A review of native vegetation types in the Black Belt of Mississippi and Alabama, with suggested relationships to the catenas of soil series.
The Black Belt in Mississippi and Alabama is readily defined in terms of its calcareous geology and chalky soils, together with its largely agricultural modern land uses (USFS 2007). Several authors have provided useful studies of this region's vegetation: Hilgard (1860), Mohr (1901), Lowe (1911, 1920), Harper (1913a, 1920, 1943), Myers (1948), Rostlund (1957), Jones and Patton (1966), Rankin and Davis (1971), DeSelm and Murdoch (1993), Brown (2003), Barone (2005a), Barone and Hill (2007), Schotz and Barbour (2009), and others. However, details of the original vegetation have remained somewhat obscure, since so much of the land became agricultural early after colonization. Cotton became dominant economically during the 19th Century, but was partly replaced in the 20th Century by soybeans and corn, especially on lowlands, and by forage and pasture, especially on uplands (Cleland 1920, Wiygul et al. 2003).
The purpose of this paper is to outline the varied native vegetation types within the Black Belt, based on available historical and scientific literature. Given the apparent importance of soil in controlling patterns of vegetation, an effort is made to express the fundamental "catenas" in geological and topographic gradients among soil series, as defined by the US Department of Agriculture. Based on the literature, typical original vegetation is then suggested for each section of the gradients in soils. The paper does not present a definitive analysis, but builds a hypothetical scheme of relationships to be tested with more systematically collected data in the future.
This review was prompted by field work during 2009 at the Pulliam Prairie in Chickasaw County, Mississippi (Campbell & Seymour 2011b, 2011c). Although initial hypotheses were developed mostly at that site, the context here has been extended to the whole Black Belt region. Moreover, similar soils and vegetation occur in other "blacklands" on the Gulf Coastal Plain, from Texas to Georgia (NatureServe 2010). Outside the strictly defined Black Belt on Cretaceous chalks, there are some calcareous soils with remnants of native grassland on Paleocene or lower Eocene parent material, from Tennessee (D. Estes, pers. comm.) to Georgia (Echols 2007, Echols and Zomlefer 2010). Further south, the Jackson Prairie region of Mississippi and Alabama lies on calcareous clays of upper Eocene age, and has much similarity to the Black Belt (Moran et al. 1997, Barone 2005b, Barone and Hill 2007). Although this paper is focused on the Black Belt, it does make some reference to similar vegetation in those other regions (as local 'associations' or 'floristic vicariants'), in order to advance more functional descriptions of broader types that might be applied to blacklands in general (as 'alliances' or 'ecological classes').
OCCURRENCE OF NATIVE GRASSLAND
Barone and Hill (2007) have recently conducted a broad floristic survey of native grassland remnants in the Black Belt and Jackson Prairie regions. The concentration of several conservative or rare grassland plant species in the Black Belt suggests that grassland has existed here for much of the post-glacial era and before. There is also increasing evidence that several populations of animals found in the region are--or were--disjunct from more extensive populations in the Great Plains. These animals include extant insects (e.g., Brown 2003, Hill 2007, Hill and Brown 2010) and extinct horses (Kaye 1974).
However, there has been some controversy about the degree of openness, which may have varied greatly in association with patterns in soils and in the frequency of burning by native people. If the region is broadly defined to include river valleys with alluvial soils, and intermixed ridges with more acid soils, it is estimated that about 10-35% of this whole landscape was truly open grassland or savanna with no more than 10 trees per acre (Harper 1913b, Cleland 1920, Jones and Patton 1966, Rankin and Davis 1971, Barone 2005a). But these openings were concentrated on about 70-75% of the more calcareous uplands where typical soil pH is about 6.5-8.5. Much other land across the whole region probably had woods with some degree of opening caused by fires or other disturbances, and about 10-40% appears to have been completely closed forest. Before European settlement, adjacent regions generally appear to have had less grassland than the Black Belt, but the woods in some of these regions were probably much influenced by fire (Rostlund 1957, Brewer 2001, Peacock et al. 2008).
When Europeans first entered the Black Belt in 1540, there were significant concentrations of native people, who provided the first serious resistance to De Soto's expedition in North America (Clayton et al. 1993). During 1500-1760, the Alabama and other tribes were based in central Alabama, numbering several thousand (Hook 1997; see also, www.ac-tribe.com/ac). The Choctaw were centered in western Alabama and east-central Mississippi, with several villages in the Black Belt, as described in accounts cited by Rostlund (1957). Further north, the Chickasaw tribe was centered in northwestern Alabama, northeastern Mississippi, western Tennessee, and southwestern Kentucky, numbering about 10,000-15,000 (Nairne 1708, Morgan 1996, Sultzman 1999, Johnson 2000, O'Brien 2003). In Mississippi, there was a relatively dense concentration of people along the Tombigbee River and its tributaries from near Columbus to Tupelo. Many villages existed in this region, usually on the low bluffs ('cuestas') along the western or southwestern side of these streams, often adjacent to openings on the chalky slopes and overlooking lowland plains with the most productive fields (B. Lieb, personal communication from The Chickasaw Nation; Peacock and Miller 1990). The land of the Chickasaw was even "better provided with these plains than the Choctaw country, the landscape more beautiful, and the soil better" (Anonomous source, ca 1755; cited by Rostlund 1957).
As described by Nairne (1708) and other early authors (see above), these native people used much lowland to grow corn and other crops, including nuts and fruits from various trees and shrubs. Based on Rostlund's (1957) review, it is likely that some of these lower open areas--often described as "fields" or "savannas"--were burned on a rotation. His historical sources also suggest that native people burned adjacent uplands in the region, as well, in order to increase production of game and other wild food. Burning may well have caused grassy openings to spread up from the thinner chalky soils. Bison were hunted in the Black Belt region about the time of European conquest, and may have increased in numbers when native human populations declined (Johnson et al. 1994).
After Spanish invasion, subsequent colonization and removal of the tribes, the Black Belt became increasingly used for intensive farming, with cotton becoming the major exported 'cash-crop' (Cleland 1920, Gibson 1941). Burning of native vegetation became greatly reduced. Good stable remnants of native grassland--or grassy open woodland--became virtually restricted to a few upland areas with relatively shallow, erodible or otherwise unproductive soils.
GEOLOGY, TOPOGRAPHY AND SOILS
The Black Belt is largely underlain by Upper Cretaceous sediments that are generally known as the Selma Group, of which the Demopolis Chalk is predominant. The Demopolis is composed of "chalk and marly chalk containing fewer impurities than underlying and overlying formations" (Moore 1985). [Chalk is limestone of calcite, i.e. CaCO3 deposited by unicellular haplophyte algae; marl is mudstone of clay and much aragonite, i.e. CaCO3 deposited by molluscs, corals and other animals.] Overlying the Demopolis Chalk are varied sediments of the Cretaceous-Tertiary transition, which are either included in the Selma Group or segregated as the Midway Group. This transition includes the Ripley Formation, which forms the Pontotoc Ridge--a more sandy physiographic strip along the western side of the Black Belt in Mississippi. The Ripley is composed of "gray to greenish-grey fine glauconitic sand, clay and sandy limestone" (Moore 1985). [Glauconite is iron silicate plus minor amounts of other minerals.] Underlying the Demopolis Chalk is the Mooreville Chalk of the Selma Group, and below that is the Eutaw Formation, which is a glauconitic sandstone of the Tuscaloosa Group.
The USDA (2010a,b) has provided detailed descriptions of soil series, regional maps and maps for each county. Relationships of soil series to topography and geology are often summarized with diagrams in the published soil surveys. From a detailed review of this material, it is possible to construct a two-dimensional diagram that displays 'catenas' of soils (i.e., sequences along gradients that sort out attributes) among typical series reported from the Black Belt (Fig. 1). This diagram was arrived at through successive approximation, the organizing goal being to place the most similar soil series closest to each other; for an earlier application of the method, see Campbell and Grubbs (1992). Overall similarity was judged subjectively based on parent material, texture, landscape position, slope, depth, drainage, acidity, and color (see Supplementary Material for overlays of individual attributes).
