agricultural landscapes, most studies have investigated the influence of the spatial pattern of forest patches on other ecological phenomena and processes, such as animal movement and biodiversity. However, few have focused on explaining the spatial pattern of the forest patches themselves. Understanding how these patterns relate to the processes that generate them is fundamental in developing a sound theory of landscape ecology, and in devising rational management strategies. In this paper, the pattern of the overall forest patches, as well as the pattern of deciduous and coniferous patches in an agricultural landscape of Southern Quebec, Canada, were analyzed and related to landscape physical attributes and land use, using remote sensing, geographic information systems and statistical methods. Results show that the role of landscape physical attributes on forest patch pattern has been modified by land use. In the study area, coniferous or deciduous patches are not associated with a specific surface deposit. In addition, physical attributes explain only a small proportion of the abundance of conifers on past abandoned land compared with land-use factors. Physical attributes only indirectly influence the forest pattern because they strongly influence the land-use practices. Our results reveal a conifer recovery process with the abandonment of agricultural land. On past abandoned land, conifers expand with increasing stand age, mostly by invasion from neighboring coniferous patches. Spatially, coniferous patches are usually located on the margins of the overall forest patches, and they are connected to non-forest land-use types such as crop and pasture, the latter being the most important. By showing the importance of some coniferous forest types that did not exist in the precolonial forest, a new perspective emerges when landscape, especially, land-use dynamics are taken into account.

Evolutionary assembly of the conifer fauna: distinguishing ancient from recent associations in bark beetles.

Several shifts from ancestral conifer feeding to angiosperm feeding have been implicated in the unparalleled diversification of beetle species. The single largest angiosperm-feeding beetle clade occurs in the weevils, and comprises the family Curculionidae and relatives. Most authorities confidently place the bark beetles (Scolytidae) within this radiation of angiosperm feeders. However, some clues indicate that the association between conifers and some scolytids, particularly in the tribe Tomicini, is a very ancient one. For instance, several fragments of Gondwanaland (South America, New Caledonia, Australia and New Guinea) harbour endemic Tomicini specialized on members of the formerly widespread and abundant conifer family Araucariaceae. As a first step towards resolving this seeming paradox, we present a phylogenetic analysis of the beetle family Scolytidae with particularly intensive sampling of conifer-feeding Tomicini and allies. We sequenced and analysed elongation factor 1alpha and nuclear rDNAs 18S and 28S for 45 taxa, using members of the weevil family Cossoninae as an out-group. Our results indicate that conifer feeding is the ancestral host association of scolytids, and that the most basal lineages of scolytids feed on Aramucaria. If scolytids are indeed nested within a great angiosperm-feeding clade, as many authorities have held, then a reversion to conifer feeding in ancestral scolytids appears to have occurred in the Mesozoic, when Araucaria still formed a major component of the woody flora.

A review of factors affecting the population dynamics of jack pine budworm (Choristoneura pinus pinus Freeman)

AbstractJack pine budworm (Choristoneura pinus pinus Free.) (Lepidoptera: Tortricidae) is a native insect that periodically defoliates areas of jack pine (Pinus banksiana Lamb.) in the subboreal forests of North America east of the Rocky Mountains. Outbreaks of jack pine budworm generally occur at 6‐ to 12‐year intervals and collapse after 2–4 years. Periodicity of outbreaks varies and is associated with site‐related factors. Survival of early‐instar larvae during spring dispersal is tied to the abundance of pollen cones (microsporangiate strobili), which provide a refuge for larvae until current‐year needles expand. Jack pine trees that have been heavily defoliated produce few pollen cones in the following year, often resulting in high mortality of early‐stage larvae. A diverse guild of generalist parasitoids attack jack pine budworm, but only a few species account for most mortality in any area. Collapsing jack pine budworm populations are characterized by sharp declines in early instar survival, coupled with an increased rate of parasitism in the late larval and pupal stages. The reciprocal interaction between heavy defoliation and low pollen cone production, and increased parasitism of late‐stage larvae or pupae, are consistent with second‐order density dependence factors identified in analysis of a long‐term population data set. Since the 1950s, several jack pine budworm outbreaks have been roughly synchronous over a large geographic area, suggesting that Moran effect processes, as well as moth dispersal or other factors, may be involved in jack pine budworm dynamics. Although the short duration of outbreaks enables most trees to recover, over time dead trees and top‐killed trees accumulate in jack pine stands. Jack pine is well adapted to fire and when fires ignite, the accumulation of dead trees and woody debris often leads to intense wildfires followed by prolific regeneration. The three‐way interaction of jack pine, jack pine budworm, and fire ultimately serves to maintain vigorous stands and ensures continued hosts for jack pine budworm.

