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 appreciable amounts of water, the air-drying process may also result in considerable 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
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 appreciable amounts of water, the air-drying process may also result in considerable 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