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Wildlife, Animals, and Plants |
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BOTANICAL AND ECOLOGICAL CHARACTERISTICS
GENERAL BOTANICAL CHARACTERISTICS:Eastern cottonwood is a native, deciduous bottomland hardwood [68,121,132,212,225]. Height ranges from 36 to 190 feet (11-57.9 m) [37,47,56,67,120,132,150,151,224]. At maturity (approximately 35 years) [132], diameter at breast height ranges from 10.7 inches to more than 6 feet (27.2-182.9 cm) [7,47,67,132,150,224]. In open areas, eastern cottonwood typically has a large trunk that divides into branches near its base and ascends to form a wide, spreading crown [47,100]. In closed stands, it tends to have a tall, straight, and relatively branch-free bole with a small rounded crown [9]. Life expectancy is approximately 100 to 200 years [9,120,142]. It is dioecious. Female catkins range from 2 to 5.1 inches (5-13 cm) long, and fruit capsules are 0.3 to 0.6 inch (.8-1.5 cm) long [56]. The bark is thick and deeply furrowed with wide, flat ridges [56,199]. The rooting depth averages 100 inches (254 cm) [97], and mature stands can reach 117.6 to 196.8 inches (298.7-499.9 cm) rooting depth [22]. Eastern cottonwood is drought tolerant [47,77]. It has been classed as moderately tolerant to water-logged soils [106,110] and is tolerant of short-term inundation [145]. Eastern cottonwood tolerates periodic flooding from January through April, but mortality and growth due to flooding depend on how many events per year, season of year, age class, duration, and depth [89,106,149]. A study using cuttings found that eastern cottonwood survived less than 16 days of complete submergence [109]. Roots die when soaked for more than 1 month and adventitious roots form from dormant buds in the main trunk [110,220]. Plains cottonwood is a quick growing, short-lived deciduous tree [4]. It is smaller than P. d. ssp. deltoides [173] and grows from 10 to 98.4 feet (3-30 m) [4,36,58,124,130,139,173,195,207,223]. It has a diameter at breast height of 5 to 78.7 inches (12.7-200 cm) [4,58,107,124,130,139,173,207]. It is considered the fastest-growing tree in the Great Plains. The life expectancy is about 90 years [173]. Staminate catkins of plains cottonwood range in size from 2 to 3.5 inches (5-9 cm), pistillate catkins are 5.9 to 7.9 inches (15-20 cm) long, and fruits are 0.4 inch (1 cm) in length [173]. Plains cottonwood is susceptible to drought except where water tables are high [4] and drought induced mortality can be high [173]. The average rooting depth is 10 feet (3.1 m), and the longest roots can reach 75 feet (22.9 m) [231]. Rio Grande cottonwood ranges in height from 26.2 to 65.6 feet (8-20 m) [56,59]. It has catkins with pedicels 0.2 to 0.6 inch (.5-1.5 cm) long [56].
RAUNKIAER LIFE FORM [172]:Phanerophyte
REGENERATION PROCESSES:Eastern cottonwood regenerates sexually and vegetatively. Sexual reproduction: Large seed crops (25 to 28 million seeds/tree/year) [9,22,129] dispersed by wind and water over long distances, are generally produced annually once the trees reach 10 to 15 years of age [9,22,47,132,142,158,173,221,225]. There is no seed dormancy in eastern cottonwood [227,228]. Germination occurs as soon as seeds arrive on a seedbed that is moist, free of vegetation, and in full sunlight [9,23,67,132,173,181]. Seeds are highly viable at dispersal [66,124], but viability decreases rapidly in the absence of a suitable germination environment [66]. Under natural conditions, seeds remain viable for 1 to 2 weeks [22]. Suitable recruitment sites occur naturally as a result of spring flooding [156,173] and scouring by ice [9]. Receding floodwaters leave freshly deposited, exposed alluvium, and seed germination along prairie river floodplains often occurs exclusively on these sites [124,229]. Exposed soil is essential, as young seedlings do not compete well with overtopping vegetation [34,124,171]. Vegetative reproduction: Cottonwood species (Populus spp.) reproduce vegetatively by sprouting from stumps and root crowns, and by the formation of suckers (adventitious shoots on roots ) [47,176,229]. There is asexual reproduction from broken limbs (flood training) and crown breakage [22]. The ability of cottonwoods to sprout declines with age [173]. Cottonwoods in the Aigeiros section of Populus, including eastern cottonwood, do not sprout as readily as cottonwoods in section Tacamahaca. Eastern cottonwood sprouts from the roots and bole after top-kill or damage, but the response is weak [22,86]. Most suckers arise from suppressed buds embedded in the periderm of undisturbed roots after death or injury of aboveground parts. There is disagreement on the ability or eastern cottonwood to sprout from the bole after being cut [47,154]. Plains cottonwood does not readily form suckers or stem sprouts [87,132], and sprouting is uncommon except in flood-trained shoots [23,86,179]. Growth: Eastern cottonwood is the fastest growing native tree in North America [28,47,121,132,212]. It commonly increases 0.7 to 1 inch (1.69-2.54 cm) in diameter and 5 feet (1.5 m) in height annually up to 10 to 15 years of age, and grows at only a slightly slower rate up to 30 to 35 years of age [28]. In the Mississippi valley, eastern cottonwood can reach 20 inches (50.8 cm) in diameter at breast height and 120 feet (36.6 m) in height at 35 years [28,145]. Growth of young seedlings is rapid [132]. The first 3 weeks of development of seedlings are slow, after which the growth rate rapidly accelerates [145]. Root growth of seedlings is also rapid. Seedlings have been observed to extend taproots 12 to 16 inches (30.5-40.6 cm) and lateral roots 24 inches (61 cm) by the end of their first growing season [222]. These roots serve as anchorage during floods and help to ensure a supply of water during dry periods. Once established, seedlings are susceptible to damage from flooding. In one instance, 8 days of complete inundation weakened all seedlings, while 16 days resulted in their mortality [112]. Seedlings can survive if flooded less than 50% of the growing season [158]. Inundation does not necessarily have a detrimental effect upon germination [108].