Early loss of synaptic protein PSD-95 from rod terminals of rhodopsin P347L transgenic porcine retina

Retinitis pigmentosa (RP), a type of retinal degeneration involving first rod and then slow cone photoreceptor degeneration, can be caused by any of a number of mutations in different genes. In the cases of mutations affecting rod-specific genes such as rhodopsin, it is unclear how the mutations may cause degeneration of cones. We have used the porcine retina, which is rod-dominated and has an abundance of cones, to study the mutation-induced changes in both rod and cone photoreceptors. Like patients with the same mutation, rhodopsin P347L transgenic swine manifest rod–cone degeneration. In addition, the rod bipolar cells fail to form synaptic connections with rods; instead, they form ectopic synapses with cones. The mechanisms that prevent the formation of the rod–rod bipolar cell synaptic connection are not known. We used specific antibodies and immunocytochemistry to show that the synaptic protein, PSD-95, is present in both normal and transgenic porcine retinas. During neonatal development, however, PSD-95 is lost from rod terminals in the transgenic swine. This loss is virtually complete (90%) by postnatal day 5, at a time when greater than 80% of rod cell bodies still remain. Furthermore, the remaining rods retain their outer segments and their gross morphology appears relatively normal. In contrast, PSD-95 expression continues in cone terminals, even in 10-month-old transgenic swine, where the rods have all disappeared and the cones show signs of severe degeneration. These results suggest that loss of PSD-95 may not be a general consequence of the deteriorating cell. Rather, the very early and selective loss of PSD-95 from the rod terminals may be causally related to the absence of rod–rod bipolar cell synapses in the rhodopsin P347L transgenic retina.

The foraging behaviour and diet of red squirrels Sciurus vulgaris receiving supplemental feeding

The effect of ad libitum supplemental feeding upon the diet and foraging behaviour of red squirrels Sciurus vulgaris was studied in a coniferous habitat during May 1994 ‐ July 1996. Although supplemental feeding in the form of peanuts was widely available, the animals continued to exploit natural foods such as pine seed, buds and flowers. The degree to which pine seed was exploited was a function of pine cone availability. In contrast, peanut consumption was not correlated with peanut availability, but was determined by the abundance of pine cones. During late winter and spring when seed was becoming scarce, peanuts contributed 30–56% of the dietary items. In addition, increasing amounts of alternative ‘low energy’ foods such as buds and flowers were also exploited. These foods are calcium rich and their ingestion would compensate for the high phosphorus content of peanuts. The nutritional composition of peanuts appears to have restricted the degree to which they could be included in the diet. Nevertheless peanuts were an important dietary component, and seasonally contributed 25–181% of the animals' basic daily energy requirements. Supplemental feeding was associated with relatively large amounts of activity occurring on the ground (annual mean estimates were 47 and 50% of total foraging time). The animals continued to exhibit ‘scatter‐hoarding’ behaviour, with peanuts accounting for 90% of the identified cached items. This stored resource could satisfy 344 (1994/95) and 198 (1995/96) days of the animals' basic energy requirements.

A hierarchical analysis of nesting and foraging habitat for the conservation of the Hispaniolan White-winged crossbill ( Loxia leucoptera megaplaga)

Little is known about habitat use by the endemic Hispaniolan White-winged crossbill ( Loxia leucoptera megaplaga), in part because of its small population size and wandering tendencies; before this study only a single nest had been described for the species. From 1996 to 1999 we studied crossbill abundance, and foraging and nesting habitat at three scales (individual tree, local patch, and landscape), in the Sierra de Bahoruco, Dominican Republic. Point-count estimates of the number of crossbills encountered in the 3 study sites varied significantly among years and sites (range=0.00–2.95 birds/ha), but we estimate that there may be as many as 3000 crossbills in the Sierra de Bahoruco and 3375 island-wide. Annual means of crossbill abundance were highly correlated with mean scores of pine cone abundance. Fifteen nests found in pine trees had a mean nest height of 14.2 m. Two nests were found at heights of 1.0 m and 1.5 m in understory shrubs of Lyonia sp. (Ericaceae). The mean age of 15 trees used for foraging or nesting by the crossbill was 96 years. The height of trees used for foraging was significantly greater, and bore significantly more cones, than randomly chosen cone-bearing trees from across the study sites. Results from our multivariate analyses of nesting and foraging habitat at the patch level suggest that crossbills favor sites that have taller, more densely spaced pine trees, and foraging sites contain more cones than are generally available. At the landscape level, both nesting and foraging results suggest that crossbills may respond negatively to fragmentation of the pine forest. Uncontrolled fires are the most important threat to pine forests and the persistence of the crossbill; our models suggest that at current burning regimes pine forest will be nearly eliminated within 100–150 years. Changes in the fire regime are probably human-caused and have altered the nature of fire in this system. Our study supports previous findings that expanses of mature pine are required by this species, but we also suggest protection of unfragmented areas with higher rates of canopy closure.

