The Big Thicket 2009 Southeastern Naturalist 8(Special Issue 2):1–30 An Ecological Classification System for the National Forests and Adjacent Areas of the West Gulf Coastal Plain James E. Van Kley1,* and Rick L. Turner1 Abstract - We developed a multifactor ecological classification system (ECS) for the National Forests and adjacent lands of Texas and Louisiana. The ECS classifies lands into ecosystem types: repeating combinations of potential natural vegetation, soils, and physiography. This paper uses results of a portion of this effort from the northern part of Louisiana’s Kisatchie National Forest as an example. Forest stands were sampled across a range of soil and topographic situations. Non-metric multidimensional scaling ordinations and TWINSPAN classification of the samples based on ground-layer vegetation corresponded to gradients of topographic position, fire frequency, disturbance, and soil nutrients. A separate ordination of only upland stands clarified relationships between upland vegetation and soil texture. Ordination and TWINSPAN results formed the basis for a final classification of the sample stands and for descriptions and dichotomous keys for seven “land-type phases”—local ecosystem types that share soil and topographic attributes, natural plant communities, and responses to management or disturbance. ECS provides an ecologically relevant way to stratify the landscape for inventory, conservation, research, or management and gives the Forest Service and other professionals a valuable tool to aid in making ecologically informed decisions. Future goals include mapping ecological units on National Forest lands and expansion of the area covered. Introduction Most land classifications focus on only one aspect of the land resource such as ownership or political boundaries, existing vegetation types, topography, or soils. Classifications based on soils are widely used in forest inventory, but if their relationship to the biota is unknown, they are not fully relevant to forest management. Transitory phenomena such as existing plant communities or forest cover types form the basis for other classifications; these can become obsolete due to logging, storms, other disturbances, or natural succession. An ecological classification system (ECS) provides an alternative approach. An ECS expresses in simplified terms the interrelationships between vegetation and other parts of an ecosystem such as physiography (landform and topography) and soils and uses repeating combinations of these multiple ecosystem components to classify land. Physiography infl uences microclimate, drainage, and solar radiation, and correlates with soil conditions. Soil texture, nutrients, and moisture-holding capacity affect plant species composition and productivity, while the vegetation on a site serves as a “phytometer” that integrates environmental factors and gives them ecological meaning (Barnes et 1Department of Biology, PO Box 13003, Stephen F. Austin State University, Nacogdoches, TX 75963. *Corresponding author - jvankley@sfasu.edu. 2 Southeastern Naturalist Vol. 8, Special Issue 2 al. 1982). The product of an ECS is a manual containing descriptions of “ecological units” consisting of predictable combinations of soils, potential natural vegetation, and physiography. Ecological units are based on long-lived ecosystem attributes (soil properties, topography, and potential vegetation), but at the same time are relevant to existing vegetation patterns and thus highly relevant to conservation or management. Descriptions of ecological units can be used to identify the “ecological type” of any site in the covered region prior to management, conservation activities, or research. ECS can also be used to generate maps showing the distribution of ecological units across the landscape. An ECS-based map does not become obsolete when vegetation changes—in fact, several vegetative communities may be possible on one ecological type depending on management or successional stage. This paper describes an ECS for the national forest lands and adjacent areas of the Texas and Louisiana West Gulf Coastal Plain, focusing on data collected in northern Louisiana to illustrate the ECS development process. Multiple-factor ecological classification systems The earliest multiple-factor ECS, initiated by G.A. Kraus in the German state of Baden-Württemberg, has been in use since about 1946 (Spurr and Barnes 1980). In the US, Barnes et al. (1982) developed an ECS based on the Baden-Württemberg model for the Cyrus McCormick Experimental Forest in Michigan. Other examples are from the Piedmont and Upper Coastal Plain provinces in South Carolina Jones (1991), Michigan’s Sylvania Recreation Area (Spies and Barnes 1985), the Savannah River Plant in South Carolina (Van Lear and Jones 1987), the Shawnee Hills in Illinois (Fralish 1988), the Kickapoo River watershed in southwestern Wisconsin (Hix 1988), Huron and Manistee National Forests in Michigan (Cleland et al. 1994), Hoosier National Forest in Indiana (Van Kley and Parker 1993), Wayne National Forest in Ohio (Hix and Pearcy 1997), and Hiawatha National Forest in Michigan (Kudray 2002). In the western US, a related approach based largely on old-growth vegetation (which is assumed to “integrate” multiple ecosystem components), known as “habitat typing,” has long been in use on National Forest lands (e.g., Daubenmire 1980, Daubenmire and Daubenmire 1968). The initial ECS field guide for the Texas and Louisiana West Gulf Coastal Plain was submitted as an unpublished report to the US Forest Service by Turner et al. (1999) and revised and expanded into a 379-page, color-illustrated “Second Approximation” (Van Kley et al. 2007) in 2007. Vegetation studies on the West Gulf Coastal Plain Numerous previous studies provided background for ECS including descriptions of individual local plant communities (e.g., MacRoberts and MacRoberts 1992, 1995, 2004; Marietta and Nixon 1983; Nixon et al. 1980). Several papers also describe landscape-wide vegetation-environment relationships from the Big Thicket area of southeast Texas (immediately south of the ECS study area), the most notable being Marks and Harcombe (1981) and Harcombe et al. (1993). While such literature formed a good working first 2009 J.E. Van Kley and R.L. Turner 3 approximation for ecological classification, we desired that ECS be based primarily on independent quantitative data so that the previous studies could be used to corroborate ECS results. Several theses and publications provide detailed analyses and summaries of portions of the ECS data (collected in stages over a period of more than 10 years) including Dehnisch (1998), Mundorf (1998), Van Kley and Hine (1998), Turner, (1999), Van Kley (1999a), Van Kley (1999b), and Quine (2000); a generalized version of the resulting ecological units is presented by Van Kley in Diggs et al. (2006). Objectives Relating patterns of natural vegetation to natural environmental factors is the core of ecological classification; of many possible soil and physiographic factors, we desired to find ones strongly related to natural vegetation. Once these factors were identified, ecological types could be described. The aim of our study was to use field data to identify vegetation- environment relationships and use these relationships to develop the local-level (land-type and land-type phase) ecological units for the national forests and adjacent areas of the West Gulf coastal plain. To accomplish this goal, we sampled sites from a range of geological, topographic, and soil settings covering much of the region and subjected the resulting vegetation and environmental data to multivariate analysis. In this paper, we use previously unpublished data collected in 2002 from a portion of Kisatchie National Forest in northern Louisiana as an example. National hierarchy of ecological units The local ECS is nested within a pre-existing National Hierarchical Framework of Ecological Units (Table 1): a scientifically derived regionalization of ecosystems organized into nested, increasingly homogeneous units of decreasing orders of scale from upper to lower levels (McNab and Avers 1994). Our ECS inherits this hierarchy and extends it by developing local-level ecological units. At the highest level, Texas and Louisiana lie entirely within