SITE CHARACTERISTICS:Eastern cottonwood primarily grows on the moist alluvial soil of floodplains and bottomlands [132,145,158,171,229]. It is also found in ravines [16,107,229], along disturbed streams [117], and in low spots of sandy uplands with a high water table [229]. It also found on batture lands, the unprotected areas between the Mississippi River and its levees [145]. Plains cottonwood is found on floodplains and small sandbars in the river beds or large bends where stream flow is dramatically retarded during high water. It is found next to springs that flow long enough to form ponds [4,130,173]. Across its range, eastern cottonwood is found from 255 to 6,500 feet (78-1,981 m) [10,12,37,165,169,187], usually 15 to 40 feet (5-12 m) above stream level [90,151,187]. Elevation ranges for plains and Rio Grande cottonwood are given in the following table:
The average annual precipitation across the eastern cottonwood range is 13.78 to 55 inches (350-1,397 mm) [125,169]. Average annual precipitation ranges for some states where eastern cottonwood occurs is listed below:
Eastern cottonwood occurs in a wide range of temperature regimes with extremes ranging from -49 degrees Fahrenheit (-45 oC) in winter to 114.8 degrees Fahrenheit (46 oC) in summer [125]. The mean annual temperature or annual temperature range for some states is as follows:
The annual precipitation varies between 12 and 30 inches (305-762 mm), averaging less than 20 inches (508 mm) across most of the plains cottonwood range. The temperature can range between -50 degrees Fahrenheit (-45.56 oC) in January and 115 degrees Fahrenheit in July (46.11 oC) [173]. The average annual precipitation and temperature for some states in the plains cottonwood range are given in the table below [4,11,15,20,36,73,82,104,105,124,127,130,146,162,175,182,186,198,208,221,231]:
Eastern cottonwood tolerates a wide range of soils ranging from coarse sands to clays but grows best on moist, well-drained fine sandy loams or silt [47,90,129,145,151,154,158]. Plains cottonwood is found on sandy soils [124,130] or well-drained soils with a high water table to supply year-round moisture [4]. Availability of moisture is reportedly more significant to plains cottonwood than soil texture or fertility [173].
SUCCESSIONAL STATUS:Eastern cottonwood is shade intolerant [9,47,151,171,217,225] and a pioneer species that typically establishes on freshly exposed alluvium of sandbars, streambanks, and other floodplain sites [16,23,103,117,124,150,222]. Establishment and dominance may also occur after sandbar willows have stabilized the site [229]. Eastern cottonwood invades unburned prairies in Kansas [1] and old fields and upland sites in the lake states [47,111]. Maintenance of seral, eastern cottonwood-dominated communities depends on either periodic flooding or timber harvest [23,92,155,158]. In the Great Plains, dams and reservoirs which alter the magnitude and frequency of floods, sedimentation rates, and stream meander migration rates have detrimentally affected cottonwood communities by reducing seedling recruitment and survival [23]. In the absence of flooding, succession proceeds, and the shade-intolerant cottonwoods are eventually replaced by more shade-tolerant species [155]. Eastern cottonwood stands are replaced by American elm, sycamore, pecan, sugarberry, boxelder, and sweetgum [103]. The eastern cottonwood/Rocky Mountain juniper community type is an early successional stage in North Dakota. It succeeds to the green ash/western snowberry community if left undisturbed [83]. Plains cottonwood with willow and boxelder represents an early stage on floodplains in Nebraska [4]. The plains cottonwood-willow type progresses to the plains cottonwood-green ash type in North Dakota [124]. It contributes significantly to dune formation on Lake Michigan [38].
SEASONAL DEVELOPMENT:Time of flowering and leaf emergence for eastern cottonwood varies according to geographic location. Eastern cottonwood flowers during early to late spring, generally from February through May [22,47,68,147,228] and 1 to 2 weeks before leaf initiation [22]. Seed dispersal occurs in early summer [47]. Seed dispersal and germination generally occur in late spring to early- or mid-summer and typically coincide with decreasing flow levels (May through August) [9,22,40,66,181]. Phenological dates for some states and the Great Plains are given below:
Related categories for SPECIES: Populus deltoides | Eastern Cottonwood |
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