Sharp Decrease in Summer Monsoon Strength 4000–3500 cal yr B.P. in the Central Higher Himalaya of India Based on Pollen Evidence from Alpine Peat

Age-constrained pollen data and magnetic susceptibility of an alpine peat profile from the Garhwal Higher Himalaya display a continuous record of climate and monsoon trends for the past 7800 yr. About 7800 cal yr B.P., dominance of evergreen oak (Quercus semecarpifolia), alder (Alnus), and grasses in the pollen record reflect a cold, wet climate with moderate monsoon precipitation. From 7800 to 5000 cal yr B.P., vegetation was progressively dominated by conifers, indicating ameliorated climate with a stronger monsoon. A warm, humid climate, with highest monsoon intensity, from 6000–4500 cal yr B.P. represents the mid-Holocene climatic optimum. Between 4000 and 3500 cal yr B.P., the abundance of conifers sharply decreased, with the greatest increase in evergreen oak. This trend suggests progressive cooling, with a decrease in the monsoon to its minimum about 3500 cal yr B.P. Two relatively minor cold/dry events at ca. 3000 and 2000 cal yr B.P. marked step-wise strengthening of the monsoon until ca. 1000 cal yr B.P. After a cold/dry episode that culminated ca. 800 cal yr B.P., the monsoon again strengthened and continued until today. A sharp decrease in temperature and rainfall at 4000–3500 cal yr B.P. represents the weakest monsoon event of the Holocene record. This cold/dry event correlates with proxy data from other localities of the Indian subcontinent, Arabian Sea, and western Tibet.

A survey of insects attacking seed cones of Pinus cembra in the Alps, the Pyrenees and Massif Central

The composition and impact of the entomofauna exploiting seed cones of Swiss stone pine (Pinus cembra L.) was surveyed in native stands and plantations of France, Italy, Switzerland and Austria during 1992-1996. A total of 2785 cones were collected from 25 sites. The cone entomofauna consisted of five species, of which three (Dioryctria abietella, Eupithecia abietaria, Cecidomyia pini) were regularly observed. The two other insects, Polydrusus atomarius and Zeiraphera diniana were observed on first-year cones, and only in two stands. No spermatophagous insect was detected. None of these insect species could be considered specific to cones of P. cembra. The overall damage never exceeded 40% of the cone crop. The importance of cone damage varied with year, cone abundance, and the position of the tree in the stand. The cone entomofauna of Swiss stone pine largely deviated from that recorded in cones of other high altitude conifers but resembled that of other stone pines growing in Eurasia. The question: why cones of P. cembra were less damaged by insects than those of other alpine conifers is discussed.

Oviposition site selection and intraspecific competition influence larval survival and pupal weight of Strobilomyia neanthracina (Diptera: Anthomyiidae) in white spruce

Densities of coniferous seed cones fluctuate greatly from year to year, and thus cones may be a limiting resource for obligate endoparasites of seed cones during years of low cone abundance. We examined this for the spruce cone maggot, Strobilomyia neanthracina Michelsen, whose larvae feed entirely within the cones of white spruce, Picea glauca (Moench) Voss. During a year of very low cone densities, we tested the predictions that egg density, larval survival, and pupal weight would be positively related to cone size, and that larval survival and pupal weight were negatively related to the number of fly larvae developing in a cone. Although previous studies demonstrated that S. neanthracina avoids ovipositing on cones containing a conspecific, we observed that more than 90% of the cones examined contained three or more eggs. This suggests that cones were a limiting resource for females. The number of eggs laid per cone increased with cone size but the slope of this relationship varied significantly among clones of trees in this seed orchard. Survival of fly larvae and weight of pupae were positively related to cone size and negatively related to the number of hatched eggs per cone in at least one of two samples of cones. Reductions in pupal weight with decreased cone size and increased egg densities suggests that exploitation competition occurred among third (last) instar larvae. However, because most larval died during the second instar, before consuming much food, most larval mortality was probably due to interference competition among larvae. Tree clone significantly influenced larval survival in one cone sample and the relationship between survival and number of hatched eggs per cone in another. Our results support a link between the preference by spruce cone flies for larger cones and the performance of their progeny. Reduced larval survival when more than one individual developed in a cone indicates that selection of unoccupied cones, when available, is adaptive.

