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Artificial regeneration is successful when high-performing seedlings are transported with care to the planting site, stored for a short period in an environment without desiccation or fungal growth, and planted in a deep hole, so roots are in contact with moist soil. One of the requirements for success is the ability to avoid common planting mistakes. Due, in part, to the use of container stock plus an increase in rainfall, the average first-year survival of pine seedlings (89%) in the southern United States is about 15% greater now than 45 years ago. However, when survival is less than 50% six months after planting, some landowners seek reimbursement for their loss. Some assume poor seedling quality was the cause without realizing that anaerobic soils or sudden freeze events, shallow planting holes, pruning roots, a lack of rain or underground insects can kill pines. With a focus on pines planted in the southern United States, we list non-nursery factors that have killed seedlings in North America, Africa and Europe.

This review provides information and opinions about irrigation practices in pine nurseries. Even when nurseries receive more than 15 mm of rainfall week-1, managers irrigate seedbeds to increase germination, increase seed efficiency, and increase root growth. In the southern United States, a 7-month old pine seedling in an outdoor nursery typically receives 2 to 6 kg of water supplied from either sprinklers (39 nurseries) or center-pivot irrigation (12 nurseries). Most nursery managers do not intentionally subject the crop to moisture stress, since most reforestation sites receive adequate rainfall, and many studies show that reducing root mass does not increase seedling performance. In fact, nursery profits can be reduced by more than $13,000 ha-1 when deficit irrigation reduces average seedling diameter by 1 mm. Although some researchers believe that failure to properly drought stress pine seedlings might increase outplanting mortality by up to 75%, research over the past 40 years does not support that myth. When pine seedlings average 5 mm (at the root-collar), water stress is not a reliable method of increasing tolerance to an October freeze event. In several greenhouse trials, researchers grew and tested seedlings that nursery managers would classify as culls (i.e., dry root mass < 0.5 g). Unfortunately, it is common for researchers to make irrigation recommendations without first developing a water-production function curve.

Copper has been used by nursery managers for more than 100 years to suppress fungi and as a fertilizer for more than 50 years. Consequently, nursery seedlings with copper deficiencies are rare, especially for broadleaf species. In many nurseries, soil contains

This review covers most of the published literature on potassium (K) fertilization in bareroot seedbeds with the intent to concentrate on the southern United States. The timing and rates of K fertilization for bareroot seedlings are often based on logic and myths and, as a result, K recommendations vary considerably. Some recommend bareroot pine seedlings be fertilized with twice as much K as nitrogen (N) while others apply less than 100 kg ha-1. It was determined that several long-held claims about K fertilization are invalid. Nursery seedbeds do not need to contain four times as much available K as N and the belief that extra K fertilization will increase freeze tolerance or drought resistance of non-deficient seedlings is invalid. There are no data to support the claim that K fertilization increases root growth or assists in the formation of terminal buds. For sandy seedbeds, there is no need to apply K before sowing. Adding extra K during the fall does not increase seedling morphology or seedling performance when loblolly pine seedlings, at lifting, have more than 0.5% K in needles. A reduction of K fertilization can be achieved by reviewing foliar tests prior to K top-dressings.

Two schools of thought address the optimum soil pH (measured in water) for growing hardwood seedlings in bareroot nurseries. One school uses nutrient surveys in non-fertilized forests to determine the best pH range for growing seedlings in fertilized nurseries. Some students of this school believe hardwood seedlings grow best at pH 6.0 to 7.5. In contrast, another school relies on research from pH trials to conclude that fertilized hardwoods can grow well in soils that range from pH 4.5 to 6.0. This article compiles some of the findings from seedbed and greenhouse trials and attempts to use data to dispel a few myths about the “optimum pH” for growing hardwood seedlings. Greenhouse trials suggest many fertilized hardwoods grow better in acid soils (pH 4-6) than in nearly neutral soils (pH 6.0-7.5). The optimal pH for growth differs among species and, therefore, it is a myth that all hardwood seedlings grow best at pH 6 to 7.5. Most nursery managers in the southern United States grow bareroot hardwoods between pH 4.8 and 6.0.

