Does Araucaria hunsteinii compete with its neighbours?

A comparison of the proportion of total stand basal area contributed by Araucaria hunsteinii, as opposed to the rest of the forest, in a number of 0.5 ha plots from New Guinea rainforest is presented. Results suggest that A. hunsteinii avoids competition with other tree species. Several hypotheses which may explain this phenomenon are advanced.     

The ecology of Araucaria species in New Guinea. III. Population dynamics of sample stands

Life table data for A. cunninghamii and A. hunsteinii from a total of four sites near Bulolo, Papua New Guinea are presented. Sample populations are analysed using the Leslie matrix method. Values of λ, the ‘finite rate of natural increase’, vary between sites and species in the predicted manner. The value of λ calculated for the A. cunninghamii population is close to, and slightly above 1.0, while the three values calculated for A. hunsteinii show wide variation, with values both above and below 1.0. It is argued that A. hunsteinii is a gap regenerating species and cannot regenerate beneath a closed canopy. Evidence presented here and elsewhere indicates that A. cunninghamii is more shade tolerant and therefore, theoretically, better adapted to stable forest situations.     

A matrix population model analysis for the tropical tree,Araucaria cunninghamii

The temporal stability of estimates of demographic behaviour for a sample population of the tropical rainforest gymnosperm Araucaria cunninghamii was analysed using a stage-classified (Lefkovitch) matrix model. Previously published life-table analyses, which used only 2 years of held data (1975–77), were compared with life-table analysis based on a further 5 years of field data for growth and survival (1977–82). The new analysis calculated the finite rate of natural increase, λ, as 1.009 ± 0.077. This value is closer to the theoretical value of 1.0 for a stable population than is the value calculated on the basis of only 2 years of field data (1.021 ± 0.093). However, the two estimates are not significantly different from each other or from a value of 1.0. Despite the similarity of estimates for λ, the life-table analysis based on 5 years of data showed some marked differences from the earlier analysis. Revised growth and survival rates imply a slower progression to reproductive maturity and shorter reproductive life for A. cunninghamii. The predicted stable stage distribution (SSD) showed a better fit to the initial stage distribution (ISD), and bulges in the frequency distribution for large trees can be explained by the varying rates at which individuals grow from one stage to the next. The relative contributions of survival, growth and fecundity to the observed population growth rate (elasticity) remained similar for both analyses. Survival rate contributes most significantly to the achieved population growth rate, and this appears typical of long-lived plant species. However, the pattern of elasticities across size-classes changed for the new analysis and identified different critical life history stages from those recorded previously. Elasticity is proposed as a measure for classifying species using the competitive (C), stress-tolerant (S) and ruderal (R) model of plant strategies.     

Existence of a soil seed bank under rainforest in New Guinea

A germination experiment indicated the existence of viable buried seed of early secondary species under well-developed rainforest near Bulolo, Papua New Guinea. The seed bank was dominated numerically by the secondary tree species, Pipturus argenteus, this dominance increasing with depth. The same species was found to germinate most rapidly and to dominate developing plant cover in seed trays.     

Representation of Landcover Along Breeding Bird Survey Routes in the Northern Plains

ABSTRACT The North American Breeding Bird Survey (BBS) is used extensively to make inferences about populations of many North American bird species and is increasingly being used for avian conservation planning. How well BBS routes represent the landscape is poorly known, even though accuracy of representation could significantly affect inferences made from BBS data. We used digital landcover data to examine how well landcover within 400-m buffers around BBS routes represented the surrounding landscape (the route neighborhood) for 52 routes in the Prairie Pothole Region of North Dakota and South Dakota. Differences in composition between landcover along BBS routes and the route neighborhood were not statistically significant for upland cover classes. The area of temporary and seasonal wetland basins was accurately represented by BBS routes in our study area, but the area of semipermanent and permanent wetland basins was significantly underrepresented along BBS routes. Number of wetland basins and upland patches was higher along routes. Area of urban, forest, and hay landcover classes was higher along routes, although differences were not statistically significant. Amount of bias in landcover representation was negatively correlated with the proportion of each landcover type in the study area, but bias was not correlated with area of the route neighborhoods. Differences between landcover along BBS routes and the route neighborhood were primarily attributable to increased anthropogenic activity along roads and siting of roads away from relatively large, deep water bodies. Our results suggest that inferences made from BBS data in our study region are likely biased for species that are associated with deeper-water habitats or are strongly influenced by landscape fragmentation. Inferences made from BBS data for species associated with uplands or shallow wetlands are less likely to be biased because of differences in landcover composition.     

Inhibition of Bacterial DNA Replication by 6-(<Emphasis Type="Italic">p</Emphasis>-Hydroxyphenylazo)-uracil

THE semi-conservative replication of DNA of Gram-positive bacteria is specifically inhibited by 6-(p-hydroxyphenyIazo)-uracil (HPUra; obtained from ICI) in an apparently novel mechanism^1–4. We have attempted to characterize the HPUra-sensitive site in replication using in vitro preparations of drug-sensitive bacteria. In particulate and soluble preparations of sensitive bacteria, however, HPUra at high concentration does not significantly inhibit polymerization of deoxyribonucleotides^2,4. Since these systems may not accurately represent the process of DNA replication as it occurs in vivo, we have examined the effect of HPUra on a more suitable, toluene-treated preparation of Bacillus subtilis described by Matsushita et al.⁵. In this preparation, DNA replication is ATP-dependent, utilizes deoxyribonucleotides to give biologically active DNA, semi-conservatively and sequentially in the proper gene order. HPUra can inhibit DNA replication by this system. We describe here the characteristics of HPUra inhibition and the conditions necessary for it to occur.     

The Effects of Calcium and the Ionophore A23I87 on Modulation, Nitrogen Fixation and Growth of Soybeans

Tryptophan synthase in Phycomyces blakesleeanus. Part II: Activity of tryptophan synthase in Phycomyces blakesleeanus depending on the light and the content of zinc ions in the culture medium Five-day-old cultures of Phycomyces blakesleeanus show notice-able differences in the phenotype, depending on the culture conditions (permanent light, permanent dark, zinc deficiency, zinc sufficiency) and related to the distribution of tryptophan synthase activity between mycelium and sporangiophores. Permanent light and the presence of zinc ions in the medium during culturing have an antagonistic influence on the tryptophan synthase. The activity of the enzyme is being reduced in the sporangiophores and increased in the mycelium by the influence of light, while zinc ions in the culture medium increase the activity in the sporangiophores at simultaneous reduction in the mycelium. The importance of tryptophan synthase and tryptophan for the development of the fungus in relation to the metabolism of indole acetic acid is discussed.     

Large-Scale Temperature-Induced Synchrony of Cell Division in Euglena gracilis*

SYNOPSIS. Temperature-induced patterns of synchronous cell division and cell size were obtained with Euglena gracilis. The alga was cultured in a glutamate-sucrose medium in 6-liter quantities. Synchrony was induced by non-lethal shifts of temperature between 14.5 and 28.5 C. Three liters of cells containing 2 × 10⁶ cells/ml were harvested in each 24-hour cycle.