Introduction
xxi
canopy insectivores in Chile and a greater diversity of leaf gleaners and
understory birds in Alaska. Much of the contrast in community structure
between Chile and Alaska is hypothesized to be due to the architectural
differences between broadleaf and coniferous forests , but none of the
measures tested are able to explain the differences in community structure
that are observed.
Bird pollination and seed dispersal are important to the maintenance of
forest species diversity in coastal temperate rainforests on Chiloe Island.
Armesto and his coworkers found that one species of migrant frugiver
bird accounts for nearly half the fruit consumption in these forests. Bird
pollination is much more widespread and occurs throughout the year in
Chile. The effects of loggingand land-clearing activities on the maintenance
of species richness are particularly prominent in this rainforest, since
fragmentation tends to be associated with a decline in these key fruiteating and pollinator bird species. Biotic interactions are more important
to the maintenance of biodiversity in Chile than in North America.
Freshwater ecosystems show parallel trends with rainforests in terms of
evolutionary history and unique community structures. Soto and Stockner
compare the physical and biotic features of lakes in Chile and corresponding
rainforest regions in southern British Columbia. The lakes in both regions
are similar in chemistry, ontogeny , and geomorphology but contrast in
temperature, productivity, and food web structure. These ecosystem
features suggest that they are similar in chemistry , ontogeny, and geomorphology but contrast in temperature, productivity , and food web
structure. These ecosystem features suggest that Chilean lakes may be
more sensitive to introductions of exotic species and to the effects of
logging on water chemistry than lakes in British Columbia.
Forest System Responses to Human Activities
The third and final section of the book summarizes techniques available
for assessing the influence of human activities on the high-latitude ecosystems and discusses some of the management strategies and policies that
are being undertaken or proposed to address the management of highlatitude forests. A new understanding of the importance of spatial gradients
is leading to the development of new tools for analyzing and managing
terrestrial ecosystems at the landscape level.
Bradshaw and her associates report on a technique for analyzing scale
interactions in forest environments, using the concepts of patch dynamics
and hierarchy theory. Landscape composition and rates of landscape
change are determined by local patch-matrix interactions and patterns.
When the rates of landscape change due to local processes are slow
relative to large-scale changes, successional patterns will be more severely
displaced. The results of these modeling studies raise additional questions
xxi
canopy insectivores in Chile and a greater diversity of leaf gleaners and
understory birds in Alaska. Much of the contrast in community structure
between Chile and Alaska is hypothesized to be due to the architectural
differences between broadleaf and coniferous forests , but none of the
measures tested are able to explain the differences in community structure
that are observed.
Bird pollination and seed dispersal are important to the maintenance of
forest species diversity in coastal temperate rainforests on Chiloe Island.
Armesto and his coworkers found that one species of migrant frugiver
bird accounts for nearly half the fruit consumption in these forests. Bird
pollination is much more widespread and occurs throughout the year in
Chile. The effects of loggingand land-clearing activities on the maintenance
of species richness are particularly prominent in this rainforest, since
fragmentation tends to be associated with a decline in these key fruiteating and pollinator bird species. Biotic interactions are more important
to the maintenance of biodiversity in Chile than in North America.
Freshwater ecosystems show parallel trends with rainforests in terms of
evolutionary history and unique community structures. Soto and Stockner
compare the physical and biotic features of lakes in Chile and corresponding
rainforest regions in southern British Columbia. The lakes in both regions
are similar in chemistry, ontogeny , and geomorphology but contrast in
temperature, productivity, and food web structure. These ecosystem
features suggest that they are similar in chemistry , ontogeny, and geomorphology but contrast in temperature, productivity , and food web
structure. These ecosystem features suggest that Chilean lakes may be
more sensitive to introductions of exotic species and to the effects of
logging on water chemistry than lakes in British Columbia.
Forest System Responses to Human Activities
The third and final section of the book summarizes techniques available
for assessing the influence of human activities on the high-latitude ecosystems and discusses some of the management strategies and policies that
are being undertaken or proposed to address the management of highlatitude forests. A new understanding of the importance of spatial gradients
is leading to the development of new tools for analyzing and managing
terrestrial ecosystems at the landscape level.
Bradshaw and her associates report on a technique for analyzing scale
interactions in forest environments, using the concepts of patch dynamics
and hierarchy theory. Landscape composition and rates of landscape
change are determined by local patch-matrix interactions and patterns.
When the rates of landscape change due to local processes are slow
relative to large-scale changes, successional patterns will be more severely
displaced. The results of these modeling studies raise additional questions