United States

Department of

Agriculture Improvements on

Forest Service

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Pg$

I”Io(m?.

a Reliable Oak Seed Trap

Southern Carl N. Phillips, Marianne K. Burke,

Research Station and Thomas B. Hunnicutt, Jr.

Research Note

SE-371

June 1995

Abstract

The need for seed trap longevity, capture of heavy seed, and protection from

predation in several forest types for long-term studies of seed production

prompted seed trap design improvements. Critical improvements were

achieved by painting the trap with a latex exterior gloss house paint, raising

traps above water lines in areas tbat flooded, and enclosing the seed container

in a protective cage made of hardware cloth. Forty improved seed traps were

installed in four forest communities across a flooding gradient and monitored

for structural integrity and seed capture over an g-month period. Ten traps

were placed in each of the following locations in the South Carolina Lower

Coastal Plain: a tupelo swamp, a transition to bottomland hardwood forest, a

bottomland hardwood forest, end a pine hardwood forest. All traps provided

protection from predators and effectively captured several seed types. The

use ofwater-based latex paint as a sealant inthe high humidity locale

enhanced the durability of the improved seed trap design.

Keywork Floodmg gradient, forested wetlands, predation, seed production,

seed trap.

Introduction

Estimates of forest production should include measurement of

seedfall, but traditional seed traps may be inappropriate for

long-term studies of seed production in some forest types.

For example, traps designed for collecting light seeds (Easley

and Chaiken 195 1, Houle and Payette 199 1) are not accurate

for collecting heavy seeds from species, such as oak and

hickory, because many of the heavy seeds bounce out.

Klawitter and Stubbs’ (196 1) improved design retains 90

percent of the heavy mast, but because the trap is paperboard,

it is not durable enough for long-term seed collection studies.

Carl N. Phillips is a Forester Trainee; Marianne K. Burke is a Research

Ecologist; and Thomas B. Hunnicutt, Jr., is a Forestry Technician, USDA

Forest Service, Southern Research Station, 2730 Savarmah Hwy., Charleston,

SC 29414.

The use. of trade or fum names in this publication is for reader information

and does not imply endorsement by the U.S. Department of Agriculture of

any product or service.

A mast production study in four wetland communities across

a soil moisture gradient prompted us to modify Klawitter and

Stubbs’ (196 1) seed trap. The traps had to withstand the

humid climate of the South Carolina Coastal Plain, accurately

collect a variety of seed types, remain intact for 3 years,

provide easy collection in both upland and permanently

flooded terrain, and resist animal predation. Other traps

shown to be effective in collecting the soft mast produced in a

cypress-tupelo swamp (Schneider and Sharitz 1988) would

probably have resulted in inaccurate seed production

estimates in upland sites because heavier seeds bounce out.

Because Klawitter and Stubbs (196 1) designed a trap that

was accurate for collecting acorns, we based our improved

seed trap on their design. Improvements include greater

durability, easy retrieval of collected seeds fi-om traps in

flooded areas, and protection from potential predators.

Methods

First, we converted available four-sided traps designed for

pine seed collection ( Easley and Chaiken 195 1) to threesided traps (fig 1.) according to Klawitter and Stubbs (1961).

Their modification increased the angle of the sides, reducing

the possibility that hard and heavy seeds would bounce out of

the trap. To improve durability, we reinforced the outside of

the seam with 1 -inch wide screen door molding strips. The

molding was stapled to the trap with %-inch long, 20-gauge

crown staples. The top 2 inches of cardboard were folded

down and 16-gauge metal wire was strung between the trap

and the folded flaps. Wire protruded as a loop from each

comer, and the flaps were stapled to the outside of the trap.

The three-sided trap of Klawitter and Stubbs (1961) was raw

paperboard and intended for short-term use only. We needed

a seed trap that would not deteriorate during a long-term

study. In an attempt to improve the durability of Klawitter

and Stubbs’ design, we treated and tested the traps for water
repel1

exteri

house

Figure L-Carl Phillips replacing protective cage on seed trap located in a Tupelo Swamp h the Donuelley Wildlife Management

Area in the AC.E. Basin of South Carolina’s lower Coastal Plain.

ency. We painted the traps with a water-based latex

or glossy house paint, an oil-based latex exterior glossy

I paint, and an oil-based stain. Forty traps were painted:

20 with the water-based paint, 10 with the oii-based paint,

and 10 with the oil-based stain. Paint was applied using

strokes in the direction of the eventual rainfall (vertical) to

facilitate the rapid drainage of rainfall.

