1954-Litter_Production_in_Forests_of_the_World

Prévia do material em texto

Litter Production in Forests of the Worldt 
J . R O G E R B R A Y 
Grasslands Division. D.S.I.R., Palmerston North. 
New Zealand 
and 
E V I L L E GORHAM 
Botany Department. University of Minnesota. 
Minneapolis. Minn., U . S. A .. 
I . Introduction ........................................................ 101 
I1 . SourcesofData ...................................................... 104 
A . UnpublishedStudybyJ.R.Bray ................................... 104 
B . WorldReview .................................................... 106 
I11 . Selection and Presentation of Data ..................................... 107 
A . Criteriafor Acceptance ............................................ 107 
B . Arrangement ..................................................... 108 
IV . Litter Components ................................................... 118 
A . Detailed Litter Separation ......................................... 118 
B . Percentage of Non-Leaf Litter ...................................... 118 
C . Understory Litter ................................................ 119 
D . MineralMaterial .................................................. 121 
E . OrganicMaterial .................................................. 125 
V . Factors Affecting Litter-Fall .......................................... 125 
A . Evergreen Gymnosperm and Deciduous Angiosperms ................. 125 
B . Environment ..................................................... 127 
C . Treatment ....................................................... 131 
D . TheTimeFactor ................................................. 133 
VI . StandingCropofLeaves .............................................. 142 
A . SeasonalChanges-Intrinsic ...................................... 142 
B . Seasonal Changes - Extrinsic ....................................... 144 
C . MagnitudeofLeafCrops ........................................... 144 
VII . Leaf Litter as an Index to Net Production ............................... 147 
References ................................................................ 152 
I . INTRODUCTION 
The organic debris shed by forest vegetation upon the surface of the 
soil has long engaged attention . In the past. branches and twigs were 
staff of the University of Toronto. Canada . 
t This study formed part of the authors’ research programmes while they were on the 
102 J . ROGER BRAY AND EVILLE GORHAM 
used as fuel, and leaves as bedding for farm animals or as a soil treat- 
ment. In Germany such utilization prompted concern over site degrada- 
tion, and provided a stimulus for Ebermayer’s (1876) classic work on 
the production and chemical composition of forest litter. This study 
demonstrated conclusively the importance of litter-fall in the nutrient 
cycle of the forest, at the same time that its significance in soil develop- 
ment was being shown by Miiller’s (1887) pioneer investigation of the 
types of forest humus layer. More recent studies of the importance of 
litter-fall in the forest ecosystem have been reviewed by Lutz and 
Chandler (1946). 
In the future, forest litter may assume additional significance. The 
current rapid increase in human population, with its consequent 
pressure on food supplies and accelerated depletion of non-renewable 
resources such as coal and oil, will eventually necessitate much fuller use 
of the world’s organic production (cf. Gaffron, 1946). To be thoroughly 
efficient such utilization must be mainly a t the level of green plants, 
the primary producers in the food web. It will also depend upon cheaper 
sources of energy and on great expansion of biochemical engineering, 
with current plant residues of all kinds serving as raw materials in 
addition to the present mainstays - agricultural crops, tree boles, and 
fossil plant deposits of coal and oil. Because much of the world’s land 
is best suited to the growth of trees, and wood will in any case remain 
a valuable raw material in its own right, forests will probably be a 
major source of materials for the new biochemical technology, par- 
ticularly since mature stands can in certain circumstances be managed 
economically on a sustaining basis by selective felling. Moreover, forests 
utilize both light and growing season to a much greater degree than 
most agricultGa1 crops, especially if the trees arel evergreen. Total 
yields of forest dry matter compare favorably with those of farm crops, 
even without the constant cultivation and fertilization the latter receive 
(Weck, 1955 ; Ovington and Pearsall, 1956; Ovington, 1956). 
If forest production is to be used with maximum efficiency, the leaves 
and other debris should be utilized along with boles and slash, since they 
make up an important part of the total yield (see Table XX, p. 148). 
One promising use of leaf litter is as a source of protein which could be 
extracted from the leaves and incorporated into palatable foodstuffs. 
Such protein is “not as good as milk protein, but is as good as, or even 
better than, fish meal” (Pirie, 1962). Pirie (1953, 1958, 1961) has pro- 
vided cogent arguments for attempting the extraction of protein from 
forest and agricultural waste on a commercial scale, and the cultivation 
of useful micro-organisms on the residue. The cultivation of edible 
fungi on beds of forest litter or on the forest floor itself (“fungal farm- 
ing”) is another use of litter which might add to the world food supply. 
LITTER PRODUCTION IN FORESTS O F THE WORLD 103 
The harvesting of present edible fungal growth is still inefficient and 
haphazard. Smith (1958) notes that conifer forests and plantations of 
Michigan, U.S.A., each year “burst with great quantities of relatively 
few species of Boletus”. He suggests that lumber companies could 
harvest the fungus crop as a means of paying taxes and other costs 
while the trees are growing to commercial size. 
Glesinger (1949), in a popular account entitled “The Coming Age of 
Wood”, points out that the cellulose in wood wastes is capable of being 
used not only as natural fibre, but as reconstituted cellulose in rayon 
and plastics, and as raw material for hydrolysis to sugar. The sugar can 
then be used to produce alcohol, high-protein yeast fodder, and a 
variety of other useful products. Presumably the cellulose in litter 
materials could also be so employed, though not as economically. It 
seems likely that the lignin in wood waste and litter, like the cellulose, 
can eventually become the raw material for a wide range of chemical 
conversions, whose industrial importance will increase greatly as 
reserves of coal and oil dwindle and demands for industrial raw materials 
grow. Brauns and Brauns (1960, pp. 742-9), in their book on lignin 
chemistry, point out that this substance is already used (though not 
on a large scale, in proportion to its availability) in the production of 
vanillin, plastics, ion-exchange resins, soil stabilizers, fertilizers, rubber 
reinforcing agents, tanning agents, stabilizers for asphalt emulsions, 
dispersants in oil-well drilling and other processes, and in ceramic 
processing. New and large-scale industrial uses will undoubtedly appear 
as the chemistry of lignin is further investigated. Other litter com- 
ponents beside cellulose and lignin may have industrial potential, the 
oils and resins in Gymnosperm litter being perhaps the most probable 
example. 
If litter is to be utilized commercially, harvest methods will need to 
be developed. Mechanized raking might serve in well-spaced plantations 
with closed canopy and little ground flora. In other types of forest some 
form of vacuum collection might be devised, since the litter material is 
loose and unattached. Should litter utilization become economic, it 
will inevitably involve replacement of the nutrient elements present in 
the organic debris harvested.Nitrogen is probably the most important 
of these, but phosphorus, potassium and calcium will also be significant 
(Tamm, 1958). In time, nitrogenous fertilizers may be synthesized from 
atmospheric nitrogen a t low cost, through the use of small nuclear 
reactors which could provide local sources of power in forested areas. 
The increasing use of human excretory wastes as fertilizers through 
sewage processing may also enable a low cost return of nitrogen, 
phosphorus, potassium and other nutrients to forested areas, especi- 
ally since the costly sterilization needed for the agricultural use of 
104 J. ROGER BRAY AND EVILLE GORHAM 
sewage will not be necessary in forest areas. Aerial application of 
various fertilizers may become a widespread technique for economic- 
ally renewing or improving the fertility of forest soils, as the demand 
for forest products rises. 
Even if forest litter does not become an economic raw material in 
the near future, the study of quantitative aspects of litter-fall remains 
an important part of forest ecology, dealing with a major pathway for 
both energy and nutrient transfer in this type of ecosystem. And since 
litter production is easy to measure in comparison with the difficult and 
expensive techniques for estimating total net production of forest 
stands, the possibility that litter-fall might serve as a simple and con- 
venient index to net production provided an additional stimulus for 
this review. The chief aim of the study, however, is to collate available 
data on the quantity of litter produced by forests in different parts of 
the world, -and to assess the influence of environment upon litter-fall 
under different forest communities. 
11. SOURCES OF DATA 
A. UNPUBLISXED STUDY B Y J . R. BRAY 
Litter production was measured by Bray from 1957 to 1961 in an 
Angiosperm forest with a slight admixture of Pinus strobus. This forest 
occurs on the upper slope of the east bank of the Don River valley at 
Glendon Hall, Toronto, Canada (43" 40' N, 79' 22' W). It is dominated 
by Acer saccharurn with a density of 247 treestha. The composition is 
shown in detail in Table I. 
In 1957 and 1958, leaves and stem fragments were collected from the 
forest floor in late autumn at the close of the period of leaf-fall. These 
collections were made from 1 f t 2 quadrats (30.5 x 30-5 cm) placed at 
equal intervals along a transect. Newly fallen leaves and any stem 
material included were lifted intact from the decomposed duff layer in 
each quadrat. Samples were taken to the laboratory, where each leaf 
was inspected for signs of decay. If a mesic, calcium-rich leaf (e.g. Acer 
saccharurn, Fraxinus pennsylvanica) showed only slight decay or tiny 
holes it was retained as representative of the current crop. If a leaf 
with a tough, leathery surface (e.g. Quercus boreaZiis, Q. alba) was even 
moderately decayed, it was rejected as belonging to the previous year's 
crop. On this basis it was possible to separate the leaves of the current 
season from those of the previous season in all but a few cases. Samples 
were then oven-dried at 105°C. 
In early winter of 1959, Hty galvanized iron litter pails (0.093m2 
in area) were placed in the forest in a regular block pattern. No pail was 
located beneath a shrub or low sapling which would intercept litter 
TABLE I 
Forest Composition, Glendon Hall, Toronto, Canada 
Density Basal area Frequency Density Basal area Importance 
at breast height index* 
(treeslha) (m2/tree) (m2/ha) (percentage of total) 
Acer saccharurn 247 0.044 11.0 42.4 42.5 20.8 106 
Pinus strobus 15 0.128 1.9 3.0 2-5 3.5 9 
Prunus serotina 44 0.115 5.1 6.1 7.5 9.5 23 
Quercus alba 87 0.181 15.7 18.2 15.0 29.9 63 
Quercus borealis 160 - 0.116 18.6 24.2 27.5 35.2 87 
Fraxinus pennsylvanica 29 0.017 0.5 6.1 5.0 0.9 12 
* Sum of frequency, density and basal area percentages. 
