Allan E. Tiarks

Impacts of intensive forestry on early rotation trends in site carbon pools in the southeastern US

Abstract The effects of different silvicultural practices on site, especially soil, carbon (C) pools are still poorly known. We studied changes in site C pools during the first 5 years following harvesting and conversion of two extensively managed pine-hardwood stands to intensively managed loblolly pine plantations. One study site was located on the lower Atlantic Coastal Plain in North Carolina (NC) and another on the Gulf Coastal Plain in Louisiana (La). Four different harvesting-disturbance regimes were applied: stem only harvest (SO), whole tree harvest (WT), whole tree harvest with forest floor removal (WTFF), and full amelioration, i.e. whole tree harvest, disking, bedding and fertilization (FA; only in NC). Each harvesting-disturbance regime plot was split and one-half received annual herbicide treatments while the other half received no herbicide treatments. In NC, soil C decreased slightly with WT, and increased with FA, otherwise no significant changes were detected. In La, there was a consistent decrease in soil C content from the pre-harvest value in all cases where herbicides were applied. All treatments caused a reduction in the forest floor C pool in NC. In La, the most intensive treatments also resulted in a decrease in the forest floor C, but to a smaller extent. In contrast, there was no net change in forest floor C with the SO and WT treatments, even though significant amounts of logging slash were added to the forest floor at harvest in the SO plots and not in the WT. Herbicide treatment clearly decreased the C pool of hardwoods and understory, and more than doubled that of planted pines. Carbon accumulation in the planted pines was similar for trees growing in the SO, WT, and WTFF treatments on both the LA and NC sites. The full amelioration treatment (only applied at the NC site) led to a significant increase in C sequestration by the planted pine component. Due to a large amount of voluntary pines, total 5-year pine C pool was highest on the non-herbicided intensive management plots on the NC site, however. The differing response patterns of soil and forest floor C pools between the two sites may be due to their differing drainage-summer rainfall regimes. Our results suggest that while poor drainage-wet summer conditions may be impeding carbon loss from the soil component it may be accelerating the rate of decomposition of the forest floor and slash on the soil surface.

Pinus taeda L. response to fertilization, herbaceous plant control, and woody plant control

Abstract On an intensively prepared site, a complete fertilizer applied at planting, and control of herbaceous and woody plants for the first 4 years, increased Pinus taeda L. volume at age 5 to 25.9 m3/ha compared to 11.8 m3/ha without the treatments. The fertilizer and competition control factors affected pine growth independently of each other, and so their effects are additive. Herbaceous plant control was the most effective treatment, increasing pine volume by 63%. Declining dry weights of herbaceous plant material indicated that pine was dominant by age 6, so more responses from herbaceous plant control are not expected. Woody plant control did not significantly increase pine volume until the fifth year because the intensive site preparation retarded the development of the woody competition. The fertilizer contained nitrogen, phosphorus, and potassium, but analysis of pine foliage indicates phosphorus was the element causing the response of pine to fertilizer. By the sixth season, the herbaceous and woody plant material contained 31% of the nitrogen and potassium applied as fertilizer. The competing material also contained 7% of the phosphorus applied in the fertilizer. This showed that competitors can be major utilizers of fertilizer applied to pines.

Fertilization, weed control, and pine litter influence loblolly pine stem productivity and root development

Following site preparation, three cultural treatments and three open-pollinated loblolly pine (Pinus taeda L.) families were studied on a gently sloping Beauregard silt loam in central Louisiana. The treatments were: (1) fertilization (either broadcast application of 177 kg N and 151 kg P/ha or none); (2) herbicide application (either broadcast application of herbicides during the first through third growing seasons, and felling of a few, scattered volunteer hardwood trees greater than 2.5 cm dbh during the third growing season or none); and (3) litter application (either broadcast application of 37 Mg/ha (oven-dried weight) of pine straw over the plots to form a 10 to 15 cm layer or none). The subplot treatment was planting stock, where in November 1988, 28-week-old container-grown loblolly pine seedlings from three open-pollinated families were randomly assigned to planting locations. Through five growing seasons, fertilization and weed control with herbicides resulted in the greatest loblolly pine productivity, but the use of herbicides severely reduced other vegetation. Applying litter, which was less effective than herbicides as a weed control treatment, increased the presence of blackberry (Rubus spp.) when herbicides were not applied. Applying litter resulted in a decrease and fertilization resulted in an increase in the number and length of live lateral roots. Soil temperature was reduced by litter application. Treatment responses were not influenced by loblolly pine family.

