7. Biodiversity Patterns in Relation to Climate
127
Ecosystem recovery following disturbance, especially that from forest
clearing, appears to take longer in northern temperate rainforests than in
other forest types (Veblen & Alaback, this volume). Old-growth forests
may develop following catastrophic disturbance in as little as 200 years
in the mesophytic (Pseudotsuga) forest type in the Oregon Cascades
(Franklin et al., 1981; Spies & Franklin, 1991). In northern temperate
rainforests, by contrast , many understory species appear to require the
disturbance or microclimate associated with canopy gaps in mature forest
to maintain viable populations (Alaback, 1982; Tappeiner & Alaback,
1989). It may take 3 or 4 centuries for upland forests, or even longer in
riparian ecosystems, to develop the species richness of primary rainforest,
although at some younger successional stages, high levels of diversity may
be achieved for short periods of time. Riparian ecosystems provide the
highest level of diversity and best representation of specialized habitats,
so these should be key habitats for development of conservation strategies
in temperate rainforest regions. They provide critical habitat for aquatic
species, including many commercial fish species. Riparian zones also have
the highest economic values for trees, are used for transportation corridors, and have high value for recreation; thus, they are a focal point for
land-use decisions in general as well as for biodiversity. Relatively few
pristine riparian forests exist on the Pacific coast, most of them in Alaska
and British Columbia. Fewer still exist on larger stream systems. In most
cases, a focus on the maintenance of biodiversity in riparian systems will
require considerable attention on ecological restoration.
Careful monitoring of biodiversity changes with climate change and
human land-use changes should provide a useful barometer of ecosystemand landscape-level functioning, especially for rare or specialized species.
Development of conservation strategies for maintaining biodiversity
should complement management strategies that might be developed for
promoting greater ecosystem sustainability and for promoting wildlife
values of forests. Because of the overall similarity of climate and biodiversity patterns of the principal temperate rainforest regions of the
world, these bioregions would seem to be particularly valuable places to
focus future effort on comparing the cumulative effects of land-use change
and climate change across the contrasting gradients of North America and
the Southern Hemisphere.
References
Adams, W.T. 1992. Gene dispersal within forest tree populations. New For, 6,
217-240.
Adams , W.T., and Birkes, D.S. 1990. Estim ating mating patterns in forest tree
populations. Proceedings of the International Workshop on Plant Biology,
Biochemical Markers in Population Genetics of Forest Trees. Institute for
Agroforestry of the National Research Council of Italy, Porano-Orvieto, Italy.
127
Ecosystem recovery following disturbance, especially that from forest
clearing, appears to take longer in northern temperate rainforests than in
other forest types (Veblen & Alaback, this volume). Old-growth forests
may develop following catastrophic disturbance in as little as 200 years
in the mesophytic (Pseudotsuga) forest type in the Oregon Cascades
(Franklin et al., 1981; Spies & Franklin, 1991). In northern temperate
rainforests, by contrast , many understory species appear to require the
disturbance or microclimate associated with canopy gaps in mature forest
to maintain viable populations (Alaback, 1982; Tappeiner & Alaback,
1989). It may take 3 or 4 centuries for upland forests, or even longer in
riparian ecosystems, to develop the species richness of primary rainforest,
although at some younger successional stages, high levels of diversity may
be achieved for short periods of time. Riparian ecosystems provide the
highest level of diversity and best representation of specialized habitats,
so these should be key habitats for development of conservation strategies
in temperate rainforest regions. They provide critical habitat for aquatic
species, including many commercial fish species. Riparian zones also have
the highest economic values for trees, are used for transportation corridors, and have high value for recreation; thus, they are a focal point for
land-use decisions in general as well as for biodiversity. Relatively few
pristine riparian forests exist on the Pacific coast, most of them in Alaska
and British Columbia. Fewer still exist on larger stream systems. In most
cases, a focus on the maintenance of biodiversity in riparian systems will
require considerable attention on ecological restoration.
Careful monitoring of biodiversity changes with climate change and
human land-use changes should provide a useful barometer of ecosystemand landscape-level functioning, especially for rare or specialized species.
Development of conservation strategies for maintaining biodiversity
should complement management strategies that might be developed for
promoting greater ecosystem sustainability and for promoting wildlife
values of forests. Because of the overall similarity of climate and biodiversity patterns of the principal temperate rainforest regions of the
world, these bioregions would seem to be particularly valuable places to
focus future effort on comparing the cumulative effects of land-use change
and climate change across the contrasting gradients of North America and
the Southern Hemisphere.
References
Adams, W.T. 1992. Gene dispersal within forest tree populations. New For, 6,
217-240.
Adams , W.T., and Birkes, D.S. 1990. Estim ating mating patterns in forest tree
populations. Proceedings of the International Workshop on Plant Biology,
Biochemical Markers in Population Genetics of Forest Trees. Institute for
Agroforestry of the National Research Council of Italy, Porano-Orvieto, Italy.