Introduction
xvii
as compared to other temperate-latitude forest types, reflecting both a
complex disturbance history and a moist, moderate climate.
Temperate and high-latitude rainforests are generally divided into four
distinctive subtypes that can be defined by temperature, seasonality of
rainfall, and natural disturbance regimes. The highest-latitude rainforest
type, the subpolar rainforest , has high" rainfall equitably distributed
throughout the year but also a significant winter snowpack (especially in
the Northern Hemisphere). Subpolar rainforests also have low species
diversity and small, highly fragmented forest patches. Perhumid rainforests
are warmer , more extensive, and much more diverse but still have
abundant rainfall year-round. The seasonal rainforest type is transitional
to mesophytic temperate forests , in that summer rainfall is low and
catastrophic fires, although infrequent, playa key role in natural disturbance regimes. The warm temperate rainforest is the lowest-latitude extratropical rainforest type and has even less summer rainfall and a more
frequent occurrence of fire than the seasonal rainforest type. This forest
type is sometimes considered a wet subtype within the Mediterranean
climatic zone.
Timber harvesting associated with development activities is a common
environmental stress on forests in both hemispheres. Temperate rainforests
on the west coasts of North and South America are being exploited as
quickly as tropical forests, but because they occupy a much smaller
fraction of the global land base than tropical regions they are potentially
at greater risk. Not only do these rainforests play an essential role in the
global carbon balance, because they serve as a carbon sink, but they also
are an important source of revenue to the resource-dependent economies
of American countries with coastal boundaries. In South America , the
introduction of new tree species to improve forest productivity is further
altering the biogeochemical balance, the regional hydrological cycle, and
habitats for plants and animals.
In this book , we examine both physical processes that drive ecosystem
functions in temperate and high-latitude rainforests and the historical
factors that led to the development of this unique biome. Important
local-scale effects arise from the complex biological interrelations that
occur in these rainforests and from the effects of human uses on their
associated ecosystems and landscapes.
Physical Processes and Patterns
The first section of this book deals with abiotic factors and processes that
influence the distribution of biotic patterns in both space and time and the
complex interactions between these factors. The north-south variations
in forest structure are driven by climate as well as genetic pool structure
and local geomorpholog y.
xvii
as compared to other temperate-latitude forest types, reflecting both a
complex disturbance history and a moist, moderate climate.
Temperate and high-latitude rainforests are generally divided into four
distinctive subtypes that can be defined by temperature, seasonality of
rainfall, and natural disturbance regimes. The highest-latitude rainforest
type, the subpolar rainforest , has high" rainfall equitably distributed
throughout the year but also a significant winter snowpack (especially in
the Northern Hemisphere). Subpolar rainforests also have low species
diversity and small, highly fragmented forest patches. Perhumid rainforests
are warmer , more extensive, and much more diverse but still have
abundant rainfall year-round. The seasonal rainforest type is transitional
to mesophytic temperate forests , in that summer rainfall is low and
catastrophic fires, although infrequent, playa key role in natural disturbance regimes. The warm temperate rainforest is the lowest-latitude extratropical rainforest type and has even less summer rainfall and a more
frequent occurrence of fire than the seasonal rainforest type. This forest
type is sometimes considered a wet subtype within the Mediterranean
climatic zone.
Timber harvesting associated with development activities is a common
environmental stress on forests in both hemispheres. Temperate rainforests
on the west coasts of North and South America are being exploited as
quickly as tropical forests, but because they occupy a much smaller
fraction of the global land base than tropical regions they are potentially
at greater risk. Not only do these rainforests play an essential role in the
global carbon balance, because they serve as a carbon sink, but they also
are an important source of revenue to the resource-dependent economies
of American countries with coastal boundaries. In South America , the
introduction of new tree species to improve forest productivity is further
altering the biogeochemical balance, the regional hydrological cycle, and
habitats for plants and animals.
In this book , we examine both physical processes that drive ecosystem
functions in temperate and high-latitude rainforests and the historical
factors that led to the development of this unique biome. Important
local-scale effects arise from the complex biological interrelations that
occur in these rainforests and from the effects of human uses on their
associated ecosystems and landscapes.
Physical Processes and Patterns
The first section of this book deals with abiotic factors and processes that
influence the distribution of biotic patterns in both space and time and the
complex interactions between these factors. The north-south variations
in forest structure are driven by climate as well as genetic pool structure
and local geomorpholog y.