106 J . ROGER BRAY AND EVILLE GORHAM 
from the canopy. Each pail was wired to two adjacent steel posts to 
hold it level. The bottom of the pail was slightly above ground surface, 
and was perforated to allow for drainage of rain and snow melt. A 
copper screen was placed on the bottom of each pail to prevent tiny 
litter particles such as bud scales from washing through the drainage 
holes. Samples were taken at three or more irregular intervals during 
the year, the major collection being made at the close of leaf-fall. A few 
leaves blew into the pails in winter and early spring after the canopy 
opened and leaf-fall was complete. These leaves were discarded from 
the sample. All stem material in the pails was collected along with that 
portion of any fallen stem lying directly above the inside perimeter of a 
pail. All material of animal origin, including fecal matter, was rejected 
from the sample. Samples from 1960 and 1961 were oven-dried at 70". In 
1958 and 1961 leaf samples were ashed in a muffle furnace at around 
550°C for 24 h, to measure mineral content. 
Litter-fall and ash content are shown in Table 11. The similarity of 
leaf litter values indicates a rather uniform yearly production. Stem 
data are much more variable. 
TABLE I1 
Litter Production in Glendon Hall Forest, 
Toronto, Canada 
Litter fall (metric tons/ha/yr) 
1957 1958 1960 1961 Mean 
Leaf, incl. bud scales, fruit 2.8 3.2 3.2 3-1 3-1 
Stem, incl. bark 0.6 3.2 0.5 0.8 1.3 
Total 3.4 6.3 3.7 3.9 4.3 
(% drywt ) - 7.9 - 9.0 8.4 
Ash content of leaves 
B. WORLD REVIEW 
Literature containing data on litter-fall was reviewed in Biological 
Abstracts, Forestry Abstracts and miscellaneous journals. Coverage is 
undoubtedly incomplete owing to the wide range of journals and annual 
reports in which data of this kind are published. Biologists in areas for 
which data could not be found were consulted for literature references 
and for unpublished material. We are most grateful to many biologists 
throughout the world who answered our letters of inquiry. The following 
have very kindly supplied unpublished data or additional information 
about published data: Dr D. H. Ashton, Dr J. Brynaert, Dr H. R. De 
Selm, Mr A. Deville, Mr E. J. Dimock, Mr G. S. Meagher, Mr B. A. 
Mitchell, Dr J. S. Olson, Dr A. M. Schultz, Dr L. J. Webb, Drs F. D. 
Hole and G. A. Nielsen. 
LITTER PRODUCTION I N FORESTS O F THE WORLD 107 
We are especially indebted to the librarians in the reference room of 
the University of Toronto Library for their expert and unfailing 
bibliographic assistance. 
111. SELECTION AND PRESENTATION O F DATA 
A. CRITERIA FOR ACCEPTANCE 
Despite wide variation in methods of litter collection (e.g., raking of 
cleared surface, cloth or wire screen at soil surface, box or bucket with 
screen bottom above soil surface) and adequacy of sampling, most of 
the data examined have been included in this review, in order to obtain 
maximum coverage. Owing to the difficulty of equating number, area 
and type of litter traps, length of exposure, etc., studies of very unequal 
value have had to be given equal weight. In the case of Japanese 
forests (Ohmasa and Mori, 1937) the few data based on less than five 
plots were omitted. A study by Tarrant et ul. (1951) has been excluded 
because the data refer mainly to one year's growth of leaves or needles 
sampled from the lower portion of the crown (G. S. Meagher, private 
communication). All values based on complete or representative samp- 
ling of forest tree canopy have been segregated for separate examination 
of the yearly standing crop of tree foliage (see Table XIX). 
No attempt has been made to convert air-dry to oven-dry weights, 
partly because it has not always been possible to ascertain the method 
of drying, but also for other reasons. There appears to be considerable 
variation in weight loss upon further drying. Table I11 shows between 
7 and 18% lossin weight by air-dry litter after drying either at an 
elevated temperature or in vucuo. Ebermayer (1876) reported losses 
TABLE I11 
Loss of Weight by Air-dried Litter upon Further Drying 
Material % weight loss Drying method Authority 
Fagus sihatica litter 18 100" c Ebermayer, 1876 
Picea abies litter 15 looo c Ebermayer, 1876 
Pinus silvestris litter 14 100" c Ebermayer, 1876 
Fagus silvatica leaves 9.4 - Burger, 1925 
Picea abies needles 10.0 - Burger, 1925 
Picea abies needles 8.1 In vacuo, P,O, Lindberg and Norming, 1943 
Picea abies needles 6.8 I n vacuo, P,O, Lindberg and Norming, 1943 
Picea ubiecr needles 6.9 100-105" C, 5 h. Lindberg and Norming, 1943 
Populus leaves 7.8 I n vucuo, P,O, AnderssonandEnander, 1948 
Bet& litter 10.5 I n vacuo, 20" C Knudsen and 
Betub litter 10.8 10@-103° C, 2.6 h. Knudsen and 
Angiosperm tree litter 8.7 105' C Bray, unpublished 
Heath and moss litter 9.5 In vacuo, P,O, AndrB, 1947 
Mauritz-Hansson, 1939 
Mauritz-Hansson, 1939 
108 J . ROQER BRAY AND EVILLE QORHAM 
between 14 and 18%, all other losses ranged between 7 and 11%. The 
average for all data is lo%, whether or not each author's data are 
combined before averaging. Although air-dry litter may retain appreci- 
able amounts of water, the air-drying process may also result in con- 
siderable loss of organic matter. Tamm (1955) reported dry weight 
losses of 1 to 10% by living pine and spruce needles stored upon moist 
filter paper during 48 h at room temperature, only about 2% appeared 
to be lost by respiration. White (1954) observed that needles of Pinus 
resinosa air-dried for six weeks, and then oven-dried, yielded 9% less 
dry weight than needles oven-dried immediately at 7OoC. If the needles 
were left on whole branches during air-drying, the dry weight decline 
amounted to 14%. It thus appears that in some cases, oven-drying and 
air-drying of living leaves should give fairly comparable results, since 
the excess water content of air-dry needles may be balanced by their 
dry weight losses. Whether the same is true of litter remains to be 
ascertained. In any case, differences owing to drying techniques are 
small compared with variations in litter weight from other causes, and 
are unlikely to affect seriously any conclusions drawn from the material. 
B. ARRANGEMENT 
The collected records of litter-fall are presented in Table IV, as metric 
tons of leaves, other, and total litter per hectare per annum (1 metric 
ton/ha = 892 lb/acre). Owing to rounding off original figures, total litter 
does not always exactly equal the sum of leaf and other litter. 
An initial grouping of data is given under four major headings based 
on broad climatic zones : Equatorial, Warm Temperate, Cool Temperate 
and Arctic-Alpine. The Equatorial forests are all within a 10" band 
north and south of the Equator, in Colombia, the Congo, Ghana and 
Malaya. The Warm Temperate group ranges between about 30" and 40" 
both south and north of the Equator, including Australia, New Zealand, 
and southern parts of the U.S.A. (Florida, the Carolinas, Tennessee and 
California). The Cool Temperate forests in North America range from 
Missouri and the mountains of California to Minnesota and Quebec, 
or about latitude 37-47' N; and in Europe from Hungary to Finland, 
or about 47" to 62" N. Japanese forests are included in this group, for 
although the mean annual temperature is not greatly different from 
that of New Zealand, the climate is more extreme, with distinctly cool 
winters. The scanty Arctic-Alpine data come from stands at 3 000 m 
altitude in the Sierra Nevada of California, at 800m in southern 
Norway, and from the Kola Peninsula in the U.S.S.R., the last region 
being the most northerly at approximately latitude 67" N. 
Within the broad climatic zones, data are arranged alphabetically 
by country. For each country the presentation is alphabetically by 
TABLE IV 
Annual Production of Leaf, Other a.nd Total Litter by the Forests of the World 
Authority Date Location Lat. Long. Alt. Plant community Origin1 Age Drying Litter-fall 
(approx.) (m) (yr) methoda (metric tons/ba/yr 
Leaves Other T o L 
Jenny el al. 1949 Colombia 4s 
Bartholomew et at. 1953 Congo (Yangambi) 1N 
Brynaert p.c. (Ituri) 2N 
Laudelot and Meyer 1954 (Yangambi) 1N 
Nye 1961 Ghana (Kade) 6N 
Mitchell p.0. Malaya 3N 
Ashton 
Hatch 
Stoate 
p.c. Australia (Victoria) 37s 
1956 (Dwellingup) 33s 
1958 (Western) c 33s 
74w 
24E 
27E 
24E 
1w 
102E 
145E 
l l 6E 
c l l6E 
1700 
1800 
1650 
150 
c 600 
c 230 
c 300 
c 450 
270 
EQUATORIAL FORESTS 
Rain forest 
Forest 
Ewalyptus saligna 
Cupressus lwrilanica 
Mixed forest 
Musanga ceeropioides, young 
secondary forest 
Mawolobium forest 
Mixed forest 
Brachystegia forest 
Dioapyros spp., mature secondary 
Dipterocarpue forest, lowland 
Dipteromrpus forest lowland 
Dipterocarpua forest: upland un- 
forest 
disturbed 
Secondary forest, apparently never 
cultivated, moderately disturbed 
Secondary forest apparently never 
cultivated, moherately disturbed 
Secondary forest apparently never 
cultivated, mohefately disturbed 
Dipterocarpue baud%% plantation 
Druobahnops armnatica plantation 
Fagraea fragrane plantation 
Shoreu lepr08uh plantation (close 
Shorea Zep7osllla plantation (wide 
WARM TEMPERATE FORESTS 
planting) 
planting) 
I 
I 
E 
E 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
22 
25 
40 
28 
28 
25 
30 
30 
0 
8.3 
2.9 
8 5 
10.2 
1 2 3 
14.9 
15.3 
12.4 
12.3 
0 7.0 3.5 10.5 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
7.2 
5.5 
6.3 
8.3 
10.5 
14.4 
9.3 
10.9 
7.7 
14.8 
10.2 
(including subtropical) 
with undergrowth, 47 trees/ha 
217 trees/ha 
1013 trees/ha 
Eucalyptus regnans, mature forest I 200 4.2 3.9 8.1 
Eucalyptus regnaw, spar forest, I 55 4.1 3.9 8.1 
Eucalyptus regnaw, pole forest, I 25 3 4 3.3 6.9 
Eucalyptus marginata virgin forest I 0 1.2 1.1 2.4 
Eucalyptus marginata: pole forest I 36 0 2.0 1.1 3.1 
Eucalyptus mnrginata sapling forest I c 25 0 1.6 1.0 2.6 
Eucalyptue diversieoldr, virgin forest, I 2.8 2.9 6.7 
0.65 canopy 
I=indigenous, E=exotic. * O=oven dry, A=air dry. 
