Bottomland Oak Research Articles

Using LiDAR Data to Estimate Biomass in Afforested Bottomland Oak Sites in the Southern United States

Abstract The extent of bottomland hardwood forests in the Lower Mississippi Alluvial Valley (LMAV) has diminished, and federal programs like the Conservation Reserve Program provide incentives to afforest marginal agricultural areas with oaks to provide ecosystem services. Remote sensing technologies, like light detection and ranging (LiDAR), can be used to estimate biomass of these stands to potentially allow landowners to take advantage of carbon markets, but data are expensive to collect. Therefore, we determined whether freely available low-density LiDAR data could capture variability in tree- and stand-level characteristics in the LMAV, including aboveground biomass. We found that multiple regression LiDAR models captured more variability in tree-level than stand-level parameters and including soil type generally improved models. Model r2 values predicting tree and stand parameters including tree height, height to the live crown, quadratic mean diameter, crown area, trees per hectare, stand basal area, and stand biomass ranged from 0.34 to 0.82 and root mean square percent error (RMSPE) ranged from 7% to 36%. Specifically, models for stand biomass had an RMSE of about 19 Mg/ha or about 19% of mean values across sites. Therefore, freely available LiDAR data was useful in evaluating afforested bottomland oak sites for tree- and stand-level structural components in the LMAV.

Influence of Soil Saturation on Survival and Growth of Bottomland Oaks Six and Fourteen Years after Planting

Bottomland oak restoration projects have been marginally successful because professionals often recommend conventional tree-planting procedures that prove problematic in hydric soils. A reliable method of matching oak species to bottomland sites is needed prior to planting. To address the issue, we planted 8 different species of oak seedlings into previously farmed hydric soil in West Tennessee in 2004. We took measurements after 6 and 14 growing seasons to ascertain survival and growth trends based on soil mottling and the depth to gleyed matrix. The later measurements mostly supported early findings that Quercus lyrata (Overcup Oak), Q. texana (Nuttall Oak), Q. palustris (Pin Oak), and Q. phellos (Willow Oak) are most tolerant of poorly drained soil and that as soil drainage improves, species diversity may expand.

Acorn Weevil (Coleoptera: Curculionidae) Predation Dynamics in a Mississippi Bottomland Hardwood Forest

Curculio and Conotrachelus weevils (Coleoptera: Curculionidae) can render the majority of North American Quercus spp. acorn crops nonviable, thereby reducing food resources for wildlife and limiting opportunities for seedling establishment. Acorn predation by weevils at the individual tree level can be influenced by many factors, and research specifically investigating acorn predation by weevils in seasonally flooded bottomland oak forests is lacking. We placed cone emergence traps in a periodically flooded forest on the Sam D. Hamilton Noxubee National Wildlife Refuge near Brooksville, Mississippi to obtain weevil population parameter estimates, record emergence phenologies, and identify variables that may aid in understanding tree-to-tree variability in acorn predation rates. Forty-three Curculio weevils representing five species emerged from mid-August through early November, and 56% of those captured emerged over an 11-day period in mid-September. Sixty-four Conotrachelus weevils representing two species emerged from mid-August through late November and occurred at nearly twice the density of Curculio weevils. The exotic Asiatic oak weevil, Crytepistomus castaneus, a minor defoliator, emerged from August through early November. We also identified Quercus density, specifically the proportion of oaks that immediately neighbor the host tree, as a potentially important explanatory variable of acorn predation by weevils at the tree level in bottomland forest habitats.

Relationships between Leaf Anatomy and Physiological Functioning of Southern US Oak Species Differing in Flood Tolerance

Research Highlights: Bottomland oaks receive less attention than upland species, however their adaptations to flooding and summer water stress will extend our understanding of the oak genus and links between physiology and leaf anatomy. Background and objectives: Determining links between leaf anatomy and physiology can aid in parameterizing dynamic global vegetation models for oak systems, therefore we sought to (1) compare leaf anatomic, nutrient, and physiological parameters for bottomland oaks differing in flood tolerance, (2) determine correlations across parameters and determine which anatomic and nutrient parameters best predict photosynthetic capacity metrics, and (3) compare these data with reported literature values for oaks across the globe. Materials and Methods: We measured CO2 response curves (A/Ci) on leaves from Nuttall, Shumard, swamp chestnut, water and white oak seedlings planted in the Southeastern United States (US) and estimated stomatal size and density, epidermal cell size, vein density, leaf mass per area (LMA) and nitrogen (N) concentrations. Principal component analysis among these leaf anatomic and nutrient parameters was used to determine the best predictors of photosynthetic parameters including Rubisco-limited carboxylation rate (VCmax) and electron transport limited carboxylation rate (Jmax). Results: We found that although physiological parameters were similar, flood-tolerant oaks had lower leaf N concentrations and larger, more infrequent stomata than less flood-tolerant species. Leaf epidermal properties were correlated with N concentrations and a principal component capturing this correlation as well as principal components correlated with mesophyll conductance and leaf carbon concentrations were found to best explain variation in VCmax and Jmax. These Southeastern US oaks exhibited similar leaf physiological parameters and LMA as oaks reported in the literature but differed in leaf epidermal and stomatal properties as well as leaf N concentrations increasing the reported range of these parameters within the oak genus. Conclusions: Therefore, leaf anatomy and nutrient parameters as opposed to physiology differed across flood tolerance and between bottomland oaks and broader literature values.

