Preface ix 



mensional. Although the reader may begin and end at any point, he must 

 proceed Hnearly between those points. We view ecosystems as mukidi- 

 mensional, with complex lines of interaction and influence running 

 throughout. In resolving this complexity into the linear structure of this 

 volume, we have fallen back on the relatively familiar divisions of abiotic 

 setting, primary production processes, soil and decomposition processes, 

 and herbivory. Within each of these subdivisions, the reader will find the 

 common theme of the limitation of rates of biological processes by low 

 temperature and related conditions of short growing season and the pres- 

 ence of permafrost. 



The Editors 



