Edward S. Deevey

Life tables for natural populations of animals.

In selecting from Deevey’s extensive review, we have tried to emphasize the different types of problems that arise in working with animal populations; our most serious omission is a detailed study of barnacles that examines crowding effects and mortality. Deevey begins his article with discussions of the life table and of different general survival patterns, which we also omit.

Yale Natural Radiocarbon Measurements VIII

No important instrumental modifications have been made since publication of our last list (Yale VII). As before, we are indebted to many collaborators for samples and for assistance with descriptions and comments. Technical assistance has been provided by George Young, Carolyn Haupt, and Jonathan Wood. The generous support of the National Science Foundation, under grants G-19080 (to Stuiver), G-19335 (to Deevey), and G-24049 (to Rouse) is gratefully acknowledged. As in our previous lists, dates are reported in terms of the Libby half life of C14, 5570 ± 30 yr, and geochemical measurements are expressed as ∆, the normalized deviation from 95 percent of the NBS oxalic-acid standard. Infinite dates are reported as beyond a limit equal to 3o above background.

Mayan Urbanism: Impact On a Tropical Karst Environment

From the first millennium B.C. through the 9th-century A.D. Classic Maya collapse, nonurban populations grew exponentially, doubling every 408 years, in the twin-lake (Yaxha-Sacnab) basin that contained the Classic urban center of Yaxha. Pollen data show that forests were essentially cleared by Early Classic time. Sharply accelerated slopewash and colluviation, amplified in the Yaxha subbasin by urban construction, transferred nutrients plus calcareous, silty clay to both lakes. Except for the urban silt, colluvium appearing as lake sediments has a mean total phosphorus concentration close to that of basin soils. From this fact, from abundance and distribution of soil phosphorus, and from continuing post-Maya influxes (80 to 86 milligrams of phosphorus per square meter each year), which have no other apparent source, we conclude that riparian soils are anthrosols and that the mechanism of long-term phosphorus loading in lakes is mass transport of soil. Per capita deliveries of phosphorus match physiological outputs, approximately 0.5 kilogram of phosphorus per capita per year. Smaller apparent deliveries reflect the nonphosphatic composition of urban silt; larger societal outputs, expressing excess phosphorus from deforestation and from food waste and mortuary disposal, are probable but cannot be evaluated from our data. Eutrophication is not demonstrable and was probably impeded, even in less-impacted lakes, by suspended Maya silt. Environmental strain, the product of accelerating agroengineering demand and sequestering of nutrients in colluvium, developed too slowly to act as a servomechanism, damping population growth, at least until Late Classic time.

Ecosystems, paleoecology and human disturbance in subtropical and tropical america

Abstract Human disturbances of ecosystems last a long time and have quantifiable influences on the structure and function of the systems. If long records (e.g. paleoecological) of both disturbances and the responses are available, the array of disturbances provides quasi-experimental treatments useful for the study of factors which govern ecosystems. This paper examines the paleoecology of a series of lake-drainage basin ecosystems that have been subject to disturbances which vary through time and space. In all cases studied, it has been demonstrated that human activities have increased the movement of materials from the catchment to the lake. Examples in Guatemala, Haiti and Florida demonstrate that the flow of macronutrients (nitrogen and phosphorus) is proportional to human population sizes, and that the flow of inorganic particulates is related to the nature of both the disturbances and the catchment. Lake eutrophication is driven by growing human populations, but the rate of increase can be slowed by activities such as urbanization, which increases siltation. Several tropical ecosystems have recovered from severe disturbances, but the rate of recovery was related to the severity and temporal extent of the disturbances.

Pollen Accumulation Rates: Estimates from Late-Glacial Sediment of Rogers Lake

Absolute pollen deposition in a Connecticut lake over a 4000-year interval has been estimated from pollen frequencies in a core of late-glacial sediment dated by radiocarbon techniques. The rate of total sediment accumulation as measured after burial was statistically constant at 0.036 centimeter per year, but the rate of deposition of pollen grains onto the sediment increased from 600 to 900 grains 14,000 years ago to 9000 per square centimeter per year 10,000 years ago. A major increase in the deposition of tree pollen occurred about 11,500 years ago, at the beginning of the spruce pollen zone. Presentation of data in conventional (percentage) form masks the magnitude of this change and distorts many of the changes in accumulation rates for individual types of pollen; moreover it magnifies statistical variation in the herb zone where all pollen is scarce.