the Humid Temperate Domain and the Subtropical Division (Bailey et al. 1994). Ecosystem units at a regional scale (“province,” “section,” and “subsection”), are based on combinations of regional climate, geology, and broad-scale vegetation types. Bailey et al. (1994) and McNab and Avers (1994) described the domains, divisions, provinces, and sections for the US, while Keys et al. (1995) mapped the eastern and southern US sections and subsections. The greater study area (Fig. 1a) occurs across three provinces and three sections: the Middle Coastal Plain, Western Section (231E); the Coastal Plains and Flatwoods, Western Gulf Section (232F); and the Mississippi Alluvial Basin Section (234A). We collectively refer to these as the West Gulf coastal plain. Local-level ecological units, based on local patterns of natural vegetation, soils, geology, and topography are in decreasing order of scale, the “land-type association” (LTA), “land-type'” (LT), and “land-type phase” (LTP). The US Forest service previously delineated 18 LTAs across the 4 Southeastern Naturalist Vol. 8, Special Issue 2 national forest lands of Texas and Louisiana largely on the basis of geology and broad vegetation differences mainly related to the former natural range of upland Pinus palustris P. Mill (Longleaf Pine) communities (USDA Forest Service 1996, 1997). Circumscription (though not mapping) of land-type Table 1. Hierarchical levels of the USDA Forest Service Ecological Classification and Inventory. Modified from Forest Service Handbook 1909.21 (USDA 1979). Planning Level Factors Approximate scale level Province Geomorphology, climate Multi-state Nationalregional Section Geomorphology, climate, 1000’s of square miles Regionalvegetation subregional Subsection Climate, geomorphology, 0 to 100s of square Multi-forest, vegetation miles state Landtype Landforms, natural overstory 10s to 10,000s of acres Forest association (LTA) communities, soil associations Landtype (LT) Landform, natural 10s to 100s of acres Ranger vegetative communities, soils district, Management area, Opportunity area Landtype Soils, landscape position, 1 to 100s of acres Project phase (LTP) natural vegetative communities Figure 1 (opposite page). Study area. a) Locations of National Forest boundaries (dark outlines) and the provinces, sections, and subsections of the national ECS hierarchical framework on the West Gulf Coastal Plain of Texas and Louisiana. The subsections with the majority of National Forest lands are: for the Southeastern Mixed Forest province (231)—231Ea (South Central Arkansas), 231Ef (Piney Woods Transition), 231Eg (Sand Hills), and 231Eh, (Southern Loam Hills); for the Outer Coastal Plain Mixed Forest Province (232)—232Fa (Southern Loam Hills) and 232Fe (Piney Woods Transition). 232Fc and 232Fd are alluvial valley subsections associated with major rivers. 234Ai is the Red River Alluvial Plain subsection of Louisiana. Eighteen land-type associations (LTAs) occur in the portions of the subsections with USFS lands. SHNF, DNF, ANF, and SNF = Sam Houston, Davey Crockett, Angelina, and Sabine National Forests, respectively. The map is modified from Keys et al. (1995). b) Location of the Caney Ranger District of Kisatchie National Forest (dark outlines) within the South Central Arkansas subsection (231Ea) and North Louisiana Clayey Hills (231Ea.9) LTA. Adjacent LTAs include 231Ea.8 (Caney Lakes Rolling Uplands), 231Ea.4 (Alluvial Floodplains and Terraces), and 234Ai.7 (Red River Alluvial Plain). Numerals in the 3 Caney Ranger District units represent the number of stands sampled from (left to right) the Caney, Middlefork, and Corney Units. 2009 J.E. Van Kley and R.L. Turner 5 phases and the land-types within which they are nested was the aim of our study. This paper describes development of land-type phases for a land-type association known as the “North Louisiana Clayey Hills,” or “231Ea.9,” which is in the South Central Arkansas Subsection (231Ea) and contains most of Kisatchie National Forest's Caney Ranger District (Fig. 1b). Methods Study area The general study area included the lands of Louisiana's Kisatchie National Forest and the four national forests in Texas (Fig. 1a). Louisiana and 6 Southeastern Naturalist Vol. 8, Special Issue 2 eastern Texas have a humid, subtropical climate with hot, humid summers, mild winters, occasional frost, and negligible snowfall (Larkin and Bomar 1983). Precipitation occurs year-round, but more falls in winter and spring. Summer precipitation is usually from afternoon thunderstorms, lightning from which ignited low-intensity fires that frequently burned through the pine-dominated woodlands typical of the region's presettlement uplands (Christenson 1981, Frost 1993). Mean annual precipitation increases from west to east, ranging from 42 inches (107cm) in Houston County, TX (Larkin and Bomar 1983) to 57 inches (145 cm) in Rapides Parish, LA (Kerr et al. 1980). Surface geology consists of a series of largely east–west sedimentary deposits that become progressively younger from north (Eocene) to south (Miocene and Pliocene) (Bureau of Economic Geology 1975, 1979, 1993; Sellards et al. 1932; Snead and McCulloh 1984). The North Louisiana Clayey Hills LTA is a rolling terrain on Eocene-aged Cook Mountain and Cockfield surface geology (USDA Forest Service 1997) that encompasses most of the Caney Ranger District of Kisatchie National Forest (Fig. 1b; Snead and McCulloh 1984). Presettlement upland vegetation consisted of Shortleaf Pine-oak-hickory communities (Mohr 1896, Sargent 1884), although presently most stands are second-growth Pinus taeda L. (Loblolly Pine)-Liquidambar styracifl ua L. (Sweetgum)-oak forests. The area is outside of the natural range of Longleaf Pine communities (Frost 1993). Field sampling The overall ECS strategy involved sampling a series of stands in each of the previously defined 18 LTAs on national forest lands, thereby compiling a series of essentially independent data sets each covering one to several adjacent LTAs. Here we describe sampling on Kisatchie National Forest's Caney Ranger District; methodology for the remaining datasets was similar and is described in Dehnisch (1998), Mundorf (1998), Turner, (1999), Van Kley and Hine (1998), Van Kley (1999a), Van Kley (1999b), and Quine (2000). Desiring to reduce the infl uence of historical factors on plant communities so as to not obscure relationships with soil and physiography, we only used stands listed in the Forest Service’s Continuous Inventory of Stand Conditions (CISC) database as being more than 60 years of age. To ensure data represented the region's full ecological range, we generated a list of age-eligible stands from each forest compartment in the District and used USGS topographic maps and soil maps (Kilpatrick and Henry 1989, Kilpatrick et al. 1998) to sort stands into “selection types” based on topographic position and soils (Table 2). Random stands from each selection type were field checked and approved for sampling if free from substantial recent disturbance or excessive heterogeneity. “Unusual” sites (three forested seeps and a fl oodplain depression with Taxodium distichum (L.) L.C. Rich. [Bald Cypress]) were also selected if they met age and disturbance criteria. In each stand, we established a transect from a random starting point and located four points at 20-m intervals along the transect. Each point defined 2009 J.E. Van Kley and R.L. Turner 7 a plot with a series of nested subplots: A 1000-m2 “search area” a 250-m2 circular subplot, a 100-m2 subplot, a 10-m2 subplot, and a 1-m2 subplot. The presence of ground-layer species (<1 m tall) in this series of subplots with increasing area was scored: plants occurring in the 1-m2 subplot were given an occurrence rank of 5, those not in the 1-m2 subplot but growing in the 10 -m2 subplot were given a rank of 4, those only in the 100-m2 subplot were given a rank of 3, and those only within the 1000-m2 area were given a rank of 2 if there were three or more individuals or colonies and a rank of 1 if there were only one or two individuals or small colonies. The 1000-m2 search area, its long axis perpendicular to the transect, extended 25 m on each side of the transect and 10 m along the transect on each side of the plot center point. Boundaries, located by pacing and marked with