The vertical dimension in Fig. 1 displays the elevation-related gradient, from alluvial lowlands, to the chalky soils on gentle side slopes, to the overlying clays and sands on broader ridges. The horizontal dimension displays the drainage-related gradient, from well drained slopes with generally shallower soils above parent material (left), to poorly drained flats with generally deeper soils (right). Some of the poorly drained soils have 'xerohydric' character, with great fluctuations in water table through the seasons. For example, the Trebloc soil series, on upland flats (at upper right in Fig. 1), is known to experience particularly wide fluctuations (Pettry et al. 1995).
Soil series on chalk are mostly classed as various vertisols (Fig. 1)--with expansive 'shrink-swell' clays (Pettry and Switzer 1993), and 'self-mulching' of organic matter into deep A horizons. Similar vertisols (as chromic hapluderts) have been detailed in the Jackson Prairie by Moran et al. (1997). More local soil classes include entisols (especially on more recent colluvium/alluvium), inceptisols (especially on deep/damp colluvium/alluvium), mollisols (often with more stable grass, cane or cedar cover), and alfisols (on more weathered loamy uplands with more woodland history just above the chalk). In contrast, loamy ultisols (with generally less base saturation) predominate above the chalky soils, on more sandy uplands or on high terraces, usually with a history of more woodland than grassland.
Uplands in the Black Belt, as in some other blacklands (e.g. Moran et al. 1997), are prone to severe sheet and gully erosion, even on gentle slopes. Natural erosion is already a widespread feature of chalky soils in the region, but land clearance and farming have caused substantial increases. The valley floor of Sakatonchee Creek in Chickasaw County, Mississippi, appears to have risen by 10-20 feet within the past century, based on observations at bridges (S. Pulliam, pers. comm.). Similar observations have been made across northcentral Mississippi (Grissenger et al. 1982). Adair (1775; p. 358, 413), Harper (1913a), Gibson (1941) and several other early geographers pointed out that erosion often exceeds weathering on uplands in the Black Belt, leaving a thin layer of clayey soil or disintegrating chalk--or 'rotten limestone'--above more consolidated parent material. However, erosion appears to be retarded where there are remnants of thicker acid clays on ridges, often associated with post oak and other trees.
NATIVE VEGETATION TYPES Based on available literature, the following vegetation types can be broadly defined, with potential segregates indicated in several cases. These types are ordered here with an informal letter code--(a) to (o)--that is used for cross-reference to an accompanying paper (Campbell and Seymour 2011b). Numbers in parentheses after "NVC" refer to the "CEGL" codes for the most similar vegetation types in the National Vegetation Classification of NatureServe (2010). Botanical nomenclature primarily follows the list of vascular flora in Mississippi that is being developed at the Pullen Herbarium in Oxford (McCook and Kartesz 2010), based initially on Kartesz (1999).
Uplands with Acid Soils Overlying Calcareous Sediments. These diverse soils have varied components of clay, silt or sand, occuring on uplands within the Black Belt and in transitions to the Pontotoc Ridge or other adjacent uplands. Subsoils have red, brown, yellow or gray hues.
(a) Oak woods on ridges and knolls (NVC 7246, 2075). Several observers have indicated the historical place of such woods in the landscape. In addition to the locally wet "flatwoods" with much post oak that were extensive just outside the western and southern borders of the Black Belt (Mohr 1901, Lowe 1921), there were more fragmented oak woods on uplands scattered within much of the region. For example, in the northern Black Belt, Nairne (1708, p. 36-39) described traveling "up and down the savannas ... among a tuft of oaks on a rising knowll, in the midst of a large grassy plain." M. McGee (1841, p. 60 in Atkinson, 2004) recalled "Old Fields" ca. 1750-70 in the Tupelo area, from "Old Town" towards "Long Town" and "Post Oak Town"--these fields were "some 13 or 14 miles long by about 4 broad, with here & there a copse of wood to dot the wide & long extended expanse." In the western transition, Ward (1987) used details of the 1834 survey to map islands of post oak within the prairie, just above sites of human occupation. Hilgard (1860) provided several notes of such oak woods, and Harper (1913a) generally noted "oak groves on broad low knolls of poorer soils."
There has been little botanical description of these oak woods. In Mississippi, Lowe (1921) noted: "On the lighter and usually higher [yellowish-brown to] reddish soil areas which dot the prairie surface like islands, an entirely different assemblage occurs. The soil is not so rich in plant food as the black soils, lime especially being in much smaller proportions. These areas support a rather dwarfish growth of a few species of trees, chiefly oaks, the commonest being ..." [with modern names] chiefly Quercus stellata, Q. marilandica and Q. falcata; also present, Q. velutina, Q. durandii Buckl. (= Q. sinuata auct.), Carya tomentosa, Diospyros virginiana, Pinus echinata, Prunus serotina and Rosa carolina. He noted more distinct flora in the red sandy hills that intermix with the Black Belt, on soils typical of the Pontotoc Ridge and plains further west, adding Liquidambar stryraciflua, Sassafras albidum, Rhus spp., Vaccinium arboreum and Vitis rotundifolia.
In Alabama, Bartram's (1791) early account of the "expansive illuminated plains" south of Montgomery is insightful: "They are invested by high forests, extensive points or promontories, which project into the plains on each side, dividing them into many vast fields opening on either side as we passed along." Hawkins (1798-99) also described these plains: "They are waving, hill and dale, and appear divided into fields. In the fields the grass is short, no brush; the soil in places is a lead color, yellow underneath, and very stiff [suggesting the dystrudert series, Vaiden, in Fig. 1]. In the wooded parts the growth is generally post oak, and very large, without any underbrush, beautifully set in clumps. Here the soil is dark clay, covered with long grass and weeds, which indicates a rich soil ..." [suggesting the more alfic Brooksville or Kipling soil series]. Mohr (1901) and earlier authors (Romans 1775, Darby 1818; W. Roberts 1818, quoted in Rostlund, 1957) described oak woods in Alabama similar to Lowe's (1921), adding other species of Carya (glabra, ?ovata), dogwood (Cornus florida), ironwood (?Ostrya) and, locally, poplar (Liriodendron) to the list of typical trees. Mohr also detailed the poorly drained condition in some areas, with distinctive grasses, diverse sedges and allies in Carex, Cyperus, Eleocharis and Scleria; the latter appears to have been locally abundant in drier transitions. On drier ground, legumes were relatively common: Desmodium spp., Lespedeza spp., and "Japanese clover" [Kummerovia striata].
Today, post oak is generally dominant in older woods on uplands, and large open-grown post oaks are frequently left around old home sites for shade, or along old surveyed boundaries. Hill et al. (2009) surveyed a hectare of woods adjacent to the Osborn Prairie in Oktibbeha County, Mississippi. These woods were dominated by post oak and red cedar (Juniperus virginiana), plus scattered loblolly pines ca. 30-60 years old. Other trees included oaks (Quercus: marilandica, durandii, falcata, velutina, alba), hickories (Carya: ovata, myristicaeformis, tomentosa), white ash (Fraxinus americana) and winged elm (Ulmus alata). Ground vegetation contained common shade tolerant species, with none characteristic of grassland.
(b) More open woods with local blackjack oak (b1) or shortleaf pine (b2), plus associated thickets and glades (NVC 4053, 3952--or 4670 on more calcareous soils). As emphasized by Rostlund (1957)--but perhaps overemphasized--before the 1830s, there are indications of open woods with grassy conditions at many localities in regions with acid soils adjacent to, or intermixed with, the Black Belt grasslands on chalk. He suggested that frequent fires were involved in maintaining these areas, and that the Black Belt itself was not much more open.
