ISSN:0012-9658    

DOI:10.2307/1933882

出版商:Ecological Society of America    

年代:1969

数据来源: WILEY

摘要:

The chemical and physical soil characteristics of the Eucalyptus associations in Benandra State Forest are described. Changes in species associations occur over a gradient of increasing moisture and nutrient status of soils from ridge to gully sites. Concentrations of major nutrients in leaves and bark of dominant trees on these sites generally follow the soil gradients. In particular, leaf phosphorus and bark calcium are correlated with the corresponding soil nutrients. Soil calcium and magnesium are also correlated with leaf phosphorus, indicating a possible interaction between these soil nutrients and phosphorus uptake by the trees. Soil magnesium is similarly correlated with bark calcium. Aluminum is the major exchangeable cation in soils of the poorer ridge sites which are the most acid. It is hypothesized that soil aluminum competes with other nutrient cations such as calcium and magnesium for sites of absorption on plant roots. In addition to the effect of soil pH on phosphate solubility, competition between aluminum ions and other cations may inhibit the absorption and uptake of calcium and phosphorus, both of which are important to the growth and nutrition of the Eucalyptus species in the study area.

ISSN:0012-9658    

DOI:10.2307/1933883

出版商:Ecological Society of America    

年代:1969

数据来源: WILEY

摘要:

An empirical test of the existence of higher order interactions was carried out using four ciliate protozoans, Paramecium caudatum, P. bursaria, P. aurelia, and Blepharisma sp. All four ciliates were cultured individually, and their population histories were described quite well by the simple logistic equation. Attempts to explain minor deviations of the data from the logistic by use of the one or two time lag logistic failed. A more complicated time lag phenomenon must be operative. Every possible pair of the four ciliates was cultured and a trial and error procedure was used to estimate @a and @b of the Gause equations. In all cases the simple Gause equations seemed adequately to describe the data. All four ciliates were cultured together and compared to predictions made by use of the competition coefficients estimated from pair—wise competition and population parameters estimated from single species population growth. The correspondence between prediction and data suggests that the higher order interactions have slight or no effect on the dynamics of this artificial community.

ISSN:0012-9658    

DOI:10.2307/1933884

出版商:Ecological Society of America    

年代:1969

数据来源: WILEY

摘要:

Investigations on aquatic insect activity, measured as drift in an artificial stream system with rigid light and temperature conditions, demonstrated a light—controlled, labile, exogenously—mediated activity rhythm. A threshold value for light, incident at the water surface, which when decreased led to high drift rates, and when increased suppressed activity, was determined to lie between 10—3and 10—4ft—c (10—2and 10—3lux). Preliminary experiments showed variations in wavelength to have little effect on the activity patterns of the insects.

ISSN:0012-9658    

DOI:10.2307/1933885

出版商:Ecological Society of America    

年代:1969

数据来源: WILEY

摘要:

Relationships among the phytoplankton standing crop, rate of photosynthesis, and the distribution of C—14 in primary products of photosynthesis were investigated in western Lake Erie from July to August 1965. Sixty species of phytoplankton were noted during the study, but only four species, Coscinodiscus sp, Ceratium hirundinella (O.F.M.) Schrank, Aphanizomenon flos—aquae (L) Ralfs, and Microcystis aeruginosa Kutz accounted for over 98% of the total cell volume. Cell volumes ranged from 10 to 282 mm3liter—1. Total photosynthesis (mgC m—3day—1) in the upper photic zone averaged 566, ranging from 55 to 1690. Relative photosynthesis (mgC day—1mm—3) ranged from 1.6 to 332. Ethanol—soluble C—14 fractions (mostly carbohydrate and lipids) of the phytoplankton accounted for 25—60% of the total C—14 assimilated. Insoluble C—14 fractions (mostly proteins) accounted for 20—48% of the total C—14 uptake. Large carbohydrate and small protein fractions occurred in Coscinodiscus standing crops under moderate illumination and in steady—state Alphanizomenon—Microcystis standing crops under high illumination. C—14 labeled protein fractions exceeded carbohydrate fractions in rapidly growing Aphanizomenon—Microcystis standing crops under moderate illumination and at the peak of a blue—green algae bloom under low illumination.

