Effect of Soils on the Establishment of Tree Crops

The importance of soil factors to the establishment of tree crops is well recognized by forest soil scientists and foresters. It has, however, been overlooked by far too many foresters responsible for major forestation projects. The soil factors found to be significant in the establishment of both planted stock and seedlings from natural or artificial seedf all are: texture and structure characteristics of the soil profile as they affect moisture and aeration; depth to the ground water table; content of soil organic matter; chemical properties, including soil fertility and the occurrence of layers high in soluble salts and toxic substances. The importance of producing nutritionally balanced or physiologically balanced planting stock has been recognized, and more attention is being paid to nursery soil management practices in an effort to improve the survival qualities of seedlings. The importance of mycorrhizal fungi as related to seedling survival has also been well established. These relationships are well recognized in the east where foresters have been at grips with the problems for some time. In the west, foresters are just beginning to see the significance of soil factors; the specific soil-site relationships affecting the survival and growth of a tree crop need to be established for western conditions. O NE of the most significant site factors affecting the successful establishment of tree crops is the edaphic factor. Forest soil scientists and many foresters have been well aware of this fact, and in the planning for reforestation programs a thorough evaluation of soil conditions has been included. These evaluations have ranged from preplanting soil surveys to on-thespot analyses of certain soil properties known to be significant to seedling survival. Many foresters who are responsible for seeding and planting programs still disregard the all-important basic resource in planning reforestation operations. Chapter 5 of the "Reports of the Pacific Northwest Seeding and Planting Committee on Various Recommended Reforestation Practices" is a case in point. This chapter, in dealing with factors affecting plantation survival, discusses the natural hazards having a bearing on plantation success. Weather, animal damage, vegetative competition, and insects and disease are discussed, but no mention is made of the quality of the soil on the planting site. The chapters on direct seeding and on reforestation surveys in this same report give only a superficial discussion of soil factors. It is obvious then, that forest soils research workers and teachers still have a big job in educating the practicing forester and convincing him of the importance of a thorough knowledge of soils to forest manage-