Soil features, such as soil texture, mineral composition and soil moisture, and other features of land, such as topography, vary in their effect on forest growth depending upon regional climate. In Ontario, studies of land-forest relationships are conducted within the framework of site regions. Site regions are regions within which the effectivity of macroclimate is assumed to be relatively uniform since these regions are established through comparing the natural succession of vegetation on similar landforms, rather than by meteorological data. From the standpoint of forestry practice, the most pertinent feature of a site region is that it is an area in which similar responses may be expected from similar natural disturbances and forestry practices within similar combinations of landforms and forest types.Regional site research embraces, within each site region:(a) The establishment of landtypes and the description of the physiographic site types occurring within each landtype.(b) The description of the forest types coinciding with stages of succession within each physiographic site type.(c) The establishment of soil types coinciding with physiographic site types and major vegetation controls; also the establishment of variations in soil types resulting from differences in forest succession and forestry practice.(d) The evaluation of each physiographic site type for producing forest and other crops.Thus the aim of regional site research is (i) to describe the various physiographic conditions occurring in a site region so that foresters and land-use planners may recognize them, and (ii) to provide information regarding forest distribution, forest succession and the capability of these physiographic site types to produce forest and other crops, which information may aid these people in designing silvicultural experiments, in making forest management decisions, or in planning alternative uses of the land.Examples have been drawn from the site regions of Ontario to illustrate the principles and methodology of regional research.

Total site is that combination of environmental features with which the forest manager must deal in the growing and harvesting of forest crops. It is not enough to know the kind of regional climate, the zonal soil type and the regional cover type. The forester must know the significant features of each local area with which he has to deal.It is essential to know the variations in soil profile and forest communities at every stage in forest succession for each specific landform and climatic region. It is also necessary to know the effect of man's activities upon forest succession and soil characteristics. For the actual management of any specific forest area, a forester requires a knowledge of total site, not merely a classification of site.It is hoped that the proposed site classification may provide a scientific regional framework into which may be placed those significant site features with which a practicing forester must deal. The objectives of this site classification are twofold:1. To provide a systematic approach to forest description and site evaluation of local areas.2. To provide a framework to facilitate the application of results of forest research and practice to other areas.

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The first p a r t of this paper deals with a basic site classification designed t o provide a framework for assessing the capability of any area for forest production : the second part is a discussion of mapping methods with emphasis on the use of aerial photographs.Basic soil sites are described in terms of the moisture regime and the permeability of the soil materials and of the temperature and the evaporntivity of the local atmosphere. The simple terms or symbols used to indicate sequence in the intensity or level of these three most essential characteristics are also handles for a class of forest sites which can be subdivided o n the basis of any significant site feature. Though this is necessary for detailed studies. refinement is avoided as much as possible because of the overwhelming number of types. Grouping rather than subdivision is necessary for practical purposes since there a r e a t least three hundred basic soil sites (several times this figure, in fact, if even the most important variations are considered) for each climatic region. A chart is presented in which the one hundred and twenty-one sites (based on moisture and permeability and excluding ecoclimate), are grouped in thirty-three groups. An indication is given by the use of letter symbols, of the method by which these can be further grouped into five merchantable sites, four partially merchantable sites and two unmerchantable ones (the very dry and the very wet) making a total of eleven sites occurring within the normal or zonal ecoclimate of any one site region.Using a knowledge gained from field studies of the relationships of moisture and permeability to various recognizable characteristics of patterns of the following: (a) forest cover. (b) landform including length and per cent slope, (c) waterways, (d), rock-outcrop, and (e) land-use, basic soil si es are mapped from aerial photographs by noting the coincidences of moisture and permeability classes indicated by the overlapping patterns of the above named 'single' site characteristics. Seldom are the boundaries of the single characteristics actually marked on the photographs.

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