Estimating seed quantity and quality in shortleaf pine (Pinus echinata Mill.) cones from natural stands

The quantity and quality of seeds were studied in 886 shortleaf pine cones collected from 48 trees in each of two 15-ha natural stands in western Arkansas, USA. The number of seeds per cone ranged from 0 to 102, and averaged 34.6 and 38.0 in the two stands. Between 30 and 50 percent of the seeds were sound. Overall mean values for total number and total sound seeds compare with previous work. However, the wide variation between individual trees in a stand needs to be considered when evaluating cone abundance and estimating potential seed yields. For the stands observed in this study, a sample of 65 to 85 cones would be needed to estimate the number of sound seeds per cone (within ±3 seeds) with 95 percent probability. Sampling 1 or 2 cones from each of about 3 trees per ha would provide a reliable estimate of sound seed contents.

Aspect influences cone abundance within the crown of Pinus banksiana Lamb. trees at the limit of the species distribution in northern Québec (Canada)

:We studied the variability in cone and seed production and vegetative growth within the crown of jack pine trees (Pinus banksiana Lamb.) in a population at the limit of the species distribution in northern Québec. Number of cones, number of fertile scales per cone, proportion of formed seeds per cone, and branch elongation were compared among heights and aspects for 15 trees, over a 4-year period. Cone number was generally greater in the south quadrant and in the upper part of the tree crown. Number of fertile scales per cone, proportion of formed seeds per cone, and branch elongation were also higher in the upper part of the tree crown, but did not vary much with aspect. Increased cone production in the south quadrant of the tree crown was thus not strictly related to higher branch growth and vigor, but appeared to result from direct and/or indirect effects of higher intercepted radiation on this part of the tree crown.

Winter Use of Glyphosate-Treated Clearcuts by Moose in Maine

Aerial treatment of naturally regenerating clearcuts with the herbicide glyphosate initially reduces the availability of deciduous browse, but may subsequently improve bedding cover for moose (Alces alces). However, the potential effects of these vegetative changes on use of clearcuts by moose has received little study. We studied effects of glyphosate treatment of clearcuts in Maine on (1) use of clearcuts by moose and (2) conifer cover during 2 periods, 1-2 and 7-11 years posttreatment. We made counts of moose tracks, beds, and pellet groups on transects in treated and untreated clearcuts in January-March 1992 and 1993 and measured conifer densities in January-March 1991-93. At 1 and 2 years posttreatment, tracks of foraging moose were 57 and 75% less abundant on treated than untreated clearcuts (P = 0.013). Counts of moose beds, total tracks, and pellet groups exhibited similar patterns as tracks of foraging moose but did not differ (P > 0.1) between treatments. At 7-11 years posttreatment, tracks of foraging moose (P = 0.05) and moose beds (P = 0.06) were greater on treated than untreated clearcuts. Conifer densities at 1-2 years posttreatment were not affected (P > 0.1) by treatment, but conifers 2.0-2.9 m tall were 2 times more abundant (P < 0.1) on treated than untreated clearcuts at 7-11 years posttreatment. Less foraging activity at 1-2 years posttreatment appeared to be the result of reduced browse availability because conifer cover for bedding was similar on treated and untreated clearcuts. We hypothesized that greater counts of tracks of foraging moose on older treated clearcuts was due to increased foraging activity on sites with more abundant conifer cover.

