L I T T E R PRODUCTION I N FORESTS OF T H E WORLD
127
greater total litter production by the deciduous F q u s silvatica, 3.8 t/ha,
than by the evergreens Picea abies, 3.5 t/ha, and Pinus silvestris,
3.0 t/ha. If only Ebermayer’s individual data are examined a somewhat
different situation is evident, with Fagus averaging 3.3, Pinus 3.2 and
Picea 3.0 t/ha (Lutz and Chandler, 1946).
B. ENVIRONMENT
7. Climate and Latitude
The predominant influence of climate upon litter production is shown
in a general way by Table XI, which summarizes the data for major
climatic zones. In Arctic-Alpine forests total litter production averages
1 t/ha annually, while in Equatorial forests the mean is almost 11 t/ha.i
Cool and Warm Temperate forests average 3.5 and 5-5 t/ha respectively.
In round figures the ratios are about 1 : 3 : 5 : 10 for the major climatic
zones.
The range of mean annual temperature spanned by these climatic
zones is from below freezing for the most northerly Arctic forests to
about 25°C for those of the hottest Equatorial regions. From a biological standpoint the length of the period when temperatures are
above freezing is also important. It is of course year-long in the Equatorial forests, and almost so in the Warm Temperate stands; but in
Arctic-Alpine regions the mean daily temperature may be above freezing
for 6 months or less. The growing season may be considerabIy shorter,
for example Paterson (1961) indicates that in parts of northern Fennoscandia the growing season for Gymnosperm forests may be as short as
3 months per annum, while in .Cool Temperate forests it is often about
6 to 7 months in duration.
Associated with the higher temperature and longer growing season
of the Equatorial zone is the greater amount of insolation during the
period of photosynthesis. This must be of considerable importance for
primary productivity. Some preliminary calculations based on maps of
Black (1956) suggest that the total amount of solar radiation received
during the growing season is roughly in the proportion of 1 : 3 : 5 for
extreme Arctic-Alpine, Cool Temperate and Equatorial sites. In the
Arctic-Alpine sites it is probably less effectively utilized owing to the
more open nature of the forest and to the relative coldness of the soil.
Data for both leaf and other litter, while less extensive than those for
total litter, bear out the general climatic relationship. (In this cont I n view of the scarcity of tropical data it may be of interest to note a total annual
litter-fall of 14 t/ha by Eucalyptus in Brazil, measured over 8 years (Navarro de Andrade,
1941). This value has not been included in the tables because no further information ia
available, particularly as to whether this is dry weight (though it seems unlikely to be
otherwise).
127
greater total litter production by the deciduous F q u s silvatica, 3.8 t/ha,
than by the evergreens Picea abies, 3.5 t/ha, and Pinus silvestris,
3.0 t/ha. If only Ebermayer’s individual data are examined a somewhat
different situation is evident, with Fagus averaging 3.3, Pinus 3.2 and
Picea 3.0 t/ha (Lutz and Chandler, 1946).
B. ENVIRONMENT
7. Climate and Latitude
The predominant influence of climate upon litter production is shown
in a general way by Table XI, which summarizes the data for major
climatic zones. In Arctic-Alpine forests total litter production averages
1 t/ha annually, while in Equatorial forests the mean is almost 11 t/ha.i
Cool and Warm Temperate forests average 3.5 and 5-5 t/ha respectively.
In round figures the ratios are about 1 : 3 : 5 : 10 for the major climatic
zones.
The range of mean annual temperature spanned by these climatic
zones is from below freezing for the most northerly Arctic forests to
about 25°C for those of the hottest Equatorial regions. From a biological standpoint the length of the period when temperatures are
above freezing is also important. It is of course year-long in the Equatorial forests, and almost so in the Warm Temperate stands; but in
Arctic-Alpine regions the mean daily temperature may be above freezing
for 6 months or less. The growing season may be considerabIy shorter,
for example Paterson (1961) indicates that in parts of northern Fennoscandia the growing season for Gymnosperm forests may be as short as
3 months per annum, while in .Cool Temperate forests it is often about
6 to 7 months in duration.
Associated with the higher temperature and longer growing season
of the Equatorial zone is the greater amount of insolation during the
period of photosynthesis. This must be of considerable importance for
primary productivity. Some preliminary calculations based on maps of
Black (1956) suggest that the total amount of solar radiation received
during the growing season is roughly in the proportion of 1 : 3 : 5 for
extreme Arctic-Alpine, Cool Temperate and Equatorial sites. In the
Arctic-Alpine sites it is probably less effectively utilized owing to the
more open nature of the forest and to the relative coldness of the soil.
Data for both leaf and other litter, while less extensive than those for
total litter, bear out the general climatic relationship. (In this cont I n view of the scarcity of tropical data it may be of interest to note a total annual
litter-fall of 14 t/ha by Eucalyptus in Brazil, measured over 8 years (Navarro de Andrade,
1941). This value has not been included in the tables because no further information ia
available, particularly as to whether this is dry weight (though it seems unlikely to be
otherwise).