TABLE IV - continued 
Authority Date Location Lat. Long. Alt. Plant community Origin‘ Age Drying Litter-fall 
(approx.) (4 (yr) method* (metric tons/halyr) 
Leaves Other Total 
Webb P.C. (North N.S.W.) c 305 c 15OE 
Claudot 1956 Morocco (Rharb) 34N 7W 
Miller and Hurst 1957 New Zealand (Wellington) 415 175W 
Will 1959 (Rotorua) 385 176W 
Biawell and Schults p.c. U.S.A. (California) 
Blow 1955 (Tennessee) 
De Selm et al. p.c. (Tennessee) 
Heyward and 1936 (N. Florida) 
Barnette 
Kittredge 
Mete 
1940 
1952 
(California) 
(5. Carolina) 
39N 
36N 
36N 
30N 
38N 
35N 
123W 
84W 
848 
83W 
122w 
82W 
915 
245 
Warm Temperate Forests-continued 
Eucalyptus diversieolw, regrowth, 
0.87 canopy. 
Subtropical rain forest, Brgy- 
rodendron Fieus 
Low suhtropkal rain forest emergent 
Eucalyptus acmenioides e‘tc. 
Warm temperate rain forest, Cera- 
topetalum, Schizotperia 
Warm temperate rain forest, Cera- 
topetalum, Schizomeriq 
Tall warm temperate rain forest with 
l’riatania eonferta 
Wet sclerophyll forest, Eucalyptus 
zrilularis 
Eucalyptus camaldulensia 
Nothofag? twncata 
Pinus radzata 
Pinus radiata 
P i nw nigra 
Pseudotsuga ~ z i e s i i 
Pseudotsuga menziesii 
L a k t decidua 
Pintu ponderosa, pure stand 
Mixed Quercue spp cut over a t 62 yr. 
Larger trees Q. ldccinea and 
9. velutina, 
Panus virgintuna secondary forest 
Secondary growth Quercue alba, 
Q. velulina Q. prinus 
Pinue palustha second growth, 
889 trees/ha 
Pinus palustns second growth, 
1161 trees/ha 
Pinus palustns second growth, 
1947 treeslha 
Pinus palustns second growth, 
2 402 treeslha 
Pinus caribaea second growth, 
1277 trees/ha. 
Pinus cananenas 
P inw taeda, P . eehinata 
Pinue echinata 
Pinus taeda 
Pinus eehinata and mixedangio- 
snerm8 
I 
I 
I 
I 
I 
I 
1 
I 
E 
E 
E 
P 
E 
E 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
0 
0 
0 
0 
0 
0 
0 
40 A 
28 A 
45 A 
40 A 
33 A 
45 A 
0 
78 0 
15 0 
0 
0 
0 
0 
0 
0 
0 
20-25 0 
30-40 0 
10 0 
1-60 0 
2.7 
7.2 
7.3 
4.5 
5.9 
6.8 
6.0 
4.2 
3.5 
4.2 
5.1 
1.5 
2.2 
2.2 
2.1 
3.8 
3.5 
2.7 
3.4 
2.7 
3.3 
3.9 
5.0 
3.3 
4.2 
3.8 
3.3 
1.5 
3.9 
2.0 
2.8 
1.4 
0.7 
1.5 
0.7 
1.0 
1.3 
1.3 
0.3 
1.6 
6.0 
6.0 
5.7 
7.4 
6.3 
7.9 
2.9 
2.9 
3.7 
24 
4 4 
4.6 
6.7 
6.3 
46 
4.6 
6 4 
~~ 
l I=indigenous, E =exotic. a 0 -oven dry, A=air dry. 
TABLE IV - continued 
Authority Date Location Lat. Long. Alt. Plant community Origin1 Age Drying Litter-fall 
(approx.) (m) (yr) method’ Leaves Other Total 
(metric tons/ha/n) 
Olson p.c. (Tennessee) 36N 84W 
Sims 1932 (N. Carolina) 
Biihmerle 1906 Austria 
Bray Table11 Canada (Toronto) 
Coldwell and 
De Long 
1950 (Montreal) 
Perina and Vintrova 1958 Czechoslovakia 
Bornehusch 1937 Denmark (Nsdebo) 
Boysen- Jensen 1930 (Sor0) 
Moller 1945 
Aaltonen (data of 1948 Finland (South) 
Svinhnfvud) 
36N 83W 
48N 16E 
44N 80W 120 
47N 74W 
c 49N c l 8E 
56N 12E 
56N 12E 
56N 12E 
c 62N c22E 
Warm Temperate Forest-onlinued 
Mixed angiosperms and Pinue 
eehinac 
Mixed angiosperms and Pinusspp. 
Mixedsnmosoermq 
Mixed a n ~ o s ~ e - 6 
Mixed angiospem 
Pinus eehinatu north-facing slope 
Pinu8cehinatu:south-facina slope 
Pinua eehina&level upland 
Liriodendron tulipifera Pqpulua, 
Frminzlsin sinkhold 
Querctls Carua Liriodendron 
Qwms , Carya, Liriodendron 
lulip$era,ndrth-facing slope 
lulipifera,south-f3cin~ slope 
Quercua Carya, Liriaddrmi 
B inwr - uercud forest,unburned 
Pinus - 8uercus forest,burned 
COOL T E ~ ERATE FORESTS 
Pinua niura plantation 
Pinus nigra plantation 
Acer saccharurn Quermsboralis 
Beer saccharuna 
Fagus grandifolia 
Betula populifolia 
Pwulus arandidenlata. P. trmuloidee 
.!uZip$era, level upland 
uercu.9, Carya, Liriodendron valley 
alba slight’admixtnre Pi& 
%obua’ 
Pi+& spl 
Piceaabie6,stem diam.6 cm., 
Picea abies, stem diam. 10 cm., 
P i c a abiee, stem diam.21 cm., 
Fraxanue excelsior. unthinned 
7 000/ha 
3 700/ha 
1200/ha 
Fraxinus excelsior,thinned 
Fagus silvatica 
PinUS 8dVestl.is 
Picea abiea 
I 1-60 
I 1-40 
I 1-150 
I 1-50 
I 1-45 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 37 
I 57 
I 60-200 
I 
I 
I 
I 
I 
I 
I 
I 12 
I 12 
I 5-200 
I 
I 
94 
0 4.3 1.7 6.0 
3.6 1.1 4.6 0 
0 46 0 7 53 
0 4.1 0.6 4.7 
4.1 0 9 6 1 0 
0 6.6 
0 6.2 
0 3.8 
0 4.7 
4.0 
5.0 
6.4 
6.3 
3.5 
2.0 
0 3.5 
0 3.8 
0 3.1 1.3 4.3 
0 3.4 
0 2.2 
0 1.7 
0 1.7 
A 2.2 1.6 1.4 3 4 
A 1.2 
A 1.6 
A 1.0 
*I=indigenous, E=exotic. O=oven dry, A=air dry. 
TABLE IV - continued 
Authoilty Date Location Lat. Long. Alt. Plant community Origin1 Age Drying Litter-fall 
(approx.) (m) (yr) methoda (metric tons/ha/yr) 
Leaves Other Total 
Cool Temperate Forests-continued 
Belula I A 1.9 
viro 1056 (Eva) 61N 25E 105 Pinussilvestris I 50 0 1.7 0.6 2.3 
Pinuasilve.at+ I 88 0 1.2 0.6 1.8 
(Vilppula) 62N 25E 105 Pinussilvestrzd I 58 0 2.7 
61N 25E 105 Piceaabies I 68 0 1.9 1.0 2.8 
Picea abies I 0 1.9 0.5 2.4 
(Hyytiala) 62N 24E 150 Pieeaabia I 78 0 1.7 0.4 2.2 
(Vesijako) 61N 25E 110 Betula I 91 0 1.3 0.5 1.8 
1.5 
(Eva) 
Betula I 86 0 
Danckelmann 1887a Germany (5. Bavaria) 48N 11E Pinus silvestris, plantations on good I 21-40 A 3.3 
Pinwr silvestri.8, plantations on good I 4140 A 3.2 
soils 
soils 
soils 
Pinus silvertris, plantatibns on good I 61-80 A 3.2 
Pinus silvestris, plantations on good I 81-100 A 3.1 
Pinus silvestri.8, plantations on good I 100 A 3.0 
Pinus silvestris,plantations on I 21-40 A 2.4 
Pinus silvestris, plantationson I 41-60 A 2.3 
Pinus silvest7i.8,plantations on I 61-80 A 2.2 
Pinus stluestrzd, plantations on I 81-100 A 2.0 
Pinus siZvestri8,plantations on I 100 A 1.9 
SOilS 
soils 
moderately good to poor soils 
moderately good to poor soils 
moderately good to poor SOUS 
moderately good to poorsoils 
moderately good to poor solls 
Fagus silvatiea, good to moderately I 21-40 A 3.6 
Fugwr silvatiea, good to moderately I 41-60 A 4.2 
Fagua silvutieu, good to moderately I 61-80 A 4.6 
Fagus silvdica, good to moderately I 81-100 A 5.0 
Fagus silvdim, good to moderately I 100 A 4.6 
Fagus silvatica, fair to poor soils I 4140 A 3.6 
Fagwr silvatica fair to poor oils I 61-80 A 3.9 
Picea at+ I 21-40 A 3.1 
Pieea a h 8 I 41-60 A 3.7 
good Soil8 
good soils 
good soils 
good soils 
good soils 
Fugw silvuth: fair to poor soils I 81-100 A 4.2 
Danckelmann 18871, (throughout) c 50N c 10E 
'I=indigenous, E=exotic. O=oven dry, A=air dry. 
