Timothy J. Albaugh

Carry-Over Effects of Water and Nutrient Supply on Water Use of Pinus Taeda

A study of the effects of nutrients and water supply (2 × 2 factorial experiment) was conducted in a 12-yr-old stand of loblolly pine (Pinus taeda L.) during a period in which soil moisture was not augmented by irrigation because of frequent rain events. Information on the responses of sapwood-to-leaf area ratio and early-to-late wood ratio, to four years of treatments led to the hypothesis that the combination of increased nutrient and water supply (IF treatment) will increase tree transpiration rate per unit leaf area (EC,1) above EC,1 in the control (C), as well as increasing EC,1 above that when either the supply of water (I) or of nutrients (F) is increased. We further hypothesized that canopy transpiration (EC) will rank IF > F > I = C, based on the ranking of leaf area index (L) and assuming that the ranking of EC,1 is as first hypothesized. We rejected our first hypothesis, because F had lower EC,1 than the other treatments, rather than IF having higher values. We could not reject the second hypothesis; the ranking of average daily EC was 1.8 mm for IF, 1.2 mm for F, and 0.7 mm for both C and I (se < 0.1 mm for all treatments). Thus, it was the lower EC,1 of the F treatment, relative to IF, that resulted in ranking of EC similar to that hypothesized. Lower EC,1 in F trees was found to relate to lower canopy stomatal conductance, even though soil moisture conditions during the time of the study were similar in all treatments. Only trees in the F treatment absorbed a substantial amount of water (25%) below 1 m in the soil. These results indicate a “carry-over” effect of irrigation when combined with fertilization that increases EC in irrigated trees, relative to unirrigated trees, even under conditions when soil moisture is high and similar in all treatments.

The influence of nutrient and water availability on carbohydrate storage in loblolly pine

We quantified the effects of nutrient and water availability on monthly whole-tree carbohydrate budgets and determined allocation patterns of storage carbohydrates in loblolly pine (Pinus taeda) to test site resource impacts on internal carbon (C) storage. A factorial combination of two nutrient and two irrigation treatments were imposed on a 7-year-old loblolly pine stand in the Sandhills of North Carolina. Monthly collections of foliage, branch, stem, bark, and root tissues were made and total non-structural carbohydrate analyses were performed on samples collected in years 3 and 4 after treatment initiation. Seasonal fluxes of carbohydrates reflected the hypothesized use and storage patterns. Starch concentrations peaked in the spring in all tissues measured; however, minimum concentrations in aboveground tissue occurred in late winter while minimum concentrations in below ground tissue occurred in late fall. Increased nutrient availability generally decreased starch concentrations in current year tissue, while increasing starch in 1-year-old woody tissue. Irrigation treatments did not significantly impact carbohydrate flux. The greatest capacity for starch storage was in below ground tissue, accounting for as much as 400 kg C/ha per year, and more than 65% of the total stored starch C pool. The absolute amount of C stored as starch was significantly increased with increased nutrient availability, however, its relative contribution to the total annual C budget was not changed.

Phosphorus Nutrition of Forest Plantations: The Role of Inorganic and Organic Phosphorus

Fertilization with P is a common silvicultural practice in forest plantations where large and sustained growth responses frequently occur following P fertilization. Inorganic P is tightly sorbed in many forest soils and, consequently, labile P is low. Trees have evolved a variety of mechanisms to acquire P in soils with low P availability. This includes release of low molecular weight organic acids into the rhizosphere. Significant quantities of organic P also exist in the forest floor and mineral horizons of forest soils that can contribute to P nutrition of forests. There are several mechanisms whereby organic P in the forest floor and the mineral soil may become available to forest trees. These include uptake of organic P by mycorrhizae and mineralization of organic P.

Intra-annual nutrient flux in Pinus taeda

Intra-annual nutrient (nitrogen, phosphorus, potassium, calcium and magnesium) flux was quantified for Pinus taeda L. at a nutrient-poor, well-drained sandy site in Scotland County, NC, USA where a 2 × 2 factorial of irrigation and nutrition was applied in four replications in a 10-year-old stand with 1200 stems ha(-1). Treatments were applied with the goal of providing optimum nutrition (no nutritional deficiencies) and water availability. Component (foliage, branch, stem and root) nutrient content was estimated monthly for 2 years using nutrient concentration and phenology assessments combined with destructive harvests. Positive flux values indicated nutrient accumulation in the trees while negative values indicated nutrient loss from the trees. Fertilization significantly increased nitrogen, phosphorus, potassium, calcium and magnesium flux 140%, on average, over non-fertilized. Irrigation significantly increased calcium flux 28% while there was no significant irrigation effect on nitrogen, phosphorus, potassium or magnesium. Maximum nutrient fluxes (kg ha(-1) day(-1)) for non-fertilized and fertilized stands were 0.36 and 1.05 for nitrogen, 0.042 and 0.095 for phosphorus, 0.13 and 0.51 for potassium, 0.27 and 0.42 for calcium, and 0.04 and 0.12 for magnesium, respectively. Maximum flux was coincident with ephemeral tissue (foliage and fine root) development and likely would be higher in stands with more foliage than those observed in this study (projected leaf area indices were 1.5 and 3.0 for the non-fertilized and fertilized stands). Minimum nutrient fluxes (kg ha(-1) day(-1)) for non-fertilized and fertilized stands were -0.18 and -0.42 for nitrogen, -0.029 and -0.070 for phosphorus, -0.05 and -0.18 for potassium, -0.04 and -0.05 for calcium, and -0.02 and -0.03 for magnesium, respectively. Minimum fluxes were typically observed in the dormant season and were linked to foliage senescence and branch death. Foliage and branch component nutrient contents were out of phase for nitrogen, phosphorus, potassium and magnesium, indicating nutrient retranslocation and storage in branches prior to foliage development and after foliage senescence. In contrast to current operational fertilizer programs which often target winter application these data suggest the best application times would be during foliage development.

