Browsing by Author "H. Lee Allen, Committee Chair"

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Biomass and nutrient accumulation comparison between successive loblolly pine rotations on the Upper Coastal Plain of Alabama.
(2003-01-29) Rubilar, Rafael Alejandro; H. Lee Allen, Committee Chair; Daniel L. Kelting, Committee Member; Daniel D. Richter, Committee Member
Upper Coastal Plain forest sites are characterized by highly weathered soils and intensive agricultural use. These conditions may predispose intensively managed sites to second rotation declines if managed carelessly. This study compared aboveground biomass and nutrient content changes between successive rotations of loblolly pine on the same site in the Upper Coastal Plain of Alabama and examined what first rotation factors were important in the biomass and nutrient accumulation in the second rotation. Individual tree biomass and nutrient content equations were compared for the first and second rotation. In addition, within tree nutrient concentration relationships were explored to evaluate their significance for whole tree nutrient content determinations. Representative trees from the diameter distribution were destructively sampled from each rotation. Foliage, branch, stemwood, and stembark tissues, were separated, sampled, and analyzed for nutrient concentrations. Green-field and oven-dry weights were used to calculate nutrient contents. Regression equations for individual tree tissues biomass and nutrient contents as a function of tree diameter and height were fitted for each rotation. Stand biomass and nutrient contents were estimated by applying these equations to stand inventory data for each rotation. Forest floor biomass and nutrient contents were evaluated for both rotations. Soil samples obtained when the first rotation stand was harvested were used to characterize total N and available pools for other mineral soil nutrients. Analyses of nutrient concentration relationships within the tree indicated that mobile nutrients concentrations of stemwood, bark, and branches decreased with distance from the top of the tree. Foliar nutrient concentrations and non-mobile nutrients for other tissues showed no patterns with tree height. Stemwood biomass regression equations were the same for the two rotations but nutrient content regressions differed. Foliage, branch, and bark biomass and nutrient content regressions also differed. Major differences between rotations were found for stemwood N and P; foliage, branch, and bark B concentrations, indicating reduced availability of these nutrients in the second rotation stand. Considering harvesting removals, micronutrient availability, especially B availability may be severely affected as a larger proportion of B, relative to other micronutrients was allocated to stemwood. Biomass and nutrient accumulation in the second rotation stand was highly correlated with soil exchangeable P at the end of the first rotation. The forest floor was a large C reservoir and a large nutrient sink for N, P, K, S Zn, and Cu.
Carbon storage and transport in fertilized loblolly pine (Pinus taeda) plantations on upland sandy and clayey soils.
(2004-06-27) Leggett, Zakiya Holmes; James A. Thompson, Committee Member; Felipe G. Sanchez, Committee Member; Daniel D. Richter, Committee Member; H. Lee Allen, Committee Chair; Daniel L. Kelting, Committee Co-Chair
Fertilization and soil texture may function independently or interactively to have a positive effect on a forest ecosystem's carbon (C) storage. Fertilization has been identified as an effective management strategy for sequestering additional atmospheric CO2 by increasing biomass accumulation in loblolly pine plantations. Fertilization may increase soil C sequestration as a beneficial result of enhancing peak leaf area index, which results in increased biomass production and return of litter. The ability of the soil to sequester the additional C fixed is largely dependent on the soil's capacity to retain and protect the C from respiration and leaching loss. Well-drained finer textured soils (clayey soils) have a higher C retention capacity than coarse textured soils (sandy soils). This study was conducted in 11-year old loblolly pine plantations on sandy and clayey soils with and without the addition of nitrogen and phosphorus fertilization applied at planting. Soil C pools were inventoried prior to planting and soil and forest floor C pools were inventoried 11 years after stand establishment. Tree heights and diameters were used to estimate above- and below-ground biomass. Dissolved organic carbon (DOC) from throughfall and forest floor leachate was measured in the 11th growing season. The chemical composition of DOC from the forest floor leachate was evaluated using liquid state proton nuclear magnetic resonance (1H NMR). After 11 years of stand development total ecosystem C increased by 24 Mg/ha on average across both sites (soils). Fertilization increased accretion by 25.3 Mg C/ha with the majority of the increase occurring in the biomass. The clayey site averaged 64% more total ecosystem C than the sandy site. Statistically, the mineral soil C in the surface 20-cm did not change during the 11 years of stand development, except for the significant decrease in soil C within the 10-20cm depth on the control plots of the sandy site. Fertilization did not have a significant effect on throughfall or forest floor leachate solution volume, DOC concentration, or DOC flux. The yearly flux of DOC that entered the forest floor and soil from throughfall (100 kg/ha/yr) and forest floor leachate (150 kg/ha/yr) was relatively small (6% of the sum of all fluxes evaluated). Based on the 1H NMR spectrum, fertilization may alter the chemistry of the DOC leaching from the forest floor by increasing the C constituents least resistant to microbial oxidation.
