Michael D. Cain

Secondary forest succession following reproduction cutting on the Upper Coastal Plain of southeastern Arkansas, USA

Abstract To contribute to an understanding of forest management on secondary forest succession, we conducted vegetation surveys in a chronosequence of pine stands ranging in age from 1 to 59 years. Adjacent areas were compared at 1, 7, 12, and 17 years following two reproduction cutting methods (clearcuts or pine seed-tree cuts); a 59-year-old pine stand that was periodically thinned was also included to represent conditions before reproduction cutting. Because average or better natural loblolly and shortleaf pine (Pinus taeda L. and P. echinata Mill.) seed crops coincided with the planned site disturbances, pines dominated the seedling-size classes at 1 and 7 years after reproduction cutting, the sapling-size classes at 7, 12, and 17 years after reproduction cutting, and the small- and large-tree size classes at 12, 17, and 59 years after reproduction cutting. For seedling-size classes, three measures of woody plant diversity (Shannon’s (H′), Simpson’s (D), and evenness (e) indices) tended to increase from 1 to 12 years after reproduction cutting. In the sapling-size classes, H′ and D diversity indices were highest at 17 years and lowest at 59 years after reproduction cutting. For small-tree size classes, H′, and D were highest at 7 years and lowest at 12 years after reproduction cutting. Across all but the large-tree size classes, woody species richness peaked 7 years after reproduction cutting. Naturally regenerated pines achieved complete crown closure by 17 years after reproduction cutting; consequently, the presence of shade-tolerant woody plants increased in the understory, and shade-intolerant herbaceous plants disappeared from the forest floor.

Hardwood Snag Fragmentation in a Pine-oak Forest of Southeastern Arkansas

AssTR.KT.-Because snags are important to forest wildlife as breeding, roosting and foraging sites, resource managers who wish to maintain this component in forest stands need to be aware of snag fragmentation rates. Measurements were taken in uneven-aged pinehardwood stands in southeastern Arkansas to determine fragmentation rates for hardwood snags 2 to 6 yr after stem injection with herbicides. Crown and bole condition of snags were also assessed. Pinus echinata Mill. and E! taeda L. were the dominant overstory components and were undisturbed. Q~ercus spp. accounted for 91% of hardwoods >25 cm dbh. Since small diameter snags deteriorated first, snag diameter distributions changed from unevensized to even-sized structure as time since mortality increased. Within 3 yr of injection, 57% of snag boles had broken below crown height. Number of wildlife cavities per snag increased with time since mortality. At 6 yr after injection, 44% of residual snags had evidence of wildlife cavities. Less than 50% of hardwoods <25 cm dbh were still standing 5 yr after herbicide injection.

Viability of litter-stored Pinus taeda L. seeds after simulated prescribed winter burns

Stratified loblolly pine (Pinus taeda L.) seeds were placed at three depths in a reconstructed forest floor and subjected to simulated prescribed winter burns. Within the forest floor, pine seeds were placed at the L/upper-F interface, upper-F/lower-F interface, and lower-F/mineral-soil interface. Wind was generated by electric box-fans. Seeds that survived the burns were transferred to moist sand flats for 30-day germination tests. About 96% of seeds placed at the two upper layers in the forest floor were either destroyed by the fires or failed to germinate. Germinative capacity of seeds placed at the lower-F/mineral-soil interface averaged 79% as compared to 97% for unburned control seeds.

Growth expectations from alternative thinning regimes and prescribed burning in naturally regenerated loblolly-shortleaf pine stands through age 20

Abstract Pine growth was monitored for 14 years after mechanically strip-thinning a dense, naturally regenerated, even-aged stand of 6-year-old loblolly pines (Pinus taeda L.) and shortleaf pines (Pinus echinata Mill.) that averaged 41000 trees per hectare in southeastern Arkansas, USA. Prescribed winter burns were conducted biennially between ages 9 and 20 years. A commercial thinning during the 17th growing season left a residual stocking of either 19.5 m2 ha−1 or 494 crop trees ha−1 in merchantable-sized ( > 9.0 cm dbh) pines on plots that were precommercially thinned and on plots that were not. Precommercial thinning enhanced pine growth in total height and in diameter at breast height (dbh, taken at 1.37 m) through stand age 20 years. At age 20, present net value (PNV) averaged highest on plots that were precommercially thinned at age 6 then commercially thinned to 494 crop trees per hectare after 16 years because of increased production in sawtimber (trees over 24 cm dbh). The second highest PNV at age 20 was on unmanaged control plots because no costs were incurred for precommercial thinning, hardwood injection, prescribed burning, or timber sale administration. Within each thinning treatment, pine dbh growth decreased in the 18th and 20th year relative to an increase in the degree of crown scorch from prescribed winter burns that were conducted after 17 and 19 years, respectively.

