Tree-level Growth of Four Oak Species in a Bottomland Hardwood Plantation: Implications for Silvicultural Treatments

A 41-year-old bottomland hardwood plantation experiment located in southeastern Arkansas was revisited in 2017 to evaluate basal area increment (BAI) of four oak species [cherrybark oak (Quercus pagoda Raf.), swamp chestnut oak (Q. michauxii Nutt.), Nuttall oak (Q. texana Buckl.), and water oak (Q. nigra L.)] planted in monoculture in relation with species, spacing, thinning, and neighborhood competition. Species had a significant effect on BAI (P = 0.04), with cherrybark oak and Nuttall oak demonstrating the greatest (21.5 ± 2.5 cm2 year−1) and lowest (12.7 ± 2.9 cm2 year−1) growth rates, respectively, whereas BAI declined significantly with increasing competition (P = 0.03). However, rates of growth decline with competition did not differ between species (P > 0.05 for competition × species term), and thinning and spacing treatments had no effect on BAI (P > 0.05). We recommend that repetitive thinning, rather than a single thinning, would be appropriate to maintain a positive impact on oak growth. Managing stand density would not only provide opportunities for improving timber production, but also would enhance ecological benefits (e.g., wildlife habitat) through diversification of structure within monoculture plantations. Study Implications: This research supports the general concept that stand density management may effectively alleviate tree-level stresses on bottomland oak species related to intra-specific competition while improving their growth. In particular, repeated thinning could help reduce growth stagnation and maintain tree-level vigor. Repeated tending entries would also create multiple opportunities to simultaneously improve timber production and enhance ecological benefits in bottomland oak monocultures. Finally, the findings of this study confirm the importance of correctly matching species to site when artificially regenerating bottomland oaks.

A Random-Parameter Height-Dbh Model for Cherrybark Oak

A random-parameter model was used to relate total height to diameter at breast height (dbh) for cherrybark oak (Quercus pagoda Raf.). Data were obtained from 561 trees located in 50 stands occurring on bottomland hardwood sites in East Texas, near the western extent of the cherrybarkoak natural range. Mixed-model estimation techniques were used to fit fixed-effects parameters to the height-dbh relationship for cherrybark oak, with random-effects parameters representing sample stands from which tree data were obtained. The fixed-effect parameter estimates can be used topredict average cherrybark oak height for a given dbh in the region from which the data were obtained. Because random parameters associated with stands were used in the data-fitting process, the models can be calibrated to fit new stands by obtaining measurements to fit appropriate randomparameters for that stand. This calibration improves height predictions for individual stands while requiring less data than would the development of a completely new height prediction model for that stand. South. J. Appl. For. 29(1):22–26.

Nursery Practices Influence Seedling Morphology, Field Performance, and Cost Efficiency of Containerized Cherrybark Oak

To quantify effects of nursery practices on seedling cost and performance, cherrybark oaks (Quercus pagoda L.) were grown in three container sizes (170, 650, or 1,250 cm3) with or without fertilization and then planted Dec. 1995 at a site near Milledgeville, GA, with or without removal of container soil. Initial size, biomass, and leaf area of seedlings grown in medium and large containers were up to twice those grown in small containers, and they were greater with versus without fertilization. Price efficiency (stem volume divided by estimated nursery price of 1,000 seedlings) was greatest for medium and large containers with soil removed and hypothetically reused. Differences in stem diameter and height due to container size and fertilization continued to diverge through the fifth year after planting. Fifth-year yield (stem volume × proportionate survival of 1,000 planted seedlings) increased 104, 56, and 31% with increasing container size and with fertilization and soil removal, respectively. Cost efficiency (fifth-year yield divided by costs compounded 5 years at 5% interest) was greatest for medium and large containers with soil removed. Joint comparisons of nursery costs, planting costs, and field performance for different seedling stock types provide an objective approach for prioritizing cultural treatments in forestry. South. J. Appl. For. 28(3):152–162.

Assessing the Use of Chopper Herbicide for Establishing Hardwood Plantations on a Cutover Site

Successful establishment of hardwood plantations requires effective weed management. Mechanical weed control is inefficient, and few herbicides are available for use in hardwood plantations. In an effort to identify new chemical control options, the potential of imazapyr (Chopper herbicide) for site preparation prior to planting three common southern hardwood species was assessed. Twelve site preparation treatments were tested using Chopper applied at four rates and three timings prior to planting. Each site preparation rate and time pairing was repeated under two postplant herbicide regimes—directed glyphosate (Accord herbicide) sprays designed to maintain weed-free conditions and a single broadcast sulfometuron methyl (Oust herbicide) treatment designed to test a potential operational sequencing of Chopper site preparation followed by herbaceous weed control. Although results must be evaluated in the context of a single site and set of environmental conditions, they demonstrate the utility of Chopper herbicide for site preparation prior to planting hardwoods. For sycamore (Platanus occidentalis L.)and sweetgum (Liquidambar styraciflua L.),site preparation before the end of July with Chopper rates up to 64 oz/ac improved survival and growth over postplant treatments alone. For later season applications, sycamore and sweetgum were more sensitive to the Chopper site preparation rate. For Oct. site preparation, Chopper rates above 16 oz/ac adversely affected planted sycamore seedlings and rates greater than 32 oz/ac adversely effected planted sweetgum seedlings. Cherrybark oak (Quercus pagoda Raf.)performed best using the highest Chopper rate of 64 oz/ac regardless of timing. South. J. Appl. For. 28(3):163–170.

Soil Scarification Effects on Oak Reproduction in Two Mixed-Oak Bottomland Stands of Southern Illinois

This study investigated whether soil scarification during the presence of oak mast could increase oak seedling establishment and decrease poison ivy cover in two mixed-oak bottomland stands that lacked adequate advanced oak reproduction. Study sites were located along the Saline River in southern Illinois and designated as Cherrybark Bottoms, with an overstory dominated by cherrybark oak (Quercus pagoda Raf.), and Post Oak Flat, which contained an even mixture of post oak (Q. stellata Wang.) and cherrybark oak. Scarification was completed in November of 1999 using a small farm tractor with a pull-behind field disk to incorporate acorns into the soil. One growing season after scarification, Cherrybark Bottoms had significantly more oak seedlings in the scarified plots (7,243 ha-1) than in controls (453 ha-1). Likewise, Post Oak Flat had a significantly greater density of oak seedlings in scarified plots (8,715 ha-1) when compared to control plots (679 ha-1). In addition, scarification decreased poison ivy [Toxicodendron radicans (L.) Kuntze] cover in both stands. Results suggest that, in the presence of abundant acorns, scarification may increase the establishment of new oak seedlings in mixed-oak bottomland forests. South. J. Appl. For. 27(3):164–171.