TABLE IV - continued 
Litter-fall 
Leaves Other Total 
Origin' Age Drying Authority Date Location Lat. Long. Alt. Plant community 
(approx.) (m) (yr) methoda (metric tons/hs/gr) 
Ebermayer 1876 
Ebermayer (data of 1876 
Hartin) 
(Bavaria) c 49N c 12E 
Cool Temperate Forest&-continued 
Picea abies 
Pieea dies 
Picea abies 
Fagus silvatica 
Fagua &vat+ 
Fagus silvatwa 
P ica abies 
P i ca abiea 
Picea abies 
Picea abies 
Pinus si1veatri.a 
Pinus 6ilvestri.a 
Pinua eilvestris 
Faqua silvatica 
61-80 
81-100 
100 
30-60 
60-90 
90 
30 
30-60 
60-90 
90 
25-50 
50-75 
75-100 
80 
100 
A 
A 
A 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
A 
A 
3.8 
3.6 
3.4 
3.4 
3.4 
3.3 
4.5 
3.4 
2.9 
2.8 
2.9 
3.0 
3.6 
4.0 
3.8 
TABLE IV - continued 
Authority Date Location Lat. Long. Ale. Plant community 
(wwox.) (m) 
Origin' Age Drying Litter-fall 
(yr) method' (metric tons/ha/yr) 
Leaves Other Tow 
Ohmasa and Kori 
Witkamp and 
van der Drift 
Bonnevie-Svendsen 
and Qjem 
(Kunadacs) 
(Godollo) . 
(Era) 
(Kunadacs) 
(Retsag) 
(Godollo) 
(Ugod) 
(Rallol 
(Kunadacs) 
(Kallo) 
(Matra) 
(Kallo) 
(Kallo) 
(Godollo) 
(Retsag)' 
(Godollo) 
1937 Japan 
1961 Netherlands (Amhem) 
1967 Norway (Eidsberg) 
(Ringsaker) 
(Storelvdal) 
(Qrue) 
48N 22E 
48N 201 
c 36N c 136W 
62N 6E 
60N 11E 
61N 11E 
62N 11E 
6ON 12E 
6ON 11E 
69N 10E 
Cool Temperate Forests-continued 
Populus (Hungarian szurke) 
Populue nigra hybrid 
UZmw (Hungarian venic) 
Betula 
w c u e robur 
uercue robur 
WWU8 8Ee8aflo7U 
Chanzaecyparis obtuea 
Pinue denaiflora 
Pinus thunbergii 
Thujopsid dolabrata 
Lark kampferc (leptolepia) 
Abies eaclutlinensur 
Pieea glehnii 
Caetanea crenata 
PieeajEZO6nSd 
Betula latifolia 
Quercua robur, Betula vem(coda, mor 
.nil 
~ e i & cerruco~)a, &tletnur rob~r, etc., 
mull Boil 
160 brk Sibirieo on brown earth 
170 
330 
250 
80 
250 
150 
170 
50 
Lark silririca on brown earth 
La& sibirica on iron podzol 
Lark decidua on iron podzol 
La& l@ptol,e& on brown earth 
Pieea abies on iron podzol 
Pieea a h 8 on brown earth 
Picea abies on brown earth 
Pice0 abkd on brown earth (tram. to 
nnaroii 
I 
II 
I 
E 
E 
E 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
. I 
I 
E 
E 
E 
I 
E 
I 
I 
I 
I 
24 
35 
40 
30 
35 
45 
70 
83 
51 
60 
70 
75 
76 
28 
45 
12-16 
45 
36 
60 
90 
30 
80 
60 
30-40 
45-66 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
A 
0 
0 
0 
0 
0 
0 
0 
0 
0 
3.8 
1.8 
2.5 
3.6 
3.9 
2.0 
1.1 
1.6 
1.6 
1.9 
1.4 
2.3 
2.8 
1.6 
2.7 
2.6 
1.0 
1.6 
4.4 
4.0 
4.9 
3.6 
3.3 
3.8 
2.7 
3.4 
4.0 
44 
4.7 
4.6 
38 
4 1 
4.5 
6.0 
3.7 
4 1 
2.8 
2.8 
1.2 
2.1 
3.4 
2.0 
3.z 
2.0 
46 
r"-""., 
I =indigenous, E =exotic. 0 =oven dry, A =air dry. 
TABLE IV - continued 
Authority Date Location Lat. Long. Alt. Plant community Origin' Age Drying Litter-fall 
(yr) method' (metric tOns/ha/yr 
Leaves Other T o L 
(approx.) (m) 
York 
Anderason and 
Enauder 
budsen and 
Yauritz-Hanaaon 
Lindberg and 
Norming 
.Lindquist 
Sjors 
Ehwald (data of 
Liebundgut) 
Kendrlck 
Owen 
Wright 
Alway et al. 
Alway and Zon 
Anonymous 
Chandler 
(Storelvdal) 
(Brunlanes) 
1939 (Stockholm) 
1943 (Stockholm) 
1038 (Lurid) 
1964 (S.W. Dalama) 
1967 Switzerland (Zurich) 
1069 U.K. (Cheshire) 
1964 (N. Wales) 
1967 (Roxburghahire) 
1033 U.S.A. (Minnesota) 
1030 (hfinnesota) 
1960 (Missouri) 
1941 (New York) 
61N 
69N 
69N 
SON 
66N 
60N 
47N 
63N 
63N 
66N 
47N 
47N 
c 39N 
43N 
11E 
18E 
18E 
18E 
13E 
16E 
9E 
3 w 
4 w 
3 w 
96W 
92W 
c 92W 
77w 
7 R W 
330 
60 
80 
80 
180 
180 
Cool Temperate Forests-continued 
Pinus silvestrb on iron podzol 
Fagus silvatiea on brown earth 
Fagw siludiea on brown earth 
Pieea abiee 
Pieea ab-ia 
Bet& 
Populust remula, herb-rich, some 
Betula pubeacend and hybrids 
Pieea abiea 
Mixed angiosperms 
Betula pubeseens, open parkland 
(46% canopy) 
Fagus dlvdiea 
Fagus eilvdica 
Pinus silvegtris 
Picea suchensis 
Picea abiet?, light low thinning, 
460 trees/ha 
Pieea abies, medium thinning, 
237 treestha 
Picea abies, heavy thinning, 
67 trees/ha 
Pieea abiea, light crown thinning, 
152 trees/ha 
deer saecharum and Tilia ame&ann 
Pinus banksiana and P. resinosa 
Pinus resmnosa 
Pinus bankaiana 
Pinus resinosa and P. 8trobun 
Pinus banksiana 
Pinus echinata 
Acer saccharurn and some mixed 
angiosperms 
Tilia americana and some mixed 
(trans. to podzol) 
Betula and Cmylus 
aneiosDerms angiosperms 
Carya cordifomzts 
little Fagus grandifolio 
Tilia americana, Q y e w rubra, 
Acer saccharurn, QUErcuS rubra, R 
Pinus strobus 
Tilia-americana, Q y e w rubra, 
Acer saccharurn, QUErcuS rubra, R 
Pinus strobus 
Carya cordifomzts 
little Fagus grandifolio 
I 90-130 
I 80 
I 26 
I 39 
I 63 
I 62 
I 
I 
I 
I 
I 
I 60 
P 
E 30 
E ,46 
E 46 
E 46 
E 46 
I 60 
I 
I 
I 
I 
I 
I 
I 30-70 
I 30-70 
I 30-70 
I 30-70 
I c24 
0 
0 
0 
0 
0 
0 
0 
0 
0 
A 
A 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
2.5 
1.6 
1.3 
1 9 
1.6 
3.1 
2.8 
1.7 
4.1 
2.1 
2.2 
2.0 
2.2 
2.1 
2.0 
2.0 
3.3 
3.1 
2.9 
2.9 
3.1 
0.6 
0.3 
0.0 
0.1 
0.7 
2.0 
2.6 
3.1 
3.1 
1.0 
1.0 
1.7 
2.8 
1-7 
4 8 
5.7 
4.3 
3.7 
4.2 
3 8 
Chandler 1944 (New York) 42N ._.. 
I -indigenous, E =exotic. * 0 =oven dry, A =air dry. 
TABLE- IV - continued 
Authority Date Location Lat. Long. Alt. Plant community Origin1 Age Drying Litter-fall 
(yr) method* (metric tonslhaly~) (approx.) (m) 
Leaves Other Total 
Dimock 
Hole and Nieleen 
Jenny el al. 
Lnnt 
Scott 
Ehwald (data of 
Abramova) 
Ehwald (data of 
Bykova) 
Ehwald (data of 
Nesterov) 
Ehwald (data of 
Sacharov) 
44N 
42N 
42N 
44N 
44N 
44N 
44N 
1958 (Washington State) 47N 
p.c. (Wisconsin) 43N 
1949 (California) 37N 
1951 (Connecticut) 42N 
1955 (Connecticut) 42N 
1957 U.S.S.R. (Velikije Luki) 57N 
1957 (Voronezh) 62N 
Cool Temperate Forests--eontinued 
74w Pinus atrobus 
76W Pinua reainosa 
76W Picea abies 
74w Picea rubens 
74w Tauga canadensis 
74w Thuja oceidenlalis 
74w Abiea balsamea 
123W 330 Paeudotauga menziesii unthiuned 
300 Paeudotauga menzicsi( light thinning 
320 Pseudotsuga menzhii, medium 
310 Paeudotsuga menziesii, heavy 
89W 290 wcua alba Q. vdutina, 420 treespa 
thinning 
thinning 
l l9W 1200- 8 wrcua kedggii 
1 200- Pinusponderoaa 
1500 Wxed gymnosperms 
Pinus strobus 
Beer aaccharum, Qww rubra and 
Pinus strobua 
P ica abiea with Ozalis &a& 
1 800 
2 200 
73w Pinua resinoaa 
73w 
31E 
mixed angiosperms 
ground flora 
PGea abiea with Vmcini :um murtillw, 
grouud Eora 
391 Pinus advestria 
1967 (MOSCOW) 66N 38E Pinua silvurtria with Qww 
Pinus silvurtria with Beer 
Pinus silveatris with mixed spp. 
Pieeaabies withSambunwr under- 
story 
Pica a b h 
&is-idaea ground flora 
Pinus ailvurtris with Colylus under- 
at,nro 
1957 (Brjansk) 63N 34E Pinua ailveetris with Vaccinium 
I 65 0 
I c24 0 
E c24 0 
I 150 0 
I 150 0 
I 65 0 
I 25 0 
I 45 0 
I 46 0 
I 45 0 
I 45 0 
I 100-125 0 
I 60-100 0 
I is0 o 
I 50 0 
I 30-50 
I 
I 0 
I 0 
I A 
I A 
I 20 0 
I 40 0 
I 60 0 
I 80 0 
I 100 0 
I A 
I A 
I A 
I 45-68 A 
I A? 
