NATIVE FOREST AND PLANTATIONS OF INTRODUCED TREES. 159 
the growth of native trees as given at p. 78 of the late Mr. Matthews’s 
book (‘‘ Tree-culture in New Zealand ’’), New Zealand diameter-growth 
is four times European and height-growth nearly twice, It must be 
noted that the comparison here made is between native New Zealand trees 
grown in the open and between European trees grown in a normal forest. 
Thus the greatest difference is in the diameter-growth. 
Judging from the height-growths, and the yearly rings of growth, one 
can say generally that the New Zealand native trees grow, as would be 
expected, faster than the forest trees of colder countries such as Europe 
and America. Since the forests of these countries are yielding returns, 
in money and employment, equal to dairying on poor soil in New Zealand, 
and are very carefully preserved and worked, it follows that New Zealand 
should do the same, unless all the civilized world (with England almost 
the sole exception) is in error over its forest policy. It must be remem- 
bered that Japan, after exhaustive inquiry and sending Commissions to 
the chief forest countries, adopted scientific forestry in toto. In Europe 
it is only some of the Balkan States that have a forest policv no better 
than New Zealand: and they are not losing forest ike New Zealand. 
PRODUCTION OF TIMBER PER ACRE PER YEAR. 
When all is said and done, the growth of individual trees only points 
the way to the forester’s real task, the maximum mean yearly production 
of timber per acre—the ‘‘acrim,’’ to use a convenient abbreviation. 
A quick-growing tree does not necessarily produce the highest acrim. 
Other things have to be considered. 
For the production of timber per acre per year in fully stocked areas, 
data from the cultivated forests of Europe are readily available. There 
are also data from regular regrowth forest in America, and from the 
country most like New Zealand, Japan. For New Zealand these data are 
wanting; and, so far as I have seen. there are no means of arriving at an 
estimate that would be sufficiently reliable and of general application. 
The returns from certain milled areas in New Zealand are known, but the 
age of every tree felled is different, and the rings of growth would not 
be clear enough throughout to compute averages, apart from other sources 
of error, such as the disregarding in the milling of unsound or small 
dominated trees. It is probable that from the few areas of regrowth 
forest that have escaped the general destruction an‘ area sufficiently 
regular to measure might be found. So far I have not seen such an area, 
but I have heard of them. As the forest becomes regularized and im- 
proved such figures will gradually become available. It is safe to con- 
clude they will be favourable for these reasons. 
The limiting factors of timber-production are primarily light and 
moisture, and secondarily the seasons of winter cold and summer drought. 
The air and space required for each forest-tree in popular writings have 
no more basis of fact than the heart as the seat of the affections in 
popular writing. New Zealand has the abundant light of its latitude, 
and over the greater part of its area a heavy well-distributed rainfall, 
together with mild summers and winters—all favourable to timber-pro- 
duction. Drought, such as limits the timber ‘‘stands’’ of Australia 
and South Africa, and even parts of eastern Europe. is absent from New 
Zealand. Schimper, amongst his many mistakes, misunderstood Brandis 
and quoted 40in. rainfall as the hmit for really successful forestry. 
Actually the limits vary according to the latitude, It is about 15 in. 