An Investigation of the Impacts of Elevated Carbon Dioxide, Irrigation, and Fertilization on the Physiology and Growth of Loblolly Pine

Southern pine forests that are dominated by loblolly pine (Pinus taeda L.) are the most intensively managed forests in the United States. They provide more than 50% of the total softwood being harvested annually in the United States and represent the first or second most economically important agricultural crops in nine of the twelve southeastern states (U.S. Department Agriculture Forest Service, 1988). Thus, any changes in environmental conditions that will alter productivity of these forests will have important ecological, economical, and sociological consequences. Over the past several decades, the environment of southeastern forests has been changing. Increases in acidic deposition (SO4 and NOx), nitrogen inputs (Husar, 1986), atmospheric CO2 concentration (Conway et al., 1988; Keeling et al., 1989), and tropospheric ozone have all been documented to parallel the increase in population since the beginning of the industrial revolution. Climate change has also been predicted for the southeastern United States for the future. Each of these atmospheric and climatic elements that are being altered by human activities has the potential to affect productivity of southern pine forests. Nutrient availability, water availability, atmospheric CO2 concentration, and temperature are presently the principal factors that are limiting the productivity of southern pine forests. Thus, it is extremely important that we understand how changes in these factors will interact to affect physiological processes of forest stands.

Biomass-D2H relationships for young loblolly pine as affected by ozone

Abstract The influence of below and above ambient levels of ozone on the relationships between biomass components (foliage, branch, and stem) and DZH was examined using data from 1284 young loblolly pine ( Pinus taeda L. ) harvested from two ozone field studies. A In-in model form provided a very good fit of the biomass data. Residual plots showed no bias and R 2 ranged from 0.94 to 0.99. Ozone treatment significantly affected the shape of biomass— D 2 H relationships for all components except stem. For a given D 2 H , increasing ozone dose resulted in less foliage and more branch biomass. After adjusting for age and tree size, increasing ozone dose significantly increased number of branches after one year of ozone treatment. After the second year, ozone dose did not significantly change the number of branches when adjusting for tree size; however, the trends were the same as the first year. Because of the strong negative ozone effect on foliage biomass, total biomass for a given D 2 H was less for increasing ozone dose. Ozone effects need to be considered when developing biomass equations for young loblolly pine trees.

Leaf area duration in natural range and exotic Pinus taeda.

Exotic Pinus taeda L. plantations may be more productive than native ones. Several hypotheses may explain this difference; however, process models with a light-interception-driving variable cannot test these hypotheses without foliage display first being quantified in native and exotic trees. We quantified leaf area duration in North Carolina, USA (natural), and Gobernador Virasoro, Argentina (exotic), with no additional nutrients and optimum fertilizer treatments. More (60%–100%) foliage was displayed but for a shorter (∼86 fewer days) time per fascicle in the exotics than in the naturals. Study inference was limited, with only one native and one exotic site. However, while the sites were markedly different in soils, climate, resource availability, and genetics, and we observed significant differences in fascicle display and longevity, most fascicles at both sites survived two growing seasons: the one in which they were produced and the subsequent one. This robust finding indicates it would be reasonable...

Advances in Silviculture of Intensively Managed Plantations

Purpose of ReviewIntensive management of forest plantations has evolved significantly in recent decades because of advances in our understanding of environmental and silvicultural effects on forest productivity combined with improvements in information technologies. Our paper summarizes concepts that provide a basis for making strategic and operational silvicultural decisions that insure sustainability when applying intensive management of forest plantations. In addition, we include new information in areas where there are knowledge gaps in forest plantation management.Recent FindingsIntensive management of forest plantations increasingly incorporates large-scale precision silviculture to estimate silvicultural, biotic, and abiotic effects on site-specific forest productivity. Remote sensing measurements combined with strategically located ground information provide spatial modeling tools needed for this type of silviculture. Long-term field experiments, which are a part of this methodology, provide a mechanistic understanding of environmental and silvicultural effects on forest production that is required for the models driving silvicultural decisions. The focus on maximizing production will challenge scientific efforts to alleviate concerns about intensive land use and to provide solutions for water use conflicts while maintaining long-term productivity and sustainability. Future work will need to develop a better understanding of genetic × environment × silvicultural (G × E × S) interactions to improve productivity and simultaneously provide improved ecosystem services.SummaryNew silviculture technology combines remote sensing information with ground data to model resource availability and limitations to forest productivity. Understanding G × E × S permits successful implementation of these new silvicultural technologies. An improved understanding of G × E × S will provide practical tools that may be incorporated into our scientific and technical models while providing robust economic sustainability.