I A 
I A 
2.9 
3.8 
3.9 
1.9 
1.5 
1.1 
4.6 1.5 6.2 
1.3 
2.1 
4 6 
4.0 
4.0 
2.1 
1.7 
4.6 
3 7 
2.5 
2.3 
1.9 
2.0 
1.3 
3.0 
3.6 
4.2 
8.2 
6.9 
2.7 0.6 3.2 
4.7 2.2 6.0 
I=iudigenous, E=exotic. * 0 =oven dry, A=air dry. 
TABLE I V - continued 
Authority Date Location Lat. Long. Alt. Plant community Origin1 Age Drying Litter-fall 
(approx.) (m) (yr) methoda (metric tons/ha/yr) 
Leave8 Other Total 
Ehwald (data of 
Smirnova) 
Ehwald (data of 
Zrazevskij and 
Krot) 
Remezov and 
Bykova 
Sonn 
Sviridova 
Mork 
Jenny et al. 
Levina 
0 
hi 
1957 (Velikije Luki) 
1957 (Kiev) 
1953 (Voronezh) 
1960 (Voronezh) 
(Derkul steppe) 
(unspecified) 
1960 (Voronezh) 
1942 Norway (Hirkjolen) 
1949 
1960 
U.S.A. (California) 
U.S.S.R. (Kola Peninsula) 
57N 
51N 
52" 
52N 
49N 
52N 
62N 
37N 
67N 
31E 
31E 
39E 
393 
40E 
39E 
10E 
119w 
37E 
800 
3 000 
Cool Teniyeralc Forcsls-- continued 
Picea abies with Vacciniuni mrrtiUu8 
and Ozal i s aceloselln groiind flora 
Picea ubies with Relula sp. 
P i c a abks with mixed angiosperms 
Pinus siluestris 
Populus tremula, with Cowlus and 
Populus tremula with Cmylu8, Tilia 
some ground flora 
and much modnd flora 
Populu~ hemka-w ith TiEia Acer 
Pinus siluestris with Quercwr 
Pinus siluestris with Acer 
Pinus siluestris with Vaecinium 
sitis-idma eronnd flora 
platunoides add much grdund flora 
-- - -~~ ~~ - . . . . 
Quercus plantation 
Quercus and Frazinus plantation 
Quercus, Fraxinus and Caragann 
lnicrophylla 
Quercus and deer 
Quercus with Begopodiumground flora 
Quernur with Aegopodium and Carex 
ground flora 
Qu.ercu.8, solonetz soil 
Populus, density 0.75,1688 trees/ha 
(thinned) 
Pomlus densitv 1.0. 2 460 treeslha 
" I 
(thinned) 
(thinnkd) 
Populus density 0.8, 988 trees/ha 
Populus, density 1.1,1464 trees/ha 
ALPINE AND ARCTIC FORESTS 
Picea abies, very slight Betula 
admixture 
Pinue siluestri-9, appreciable Belula 
admixture 
Betula 
Pinus conlorta 
Pinue siluestris with Cladoniaground 
flora 
Pinwr silveetri.8 with H~loconzium 
I 70 
I 38-90 
I 
I 10,45,105 
I 10 
I 25 
I 50 
I 
I 
I 30 
25 
60 
15 
50 
c 210 
130 
c 170 
30 
30 
55 
55 
I el35 
I c200 
I c 105 
I 200 
I 
I 
A 3.3 1.6 4.9 
0 1.5 0.5 2.0 
0 2.1 0.6 2.7 
0 2.4 
0 
0 
0 
3.9 
4.1 
4.9 
1.3 
2.0 
4.5 
3.3 
3.1 
4.3 
5.2 
4.1 
4.1 
1.4 
A 6.0 
A 5.2 
A 
A 
5.4 
4.6 
0 0.9 0.6 1.5 
0 0.5 0.3 0.8 
0 0.6 0.2 0.8 
0 1.2 
0.6 
1.0 
ground flora 
I =indigenous, E =exotic. * 0 =oven dry, A =air dry. La 
118 J. ROGER BRAY AND EVILLE GORHAM 
author, which involves some separation of data from the same areas 
within the U.S.A. and the U.S.S.R. 
IV. LITTER COMPONENTS 
A. DETAILED LITTER SEPARATION 
Table V shows that leaf material contributed 60-76y0 of litter for 
the species listed, branches 12-15%, bark <1-14y0 and fruit <1-17%. 
Trees with loose dehiscent bark produced considerably more bark litter 
TABLE V 
Detailed separation of Litter Cmponents 
Percentage of total litter 
Leaf Fruit Branch Bark Other* Authority 
Pinua 
Pinua 
Pinua 
Picea 
Picea- Betulu 
Betula 
Quercua 
Eucalyptua 
60 11 12 14 <1 Perina and Vintrova, 1958 
62 17 1-21-+] Mork, 1942 
69 2 12 11 6 Viro, 1955 
73 5 13 - 10 Viro, 1955 
76 6 k-,l8-----+I Mork, 1942 
71 - 12 <1 16 Viro, 1955 
75 t l 15 9 - Nieleen and Hole, p.c. 
60 15t ) - 2 b + ] Hatch. 1955 
* Flowers, bud scales, fragments, epiphytes, insects. 
t Including buds. 
than did tight-barked trees. For example, the floor of a Eucalyptus 
forest was often covered with fallen bark; and Pinw forests, particu- 
larly of P. resinosa, also showed a high bark-fall. Bark litter from 
Pagw, Carpinw and other tight-barked trees was negligible. The 
variation of fruit litter reflects the widely varying fruit size and pro- 
duction of tree species and the usually short period over which litter is 
sampled. Curtis (1959) found that an Acer saccharurn forest produced 
from 99 000 seeds/ha/yr to 13 million seeds/ha/yr. Miller and Hurst 
(1957) noted great annual variation in seed production by a pure 
Nothofagus truncata forest, and observed that hot dry summers favored 
flowering. The occurrence of “mast years” in true beech (B’agw) forests 
is well known. 
B. PERCENTAGE O F NON-LEAF LITTER 
The difficulties of sampling tree stem litter have been noted fre- 
quently. Nye (1961) observed that timber-fall over a small area was 
very erratic and difficult to measure, since it was influenced greatly 
by the fall of even a single large tree. Data from Toronto (Table 11) 
LITTER PRODUCTION IN FORESTS OF THE WORLD 119 
showed stem litter ranging from 14 to 50% of total yearly litter over 
four years. Non-leaf litter data in Table IV range from 2.8% in an 
angiosperm stand of Bonnevie and Gjems (1957) to 55% in an Angio- 
sperm forest of Stoate (1958). These variations emphasize that stem 
litter sampling requires larger areas and longer time spans than leaf 
litter sampling if accurate comparisons of the two are to be made. * 
On average, non-leaf litter makes up about 27 to 31% of the total, 
as shown by Table VI. The mean of all values is 30%. Values for Angio- 
TABLE VI 
Percentage of Non-leaf Material in Forest Litter 
Individual BY 
values author 
All species 30 30 
Angiosperms 30 31 
Gymnosperms 29 27 
sperms are slightly higher than those for Gymnosperms, owing mainly 
to high values for several Australian Warm Temperate species. If the 
data are divided into latitudinal zones (Table VII), Warm Temperate 
TABLE VII 
Percentage of Non-leaf Litter in Different Climates* 
Climate Gymnosperms Angiosperms 
(33) Tropical - 
New Zealand (39) 42 
Warm Temperate. North America 37 23 
Cool Temperate 23 21 
Arctic-Alpine (39) 21 
Warm Temperate, Australia and 
~~ 
*Figures in brackets represent a single author’s data. 
areas tend to have a higher non-leaf litter percentage than Cool Tem- 
perate areas. This relationship is especially evident in the Gymnosperm 
species. Among Angiosperms this tendency is less clear, for while the 
Warm Temperate forests of Australia include many loose-barked trees 
(e.g. Eucalyptus), the forests of the southern U.S.A. show lower non- 
leaf litter percentages similar to those of their Cool Temperate counter- 
parts farther north. 
c. UNDERSTORY LITTER 
The contribution of understory plants to forest litter is closely related 
to the density of the forest canopy and light penetration to the under- 
TABLE VI I I 
Understory Litter 
Species Understory litter Authority 
tonslhalyr) litter) 
(metric (yo of total 
Eucalyptus regnans mature forest, 47 treeslha 2*0* 25 Ashton (P.c.) 
Eucalyptus regnans spar forest, 217 treeslha 0.9* 11 Ashton (P.c.) 
Eucalyptus regnans pole forest, 1013 trees/ha 0.8* 11 Ashton (P.c.) 
Robinia pseudacacia, 9 yr 1.1.t 28 Auten, 1941 
Sassafras albidum, 12 yr 0.21- 7 Auten, 1941 
Larix leptolepis 0.3 10 Bonnevie-Svendsen and Gjems, 1957 
Larix sibirica 0.2 7 Bonnevie-Svendsen and Gjems, 1957 
Picea abies 0.1 3 Bonnevie-Svendsen and Gjems, 1957 
Pinus silvestris 0.2 7 Bonnevie-Svendsen and Gjems, 1957 
Ulmus glabra and mixed Angiosperms 0.3 10 Lindquist, 1938 
Pinus strobus 0.3 16 Scott, 1955 
Acer sacchrum 0.3 15 Scott, 1955 
Populus tremula, 30 yr, 2 460 treeslha 0.4 8 Sviridova, 1960 
Populus tremula, 30 yr, 1 688 treeslha 0.5f 10 Sviridova, 1960 
Populus tremula, 55 yr, 1464 treeslha 0.3 8 Sviridova, 1960 
Populus trernula, 55 yr. 988 trees/ha 0.35 6 Sviridova, 1960 
Quercus robur 0- 1 4 Witkamp and van der Drift, 1961 
Mixed Angiosperms, cut in 1940 0.8 20 Witkamp and van der Drift, 1961 
* Probably includea lower story trees. 
t Living material harvested in mid-summer. 
f Improvement cut 1952, sampled 195S58. 
