Treesearch

Sharkey clay is now important to the Southern forest industry because it supports so much of the hardwood resource-more than any other soil within the Mississippi Delta-and its extent will continue to make it important to Delta forestry.

The Coastal Plain soil area occupies the major portion of Mississippi east of the Delta and Loess areas. In general, the soils are sandy, acid, and lacking in natural fertility, but on the alluvial soils moisture and drainage relations appear sufficient to support good growth of some tree species.

Some of the finest forest land in the country is in the batture of the Mississippi River - the area between the levees and the river. Many of these sites once bore nearly pure stands of cottonwood, and cottonwood probably is the most valuable timber crop that could be grown on them today. After the old-growth was harvested, though, the sites were taken over largely by trees of inferior species and form.

Studies of the Populus tremuloides root system by Day (1944), Sandberg (1951) and Barnes (1959) have all shown lateral roots extending as much as 30 feet from tree base. These roots may branch extensively and sometimes exhibit an "undulating" growth habit. According to the above authors, suckers occur on the segments of these lateral roots which are closest to the soil surface. The objective of this investigation was to quantitatively determine root depth and diameter at the point where suckering occurs. Both trembling aspen (P. tremuloides) and bigtooth aspen (P. grandidentata) were studied.

Root suckering is the primary mode of regeneration in the aspens, Populus tremuloides Michx. and P. grandidentata Michx. When stems of these species are cut, numerous suckers originating in the root pericycle are formed on their extensive lateral root systems. During their first season of growth, suckers ordinarily reach a height of 3 to 5 feet. As many as 20,000 suckers per acre may occur after clear-cutting of well-stocked stands of P. grandidentata.

Since the recognition of natural hybridization of small-leaf (West Indies) mahogany (Swietenia mahagoni Jacq.) with bigleaf (Honduras) mahogany (S. macrophylla King) there has been conjecture about their relative growth rates. One would expect small-leaf to be the fastest growing on dry sites, the hybrids to be fastest on intermediate sites, and bigleaf to excel on wet sites.

The dry limestone hill region of southwestern Puerto Rico, because of heavy, shallow soils and scant rainfall is not farmed, and is recognized as an area best suited for the growth of trees. With a mean temperature near 80°F and with rainfall averaging no more than 30 inches anually and much less during dry years, the site is adverse even for tree growth. Studies on this area have been under way for several years to determine the diameter growth rates which can be expected.

Before beginning a growth study in tropic or temperate regions a specific problem should be selected for solution. Once the problem is selected use· all available information on the forest in particular and statistical probabilities in general to reduce the number of measurements necessary and increase the reliability of those made. These two steps can tremendously reduce the costs of and increase the useful information from growth studies. Unless labor is very cheap, weekly diameter measurements are probably best made with vernier bands. Longer-term measurements can be made satisfactorily...

A study was made of the putative hybrid of bigleaf and small-leaf mahoganies. Initial measurements indicated that bigleaf mahogany can be distinguished from small-leaf mahogany by gross measurements of leaflets. Isolated mother trees yield typical progeny. Typical mother trees in mixed stands yield like progeny plus, usually, mediumleaf progeny. Mediumleaf mother trees yield mixed progeny and usually yield all three types: bigleaf, small-leaf, and mediumleaf. Although there must remain an element of doubt until hand pollinationunder controlled conditions is accomplished, it seems apparent...