Seasonal physiology and growth of bottomland oaks of differing planting stocks in afforestation sites on the U.S. Gulf Coastal Plain

Hurricane Katrina caused large losses of bottomland hardwood forests on the Gulf Coastal Plain. Heavy‐seeded species such as oaks (Quercus) generally require direct planting for restoration after such losses. However, evaluating the performance of various oak planting stocks using biometric data alone can be challenging due to their slow juvenile growth and belowground carbon allocation. Our study goals were to evaluate physiological parameters including photosynthesis, stomatal conductance, and water‐use efficiency (WUE) and their correlation with annual height growth to determine differences in functional performance and drought tolerance between seedling types and whether physiology can predict height growth. Monthly growing season gas exchange measurements were made on two oak species (Quercus texana and Quercus shumardii) and three planting stocks (bare root, conventional containerized, large containerized [LC]) planted on two sites in coastal Mississippi. We found that photosynthesis decreased throughout the growing season while stomatal conductances increased leading to decreasing WUEs in all seedling types. Physiological parameters differed across planting stocks but not species. Particularly, LC seedlings exhibited greater WUEs and sensitivity to vapor pressure deficit (VPD) suggesting increased moisture stress compared with other planting stocks. Across seedling types, photosynthesis, stomatal sensitivity to VPD, and seasonal changes in intrinsic WUE measured in year one of the study were significantly correlated with year two, but not year one height growth, suggesting belowground allocation of carbon during the first growing season. In total, these results highlight the use of physiological measurements in selecting successful planting stocks for various site conditions.

Chloride concentration distribution under oak hedgerow: an indicator of the water-uptake zone of tree roots?

Aims In agroforestry systems, root activity of trees may either reduce nutrient leaching beneath neighboring crops or compete with them. A previous study reveals high chloride (Cl) accumulation in the soil under a bottomland oak hedgerow in western France. Our study tests whether Cl can be used as an indicator of the spatial extent of tree root activity.

Extension Efforts to Restore Bottomland Oaks Requires Knowledge of Both Trees and Soil

Bottomland oak restoration projects have been marginally successful because professionals often recommend conventional tree planting procedures that prove problematic in saturated soils. A reliable method of matching oak species to bottomland sites is needed prior to planting. In the study reported here, bottomland oaks were matched to hydric soils based on soil mottling. The findings suggest that as soil drainage improves, species diversity expands. Natural Resource Extension professionals should consider "active" methods of direct technical assistance and field demonstrations and "passive" methods of newsletters, publications, and pamphlets, as delivery methods to educate both landowners and professionals about this subject.

Nitrate attenuation in soil and shallow groundwater under a bottomland hedgerow in a European farming landscape

AbstractIn many agricultural areas, hedgerows give rise to strong expectations of reducing the inputs of excess nitrate to the groundwater and rivers. This study aims to analyse the spatial and seasonal influences of a hedgerow on nitrate dynamics in the soil and groundwater. Nitrate (NO3−) and chloride (Cl−) concentrations were measured with spatially dense sampling in the unsaturated soil and in the groundwater along a transect intersecting a bottomland oak (Quercus rubor) hedgerow after the growing season and during the dormant season. We explain NO3− dynamics by using Cl− as an index of tree‐root extension and water transfer. At the end of the growing season, NO3− is entirely absorbed by the trees over a large and deep volume corresponding to the rooting zone, where, in contrast Cl− is highly concentrated due to root exclusion. However, these observed patterns in the soil have no influence on the deep groundwater composition at this season. During the dormant season, water transfer processes feeding the shallow groundwater layer are different upslope and downslope from the hedgerow in relation to the thickness of the unsaturated zone. Upslope, the shallow groundwater is fed by rainwater infiltration through the soil which favours Cl− dilution. Right under the hedge and downslope, the rapid ascent of the groundwater near the ground surface prevents rainwater input and Cl− dilution. Under the hedgerow the highest concentrations of Cl− coincide with the absence of NO3− in the shallow groundwater layer and with high concentrations of dissolved organic carbon. The absence of NO3− during the dormant season seems to be due to denitrification in the hedgerow rooting zone when it is rapidly saturated by groundwater. Copyright © 2011 John Wiley & Sons, Ltd.