In North America, most tree nursery nutrition publications during the past two decades involved either container-grown stock or stock grown in greenhouses. In contrast, most bareroot nursery fertility trials in North America were published during the last century. As a result, some bareroot fertilization recommendations have remained the same since 1980 and some practices continue to be based on myths and assumptions. The bareroot nursery industry in the USA might benefit if the next generation of graduate students will consider testing old and new theories about nursery fertilization. Hopefully, they will discover new facts so that future fertilization regimes will be based on science. This paper provides various fertilizer trials that should be established in bareroot nurseries.

Although the production of commercial products of vegetative Pt (Pisolithus tinctorius (Pers.) Coker & Couch) inoculums has ceased in North America due to a lack of demand by consumers, the number of products that contain Pt spores has increased. The quality, quantity and price of these products vary considerably. The cost of inoculating 1,000 tree seedlings with Pt basidiospores can vary from $0.45 to more than $30. The cost of treating with Pt spores is lowest when seedlings are inoculated in a container nursery using rates that are less than 0.4 mg per seedling. However, with some products the cost to treat 1,000 bareroot seedlings is greater than $500 when spores are applied in the planting hole. Three decades ago, 1 g of Pt spores could be purchased for $0.13 and now the price of 1 g can exceed $14. Although many research papers provide data on the biological response to inoculating seedlings with spores, few document the cost of inoculation. Commercial products that are marketed toward homeowners containing both ectomycorrhizal and endomycorrhizal spores are more expensive than products that contain only ectomycorrhizal spores. In situations where survival and growth of seedlings are not increased, the benefit/cost ratio will typically be less than one.

Two pH experiments were conducted at a sandy, bareroot loblolly pine (Pinus taeda L.) nursery in Texas. A sulfur trial (0, 813, 1626, 2439 kg ha-1 of elemental sulfur) was installed to determine if lowering soil pH would result in nutrient toxicity symptoms and affect seedling morphology. Although soil acidity in the sulfur study ranged from pH 3.9 to pH 5.0, none of the treatments resulted in micronutrient toxicity and none affected height growth, root-collar diameter, root mass, shoot mass or the root-mass ratio (root dry mass/total dry mass). Acidifying soil with sulfur increased leaching of calcium, potassium, magnesium, manganese and zinc but there was no effect on seedling morphology. The objective of the liming trial (0, 813, 1626, 3252 kg ha-1 of dolomitic lime) was to determine if increasing alkalinity would result in an iron deficiency and reduce seedling growth. As expected, applying lime increased the calcium and magnesium levels but had no effect on soil levels of iron, phosphorus, potassium, sulfur, zinc and sodium. However, the root-mass ratio was reduced by applications of dolomitic lime (pH ranged from 5.3 to 6.0). Differences in soil properties (i.e. plot location) had a greater effect on seedling morphology than lime applications. Foliage levels of manganese and boron were reduced by the highest rate of lime and sulfur, respectively.

This review compares fall acclimation patterns and lift/store practices for Pseudotsuga menziesii var. menziesii, Picea glauca (Moench) Voss x P. engelmannii Parry ex engelm and Pinus taeda L. seedlings. Spruce seedlings achieve budset and an endodormant state in late summer, coastal Douglas-fir in early fall, while loblolly pine achieves a less endodormant state with a limited amount of mitotic activity. Natural chilling during the fall reduces days to budbreak (DBB) and increases freezing tolerance, with northern species achieving greater freezing tolerance. Although root growth potential (RGP) in some years may increase from early fall to mid-winter, this trend does not always occur. Chilling hours and/or freezing tolerance status is used to initiate storage of Douglas-fir and spruce seedlings but there is no proven attribute to make the lifting decision for loblolly pine. When properly hardened, all species can be cooler stored to meet lift/store requirements of a few months, though fall lifted interior spruce seedlings are typically freezer stored for up to six months. Lengthy storage can cause declines in DBB, freezing tolerance, RGP, and carbohydrate reserves. Douglas-fir and interior spruce seedlings require an appropriate length of fall acclimation, typically including chilling, to develop a level of hardiness for lengthy storage and high survival after outplanting. Loblolly pine seedlings benefit from chilling, though non-chilled, hardened seedlings may exhibit high survival after four weeks of cooler storage. Each species has a unique fall acclimation pattern making it difficult to define universal culture practices across all regional forest regeneration programs.

