Introductory Overview

David Greenland

Television images of floods, hurricanes, tornadoes, snow and ice storms, and drought conditions are among the most vivid that leap into our minds when we think of short-term climatic events and their often obvious and direct ecosystem responses. The images are so striking that they tend to crowd out thoughts of longer term events. Yet, in many cases, even the longer term climatic events are often represented by the media as some manifestation of an individual severe weather event. The LTER sites have experienced a wide variety of severe weather events. Some of these are discussed in various chapters of this book. However, many other noteworthy instances are not treated in these pages. For example, we do not discuss the playa at the Jornada LTER site that has experienced a 100-year return period storm that filled the normally dry lake with water and brought to the fore many life forms that were surprising to Jornada investigators. Neither do we have room for the work at the Hubbard Brook LTER site by researchers who have documented in detail the effects on their trees of one of the most severe ice storms of the last century. Several other short-term climatic events, such as the 1996 flood at the Andrews rain forest, are discussed in the chapters of this book beyond this first section. In Part I the focus is on hurricanes, drought, and the short-term climatic events and ecosystem responses in the Arctic LTER site in Alaska.

Emery Boose of the Harvard Forest LTER in central Massachusetts introduces a Harvard Forest study on the effects of hurricanes on forest ecosystems in chapter 2. A strong hurricane passed over central New England in 1938 and left an indelible memory both in the minds of the inhabitants who experienced it and on the landscape. This stimulated Harvard Forest researchers to investigate the past history of hurricanes in their region and even to simulate a hurricane in their forest and study its effects on the ecosystem. The latter has become one of the legendary classic experiments of the LTER program. It has also been natural for Harvard Forest researchers to extend their interest to other LTER sites that have experienced hurricanes. They are interested particularly in the Luquillo LTER site in Puerto Rico and, to a lesser extent, the former North Inlet site in South Carolina that suffered immensely from the passage of hurricane Hugo in 1989. Boose provides an interesting comparison on the hurricanes in New England and Puerto Rico and their impact on the respective ecosystems.

Another important event in the 20-year annals of LTER history is the drought of 1988 that affected the entire United States in one way or another. Kloeppel and his coworkers examine the effects of this event in chapter 3 with respect to tree mortality at the Coweeta LTER site in the mountain forests of North Carolina. The same drought caused major detrimental responses to the agricultural ecosystems of the north central region of the United States, where the Kellogg Biological Station LTER is located. In chapter 4, Gage provides a penetrating analysis of the effects of this drought not only for the Kellogg LTER but also for a much larger region. Finally, in this chapter 5, we turn our attention to one of the younger LTER sites, the Arctic site in northern central Alaska where the climate record began in the early 1970s. Hobbie and his coworkers describe the effects of low temperatures in the air and soil, the 8-month snow cover, the reduced amount of light energy for photosynthesis, the completely frozen streams from mid-September until mid-May, and the long duration of the ice cover on lakes.

LTER sites are well set up to systematically observe the effects of short-term climatic events. The chapters in part I demonstrate the different ways in which LTER research on climate variability and ecosystem response operates at this timescale.

0 0

Post a comment