ISSN:0012-9658    

DOI:10.2307/1933886

出版商:Ecological Society of America    

年代:1969

数据来源: WILEY

摘要:

The relative distribution of the mallee eucalypts E. incrassata and E. socialis seems to be controlled by slight soil differences, with E. incrassata usually on soils both lower in nutrients and with a higher water—supplying capacity. Seedling monocultures in soils naturally supporting either species or both showed that the two species had closely comparable physiological tolerance to a wide range of macronutrients. In mixed cultures, F. incrassata had a competitive advantage in all soils at optimal water levels, but this was greatly reduced in a drought treatment. E. socialis seems to have superior drought avoidance related to higher root: shoot ratio and possibly to slower growth in competition. Drought susceptibility is shown to be positively correlated with soil fertility. E. incrassata may succumb to drought on the dry, fertile soils carrying E. socialis, whereas E. socialis may be out—competed by E. incrassata on wetter, less fertile sites.

ISSN:0012-9658    

DOI:10.2307/1933887

出版商:Ecological Society of America    

年代:1969

数据来源: WILEY

摘要:

A method of analyzing spatial pattern by serial regression is proposed. It involves regression of species frequencies on other frequencies of the same species recorded at increasing intervals of distance from the "dependent" record. If the regression coefficients are plotted against distance, positive peaks indicate the distance between individuals or clumps of the species, and negative peaks indicate the distance between clumps and spaces. The method is contrasted with the analysis of variance approach first proposed by Greig—Smith. Pattern analyses of crustose lichens on a limestone cliff are employed to illustrate application of the method and to facilitate comparison with the analysis of variance method.

ISSN:0012-9658    

DOI:10.2307/1933888

出版商:Ecological Society of America    

年代:1969

数据来源: WILEY

摘要:

Particulate organic matter of various size fractions larger than 44 μ in diameter was extracted from old—field and forest soils by flotation in aqueous solutions of magnesium sulfate. Extracted ash—free organic material comprised about 0.6% of the dry weight of both soils and from 15—20% of all the organice matter present in the soils. Particulate organic matter less than 44 μ in size accounted for 70% of the organic matter, the remaining 10—15% being water soluble. In the old—field soil, a direct relationship existed between caloric values and particle sizes with the exception of particles between 44—105 μ in size. Relationships between size and energy content of organic particles in the forest soil were not as clearcut, since several smaller size components in the upper 10 cm of the soil had greater caloric contents than larger sizes. The data are discussed in relation to decomposition processes and heterotrophic production in soil ecosystems.

ISSN:0012-9658    

DOI:10.2307/1933889

出版商:Ecological Society of America    

年代:1969

数据来源: WILEY

摘要:

Encelia farinosa is one of a number of species of desert perennial shrubs in which individuals exhibit considerable seasonal variation in the amount and structure of leaf tissue. The function of seasonal leaf variability in adapting this species to the desert environment was investigated. Field observations demonstrated that leaf quantity and structure are controlled by the moisture status of the environment. The field observations also established the influence which leaf quantity and structure have on the CO2exchange capacity and water status of the shrub. These observations were corroborated by laboratory experiments. The laboratory investigations also indicated that the influences of leaf structure are brought about by alterations in the resistances to CO2and water vapor diffusion.

ISSN:0012-9658    

DOI:10.2307/1933890

出版商:Ecological Society of America    

年代:1969

数据来源: WILEY

摘要:

Rates of deposition of pollen grains throughout late— and postglacial time were determined from the pollen concentration in radiocarbon—dated sediment. Changes by a factor of 5 or more for all except rate pollen types from one level to the next were considered significant indication of changes in the pollen input to the lake, reflecting changes in the pollen productivity of the surrounding vegetation. Low pollen deposition rates in the oldest sediments reflect the prevalence of tundra vegetation between 14,000 and 12,000 years ago. An increase in the rate for tree pollen occurred 12,000 years ago, when boreal woodland became established. The rates continued to increase until a sudden sharp rise for white pine, hemlock, poplar, oak, and maple pollen 9,000 years ago marked the establishment of forest, similar perhaps to modern forests of the northern Great Lakes region. Pine pollen rates decline 8,000 years ago, and deciduous tree pollen became dominant. Ragweed pollen was deposited at relatively high rates 8,000 years ago, reflecting changes in the vegetation associated with the "prairie period" recorded in the Great Lakes region at this time. Subsequent changes in pollen deposition rates reflect the immigration of beech (6,500 years B.P.), hickory (5,500 years B.P.), and chestnut (2,000 B.P.) to southern Connecticut. During the past few hundred years pollen deposition rates reflect changes in the vegetation caused by disturbance by European settlers. Throughout much of postglacial time the pollen assemblages deposited at Rogers Lake are different from assemblages known from modern sediment. This makes climatic interpretation difficult and suggest that the forest associations of the region as they are recognized now are of quite recent origin.

ISSN:0012-9658    

DOI:10.2307/1933891

出版商:Ecological Society of America    

年代:1969

数据来源: WILEY