Establishment treatments affect the relationships among nutrition, productivity and competing vegetation of loblolly pine saplings on a Gulf Coastal Plain site

After cultural treatments such as site preparation, release and fertilization, changes in the supply of mineral nutrients relative to each other and shifts in the composition of vegetation may have a delayed effect on the nutrition, carbon partitioning and growth of forest trees. This study was conducted to evaluate the influence of early management options that control vegetation and fertility on the nutrition and productivity of a young loblolly pine (Pinus taeda L.) plantation on a phosphorus-deficient site in the Gulf Coastal Plain. Two levels each of herbicide application, fertilization and litter addition were applied in a factorial arrangement to three open-pollinated families of newly planted loblolly pine seedlings. Competing vegetation was evaluated after three growing seasons, loblolly pine nutrition and tannin synthesis were evaluated after four growing seasons and loblolly pine productivity was quantified after five growing seasons. Fertilization and herbicide application increased the growth and decreased the foliar tannin concentration of loblolly pine. Herbicide application also increased the potassium concentration of loblolly pine foliage. A negative correlation between foliar tannin and potassium concentrations was found on plots that were fertilized with nitrogen and phosphorus. On southern pine sites that are fertilized with phosphorus, the accelerated growth of planted pine and invading vegetation may create new nutrient limitations. Where phosphorus is limiting, however, nutrient utilization may not be great enough for new deficiencies to develop. Loblolly pine stand productivity and foliar nutrient concentrations were affected by genetic family and the foliar calcium and magnesium concentrations of loblolly pine families responded differently to the establishment treatments. We also found that the establishment treatments influenced the occurrence of herbaceous and woody competitors. We hypothesize that corresponding treatment effects on exchangeable cation concentrations and pH of the soil were caused by changes in vegetation.

Condensed Tannins in Southern Pines and Their Interactions with the Ecosystem

Condensed tannins extracted from the foliage of selected southern pine species were found to be predominately prodelphinidin polymers of 14 to 18 flavanoid units, whereas, tannins from phloem were mostly procyanidins of 8 to 11 units. These chemical characteristics indicate that the tannins from the different plant parts may have different biological activities in the ecosystem. Slash pine (Pinus elliottii Engelmann var. elliottii) foliage contained an average of 49 percent more tannin than loblolly (Pinus taeda L.) or longleaf (Pinus palustris Miller) pine foliage. Tannin concentration in the phloem did not seem to be related to site factors that control the rate of pine growth, but tannin concentration in the foliage increased by 30 percent as the site quality decreased from good to poor. Application of phosphorus fertilizer decreased the concentration of tannin in the foliage of loblolly pine from 110 to 85 g/kg. Concentrations of tannins in the foliage increased in the spring of the first year of the lifespan of needles, followed by a period of stability, and then another increase in concentration the second spring. In the months prior to senescence, tannins were lost from the foliage, either by leaching or by chemical transformations. The importance of tannins in nutrient cycling suggests that research on the fate of tannins released into the ecosystem needs to be intensified.