Two studies were established to determine the effects of planting depth on early performance of bareroot shortleaf pine seedlings (Pinus echinata). The studies involved planting seedlings either with the root-collar slightly below the groundline (GL) or with the root-collar planted about 11 cm below the soil surface (DEEP). After transplanting, DEEP seedlings had about 7.9 cm of shoot remaining aboveground. In one study, seedlings were planted in open sand pits where seedlings received 352 mm of rain by April 30. The second study involved planting seedlings in boxes (containing sand) in a roofed shade-house. Without rain, survival of DEEP seedlings in April was 96% which was significantly greater (P>F =0.007) than survival of GL seedlings (67%). With rainfall, survival (95%) was the same for both planting depths (P>F = 0.39). Therefore, planting seedlings with the root-collar level with the soil surface can, in some years, increase mortality. This might help explain why bareroot survival of shortleaf pine in some forest districts averages less than 80%.

Cold storing bareroot southern pine (Pinus spp.) seedlings for greater than one week after lifting in the fall can lead to poor outplanting survival when compared to seedlings that are lifted and stored in winter. In contrast, container-grown seedlings typically do not experience adverse effects from storing for periods greater than one week. The practice of lifting bareroot seedlings can cause wounds to root systems, which could allow soil-borne pathogens such as Pythium species to be used as infection sites. Once seedlings are placed in storage, the cool, moist environment may be conducive for zoospore activity, leading to root disease and outplanting failure. Bareroot and container-grown longleaf pine (Pinus palustris), loblolly pine (Pinus taeda), and slash pine (Pinus elliottii) and container-grown shortleaf pine (Pinus echinata) were inoculated with either Pythium dimorphum or Pythium irregulare, cold-stored for 3, 4, 6, or 12 weeks, and outplanted. Both Pythium species reduced survival of bareroot longleaf pine but not bareroot slash pine. Length of storage decreased survival for both seedling stock types. Pythium species did not affect the survival of container-grown seedlings. These results suggest that P. dimorphum and P. irregulare are more virulent to bareroot longleaf pine than the other pine species tested.

Pinus taeda L. plantations in the United States are typically established using rows that are spaced 3 to 4 m apart. Although one company now plants pines in 6.1 m rows, reports on performance using this row spacing are rare. This paper provides a case study (established at the Solon Dixon Forestry Education Center) that compares two densities (672 vs 1344 seedlings per ha (SPH)) when fixing the between-row distance to 6.1 m and using either 2.44 m or 1.22 m within-row distances between the planted trees. At age 13-years, the aboveground biomass mean annual increment on this old-orchard site was 13.5 green Mg/ha/yr. Planting half as many pine seedlings as typical (for this region) did not reduce dominant height (P=0.22), basal area/ha (P=0.58) or total merchantable tonnes/ha (P=0.67). As expected, the higher density produced trees that were smaller in mean diameter at breast height DBH (25 vs 22 cm) and had more pulpwood than 672 SPH plots. However, planting pines 1.2 m apart within the row reduced survival, soon after two severe summer droughts. Apparently this stress increased the risk of attracting bark beetles. An economic analysis indicates that 672 SPH produced more valuable timber (at age 13 years) and had the highest Net Present Value (NPV). In contrast, the Ptaeda3 model indicated 1344 SPH would have the greater NPV. The conflicting results are related to Ptaeda3 predicting one sawtimber-sized tree while 156 were present in the 672 SPH plots. Although these findings should not be extrapolated to cutover sites, it appears there may be several advantages to planting pines in wider than traditional rows. The reluctance to plant Pinus taeda in 6.1 rows on flat, agricultural lands might be due to a lack of field data and/or a reliance on output from growth and yield programs that were developed using data from cutover sites.

