Treesearch

Three scales of aerial photography were tested in an attempt to determine the best scale to use in forest surveying. This was done by comparing photo measurements of average tree height, average crown diameter, and crown-closure percent. These stand variables were selected for testing because of their applicability in making aerial estimates of timber volume.

Aerial photographs are used widely in forest inventories. But there is a continuing need for improving the techniques of photo interpretation and making more efficient use of photographs. When the number or intensity of sample ground plots is controlled by airphoto classifications, a reliable stratification of the timber area is a must.

Melampsora leaf rust occurs in all countries where poplars are native or where they have been introduced for ornamental use or timber culture. The rust is easily recognized by the bright orange-yellow spore masses on the undersides of the leaves during most of the growing season.

In nursery seedbeds, severe root competition soon develops among seedlings of yellow birch (Betula alleghaniensis). This is due to the characteristic root system of the species - wide-spreading lateral growth with little downward penetration (fig. 1).

This is a report on the findings of the first comprehensive survey of the timber resources of Delaware. It describes, as of 1957, the area and condition of the forest land, the volume of standing timber, the annual growth and mortality of the forest growing stock, and the extent of timber cutting. The survey made by the Forest Service, U.S. Department of Agriculture, is a part of a nationwide survey of timber resources.

Trees, like other plants, contain many natural chemicals of the sort that we call hormones. Research is gradually revealing that, in the behavior of a tree, these chemicals may be almost as important as the basic influences of heredity and environment.

The exact value of thinning in managing hardwoods is not yet known. Further study of the many factors that affect thinning results is needed. These factors include methods and intensities of thinning, ages at which thinnings are started or repeated, effects of species composition in mixed stands, and influence of site index on response to thinning.

The trend of soil moisture during the growing season, the alternate wetting from rainfall and drying during clear weather, determines the amount of moisture available for tree growth and also fixes, in part, the environment for root growth. In much of the northern coniferous region both moisture content and root environment are in turn affected by the hummock-and-hollow topography so characteristic of the softwood forest types.

In the Coastal Plain from Virginia to Pennsylvania, snowstorms heavy enough to damage trees are unusual. Weather Bureau records for the general area show that heavy snowfall - 8 to 25 inches in a single storm - occurs at an average frequency of about once in 7 years.

The "green" in green ash (Fraxinus pennsylvanica Marsh.) refers to the leaves. They are nearly as bright green on the lower surface as on the upper. The specific Latin name 'pennsylvanica' was given to the species because it occurs in the United States and because in 1785 Pennsylvania and the American colonies were often considered as synonymous in the minds of European botanists.