Sequential Extraction of Condensed Tannins from Pine Litter at Different Stages of Decomposition

Sequential extraction procedures using methanol or methanol followed by acetone-water (1:1) (v/v) were used to measure condensed tannins in pine litter. Tannins in the extracts and residues were quantified by the amount of anthocyanidins formed in n-butanol-HCl. The amount of tannin extracted varied with the solvent and the number of extractions, but the total amount of tannin measured in extracts and residues was not significantly different for any of the sequences. An extraction sequence consisting of two methanol extractions followed by one acetone-water extraction was selected to measure tannins in pine litter. When the anthocyanidin procedure was used to measure condensed tannins from southern pine foliage, 5 percent HC1 in the n-butanol was the optimal acid concentration. The yield of anthocyanidin was increased by 62 percent when 12 mg/L of ferrous iron was added to the n-butanol-HCl. The sequential extraction method was used to follow the loss of tannin from litter bags containing decomposing shortleaf pine (Pinus echinata Mill.) senescent foliage. After one season, 16 percent of the original 73.9 g/kg of tannin was detectable. After two seasons, the litter contained 5.8 g/kg (8 percent) of the original tannin content.

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.

Loblolly and slash pine height and diameter are related to soil drainage in winter on poorly drained silt loams

Soil drainage characteristics in winter and the heights and diameters of 10-year-old loblolly and slash pines (Pinus taeda L. and P. elliottii Engelm. var. elliottii) were measured on three poorly-drained silt loam sites that had been bedded, furrowed, or disked before planting. Quadratic response functions were used to determine the relationship between depth to water table or volume of drained soil in winter and mean tree height or diameter. These quadratic response functions (species × height or diameter: drainage characteristics) showed that diameter and height were significantly related to soil drainage in winter on these silt loams soils. Slash pines grew better than loblolly pines under more poorly drained conditions while loblolly pines grew better under the better drained conditions. On unbedded silt loams, the soil drainage in winter needed to maximize tree height was 42 cm for loblolly and 49 cm for slash pine. Pines planted on beds did not generally grow better than those on flat-disked plots because where bedding would be most benefical the practice did not form enough additional drainage to significantly influence pine development.

Okra production with pine straw mulch

Conventional planted okra in Booneville, Arkansas and Lorman, Mississippi were mulched with loblolly pine straw (Pinus taeda L.) and longleaf pine straw (P. palustris Mill.), respectively, at a rate of 11 t/ha or left bare. At Booneville, plant stand, season yields (18.6 t/ha), pod weight (16.3 g), plant dry weight (2.3 kg), or stem diameter (3.5 cm) were not affected by the loblolly pine mulch. However, mulch application increased pod number (1.22 vs. 1.06×106/ha) and plant height (1.5 vs. 1.6 m), while reducing weed competition (0.05 vs. 0.40 t/ha) and visible plant stress, during periods of soil moisture deficits. Soil temperatures at 5 and 15 cm depth were reduced by mulch until mid-August when plant canopies covered the rows. Seasonal moisture at 30 and 45 cm depths was similar between mulched and bare soils, based upon unreplicated neutron probe measurements. At Lorman, season okra yield (29.8 vs. 24.6 t/ha), number of pods per ha (1.24 vs. 1.07×106) and weed competition were reduced and soil pH lowered 0.56 units by longleaf pine straw mulch. Mulch reduced early season yield at both locations.

Biomass production of loblolly pine seeded between rows of planted loblolly pine

Abstract A dual-cropping concept was tested by growing loblolly pine ( Pinus taeda L.) for energy biomass in normally unused space between rows of a newly established pine plantation. Loblolly pine seeds were spot seeded in a 1.5 m wide swath between the planted rows of loblolly pine seedlings planted at 2 by 3 m spacing. At age 5 years, the direct-seeded trees from one of two seeded subplots of each plot were sampled for biomass and nutrient measurements. After subsampling, all of the direct-seeded material was removed from the subplot. On plots without direct-seeded trees, phosphorus fertilization increased height of the planted trees from 5.8 to 6.4 m and the dbh from 8.3 to 9.2 cm at age 5 years. The presence of the direct seeded trees reduced height 0.2 m and the dbh 0.6 cm. The average dry weight of the direct seeded material was 10.2 Mg ha −1 . Phosphorus fertilization had no effect on the growth of the direct-seeded trees after the first year. Water content (wet weight basis) of the direct seeded material was 62% in the needles, 52% in the branches and 56% in the main stems, which reduced potential fuel efficiency. Total energy produced over the 5 year period was 130,800 MJ ha −1 .