Yellow nutsedge (Cyperus esculentus) is a difficult weed to control in conifer nurseries. Soil fumigation with methyl bromide has been used to control yellow nutsedge for years but may not be available in the future. For this reason, the objective of this research was to identify herbicides that can control yellow nutsedge but do not injure loblolly (Pinus taeda L.) and slash pine (Pinus elliottii Engelm.) when used over-the-top of seedlings. Yellow nutsedge tubers and loblolly and slash pine seedlings were potted separately, and treated with three rates of the herbicides mesotrione (Callisto®), imazosulfuron (Valent-V10142), and halosulfuron (Sedgehammer®). Imazosulfuron and halosulfuron provided the best suppression of nutsedge, but imazosulfuron injured loblolly and slash pine. Slash pine diameter and height growth were reduced by imazosulfuron. Halosulfuron did not affect loblolly pine but it reduced slash pine height growth and the number of new leaders (spring flush growth) the following spring. Mesotrione injured slash pine but provided intermediate control of yellow nutsedge. Halosulfuron applied at 35 to 140 g ai·ha−1 (active ingredient per hectare) over the top of loblolly pine (≥ 60 cm height and ≥ 8 mm diameter) can control yellow nutsedge without injuring pine seedlings.

Managers are typically interested in using equations that provide accurate volumes for large, merchantable trees while modelers are often more interested in equations that meet statistical assumptions. Therefore, modelers often use weighted (WLS) rather than ordinary least squares (OLS) to fit individual tree volume equations since the random error variance is not constant. Since OLS and WLS produce different parameter estimates, perhaps the method chosen will impact the predicted optimum economic rotation age. To address this concern, individual tree volumes were obtained from plots established in an unthinned loblolly pine plantation in southeastern Arkansas. Parameters of the combined- variable function were then estimated using OLS and WLS for the same dataset. Stand-level projections and predicted diameter distributions for two planting densities (748 and 2,692 seedlings per hectare) were then obtained from a growth and yield model (PTAEDA 3.1) and individual tree volumes were predicted using the two parameter estimation approaches. When conducting economic analyses, we found the optimum rotation age between OLS and WLS can differ by as much as 11 yrs (i.e. 10 yr clearcut vs 21 yr clearcut).

An assumption of ordinary least squares (OLS) is constant variance across the domain of a regressor. Often, however, the random error term variance is not constant when modeling biological data and therefore weighted least squares (WLS) is commonly used to estimate parameters. Less emphasis is placed on observations of the dependent variable with larger variances when using WLS, which is thought to produce more “efficient” parameter estimates. Statisticians often use WLS instead of OLS when the random error variance is not constant. However, as natural resource managers, we are often most interested in values of the dependent variable where the variance is greatest. What then are the biological, economic, and management implications of using WLS versus OLS in natural resource modeling? In this article, parameters of the combined-variable volume equation were estimated for individual trees in loblolly pine plantations using both OLS and WLS. A growth-and-yield model was used to predict stand development over time of two planting densities (303 and 1,090 seedlings/ac) and individual tree volumes were predicted using OLS and WLS parameter estimates. Economic analyses were then conducted. Our results show that the choice of OLS or WLS can have a substantial impact on predicted economic returns. Thus, when using WLS, landowners may decide to invest in additional management treatments that may, in fact, not be economically feasible. This study provides further evidence that landowners need to be aware of model structures when basing harvest-age decisions on growth and yield projections.

Because of concerns over the ozone layer, the annual amount of methyl bromide used for soil fumigation for crop production is decreasing. A promising alternative soil fumigation treatment involves applying 300 lb/ac of chloropicrin (CCl3NO2) under a plastic tarp. Although this soil fumigant does not control weeds as well as an equivalent amount of methyl bromide, chloropicrin is an effective strategy for controlling many soilborne pests. The total amount of chloropicrin used for fumigation in southern pine nurseries will likely increase as use of methyl bromide fumigation declines.

Summary Gains in stand volume that result from competition control and fertilization are sometimes reported as ‘ percentage gains ’ . Because percentage gains arithmetically decline over time as stand volume increases, plantation managers have diffi culty in using percentage gains to project growth and revenues. The ‘ age-shift ’ method quantifi es the year advancements in stand growth due to silvicultural treatments and, for herbaceous vegetation management, it has been proposed that this metric is less likely to change after the juvenile growth phase. To test the sensitivity of the ‘ age-shift ’ method to time and hardwood competition, we used 20-year volume data from 11 loblolly pine ( Pinus taeda L.) studies that had early complete herbaceous and woody competition control. Volume growth gains were expressed in terms of percentages and ‘ age-shifts ’ . On all sites with no woody competition, percentage gains declined from age 8 years to age 20 years. In contrast, age-shift estimates on these plots either remained constant or increased over time. However, in four cases where woody basal areas were greater than 4 m 2 ha − 1 at age 15 years, age-shift gains due to herbaceous control decreased and eventually resulted in volume losses. When evaluating the response to early herbaceous competition control, age-shift calculations have promise as a useful predictive tool on sites with low levels of hardwood competition. Five methods for calculating age-shift are presented.

