No. 93 

1959 

NATURAL REGENERATION IN BOTTOMLAND 

HARDWOODS OF SOUTHERN NEW JERSEY 

What kind of natural regeneration follows cutting in 

the bottomland hardwoods of southern New Jersey? 

Some practicing foresters in this section have observed that dense shrubby understories are usually quick to develop after cutting and that these understories suppress desirable tree reproduction. For example, smith1 noticed that 

imperfectly and poorly drained loams usually supported luxuriant understories of shrubs and herbs, and cutting often so 

stimulated these understories that they limited the growth 

of desirable tree reproduction. In some areas he noticed no 

desirable reproduction even 10 years after cutting. This 

is quite different from experience in the South, where 

shrub-vine understories on bottomland sites do not seriously 

hinder stand regeneration? 

This note describes changes over a 12-year period in 

reproduction in two cut-over bottomland stands of southern 

New Jersey. 

Study Areas 

Both of the stands studied are on relatively level, 

poorly drained soils of the Fallsington series. In 1945 

these stands were 75 to 80 years old. In Stand A, red oaks 

(chiefly pin oaks) and sweetgum accounted for 78 percent of 

the stems larger than 2.6 inches d.b.h. In Stand B, the red 

oaks, white oaks, and sweetgum comprised 64 percent of the 

stems; red maple accounted for another 26 percent. 

In the winter of 1945-46, both stands received a light 

'smith, G.F. Observations on managing hardwoods in the Delaware Valley of 

southern New Jersey. Jour. Forestry 51: 189- 191. 1953. 

L~utnam, J.A. Management of bottomland,hardwoods. U. S. Forest Serv. South. 

Forest Expt. Sta. OCcas. Paper 116. 60 pp. 1951. 
Table 1.--~ominancel of desirable and undesirable vegetation 

in the understory, 1946 and 1958 

Kind of vegetation 

Percent Percent Percent Percent 

Desirable trees: 

Sweet gum - - 35 30 3 3 

Yellow-poplar -- -- 5 10 

Ash -- - - 3 3 

oaks2 - - 2 - - 9 

Total 0 3 7 3 8 55 

Undesirable vegetation: 

~rees~ 5 16 18 20 shrubs4 53 32 22 20 

Herbs 4 2 15 22 5 

Tot a1 100 63 62 45 

i~ominance: the tallest plant on the quadrat. 

31ncludes black, southern red, pin, willow, white, and swamp white oaks. 

Includes red maple, blackgum, sweetbay, aspen, sassafras, hophornbeam, 

black cherry, and gray birch. 

4~h~ef ly southern arrowwood, sweet pepperbush, elderberry, spicebush, and 

deciduous holly. 

cut, the first cut of a 2- or 3-cut shelterwood system used 

in managing such stands in this section.3 Sixteen red oalcs 

containing 5,193 board-feet (Doyle Rule) were removed from a 

1-acre plot In Stand A. From a similar plot in Stand B, 14 

red oaks with a volume of 4,481 board-feet (Doyle Rule) were 

cut. The cutting left 94 trees, mostly larger than 11 inches d.b.h., in the Stand A plot; and 114 trees, mostly larger 

than 12 inches d.b.h., in the Stand B plot. Oaks and sweetgum together formed 77 percent of the stems left in the 

Stand A plot, 60 percent in Stand B. 

In Stand A, a second cut was made in 1953, largely because waste water from a nearby mill was damaging overstory 

trees. A considerable portion of Stand B was blown down by 

a 1954 hurricane, so a salvage cut was made there in 1955. 

These cuttings left few overstory trees in either 1-acre 

plot. 

Although neither plot contains seed-producing sweetgums or red maples, both receive abundant seed of these 

species from adjacent areas. In 1958, no source of acorns 

remained on the plot in Stand A, but the Stand B plot had 

several residual oaks of seed-bearing size. 

'~oore, E.R., and Lentz, A.N. ?he cooperative forest management program i? 

New Jersey. Jour. Forestry 49: 31-34. 1951. 

2 

I 

Stand A 

quadrats dominated in: 

1946 

Stand B 

quadrats dominated in: 

1958 1946 1958 
Study Methods 

On the 1-acre plot in each area, 60 milacre-quadrats 

were established, 30 along each of two permanently marked 

lines. Tree reproduction, shrubs, and herbs were tallied on 

each of the quadrats in the summer of 1946 after the initial 

cut. The last tally was made during the s-er of 1958. 

Results and Discussion 

Although the understories of the two stands differed 

in 1946, they have undergone similar changes since then 

(table 1) . Now, undesirable vegetation dominates much less 

of the understory than it did in 1946, Herbs decreased the 

most; shrubs also declined; while among the undesirable 

vegetation--which lessened as a whole--trees assumed more 

importance. 

The gain in desirable tree reproduction was greatest 

in Stand A, and was practically all due to the assumption of 

dominance by sweetgum (table 1). But in 1946 no desirable 

reproduction was dominant on any quadrat in that stand. In 

contrast, Stand B then had 38 percent of its quadrats dominated by desirable tree species. On this plot yellow-poplar 

and oaks accounted for most of the 17-percent gain during 

the followirig 12 years. 

Although oaks formed a major part of the harvested 

stands, they are less important in the reproduction. In 

1958, sweetgum dominated the most quadrats in both stands, - while oaks dominated less than 10 percent of the quadrats. 

In Stand A, oak reproduction was found on only 15 percent of 

the quadrats, indicating that it may form little of the next 

Table 2.--Occurrence of desirable reproduction, 1946 and 1958 

On quadrats dominated by Stand Species On all quadrats undesirable vegetation 

1946 1958 1946 1958 

Percent Percent Percent Percent 

A Sweetgum 52 4 7 52 2 1 

Yellow-poplar 7 -- 7 - - oaks1 7 15 7 13 

Desirable 5 5 5 5 55 29 

B Sweetgum 

Yellow-poplar 

Ash - - 

oaks1 3 2 30 

Desirable 8 8 

'~ncludes black, southern red, pin, willow, white, and swamp white 

oaks. 
crop. However, oaks did occur on 43 percent of the Stand B 

quadrats (table 2) where many may become a part of the next 

overs tory. 

If uniformly spaced, the desirable stems now dominant 

(370 per acre in Stand A, 550 per acre in Stand B) would 

provide desirable future stands. Unfortunately, the spacing 

is not uniform; in certain cases the distance between quadrats containing dominant desirable stems is over 50 feet. 

Still, the present spacing should improve because: (1) only 

3 or 5 years have elapsed since the final cut; (2) desirable 

subdominants now occur on 29 or 82 percent of the quadrats 

dominated by undesired vegetation; and (3) sweetgum seed is 

still falling in both plots. 

In view of these facts, and because hardwood crop 

trees number only about 100 per acre in mature stands, the 

reproduction of both areas offers promise of forming satisfactory stands. However, results here seem better than in 

many New Jersey bottomland stands where longer intervals between cuts, or repeated light cuts, have favored dense 

shrubby understories. 

Conclusions 

Results of this study indicate that natural reproduction will provide desirable stands in bottomland hardwoods 

harvested by proper use of the shelterwood system. 

--H. B. TEPPER 

Northeastern Forest Experiment Station 

Forest Service, U.S. Dept. Agriculture 

and G. T. BAMFORD 

Forest Management Section, N. J. 

Dept. of Conservation and Economic Development 

AGRICULTURE-FOREST SERVICE-UPPER DARBY