Silviculture and Forest Ecology

Abstract 2Over the past several decades, federal incentive programs have encouraged the restoration of bottomland forests throughout the West Gulf Coastal Plain (WGCP) and the Lower Mississippi Alluvial Valley (LMAV). Programs such as the Conservation Reserve (CRP) and Wetlands Reserve (WRP) Programs have been marginally successful (Stanturf et al. 2001). Foresters and contractors often follow conventional tree planting procedures that are well established for upland sites, but prove problematic in bottomlands. High water tables, soil drainage and compaction, overland flooding and diverse soil properties make species selection difficult. Slight changes in topography and soil structure often have a dramatic effect on survival and growth of planted oak seedlings (Hodges and Schweitzer 1979). This project documented the survival and growth of six-year old seedlings that were established on a bottomland site in 2004, located at the West Tennessee Research and Education Center, Jackson, Tennessee. The purpose was to determine how soil drainage as indicated by mottling (specifically, the point of 50 percent gray color throughout the soil profile) affects the survival and growth of bottomland oak species. The findings suggest that practitioners plant Nuttall, pin and overcup oaks in poorly drained soils. As the drainage improves, begin mixing in willow oak. In the best drained soils (if they exist), finish by including water, swamp chestnut, swamp white, Shumard, cherrybark and bur oaks. Potential species diversity should expand as the soil drainage improves.

High chloride concentrations in the soil and groundwater under an oak hedge in the West of France: an indicator of evapotranspiration and water movement

AbstractChloride is a major anion in soil water and its concentration rises essentially as a function of evapotranspiration. Compared to herbaceous vegetation, high transpiration rates are measured for isolated trees, shelterbelts or hedgerows. This article deals with the influence of a tree hedge on the soil and groundwater Cl− concentrations and the possibility of using Cl− as an indicator of transpiration and water movements near the tree rows. Cl− concentrations were measured over 1 year at different depths in the unsaturated zone and in the groundwater along a transect intersecting a bottomland oak hedge. We observed a strong spatial heterogeneity of Cl− concentrations, with very high values up to 2 g l−1 in the unsaturated zone and 1·2 g l−1 in the upper part of the groundwater. This contrasts with the low and homogeneous concentrations (60–70 mg l−1) in the deeper part of the groundwater. Cl− accumulation in the unsaturated zone at the end of the vegetation season allows us to identify the active root zone extension of trees. In winter, upslope of the tree row, downwards leaching partly renews the soil solution in the root zone, while the slow water movement under the trees or farther downslope results in Cl− accumulation and leads to a salinization of the soil and groundwater. This salinization is of the same order as experimental conditions produce negative effects on oak seedlings. The measurement of Cl− concentrations in the unsaturated zone under tree rows at the end of the vegetation season would indicate whether certain topographic, pedological or climatic conditions are likely to favour a strong salinization of the soil, as observed in the present study. Copyright © 2009 John Wiley & Sons, Ltd.

A Stand-Development Approach to Oak Afforestation in the Lower Mississippi Alluvial Valley

Abstract Oak (Quercus spp.) afforestation in the Lower Mississippi Alluvial Valley has involved planting 1-year-old bareroot seedlings on a relatively wide spacing in single-species stands or planting light-seeded species with oaks to form mixed-species stands. In the former case, the developing single-species stands have limited future management options because they do not provide structures that favor quality wildlife habitat or quality sawtimber production. In the latter case, species mixtures are being planted with little knowledge of subsequent stand development, leading to an inability to predict future stand composition for management purposes. In this article, we present a system to determine bottomland tree planting mixtures that will create single-cohort, mixed-species stands with a component of high-quality bottomland oak. Using individual species ecological life-history characteristics, such as early height growth pattern, relative twig diameter and durability, and developmental patterns in natural stands, bottomland species are rated for their ability to provide beneficial training effects that will lead to the development of quality oak boles. Incorporating such a system to determine species value in mixtures should provide an increased number of future options to meet explicit management objectives and promote improved restoration of bottomland hardwood ecosystems.