Improving seedling performance by reducing seedling height can be an important aspect of nursery management. The plant growth regulator uniconazole was applied to regulate height growth of nursery-grown loblolly pine (Pinus taeda L.) seedlings. Tests involving a foliar spray (0,0.125, 0.25, 0.5 and 1.0 kg ai/ha) or a wick application (0, 125, 250, 500, and 1000 ppm) were conducted in Alabama, Georgia, and South Carolina. The wick applicator consisted of a perforated plastic pipe covered with a sponge cylinder supplied by a reservoir. With both application methods, as the rate of uniconazole increased, seedling height, root-collar diameter, and biomass decreased. Compared to the controls, uniconazole decreased the percentage of seedlings with root-collar diameters greater than 4.7 mm. At lifting there was no difference among rates for root/shoot ratio, but root/shoot ratios of uniconazole treated seedlings increased significantly after outplanting. Eighteen months after outplanting, there were no treatment effects on seedling height or survival. Wick applications of uniconazole merit further research because of soil persistence and costs associated with spray applications. South. J. Appl. For. 28(1):41–47.

A loblolly pine (Pinus taeda L.) seedling grade study was established in January 1987 on a Coastal Plain site at Bellville, Georgia. The factorial study involved three seedling grades (Wakeley's Grade 1, 2, and 3) and three half-sib families (#5, 25, 56). Trees were measured at ages 8 and 13 yr. Both family and seedling grade affected survival, height, and diameter at age 8 yr. Survival among families varied by as much as 3 percentage points while there was a 10 percentage point difference between Grade 1 and Grade 2 seedlings. Only family was related to height and diameter at age 13. Volume gains from planting Grade 1 seedlings instead of Grade 3 seedlings varied by family but there were no significant interactions between family and seedling grade. Differences in height among families and among seedling grades decreased over time. At age 8, there was a 5.3 ft difference between the tallest and shortest family but by age 13, the difference declined to 3.7 ft.Overall, planting family 56 instead of family 25 resulted in an additional 645 ft3/ac by age 13. Planting Grade 1 seedlings instead of Grade 3 seedlings produced an additional 303 ft3/ac. Per acre volume differences among families were greater at age 13 than at age 8. In contrast, differences among seedling grades were about the same at age 8 and 13 yr. The overall mean annual increment (MAI) for this study was 207 ft3/ac/yr. In comparison, the MAI for Grade 1 seedlings of family 56 was 239 ft3/ac/yr. South. J. Appl. For. 26(3):153–158.

When it comes to testing for differences in seedling survival, researchers sometimes make a Type II statistical error (i.e. failure to reject a false null hypothesis) due to the inherent variability associated with survival in tree planting studies. For example, in one trial (with five replications) first-year survival of seedlings planted in October (42%) was not significantly different (alpha = 0.05) from those planted in December (69%). Did planting in a dry October truly have no effect on survival? Authors who make a Type II error might not be aware that as seedling survival decreases (down to an overall average of 50% survival), statistical power declines. As a result, the ability to declare an 8% difference as “significant” is very difficult when survival averages 90% or less. We estimate that about half of regeneration trials (average survival of pines

Loblolly pine (Pinus taeda L.) seedlings were lifted from two nurseries in Georgia, and the roots were washed using equipment built for that purpose. Seedlings then received two levels of storage and were outplanted not far from the nursery of origin (one loam soil and one sandy soil). Immediately after washing, root weights and the length of fine roots did not differ among wash treatments from either nursery. Survival was excellent for all treatments on the loam soil, but a single wash reduced survival by 5 to 10% when seedlings were planted in sand. Washing slowed the rate of budbreak and early height growth. Bud growth of seedlings planted in a stress pit (containing sand) was correlated with both root growth 1 month after planting (r = 0.36,P = 0.0003) and survival 2 months after planting (r =0.62,P = 0.01). Among seedlings outplanted on a sandy site, initial height growth also correlated with survival (r = 0.49,P = 0.007). South. J. Appl. For. 25(1):25–30.