Ecological factors affecting the abondance of advance regeneration in Quebec's southwestern boreal forest

Boreal forest disturbance regimes have changed during the past century, in turn changing regeneration and stand dynamics of these forests. This is occurring at the same time that the forest industry is emphasizing operations that take advantage of pre-established natural regeneration. This study has therefore investigated the effect of various ecological factors on the abundance of Abiesbalsamea (L.) Mill., Piceaglauca (Moench) Voss, Piceamariana (Mill.) BSP, Thujaoccidentalis L., Betulapapyrifera Marsh., and Populustremuloides Michx. natural regeneration in some boreal stands in the Abitibi region of Quebec. Abiotic ecological site classification variables were found to be poorly correlated with seedling densities for most species. Parent trees, as a seed source, and stand type, for its influence on the quality of the seedbed, were strongly correlated with abundant conifer regeneration. As expected, time since fire was positively correlated with seedling abundance for late successional species, whereas it was not related to the abundance of early successional species. Post-fire disturbances, such as those due to spruce budworm (Choristoneurafumiferana (Clem.)) outbreaks, accounted for the variations in seedling densities observed with respect to stand age. The presence of budworm-caused gaps was positively correlated with regeneration abundance, whereas shrub competition, which was greatest in large gaps, was negatively correlated with advance regeneration density. Forest management based on abundance of pre-established regeneration should focus mainly on mixed stands because seedling density is very low in hardwood stands and because of the strong competition found in large gaps of resinous forests. The low number of seedlings observed, especially in coniferous stands, may limit the effectiveness of operations that take advantage of advance regeneration. The large variability observed among site and stand types limits their operational use in predicting seedling densities.

Jurassic palynology from a borehole in the Champagne area, France-correlation of the lower Callovian-middle Oxfordian using sequence stratigraphy

The cored borehole A901, drilled by the National Agency for the Management of Radioactive Waste at Montcornet, in Champagne, on the northeastern border of the Paris Basin, provided a continuous section from the Hettangian to the lower Kimmeridgian. Samples taken at regular intervals yielded marker dinoflagellate cysts of the northwest European domain that have been correlated with ammonite zones. The earliest dinoflagellate species appear in the upper Sinemurian (976 m, Obtusum zone), whereas the lowest intersected beds contain abundant conifer pollen and pteridophyte spores. The microplankton becomes diversified along the hole, in particular in the Callovian-Oxfordian beds; the Bathonian gravelly oolitic limestones are unfavourable for preservation of microflora. The sequence-stratigraphical interpretation was based on lithological, sedimentological and biostratigraphical information and seismic profiles. A semi-quantitative estimation of the microplankton content and of the number of species per sample enabled identification of the main transgressive-regressive cycles and condensed sequences in the lower Callovian to middle Oxfordian.

Host‐plant influence on the population ecology of the jack pine budworm, Choristoneura pinus (Lepidoptera: Tortricidae)

Abstract. Newly‐emerged, second‐instar jack pine budworm (Choristoneura pinus Freeman) establish spring feeding sites preferentially in the pollen cones of their host tree, Pinus banksiana Lamb. Laboratory studies showed that the rate of establishment and survival of jack pine budworm on pollen cones was high throughout the entire spring emergence period of the insect. In contrast, the rate of establishment and survival of jack pine budworm on vegetative buds was very poor early in the spring. Vegetative buds were only acceptable as feeding sites to the jack pine budworm for a relatively brief period in late spring. Field studies showed that the change in population density of jack pine budworm during the spring emergence stage, as expressed by k‐values, was a function of the abundance of pollen cones in the stand. Population reduction was greatest in those stands with the fewest pollen cones. Direct measurement of spring dispersal by jack pine budworm showed that dispersal and consequent losses to the budworm population were greatest in stands with the fewest pollen cones. We conclude that changes in the density of jack pine budworm are strongly influenced by production of pollen cones in the host stand. Because pollen cone production is related to previous years of defoliation by the jack pine budworm, we propose that pollen cones act as a density‐dependent factor governing the density of early‐stage jack pine budworm. The resulting dynamics are compared to those of other budworm species and used to explain observed regional and temporal patterns of jack pine budworm outbreaks.

Horizontal cells in the cone-dominated tree shrew retina: morphology, photoreceptor contacts, and topographical distribution