fl ags, were approximate, but care was taken to insure no overlap with adjacent plots. A mean occurrence rank was calculated for each species over the four plots in each stand. This abundance measure was used in subsequent analyses because multiple data were collected by multiple persons over several years and the occurrence ranks were deemed more objective and uniform across datasets than coverage estimates. Stems were counted for woody species less than 10 cm dbh occurring in the 100-m2 subplot; understory trees and shrubs were not used in the analyses, but they contributed to LTP descriptions in the ECS field guide. Diameters (dbh) were recorded for all stems greater than 10 cm dbh. in the 250-m2 subplot. Taxonomy followed Kartesz (1999). The texture, color, and depth of each soil horizon was described from a soil pit located in a random direction roughly 3 m from the center point of the 2nd plot and three, likewise-located auger cores at plots 1, 3, and 4. A topsoil sample from a depth of 10–15 cm was analyzed for texture (percentage clay, sand, and silt) and soil properties including pH, nitrates (mg/L), phosphorus (mg/L), potassium (mg/L), calcium (mg/L), magnesium (mg/L), zinc (mg/L), sulphur (mg/L), manganese (mg/L), copper (mg/L), and iron (mg/L) at the Stephen F. Austin State University Soil Testing Laboratory. Texture was also estimated by feel at depths of 50 and 100 cm, and depth to gray redox depletions was measured if observed within the top 150 cm. Table 2. A list of the preliminary “selection types” used to stratify the landscape of the North Louisiana Clayey Hills for sample selection. Soil textures refer to the finest texture within the upper 50 cm of the profile. Even distribution of samples was impossible because of the rarity of age/disturbance-eligible examples of certain types. Selection type Number of samples selected Sandy upper slopes and summits 0 Loamy upper slopes and summits 7 Clayey upper slopes and summits 11 Sandy lower slopes 2 Loamy lower slopes 4 Clayey lower slopes 5 Minor stream bottoms (<100 m wide) 7 Major stream bottoms (>100 m wide) 10 Other: seeps and swamps 4 8 Southeastern Naturalist Vol. 8, Special Issue 2 Physiographic measurements included slope gradient (%) and elevation (m above sea level). Elevation of a sample site relative to that of the nearest ridgetop or broad summit and to the nearest bottom (stream of 2nd or greater order) was determined from a USGS topographic map. Topographic position was calculated as [(site elevation - bottom elevation) / (ridge elevation - bottom elevation)] x 100. Thus, summits and stream fl oodplains would have a position of 100% and 0%, respectively. Each stand was evaluated on a scale of 1–10 for evidence of fire (1 = extensive charred logs, blackened bark, fire scars—indicative of recent and frequent fire; 10 = no visible evidence of fire). Stands were also graded on a 12-point qualitative scale (1 = high, 12 = poor) for “natural quality” based on visible evidences of past disturbance such as old stumps, fence remnants, exotic species, etc. Stand locations were recorded with a global positioning system (GPS). Data analysis Species data (mean occurrence rank for ground layer and importance values based on whole-stand relative density and basal area for overstory) were subjected to non-metric multidimensional scaling (NMS; Mcune and Medford 1999) and two-way indicator species analysis (TWINSPAN; Hill 1979b). Data were not transformed, but species found in only one sample were omitted and a Taxodium distichum (L.) L.C. Rich (Baldcypress) swamp site was omitted from the ordinations after a preliminary run showed it to be an outlier. We used PC-ORD (Mcune and Medford 1999), which incorporates strict convergence criteria, and corrected rescaling algorithms into TWINSPAN, addressing the instability and sample order-dependence (Oksanen and Minchin 1997) of earlier versions. For TWINSPAN, pseudopsecies cut-levels of 0, 2, and 4, were used; all other options were left at their default settings. Divisions were recognized down to the level (3rd and 4th in our case) where sample groups no longer occurred in largely distinct regions when superimposed on a corresponding ordination diagram and only species with mean occurrence >1.8 in at least one of these groups were displayed in the final tabulation. The Sørensen distance measure was used for NMS, and optimal dimensionality for each NMS was determined by plotting stress against the number of dimensions. “Autopilot” mode in PC-ORD was used: the optimal solution (minimum stress) from 40 runs with real data was selected, and a Monte Carlo test based on 50 runs with randomized data tested the hypothesis that the stress of the final solution was lower than that encountered at random. Resulting ordination axes (samples ordered by species composition) were interpreted as refl ecting underlying environmental gradients. Ground-layer vegetation was emphasized because of the direct relationship between overstory and many common disturbances such as selective logging, planting, pests (e.g., Dendroctonus frontalis Zimmermann [Southern Pine Beetle]), and wind damage. Compositional gradients (expressed by NMS scores) were compared with soil and physiographic factors as well as with overstory NMS scores using Pearson’s correlations. To clarify relationships among samples from upland sites, the upland samples, a subset of 20, were ordinated separately and the initial TWINSPAN-derived classification of upland samples revised accordingly. The resulting interpreted 2009 J.E. Van Kley and R.L. Turner 9 sample ordinations and classification were the basis for describing the landtype phases for the North Louisiana Clayey Hills. The Caney data were combined with the other ECS data sets from the West Gulf Coastal Plain and the combined samples (420 stands and 815 species) subjected to detrended correspondence analysis (DCA; Hill 1979a, Hill and Gauch 1980) based on mean ground-layer occurrence rank, thereby allowing us to observe plant communities from the North Louisiana Clayey Hills in the context of those from other LTAs. All samples, including those from the Caney, were active, and no data transformations were used, but 23 non-forested samples from glades and prairies, the 19 samples from the Red River Alluvial Plain, and species occurring in only one sample were omitted. Samples in each non-Caney data set had been previously classified into communities, and these classifications were pooled and displayed on the resulting ordination diagram. Results We found 340 vascular plant species on 50 sample stands from the Caney Ranger District of Kisatchie National Forest. A two-dimensional NMS ordination (Fig. 2) of 49 stands and 286 groundlayer species based on mean ranked-occurrence values showed a gradient of communities from those of well-drained upland sites to those of irregularly and seasonally fl ooded valleys of medium-sized and large streams (Corney Bayou and the Middle Fork of Bayou D’Arbonne). Final “stress” for NMS was 15.29, final instability = 0.0001, and Monte Carlo P = 0.032. The ordination corresponded to several soil and environmental factors: sites with low first- and second-axis scores had higher topographic positions, were more acid, lower in nutrients, and showed more evidence of fire than those with high scores (Fig. 2, Table 3). Ground-layer ordination axes also correlated with the first and third axes of a 3-dimensional NMS of samples based on overstory importance values (Table 3; final stress = 14.97, instability = 0.00011, Monte Carlo P = .019): lowlands were typically dominated by deciduous eudicotyledons (hardwoods), sites from the middle of the gradient supported mixtures of Loblolly Pine and hardwoods, and the uplands were pine-dominated. “Joint plot” vectors on Figure 2 indicate the direction and relative strength of correlations; the minimum r2 for joint-plot correlations displayed in the figure was 0.23. TWINSPAN of all 50 samples resulted in classification of the samples into seven groups (the six superimposed on Figure 2 and the Bald Cypress swamp omitted from the ordination). Groups ranged from uplands dominated by Shortleaf Pine-oak-hickory communities to the fl oodplains and swamps along large streams (Appendix 1). TWINSPAN also classified the species into seven species