Fractionation of Sulfur and Carbon Isotopes in a Meromictic Lake

In the permanently stagnant depths of Green Lake (near Syracuse, N.Y.), sulfide made by bacteria is depleted in heavy sulfur (S34), and sulfate is enriched. The fractionation factor, 1.0575, is the greatest yet observed. Isotopic resemblance to salt-dome sulfur deposits is evident, and, like saltdome calcite, the lakes carbon dioxide is depleted in heavy carbon (C13).

SEDIMENTS OF LAKE PATZCUARO, MICHOACAN, MEXICO

The recent sedimentary history of Lake Patzcuaro was investigated by pollen analysis in 1944, and a dry climatic phase, probably hundreds or thousands of years ago, seemed to be indicated by maximal abundance of nonarboreal (grass, chenopod, and composite) pollen. The work of Sears on Lake Texcoco, 250 km east, prompted a reinvestigation of the Patzcuaro pollen sequence and a study of the chemistry and the diatom flora of the sediment cores. On the basis of Sears9 Index of Humidity (the ratio of Quercus + Alnus + Abies pollen to the total arboreal pollen, which is minimal in the driest intervals when Pinus is most abundant), there is clear evidence of a dry phase within the zone of abundant nonarboreal pollen, but the latter now seems to have no direct climatic significance. Instead, since the nonarboreal pollen, particularly its chenopod (+ amaranth?) component, is most abundant during moist phases just preceding and just following the newly defined dry phase, the fluctuations of nonarboreal pollen seem to reflect agricultural practice and, ultimately, demographic history. The sequence as now interpreted correlates remarkably well with that from the Valley of Mexico, and, using the archaeologic dates that Sears established there, there are: zone D, pre-Archaic (before 1500 B.C.), dry; zone C, early and middle Archaic (1500–500 B.C.), moist; zone B, late Archaic-Teotihuacan (500 B.C.–A.D. 900), climate fluctuating, but with at least one markedly dry episode; zone A, Nahua (A.D. 900–1521), moist. The few archaeologic data and the folklore from the Patzcuaro region tend to confirm this interpretation. There are some differences between the Patzcuaro and the Texcoco pollen sequences, notably in the less well marked character of the last (moist) phase in Patzcuaro. Of particular interest is the evidence of relatively intense aridity shown in the cores at the inferred late Archaic or Teotihuacan level: a minimum of Sears9 Index corresponds to a strong increase in the calcium content of the sediments, and to a zone having only shallow-water benthic and littoral diatoms, above and below which the normal planktonic diatom flora is recorded. The two independent evidences for increased evaporation or reduced rainfall suggest that the dry phase was due to climatic causes and not to culture or volcanism.

Sedimentary records of accelerated nutrient loading in Florida lakes

Transfer functions relating trophic state (Carlsons TSIchlorophyll-a) to present day accumulation rate of (1) nutrients, (2) cations, and (3) organic sediment, are computed using Binfords 210Pb-dilution method. As computed from surficial sediments of 27 lakes, former trophic states are reconstructed for recent (210Pb-dated) sedimentary histories of 14 lakes. Of the three kinds of models potentially available, model (3) (TSI vs. organic accumulation) is the weakest statistically, and may be unduly influenced by exceptional deposition and/or preservation of allochthonous organic matter. At present, however, it is the only model applicable to all 14 of the histories tested. Results are encouraging in that model accurately predicts observed TSIs in several mesotrophic and eutrophic lakes. Clearly significant increases (accelerations) are inferred only for a of the most eutrophic lakes of the set, while the model consistently overpredicts TSIs of the 7 most oligotrophic lakes. As Whitmores diatom-assemblage index is a better predictor of TSI than is model (3) in the one eutrophic lake in which it has been tested, we expect more persuasive results when models (1) and (2) can be tested within a more complete set of analytical data. We were surprised to find 3 severely disturbed lakes among the 12 that show little or no acceleration in rate of eutrophication in recent decades, but we defer attempts at explanation until former nutrient loading can be tested by model (1).