LITTER PRODUCTION I N FORESTS O F THE WORLD
125
by Lutz and Chandler (1946). Many more recent references may be
found in the bibliography at the end of this review. Analyses for several
of the minor elements have been made by Scott (1955).
E. ORGANIC MATERIAL
The organic fractions of forest litter are not a t all well known. Crude
proximate analyses of fresh leaf litter from four Gymnosperm and four
Angiosperm tree species in eastern North America were carried out
according to the methods of Waksman (see Handley, 1954) by Melin
(1930), and a similar series of analyses is available for four Angiosperm
and four Gymnosperm species in Finland (Mikola, 1954). These may be of
interest to persons concerned with the possible utilization of leaf litter.
Ether soluble components ranged from 4 to 12% dry weight, coldwater soluble organic matter from 3 to 14%, hot-water soluble organic
matter from 3 to 9yo, and alcohol soluble organic material from 3 to 13%.
“Hemicelluloses”, estimated crudely from sugars produced by dilute
acid hydrolysis of alkali extracts, ranged from 10 to 19% dry weight.
“Celluloses” , also crudely estimated by treatment of hemicellulose
residues with Schweitzer’s reagent, ranged from 10 to 22%. “Ligninhumus”, the residue remaining after extraction of litter with a mixture
containing 10 ml of 18% HC1 and 50 ml of 72% H,SO,, ranged from
5 to 33%. “Crude protein”, estimated by subtracting water-soluble
from total nitrogen and multiplying the result by 6.25, ranged from
2 to 15% dry weight. Differences between Gymnosperms and Angiosperms were not consistent. Handley (1954), in discussing such analyses,
cites some by Wittich (using methods somewhat different from those
above) of German Angiosperm tree litter. These give the following
ranges, as percentage of ash-free d q matter: ether soluble 6-14, coldwater soluble 6-25, hot-water soluble P 1 0 , alcohol soluble 2-5, hemicelluloses 25-36, celluloses 7-25, lignin-humus 11-30 and lignin (by
acetyl bromide separation) < 1-8.
Nykvist (1963) has recently investigated the water-soluble aminoacids, sugars and aliphatic acids in Angiosperm and Gymnosperm litter
from Swedish forest tree species.
V. FACTORS AFFECTING LITTER-FALL
A. EVERGREEN GYMNOSPERMS AND DECIDUOUS ANGIOSPERMS
Because of their evergreen nature, Gymnosperms might be expected
to be more productive than deciduous Angiosperm trees, although this
factor may be countered to some extent by the tendency for Angiosperm forests to occupy more fertile sites. As far as litter-fall is concerned, Table X indicates that when a wide range of sites is considered
I2
C.E.R.
125
by Lutz and Chandler (1946). Many more recent references may be
found in the bibliography at the end of this review. Analyses for several
of the minor elements have been made by Scott (1955).
E. ORGANIC MATERIAL
The organic fractions of forest litter are not a t all well known. Crude
proximate analyses of fresh leaf litter from four Gymnosperm and four
Angiosperm tree species in eastern North America were carried out
according to the methods of Waksman (see Handley, 1954) by Melin
(1930), and a similar series of analyses is available for four Angiosperm
and four Gymnosperm species in Finland (Mikola, 1954). These may be of
interest to persons concerned with the possible utilization of leaf litter.
Ether soluble components ranged from 4 to 12% dry weight, coldwater soluble organic matter from 3 to 14%, hot-water soluble organic
matter from 3 to 9yo, and alcohol soluble organic material from 3 to 13%.
“Hemicelluloses”, estimated crudely from sugars produced by dilute
acid hydrolysis of alkali extracts, ranged from 10 to 19% dry weight.
“Celluloses” , also crudely estimated by treatment of hemicellulose
residues with Schweitzer’s reagent, ranged from 10 to 22%. “Ligninhumus”, the residue remaining after extraction of litter with a mixture
containing 10 ml of 18% HC1 and 50 ml of 72% H,SO,, ranged from
5 to 33%. “Crude protein”, estimated by subtracting water-soluble
from total nitrogen and multiplying the result by 6.25, ranged from
2 to 15% dry weight. Differences between Gymnosperms and Angiosperms were not consistent. Handley (1954), in discussing such analyses,
cites some by Wittich (using methods somewhat different from those
above) of German Angiosperm tree litter. These give the following
ranges, as percentage of ash-free d q matter: ether soluble 6-14, coldwater soluble 6-25, hot-water soluble P 1 0 , alcohol soluble 2-5, hemicelluloses 25-36, celluloses 7-25, lignin-humus 11-30 and lignin (by
acetyl bromide separation) < 1-8.
Nykvist (1963) has recently investigated the water-soluble aminoacids, sugars and aliphatic acids in Angiosperm and Gymnosperm litter
from Swedish forest tree species.
V. FACTORS AFFECTING LITTER-FALL
A. EVERGREEN GYMNOSPERMS AND DECIDUOUS ANGIOSPERMS
Because of their evergreen nature, Gymnosperms might be expected
to be more productive than deciduous Angiosperm trees, although this
factor may be countered to some extent by the tendency for Angiosperm forests to occupy more fertile sites. As far as litter-fall is concerned, Table X indicates that when a wide range of sites is considered
I2
C.E.R.