On plains west of the Black Belt in Mississippi, a regional increase in pine began about 2400 years ago, which is attributable to promotion of fires by people (Whitehead and Sheehan 1985). Based on early surveys, fire-tolerant oaks and pines were generally more abundant in upland woods of north-central Mississippi during the 1830s than they are in woods today, but patterns varied much in space and time (Brewer 2001, Peacock et al. 2008, Surrette et al. 2008). The pyrophile, blackjack oak (Quercus marilandica--probably including much "black oak"), was locally dominant then, but it has now greatly declined. Pines--shortleaf (Pinus echinata) or loblolly (P. taeda)--were more frequent than blackjack oak locally, especially on lower slopes with more sandy soils, where fire regimes may have been somewhat less intense or less frequent. Today, shortleaf pine remains one of the most common trees in mature woods on drier sites of north-central Mississippi, but white oak (Q. alba) predominates on more mesic uplands, often with much southern red oak (Q. falcata) and hickories. Also, the highly fire-sensitive sweetgum (Liquidambar) has generally increased, spreading from lowlands onto uplands.
Within the Black Belt, we have few historical details of patterns in the degree of openness, but blackjack oak appears to have been locally abundant, at least in Mississippi. A relevant note on the Tupelo area comes from Nutt (1805; p. 43 in Jennings, 1947): "The country around Big Town for many miles affords good farming land. Many prairies, no running water near the town ... [But] The country between Big Town & ... 20 mile creek [main branch of Tombigbee to the east] ... is poor broken black-jack land. No running water. On the creek is fine cane, the bottom subject to overflow in spring season ... the branches of this creek interlock with the head of Tal,la,hat,chee [of Yazoo River to the west, and] is high broken land very little fit for cultivation." From Pontotoc to Chickasaw County, Hilgard (1860, p. 91 and 100) noted "ridges characterized by an excessively heavy soil, bearing the Black Jack Oak, and popularly termed "beeswax hommocks" ... [on] gray calcareous clay which frequently overlies the limestone and calcareous sand" [perhaps matching the hapludert, Houston, in Fig. 1].
Pines were virtually absent within the Black Belt of Mississippi before modern planting programs, which concentrated on loblolly pine. Shortleaf pine was locally frequent only on the more acid soils in adjacent western regions, including Pontotoc Ridge and the Post-oak Flatwoods (Harper 1913a, Brewer 2001, Peacock et al. 2008, Surrette et al. 2008). But in Alabama, pines--mostly shortleaf--formed ca. 5-9% of witness trees across the whole Black Belt in 1830-50 (Jones and Patton 1966, Rankin and Davis 1971). Especially in the relatively hilly sections of eastern Alabama, there is more intermixing of geological and topographic features, and marly soils predominate rather than pure chalk. This mix was reflected in a more intimate combination of shortleaf pine or other pines with hardwoods typical of the Black Belt (Mohr 1901, Harper 1913b). Some remnants of grassland in Alabama today are surrounded by pine-oak woods (Schuster and McDaniel 1973, Schotz and Barbour 2009).
(c) Upland prairies on somewhat acid soils; (c1) xeric-tending or (c2) locally xerohydric (with potential affinity to NVC 2242, 2405 and 5057). It is likely that the chalk prairies often graded into less calcareous grassland on adjacent uplands. Extensive prairies on relatively acid soils were not well documented in early botanical literature. But, traveling south across Pontotoc County into the Black Belt of Mississippi, Hilgard (1860, p. 79-81) noted: "... on the Connewar, Chiwapa and Tallabinella [Creeks], the regular prairies set in, with their 6 to 10 foot stratum of yellow clay overlying the Rotten Limestone"; see also the quotation from Hawkins under (a) above. Hilgard noted that these "larger bodies of prairie" extended east from the "Orange Sand" at the base of the Ripley Formation to cover the broad "dividing plateau" of major streams within the Black Belt, including the "Mayhew Prairie" below Palo Alto. They were interspersed with "greatly inferior" soils on residual uplands, presumably including more sandy ultisiols (as in upper rows of Fig. 1). His description of the "12 to 18 inches" of "black prairie soil" above (2) 5-7 (10) feet of "pale yellow clay containing small round ferruginous concretions" suggests dystrudert soils such as the series Oktibbeha and Vaiden (Fig. 1). He contrasted this general upland prairie with the "small prairies" or "bald prairie spots" at lower stratigraphic levels where chalk was much closer to the surface, especially "on the [eastern] outskirts, in these wooded portions, and on the streams, not in the prairie proper."
More open oak woods and edges on transitional uplands do contain diverse sun-loving species that could have been promoted by fires before De Soto, as well as by xeric or xerohydric conditions at some sites. In Mississippi, Lowe (1921) listed the following sun-loving plants as characteristic of more acid uplands around the Black Belt [converted here to modern names]: Apocynum cannabinum, Ceanothus americanus, Gamochaeta purpurea, Krigia virginica, Oenothera sp., Orebexilum sp., Opuntia sp., Penstemon laevigatus, Phlox pilosa, Plantago aristata, Schrankia microphylla, Stylosanthes biflora, Tephrosia virginiana, Triodanis perfoliata, and Verbena sp. S. Brewer (personal communication) is currently investigating the extent to which suppressed populations of sun-loving plants, in general, can be increased with fire in seasonally dry woodlands of north-central Mississippi. He has found strong reponses by several legumes (Fabaceae), Dichanthelium spp. (Poaceae), and, especially in thinned woods, Helianthus spp. and allies (in Asteraceae). Less common potential increasers with fire in this region include Aletris aurea, Aureolaria pectinata, Eryngium yuccifolium, Eurybia hemispherica, Gentiana villosa, Gratiola pilosa, Helianthus silphioides, Liatris squarrulosa, Matelea carolinensis, Phlox pilosa, Piptochaetium avenaceum, Polygala cruciata, Pogonia ophioglossoides, Sabatia campanulata, Silphium integrifolium and Xyris jupicai (Denley et al. 2002).
In Alabama, varied accounts suggest that thin woods on uplands have often graded into prairies, which sometimes occurred in small patches or on transitional soils from sandy to calcareous. Gosse (1859, p. 82) reported contemporary usage of the term "forest prairie" for the vegetation he found on a "little knoll" within denser woods. Mohr (1901) described much of the general upland vegetation south of the Black Belt as "post oak prairies"--a term also used around the Jackson Prairies by Hilgard (1860) and others (Moran et al. 1997). Open post oak woods are known today across southeastern states, often with seasonal extremes of wetness and dryness that promote extensive graminoid ground vegetation and some shrubby openings (as in NVC 5057 and 2405). Mohr also noted that "sand hills near Montgomery" had openings with several distinctive xerophile or annual grasses (Aristida, Eragrostis, Panicum) and herbs, including Brickellia eupatorioides, Croptilon divaricatum, Mirabilis sp. ("hirsuta"), Symphyotricum spp. ("patens" and "undulates"), and Tragia urticifolia (cf. NVC 2242). There were some frequent acidophiles in Harper's (1920) prairie, e.g. Polygala grandiflora, and in the three-acre glade within pine-oak woods studied by Schuster and McDaniel (1973), e.g. Hypoxis hirsuta and Schoenolirion croceum. In some of the grasslands surveyed by Schotz and Barbour (2009), such as the Cahaba River Prairies, several of the reported common plants are more typical of acid or sandy soils, rather than purely calcareous, e.g., Agalinis tenuifolia, Aristida virgata, Desmodium marilandicum, Liatris squarrulosa, Physalis carpenteri and Sporobolus junceus.
Uplands with Calcareous Soils. In the National Vegetation Classification (NatureServe 2010), calcareous grassland and associated vegetation on the southeastern Coastal Plain is treated in a few broadly defined alliances that reflect the general gradient from xeric, open conditions to more mesic, shady conditions. However, at moderate scales of ca. 1-10 acres [0.4-4 ha], there is usually much intermixing of the grassland types outlined below (d, e, f and g), which are often partly or completely combined in published descriptions.