groups (Appendix 1). These groups were variously characteristic of upland sites, mesic lower slopes and small-stream bottoms, larger fl oodplains, forested seeps, and wetlands; an additional group of widespread species occurred across a range of habits (Appendix 1). The species groups were important in developing the descriptions of ecological 10 Southeastern Naturalist Vol. 8, Special Issue 2 units and also contributed to the “master” ecological species groups listed in Van Kley et al. (2007) that were formed by combining equivalent species groups from ECS data sets for all 18 LTAs. Appendix 1 provides the names of the “master” ecological species groups to which each of the Appendix 1 groups are closest. The gradients recovered by the ordination were dominated by topography and soil nutrients; correlations with soil sand and clay were weak (Table 3). Figure 2. A two-dimensional NMS ordination of 49 samples and 286 species from the Caney Ranger District of Kisatchie National Forest based on mean rankedoccurrence values for ground layer species. Final stress = 15.29, Monte Carlo P = 0.032, final instability = 0.0001. Dotted lines and labels indicate a classification of the samples based on TWINSPAN. “Joint plot” lines indicate the direction and relative strength of correlations between ordination scores and external environmental factors (minimum r2 for joint-plot display = 0.23). Correlations with individual ordination axes are shown in Table 3. “Less fire” is expressed on a scale of 1–10: 1= strong evidence of recent or frequent fire, 10 = no evidence of fire. “MoDpth” = depth of soil to gray redox depletions, “clay” = percentage of clay-sized mineral particles in the topsoil. “T_Pos%” = topographic position % = vertical position of site relative to the nearest local summit and steam bottom. “-NQ”= “natural quality” expressed on a scale of 1–12: higher values = more evidence of disturbance and lower quality. “OvNms1” and “OvNms3” = the 1st and 3rd NMS ordination axes of the 49 samples based on importance values for trees >10 cm dbh. 2009 J.E. Van Kley and R.L. Turner 11 Among uplands, analysis resolved a “main” upland type with a Shortleaf Pine-oak-hickory-Euphorbia corollata L. (Flowering Spurge)-Galactia (milkpea spp.)-Desmodium spp. (ticktrefoil) community, and a more denselyshaded Loblolly Pine-Sweetgum-Parthenocissus spp. (creeper) community that was transitional fl oristically (and possibly topographically) to the mesic sites (Fig. 2, Appendix 1). However, other West Gulf Coastal Plain data sets and literature indicated relationships between soil texture and vegetation, especially on upland sites (Marks and Harcombe 1981; Van Kley 1999a, 1999b). When we further investigated this possibility—eliminating most of the strong upland/lowland gradient that might obscure other patterns by running a separate 3-dimensional NMS (final stress = 10.7, instability = 0.00001, Monte Carlo P = 0.02) with a subset of 20 “upland” samples and 185 species (all the “dry-mesic” sites of Fig. 2 and two “borderline” mesic sites)—the first axis of this upland NMS was indeed related to soil texture; clayey sites generally had low scores and sites with loamy soils high scores, and percentages of sand and clay throughout the soil profile were significantly correlated with the axis (Fig. 3, Table 4). The third axis was correlated with natural quality (sites with low scores showed more evidence of human impact) as well as to fire and elevation (Fig. 3); the second axis also varied with fire and elevation (Table 4). The second and third axes together largely represent the dimension previously observed among the uplands in Figure 2. ECS integrates fl oristic variation with soil and physiography, not disturbance and site-history. However, ordering of upland samples in the analysis of Figure 2 as well as the 2nd/3rd axes of the upland-only NMS (Fig. 3) Table 3. Correlations between soil and topographic factors and the axes of a two-dimensional non-metric multidimensional scaling (NMS) ordination of 49 samples and 286 species from the Caney Ranger District of Kisatchie National Forest based on density-dependant ranked occurrence of ground layer species. “Fire” is expressed on a scale of 1–10 with 1 = strong evidence of recent or frequent fire and 10 = no evidence of fire. “Depth to gray mottles” = depth of soil to gray redox depletions. “Topographic position %” = vertical position of site relative to the nearest local summit and steam bottom. The critical value for r is 0.28 for P < 0.05. NMS Axis 1 2 Topographic position % -0.53 -0.78 Elevation (m) -0.41 -0.71 Depth to gray mottles -0.76 -0.63 Fire 0.57 0.74 pH -0.69 -0.48 Manganese 0.30 0.51 Copper 0.46 0.71 Magnesium 0.47 0.55 Iron 0.51 0.51 Overstory NMS axis 1 0.60 0.64 Overstory NMS axis 3 0.59 0.67 Natural quality -0.453 -0.433 Percentage topsoil sand (10 cm) -0.300 -0.413 Percentage topsoil clay (10 cm) 0.221 0.316 12 Southeastern Naturalist Vol. 8, Special Issue 2 represented a confounding of disturbance with elevation. Moreover, classifi- cation of upland sites based on the all-sites analyses or the 2nd/3rd axes of the upland-only NMS resolved only one “true upland” group plus a group merely transitional to the mesic sites. We therefore used soil texture (the gradient expressed by the 1st upland NMS axis) as the basis for instead classifying upland stands into loamy uplands and clayey uplands (Fig. 3). Treating the samples in this manner also allowed the classification to be more consistent with previously developed portions of ECS from adjacent LTAs. Sites with deep, sandy soils (arenic soils) were not sampled on the District as we did not locate stands that met minimum-disturbance and age criteria. However, we encountered early successional and disturbed examples, usually associated with Flo and Wolfpen soils, during site selection and sampling. We used LTP descriptions from data for nearby land-type associations in northern Sabine National Forest, TX (Turner 1999) and the Winn Ranger District of Kisatchie National Forest (Dehnisch 1998) to describe a local arenic-soil ecotype. To observe vegetation of the North Louisiana Clayey Hills in the context of other West Gulf coastal plain LTAs, we ordinated the Caney District ground-layer samples with those from the other ECS datasets (DCA eigenvalues = 0.543 and 0.274 for the first two axes, respectively). Figure 4 shows the 50 samples from the Caney Ranger District (solid circles) in the context of the greater ECS data set. Longleaf Pine communities were not encountered in the North Louisiana Clay Hills: indeed, the area is well north of the historic distribution of Longleaf Pine (Cruikshank and Eldredge 1939, Frost 1993, Mohr 1897, Williams and Smith 1995); however, the ordination does clearly show that communities encountered in the Caney District were well Table 4. Correlations between soil and topographic factors and the axes of a three-dimensional non-metric multidimensional scaling (NMS) ordination of 20 upland samples and 185 species from the Caney Ranger District of Kisatchie National Forest based on density-dependant ranked occurrence of ground layer species. “Fire” is expressed on a scale of 1–10 with 1 = strong evidence of recent or frequent fire and 10 = no evidence of fire. “Depth to gray mottles” = depth of soil to gray redox depletions. “Topographic position %” = vertical position of site relative to the nearest local summit AND steam bottom. The critical value for r is 0.43 for P < 0.05. NMS Axis Factor 1 2 3 Percentage topsoil clay (10 cm) -0.53 0.28 -0.08 Percentage clay (50 cm depth) -0.48 0.21 0.21 Percentage clay (100 cm depth) -0.63 0.06 -0.10 Percentage topsoil sand (10 cm) 0.63 -0.13 0.14 Percentage sand (50 cm depth) 0.59 -0.15 -0.18 Percentage sand (100 cm depth) 0.65 0.04 -0.07 Depth to gray mottles 0.75 0.05 0.42 Zinc 0.22 0.43 0.59 Natural quality index -0.13 -0.28 -0.76 pH 0.62 -0.17 -0.34 Fire -0.04 -0.55 -0.68 Topographic position % -0.01 0.19 0.54 Elevation (m) 0.04 0.64 0.77 2009 J.E. Van Kley and R.L. Turner 13 within the fl oristic range of equivalent communities from other portions of the West Gulf Coastal Plain. Figure 3. A three-dimensional NMS ordination of 20 upland samples and 185 species from the Caney Ranger District of Kisatchie National Forest based on mean rankedoccurrence values