Effects of early intensive silviculture on wood properties of loblolly pine
(2003-07-17) Mora, Christian Ricardo; H. Lee Allen, Committee Chair; Richard F. Daniels, Committee Member; Bailian Li, Committee Member; David A. Dickey, Committee Member
Long-term effects of site preparation, early fertilization and weed control on selected wood properties of 22-23 year-old loblolly pine (Pinus taeda L.) were examined. Wood samples were obtained from four regeneration trials established by the North Carolina State Forest Nutrition Cooperative between 1978 and 1981 in southeastern USA. Twelve millimeter breast-height wood samples were extracted from a total of 675 trees (across sites) from five treatments: 1) low site preparation (control), 2) intensive site preparation, 3) intensive site preparation and fertilization, 4) intensive site preparation and weed control, and 5) intensive site preparation, fertilization and weed control. Specific gravity data were collected using an x-ray densitometer. All samples were scanned for ring specific gravity, ring earlywood specific gravity, ring latewood specific gravity and ring latewood proportion. Across sites and treatments, the transition zone between juvenile and mature wood based on latewood specific gravity was between rings 4 and 15 and the demarcation point between both types of wood varied from rings 12 to 15. Silvicultural treatments did not affect the transition age on two out of the four sites (rings 14 and 15). An increase of 2 years on the transition age was associated to intensive cultural treatments on one site and a decrease of 3-4 years was observed on the remaining site, suggesting a relationship between the patterns of growth with age and the proportion of juvenile wood. The proportion of juvenile wood was not significantly affected by early silviculture on two sites (< 2%) and on one site a 10% decrease on the amount of juvenile wood was observed as a result of intensive cultural treatments. The results suggested that where strong growth responses to fertilization and weed control were observed, the transition age between juvenile and mature wood was unaffected or decreased and when the strong growth responses were related to herbaceous weed control, the transition age increased in intensive silvicultural plots compared to control plots. Individual tree volume was significantly affected by intensive treatments. Positive responses ranged from 29 to 33%. Despite the increased growth showed by trees under intensive cultural treatments, wood properties were generally not significantly different from those observed on control plots. Intensive site preparation (HSP) and fertilization within intensive site preparation plots (F) resulted in reductions of earlywood specific gravity and total specific gravity, respectively. Weed control (H) showed little effect on most of the properties but on one site was related to an increase on weighted specific gravity. Intensive treatments, on average, resulted in small increases in weighted latewood specific gravity compared to low site preparation and the proportion of latewood was not affected by the treatments at all.