(d) Upland prairie on xeric-tending (d1) or locally xerohydric (d2) sites. At dry open extremes on shallow, eroding or disturbed soils, there is mid-sized to short grassland, locally dominated by annuals and usually mixed with patches of bare ground that has relatively little organic matter (Schauwecker 1996). In poorly drained swales, there can be extremes of both wetness and dryness, with particularly unstable and relatively bare soil surfaces. This type of grassland occurs locally in much of the Black Belt on or near outcrops of chalk (Harper 1920, Schuster and McDaniel 1973, Morris et al. 1993, Leidolf and McDaniel 1998), and similar vegetation has been described in other blacklands (e.g., Echols and Zomlefer 2010). NatureServe (2010) has defined a variant of such vegetation from the Cook Mountain Prairie of Louisiana (NVC 4021) that could be extended and applied to much of the Black Belt: Schizachyrium scoparium-Panicum flexile-Carex microdonta. But at the Pulliam Prairie (our personal observations) and at some other sites in the northern Black Belt (C. Bryson, personal communication), Carex crawei largely replaces C. microdonta.
Other characteristic graminoids in such vegetation include Aristida spp. (longespica, oligantha, purpurascens), Bouteloua curtipendula, Fimbristylis puberula and Sporobolus spp.--vaginiflorus (on bare ground), clandestinus (in less xeric transitions) or compositus (locally on deeper soils). Typical herbs include Asclepias viridiflora, Coreopsis lanceolata, Croton monanthogynus, Dalea candida, Erigeron strigosus, Euphorbia corollata, Heliotropum tenellum, Heterotheca camporum, Houstonia nigricans, Hypericum sphaerocarpon, Liatris squarrosa, Linum sulcatum, Lithospermum canescens, Lobelia spicata, Mirabilis albida, Penstemon tenuiflorus, Solidago nemoralis, Symphyotrichum patens, Silphium laciniatum and Verbena simplex. The number of vascular species in small plots tends to be relatively low: ca. 5-15 per 0.25 [m.sup.2] (Weiher et al. 2004). However, composition varies greatly across larger plots, in relation to local topography, erosional patterns, and broad intergradation with the taller grassland outlined below (types e, f and g).
(e) More disturbed prairie on stressed or eroded sites, often transitional from (d) to (f). Mixing of characteristic species from more xeric sites (type d) and less xeric sites (type f) has probably been enhanced where soils are disturbed by grazing, mowing or plowing. Many remnants today are in various stages of recovery from farming, especially on deeper soils of lower ground that receives or holds more moisture. Several authors have noted that disturbance has led to local abundance of more weedy native species plus more frequent aliens (Mohr 1901, Harper 1913, Harper 1920, Leidolf and McDaniel 1998, Echols and Zomlefer 2010, NatureServe 2010).
Commonly reported grasses in these sources are Andropogon spp.--virginicus on drier sites (most/all as var. decipiens), or "glomeratus" on damper sites (most/all as var. pumilus = A. tenuispatheus). A. glomeratus was used by NatureServe in earlier names for some regional variants. Other locally common native grasses that are relatively tolerant of disturbance include Panicum anceps, Muhlenbergia capillaris, Paspalum floridanum and Setaria parviflora. Characteristic herbs include relatively weedy natives, such as Ambrosia spp., Cuphea viscosissima, Erigeron spp., Prunella vulgaris var. lanceolata, Sabatia angularis, and Symphyotrichum pilosum. Aliens are locally common, including the rather short but rapidly spreading grasses, Bromus japonicus, Digitaria ischaemum, Paspalum dilatatum (formerly planted for forage) and Sporobolus indicus, as well as taller species that often extend into less frequently stressed or disturbed sites (see f).
(f) Upland prairie on average sites; generally subxeric. This mid-sized to tall grassland appears to have been the most widespread type in blackland prairies of southeastern states. NatureServe (2010) and others have described regional variants from the Black Belt of Tennessee, Mississippi and Alabama (NVC 4664; see also, Schotz and Barbour 2009), the Grand Prairie of Arkansas (NVC 7769), the Jackson Prairie of Mississippi and Alabama (NVC 4020), the Jackson Prairie west of Louisiana (NVC 4721), and the prairies on lower Eocene clays in Alabama (Harper 1920) and Georgia (NVC 4247; see also, Echols and Zomlefer 2010). Among the most widespread and locally abundant species are Schizachyrium scoparium (except in Georgia), Sorghastrum nutans, Panicum virgatum and Ratibida pinnata. Species that are less generally abundant but still typical of better remnants within the Black Belt, include Dalea spp. (candida, purpurea), Liatris spp. (aspera, spicata, squarrosa), and Silphium spp. (integrifolium, laciniatum, terebinthinaceum).
Historical sources support this general description of the prevailing grassland on uplands (Bartram 1791, Mohr 1901, Harper 1913a, Lowe 1921). From Harper's transects of the region, he noted: "The comparatively large numbers of herbs, and the occurrence of a few genuine prairie species, such as Ambrosia bidentata, Silphium laciniatum, S. terebinthicaceum, Mesadenia tuberosa [= Cacalia or Arnoglossum plantagineum], and Polytaenia nuttallii (the last three seen only once, and therefore not listed), are reminders of the prairie conditions that once existed in this region." Several early, colorful accounts also indicate that wild strawberries (Fragaria virginiana) were locally abundant in the prairie, presumably proliferating after burning, grazing, cropping or other disturbance (e.g., De Montigny 1736, quoted in Rostlund, 1957; Romans 1775, Bartram 1791).
Other typical species can be inferred from Mohr (1901), Lowe (1921), DeSelm and Murdoch (1993), Schauwecker (1996), Leidolf and McDaniel (1998), NatureServe (2010), Schotz and Barbour (2009) and others, though taxonomy remains uncertain in some cases. These include Agalinis spp. (auriculata, oligophylla, purpurea), Asclepias spp. (tuberosa, viridis, verticillata), Blephilia ciliata, Buchnera americana, Coreopsis spp. (lanceolata, grandiflora), Desmanthus illinoensis, Desmodium spp. (especially ciliare), Dracopsis amplexicaulis, Eupatorium spp. (altissimum, serotinum), Helianthus spp. (especially hirsutus), Lythrum alatum (perhaps all as var. lanceolatum), Neptunia lutea, Oenothera spp. (biennis, speciosa, triloba), Rudbeckia spp. (hirta, laciniata, triloba), Sabatia angularis, Sisyrinchium albidum, Solidago spp. (especially nemoralis), Spiranthes magnicamporum, Sporobolus compositus (perhaps all as var. drummondii), Symphyotrichum spp. (dumosum, ericoides, patens), and Verbena spp. (angustifolia, canadensis, ?hastata). The number of species in small plots tends to be relatively high: ca. 10-20 in 0.25 m2 (Weiher et al. 2004).
Although there are many small remnants of the original grassland covering ca. 1-10 acre [0.4-4 ha], larger remnants are rare. NatureServe (2010; with reference to NVC 4664) stated: "Nearly all of this association has been destroyed for agricultural uses, or altered by grazing and fire suppression. No high-quality examples are known." The aliens, Bermuda grass (Cynodon dactylon), Johnson grass (Sorghum halepense), and sweet clovers (especially Melilotus alba), became widely abundant in the region ca. 1850-90, after being introduced for pasture and hay (Gosse 1859, Mohr 1901, Harper 1913a). The highly persistent sericea lespedeza (L. cuneata) has been widely sown to build soils on dry or eroded during 1950-1990. Also, fescue (Festuca arundinacea) has been widely sown for forage in converted grasslands after 1950, though it does not generally invade more intact remnants of drier native grassland. In recent decades, cogon grass (Imperata cylindrica) has become another serious alien threat to this grassland and other types, especially in seasonally damp swales.
(g) More mesic (g1) or hydric (g2) prairie. These variants can include more tall grasses, especially (in g1) big bluestem (Andropogon gerardii) and locally (in g2) gamagrass (Tripsacum dactyloides). Also, there are more tall herbs--notably Symphyotricum novae-angliae--and more marginal wetland species--notably Lythrum alatum on "seepy inclusions" (NatureServe 2010; within NVC 4664). Although A. gerardii is now rare to absent in most remnants, it was probably much more common in the original vegetation before agricultural conversions, especially where there was frequent burning that reduced woody thickets on lower slopes (Mohr 1901, Leidolf and McDaniel 1998, Hill and Seltzer 2007, Echols and Zomlefer 2010). Even without woody encroachment, Johnson grass (Sorghum halapense) and other aggressive aliens can preempt habitat for taller native grassland. In more shady transitions to riparian thickets and woods, there are several characteristic cool-season grasses. Mohr (1901) listed Elymus [glabriflorus, virginicus], Bromus [pubescens] and Chasmanthium [latifolium, sessilifolium] for "sheltered borders" [using suggested modern names instead of his usage]. Sedges and allies (Cyperaceae) are also locally abundant on wetter sites.