for ground layer species. Axes 1 and 3 are displayed. Monte Carlo P = 0.02, Final “stress” = 10.7, final instability = 0.00001. Solid and open shapes represent sites with >35% and <35% clay at 50 cm depth respectively; the resulting soil-texture based classification of samples forms the basis for describing upland ecological units. Squares and triangles represent a TWINSPAN-derived classification of samples, respectively, into Shortleaf Pine- and Loblolly Pine-dominated communities also presented in Figure 2 and Appendix 1. Right triangles represent 2 “borderline” mesic sites (separated from other samples in ordination space by low 2nd axis scores). “Joint plot” lines indicate the direction and relative strength of correlations between ordination scores and external factors (minimum r2 for joint-plot display = 0.23). Actual correlations are shown in Appendix 1. “Less Fire” is expressed on a scale of 1–10: 1 = strong evidence of both recent or frequent fire and 10 = no evidence of fire. “MoDepth” = depth of soil to gray redox depletions. “Clay 10,” “clay 50,” and “clay 100” represent the percentage of clay-sized mineral particles in the soil at depths of 10, 50, and 100 cm respectively. “Sand 10,” “sand 50,” and “sand 100” represent the percentage of sand-sized mineral particles in the soil at depths of 10, 50, and 100 cm respectively. “-NQ”= “natural quality” on a scale of 1–12: higher values = more evidence of disturbance and lower quality. “T_Pos%” = topographic position % = vertical position of site relative to the nearest local summit and steam bottom. 14 Southeastern Naturalist Vol. 8, Special Issue 2 Table 5. A dichotomous key to the land-type phases of the North Louisiana Clayey Hills. Species groups, described in Van Kley et al. (2007), are cross-referenced to their closest equivalents in this paper in Appendix 1. 1a. Upper slopes, broad uplands, or ridgetops. Sites are typically pine-dominated 2 1b. Lower slopes, ravines, hillside seeps, stream terraces, or stream fl oodplains. Sites are typically deciduous hardwood-dominated. 4 2a. Soils are arenic (sandy surface layer more than 50cm thick) or sandy throughout the profile. Soils usually mapped as Flo or Wolfpen. The Tragia species group may be present. 231Ea.9.1.20 Shortleaf Pine-Blackjack Oak/ Tragia Sandy Dry Uplands 2b. Soils are loamy or clayey; any sandy surface layer is <50 cm thick. 3 3a. Soils are either loamy throughout or have a sandy loam, loamy sand, or gravelly surface layer more than 30 cm thick over clay subsoil. Often mapped as Darley, Ruple, Mahan, Bowie, Darbonne, or Angie. Species from the Callicarpa and Chasmanthium groups are abundant. 231Ea.9.1.30 Shortleaf Pine-Southern Red oak/ Callicarpa-Chasmanthium Loamy Dry-Mesic Uplands Figure 4. A DCA ordination 420 sample sites and 815 species representing the combined ECS datasets based on ground layer mean ranked occurrence. All samples, including those from the Caney were active in the ordination solution. Disjunct samples from non-forest prairies, glades, and other open communities were removed prior to analysis. Eigenvalues were 0.543 and 0.274 for axes 1 and 2 respectively. Samples from the Caney Ranger District of Louisiana’s Kisatchie National Forest (solid circles) are shown in context of plant communities from other regions of the West Gulf Coastal Plain. 2009 J.E. Van Kley and R.L. Turner 15 Table 5, continued. 3b. Any loamy surface soil is less than 30 cm thick over clay subsoil. Soils are somewhat poorly drained and usually have shrink-swell properties. Gray drainage mottles may be present and a perched water table may occur. Includes most areas mapped as Sacul and Eastwood soils. Species from the Callicarpa and Chasmanthium groups are abundant. 231Ea.9.2.10 Shortleaf Pine/ Chasmanthium Clayey Dry-Mesic Uplands 4a. Moderate to steep lower slopes and ravines or minor stream terraces. Species from the Callicarpa, Chasmanthium, and Mitchella groups are common but the Bignonia and Justicia groups are rare or absent. 231Ea.9.3.10 White Oak-American Beech-Loblolly Pine/ Chasmanthium Loamy Mesic Lower Slopes 4b. Valleys and fl oodplains of small or medium-sized intermittent or perennial streams or areas of groundwater seepage. 5 5a. Constantly saturated groundwater seepage areas (baygalls) at the head of or along small streams. Deep, gray, nearly permanently saturated, sandy loam soils. Soils belong to the Osier series. Magnolia virginiana L. (Sweetbay Magnolia), Nyssa bifl ora Walt. (Swamp Tupelo), and Acer rubrum L. (Red Maple) dominate the overstory. Ilex decidua Walt. (Possumhaw), Rhododendron prinophyllum (Small) Millais (Early Azalea), andVaccinium fuscatum Ait. (Arkansas Blueberry) are common in the understory. The Osmunda group is common. 231Ea.9.4.30 Sweetbay-Swamp Tupelo/ Osmunda Sandy Wet Forested Seeps 5b. Stream bottoms or fl oodplains without significant surface seepage of groundwater, the Osmunda group absent. 6 6a. Small intermittent or perennial stream fl oodplains typically less than 100 m wide. Flooding is intermittent and sites generally fl ood for less than 5% of the growing season. Soils are commonly mapped as Iuka soils or as the soil type of adjacent uplands. Overstory includes Quercus nigra L. (Water Oak), Liquidambar styracifl ua L. (Sweetgum), Pinus taeda L. (Loblolly Pine), and often Fagus grandifolia Ehrh. (American Beech). The Chasmanthium, Callicarpa, and Mitchella groups are common; species from the Bignonia and Justicia groups are rare. 231Ea.9.4.10 Water Oak/ Mitchella Loamy Mesic Strea Bottoms 6b. Floodplains of medium-sized or large perennial streams, fl oodplains more than 100 m wide. Flooding is irregular or seasonal; sites are fl ooded for more than 5% of the growing season. Soils are commonly mapped as Guyton or Iuka. Flood-tolerant species such as Quercus michauxii Nutt. (Swamp Chestnut Oak), Quercus phellos L. (Willow Oak), Ulmus Americana L. (American Elm), and Quercus laurifolia Michx. (Laurel Oak) are often present. Members of the Bignonia and Justicia groups are usually present. 7 7a. Floodplains are irregularly fl ooded (fl ood for <12.5% of a typical growing season). Seasonally fl ooded (12.5–25% of season) areas exist as small, isolated areas in depressions. Members of the Chasmanthium, Callicarpa, and Mitchella groups are common. Overstory is a variable mixture of mesic and fl ood tolerant species, but Swamp Chestnut Oak, Water Oak, and Loblolly Pine may be common. 231Ea.9.4.20 Sweetgum-Oak/ Bignonia Loamy Wet-Mesic Stream Bottoms 7b. Floodplains are largely seasonally fl ooded (12.5–25% of a typical growing season) or if fl ooded less, exist on a landscape with a significant seasonally fl ooded component. Swampy areas with Bald Cypress may also occur. In Kisatchie National Forest’s Caney Ranger District, restricted to the lowest, most downstream parts of the fl oodplains of Corney Bayou and the Middle Fork of Bayou D’Arbonne. Tbese areas lack the Chasmanthium, Callicarpa, and Mitchella groups, but the Bignonia and Justicia groups are common. Flood-tolerant oaks (Willow, Laurel, and Quercus lyrata Walt. [Overcup]) often dominate. 231Ea.4 Alluvial Floodplains and Terraces Landtype Association 16 Southeastern Naturalist Vol. 8, Special Issue 2 The results enabled us to circumscribe seven land-type phases for the North Louisiana Clayey Hills (Table 5). The classifications of Appendix 1 for non-uplands and of Figure 3 for upland samples formed the basis for the LTPs. Dichotomous keys (Table 5) and detailed data-derived descriptions of the topography, soils, hydrology, known natural disturbances and processes, ground-layer species, overstory, understory trees, and shrubs for each land-type phase were generated. Each LTP is named after dominant overstory species, a characteristic ecological species group, a soil or hydrologic feature, and its typical topographic position (Table 5). The ecological species groups in the names and keys (Table 5) are the pooled “master” species groups of Van Kley et al. (2007), but they mainly correspond to the TWINSPAN-derived species classification of Appendix 1 which “crosswalks” its species classification with the “master” species groups. LTPs were aggregated into four land-types: 231Ea.9.1 (sandy/loamy uplands), 231Ea.9.2 (clayey uplands), 231Ea.9.3 (mesic slopes and terraces), and 231Ea.9.4 (minor stream bottoms). The unique code for a LTP (Table 5) incorporates the symbols or numbers for all ecological units of the hierarchichy in which it is nested. For example, the Caney Ranger District of Kisatchie National Forest is within the Southeastern Mixed Forest Province (231), the South Central Arkansas Subsection (231Ea), and the North Louisiana Clayey Hills LTA (231Ea.9; Fig. 1). Upland sites with loam soils belong to the Sandy/Loamy Uplands Landtype (231Ea.9.1) and the “Shortleaf Pine-Quercus falcata Michx. (Southern Red Oak)/Callicarpa (beautyberry spp.)