Treesearch

The past few years have seen increased interest in and use of microbial agents for the control of destructive forest insects. One of the most successful applications of this control method has been the use of the polyhedral virus disease of the European pine sawfly, Neodiprion sertifer (Geoff.). Control of this insect by its specific pathogen has been fully as satisfactory as chemical control, and less expensive.

Scarification of the soil creates seedbeds that are favorable for the establishment of both paper birch and yellow birch. Logging in the summer often has been recommended as a method of obtaining these seedbeds. However, our observations on experimental logging jobs have shown that logging alone does not provide scarification over enough of the area to assure reasonably uniform distribution of birch regeneration.

Hybrid poplars, crosses between European and American Aigeiros poplars, have been grown in Europe for about 200 years. The rapid growth and high productivity of some of these hybrids on sites to which they are adapted has stimulated interest in poplar growing in this country. And demand for these poplars is developing in many parts of the United States.

Experimentation on small watersheds is assuming increasing importance in watershed-management research. Much has been accomplished in developing adequate instrumentation for use in these experiments. Yet many problems still await solution. One difficulty encountered is that small streams are subject to wide variations in flow and that these variations are generally unpredictable; so it is often impossible for personnel to be on the spot at the right time to take samples or to service installations.

Harvesting timber on lands devoted primarily to watershed management may alter, for better or worse, many features of a forested watershed. One such feature is forest humus. The beneficial role of forest humus in watershed management is widely recognized. A protective mantle of humus serves to cushion the impact of rain, to impede surface runoff, to restrict soil freezing, to favor infiltration, and to store certain amounts of rainfall.

On the Dilldown Unit of the Delaware-Lehigh Experimental Forest in Pennsylvania, several planting studies have been made with the aim of finding the most economical and practical methods of converting scrub oak areas to productive high-forest types. These studies have already shown the need for site preparation prior to planting. Seedlings planted on prepared areas grew significantly faster than those in the untreated areas.

Atlantic white-cedar typically grows in dense stands. In southern New Jersey, young stands commonly contain several thousand trees per acre, and at ages around 60 years there still may be 1,000 or more trees per acre.

The Northeastern Forest Experiment Station, in cooperation with other experiment stations in the United States and Canada, began a range-wide provenance test of eastern white pine (Pinus strobus L.) in 1955. Seed was collected from 31 different locations in 17 states and 4 Canadian provinces. In most places collections were made from 10 trees at each location. The seed from individual trees was kept separate.

In 1948, a dieback of sweetgum (Liquidambar styraciflua L.) was first observed and reported at College Park, Md. Since then, surveys made from Maryland southward have shown that the dieback, now termed sweetgum blight, has increased in both distribution and severity and now occurs throughout much of the species range. No pathogenic organism has been found to be associated with this blight.

In November 1952 a hot surface fire burned through part of a 30-year-old Virginia pine-hardwood stand near Beltsville, Md. Observations were made for the next 2 years to evaluate the effects of this type of fire under these stand conditions. The main direct effects during the 2 years, as reported by Church in 1955, were: 45 percent mortality of trees 1 inch d.b.h. and larger, principally in the smaller size classes; and destruction of any pine seedlings that may have been present. An indirect effect, on the credit side, was the establishment of almost 11,000 pine seedlings per acre on the...