Good examples of such vegetation appear to be rare, and almost no sites have been described in detail. In Mississippi, Hill and Seltzer (2007) recently added Andropogon gerardii and Tripsacum dactyloides to the list for a relatively well known site--the Osborn Prairie of Oktibbeha County. In Alabama, Schotz and Barbour (2009) listed A. gerardii as a common species at only one of their ten best sites for Black Belt prairie in the state--Pleasant Ridge in Greene County--and they did not list Tripsacum at any site. Species that were originally associated with A. gerardii are difficult to discern from the literature, and remnants of their populations may often be suppressed in nonflowering condition by encroaching woods. Based on general knowledge, these species probably included some that are now inconsistently documented or rare in the region, e.g., Agalinis auriculata, Desmodium ochroleucum, Echinacea purpurea, Prenanthes aspera, Silphium integrifolium (or perhaps S. glabrum in more brushy transitions), Solidago rigida (especially var. rigida), and Veronicastrum virginicum.
(h) Upland thickets, often in drier (h1) or damper (h2) transitions to woods. Shrubby transitions to upland or riparian woods often have distinctive species that are not typical of open grassland or deeper woods. More thorny variants were probably associated with larger herbivores before human interferences (Kaye 1974). Distinctive examples of such vegetation are still widely scattered but generally restricted to small patches, narrow strips, or truncated woodland edges. There is only one variant that has been described by NatureServe (2010) from the blacklands of southeastern states, in the Cook Mountain Prairie of Louisiana (NVC 3879): Crataegus spathulata-Cornus drummondii-Berchemia scandens. Similar vegetation does occur in the Black Belt of Mississippi and Alabama (Leidolf and McDaniel 1998; Schotz and Barbour 2009; NatureServe 2010, as part of NVC 4664). Thickets in the blacklands of central Georgia can be included for a broader definition, with Cornus asperifolia Michx. instead of C. drummondii, and with Celtis tenuifolia Nutt. instead of C. laevigata (Echols and Zomlefer 2010).
There are several historical indications of shrubby bands along edges of upland oak woods and in riparian zones, plus "isolated baskets" or "scattered clumps" mixed with the prairies, fields or villages. Sources extend from diaries of the De Soto expedition in 1540 (Rostlund 1957, Clayton et al. 1993) to Nairne (1708), Bartram (1791), Jones (1833), Gosse (1859), Hilgard (1860), Mohr (1901), Harper (1913a,b) and Lowe (1921). Nairne (p. 57) noted: "on the Top of these knolls live the Chikcasaws, their houses ... with their ... plum trees about them." In the abandoned Chickasaw Old Fields, Jones noted "small ... cottonwoods, persimmon, bushes, wild plum, briers, and grass." In Dallas County, Alabama, Gosse did not list cedar anywhere, but reported from the prairies that "Several species of Thorn (Crataegus) grow in impenetrable thickets or in single bushes over their surface, and one or two kinds of wild plum, bearing a harsh sour sloe or bullace, are often mixed with them" (p. 75). Similar notes of "crabapple thickets", "haws" and "plum" come from early descriptions of the Jackson Prairie (Moran et al. 1997).
In general, these thickets originally had much Rosaceae, with plums (Prunus angustifolia, P. umbellata), hawthorns (especially Crataegus engelmannii; see also, Mohr 1901), or crab-apples probably Malus angustifolia). Other locally common thicket-forming species are indicated by pre-1950 accounts (especially *) or by more modern observations (especially #): Berchemia scandens#, Celtis laevigata*, Cercis canadensis#, Cornus (drummondii#, florida*), Diospyros virginiana*, Frangula caroliniana#, Gleditsia triacanthos*, Ilex decidua*, Juniperus virginiana#, Maclura pomifera#, Ptelea trifoliata, Rhus spp. (aromatica, copallina, glabra)#, Sideroxylon (lanuginosum, lycioides)#, Ulmus alata# and Vitis spp. (including rotundifolia* on more acid soils). Some species of such vegetation are now rare, at least within the region, notably Crataegus ashei, C. triflora and Rhamnus lanceolata (Schotz and Barbour 2009).
(i) Red cedar woods. Red cedar (Juniperus virginiana) appears to have been uncommon or rare in the Black Belt of Mississippi before De Soto (Peacock and Miller 1990). In 1832, it made up only ca. 0.3% of the recorded trees across the Black Belt of Sumter County, Alabama (Jones and Patton 1966). Mohr (1901) noted "cedar hammocks" in Alabama "on the highest swells of the plain where the strata of the rotten limestone are overlaid by lighter loams." In the Black Belt of Mississippi, Lowe (1913, 1920) reported red cedar only from ledges where limestone comes to the surface or as scattered clumps in low or wet areas. Harper (1913a) noted red cedar only once in Mississippi, though he stated: "It is rather common in the black belt of Alabama."
Red cedar has now become locally dominant in woods and thickets on calcareous soils at various elevations. Older stands tend to occur on drier bluffs and ridges adjacent to chalk outcrops, sometimes with the Ripley Formation nearby at higher elevation (e.g., Morris et al. 1993, Leidolf and McDaniel 1998, Hill et al. 2009). In addition to direct colonization of old fields, red cedar can invade thickets of the species noted in the previous section (h), along with sugarberry (Celtis laevigata), ashes (F. americana), scattered oaks (especially Q. muhlenbergii), and other trees. NatureServe (2010) has outlined a generalized type (NVC 7747): Juniperus virginiana-(Celtis laevigata, Prunus angustifolia, Sideroxylon lycioides). Similar woods have been well-documented in other blacklands, from Louisiana (Bekele et al. 2006; together with species of Crataegus, Diospyros and Berchemia) to Georgia (Echols and Zomlefer 2010; where Celtis tenuifolia often occurs instead of C. laevigata). Schauwecker (1996, 2001; see also Weiher et al., 2004) has shown that succession to red cedar causes ground cover to decline abruptly in biomass and richness, usually leading to a few relatively common shade-tolerant species. However, more sun-loving species can prosper locally in thinner woods, including the vine, Berchemia scandens, the sedge, Carex cherokeensis, and the alien legume, Lespedeza cuneata, which often persists from plantings in old fields.
The research of Schauwecker (2001), Weiher et al (2004) and Bekele et al. (2006) has indicated that, as well as the increase in shade during succession from grassland to cedar to hardwoods, there is increased organic matter in the soil, increased moisture-holding capacity, decreased pH (from ca. 7.5-8.25 to ca. 6.5-7.5), and shifts in the balance of available minerals (especially from Ca to Fe). Also, Hill and Brown (2010) have documented a distinctive group of ant species associated with red cedar in the Black Belt.
(j) Submesic mixed hardwoods. These varied woods occur on relatively moist but well-drained soils, usually in areas protected from disturbance on steeper bluffs or sheltered hillsides, or along streambanks where they grade into the riparian woods of broader floodplains, as outlined below (type m). Such vegetation is widespread in small patches and riparian strips, especially in peripheral parts of the region, but there have only been a few miscellaneous published notes on composition.
At the western side of the Black Belt in Mississippi, Ward (1987) used the 1834 survey to indicate red elm, hickory, ash, walnut and sassafras in groves of trees on lower slopes, along with post oak and blackjack on drier ground. In this same section, Hilgard (1860, p. 84) noted the following trees on hillsides with Paleocene limestone [using modern names]: Quercus velutina, Q. falcata, Carya sp., Liriodendron, Juglans nigra, J. cinerea, Tilia sp., Magnolia cf. pyramidata, and Robinia pseudoacacia; lower in the valley, he noted Platanus, Gleditsia, Prunus and Cercis. At the southern side of the Black Belt in central Alabama, Bartram (1791) noted: "Immediately after leaving the plains we enter the grand high forests. There were stately trees of the Robinea pseudacacia [sic], Telea [Tilia], Morus, Ulmus, Juglans exaltata [perhaps Carya ovata], Juglans nigra, Pyrus coronaria, Cornus Florida, Cercis, &c." In Alabama, some of the "cedar hammocks" described by Mohr (1901) were at least transitional to shrubs (Asimina, Ilex, Forestiera, Zanthoxylum) and hardwood trees: Fraxinus americana, Quercus spp. ("laurifolia" and "texana"), Celtis laevigata, Ulmus americana and Acer floridanum (Chapm.) Pax [= A. barbatum auct.].