Cherrybark oak stump sprout survival and development five years following plantation thinning in the lower Mississippi alluvial valley, USA

Cherrybark oak (Quercus pagoda Raf.) stump sprouts were studied for 5 years in a 30-year-old plantation thinned to 70–75% stocking (light thinning) and 45–50% stocking (heavy thinning). Sprouting success, survival, number of sprouts per stump, and sprout height differed little between thinning treatments throughout the 5-year study period. Pre-harvest tree d.b.h. also had no influence on sprout survival and development. A 2-year drought reduced survival and may have influenced sprout development. Sprout clump survival dropped from 90% 1 year following thinning to 46% 3 years after thinning. Although sprout height averaged 337 cm 5 years after thinning, annual sprout growth decreased from 166 cm the first year after thinning to 33 cm in each of the last 2 growing seasons. Results indicated that bottomland hardwood regeneration evaluation models may underestimate the potential of oak stump sprouts to contribute to pre-harvest regeneration assessments. Further study in the role of stump sprouts to regenerate bottomland oak species is needed.

Epicormic Branches Affect Lumber Grade and Value in Willow Oak

Abstract A case study was conducted in a 50-yr-old bottomland oak stand in central Alabama to investigate the relationship between epicormic branches and lumber grade and value in willow oak (Quercus phellos L.). The stand had been thinned from below 7–10 yr earlier, resulting in a wide variety of epicormic branch conditions on the residual trees. A sample of 41 willow oak trees was selected before the stand was clearcut in late 1991. All merchantable logs in each tree were graded prior to felling. Average dbh of sampled trees was 19.1 in. Each tree averaged 9.5 epicormic branches on the sawlog portion of the bole. From these 41 trees, a random sample of 57 logs (31 butt logs and 26 upper logs) was shipped to a sawmill where they were sawn into lumber and graded. Epicormic branching had a large detrimental effect on log grade of individual trees. In general, as few as five epicormic branches somewhat evenly distributed on a 16 ft log was enough to cause a reduction in log grade. More importantly, defects caused by epicormic branches had a serious effect on lumber grade, particularly in the higher grades. Over 50% of the lumber volume that would have been graded as either First and Seconds or Select in the absence of epicormic branches was downgraded to No. 1 Common or below due to defects caused by epicormic branches. Based on lumber prices prevailing at the time of the study, defects caused by epicormic branches resulted in a 13% reduction in the value of the lumber produced in the final harvest. South. J. Appl. For.25(3):136–141.

Survival and Growth of Seedlings of Four Bottomland Oak Species in Response to Increases in Flooding and Salinity

Abstract Four oak species representing a range of flood tolerance were chronically (simulating sea level rise) and acutely (simulating hurricane storm surge) exposed to increased flooding and salinity in a complete factorial experiment. Survival, growth, and final biomass were measured to assess differential species' responses. No Nuttall or overcup oak seedlings died when flooded with fresh water, but 10% of the swamp chestnut and 35% of the water oaks died. Floodwater salinities of 2 and 6 g L-1 resulted in mortality of all seedlings of all four species. Watering with 2 g L-1 saline water did not cause any mortality although leaf browning was evident in all species. Overcup oak seedlings were the most tolerant to watering with 6 g L-1 saline water (100% survival), while the other three species had high mortality. Increased salinity, both in watered and flooded conditions, generally resulted in decreased diameter growth and decreased root and shoot biomass. Short-term increases in salinity (simulated storm surge) resulted in total mortality of flooded seedlings, while drained seedlings recovered and leafed out the following spring. Results indicate that these bottomland oak species would be seriously affected by increased flooding and salinity from either hurricane storm surges or sea level rise. For. Sci. 44(4):618-624.

Effects of flood duration and season on germination of black, cherrybark, northern red, and water oak acorns

Effects of flood duration (0, 10, 20, and 30 days) and season (winter and spring) on acorn germination were tested for two upland oaks [black and northern red oak (Quercus velutina Lam. and Q. rubra L.)] and two bottomland oaks [cherrybark and water oak (Q. pagoda Raf. and Q. nigra L.)]. Acorns were stratified for 30 days before flooding at a depth of 15 cm along the edge of a small pond. After flooding, acorns were sowed in sand-filled plastic cups and germinated for 40 days. Flood duration and season strongly affected radicle and epicotyl emergence of the upland oaks, but effects were generally limited to spring flooding. Embryo axes of the upland oak acorns were severely damaged with as little as 10 days of spring flooding. Almost no epicotyls developed, but radicles developed from the connective tissues between embryo axes and the cotyledons of many acorns. Spring flooding also significantly increased the percentage of decayed acorns for the upland oaks. In contrast, germination of the bottomland oaks was slightly improved by flooding during both seasons. Results demonstrated that the effects of flooding on the distribution of species within bottomlands can begin with seed storage and germination.

