1000 
investigations. They provide the most effective methods 
of combating climatic damage; as W. J. Humphreys once 
said with regard to fruitgrowing, ‘“The best time to 
protect fruit from frost injury is before the orchard is 
set out; obviously by carefully considering what kind, 
or even variety, to grow and where to grow it.” 
Often the farmer makes use of the artificial micro- 
climate inside a greenhouse. In general, greenhouses 
are still bemg constructed extensively according to 
traditional practical experience. Investigations by 
Made and Kreutz concerning greenhouse climates re- 
veal the extent to which microclimate depends on the 
materials and the methods of constructing and erecting 
various types of greenhouses. Air humidification by 
spraying has opened new possibilities of climatic con- 
trol. Great progress is yet to be expected from system- 
atic investigation along these lines. 
After a farmer has brought in his harvest, the dura- 
bility and quality of his product are determined by the 
microclimate of barns, shocks in the open air, silos, 
and storehouses. In the American occupation zone of 
Germany farmers are currently being advised by radio, 
on the basis of microclimatic measurements in experi- 
mental shocks, when they should ventilate their shocks 
or cover them more thoroughly. This practice has con- 
tributed greatly to the preservation of agricultural 
products. The health of dairy cows, hogs, ete., and the 
work capacity of animals depend on the microclimate 
of stables. Here also, research is in its fancy and these 
factors are only beginning to be considered in the de- 
sign of stables. 
The additive effect of changes in microclimate can 
influence the fertility of an entire country. The elimina- 
tion of innumerable small and minute windbreaks is 
known to have laid waste entire regions. The cultural 
planning of cities and industrial areas has caused dis- 
order in the hydrology of many a region. Fortunately, 
however, opposite instances are not lacking. Thou- 
sands of small hedges have afforded wind protection 
which increased agricultural yield and even improved 
large-scale climate. An interesting new example is of- 
fered by work done in Yakut in Siberia (Keil [19]). 
In 1939, under the pressure of war, workers began to 
clear large areas of a cushion of moss which had formerly 
served as a heat insulator and had consumed much 
- heat by evaporation. The exposed soil now absorbed 
heat from the sun. The frozen soil thawed to a greater 
depth from year to year; soon the first agricultural 
plants began to thrive. The virgin soil bore a good 
harvest. Today the region in question supports a large 
population, and this success was actually achieved by 
the application of microclimatological experience. 
Phenology as an Auxiliary Science. Phenology is 
currently developing into an important auxiliary sci- 
ence of microclimatology (Schnelle [28]). Phenology of 
plants concerns itself with the chronology of plant 
growth and its dependence on weather and climate. 
Suitable plants are used to observe the visible stages 
in growth, such as the development of the first leaves 
in spring, the first blossoms, the ripening of fruit, and 
the discoloration of foliage. Numerous observers, in 
CLIMATOLOGY 
Germany sometimes as many as ten thousand farmers, 
gardeners, etc., make systematic entries in this ‘‘Spheno- 
logical network.” 
The plant is thus used as an instrument for meteoro- 
logical observations. This procedure has the advantage 
that, with a judicious choice of plants, a large number of 
widely scattered observation pomts are obtained. In 
addition each plant reacts to the sum of all meteorologi- 
cal factors at its location near the ground (heat, rain, 
radiation, wind), thus representing a microclimatologi- 
cal instrument. The disadvantage of the method is the 
fact that every plant, as a living organism, is an in- 
dividual. Not only are different plant varieties affected 
differently by given weather conditions, but a different 
behavior is shown by every speeimen of a single species. 
This disadvantage can be compensated by the choice 
of particularly suitable varieties and by the observa- 
tion of a large number of single plants. Wild plants 
are more suitable than cultivated plants because the 
development of the latter may still be affected by 
cultivating methods such as choice of the time at which 
seeds are planted, treatment of the soil, or fertiliza- 
tion. 
As early as fifty years ago Ihne [15] prepared maps 
showing the arrival of spring in a region on the basis 
of such systematic phenological observations. These 
maps represent a survey of orographic microclimates 
on a correspondingly large scale. In judging the micro- 
climate of a region it is therefore advisable to observe 
the development of the plants very closely. Such ob- 
servations supplement a small number of accurate meas- 
urements made with the psychrometer and anemometer 
and aid in interpolating microclimatic data between 
points at which climatic conditions have been accurately 
determined by ordinary observing stations. 
Forestry and the Microclimate. A threefold connec- 
tion exists between microclimatology and forestry. 
Young forest growth develops either on large culti- 
vated areas, in which case it is subject to local micro- 
climatic conditions as are agricultural plants, or else 
it grows by natural seeding or is planted by a forester 
at the edge or in the midst.of the mother forest. The 
section on “Microclimates in the Vegetation Layer” 
already described the effect of all silvicultural measures 
on the microclimate of locations. Microclimatology is 
thus an auxiliary science of forestry. 
Secondly, the effect of weather damage in forests 
depends to a great extent on local conditions. Wind 
damage always begins at the weakest pomt. The prac- 
tice of eliminating such danger points by silvicultural 
measures requires a knowledge of the meteorological 
wind conditions. Topographic and vegetative obstacles 
must be considered in this connection. Snow damage 
and frost damage are also greater for certain tree forma- 
tions than for others. The effect of a drought depends 
upon the method of planting, the mixture of tree 
varieties, and the treatment of the soil. Even forest 
fires require certain conditions of the ground and the 
undergrowth which can be affected by cultivating tech- 
niques. The macroclimate and the location of the forest 
in question determine which kind of weather damage 