8 Improvement cut 1940-42, sampled 1955-58. 
LITTER PRODUCTION I N FORESTS OF THE WORLD 121 
story. Data in Table VIII reveal that the maximum contribution of 
understory plants to total litter is 28% in a very young stand of 
Robinia, while an old open stand of Eucalyptus reaches 25%. Another 
high value of 20% is exhibited by a mixed Angiosperm stand (height 
6.5-10.5 m) opened by cutting. Other values range from 3 to IS%, and 
average 9%. 
D. MINERAL MATERIAL 
Forest litter is not wholly organic, but always contains some mineral 
matter. Table I X provides average values for the ash content of litter 
from Angiosperm and Gymnosperm species in North America and 
Fennoscandia. In both regions, the Angiosperm group, and especially 
the non-fagaceous Angiosperms, contained more mineral material than 
the Gymnosperm group ; with the majority of Gymnosperms having 
from 2 to 6% ash, the majority of Fagaceae from 4 to 8% ash and the 
majority of non-fagaceous Angiosperms from 8 to 14% ash content. 
Mean ash content as a percentage of dry matter of the nineteen 
Gymnosperm species was 3-7%, of the thirteen species of Fagaceae 
6.3%, and of the forty-three non-fagaceous Angiosperms 10.4%. Among 
genera summarized in Table IX with two or more species, mean per 
cent ash contents are as follows : Gymnosperms, Pinus, 3.0; Picea, 4.5 ; 
Juniperus, 4.6 ; Larix, 5.2 ; Fagaceae, Castanea, 4.4; Quercus, 6.6; F q u s , 
6-9 ; non-fagaceous Angiosperms, Acacia, 4.8 ; Populus, 5.5 ; Betula, 
5.8; Prunus, 7-7; Acer, 8.4; Diospyros, 9.0; Fraxinus, 10.7; Aesculus, 
14.7; Ulmus, 16.1; Morus, 16.3; Celtis, 21-4. Broadfoot and Pierre 
(1939) present ash contents of leaf litter from trees in West Virginia, 
U.S.A., indicating a range of from 2 to 3% dry weight for three Pinus 
species (P. strobus, P . rigida, and P. virginiana). Juniperus virginiana 
had 5% ash. Leaf litter from fifteen Angiosperm tree species ranged 
from 3 to 12% ash. 
It is noteworthythat ash content is usually low for taxa in Table IX 
such as Acacia, Betulu, Castanea, Juniperus, Pinus, Populw, and 
Quercus, which are usually pioneer in forest development and which often 
occur on the more infertile sites. There is a higher ash content in taxa 
such as Acer saccharurn, Aesculus, .Celtis, Cladrastis lutea, Diospyros, 
Praxinus, Juglans nigra, Liriodendron tulipifera, Magnolia macro- 
phytla, Morus, Tilia americana and Ulmus, which usually occur in the 
more developed (or “climax”) forest communities and on the more 
mesic and fertile soils. Ash content of litter may vary with region, 
owing mainly to soil differences. For example, among the Fenno- 
scandian data, those from Finland tend to be rather low. 
Detailed analyses of the major elements comprising the mineral 
material in litter are numerous, and have been reviewed extensively 
TABLE I X 
Ash. Content of Litter from Various Trees 
~ ~ ~~~~~~~~ 
North America Fennoscandia* Frequency 
Ash yo Scott, 1955 Joffe, 1949 *Various authors Gymno- Fagaceae Non-fagaceous 
of dry (freshly fallen leaves or (old leaves) sperms Angiosperms 
weight foliage) 
- 1 
Pinus rigida 2 0 0 
Pinus silvestris 
2 
Pinus rigida Pinus reainosa 
Pinus strobus 
Pinus silveatris 4 0 0 
Abies balsamea 
Picea rubens Larix leptolepia 
Populus grandidentata 
Pinus banksiana 
Pinus cari baea 
Pinw, palustris 
Quercus borealis 
6 1 1 
4 
Acacia angustissima 
Caatanea sativa Betula popal~olia 
Juniperus utahensia Castanea vulgaris 
Pinus resinosa 
Juniperus pinchotii Acer rubrum 3 2 3 
" 
Acacia roemeriana 
Acer rubrum 
Pinus strobus 
Quercus alba 
Quercus breviloba 
Quercus palustris 
Betula pabeacens and 
vermosa 
Larix sibirica 
P i c a abies 
Sorbua aucuparia 3 3 4 
* Andersson and Enander, 1948. Bonnevie-Svendsen and Gjems, 1957. Hesselman, 1925. Knudsen and Mauritz-Hansson, 1939. 
Mork, 1942. Viro, 1955. 
TABLE IX - continued 
North America Fennoscandia* Frequency 
Ash yo Scott, 1955 Joffe, 1949 *Various authors Gymno- Fagaceae Non-fagaceom 
weight foliage) 
of dry (freshly fallen leaves or (old leaves) sperms Angiosperms 
6- 
Fagua grandqolia 
Quercus virginiana 
L a r k decidwz 
Fagua silvatica 1 3 0 
sndifolia Populus tremzclcl 
mnsylvanica Quercus robur 0 3 4 
8 
Diospyros virginiana 
Fraxinus excelsior 
Fraxinus quadrangulata Acer smcharum 0 0 6 
Liquidambar styraci$ua 
Prunus serotim 
Carya ovata 
Catalpa speciosa 
CornusJorida 
Diospyros texana 
Magnolia macrophylla 
Platanus occidentalis 
Liriodendron tulipij'era 
Tilia americam 
9 
0 0 6 
10 
Quercus douglaaii Fraxinua americana 0 1 3 
Ulmus americana Robinia pseudmacia Acer platanoides 0 0 3 
11 
* Andersson and Enander, 1948. Bonnevie-Svendsen and Gjems, 1957. Hesselman, 1925. Knudsen and Mauritz-Hansson, 1939. 
Mork, 1942. Viro, 1955. 
TABLE IX - continued 
North America Fennoscandia* Freauencv 
Ash % Scott, 1955 Joffe, 1949 *Various authors Gymno- Fagaceae Non-fagacsoua 
of dry (freshly fallen leaves or (old leaves) sperms Angiosperms 
weight foliage) 
-- 
Acer saccharurn 0 0 1 
13 
0 0 2 Cladrastis lutea 
Juglans nigra 
Aesculus glabra 
Robinia pseudacack 0 0 2 
Aesculus calijornica 
Celtis reticulata Fraxinus excelsior 0 0 3 
16 
0 0 2 
Morus microphylla 
Morus rubra 
-. 
Celtis occidentalis 26.0 Ulmus scabra 21.3 0 0 2 
* AnderssonandEnander, 1948. Bonnevie-Svendsenctnd Gjems, 1957. Hewelman, 1925. KnudeenandMaurita-Hamson, 1939. 
Mork, 1942. Viro, 1955. 
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, cold- 
water 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%. “Lignin- 
humus”, 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 Angio- 
sperms 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, cold- 
water soluble 6-25, hot-water soluble P 1 0 , alcohol soluble 2-5, hemi- 
celluloses 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 amino- 
acids, 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 Angio- 
sperm forests to occupy more fertile sites. As far as litter-fall is con- 
cerned, Table X indicates that when a wide range of sites is considered 
I2 C.E.R. 
126 J . ROGER BRAY AND EVILLE QORHAM 
TABLE X 
A Comparison of Litter Production by Evergreen and Deciduous Trees 
in the Northern Hemisphere 
No. regions Evergreen Deciduous 
averaged Gymnosperms Angiosperms 
(metric tons/he/yr) 
Total litter 8 3.7 3.2 
Leaf litter 9 2.6 2.4 
by difference 
Other litter observed 
- 
4 
1.1 
0.7 
0.8 
0.7 
Gymnosperms yield about one-sixth more total litter annually than 
Angiosperms, the difference amounting to 0-5 t/ha. The difference for 
leaf litter alone is 8% (0.2 t/ha), and for those stands where other litter 
was actually collected the Gymnosperm yield was about the same as 
that of Angiosperm trees, 0.7 t/ha. (In computing averages from com- 
bined data, only those countries or states were considered for which both 
evergreen Gymnosperm and deciduous Angiosperm stand data were 
available. The averages in Table X, and in Table XI, are based on com- 
bined data for each country, with each American or Australian state, 
TABLE XI 
Annual Litter Production in Four Major Climatic Zones 
Leaves Other Total 
no. regions metric no. regions metric no. regions metric 
averaged tons/ha averaged tons/ha averaged tons/ha 
Arctic- Alpine 1 0.7 1 0.4 3 1.0 
Cool Temperate 15 2.5 10 0.9 22 3.5 
Warm Temperate 8 3.6 5 1.9 7 5.5 
Equatorial 2 6.8 1 3.5 4 10.9 
and the Werent major areas of the U.S.S.R., treated as countries, 
except for the following which are grouped - the New England states, 
the Carolinas.) 
Data on net production (Table XX) support the generalization that 
Gymnosperm trees are somewhatmore productive than Angiosperm 
trees, the difference amounting to about one-quarter (2.6 t/ha) for total 
above- and below-ground production. For leaves the difference is slight 
(see also data on standing crops of leaves in Table XIX). 
Specific areas do not always follow the above tendency. For example, 
within Germany the averages of data in Table I V show somewhat 
LITTER 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 bio- 
logical standpoint the length of the period when temperatures are 
above freezing is also important. It is of course year-long in the Equa- 
torial 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 Fenno- 
scandia 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 con- 
t In 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). 
128 J . ROGER BRAY AND EVILLE QORHAM 
nection it should be borne in mind that the three categories of litter 
summarized in Table XI do not represent matched sets of data, for 
some authors collected only leaf litter, and some of those collecting 
total litter did not separate leaf and other litter.) Leaf litter ranges 
from 0.7 tjha in Alpine Norwegian forest to nearly 7 t/ha in Equatorial 
Africa, with the Cool and Warm Temperate zones intermediate a t 2.5 
and 3.6 tjha respectively. Data for non-leaf litter are least satisfactory, 
with less coverage and also less reliability because of the irregular and 
' 4 t 
NORTH OR SOUTH LATITUDE (degrees1 
FIG. 1. Annual production of total litter in relation to latitude. Open triangles - 
equatorial, solid triangles - warm temperate, circles - cool temperate North American 
(open) and European (closed), squares - Arctic-Alpine. Line fitted visually to means for 
climatic zones, shown by large crosses. One alpine Californian stand is excluded. 
occasional deposition of large branches upon collecting sites. However, 
even in this instance the annual production in the Norwegian mountains 
is about one-ninth that in Ghana, 0.4 as against 3.5 tjha. Again the Cool 
and Warm Temperate forests are intermediate, with 0.9 and 1.9 t/ha. 