Silvicultural systems for southern bottomland hardwood forests

Silvicultural systems integrate both regeneration and intermediate operations in an orderly process for managing forest stands. The clearcutting method of regeneration favors the development of species that are moderately intolerant to intolerant of shade. In fact, clearcutting is the most proven and widely used method of successfully regenerating bottomland oak species in the South. The seed-tree method of regeneration favors the establishment of light-seeded species. Mechanical soil scarification may be necessary if the desired species requires bare mineral soil for establishment. The shelterwood method of regeneration can provide for the development of heavy-seeded species, but has produced highly variable results with southern bottomland oaks. The single-tree selection method of regeneration favors the development of shade-tolerant species. When single-tree selection is applied repeatedly to stands containing commercially valuable shade-intolerant species, composition will gradually shift to less-valuable, more-tolerant species. Consequently, the single-tree selection method of regeneration is not recommended for any commercially valuable bottomland hardwood tree species. Group selection, in its strictest application, creates only small openings that usually fail to allow sufficient light to the forest floor for satisfactory establishment and development of shade-intolerant bottomland species. Patch cutting, a combination of uneven-aged (group selection) and even-aged (clearcutting) silviculture, designed to create larger openings, has been successfully used to produce an uneven-aged stand that consists of many small, irregularly shaped, even-aged groups. Silvicultural systems should include a planned program of intermediate operations designed to enhance the growth and development of those species favored during the regeneration process. Improvement cutting and commercial thinning are increasingly common in southern bottomland hardwood forests. Other partial cuttings employed today in bottomland hardwood forests typically involve some form of crop-tree release. Specific recommendations for the selection of silvicultural systems are presented for the eight most important species groups found in southern bottomland hardwood forests.

Physiological, morphological and growth responses to rhizosphere hypoxia by seedlings of North American bottomland oaks

Certaines especes de chenes du sud des Etats-Unis sont distribuees le long de gradients topographiques dans les plaines inondables. Du fait des differences dans l'aeration des sols associees a ces gradients, nous avons teste l'hypothese que ces especes presentent des resistances differentes a l'hypoxie rhizospherique. Quatre especes occupant differents sites des plaines inondables (Quercus lyrata, Q laurifolia, Q phellos, et Q nigra) ont ete soumises a deux experimentations pour evaluer les reponses des plantes au debut et a la fin de la premiere saison. Dans les deux etudes, la tolerance a l'hypoxie a ete estimee par la mesure d'echanges gazeux, l'accumulation de biomasse, et la croissance de la pousse et de la racine. Des differences de resistance a l'hypoxie de la rhizosphere ont ete mises en evidence et les consequences sur la distribution des especes dans les plaines inondables ont ete discutees.

Direct Seeding of Bottomland Oaks in Oklahoma

Abstract Competition control with a broad spectrum herbicide prior to planting and placement of a fertilizer tablet near the seed spot failed to improve establishment or height growth of direct seeded water, willow, or Shumard oaks on a bottomland site in southeastern Oklahoma. The percentage of seed spots stocked with a living seedling exceeded 35%, or 1460 seedlings/ha (590/ac) given the initial spacing of 1 x 2.4 m (3.2 x 8 ft). This success is generally comparable to results obtained in more favorable environments in the Mississippi Valley. The fertilizer treatment, applied as a single fertilizer tablet placed near the seeded spots at the time of seeding, reduced stocking by 12-15% during an especially stressful growing season. Bare-root, 1-0, water/willow oak seedlings planted for comparision exhibited 80-90% survival. South. J. Appl. For. 15(1):17-22.

Establishment of Bottomland Oak Plantations on the Yazoo National Wildlife Refuge Complex

Abstract Stocking, height and diameter growth, and invasion of both herbaceous and woody plant species are reported for 5 direct seeded and 5 planted seedling stands of bottomland oaks, all of which were between 4 and 8 years old. Stocking was generally higher in the planted seedling stands. Both height and diameter growth were substantially higher in the planted seedling stands. Low stocking and poor growth, especially for the direct seeded stands, was associated with medium-textured soils and a heavy cover of Johnson grass (Sorghum halepense) and goldenrod (Solidago altissima). Invasion of woody species was heavily dominated by light-seeded species, and was highest in stands close to mature trees. South. J. Appl. For. 14(4):206-210.