West Gulf Coastal Plain Research Articles

Identifying Functional Groups of Trees in West Gulf Coast Forests (USA): A Tree-Ring Approach

A dendroclimatic study of important tree species in the west Gulf Coastal Plain region, USA, was conducted to evaluate how climate affects tree radial growth in this southeasternmost section of the Eastern Deciduous Forest/Southern Evergreen Forest. We established an east–west transect from western Louisiana to central Texas that crossed the western range limits of each of 16 species and developed a network of 104 annual tree ring-width chronologies from 38 sites. Of the 104 chronologies, 99 series from the genera Pinus, Quercus, and Fagus were analyzed using rotated principal components analysis (RPCA). The RPCA revealed the presence of three robust phylogenetic signals in the tree-ring patterns, which partitioned the data into the Pinus species (PISP), the oak species in the black oak subgenus Erythrobalanus (QUBO), and the oak species in the white oak subgenus Leucobalanus (QUWO). The Fagus chronologies (FAGR) also loaded most highly with the QUWO series, resulting in a combined QUWO/FAGR factor. This partitioning occurred even though tree species within each phylogenetic group came from contrasting xeric and mesic sites and, in the case of the QUWO/FAGR factor, from different genera. Only in the xeric western range limits of the transect did site location begin to override the phylogenetic groupings. Consequently, responses to climate based on genetics appeared to be more important than ecological and site characteristics in determining the tree-ring patterns of the sampled species overall. We tested this hypothesis by independently modeling the dendroclimate signals in the tree-ring chronologies using monthly precipitation and maximum temperature data. The resulting climate correlation functions were subjected to RPCA as before. As we did so, the same phylogenetic groups emerged. All of the chronologies were drought sensitive. However, the phylogenetic differences in climate response were related to differences in the timing of the peak monthly responses to climate and to the differing patterns of climate response in the months prior to the current growing season. The findings of this study indicate that there is an underlying organizing principle based on genetics that determines how certain phylogenetic groups of trees respond to climate in a way that is largely independent of the site environment. At a coarse level, these phylogenetic distinctions persist even at the most stressed sites near tree range limits, though distinctions within genera start to break down. These findings therefore suggest functional groupings of tree species, which can be used in vegetation/climate models that attempt to predict realistically how such forests will respond to future climate changes.

Response of direct seeded Pinus Palustris and herbaceous vegetation to fertilization, burning, and pine straw harvesting

Fallen pine straw (needles) is a renewable biological resource valued as a mulch in horticulture and for landscaping. However, its harvesting may have detrimental long-term effects on forest soils and vegetation. To compare current pine straw harvesting practices, a randomized complete block split-plot study was established during 1990 in a 34-year-old stand of direct-seeded longleaf pine ( Pinus palustris Mill.) that had been prescribed burned every 3 years since establishment. Practices included no fertilizer or applications of 50 kg ha −1 N and 56 kg ha −1 P in both 1991 and 1997 as the main plot treatment. The subplot management practices were prescribed burning and the mechanical baling and removal of straw. Pine straw harvesting eventually removed the forest floor and increased soil bulk density by 1993. The growth of longleaf pine was not significantly affected by treatments over a 5-year period from early 1991 to early 1996. Herbaceous plant productivity was determined in July 1997, and there were shifts in plant dominance associated with treatments. Fertilization increased current-year herbaceous plant biomass by 59% on an oven-dried weight basis. Among management practices, prescribed burning in early 1991, 1994, and 1997, with two annual straw harvests in early 1992 and 1993, resulted in the greatest herbaceous plant yields by July 1997. The lowest yields in 1997 were on plots that were either annually harvested six times or had been left untreated for over 6 years. Burning every 3 years favored pinehill bluestem ( Schizachyrium scoparium var. divergens (Hack.) Gould), which is often the dominant grass on longleaf uplands in the West Gulf Coastal Plain of the U.S.A. Raking straw shifts herbaceous plant dominance to other grasses, principally the panicums ( Dicanthelium spp. and Panicum spp.). The cessation of management favored bracken fern ( Pteridium aquilinum var. pseudocaudatum (Clute) Heller).