While most mammalian retinas are rod dominated, in the tree shrew retina 95% of the photoreceptors are cones. We studied three shrew horizontal cells to look for features associated with this unusual photoreceptor arrangement. The morphology of horizontal cells was revealed by intracellular injections of Lucifer yellow, and their photoreceptor contacts were assessed by light and electron microscopy. Horizontal cell topography was studied in material stained with a neurofilament antibody and with toluidine blue. The tree shrew has two types of horizontal cell that are basically the same as A- and B-type horizontal cells of other mammals. All the photoreceptor contacts of the larger, axonless, A-type cell and the dendritic contacts of the smaller, axon-bearing, B-type cell are with cones. Both types contact nearly all the cones in their dendritic field and both types synapse with both red and blue cones. There is no anatomical evidence for chromatic selectivity. The sparsely branched B-type horizontal cell axon probably contacts rods as in other mammals. The unusual features of the A-type cell are the profuse dendritic terminal arborizations and the large dendritic field size. These features may be related to the abundance of cones but do not justify the conclusion for a special type of horizontal cell as has previously been supposed. Both types of horizontal cell have a central-peripheral density gradient; at any location B-type cells are up to three times as numerous as A-type cells. There are detailed features of the distributions that differ from those of other mammalian horizontal cells. The density maximum of B-type cells is in inferior retina and roughly coincides with that of the cones; the A-type maximum is located more superiorly. Neither maximum is colocalized with the ganglion cell peak in the central area. The mosaic of B-type cells is much more regular than that of A-type cells.

Relations between reproductive growth and vegetative growth of Pinus radiata

Growth of female cones and male cones of Pinus radiata was measured and compared with vegetative growth in 10- to 14-year-old plantations given a range of water and nutrient supplies on a site near Canberra, Australia. Although P. radiata trees take about 3 years from ‘flower’ initiation to seed maturation, most of the growth in dry weight occurred in two relatively brief periods: male cones grew mainly in the 3 months before shedding their pollen; female cones grew mainly during the 4 months starting about 13 months after the time of pollen shed. As both male cones and foliage fascicles originate as short-shoot initials, each male cone is produced at the expense of one fascicle of foliage. The number of short-shoots produced was positively related to rainfall during their initiation: about September to January. When this period was dry, fewer short-shoots were initiated and a much lower proportion of these was devoted to male cones. The flowering shoots did not compensate for their loss of fascicles by producing more short-shoots or by growing larger needles. On average, about 13% of the potential foliage was diverted to the production of male flowers. Because female cones originate as long-shoot buds (i.e. buds which otherwise would produce branches), they are also produced at some cost in foliage. Reproductive growth also entailed considerable nutrient cost. Even so, there was no evidence that increased reproductive growth caused any decrease in vegetative growth. Within a stand, stem growth per tree during and shortly after the main growth of male cones did not vary with the abundance of male cones on those trees. The weight of matured male and female cones produced by all five treatments from the four flowerings of 1984–1987 averaged 1.1 t ha −1 year −1. This amount was equal to about 10% of stem growth or 5%% of total above-ground growth. The production of both male and female cones was positively related to rainfall during the September to January period in which the male cones were initiated and also to the vegetative growth that occurred during the year of flower initiation.

Protection of Disease-Resistant Western White Pine Seed from Insect Damage

Abstract Seed produced in blister rust-resistant western white pine (Pinus monticola Douglas) seed orchards is in high demand. The fir coneworm, Dioryctria abietivorella (Groté), and the lodgepole pine coneworm, Eucosma recissoriana (Heinrich), cause considerable damage to seed crops in the Moscow Arboretum seed orchard. Single (May or June) and repeated (May and June) applications of 0.025% fenvalerate, and repeated applications (May and June) of 0.0125% fenvalerate, a synthetic botanical insecticide, were evaluated in 1986 for protection of cone crops. Results in 1986 confirm results in 1984 (Haverty et al. 1986): an application of 0.025% fenvalerate in May and June significantly reduces insect damage, regardless of the relative abundance of cones or insects. The decision to use a single or repeated application depends on demand for seed, projected seed crop and insect populations, and socioeconomic costs of the treatment. West. J. Appl. For. 3(1):18-20, January 1988.

Triassic Conifers as the basis for stratigraphical correlation

Floras with abundant Conifers have been recentlydiscovered in Siberia and China. They are correlated with the floras of the Voltzia sandstones of Western Europe.

Shatter cone geometry and description procedure

This procedure of systematic description of shatter cones defines a field station as a group of lithologically and structurally homogeneous outcrops, and requires the determination of the local tectonic setting within a cryptoexplosion structure and the evaluation of the relative abundance of shatter cones within each station. The orientation of the shatter cone axis and of the apical angle is derived from the measurement of the central striae on several non parallel shatter cone segments. The height of the master cone is determined from the attitude of the two marginal striae at either sides of each segment and the arc length between them. The other style elements of shatter cones require the description of the ornamentation and the evaluation of the length of the central striae. The proposed data sheet permits plotting the main observations, approximating the attitude of the cone axis and screening out erroneous measurements of various types in the field.