Sensitivity of Cool-Temperate Forests and their Fossil Pollen Record to Rapid Temperature Change

Abstract Simulations of cool-temperate forest growth in response to climatic change using the JABOWA computer model show that a decrease of 600 growing degree-days (equivalent to a 2°C decrease in mean annual temperature) causes red spruce ( Picea rubens ) to replace sugar maple ( Acer saccharum ) as the dominant tree. These changes are delayed 100–200 yr after the climatic cooling, producing gradual forest changes in response to abrupt temperature changes, and reducing the amplitude of response to brief climatic events. Soils and disturbances affect the speed and magnitude of forest response. The delayed responses are caused by the difference in sensitivity of adult trees and younger stages. The length of the delay depends on the life history characteristics of the dominant species. Delayed responses imply that fossil pollen deposits, even if they faithfully record the abundances of trees in forests, may not be able to resolve climatic changes within 100–200 yr, or to record very brief climatic events. This explains why pollen deposits do not as yet show responses to climatic changes during the past 100 yr. Only the Little Ice Age, which lasted several centuries, caused sufficient forest change to be recorded in fossil pollen, and only at certain sites.

[1]  T. Webb,,et al.  Estimating plant abundances from pollen percentages: The use of regression analysis , 1981 .

[2]  T. Siccama,et al.  Decline of Red Spruce in the Green Mountains of Vermont , 1982 .

[3]  V. Lamarche.  Holocene Climatic Variations Inferred from Treeline Fluctuations in the White Mountains, California , 1973, Quaternary Research.

[4]  E. W. Wahl.  A COMPARISON OF THE CLIMATE OF THE EASTERN UNITED STATES DURING THE 1830's WITH THE CURRENT NORMALS , 1968 .

[5]  A. Smith.  Problems of inertia and threshold related to post-Glacial habitat changes , 1965, Proceedings of the Royal Society of London. Series B. Biological Sciences.

[6]  H. Shugart,et al.  Patterns and Dynamics of Forests: An Application of Simulation Models , 1981 .

[7]  R. Brugam.  Pollen Indicators of Land-Use Change in Southern Connecticut , 1978, Quaternary Research.

[8]  J. Aber,et al.  Predicting the effects of different harvesting regimes on productivity and yield in northern hardwoods , 1979 .

[9]  E. Grimm.  CHRONOLOGY AND DYNAMICS OF VEGETATION CHANGE IN THE PRAIRIE‐WOODLAND REGION OF SOUTHERN MINNESOTA, U.S.A. * , 1983 .

[10]  C. W. Thornthwaite,et al.  Instructions and tables for computing potential evapotranspiration and the water balance , 1955 .

[11]  Daniel B. Botkin,et al.  Predicting the effects of different harvesting regimes on forest floor dynamics in northern hardwoods , 1978 .

[12]  M. Davis.  Climatic interpretation of pollen in quaternary sediments , 1978 .

[13]  G. Likens,et al.  Pattern and process in a forested ecosystem. , 1979 .

[14]  G. Likens,et al.  The Hubbard Brook Ecosystem Study: Composition and Dynamics of the Tree Stratum , 1970 .

[15]  J. R. Wallis,et al.  Some ecological consequences of a computer model of forest growth , 1972 .

[16]  J. Bernabo,et al.  Quantitative Estimates of Temperature Changes Over the Last 2700 Years in Michigan Based on Pollen Data , 1981, Quaternary Research.

[17]  T. Anderson.  The Chestnut Pollen Decline as a Time Horizon in Lake Sediments in Eastern North America , 1974 .

[18]  M. B. Davis,et al.  Holocene Climate of New England , 1980, Quaternary Research.