Tolerance of three pine species to postemergence applications of clopyralid was examined at ten southern nurseries over a 2 yr period. The herbicide was applied at various times during May, June, and July. At time of lifting, seedling morphology was evaluated (root-collar diameter, shoot height, root dry weight, and shoot dry weight). Loblolly pine (Pinus taeda L.), slash pine (P. elliottii Engelm. var. elliottii) and longleaf pine (P. palustdds Mill.) were tolerant to 210 to 840 g acid equivalent (ae)/ha. However, epinasty was occasionally observed on both loblolly pine and slash pine. The injury symptoms were ephemeral and seedlings appeared normal 3 months after treatment. Results from these tests suggest some pine species are tolerant to this herbicide at the seedling stage. As a result of this research, this herbicide can be legally used in many southern pine nurseries to control troublesome weeds such as sicklepod (Cassia obtusifolia L.), Florida beggerweed (Desmodium tortuosum [Sw.] DC.), horseweed (Erigeron canadensis L.) and other annual broadleaf weeds. South. J. Appl. For. 24(1):51-56.

Studies have shown that clipping needles of longleaf pine before outplanting can increase average seedling survival by 13 percentage points. Under some situations, the increase in survival might be due to a reduction in transpiration. For loblolly pine, top-pruning in the nursery might increase average survival by 6 percentage points. Benefits of pruning appear greater when seedlings experience stress after planting and when nonpruned seedlings have low root weight ratios (root dry weight/total seedling dry weight). On some droughty sites, a seedling with a 0.3 root weight ratio might have an 80% chance of survival, while a seedling with a 0.2 root weight ratio might only have a 53% chance of survival. In most studies where heights were measured after 3 yr in the field, pruned seedlings were the same height as nonpruned seedlings (± 7 cm). South. J. Appl. For. 22(4):235-240.

Chloropicrin has been tested as a soil fumigant in forest nurseries throughout the world. From 1944 to the late 1960's, tests were conducted in Australia, Canada, Netherlands, New Zealand, the United Kingdom and the United States. Since 1985, studies have been conducted in Georgia, Mississippi, South Carolina, Texas, Virginia, Washington and Wisconsin. In Wisconsin, chloropicrin reduced soilborne pathogens as effectively as twice as much methyl bromide. Advantages of chloropicrin as a soil fumigant in southern pine nurseries include: efficacy similar to methyl bromide (in regards to reduction in fungi, nematodes and insects), an increase in Trichoderma populations, it is not a Class 1 ozone depleting substance, and no plastic tarp is required. Adding chloropicrin to other fumigants has increased the spectrum of biological activity. A disadvantage of chloropicrin is that it has less herbicidal activity than methyl bromide. Key words: fungicide, methyl bromide, disease, nursery management, seedbeds

Large-scale tree planting programs have placed a tremendous pressure on nursery managers to supply unprecedented numbers of seedlings. Inclusion of chemicals into seed production regimes have made it possible for southern pine nurseries to be the most productive in the world, in terms of both output per nursery and average cost per seedling. Nursery managers in the South rely on the use of fertilizers, fumigants, and pesticides to help keep production costs low. Judicious use of fertilizers can reduce the production of cull seedlings as well as increase field growth after outplanting. It has been our experience that investing in the use of pesticides and inorganic fertilizers provides a high rate of return for the nursery manager. South. J. Appl. For. 20(3):127-135.

Six herbicides and selected combinations were evaluated on four field-grown woody landscape crops: live oak, ‘Mary Nell’ holly, ‘Chesapeake’ viburnum, and ‘Acoma’ crapemyrtle. All herbicide treatments provided excellent control of goosegrass (Eleusine indica (L.) Gaertn.). Treatments with Predict (norflurazon) provided adequate sicklepod (Cassia obtusifolia L.) control. Only Goal (oxyfluorfen)-containing treatments controlled cutleaf eveningprimrose (Oenothera laciniata Hill). Predict and Predict treatment-combinations bleached older foliage of crapemyrtle and viburnum when applied in the first year after planting; however, growth was not affected. Holly was not injured by any herbicide treatments. Pendulum (pendamethalin) and Surflan (oryzalin) had similar weed control activity and plant growth with no plant injury

