Oaks

Water oak generally occurs in dense patches in temporary shallow pools beneath closed canopies. In such situations, natural regeneration occurs. Standing and moving water prevent reproduction establishment whenever seedlings are inundated for more than several weeks during the growing season. If submergence takes place prior to the growing season, seedlings remain dormant longer than usual in the spring and do not begin to make height growth until after water recedes. Regeneration usually fails if floods during the growing season occur too frequently for seedlings to have a chance between periods of high water to grow above the average depth of flooding.

Mesic oak seedlings rarely survive the low soil aeration conditions of inundation. Leaves of cherrybark oak and pin oak seedlings become chlorotic and roots die when the soil is saturated for several weeks. In this situation roots are not replaced through adventitious buds, and those that do form after excess water drains are weekly developed. One seldom finds white, cherrybark, and pin oaks on sites frequently flooded.36

In the upper reaches of the Delta, pin oak reproduction increases as overstories become heavier until basal areas reach 100 sq. ft. per acre. Thus harvest and mortality openings retard regeneration of that species while encouraging the entrance of more desirable broadleaf trees.

Fire wounds are the most important cause of decay in bottomland oaks. Among the infecting fungi are species of Polyporus, Corticium, Stereum, Poria, and Fomes. Rots not infrequently extend

Figure 4.23 Vigor of bottomland hardwoods relates to site quality. Nuttall oak vigor in the Mississippi Delta can be ascertained by observing the bark. The stem on the left shows poor vigor; on the right, high vigor. (USDA Forest Service photo)

2 feet above the top of a hollow made by fire or the bulge in the trunk. Heart rot, caused by Poria spiculosa, is extensive in these forests, probably infecting more than 1% of the oaks and hickories. Small, roughly circular cankers on boles with traces of a branch stub remaining in the usually depressed center indicate the presence of the brown decay. Fruiting bodies seem to occur only on dead wood in contact with the ground. Well established infections exhibit brown fungus matter readily available when the suspected tree branch is cut. Length of rot increases about 10 inches a year. Age of the infection can be readily determined by counting rings on the callus tissue formed around the infected branch trace.

Polyporus hispidus results in elongated swollen areas surrounding dead depressions or cankers which, upon recurrent killing of bark and cambium and renewed callus folds, give spindle-shaped swellings. Yellowish-brown to rusty-red conks 2 inches or more in width, spongy, hairy, and without a stalk, occur on surfaces of well-developed cankers in fall or winter. Drying to a rigid mass, the conks fall to the ground by spring. In summary, the many canker-forming fungi attacking hardwoods

Figure 4.24 Live oak growing in a second bottom. The species appears in many forms throughout the South. This specimen is typical of those used by ship-builders for knees in the days of the tall-masted ships. Scouts sent by the yards in the Northeast searched the river bottoms for stems that fit the naval architect's drawings, cut and hewed the timbers, and skidded them to a river's edge for shipment north. (Texas Forest Service photo)

Figure 4.24 Live oak growing in a second bottom. The species appears in many forms throughout the South. This specimen is typical of those used by ship-builders for knees in the days of the tall-masted ships. Scouts sent by the yards in the Northeast searched the river bottoms for stems that fit the naval architect's drawings, cut and hewed the timbers, and skidded them to a river's edge for shipment north. (Texas Forest Service photo)

enter through stubs of dead branches, work down the heartwood, and spread from the point of entry to kill the cambium.

Was this article helpful?

0 0

Post a comment