Environmental Constraints on Growth Phenology, Leaf Area Display, and Above and Belowground Biomass Accumulation of Pinus radiata (D. Don) in Chile
(2005-12-06) Rubilar, Rafael Alejandro; Phillip M Dougherty, Committee Member; Marcia L Gumpertz, Committee Member; H. Lee Allen, Committee Chair; Thomas R Wentworth, Committee Member; Bill Arthur Hoffmann, Committee Member
Environmental site-specific constraints on shoot, branch, and leaf area growth and phenology were investigated during the third and fourth growing seasons in two-year-old radiata pine plantations established under a factorial combination of soil preparation, fertilization, and weed control at three contrasting textural and climatic soil-site conditions in the Central Valley of Chile. During October 2002 and June 2005, biweekly measurements of foliage accretion, branch, and stem growth were obtained together with periodical evaluations of foliage senescence. At each site, tree growth, aboveground biomass, belowground biomass, total biomass, aboveground:belowground biomass ratio, and leaf area index increased mainly by weed control (WC). The large gradient of tree growth and biomass accumulation among sites, and within sites varying in response to WC, was mainly attributed to large differences in soil water availability and possibly atmospheric water demand differences within sites. A linear relationship was established between LAI and stand growth across sites. The slope of the relationship (stemwood growth efficiency, GE) varied from 2.9 m3ha-1year-1 to 6.8 m3ha-1year-1 per unit of leaf area, with lower growth efficiencies found on sites with the greater water constraints. Phenology of growth was little affected by site or silvicultural treatments. Seasonal differences in the patterns of growth were mainly observed among sites for diameter, with longer growing seasons at sites with lower water limitations. In contrast, strong site and silvicultural treatments effects were observed on tree morphology. Trees where water limitations were more severe exhibited fewer and shorter flushes of height growth. The negative effects of soil water limitations, were at least partially ameliorated by silvicultural treatments that had been applied three years previously. Resource availability constraints during the mid to late growing season affected diameter growth more than height growth. Phenology of fascicle elongation indicated that sites with water and nutritional constraints ended fascicle elongation earlier during a growing season. Phenology of fascicle senescence indicated that maximum needlefall occurred during the summer and autumn seasons. No differences in silvicultural treatments were observed in foliage accretion or senescence patterns. Foliage longevity increased for sites with water and nutrient limitations.
Factors Influencing Responses of Loblolly Pine Stands to Fertilization
(2005-08-08) Rojas, Julio Cesar; Jeffery A. Wright, Committee Member; Bronson P. Bullock, Committee Member; Marcia L. Gumpertz, Committee Member; H. Lee Allen, Committee Chair
Fertilization of pine plantations has increased dramatically in the last decade. Over 600,000 hectares are being fertilized annually to overcome chronic widespread nitrogen (N) and phosphorus (P) limitations. However, responses to fertilization vary widely since specific responses after fertilization for any particular stand will be the result of complex interactions of nutrients and rates applied, stand and site conditions at time of application, years since application, and climatic conditions after application. Stand, soil and forest floor (FF) responses to fertilizations were assessed at three different sites located in the 'flatwoods' area of southeast Georgia and northeast Florida after five years of repeated fertilizer additions. Significant leaf area index (LAI), stemwood growth and FF responses were found at all three sites. Leaf area index was double for some treated plots as compared to control plots (from 1.4 to 3.0), five year cumulative growth on treated plots almost tripled that of the control plots (32 to 89 cubic meter per hectare). Soil N availability increased dramatically soon after fertilization however, it decreased few months after application. Several nutrients affected growth at these three sites, N and P at all three sites and potassium (K) and manganese (Mn) at the Georgia study sites. Factors affecting growth efficiency (GE) of loblolly pine plantations across the southeast were examined using 86 studies sites with different climatic, edaphic and stand conditions. Two modeling approaches were developed, one where GE would change with levels of LAI (non-linear using Gompertz model) and a second where GE was independent of the level of LAI (linear model), in both cases significant reduction in RMSE (>200%) was achieved when parameters in the models were allowed to be functions of edaphic, climatic and stand characteristics. In conclusion, GE is a dynamic rather than static stand parameter; it changes with stand age, drainage, soil texture and climate. Current year climatic variables were better predictors of GE than long term climatic averages, indicating that the inter-annual variation on temperature and rainfall exerts great influence on GE. Further modeling efforts were undertaken to determine factors affecting the variation in growth responses to N+P fertilization in loblolly pine stands. By utilizing a standardization procedure on the original data, 66% of the variation in the standard response was explained by LAI, Foliar N, and growth efficiency. These variables are ecophysiological variables proposed as drivers of stand response to fertilizer application(s). Two other variables, quadratic mean diameter (Dq), and stand age were also significant predictors in the model.