Tolerance of southern pines to preemergence applications of fomesafen was examined at eight nursery experiments in 1984. When sown on coarse textured soils, loblolly pine (Pinus taeda L.), slash pine (Pinus elliottii Engelm. var elliottii), longleaf pine (Pinus palustris Mill.), and shortleaf pine (Pinus echinata Mill.) were tolerant to 0.5 kg ai/ha applied after sowing. However, a reduction in loblolly pine seedling production was observed with one test on a silt loam soil in Louisiana. The risk of injury from a preemergence application may be related to soil texture. Pine tolerance to a single postemergence treatment was tested at seven nurseries in 1985. No significant injury was observed when 0.5 kg ai/ha was applied 3 to 8 weeks after sowing loblolly pine or shortleaf pine, and no injury was observed on fall-sown eastern white pine (Pinus strobus L.). When applied 1 or 2 months after sowing, loblolly pine appears tolerant to fomesafen even on silt loam soils. Injury has been observed from postemergence applications when a surfactant was used in combination with fomesafen. Preemergence applications of fomesafen are now an operational practice at several southern pine nurseries. South. J. Appl. For. 21(3):143-145.

Successful afforestation has been practiced in South Africa for more than a century. Recently, however, problems with afforestation of pines have occurred in the northeastern part of the Eastern Cape Province. Rapid mortality of Pinus patula and P. elliottii have occurred when small container seedlings were planted on old-agricultural soils. Death would often occur within 5 months of planting. Growth of surviving trees was retarded and new needles were chlorotic and stunted. Acceptable survival was obtained when seedlings were planted on virgin grasslands. Apparently, some unseen factor in the post-agricultural soil reduces root growth, increases mortality, and decreases uptake of nutrients. Removal of the infested soil by scalping greatly improves survival and growth as does soil fumigation with methyl bromide.

Regional pine seedling tolerance experiments were conducted on five pine (Pinusspp.) species at ten forest nurseries in 1974. Similar studies in 1975 included four pine species at nine locations. From these studies, herbicides appearing safe for preemergence use are bifenox [methyl 5-(2,4-dichlorophenoxy)-2-nitrobenzoate] at 1.7, 3.4, and 6.7 kg/ha; butralin [4-(1,1-dimethylethyl)-N-(1-methylpropyl)-2,6-dinitrobenzenamine] at 2.2, 3.4, 4.5, and 6.7 kg/ha, napropamide [2-(α-naphthoxy)-N,N-diethylpropionamide] at 1.7 kg/ha; napropamide at 1.1 kg/ha plus bifenox at 3.4 kg/ha; dinitramine (N4,N4-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine) at 0.37 and 0.74 kg/ha; diphenamid (N,N-dimethyl-2,2-diphenylacetamide) at 4.5 kg/ha, trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) at 1.1 kg/ha; and profluralin [N-(cyclopropylmethyl)-α,α,α-trifluoro-2,6-dinitro-N-propyl-p-toluidine] at 1.1 and 2.2 kg/ha. Southern pine seedling tolerance to oryzalin (3,5-dinitro-N4,N4-dipropylsulfanilamide) was unacceptable at 1.1 and 2.2 kg/ha. Napropamide severely stunted seedlings at 6.7 kg/ha but affected seedlings only slightly at 3.4 kg/ha.

Third-year heights, third-year root-collar diameters, and 3 yr volume growth of loblolly pine seedlings were examined in relation to a) root-collar diameter class at time of planting and b) herbaceous weed control. Treatments were a) no weed control and b) complete control for 2 yr. For both weed control treatments, means for third-year heights, groundline diameters, and volume growth were related positively to initial seedling diameter. The influence of initial seedling diameter on third-year diameters and heights did not differ among weed control treatments. However, the influence of initial diameter on volume growth did differ among weed control treatments. Thus, when using herbaceous weed control, additional gains in early volume growth can be realized by planting seedlings with large root-collar diameters.