Corn 4 to 8 feet in length. The longer lengths wert: used on

traps installed in areas that flood to ensure that the traps and

seed collection cages remained above the high wat :er level.

Notches were cut into the top of each pipe so the wire loop at

each comer of the trap could rest in the notch. This design

allowed easy removal of the trap from the support (fig. 2), an

improvement over Klawitter and Stubbs’ permanently

attached trap supports. The improved traps installed in the

swamp were emptied by removing them from the support

struts and tipping them so the trap could be accessed from

above. This method of trap support also simplified replacing

damaged traps.

Klawitter and Stubbs (1961) used wooden stakes to support

their seed traps. Because some of the traps in this study

would be installed in a swamp, or in areas subject to

occasional flooding, we needed more durable trap support.

Support struts of %-inch EMT conduit were cut, varying

Figure 2.

Support struta made of EMT conduit were notch4

linchiudepth. Thewireloopsrestinthenotches.

The trap can be removed by lifting the wire loops

from the notches. Strut length depends on level of

water rise.

Seed Trap Support System

l/2’ EMT’

Conduit
Bottom of seed trap

l/8” hardware cloth

4-114” Flower po

inside hardware

cloth cage

Because seed predation by animals was a potential problem,

the seeds collected in the trap needed protection (fig. 3).

First, V&inch mesh hardware cloth was placed in the bottom

of a 4 %-inch plastic flower pot to prevent loss of small seed

and to provide drainage. The flower pot was protected and

supported by a cylindrical cage made with a 15-inch by 12-

inch piece of lKnch mesh hardware cloth. The mesh

hardware cloth was notched in three places so that when it

formed a cylinder, it could be attached to the bottom of the

trap with the notches fitting the comers of the trap. A 5-inch

circular piece of Vs-inch mesh hardware cloth fastened to the

unnotched end of the cylinder became the bottom of the cage.

The flower pot was placed inside the cage and the cage

mounted on the trap by running a 12-inch, g-gauge metal pin

through the cage’s hardware cloth and the trap’s cardboard.

’ Notches cut to fit

corners of seed

trap exterior.

Figure 3.

The flower pot is completely enclosed in the hardwood

cloth cage. A metal pin driven through the hardware

cloth cage and the bottom of the seed trap attaches the

cage with flower pot inside to the trap and hinders

animal intrusion.

Application

Forty seed traps were installed during September 1993,lO in

each of 4 locations at the Donnelley Wildlife Management

Area in the Ashepoo, Combahee, Edisto (A.C.E.) River Basin

of South Carolina: a tupelo swamp, a transition to bottomland

hardwood forest, a bottomland hardwood forest, and a pine

hardwood forest. It took approximately two person days to

modify and install 10 newly designed traps. The sampling

area of the three-sided version is 4.72 square feet per trap,

and the dimensions for one side are given in figure 4. Seed

was collected from the traps approximately every 2 weeks

during the autumn and early winter and monthly during the

late winter and spring. It is assumed that the capture rate of

hard-mast seeds (90% from a go-foot drop) was the same as

that determined by Klawitter and Stubbs’ (1961) trap, and this

capture rate was not retested. During seed collection, all

traps were inspected for structural integrity.

/

1. Wire is placed around all section’s

outside flap. 2. The 2” flap is stapled to

the exterior of the trap.

I- 39 8116

II

attachment for

notched struts.

Figure 4.

Pattern for one side of a 0.1 l-milacre,

three-sided seed trap.

This flap is folded down

and tacked to the strip of

molding to form the

three-sided trap.

3
Results

The new trap design appeared quite durable and well-suited

to the humid climate in the South Caro!ina Coastal Plain

where the average annual rainfall is 52 inches (Landers

1970). The latex paint proved water repellent. The 20 traps

painted with the water-based latex exhibited good moisture

tolerance after 8 months in the field. Of the 10 traps treated

with the oil-based latex, 8 soaked up moisture, began to tear

at the corners and along the seams, and were replaced within

the fust 6 months. All 10 traps painted with the oil-based

stain exhibited severe water damage and were replaced with

water-based latex treated traps within 3 months.