-Chasmanthium (woodoats spp.) Loamy Dry-Mesic Uplands” Landtype Phase (231Ea.9.1.30). Keys and LTP descriptions provided for each LTA comprise the bulk of the ECS fieldguide (Van Kley et al. 2007). Figure 5 summarizes the main features of the Caney LTPs. Two wet, low fl oodplain terraces and a Baldcypress swamp associated with the larger downstream fl oodplains of Corney Bayou and Bayou D’Arbonne, were interpreted as a result of the ordination in Figure 4 as belonging to the adjacent Alluvial Floodplains and Terraces land-type association; data from those sites contributed to descriptions of ecotypes of alluvial LTAs rather than those of the North Louisiana Clay Hills (Table 5 - couplet 7b). Discussion The complete ECS effort of which the samples from the Caney Ranger District are only a part consisted of 462 sample sites, 956 species, and 11 separate data sets representing the 18 land-type associations of the region (Table 6). Results from the various data sets generally yielded similar results: topographic position, percentage of soil sand and clay, nutrients, fire history (when available), and hydrologic factors (depth to gray mottles, high-water marks, fl ood depth) were among those most consistently and strongly correlated with vegetation gradients (Table 6). Accordingly, we emphasized these factors when describing environmental components of ecological units. 2009 J.E. Van Kley and R.L. Turner 17 ECS results are largely supported by local literature. Marks and Harcombe (1981) related woody plant communities from the Big Thicket area of southeast Texas to environmental gradients. Compositional variation correlated primarily with percentage of sand in the surface soil and secondarily to aspects of soil fertility. Harcombe et al. (1993) examined plant communities in the Longleaf Pine region of the West Gulf Coastal Plain. Vegetation corresponded to a soil-texture gradient which appeared to co-vary with soil depth and topography, both of which may infl uence soil moisture more strongly than texture alone. Nixon et al. (1987) described changes in woody vegetation along a topographic and soil gradient from an east Texas creek bottom to an upland. Soil texture and topography were likewise important factors in most ECS datasets (Table 6). Bridges and Orzell (1989) conducted a qualitative assessment that identified four subtypes of upland Longleaf Pine woodlands and three subtypes of wet savanna Longleaf Pine communities; ECS generally resolved two types in most LTAs: one on sandy soils and one on loam. Wet pine savannas lie mainly outside (south) of the ECS study region. Figure 5. A landscape profile showing characteristic topographic position and summarized soils and natural vegetation for seven ecological units (land-type phases) for the North Louisiana Clayey Hills. Names corresponding to the codes for the units are in Table 5. The unique code for each land-type phase indicates the ecological units of the hierarchy in which it is nested: the LTPs shown are in the Southeastern Mixed Forest Province (231), the South Central Arkansas Subsection (231Ea), and the North Louisiana Clayey Hills Landtype Association (231Ea.9). Species group names refer to the “master” combined ecological species groups of Van Kley et al. 2007; their closest equivalents from the current study are shown in Appendix 1. 18 Southeastern Naturalist Vol. 8, Special Issue 2 Table 6. Summary of the datasets used to develop ECS for the West Gulf Coastal Plain showing numbers of sample stands, LTAs covered, analyses used, selected correlations between ordinations and environmental factors, and the publication, report, or thesis in which the data were originally presented. The Red River Alluvial Plain and Alazan Wildlife Management Area ordinations were based on overstory; all others shown in the table used ground layer vegetation. P > 0.05 for all reported correlations. Locations of the forests sampled are shown in Figure 1. CCA and DCCA are described in Ter Braak and Smilaur (2002). NF = national forest; RD = ranger district. Dataset, location, Ordination axis (1, 2, or 3) and and year sampled Land-type association(s) Sites Type of analysis environmental factor correlations (r) Publication 1) Kisatchie NF: Calcascieu Ft. Polk Rolling Uplands; 47 DCA Topographic position (1) r = -0.84; Van Kley 1999b and Catahoula RD (1994) High Terrace Rolling Uplands Fire frequency (1) r = -0.91; Nitrogen (1) r = 0.51; Phosphorus (1) r = 0.64; Sand (2) r = 0.61; Clay (2) r = -0.47 2) Angelina and Davy Crockett Western Clayey Uplands; 51 Hybrid DCA/ Sand (1) r =0.78; Van Kley, unpubl. National Forests (1994) Eastern Clayey Uplands DCCA Clay (1) r = -0.58; data Calcium+ Magnesium (1) r = -0.57; Topographic position (2) r = 0.65 3) Kisatchie NF: Kisatchie RD Kisatchie Sandstone Hills 51 Hybrid DCA/ Topographic position (1) r = -0.83; Van Kley 1999a (1995) DCCA Sand (2) r = 0.63; Calcium (2) r = -0.47 4) Caddo Lake Wildlife Mgt. Alluvial River Floodplains 30 DCA Water depth during fl ood stage (1) Van Kley and Hine Area (1995) r = 0.86 1998 5) Kisatchie NF: Winn and Rolling Clayey Uplands; 39 DCA Topographic position (1) r = -0.76; Dehnisch 1998 Catahoula RD (1996) Winn Rolling Uplands Sand (2) r = -0.39; Clay (2) r = 0.49; Clay (3) r = 0.51 6) Sam Houston National San Jacinto Flatwoods; 54 DCA Topographic position (1) r = 0.36 Van Kley and Turner, Forest (1996) Raven Hills; Western Big (2) r =-0.55; Unpubl. data Thicket Elevation (2) r = -0.69; Slope steepness (1) r = 0.49; Sulfur (2) r = 0.40 2009 J.E. Van Kley and R.L. Turner 19 Table 6, continued. Dataset, location, Ordination axis (1, 2, or 3) and and year sampled Land-type association(s) Sites Type of analysis environmental factor correlations (r) Publication 7) Combined national forests LTAs listed for datasets 2 164, CCA Topographic Position (1) r = 0.45, Turner 1999 in Texas: All samples from and 6; Mayfl ower Uplands; (59 new) (2) r = -0.49; data-sets 2 & 6 plus 59 Sandy Uplands; Redlands; Depth to gray mottles (1) r = 0.48; samples mainly from Lignitic Uplands Sand (3) r = 0.48; pH (2) r = 0.36, (3) r = 0.34; Angelina and Sabine NF N (3) r =- 0.50; K (3) r = -0.32; (1995-1996) Mg (3) r = 0.33); S (3) r = 0.33; Latitude (3) r = -0.70; Longitude (1) r = 0.54, (3) r = -0.37; Mean low Temperature (1) r = -0.39; Mean Evaporation (1) r = -0.51 8) SFA Experimental Forest, Alluvial River fl oodplains 33, DCA High water mark height (1) r = -0.83; Mundorf 1998 Angelina, Davy Crockett, (21 new) % bare (litterless) soil surface (1) r = -0.82; and Kisatchie NF: incl. 12 Soil color: less “grayness" (1) r = 0.68; samples from other datasets (1996) Sand (1) r = 0.53; Clay (1) r = -0.62 9) Alazan Bayou Wildlife Alluvial River fl oodplains; 41 DCA Topographic position (1) r = 0.67; Quine 2000 Management Area (1999) Redlands Elevation; (1) r = 0.69; High water mark height (1) r = -0.79; Depth to gray mottles (1) r = 0.73 10) Kisatchie NF: Caney RD North Louisiana Clayey Hills; 50 NMS Topographic position (1) r = -0.53, Van Kley, previously (2002) Caney Lakes Rolling Uplands (2) r = -0.78; unpubl. data: Fire evidence (1) r = 0.57, (2) r = 0.74; current paper Depth to gray mottles (1) r = -0.76; Additional information: Table 3, Figure 2. 