More modern descriptions of hardwoods on calcareous soils in or near the Black Belt remain scattered, but somewhat consistent. At the southern side, Harper (1920) listed the commonest trees in "a small wooded valley" adjacent to his prairie: Quercus spp. (muhlenbergii, [shumardii var.] schneckii, stellata), Fraxinus americana, Ulmus alata, Juniperus, Juglans, Liquidambar, Tilia and Liriodendron. At the western side, Morris et al. (1993) listed typical trees of a NE-facing mesic bluff: Quercus spp. (muhlenbergii, shumardii), Carya spp. (carolinae-septentrionalis, myristicaeformis), Fraxinus spp. (americana, pensylvanica), and Ulmus spp. (americana, alata), plus lesser numbers of some mesic, shade tolerant species, Acer floridanum, Aesculus glabra Willd., and Tilia americana (sensu lato). In Alabama, Schotz and Barbour (2009) noted similar woods on slopes below prairies at several sites, with Quercus spp. (alba, muhlenbergii, shumardii), Carya spp. (glabra, carolinae-septentrionalis, myristiciformis), Fraxinus spp. (americana, pensylvanica), Celtis laevigata, Ulmus spp. (alata, rubra) and Pinus taeda. In the blacklands of central Georgia, the woods are somewhat similar, but more varied from damp to dry soils, i.e., with much more Q. nigra in general, locally Q. pagoda on terraces, and much transition to Q. velutina or Pinus taeda on more sandy uplands (Echols and Zomlefer 2010).
There are several, varied types in the National Vegetation Classification that might be partly applied here (NatureServe 2010), but only a few well-described types have been directly linked with blacklands. These include: (1) Quercus stellata-Q. muhlenbergii/Schizachyriumm scoparium-Sorghastrum nutans (NVC 4670), which is a transition to open post oak woodland in the Black Belt; (2) Quercus durandii-Fraxinus americana-Quercus muhlenbergii/Rhus aromatica-Cornus drummondii (NVC 7256), which is a transition to dry thicket described for the Jackson Prairie of Louisiana; and (3) Quercus muhlenbergii/Q. durandii-Cercis canadensis/Viburnum rufidulum/Scleria oligantha, which is mixed with Q. velutina in the blacklands of central Georgia, and grades into Crataegus-Cercis thickets (Echols and Zomlefer 2010). More mesic woods with less oak, as noted by Morris et al. (1993), could be included within the broadly defined Upper East Gulf Coastal Plain type: Acer floridanum-Aesculus glabra-Carya myristicaeformis-Quercus shumardii-Q. muhlenbergii (NVC 4671; see also NVC 7971 of Arkansas).
Lowlands with Alluvial Soils. Distinction from uplands is arbitrary in many areas, especially where topographic relief is slight. Calcareous uplands and toe-slopes contain local colluvium and alluvium along swales and gullies that often lead gradually into the more the extensive--and locally exogenous-- alluvium on terraces along broader valleys. Agriculture tends to be especially intense in these broad transitions.
(k) Lowland prairie or open woodland. Several historical accounts indicate that extensive grasslands ("prairies" or "savannahs") occurred locally on relatively well drained toe-slopes and bottomlands that were occupied and cultivated by native tribes, especially the Chickasaw: Nairne (1708), Atkin (1755, p. 67), Adair (1775, p. 352), Romans (1775, p. 124), Baily (1797, p. 30), Nutt (1805, p. 43), and other sources cited by Barone (2005) and Cook (2010). Atkin's account of the Chickasaw, with only "350 adult men" remaining, provides special insight: "These Indians live in seven Towns, having each a Palisade Fort with a Ditch, in an open rich Champain Plaine about ten Miles in Circumference, accessible only on one side, being almost surrounded by Swamps in a circular manner, about a mile from any running Creek ..." Similar notes came from lowlands along the Alabama River and its tributaries (e.g., D. Taitt 1772, quoted in Rostlund 1957; Bartram 1791, Hawkins 1798-99).
It is likely that gamagrass (Tripsacum dactyloides) was dominant in some of these areas, along with big bluestem (Andropogon gerardii) and other tall grasses, especially on vertisols that start wet in the spring but often dry out and crack during the summer and fall (Myers 1948). Harper (1913a) found that gamagrass was the most common native grass in the Black Belt region of Mississippi, and it was also frequent on lowlands within adjacent regions to the west, i.e., the Pontotoc Ridge on more sandy soils, and the Post-oak Flatwoods on stiff clays.
In early settlement, livestock no doubt concentrated on such land and greatly reduced the palatable taller grasses. In farmland of the northern Black Belt, Romans (1775) stated: "the earth is very nitrous ... this produced a grass of which cattle are so fond as to leave the richest cane brakes for it; and notwithstanding the soil appears barren and burnt up, they thrive to admiration." In the Jackson Prairie region, A.J. Brown (1894; cited by Moran et al. 1997) contrasted two types of grassland: (1) the true "prairie grass" of former "woodland prairie" with post oak, then much converted to cotton on deeper, moister soils [Hilgard's "black prairies"]; and (2) the "upland grass" of drier "shell prairies" that were much less productive for agriculture and becoming scrubby [Hilgard's "bald prairies"]. Regarding (1), he stated: "... of which the cattle were very fond and which was a great milk and fat producer. Most of these grasses have become extinct, or so dwarfed by constant grazing and trampling by stock, as not to be observed as an original grass."
Such vegetation has now become almost all converted to fields for corn, cotton and soybeans, except for the frequent strips of land with gamagrass along rights-of-way and ditches. NatureServe (2010) has outlined a Panicum virgatum-Tripsacum dactyloides type for the Grand Prairie of Arkansas (NVC 4624), but has not yet listed a Tripsacum type for the Black Belt in Mississippi or Alabama. Nevertheless, gamagrass is now widely promoted for native forage and general restoration by the Extension Service of Mississippi State University at Starkville.
(l) Lowland canebrakes and other thickets. Originally, there were extensive canebrakes dominated by Arundinaria gigantea on some lowlands, with the tallest cane on levees close to larger streams and rivers (Hawkins 1798-99; Nutt 1805; W. Roberts in Darby 1818; 1834 survey summarized in Ward, 1987; Lyell 1849; Mohr 1901; and other sources of Rostlund, 1957). Mohr even noted: "So conspicuous was this formation in the western part of the plain that it is called emphatically the "canebrake region"" (see also, Cleland 1920). This vegetation was presumably most widespread on sites that were frequently flooded for short periods, but probably burned less often than the lowland prairies (type k) or associated fields. However, cane was "a delightful range for stock" (Hawkins) and its soil was highly suitable for farming after clearance. Cane declined rapidly to become a minor species in the settled landscape, here (Harper 1913a) and elsewhere in its range (Platt and Brantley 1997).
From these early accounts, it appears that several small or shrubby trees were also locally abundant in thickety transitions between grassland--or cultivated fields--and woodland of various types: including edible grapevines (Vitis spp.), plums (Prunus spp.), pawpaws (Asimina triloba), persimmons (Diospyros virginiana) and mulberries (Morus rubra). NatureServe (2010) has outlined a generic canebrake type (NVC 3836), plus some bottomland forest types with cane that can be applied or modified for the Black Belt region (especially NVC 8429, 2099, 3836).
