stands, the mature cedar has a long, clear, almost 

 cylindrical bole which rapidly tapers within a short 

 crown. The crown in dense stands is typically short, 

 narrow, and conical, usually covering the upper 30% 

 of the trunk. Open-grown trees are more tapered, 

 with longer crowns and more limbs than those grow- 

 ing in a dense stand (Korstian and Brush 1931). 



3.1.2 Boots 



The root system of C. thyoides is shallow 

 and spreading, penetrating only the upper 0.3 to 0.6 

 m of peat when the substrate is permanently 

 saturated. Roots extend deeper when the water 

 table is not as near the surface. 



3.1.3 Lea^ffis 



The mature leaves are flat, small, over- 

 lapping scales with a prominent resin gland and 

 numerous ring structures. The microscopic struc- 

 ture of cones, leaves, seeds, and pollen is described 

 by Belling (1987). 



3 1 4 FInwerinq and Fruiting 



Atlantic white cedar is monoecious, but the 

 staminate (male) and pistillate (female) flowers are 

 produced on separate shoots. Flower buds are 

 formed in spring in the Virginia-North Carolina area 

 (Korstian and Brush 1 931 ) and in summer in southern 

 New Jersey (Little 1941). When mature, the four- 

 sided, oblong, brown staminate flowers are about 3 

 mm long. The pale green 3 mm-wide pistillate 

 flowers are borne on short lateral branchlets of ter- 

 minal shoots (Korstian and Brush 1931) (Figure 19). 



Pollen . Pollen grains are spheres 21 to 24 

 jum in diameter with an outer sculptured wall. As the 

 pollens of C. thyoides, arbor-vitae (Thuja occiden- 

 talis), and red cedar (Juniperus virginiana) are super- 

 ficially indistinguishable in form (Belling 1977, 1987), 

 the three species have been recorded by palynol- 

 ogists as "cedar" (Cupressaceae) despite their sig- 

 nificant differences in habitat. 



The light-green angular six-sided cones ma- 

 ture in early autumn and become dark red-brown the 

 following year. 



Seeds. The 3 mm-long, fiat, rounded seeds 

 are encircled by a darker winged membranous mar- 

 gin. There are ca. 1,014,000 seeds/kg; the average 

 weight per thousand is 0.96 g. 



3.2 SILVICAL HABITS 



3.2.1 Seed Production and Dissemination 



Production . The onset of seed production 

 varies greatly with environmental conditions: the 

 climate, water level, substrate, and competition with 

 other cedars and other species. Little (1950) ob- 

 served that the onset of cone-bearing in New Jersey 

 cedars in natural stands ranged from 7 years on 0.24 

 m trees through 22 years on 1 .28 m trees. Nursery- 

 grown field transplants produce seed as early as 3 

 years after germination. 



Little (1950) noted that trees growing in the 

 open tend to produce more cones than those in 

 clumps, although dominant trees in clumps may be 

 as prolific as open-grown trees of the same size. The 

 amount of seed produced varies from year to year; 

 abundant crops occur at about 2- or 3-year intervals 

 (Cottrell 1929; Little 1950). 



Dissemination . Seed dispersal is influenced 

 by weather (temperature, relative humidity, rainfall, 

 wind direction, and velocity), the height and diameter 

 of the parent tree, and the density and height of sur- 

 rounding vegetation. Seed dispersal starts in early 

 autumn; most of the seed is released before the end 

 of winter In New Jersey, the peak of seedfall occurs 

 in a 2-week period in late October and early Novem- 

 ber (Little 1941). 



In seed-trapping experiments. Little (1950) 

 confirmed that density and height of the surrounding 

 vegetation can almost completely prevent the disper- 

 sal of seeds beyond the edge of a stand. Seedfall per 

 unit area decreases greatly as distance from the tree 

 increases. Heavy rainfall causes complete closing of 

 the cones; lighter rain reduces the rate of seedfall due 

 to the partial closure of cones (Little 1940). High 

 winds increase the quantity of seeds falling; wind 

 direction also greatly affects seed movement (Little 

 1940). 



Seed viability . Seed viability is highly vari- 

 able. The most important factors appear to be the 

 age, genetics, general health, and nutrition of the 

 parent tree; climate; and weather The first seed 

 crops of a tree have a lower average germination rate 

 than later production. 



Germination . Under natural conditions, 

 much white cedar seed does not germinate until the 

 start of the 2nd or 3rd growing season after seed fall 

 (G. Emerson 1846; Moore 1939; Little 1950). Over- 

 winter storage in a cool, moist medium, such as the 

 moss and peat of a swamp floor, apparently 

 promotes germination. 



27 