11) Kisatchie NF: Calcascieu, Red River Alluvial Plain 19 NMS Estimated fl ood regime (1) r = 0.47, Van Kley et al. 2007; Catahoula, and Kisatchie RD (3) r = 0.61; Van Kley, unpubl. plus selected non-USFS lands Soil drainage (3) r = 0.86; data (2004) Topographic Position; (3) r = 0.72 Total 462 20 Southeastern Naturalist Vol. 8, Special Issue 2 Most published descriptions of individual local plant communities also had counterparts in the ECS results. Dry uplands described by Marietta (1979), Marietta and Nixon (1983), and Ward and Nixon (1992) correspond to communities that develop on the arenic (and grossarenic) dry upland LTPs of Van Kley et al. 2007. Mesic forest communities of Nixon et al. (1980) and beech-hardwood forests of MacRoberts and MacRoberts (1997) typically occur on the ECS mesic slope and mesic stream bottom LTPs. Brooks et al. (1993) describe two types of “wet creek bottoms” for eastern Texas, a northern type and a southern one. Called “forested seeps” in ECS, and “Baygalls” by MacRoberts and MacRoberts (2004), those on the Caney District were of the northern type. Chambless and Nixon (1975), Nixon and Raines (1976), and Nixon et al. (1977) and describe bottomland forest communities which correspond to the vegetation component of ECS wet-mesic and seasonally fl ooded fl oodplain LTPs. A total of 137 land-type phases in 18 land-type associations are described in the current ECS field guide (Van Kley et al. 2007). However, the rigid nature of the National ECS hierarchy belies the occurrence of strikingly similar land-types and land-type phases across the different LTAs (see Fig. 4). The chief difference between many LTAs was the distribution of ecological types within them or the presence and absence of “unusual” types such as glades and prairies rather than major differences in the dominant types. Principal exceptions include the well-documented absence of Longleaf Pine communities in the northern and western part of the West Gulf coastal plain (Fig. 4) and the obvious restriction of most wetland LTPs to floodplain LTAs. Although some variation in species composition was associated with larger-scale geographic variables (Turner 1999), communities and ecotypes described in one LTA had close analogues in most others (see Fig. 4); the ECS data provide no strong support for the current LTA subdivisions. Of all ECS levels, the current LTAs with their strong geology emphasis, are the closest to being a single-component classification. Additional investigation may re-define (and possibly combine several) LTAs to be more relevant to documented differences in vegetation across the region. Recognizing this issue, Van Kley et al. (2007) describe 18 LTP-level “general ecological types” applicable across most of the West Gulf Coastal Plain that largely correspond to the ecosystem-type descriptions in the introduction to Volume 1of the Illustrated Flora of East Texas (Van Kley, in Diggs et al. 2006). ECS currently covers a large part of the West Gulf Coastal Plain at the LTP level, and is becoming a valuable conservation, management, and inventory tool. Its chief advantage over existing single-attribute classifications is that it integrates multiple ecosystem components into the classification thereby forming an expression of the “ecological potential” of the land: sites classified as the same ecological unit should respond in similar ways to most forms of management, support similar old-growth and late-successional plant communities, and support a similar array of seral communities and succession pathways. Nonetheless, vegetation-only 2009 J.E. Van Kley and R.L. Turner 21 classifications such as The Nature Conservancy's US National Vegetation Classification (Allard 1990, Anderson et al. 1998, Grossman et al. 1998) or the Texas plant community classification framework (Diamond et al. 1987) have an important role, especially in the number of finely-defined community types they resolve; cross-walking vegetation-based types with the ecological land units of ECS will enhance the usefulness both ECS and the vegetation classifications. In addition to being a management and inventory tool, ECS provides a framework for ecological research. Huston (2007) used ECS as a framework to describe bryophyte communities for the principal east Texas ecological types, and Fakhritidinova (2008) used molecular methods to describe community patterns of arbuscular mycrorrhizal fungi on three widespread native host plants across contrasting east Texas ecological types. A high future priority is generating LTP maps on US Forest service lands. Mapping allows ECS to reach its full potential as a basis for decision making and planning. Other needs include continued testing and refinement of existing ecological units and extending the geographic coverage of ECS. In particular, the Big Thicket National Preserve in southeastern Texas, an area for which there is rich preexisting data (Marks and Harcombe 1981, etc.) that could be tapped, forms a major gap in present ECS coverage. Describing possible succession pathways and additional components of the ecosystem such as bryophytes, soil microbes, insects, and mycorrhizal fungi for the ecological units will also greatly enhance the power of ECS. Acknowledgments Numerous individuals and organizations contributed to this large, multi-year project. We thank The Nature Conservancy, the US Forest Service, and Stephen F. Austin State University for multiple seasons of funding. Assistance was provided by numerous staff from The Nature Conservancy, the National Forests and Grasslands in Texas, Kisatchie National Forest, and other agencies. Ike McWhorter and Bill Bartush helped define the scope of this project and provided administrative support. Philip Hyatt, John Novosad, Susan Carr, David Moore, and Calvin Baker of Kisatchie National Forest provided administrative and logistical support. Guy Nesom assisted with site selection and data collection on Sam Houston National Forest. Kevin Mundorff, Mike Dehnisch, John Quine, and Matthew Welch collected and analyzed field data while pursuing graduate degrees at Stephen F. Austin State University. Dr. Larry Brown helped with plant identification. Raymond Dolezel’s aid in classifying soils was greatly appreciated. We thank Dr. Scott Beasley of the College of Forestry, Stephen F. Austin State University, for use of the GIS Laboratory and Dr. Paul Harcombe, Alan Weakley, and Jim Keys, for their helpful suggestions. Finally, we acknowledge Forest Supervisors Alan Newman, Danny Britt, Ronnie Raum, Lynn Neff, Fred Salinas, and Gretta Boley for their support of ECS. Literature Cited Allard, D.J. 1990. Southeastern United States Ecological Community Classification. Interim report, Version 1.2. The Nature Conservancy, Southeast Regional Office, Chapel Hill, NC. 96 pp. 22 Southeastern Naturalist Vol. 8, Special Issue 2 Anderson, M., P. Bourgeron, M.T. Bryer, R. Crawford, L. Engelking, D. Faber-Langendoen, M. Gallyoun, K. 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Eastern Region Land and Resource Management Planning Handbook. USDA Forest Service, Washington, DC. Handbook 1909.21 USDA Forest Service. 1996. Revised land and resource management plan, National Forests and Grasslands in Texas, Management Bulletin R8-MB 70-D. Washington, DC. USDA Forest Service. 1997. Draft Environmental Impact Statement, Kisatchie National Forest. USDA Forest Service Southern Region, Washington, DC. Van Kley, J.E., and G.R. Parker. 1993. An ecological classification system for the Central Hardwoods Region: The Hoosier National Forest. In Proceedings of the Ninth Annual Central Hardwoods Conference, Purdue University, West Lafayette, IN. USDA Forest Service, St. Paul, MN. Technical Report NC-161. Van Kley, J.E., and D.N. Hine. 1998. The wetland vegetation of Caddo Lake. Texas Journal of Science 50: 67–290. Van Kley, J.E. 1999a. The vegetation of the Kisatchie Sandstone Hills, Louisiana. Castanea 64:64–80. Van Kley, J.E. 1999b. The vegetation of the High Terrace Rolling Uplands, Louisiana. Castanea 64:318–336. Van Kley, J.E., R.L. Turner, L.S. Smith, and R.E. Evans. 2007. Ecological classification system for the national forests and adjacent areas of the West Gulf Coastal Plain: 2nd approximation. The Nature Conservancy and Stephen F. Austin State University, Nacogdoches, TX. 379 pp. Van Lear, D.H., and S.M. Jones. 1987. An example of site classification in the southeastern coastal plain based on vegetation and land type. Southern Journal of Applied Forestry 11(1):23–28. Ward, J.R., and E.S. Nixon. 1992. Woody vegetation of the dry, sandy uplands of eastern Texas. Texas Journal of Science 44(3):283–294. Williams, R., and L.M. Smith. 