The effects of hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4 (1H, 3H)-dione] and its metabolites, A [3-(4-hydroxycyclohexyl)-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4 (1H,3H)-dione], B [3-cyclohexyl-6-(methylamino)-1-methyl-1,3,5-triazine-2,4 (1H,3H)-dione], C [3-(4-hydroxycyclohexyl)-6-(methylamino)-1-methyl-1,3,5-triazine-2,4 (1H,3H)-dione], D [3-cyclohexyl-1-methyl-1,3,5-triazine-2,4,6 (1H, 3H,5H)-trione], and E [3-(4-hydroxycy clohexyl)-1-methyl-1,3,5-triazine-2,4,6 (1H,3H,5H)-trione], on photosynthesis of loblolly pine primary needle segments were studied using a bioassay technique. Hexazinone, at concentrations equal to or greater than 1.0 × 10-6M, inhibited photosynthesis, while 1.0 × 10-8M and 1.0 × 10-7M concentrations increased photosynthesis. Metabolite B at 1.0 × 10-4M also inhibited photosynthesis. Metabolites A, C, D, and E did not affect photosynthesis at 1.0 × 10-4in pine needle segments. The bioassay proved simple and useful for determining effects of certain herbicides and metabolites on photosynthesis.

Correspondence Dear Editor I am writing to draw your readers’ attention to recently published findings that, in my opinion, will alter the way we think about “greenhouse gasses/global warming.” These findings may cause critical thinkers to question the effectiveness of “carbon-sequestration plantations” (aimed at altering atmospheric temperatures). Traditionally, the effect of having an atmosphere has been estimated to increase the Earth’s average temperature by 33 °C. However, Volokin and ReLlez (2014) provided mathematical and empirical evidence that the effect of nearly 1-bar atmosphere on Earth’s average temperature is around 90 °C. The authors showed that the 33 °C estimate referred to in virtually all meteorology/climate textbooks for the past 40 years has been a result of incorrect application of the Stefan-Boltzmann radiation law to a sphere. The study also demonstrates for the first time that the atmospheric thermal effect has a significant non-radiative component controlled by air pressure. Based on these findings, the contribution of greenhouse gasses to Earth’s fluctuating temperature will remain uncertain until the magnitude of the newly identified thermodynamic temperature enhancement is fully quantified by future research. In a subsequent paper, Volokin and ReLlez (2015) developed a new macro-level model using data from six celestial bodies in our solar system (i.e., Venus, Moon, Earth, Mars, Titan, and Triton). Amazingly, their model accurately predicts the mean global temperatures of rocky planets (with diverse atmospheres) using only two variables: top-of-the-atmosphere solar irradiance and total surface atmospheric pressure. According to the authors, “The new model displays characteristics of an emergent macro-level thermodynamic relationship heretofore unbeknown to science that deserves further investigation and possibly a theoretical interpretation.” The model fully explains the previously mentioned ~90 °C atmospheric effect as a function of atmospheric pressure and solar irradiance. The authors show that neither the concentration nor the partial pressure of greenhouse gasses can satisfactorily predict the observed variation of global planetary temperatures across the solar system. These new results indicate that the pressure of Earth’s atmosphere plays a key role in keeping the planet warm while accounting for virtually 100 % of the so-called natural greenhouse effect. This implies that the rising levels of “greenhouse gasses” may have little to no effect on future climate. The findings by Volokin and ReLlez (2014, 2015) may improve our understanding of the possible impact of afforestation on global temperature as follows: Some researchers say that a massive afforestation effort might warm the Earth by 0.1 °C (Davies-Barnard et al. 2014) while many foresters assume that removing 8.7 Gt of carbon from the atmosphere (by planting trees) would delay anthropogenic global warming by about one year. Although arriving at contradictory conclusions, both of these groups have assumed that carbon dioxide and other trace gasses, rather than atmospheric pressure, have warmed the Earth by about 33 °C. However, the findings of Volokin and ReLlez (2014, 2015) cause us to question: (1) the theoretical foundation of the “greenhouse” theory itself; and (2) the belief that large-scale carbon sequestration can alter the global mean temperature. Readers should be aware that atmospheric science is not set in stone; there is plenty of room for the evolution of our understanding on this complex topic. The above scientific breakthrough is not to say that we as foresters do not have a stewardship responsibility for protecting forests and establishing tree plantations. However, our reason for tree planting should no longer rest on the belief that greenhouse gas emissions will cause catastrophic global warming. David South is Emeritus Professor, Auburn University.