Effects of habitat and growing season fires on resprouting of shrubs in longleaf pine savannas

The effects of habitat and timing of growing season fires on resprouting of shrubs were studied in second-growth longleaf pine savannas of the west Gulf coastal plain in the southeastern United States. Within the headwaters of three different drainages of the Calcasieu River in the Kisatchie National Forest in western Louisiana, replicated permanent transects were established that extended from xeric upland longleaf pine savannas into downslope hydric seepage savannas. All shrubs were mapped and tagged, and numbers of stems were counted prior to any fires. Replicated prescribed fires were set early (June) and late (August) during the 1990 growing season; maximum fire temperatures were measured within both upland and seepage habitats within each transect. Shrubs were relocated; stems were recensused two and twelve months after the fires. At least some shrubs of all species resprouted from underground organs; none regenerated solely from seed banks in the soil. There was no reduction in total numbers of stems one year after fires compared to before fires, either in the upland or in seepage savannas. In addition, there was no reduction in total numbers of stems one year after early or late growing season fires. Fire-related mortality was restricted to small shrubs (< 18 stems) and was not associated with high fire temperatures. The rate of resprouting varied among species and between habitats. Resprouting occurred more rapidly in seepage than upland savannas, but more resprouts were produced in upland than seepage savannas one year after fires. In contrast to other upland species, Vaccinium arboreum and V. elliottii delayed resprouting more than two months following fire. Stems of Rhus copallina and Pyrus arbutifolia, species with long rhizomes, increased more after fires in June than fires in August. We suggest that growing season fires may block further recruitment of shrubs into longleaf pine savannas, but reduction in numbers of large shrubs may require additional management.

Loblolly Pine Plantation Development is Influenced by Site Preparation and Soils in the West Gulf Coastal Plain

Abstract Productivity of upland loblolly pine (Pinus taeda L.) plantations was studied under seven site preparation treatments and five soil classes, with and without fertilizer, in the West Gulf Coastal Plain. Generally, the chop-burn-harrow and shear-windrow-harrow treatments resulted in themost basal area (ave. 112 ft²/ac), but the chop-burn-harrow treatment produced the most fiber (2,109 ft³/ac) after 12 growing seasons. Harrowing as an additional treatment after chopping-and-burning increased productivity by 394 ft³/ac over the chop-burn treatment. The leastproductive treatments were underplant-inject and shear-windrow. Generally, basal area per acre was comparatively high on the silty, slowly permeable clay, and very slowly permeable clay soils (ave. 105 ft ²/ac). Two of the soils, silty and slowly permeable clay, had comparatively highvolume production (ave. 1,878 ft³/ac). The least productive sites had gravelly subsoils. Generally, phosphorus fertilization did not influence pine productivity. South. J. Appl. For. 13(1):17-21.

Basal-area projection equations for thinned natural even-aged forest stands

Several existing basal-area projection equations, including one with a thinning term, were compared by using data from a long-term thinning study in natural even-aged stands of loblolly (Pinustaeda L.) and shortleaf pine (Pinusechinata Mill.) in the West Gulf Coastal Plain. The model with the thinning term was no better than existing models with no thinning variable. These results prompted a search to improve the projection models that include thinning. A general technique for introducing a thinning variable into basal-area projection models was developed. This study found that the efficacy of adding a thinning term depends upon the accuracy requirements of the user.

Phosphorus sorption curves for evaluating phosphorus requirements of loblolly pine (pinus taeda)

Abstract Bray P2, Mehlich 1, and Mehlich 2 methods identified soils on which loblolly pine would respond to P fertilizer in a greenhouse study using six soils from the West Gulf Coastal Plain. The P extracted by any of the three methods did not correlate with growth on unfertilized soils or to the maximum amount of response when P was applied. Phosphorus sorption curves were used to estimate the amount of P in soil solution. The concentration of P in roots and tops was proportional to the log of the amount of P in solution. For 90% of maximum dry weight of loblolly seedlings, about 0.22 mg/liter of P in soil solution was necessary. The phosphorus sorption method has the potential of predicting the P requirements of loblolly pine, but field testing is necessary.