The new trap successfully restricted predation of the trapped

seeds. Despite occasional signs of wild hogs and deer near

the traps and observations of turkeys, squirrels, and blue jays

in the area, no traps were disturbed. The deep seedcollection compartment and the cross pin blocking the

entrance to the compartment prevented entry by rodents and

birds to the flower pot in the hardware cage. The hardwarecloth cage prevented entry by larger animals from below.

However, some predation of seeds by birds is possible when

litter obstructs the seed collection compartment.

The new design allowed easy removal of the seeds and

replacement of the traps. This was particularly important in

the swamp where the water level ranged from 3- to 4-feet

deep, and the traps were supported 4-feet above the high

water line. All traps were emptied first by removing one

comer from the support strut and tipping the top of the trap to

access litter fall. Afterwards, the collection container pin was

pulled and the seed removed from the flowerpot in the

hardware cage.

Discussion

Our improved trap is versatile and adequately collected a

variety of seed types. The seeds were easily retrieved from

above or below the trap, an important feature at the swamp

sites that were only accessible by foot. In addition, trap

integrity remained high in the humid environment of the South

Carolina Coastal Plain. Although other styles of traps

appeared effective in catching the sotI mast falling in a tupelo

swamp (Schneider and Sharitz 1988) and light seeds falling in

upland sites (Houle and Payette 1991), our trap was more

versatile among the forested wetland community types.

Whether in the swamp or on upland sites, the trap design was

effective in preventing predation on the collected seeds.

Predation on seeds has an important impact on plant

population biology (Harper 1977), and when an accurate

measurement of seed production is sought, the traps must

restrict predators. Apparently, the hardware cloth cage

securing the flowerpot to the trap adequately repelled animals.

In contrast, the collection container used by Klawitter and

Stubbs (1961) and unattached bucket types of containers

allow deer, hogs, blue jays, turkey, and squirrels access to the

collected seeds.

The improved seed trap takes longer to install than the

Klawitter and Stubbs’ trap, but the moditications are worth the

extra effort for long-term seed production studies. A key to

trap longevity was the water-based latex paint, which

provided total trap integrity 6 months atIer installation. The

oil-based latex paint and oil-based latex stain provided little

protection from moisture and could possibly cause water

contamination. Whether placement of the pm through the

base of the trap contributes to trap longevity is unknown. The

pin placement exposed unpainted cardboard to the weather

and could weaken the trap. If traps are weakened by pm

placement an alternative method of connecting the hardware

cloth cage to the trap will be needed.

Other seed traps, such as plastic trash cans, milk jugs, and

nets offer good capture of seed crops and can be used for

collecting specitic seed types over the short term. However,

the advantages of our improved trap include versatility among

forest types, durability, and resistance to seed loss from

predation. Seed trap sides used in construction of the

improved reliable oak seed trap may be obtained from

Palmetto Packaging Company, Attention: Mr. Paul Stewart,

P.O. Box 4740, Florence, SC 29502.

Literature Cited

Easley, LT.; Chaiken, LE. 1951. An expendable seed trap. Journal of

Forestay. 49: 652-653.

Harper, J. L. 1977. The population biology of plants. New York: Academic

Press 457-468.

Houle, 6; Payette, S. 1991. Seed dynamics ofAbies balsamea and Acer

sacchancm in a deciduous forest of Northeastern North America

American Journal of Botany. 78(7): 895-905.

Klswitter, Mph k, Stubbs, Jack 1961. A reliable oak seed trap.

Journal of Forestry. 59: 291-292.

Landers, H. 1970. The climate of South Carolina Climates of tbe States.

Port Washington, NY: Water Information Center, Inc. 1: 353369.

Schneider, R. L, Shnritz, RR 1988. Hydrochory and regeneration in a

bald cypress-water tupelo swamp forest. Ecology. 69: 1055-1063.

Southern Research Station, P.O. Box 2680, Asheville, NC 28802