Hardwoods on pine sites: competition or antagonistic symbiosis

Abstract Early development of natural loblolly (Pinus taeda L.) and shortleaf pine (Pinus echinata Mill.) regeneration was monitored in two research studies and two research demonstrations between 1980 and 1989 in southern Arkansas. Site preparation and hardwood control incorporated the use of herbicides, mechanical treatments, or prescribed burning to facilitate the establishment of natural pine regeneration in accordance with two reproduction cutting methods — selection and shelterwood — on upland pine sites. All treatments resulted in satisfactory density and per cent stocking of pine regeneration within the first 3 years. Growth of that regeneration excelled in one research study and on one demonstration area, but was impaired on the other two areas, apparently by an overabundance of herbaceous vegetation. Where an understory and midstory hardwood cover preceded the pine reproduction cuts, herbaceous vegetation was nearly absent and subsequent growth of the pine regeneration was excellent.

Fire effects on germination of seeds from Rhus and Rubus: competitors to pine during natural regeneration.

Throughout the southeastern United States, Rhus and Rubus species are common associates of the southern pines on a wide array of upland site and stand conditions. Because of their ability to overrun disturbed sites, these species are categorized as competitors to pine during stand regeneration. Since prescribed burning is often used for site preparation in advance of pine regeneration, this study investigated the effect of fire on the germination of seeds from three pine competitors (Rubus argutus Link, Rhus copallina L. and Rhus glabra L.). During dormant-season burns, sumac seeds were located 45 cm above litter, within the F layer of a reconstructed forest floor, and at the interface of the forest floor and mineral soil. During growing-season burns, fresh blackberry fruits were placed at heights of 0, 15, 30, and 45 cm above the surface litter of a reconstructed forest floor. In subsequent germination tests, sumac seeds from within the F layer of burned litter had significantly higher germination rates for smooth sumac (31%) and shining sumac (42%) as compared to unburned control seeds (1–5%). In general, germination rates for sumac seeds placed in the air or on mineral soil during burning were no better than control seeds. Seeds from blackberry fruits that were located at heights of 15, 30, and 45 cm had germination rates that were comparable to unburned control seeds (18%), but seeds from fruits placed on the litter during burning had <1% germination. Results suggest that sumac seed germination may be enhanced by the heat from prescribed burning, whereas blackberry seeds showed more germination response to multiple germination cycles which indicated a potential for long-term storage in the soil seed bank.

Woody and herbaceous competition effects on the growth of naturally regenerated loblolly and shortleaf pines through 11 years

Four levels of vegetative competition were used to quantify the growth of loblolly and shortleaf pines (Pinus taeda L. and P. echinata Mill.) in naturally regenerated, even-aged stands on the Upper Coastal Plain of southeastern Arkansas, USA. Treatments included: (1) no competition control, (2) woody competition control, (3) herbaceous competition control, and (4) total control of nonpine vegetation. After pines became established from natural seeding, herbicides were used to control herbaceous plants for 4 consecutive years and woody plants for 5 consecutive years. Even though 89% of crop pines on untreated check plots were free-to-grow 11 years after establishment, crop pines on vegetation control plots were larger (P<0.001) in mean dbh, total height, and volume per tree. From age 5 through 11 years, crop pine diameter growth increased on woody control plots and decreased on herbaceous control plots because of hardwood competition in the latter treatment. At age 11, crop pine volume production averaged 207 m3/ha on total control plots, 158 m3/ha on herbaceous control plots, 130 m3/ha on woody control plots, and 102 m3/ha on untreated check plots.

Five-year field comparison of naturally regenerated Pinus taeda L. to genetically improved container stock, with and without release

A field study compared genetically improved, container-grown loblolly pine (Pinus taeda L.) seedlings to naturally established loblolly seedlings on a cutover pine site in southern Arkansas, USA. Pines on 50% of all plots were released from woody and herbaceous competition within a 61 cm radius of each tree stem. Woody competition was controlled by hand cutting for 5 consecutive years and herbaceous competition was controlled with herbicides (sulfometuron methyl and glyphosate) for 4 consecutive years. Competition control increased 5-year survival by 21–23% for natural and planted seedlings, respectively, with no statistically significant difference between the two regeneration techniques. Five years after field establishment, planted pines averaged 85% more volume than naturally established pines. Nevertheless, greater volume gains (551–688%) were achieved within regeneration techniques, as a result of competition control, than were achieved between the two regeneration techniques.