The major role of temperature in controlling litter production is 
well illustrated in Fig. 1, where total annual litter-fall is plotted versus 
latitude. The relationship is inverse and linear, with a maximum level 
of over 11 t/ha at the Equator declining steadily to a little less than 
1 t/ha a t latitude 65" N in Europe, where forest grades into tundra. 
Fig. 1 reveals that litter production in central and north European 
forests is about the same as that of similar Cool Temperate forests in 
LITTER PRODUCTION I N FORESTS OF THE WORLD 129 
the northern U.S.A. and Canada, although the European sites are on 
average about 10 degrees farther north. The warming effect of the 
Gulf Stream upon European climate is probably the major factor 
involved, but it is also possible that the intensive management of 
European as compared with North American forests is important in 
this connection. 
2. Altitude and Exposure 
Ebermayer’s (1876) data for Fagus silvatica, Picea abies snd Pinus 
silvestris have been summarized by 200 m altitude classes from 250 to 
1 250 m. This analysis, in Table XII, indicates a peak litter production 
at the intermediate elevations from 450 to 850 m, although no species 
covers the entire altitudinal gradient. The data for Picea are most 
complete, and show peak litter-fall between 650 and 850 m. There is a 
tendency in mountainous areas for rainfall and temperature conditions 
to be optimum for forest growth at intermediate elevations. At higher 
elevations, temperatures are too low and winds too severe for luxuriant 
tree growth, and at low elevations, there is often a decreased rainfall. 
Whether these conditions apply to the data in Table XI1 is not known. 
TABLE XI1 
Litter Production and Elevation in German Porests 
Elevation Fagua ailvatica Picea abies Pinw, silvestris 
(4 (total litter, metric tons/ha/yr) 
250 
3.8 - 3.3 
4.1 3.4 6.0t 
5.9* 3.9 
650 
- 3.6 
- 3.1t 
1050 
1250 
* One value. t Two values. 
Ebermayer’s material was also divided into four exposure quadrants, 
NE, SE, SW and NW. Values from cardinal points (N, E, S, W) were 
divided in half and assigned to each of the adjacent quadrants. The 
results of this analysis are given in Table XIII, and indicate a lower 
litter production in westerly than in easterly quadrants. The highest 
average litter production was on the NE slope, generally considered to 
be least exposed to the heating and drying effects of insolation ; while 
130 J. ROGER BRAY AND EVILLE GOREAM 
TABLE XI11 
Litter Production and Exposure in German Forests* 
Exposure Total litter production, metric tonslhalyr Total no. 
Fagus Picea Pinus Mean Mean 
silvatica abies silvestris weighted 
by no. of 
stands 
stands 
NE 4.1 4.7 4.0 4.3 4.3 14.5 
SE 4.4 3.7 3.7 3.9 3.8 10.0 
SW 3.9 2.5 3.8 3.4 3.2 15.0 
Nw 4.1 3.6 3.6 3.8 3.7 23.5 
* From data in Ebermayer f1876). 
the lowest average litter production occurred on the most exposed (SW) 
slope. The greater average exposure effect of SW as compared with SE 
slopes is presumably owing to maximum reception of insolation on SW 
slopes in the afternoon, when the air is warmest, driest, and usually 
clearest. Thus insolation and evaporation maxima tend to be greatest 
on SW slopes. 
3. Soil Fertility 
The influence of site class on litter production,with special reference 
to soil fertility, is shown in Table XIV. Site class designations are the 
European “bonitat” grades of decreasing fertility from I to V. Table XIV 
generally shows decreasing litter-fall with a decline in site quality, 
TABLE XIV 
Litter Production and Soil Fertility in German Forests 
Species Authority Site class Total litter 
(metric tonslhalyr) 
Pinus szhestris Zimmerle, 1933* I 3.0 
Danckelmann, 1887a 1-111 3.2 
Wiedemann, 1948* I11 2.0 
Danckelmann, 1887a m-v 2.2 
Wiedemann, 1948* V 1.0 
Piceu abies Zimmerle, 1949* I 3-8 
Wiedemann, 1936* I11 3.0 . 
Fagus silvatica Dietrich, 1925* I 3.5 
Danckelmann, 1887b 1-111 4.4 
Wiedemann, 1931* I11 2.5 
Danckelmann, 188713 111-V 3-9 
~~ ~~ 
* Cited by EhwaId (1957). 
LITTER PRODUCTION IN FORESTS OF THE WORLD 131 
although for Pagus silvatica the data fiom nineteenth- and twentieth- 
century authors require separate consideration. The data for Pinus 
silvestris provide the clearest indication of a site effect, with litter pro- 
duction on the poorest site (V) one-third that on the best site (I). The 
intermediate site class (111) produces two-thirds as much littgr as the 
best class. 
Data of Bonnevie-Svendsen and Gjems (1957) also indicate higher 
litter-fall on more fertile soils in Norway. Mean litter production for 
Larix spp. is 1-6 t/ha on iron-podzol and 2.8 t/ha on transitional and 
brown-earth soils. For Picea abies the corresponding figures are 2.0 t/ha 
and 3.2 t/ha respectively. 
4. Soil moisture 
Litter data from Ebermayer (1876) for Pinus silvestris and Picea 
abies are shown in Table XV from mesic and dry soil moisture sites. 
TABLE XV 
Litter Production and Soil Moisture in German Forests* 
Species Soil No. of Total litter 
moisture sites (metric tons/ha/yr) 
Pin- silvestris Mesic 6 4.0 
Picea abies Mesic 31 3.8 
Picea abies Dry 2 2.3 
Pinw silvestris Dry 11 3.5 
* From data in Ebermayer (1876). 
The decrease in litter-fall from mesic to dry conditions is especially 
marked for Picea, a mesic species, and less noticeable for Pinus, which 
tends to occur more often on exposed dry sites. 
c. TREATMENT 
1. Plantations and Native Forests 
Only one study (Ohmasa and Mori, 1937) gives sufficient data to 
allow comparisons of litter-fall in natural forest stands and plantations. 
In both Chamaecyparis obtusa and Pinus densijiora there is no significant 
difference between mean litter-fall in plantaJion and forest. Investiga- 
tion by Mitchell (private communication) of a variety of indigenous 
Malayan species yields a mean value of 8-7 t/ha for natural communities 
and 10.6 tiha for plantations, not necessarily of the same species. 
2. Influence of Tree Density and Basal Area 
Within closed-canopy forests litter production appears to be little 
affected by differences in tree density, as shown in Table XVI. Com- 
132 J . ROGER BRAY AND EVILLE GORRAM 
TABLE XVI 
Litter Production and Tree Density 
Species Authority Density Litter 
(treeslha), (metric tons/ 
h a m ) 
Fagw silvatica Moller, 1945 179 2.8 
233 2.3 
244 2.3 
248 2.6 
281 2.7 
317 2.5 
901 2.9 
908 2.8 
1173 2.6 
5 842 2.2 
6 732 3.0 
Populus trernula Sviridova, 1960 988 5.0 
1464 4.2 
1688 5.4 
2 460 4.9 
1161 3.4 
1 947 2.7 
2 402 3.3 
Pinus ponderosa Biswell and Schultz (P.c.) 1196 2.6 
1495 2.0 
2 931 1.8 
3 459 2.1 
Pinus paluatris Heyward and Barnette, 1936 889 2.7 
parison of eleven stands of Fugw silvatica (Moller, 1945) by a rank cor- 
relation test showed no significant correlation ( p > 0.10) between litter- 
fall and tree density. Similarly, studies by Sviridova (1960), Heyward 
and Barnette (1936) and Biswell and Schultz (Schultz, private com- 
munication) failed to show any consistent relationship between these 
two variables, although in each of these instances only four stands were 
compared. 
In Norway Bonnevie-Svendsen and Gjems (1957) have shown a 
distinct correlation between annual fall of leaf litter and stand basal 
area in a series of Gymnosperm and Angiosperm stands. Litter-fall 
averaged about 70-75 kg per m2 basal area, over a basal area range from 
8 to 40 m2/ha. In Missouri (U.S.A.), Crosby (1961) has demonstrated a 
correlation between total litter-fall of Pinus echinata and stand basal 
area, but in this case an increase from minimum to maximum basal area 
coverage of three-fold only doubled the annual litter-fall. The stands of 
low basal area had been thinned a few years prior to litter collection, and 
presumably the less productive trees were removed. 
LITTER PRODUCTION I N FORESTS O F THE WORLD 133 
3. Effect of Thinning 
If a closed-canopy forest is thinned there is a decrease in litter pro- 
duction which is roughly proportional to the degree of thinning. Data 
in Table IV demonstrate this relationship for Pseudotszqa menziesii 
(Dimock, 1958), Picea abies (Wright, 1957) and Fraxinus excelsior 
(Boysen-Jensen, 1930). In all cases the control stand has the highest 
litter-fall and the most heavily thinned stand the lowest. Moller (1945) 
has shown the effect of thinning upon the standing crop of Fagus sil- 
vatica leaves. With no thinning, leaf crop was 2.0 tiha, with Bregentved 
thinning 1.9 t/ha and with Vemmetofte thinning 1.7 t/ha. 
4.' Effect of Litter Removal 
Rights to utilize forest litter still existed in Germany in 1954, par- 
ticularly in Bavaria, where it sometimes caused extreme reduction of 
forest growth (Mayer-Krapoll, 1956). By comparing areas with and 
without rights to litter utilization, it has been estimated that annual 
forest output may require forty years to recover from long-continued 
litter removal. The loss of nitrogen in the litter is believed to be of 
especial significance in lessening forest productivity. Wiedemann ( 195 1) 
presented data from study plots (Hermeskeil143,146, Table 363, p. 260) 
indicating that twenty-five years of litter utilization reduced basal 
area increase by about two-thirds. Thirty years were then required for 
recovery. 
D. THE TIME FACTOR 
1. Seasonal Variation 
If forest litter is ever to be utilized economically, it will be of impor- 
tance to know the pattern of litter-fall, whether distinctly seasonal, or 
more or less continuous. Such knowledge is also of the utmost impor- 
tance to students of population dynamics in organisms responsible for 
litter breakdown, and may be of interest to persons concerned with the 
role of organic matter in soil development. 