1995. A survey and description of the natural plant communities of the Kisatchie National Forest: Caney District. Louisiana Natural Heritage Program, Louisiana Department of Wildlife and Fisheries, Baton Rouge, LA. 26 Southeastern Naturalist Vol. 8, Special Issue 2 Appendix 1. A synoptic table derived from a TWINSPAN classification of 50 samples and 340 species from the Caney Ranger District of Kisatchie National Forest. Values = mean occurrence rank (frequency %). Only species with mean occurrence >1.8 in at least one community are displayed. SOU= Shortleaf Pine-oak-hickory uplands, LSU = Loblolly Pine-Sweetgum uplands, MLS = mesic lower slopes and stream bottoms, WMF = wet-mesic fl oodplains, WMT = wet-fl oodplain terraces, FS = forested seeps, and SWP = Baldcypress swamp. Species group names in parenthesis indicate the “master” ecological species group(s) of Van Kley et al. 2007 to which the Appendix 1 group is closest. Species SOU LSU MLS WMF WMT FS SWP Species of upland pine oak-hickory communities (“Tragia + Schizachyrium groups”) Carya texana Buckl. 2.5 (64) 1.9 (43) 0.7 (17) - - - - Desmodium paniculatum (L.) DC. 1.9 (64) 1.1 (43) - - - - - Dichanthelium acuminatum (Sw.) 2.0 (64) 0.3 (14) - 0.8 (25) - - Gould & C.A. Clark Euphorbia corollata L. 3.5 (91) 0.7 (29) 0.1 (6) - - - - Galactia volubilis (L.) Britt. 2.0 (64) 0.4 (29) - - - - - Hypericum hypericoides (L.) Crantz 3.1 (100) 0.4 (14) 0.5 (33) 0.8 (25) - - - Lespedeza violacea (L.) Pers. 1.5 (45) - - - - - - Pinus echinata P. Mill. 3.0 (82) 0.1 (14) 0.2 (6) - - - - Pteridium aquilinum (L.) Kuhn 1.8 (45) - 0.7 (28) - - - - Quercus stellata Wangenh. 1.8 (45) - - - - - - Rhus copallinum L. 2.7 (91) 0.9 (43) 0.1 (6) - - - - Vaccinium arboreum Marsh. 3.9 (100) 2.3 (86) 0.8 (39) - - - - Vernonia texana (Gray) Small 1.9 (64) - - - - - - Viburnum rufidulum Raf. 2.8 (91) 1.1 (43) 0.9 (44) - - - - Species of upland and mesic sites (“Callicarpa group”) Aesculus pavia L. 2.4 (73) 0.7 (29) 1.1 (56) - - - - Celtis laevigata Willd. 0.4 (18) 2.0 (71) 0.5 (17) - - - - Callicarpa americana L. 3.9 (100) 3.4 (100) 3.6 (94) 1.4 (75) - 3.7 (100) - Chionanthus virginicus L. 2.6 (82) 1.7 (71) 1.7 (67) - - 2.3 (100) - 2009 J.E. Van Kley and R.L. Turner 27 Species SOU LSU MLS WMF WMT FS SWP Clitoria mariana L. 2.4 (73) 2.6 (86) 0.8 (39) - - - - Cornus fl orida L. 2.9 (100) 3.3 (86) 2.4 (89) 0.4 (25) - 1.7 (67) - Desmodium obtusum (Muhl ex. Willd) DC 3.0 (100) 3.0 (100) 1.9 (61) 0.4 (13) - - - Dioscorea quaternata J.F. Gmel. 0.4 (18) 0.9 (29) 2.2 (72) - - - - Fraxinus americana L. 1.1 (45) 0.4 (29) 2.2 (83) 0.3 (25) - 1.0 (33) - Frangula caroliniana (Walt.) Gray 1.0 (45) 4.0 (100) 1.9 (78) 0.3 (13) - 0.7 (33) - Gelsemium sempervirens St.-Hil. 2.5 (73) 2.7 (86) 0.5 (17) - - - - Hamamelis virginiana L. 0.7 (27) 1.0 (29) 3.8 (100) 0.4 (13) - 1.3 (33 - Ostrya virginiana (P. Mill.) K. Koch 1.1 (27) 1.1 (43) 3.2 (94) - - 1.3 (33 - Prunus serotina Ehrh. 3.8 (100) 3.6 (100) 3.1 (89) 0.3 (13) - 0.7 (33) - Quercus alba L. 4.0 (100) 3.4 (100) 3.6 (94) - - 3.3 (100) - Quercus falcata Michx. 3.1 (82) 3.6 (100) 1.5 (56) 1.1 (25) - 0.7 (33) - Sassafras albidum (Nutt.) Nees 2.4 (64) 3.1 (100) 3.1 (94) 0.3 (13) - - - Scleria oligantha Michx. 3.3 (100) 2.6 (57) 1.9 (56) - - 0.3 (33) - Smilax bona-nox L. 3.5 (91) 1.7 (43) 1.3 (44) 0.6 (25) - 1.0 (33) - Smilax smallii Morong 2.0 (64) 1.0 (29) 1.0 (39) 0.3 (13) - - - Vaccinium virgatum Ait. 3.8 (100) 2.9 (86) 2.2 (56) 0.1 (130 - - - Viburnum dentatum L. 3.1 (91) 0.7 (29) 1.7 (56) - - 1.0 (33) - Vitis aestivalis Michx. 2.5 (91) 3.4 (100) 2.7 (94) 2.1 (88) - - - Wide-ranging species (“Chasmanthium + Mitchella groups”) Acer rubrum L. 3.6 (91) 4.7 (100) 3.7 (94) 1.3 (50) 3.5 (100) 3.3 (100) 1.0 (100) Berchemia scandens (Hill) K. Koch 0.9 (45) 2.0 (57) 1.1 (39) 2.6 (88) - 1.7 (67) - Bignonia capreolata L. 1.8 (64) 1.7 (57) 3.2 (100 4.1 (100) 2.0 (50) 3.3 (100) - Chasmanthium sessilifl orum (Poir.) Yates 4.5 (100) 4.6 (100) 2.7 (78) 0.1 (13) - - - Chasmanthium laxum (L.) Yates 0.3 (9) 0.3 (14) 1.8 (44) 3.1 (88) 3.5 (100) 3.7 (100) - Dichanthelium dichotomum (L.) Gould 1.5 (55) 0.1 (14) 0.4 (17) 2.0 (63) 0.5 (50) 2.7 (67) - 28 Southeastern Naturalist Vol. 8, Special Issue 2 Species SOU LSU MLS WMF WMT FS SWP Dichanthelium boscii (Poir.) Gould & 3.2 (82) 2.1 (57) 3.1 (89) 3.4 (88) - 1.3 (33) - C.A. Clark Diospyros virginiana L. 1.4 (82) 2.0 (57) 0.8 (33) 0.5 (25) 3.0 (100) - - Ilex opaca Ait. 1.2 (55) 2.9 (100) 3.4 (94) 2.6 (75) 2.5 (100) 3.7 (100) - Liquidambar styracifl ua L. 3.3 (82) 2.9 (71) 1.6 (67) 2.4 (75) 3.5 (100) 2.3 (67) - Lonicera japonica Thunb. 0.5 (18) 2.4 (86) 1.6 (50) 1.3 (38) - 2.3 (67) - Wide-ranging species (“Chasmanthium + Mitchella groups”) Mitchella repens L. 1.8 (55) 2.4 (86) 2.2 (67) 4.1 (100) 2.5 (100) 2.7 (67) - Nyssa sylvatica Marsh. 3.1 (91) 3.3 (100) 2.9 (94) 2.8 (100) 3.0 (100) 2.3 (100) - Parthenocissus quinquefolia (L.) Planch. 3.8 (91) 4.7 (100) 4.4 (100) 2.0 (63) - 2.0 (100) - Pinus taeda L. 1.2 (36) 1.9 (57) 1.7 (61) - 3.5 (100) 2.7 (67) - Polystichum acrostichoides (Michx.) Schott 0.1 (9) 0.9 (43) 2.6 (72) 0.5 (13) - - - Quercus nigra L. 2.9 (73) 4.3 (100) 3.4 (89) 2.9 (75) 4.0 (100) 3.0 (100) - Rubus argutus Link 0.8 (27) 1.4 (43) 0.7 (22) 2.6 (75) 1.0 (50) 2.0 (67) - Smilax glauca Walt. 3.5 (100) 3.6 (100) 3.4 (100) 2.6 (88) 2.5 (100) 2.3 (67) - Smilax rotundifolia L. 1.9 (55) 2.1 (57) 2.3 (67) 3.3 (88) 3.5 (100) 4.0 (100) - Toxicodendron radicans (L.) Kuntze 3.9 (91) 4.9 (100) 4.0 (100) 4.4 (100) 1.5 (50) 2.3 (67) - Trachelospermum difforme (Walt.) Gray 0.3 (9) 0.3 (29) 0.3 (11) 2.5 (88) 1.5 (50) - - Ulmus alata Michx. 1.7 (64) 3.1 (100) 2.7 (83) 1.8 (75) - 0.7 (33) - Vaccinium elliottii Chapman 0.1 (9) 1.7 (57) 1.0 (33) 1.0 (38) 3.5 (100) - - Vitis rotundifolia Michx. 4.5 (100) 4.4 (100) 4.3 (100 3.9 (100) 1.0 (50) 4.0 (100) - Species of mesic, wet-mesic, and forested seep sites (“Arisaema group”) Acer barbatum Michx. - 0.6 (29) 1.9 (50) 0.9 (25) - - - Arisaema triphyllum (L.) Schott - 1.4 (57) 1.7 (33) 0.9 (38) - 3.7 (100) -- Athyrium filix-femina (L.) Roth - 0.3 (14) 0.6 (17) 0.8 (38) - 4.7 (100) - Carpinus caroliniana Walt. - 1.6 (43) 2.2 (61) 3.6 (100) 1.0 (50) 1.7 (67) - Carex abscondita Mackenzie - 0.1 (14) 1.5 (39) 4.0 (88) - - - 2009 J.E. Van Kley and R.L. Turner 29 Species SOU LSU MLS WMF WMT FS SWP Euonymus americana L. - 0.3 (14) 2.5 (89) 1.1 (38) - 1.0 (33) - Fagus grandifolia Ehrh. - 1.7 (71) 2.2 (67) 0.5 (25) - 2.0 (67) - Ligustrum sinense Lour. - 0.3 (14) 0.1 (6) 1.6 (88) - 2.3 (100) - Quercus laurifolia Michx. - 0.3 (14) 0.3 (11) - 4.5 (100) 1.0 (33) - Quercus michauxii Nutt. - 1.1 (29) 0.5 (17) 1.8 (63) 1.5 (50) 0.3 (33) - Species of fl oodplains and wetlands (“Bignonia + Justicia groups”) Arundinaria gigantea (Walt.) Muhl. - - 0.3 (11) 2.0 (63) - - - Bidens aristosa (Michx.) Britt. - - 0.2 (6) 1.5 (75) - - 5.0 (100) Boehmeria cylindrica (L.) Sw. - - 0.3 (17) 2.6 (75) 1.5 (50) 2.0 (67) 4.0 (100) Brunnichia ovata (Walt.) Shinners - - - 2.4 (75) 2.0 (50) - 2.0 (100) Carex debilis Michx. - - 1.1 (28) 1.9 (50) 1.5 (50) 4.3 (100) - Carex fl accosperma Dewey - - 0.3 (17) 2.0 (63) 1.5 (50) - - Carex joorii Bailey - - 0.2 (6) - 4.5 (100) - 4.0 (100) Carex louisianica Bailey 0.4 (9) - 0.2 (6) 3.8 (100) 2.5 (100) - 1.0 (100) Carya glabra (P. Mill.) Sweet - - 1.7 (39) 2.1 (50) - - - Cephalanthus occidentalis L. - - - 1.3 (63) - 2.0 (67) 5.0 (100) Commelina virginica L. - - 0.2 (6) 2.9 (100) - - - Itea virginica L. - - 0.2 (6) 0.4 (25) - 3.3 (100) 4.0 (100) Justicia ovata (Walt.) Lindau - - 0.5 (17) 1.8 (63) - - - Leersia oryzoides (L.) Sw. - - 0.2 (6) 1.9 (50) - - - Leersia virginica Willd. - - 0.6 (22) 2.0 (63) - 1.7 (67) - Lycopus rubellus Moench - - 0.1 (6) 1.0 (38) - 2.0 (67) 4.0 (100) Quercus phellos L. - - 0.2 (6) 1.4 (38) 2.0 (50) - - Saururus cernuus L. - - 0.1 (6) 2.1 (88) 2.5 (100) 2.0 (67) 2.0 (100) Styrax americanus Lam. - - - 0.5 (25) 3.5 (100) - 4.0 (100) Species of forested seeps ('”Osmunda group”) Magnolia virginiana L. - - 0.1 (6) - 1.0 (50) 3.7 (100) - Osmunda cinnamomea L. - - - - - 2.6 (100) - 30 Southeastern Naturalist Vol. 8, Special Issue 2 Species SOU LSU MLS WMF WMT FS SWP Viburnum nudum L. - - - - - 4.0 (100) - Woodwardia areolata (L.) T. Moore - - 0.1 (6) - - 4.7 (100) - Wetland species (“Ceratophyllum group”) Hydrolea unifl ora Raf. - - - - - - 2.0 (100) Lemna valdiviana Phil. - - - - - - 4.0 (100) Ludwigia glandulosa Walt. - - - - - - 2.0 (100) Planera aquatica J.F. Gmel. - - - - - - 3.0 (100) Proserpinaca palustris L. - - - - - - 4.0 (100)