PIGNUT HICKORY (Carya glabra)
Carya glabra, the Pignut hickory, is a common, but not abundant species in the oak-hickory forest association in the Eastern United States and Canada. Other common names are pignut, sweet pignut, coast pignut hickory, smoothbark hickory, swamp hickory, and broom hickory. The pear-shaped nut ripens in September and October and is an important part of the diet of many wild animals. The wood is used for a variety of products, including fuel for home heating.
The range of pignut hickory covers nearly all of eastern United States (11). The species grows in central Florida and westward through Louisiana and along the Gulf Coast to Alabama through Mississippi. It extends through parts of East Texas to Louisiana, Arkansas, Missouri and extreme southeastern Iowa. Its range further includes Massachusetts and the southwest corner of New Hampshire westward through southern Vermont to central Lower Peninsula of Michigan and Illinois.
The best development of this species is in the lower Ohio River Basin. It prevails over other species of hickory in the Appalachian forests. Pignut makes up much of the hickory harvested in Kentucky, West Virginia, the Cumberland Mountains of Tennessee, and the hill country of the Ohio Valley.
Pignut Hickory is also found in Canada in southern Ontario. It does however have a limited range and is restricted to the Niagara Peninsula, southern Halton Region, the Hamilton area along western Lake Ontario, and southward along the northern shore of Lake Erie and pockets of extreme southwestern Ontario.
Pignut hickory grows in a humid climate with an average annual precipitation of 760 to 2,030 mm (30 to 80 in) of which 510 to 1,020 mm (20 to 40 in) is rain during the growing season. Average snowfall varies from little to none in the South to 2,540 mm (100 in) or more in the mountains of West Virginia, southeastern New York, and southern Vermont (25).
Within the range of pignut hickory, average annual temperatures vary from 7 °C (45 °F) in the north to 21 °C (70 °F) in Florida. Average January temperature varies from -4° to 16 °C (25° to 60 °F) and average July temperature varies from 21° to 27 °C (70° to 80 °F). Extremes of 46° and -30 °C (115° and -22 °F) have been recorded within the range. The growing season varies by latitude and elevation from 140 to 300 days.
Mean annual relative humidity ranges from 70 to 80 percent with small monthly differences; daytime relative humidity often falls below 50% while nighttime humidity approaches 100%.
Mean annual hours of sunshine range from 2,200 to 3,000. Average January sunshine varies from 100 to 200 hours, and July sunshine from 260 to 340 hours. Mean daily solar radiation ranges from 12.57 to 18.86 million J m± (300 to 450 langleys). In January daily radiation varies from 6.28 to 12.57 million J m± (150 to 300 langleys), and in July from 20.95 to 23.04 million J m± (500 to 550 langleys).
According to one classification of climate (20), the range of pignut hickory south of the Ohio River, except for a small area in Florida, is designated as humid, mesothermal. That part of the range lying north of the Ohio River is designated humid, mesothermal. Part of the species range in peninsular Florida is classed as subhumid, mesothermal. Mountains in Pennsylvania, West Virginia, North Carolina, and Tennessee are classed as wet, microthermal, and mountains in South Carolina and Georgia are classed as wet, mesothermal. Throughout its range, precipitation is rated adequate during all seasons.
Soils and topography
Pignut hickory frequently grows on dry ridgetops and sideslopes throughout its range but it is also common on moist sites, particularly in the mountains and Piedmont. In the Great Smoky Mountains pignut hickory has been observed on dry sandy soils at low elevations. Whittaker (27) placed pignut in a submesic class and charted it as ranging up to 1480 m (4,850 ft)-the hickory with the greatest elevational range in the Great Smoky Mountains. In southwest Virginia, south-facing upper slopes from 975 to 1050 m (3,200 to 3,445 ft) of Beanfield Mountain are dominated by pignut hickory, northern red oak Quercus rubra), and white oak (Q. alba). This site is the most xeric habitat on the mountain because of high insolation, 70 percent slopes, and medium- to coarse-textured soils derived from Clinch sandstone. Mid-elevation slopes from 800 to 975 m (2,625 to 3,200 ft) are dominated by chestnut oak (Q. prinus), northern red oak, and pignut hickory and coincide with three shale formations (12).
The range of pignut hickory encompasses 7 orders, 12 suborders, and 22 great groups of soils (24,25). About two-thirds of the species range is dominated by Ultisols, which are low in bases and have subsurface horizons of clay accumulation. They are usually moist but are dry during part of the warm season. Udults is the dominant suborder and Hapludults and Paleudults are the dominant great groups. These soils are derived from a variety of parent materials-sedimentary and metamorphic rocks, glacial till, and in places varying thickness of loess-which vary in age from Precambrian to Quaternary.
A wide range of soil fertility exists as evidenced by soil orders-Alfisols and Mollisols which are medium to high in base saturation to Ultisols which are low in base saturation. Pignut hickory responds to increases in soil nitrogen similarly to American beech (Fagus grandifolia), sugar maple (Acer saccharum), and blackgum (Nyssa sylvatica) . These species are rated as intermediate in nitrogen deficiency tolerance and consequently are able to grow with lower levels of nitrogen than are required by “nitrogen- demanding” white ash (Fraxinus americana), yellow-poplar (Liriodendron tulipifera), and American basswood (Tilia americana). Hickories are considered “soil improvers” because their leaves have a relatively high calcium content.
Hickories provide food to many kinds of wildlife. The nuts are relished by several species of squirrel and represent an estimated 10 to 25 percent of their diet. Nuts and flowers are eaten by the wild turkey and several species of songbirds. Nuts and bark are eaten by black bears, foxes, rabbits, and raccoons. Small mammals eat the nuts and leaves; 5 to 10 percent of the diet of eastern chipmunks is hickory nuts. White-tailed deer occasionally browse hickory leaves, twigs, and nuts.
The kernel of hickory seeds is exceptionally high in crude fat, up to 70 to 80 percent in some species. Crude protein, phosphorus, and calcium contents are generally moderate to low. Crude fiber is very low.
Pignut hickory makes up a small percentage of the biomass in low-quality upland hardwood stands that are prime candidates for clearcutting for chips or fuelwood as the first step toward rehabilitation to more productive stands. Hickory has a relatively high heating value and is used extensively as a home heating fuel.
Pignut hickory is an important shade tree in wooded suburban areas over most of the range but is seldom planted as an ornamental tree because of its size and difficulty of transplanting, although it has spectacular orangey-red fall colors.
(Source: Wikipedia, the free encyclopedia)