(m) Riparian woods. From historical to modern sources, mixed hardwood forests of diverse types have often been noted along banks and terraces of streams and rivers within the Black Belt and other nearby blacklands (D. Taitt 1772, quoted by Rostlund 1957; Bartram 1791; Hawkins 1798-99; 1834 survey summarized by Ward 1987; Hilgard 1860, Mohr 1901, Harper 1943, Lowe 1921, Whitehead and Sheehan 1985, Morris et al. 1993, Echols and Zomlefer 2010; NVC 2427, 2431, 7335, 7340, 7353, 7915). Frequent trees have included Acer spp., Aesculus spp., Betula nigra, Carya spp., Celtis laevigata, Fraxinus spp., Gleditsia triacanthos, Juglans nigra, Liquidambar styraciflua, Morus rubra, Nyssa spp., Platanus occidentalis, Populus spp., Prunus serotina, Quercus spp., Salix nigra, Tilia spp. and Ulmus spp. Several shrubs and vines are also common, and there is local intergradation with canebrakes (type l).
Such woods varied much in width, structure and composition depending on the size of streams, hydrology, soil conditions and management. Groves of nut trees and persimmons on low slopes or terraces were noted by some early observers, and may well have been selected by the inhabitants, based on diaries from De Soto's 1539-43 expedition (Clayton et al. 1993), Bartram (1791), and others cited by Rostlund (1957). Along the larger rivers of central Alabama, where alluvium is often sandier, Mohr (1901) added listed Fagus, Liriodendron and Magnolia, and other early observers noted "poplar" [probably L. tulipifera], "laurel" [probably M. grandiflora], "cypress", "bay" and "white cork" (Rostlund 1957).
(n) Wooded swamps, sloughs and ponds. Such vegetation is widely scattered across the region, but there are few extensive remnants in a relatively natural condition (Mohr 1901, Harper 1913b, Whitehead and Sheehan 1985, Leidolf and McDaniel 1998). Before agricultural conversions and excessive hunting, beavers--and even people in some areas--probably formed extensive dams on lowlands of the Black Belt (Ward 1987, Cook 2010). Nairne (1708; p. 47, 50) noted "multitudes of Beavor dams" among the Chickasaw villages. Black willow may have been a typical tree around more open wetlands within the grassland (e.g. Roman 1775; p. 15-16).
Some larger sloughs are distinguished by overcup oak (Quercus lyrata; cf. NVC 2424) or water tupelo (Nyssa aquatica; cf. NVC 2419). However, bald cypress (Taxodium distichum) is largely absent, except locally along larger streams and rivers. Paleoecological studies of an oxbow along the Tombigbee River detected bald cypress only after 1800, and "suggest that the modern vegetation of Nyssa-Taxodium developed very recently ... Increased discharge due to European land clearance may have increased both water level and the length of time that standing water was present in the oxbow sufficiently to permit growth of both cypress and Orontium" (Whitehead and Sheehan 1985).
(o) More open ponds and marshes. These must have existed locally before European settlement, for example around beaver ponds. They do exist in varied contexts today, but generally in rather small patches that tend to escape attention, description and conservation. For example, the valley of Sakatonchee Creek in Chickasaw County, Mississippi, is locally dominated by marshy vegetation. On more open lowlands managed by native people before 1540, such vegetation may have graded into the wetter grassland indicated above (types k and g).
Based on the preceding notes, Fig. 2 presents a hypothetical scheme of associations between vegetation types and soil series. Gradients among vegetation types are overlayed on the catenas of soil series (Fig. 1). It is hypothesized that each vegetation type was formerly most extensive on or near their overlayed soil series during pre-Columbian times. However, some modern descendants of original vegetation types cannot be reliably associated with particular soils today, especially on damper or lower ground with more drastic changes in disturbance regime, agricultural development and fragmentation. These more uncertain associations are indicated with question marks.
This framework does provide a useful initial model, but deserves refinement. It will be important to cross-reference such schemes in more detail with descriptions and mappings of vegetation types in the National Vegetation Classification and State Heritage Programs. Moreover, robust classifications should be built on a more detailed review of raw data from across the region. Also, such classification should ultimately be rooted in models of major ecological gradients and dynamic processes, rather than just hierarchical concepts of formations, alliances, associations and the like.
The gradient outlined here from lowland to upland vegetation is readily related to mapped soil series. However, the independent gradient from closed forest to open grassland is clearly influenced by dynamic factors that can reduce consistent associations with soil, even among better remnants of the original vegetation. Such factors have probably changed much during recent centuries. Deeper woods have probably remained best developed on relatively mesic, well-drained sites or on swampy soils. But red cedar has spread much into former prairies, while the original thickets and other transitions between woodland and grassland have probably declined considerably. Native grassland appears to have originally occurred on a wide range of soils, but became greatly modified after European settlement. Better remnants are now mostly restricted to shallower chalky soils (left-center of Figs. 1 and 2). More disturbed variants of native grassland, grouped under type (e) above, may have been concentrated below actively eroding exposures of chalk before settlement, on local alluvial soils such as Griffith (Fig. 1), but now appear to be widespread on several soil series.
These concepts can be tested. Research on modern or historical vegetation of the region could record soil types in a systematic fashion at study sites. But it will be important for ecologists to add their own local precision in mapping soils, since existing maps of the USDA are not reliable at scales less than 10-100 acres [4-40 ha]. And, for more general application of soil classification, it will be useful to consider series within the context of 'catenas'--a traditional concept in soil science that deserves more regular application across the ecological literature of eastern North America. More intensive, separate analyses of spatial variation in both soil and vegetation could allow more definitive correlations between soil and vegetation. Residual variation or 'noise' in those relationships could then be separated statistically to examine potential involvement of changes in 'disturbance regime'--defined broadly, from climatic disruptions to human land uses--and especially changes within recent centuries. In this way more dynamic models of interaction between soil and vegetation might be advanced.
