7. Biodiversity Pattern s in Relation to Climate
107
Dyrness, 1973; Pojar et al. , 1987). These zones correspond to mean
annual temperatures of 4°e, T'C , lOoe, and 12
0
e and growing-degree
days (>5°C) from less than 800 to more than 2000 (Farr & Harris , 1979;
Lawford, this volume) .
Temperate rainforest regions are distinguished from other western
temperate forest types by cool annual temperatures and the equability of
climate over the year , as shown in Figure 7.1. Whereas a high degree of
similarity occurs among the climates of temperate rainforest regions over
a wide range in latitude, the climates of interior continental areas vary
widely with latitude. In the southern extent of coastal forest , adjacent
climatic zones include Mediterranean and semidesert as well as montane
zones. In the seasonal zone, interior forests include high-elevation xeric
pine and mesophytic types. In the subpolar zone, rainforest rapidly gives
way to boreal forest and tundra. The boreal zone is the most distinctive,
with the highest degree of annual variation and lowest temperatures.
During the growing season , however, the boreal zone has similar temperatures to the subpolar rainforest zone. Xeric and mesophytic forests
(e.g. , Pinus ponderosa and Pseudotsuga menziesii respectively) are
distinguished from temperate rainforests mostly by the greater degree of
annual variation in temperature, but , except at the highest latitudes or at
high elevations , also tend to be significantlywarmer , especially during the
~real
30
!!! 25
~
li!
~eric
Q)
Co
E 20
Q)
...
.s
Q)
15
.subpolar
Mlerhumid
~esophytic
Cl
c
.seasonal
ca 10
.Warm temperate
~
Chile-Seasonal
Chile-Perhumid
c
c
0
Rainforest
o Rainforest
-c 5
0
·2
0
2
4
6
8
10
12
14
MeanAnnual Temperature
Figure 7.1. Climates of Pacific forest types. Means based on 20-30 year climate
normals from U.S. Weather Service and Environment Canada Atmospheric
Environment Service from the Pacific coast east to the eastern foothills of the
Cascade-Sierra Range and the British Columbia Coast Range crest. Xeric forests
represent those dominated by Pinus ponderosa . Mesic forests represent those
dominated by Pseudotsuga menziesii in the western Cascades.
107
Dyrness, 1973; Pojar et al. , 1987). These zones correspond to mean
annual temperatures of 4°e, T'C , lOoe, and 12
0
e and growing-degree
days (>5°C) from less than 800 to more than 2000 (Farr & Harris , 1979;
Lawford, this volume) .
Temperate rainforest regions are distinguished from other western
temperate forest types by cool annual temperatures and the equability of
climate over the year , as shown in Figure 7.1. Whereas a high degree of
similarity occurs among the climates of temperate rainforest regions over
a wide range in latitude, the climates of interior continental areas vary
widely with latitude. In the southern extent of coastal forest , adjacent
climatic zones include Mediterranean and semidesert as well as montane
zones. In the seasonal zone, interior forests include high-elevation xeric
pine and mesophytic types. In the subpolar zone, rainforest rapidly gives
way to boreal forest and tundra. The boreal zone is the most distinctive,
with the highest degree of annual variation and lowest temperatures.
During the growing season , however, the boreal zone has similar temperatures to the subpolar rainforest zone. Xeric and mesophytic forests
(e.g. , Pinus ponderosa and Pseudotsuga menziesii respectively) are
distinguished from temperate rainforests mostly by the greater degree of
annual variation in temperature, but , except at the highest latitudes or at
high elevations , also tend to be significantlywarmer , especially during the
~real
30
!!! 25
~
li!
~eric
Q)
Co
E 20
Q)
...
.s
Q)
15
.subpolar
Mlerhumid
~esophytic
Cl
c
.seasonal
ca 10
.Warm temperate
~
Chile-Seasonal
Chile-Perhumid
c
c
0
Rainforest
o Rainforest
-c 5
0
·2
0
2
4
6
8
10
12
14
MeanAnnual Temperature
Figure 7.1. Climates of Pacific forest types. Means based on 20-30 year climate
normals from U.S. Weather Service and Environment Canada Atmospheric
Environment Service from the Pacific coast east to the eastern foothills of the
Cascade-Sierra Range and the British Columbia Coast Range crest. Xeric forests
represent those dominated by Pinus ponderosa . Mesic forests represent those
dominated by Pseudotsuga menziesii in the western Cascades.