The pattern of litter-fall varies greatly, as demonstrated by Figs. 2-5. 
In the Equatorial forests of Ghana, Colombia and Malaya litter-fall is 
continuous throughout the year, but with a tendency for slightly 
greater deposition during the first half of the year. In Ghana a, short dry 
season in January and February was noted as leading to increased leaf- 
fall (Nye, 1961). Laudelot and Meyer (1954) state that at Yangambi in 
the Congo there are two minima in the wet seasons and two maxima at 
the ends of the dry seasons. According to Deville (private communi- 
cation) seven-year plantation of Acacia decurrens showed highs in 
134 J. ROGER BRAY AND EVILLE GORHAM 
40 
20 
0 
2 40 
w 20 
k 
J O 
40 
20 
w o 
n. 
3 40 
-I 
-I 
!x 
I- 
2 
0 
n 
I 
0 
5 20 
= o 
40 
20 
0 
RAIN FOREST, COLOMBIA, TOTAL 
. . . 
RAIN FOREST, GHANA, TOTAL 
. . 
UNDISTURBED DIPTEROCARP FOREST, MALAYA, TOTAL 
. . . . . . . . . . . 
SECONDARY FOREST, MALAYA, TOTAL 
. . . . . . . . . . . 
SHOREA LEPROSULA [INDIGENOUS 1 PLANTATION, MALAYA 
1 / 
JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT.' NOV. OEC 
REP. 
( I ) 
40 
20 
0 
40 
20 
0 
40 
20 
0 
40 
20 
0 
40 
20 
0 
( 2.) 
(3) 
(3) 
(31 
FIG. 2. Seasonal litter-fallin equatorial forests. (1) Jenny et al., 1949;1(2) Nye, 1961; 
(3) Mitchell (P.c.). 
December (18% of total litter-fall) and June (llx), with lows in May 
(3%) and August to September (5% each). It should be noted that 
many individual species of indigenous tropical rain forest are distinctly 
deciduous, though not necessarily tied to any sort of annual cycle. The 
pattern and timing of leaf replacement is extremely variable, and 
dependent upon both external and internal factors (see Richards, 1957, 
In the Warm Temperate forests of eastern Australia, Fig. 3 shows that 
litter-fall goes on throughout the year, but with a distinct maximum in 
spring and early summer (October to December). Precipitation gener- 
ally increases along with temperature during this period in eastern 
Australia (Walter and Lieth, 1960). In the Eucalyptus regnans forests of 
Victoria, Australia, Ashton (private communication) reports about nine 
times as much leaf-fall in summer as in winter. In western Australia both 
young and old forests of Eucalyptus marginata deposit leaf litter mainly 
from January to March, the warm dry part of the year. Other litter falls 
irregularly throughout the year, but with slightly greater intensity at 
about the time of maximum leaf-fall (Hatch, 1955). Eucalyptus diversi- 
pp. 193-8). 
LITTER PRODUCTION I N FORESTS OF THE WORLD 136 
OTHER A LEAVES *A, 
... , 
'--- I- 
- 
-.-,#' 
40 
20 
0 
2 40 
-t 
-t 
a 
w 20 
I- 
5 0 
2 40 
a 
20 
I- 
W 
0 
: o 
3 
a 
40 
I 
I- 20 
z 
0 
E O 
40 
20 
0 
(4) 
- 20 
:AST AUSTRALIAN FORESTS, LEAVES 
SCLEROPHYLL 
0 
I I R G l N EUCALYPTUS MARGINATA, WEST AUSTRALIA 
OTHER 
P lNUS NIGRA, NEW Z E A L A N D 
LEAVES 
0 
40 
.___-_______- --- 
PlNUS RADIATA, NEW Z E A L A N D 
FIG. 3. Seasonal Litter-fd in forests of the southern hemkphere. (1) Webb (P.c.); (2) 
Hatch, 1956; (3)Miller andHurst, 1957; (4) Will, 1959. 
color in western Australia shows a similar pattern of litter deposition 
(Stoate, 1958). 
In New Zealand the peak leaf-fall of Nothofagus truncata is connected 
with the development of new leaves in the spring months of October 
and November (Miller and Hurst, 1957). The main fall of non-leaf litter 
takes place 2 months earlier. For the exotic northern Gymnosperms 
Pinus nigra, P. radiata and Larix decidua in New Zealand, maximum 
needle-fall occurs in autumn (March to May), according to Will (1959). 
While precipitation is rather uniform, March is the driest month of the 
year (9.4 mm) and June the wettest (14.5 mm). Pseudotsuga menziesii 
shows no definite seasonal trend. In all species the fall of non-needle 
litter is more affected by storms than is needle-fall, which does however 
show some storm influence. The main period of non-needle litter de- 
position is clearly mid-winter (June to July) for Pinus nigra, the peak 
coming about 2 months after cessation of needle-fall. The pattern is 
less regular for Pinus radiata, the average over 4 years showing one peak 
near the time of maximum needle-fall and another about 5 months later. 
The Warm Temperate forests of Tennessee in North America also 
136 
'ICEA ABlES 
SCOTLAND, DENMARK, 
TOTAL LEAVES 
--_ ---_ _.I---- -- ------__-- h 
'ICEA SITCHENSIS, WALES, LEAVES 
J. ROGER BRAY AND EVILLE QORRAM 
.40 
20 
~. ' 0 
.40 
( 6 ) 
40 
20 
0 
40 
20 
0 
40 
i 20 
4 LL 
0 
40 
20 
a 
u 
- 
-I 
W 
13 
z 
3 0 
40 
a 
Q 20 
- I 0 
40 
20 
0 
40 
2 0 , 
0 
40 
20 
0 
u 
* 
I 
0 
I 
rENNESSEE FORESTS, TOTAL 
UPLAND PINUS 
0 
FINNISH FORESTS, LEAVES 
( 3) 
YEAR 'OF 
4IGH L E A F F A L L 
YEAR OF 
LOW L E A F F A L L 
IAPANESE GYMNOSPERM FORESTS, LEAVES 
CRYPTOMERIA oOTUSA P l N l l S 
IENSIFLORA 
0 ... 
AN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC. 
FIG. 4. Seasonal litter-fall in forests of the northern hemisphere. (1) Witkamp and 
van der Drift, 1961; (2) Olson (P.c.); (3) Viro, 1955; (4) Kendrick, 1959 and Danckel- 
mann, 1887; (5) Mork, 1942; (6) Wright, 1957 and Bornebusch, 1937; (7) Owen, 1954; 
(8) Ohmasa and Mori, 1937. 
show a seasonal pattern, although some leaf-fall is observed throughout 
the year (Fig. 4). Angiosperms exhibit a distinct autumnal peak as the 
weather cools, while the seasonal effect is much less for Pinus echinata 
(Olsen, private communication). For Pinus echinata farther north in 
LITTER PRODUCTION IN FORESTS O F THE WORLD 137 
Missouri it is reported (Anon., 1960) that 60% of litter-fall occurs in 
the 3 months from September to November. 
In Cool Temperate forests seasonal patterns of litter-fall are often 
striking (Fig. 4), with autumnal cooling leading to more or less complete 
leaf-fall in deciduous species, as shown by the graphs for Dutch Quercus 
and mixed Angiosperms, and for Finnish. Betula. In New Hampshire 
(Anon., 1932) it is reported that four-fifths of the mixed Angiosperm 
litter-fall over the seven months June to December occurs in October. 
Among Gymnosperms the pattern of deposition ranges from distinctly 
seasonal, as in the various stands of Pinus silvestris represented in 
Fig. 4, to irregular throughout the year, as is the case with Picea abies 
in the stands shown. Chandler (1944) has noted however that Picea 
abies planted in the north-eastern U.S.A. shows distinctly lower needle- 
fall in spring and summer than at other times of year. In contrast 
irregular collections by Lindberg and Norming (1943) in Sweden showed 
high rates of needle-fall during late spring and early summer. Picea 
sitchensis in Wales showed a rather irregular pattern of needle-fall 
whether the total for the year was high (1946-47, with a very cold winter) 
or low (1947-48). There was however a slight tendency for spring and 
autumn maxima. Such a bimodal spring and autumn pattern of needle- 
fall was more strongly exhibited by Japanese stands of Cryptmeria 
japonica, Chumaecyparis obtusa and Pinus densijora. 
TABLE XVII 
Speci,fic Differences in Leaf Fall within an Upland Oak Porest in 
Tennessee, U.S.A. 
Leaf fall as per cent of total for 
each species 
Late Mid- Early 
August October December 
Overstory Quercw velutina 
Quercus coccinea 
Understory Cornus sp. 
Oxydendrum arboreum 
Nyssa sylvatica 
Quercw montana 
Quercus falcata 
Quercw stellata 
Aeer rubrum 
Carya sp. 
Pinw echinata 
Miscellaneous Quercw alba 
0 
1 
3 
1 
63 
0 
0 
0 
0 
0 
0 
0 
3 
12 
72 
99 
37 
16 
4 
43 
71 
32 
52 
20 
97 
87 
25 
0 
0 
7 4* 
96 
57 
29 
68 
48 
80 
~ ~ ~~~~ 
* Balance of 10% overwinters, 5 % falling by February and the remainder by April. 
138 J. ROGER BRAY AND EVILLE OORHAM 
The difference in leaf-fall periodicity of different species within mixed 
forest has been shown clearly by Blow (1955), working in upland oak 
forest of eastern Tennessee in the U.S.A. Table XVII shows the per- 
centage of leaf-fall during the year 1948-49 which was collected by 
late August, mid-October and early December. From this table it 
appears that the overstory species lose their leaves later than the under- 
story species, and that even within these groups there are distinct 
specific differences. The only species in this forest which retains many 
leaves (10%) through the winter is Quercus alba, although a few remain 
REF 
ANISOPTERA SHOREA . . I 
MALAYAN FOREST 
40 40 
u. 
LK 4 0 - 
W 
I- 
t 2 0 - 
MALAYAN FOREST, SHOREA L A E V I S 
- 40 
.20 
1 1 ) 
-3 
I 
+ 60 z 
0 * 40 
20 
0 
N E T H E R L A N D S FOREST QUERCUS 
T R E M U L A 
20 
J A N . FEB. MAR. APR. MAY JUNE JULY AUG. SEPT OCT. NOV. DEC. 
FIG. 5. Seasonal litter-fall of individual