Stand and Site Conditions Related to Southern Pine Beetle Susceptibility

Abstract Stand/site data from infested stands were compared with those from the general forest. Findings supported earlier research relating high basal area, high stand density, high proportion of pines, reduced radial growth rate, low soil pH, and high site index to increased southern pine beetle activity in the West Gulf Coastal Plain. Also, increased understory vegetation and thicker bark of potential host trees were found to favor beetle attack. Discriminant models were derived from data obtained from infested and general stand (baseline) plots and can be used to rank forest stands as to susceptibility to southern pine beetle attack. Forest Sci. 25:656-664.

Slash Pine Response to Nitrogen and Phosphorus on Imperfectly Drained Soil of the West Gulf Coastal Plain

AbstractTotal dry weight and nutrient content of 1‐year‐old slash pines (Pinus elliottii var. elliottii Engelm.) responded to combinations of N and P in a pot study with imperfectly drained Coastal Plain soil. Application of either nutrient alone resulted in no growth response. A marked response was obtained with applications equivalent to 50 kg of P and 168 kg of N/ha. Maximum growth as determined by regression analysis was obtained with applications equivalent to 124 kg of P and 232 kg of N/ha.Uptake of individual nutrients increased with N and P levels, but response patterns differed. Nitrogen, calcium, and magnesium uptake corresponded closely to dry‐matter accumulation of seedlings, while P uptake was independent of dry weight. Percentage recovery of applied P decreased with increased P fertilization but improved with addition of N. Recovery of N increased with amount applied and was not affected by P.

Southern Mixed Hardwood Forest: Climax in the Southeastern Coastal Plain, U.S.A.

DESCRIPTION OF AREA The Coastal Plain in the southeastern tier of states is divided into several major portions, namely the Sea Island Section, the Floridian Section, the East Gulf Coastal Plain, the Mississippi Alluvial Plain, and the West Gulf Coastal Plain (Fenneman 1938). This study dealt with forests that occur on uplands of the Sea Island Section and on the East and West Gulf Coastal Plains. A distinct fall line separates the Sea Island Section, which drains into the Atlantic, from the adjacent Piedmont, and the Coastal Plain itself is comprised of a series of northeasterly-southwesterly oriented belts, the two lowermost of which consist of terraces of Pleistocene age. The East and West Gulf Coastal Plains, separated by the Mississippi Alluvial Plain, are very similar to each other in general plan. They are broadly belted, have a somewhat indistinct demarcation at the inner boundary, and their combined Pleistocene terraces form a narrower strip than do those on the Atlantic slope. This investigation was concerned with an area that corresponds approximately to the Southeastern Ever-

Application of coefficients of transmissibility and storage to regional problems in the Houston District, Texas

The Houston District, as the term is used in this paper, comprises an area between the Trinity and Brazos rivers in Harris County and parts of Montgomery, Waller, and Fort Bend counties, Texas. It consists of a plain of low relief that lies not far above sea‐level, and is a part of the West Gulf Coastal Plain. A part of the District is shown in Figure 1.Large quantities of ground‐water are pumped in the Houston District from a succession of beds of sand that occur between 300 and 1,900 feet below the surface. These sands are interbedded with relatively impermeable clays. The formations range in age from Miocene to Recent and were deposited during several cycles of marine and continental deposition. They may be classified into several zones which are predominantly clay or predominantly sand, but in which the individual beds at most horizons can not be traced very far. Most of the beds interfinger and grade into one another laterally and vertically in short distances, the thinner beds in many places changing character or pinching out within a few hundred feet. The formations dip to the southeastward, the dip ranging from about 35 feet to the mile in the older formations to about 20 feet to the mile in the younger. In the outcrop‐areas of the formations, and for considerable distances down the dip, the sediments are in general dominantly sandy. Far to the southeastward, in the direction of the Gulf, clay predominates.