This work would not have happened without support from Roundstone Native Seed, L.L.C., and our introduction to Mississippi by Daniel Coggin of Wildlife Mississippi, to whom we are particularly grateful. Brad Lieb generously provided unpublished review of original material on the history of Chickasaw lands. Several other people have helped with shared advice, knowledge and wisdom, including John Barone, Steve Brewer, Richard Brown, Charles Bryson, John Gruchy, JoVonn Hill, John Pascarella, Al Schotz, Heather Sullivan, Jennifer Seltzer, and some anonymous reviewers
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J.J.N. Campbell (1) * and W.R. Seymour, Jr. (2)
(1) Bluegrass Woodland Restoration Center, 3525 Willowood Road, Lexington, Kentucky 40517
(2) Roundstone Native Seed, 9764 Raider Hollow Road, Upton, Kentucky 42784-9216
Corresponding Author: firstname.lastname@example.org
Figure 1. Diagram showing generalized catenas of soil series in the Black Belt region, as related to parent material and topography. Within each box: 1st line = soil group modifier; 2nd line = soil group/class (upper case); 3rd line = series name; 4th line = typical texture. See USDA (2010a) for detailed descriptions of each soil series. Soil orders are color-coded as shown in the lower bar. Some common soils in peripheral sections of the Black Belt are included here, but soils more ttypical of disjunc blacklands elsewhere in southeastern states are excluded (e.g. Hannon, Okeelala and Toxey). [Supplementary material with details of trends in edaphic data is available from the senior author.] (a) ULTISOLS (b) ALFISOLS (c) VERTISOLS (d) MOLLISOLS (e) INCEPTISOLS (f) ENTISOLS TYPICAL PARENT TYPICAL TOPOGRAPHY MATERIAL MORE HILLY TRANSITIONAL LANDSCAPES IN GENERAL shallow/rocky soil Mixed uplands or Typic KANDIUDULT high terraces: fine Faceville fine sandy sandy loams to silt loam (a) loams Sandy uplands or Typic high terraces: FRAGIUDULT sandy loams to fine Ora sandy loams sandy loam (a) Clayey uplands: Ultic HAPLUDALF Vertic PALEUDALF acid clay and Brantley fine sandy Boswell fine locally sand or silt loam (b) sandy loam (b) above calcareous Clayey uplands: Note: Boswell and Leptic HAPLUDERT more influence of Brantley are mostly Watsonia clay (c) acid clay than mapped on chalk; not loamy Paleocene/Eocene Chalky uplands: Oxyaquic HAPLUDERT gentle slopes with Maytag silty influence of clay (c) overlying clay Chalky uplands: Typic HAPRENDOLL Rendollic EU Sumter steeper side-slopes Binnsville silty silty clay (e) to local alluvial clay (d) flats with clay Chalky uplands: Note: mesic soils Typic loamy toe-slopes, on NE-facing bluffs UDORTHENT Demopolis swales and alluvial with sugar maple silty clay loam (f) transitions need definition here Floodplains: loamy alluvium along perennial streams Floodplains: deep Typic HAPLUDERT clayey alluv. along Trinity clay (c) streams and backwater sloughs TYPICAL PARENT TYPICAL TOPOGRAPHY MATERIAL INTERMEDIATE TRANSITIONAL LANDSCAPES IN GENERAL moderate to deep Mixed uplands or Glossic FRAGIUDULT Fluvaquentic high terraces: fine Prentiss loam (a) PALEUDULT Brewton sandy loams to silt fine sandy loam (a) loams Sandy uplands or Typic Fluvaquentic high terraces: FRAGIUDULT PALEUDULT sandy loams to fine Savannah Stough sandy loams fine sandy loam (a) fine sandy loam (a) Clayey uplands: Vertic PALEUDALF Aquic HAPLUDERT acid clay and Kipling silt Brooksville silty locally sand or silt loam (b) clay loam (c) above calcareous Clayey uplands: Chromic DYSTRUDERT Aquic DYSTRUDERT more influence of Oktibbeha clay (c) Vaiden clay (c) acid clay than chalk; not loamy Chalky uplands: Oxyaquic HAPLUDERT Oxyaquic HAPLUDERT gentle slopes with Okolona silty Houston clay (c) influence of clay (c) overlying clay Chalky uplands: Aquic HAPLUDERT Chromic EPIAQUERT steeper side-slopes Griffith silty Sucarnochee to local alluvial clay (c) silty clay (c) flats with clay Chalky uplands: Aquic HAPLUDERT Vertic EPIAQUEPT loamy toe-slopes, Faunsdale clay Leeper silty clay swales and alluvial loam (c) loam (e) transitions Floodplains: loamy Fluvaquentic Aeric FLUVAQUENT alluvium along HAPLUDERT Belden silty clay perennial streams Marietta loam (c) loam (f) Floodplains: deep Fluvaquentic Vertic EPIAQUEPT clayey alluv. along HAPLUDOLL Catalpa Tuscumbia silty streams and silty clay loam (d) clay loam (e) backwater sloughs TYPICAL PARENT TYPICAL TOPOGRAPHY MATERIAL LESS HILLY LANDSCAPES IN GENERAL less well-drained Mixed uplands or Typic PALEAQUULT high terraces: fine Trebloc silt sandy loams to silt loam (a) loams Sandy uplands or Note: Brewton is high terraces: close to Stough but sandy loams to fine with more eluviated sandy loams clay Clayey uplands: Chromic DYSTRAQUEPT acid clay and Eutaw silty clay (e) locally sand or silt above calcareous Clayey uplands: Note: "Houston" more influence of included fine sandy acid clay than loams on Paleocene chalk; not loamy (Harper 1920) Chalky uplands: Note: "Houston" has gentle slopes with often eroded down to influence of Sumter (Gibson 1941) overlying clay Chalky uplands: steeper side-slopes to local alluvial flats with clay Chalky uplands: loamy toe-slopes, swales and alluvial transitions Floodplains: loamy Note: more open alluvium along marshy wetland soils perennial streams need definition here Floodplains: deep Typic EPIAQUEPT Una clayey alluv. along silty clay (e) streams and backwater sloughs Figure 2. Diagram showing suggested associations of gradients in original native vegetation to catenas of soil series in the Black Belt region. Lettered codes in parentheses (a to o) refer to the sequence of notes in text. Shading indicates the general degree of openness in the vegetation. Asterisks at the bottom of each cell indicate the general degree of agricultural conversion, based on descriptions of USDA (2010a), overall review of literature and general observation. The densest asterisks indicate land that was most suitable for crops in early agricultural development. Moderately dense asterisks indicate additional land that is now generally used for row crops, especially cotton, corn or soybeans. Less dense asterisks indicate that pasture and hay-production are at least as extensive as row crops. Lack of asterisks indicates that native vegetation is at least as extensive as agricultural land-native vegetation is mostly woody, except for the concentrations of prairie remnants on Binnville and Sumter soils TYPICAL PARENT TYPICAL TOPOGRAPHY MATERIAL MORE HILLY TRANSITIONAL LANDSCAPES IN GENERAL shallow/rocky soil Mixed uplands or (a) post oak woods high terraces: fine (or deeper woods) sandy loams to silt loams Sandy uplands or (a) post oak woods high terraces: (or deeper woods) sandy loams to fine sandy loams Clayey uplands: (a) post oak woods (a) post oak woods acid clay and (or deeper woods) locally sand or silt overlying chalk Clayey uplands: (a) post oak woods more influence of acid clay than chalk; not loamy Chalky uplands: (i/h1) red cedar, gentle slopes with drier thickets, or influence of grassy mixes? overlying clay Chalky uplands: (i) red cedar woods (f) subxeric chalk steeper side-slopes or grassy mixes grassland to local alluvial flats with clay Chalky uplands: (j1) submesic woods (h2) damper thickets loamy toe-slopes, below bluffs & on or grassy mixes? swales and alluvial toes transitions Floodplains: loamy (j2) more mesic alluvium along woods on toes & perennial streams terraces? Floodplains: deep (m) more mesic clayey alluv. along riparian woods streams and backwater sloughs TYPICAL PARENT TYPICAL TOPOGRAPHY MATERIAL INTERMEDIATE TRANSITIONAL LANDSCAPES IN GENERAL moderate to deep Mixed uplands or (a/b1) post oak or (a/b2) post oak or high terraces: fine oak-pine woods blackjack oak sandy loams to silt woods? loams Sandy uplands or (b1) oak-pine woods (b2) blackjack oak high terraces: woods? sandy loams to fine sandy loams Clayey uplands: (a/b2) post oak or (a/b2) post oak or acid clay and blackjack oak woods blackjack oak woods locally sand or silt overlying chalk Clayey uplands: (b2) blackjack oak (c1) drier acid more influence of woods or grassy grassland acid clay than mixes chalk; not loamy Chalky uplands: (d1) xeric tending (d2) xero-hydric gentle slopes with chalk grassland chalk grassland influence of overlying clay Chalky uplands: (e) transitional (g2) more hydric steeper side-slopes chalk grassland; chalk grassland to local alluvial wider if disturbed flats with clay Chalky uplands: (g1) more mesic (k) lowland loamy toe-slopes, chalk grassland? grassland? swales and alluvial transitions Floodplains: loamy (j3) submesic woods (l) canebrakes and alluvium along on terraces varied transitions? perennial streams Floodplains: deep (m) more hydric (n1) swampy woods clayey alluv. along riparian woods streams and backwater sloughs TYPICAL PARENT TYPICAL TOPOGRAPHY MATERIAL LESS HILLY LANDSCAPES IN GENERAL less well-drained Mixed uplands or (n2) swampy woods high terraces: fine with post and water sandy loams to silt oak? loams Sandy uplands or high terraces: sandy loams to fine sandy loams Clayey uplands: (c2) wetter acid acid clay and grassland locally sand or silt overlying chalk Clayey uplands: more influence of acid clay than chalk; not loamy Chalky uplands: gentle slopes with influence of overlying clay Chalky uplands: steeper side-slopes to local alluvial flats with clay Chalky uplands: loamy toe-slopes, swales and alluvial transitions Floodplains: loamy (k) lowland alluvium along grassland (marshy)? perennial streams Floodplains: deep (o) marshes and clayey alluv. along ponds? streams and backwater sloughs
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|Author:||Campbell, J.J.N.; Seymour, W.R., Jr.|
|Publication:||Journal of the Mississippi Academy of Sciences|
|Date:||Apr 1, 2011|
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