Leaf Area Assessments of Overstory and Understory Vegetation in Pine Plantations Located in South Georgia and North Florida, US
(2007-04-11) Peduzzi, Alicia; H. Lee Allen, Committee Chair; Marcia L. Gumpertz, Committee Member; Stacy A. C. Nelson, Committee Member; Randolph H. Wynne, Committee Member
Leaf Area Index (LAI) was estimated in summer 2005 and winter 2006 for overstory and understory in loblolly pine and slash pine plantations at ages 7 and 10 year-old and on poorly, somewhat poorly and moderately-well drained soils located in the flatwoods region. Additionally, stand and site factors such as basal area, pine dominant height, understory height and understory coverage were estimated for each of the 40 plots established, and leaf area index and vegetation indices (SR, NDVI, VI and EVI) were calculated using remote sensing imagery. The objectives of this study were to determine the understory (competing vegetation) and overstory (crop-trees) leaf area index, to relate the variation in understory and overstory LAI to stand and site factors and to examine the relationships among understory and overstory leaf area index and spectral reflectance data captured by satellite imagery. Leaf area index values observed for the overstory were low in most of the plots (around 2 m2m-2 in slash pine and around 3 m2m-2 in loblolly pine), while the understory LAI was very high (around 2 m2m-2), which can be attributed to the lack of canopy closure observed in all plots. A negative relationship was observed between the overstory and the understory, where the higher the understory LAI the lower the overstory LAI. No significant differences were found in the understory LAI values across soil drainage classes. Low heights and short crown lengths were generally observed and could be explained by nutrient deficiency in most of the sites; which could be attributable to the belowground competition for water and nutrients. LAI and basal area were not correlated. Total LAI (overstory LAI plus understory LAI) estimated values on the ground were high and weakly correlated with the Landsat-derived vegetation indices, and the LAI values estimated with a LAI model were typically half of the values estimated on the ground. These results could be influenced by the contribution of different backgrounds, such as soil moisture and understory vegetation, plus the saturated response of the vegetation indices at high LAI values. Significant correlations were observed between the vegetation indices (SR and NDVI) and stand and site factors, suggesting that the satellite derived indices were more related to the stand biophysical parameters than in situ LAI estimates.
Quantifying the Coarse Root Biomass of Intensively Managed Loblolly Pine Plantations.
(2005-06-15) Taylor, Ashley E; H. Lee Allen, Committee Chair; Chris Maier, Committee Member; Michael Wagger, Committee Member
Nearly all of the C accumulation during a typical forest rotation is in plant biomass and the forest floor. Most biomass studies focus on aboveground C accumulation, and there is little information about biomass-C accumulation belowground. In older, loblolly pine forests, the majority of root biomass is in coarse roots, and coarse roots persist longer after harvest than aboveground biomass and fine roots. The main objective of this research was to assess the belowground carbon accumulation in coarse roots of a managed loblolly pine (Pinus taeda L.) plantation, which was subjected to different levels of management intensities. Additional objectives included determining the depth of excavation required to sample a majority of the coarse roots, quantifying coarse roots that were not associated with the taproots of either hardwoods or planted pines, developing an inter-specific hardwood regression relating diameter at breast height to coarse root biomass, and estimating total coarse root biomass per hectare. Estimates of total belowground biomass ranged from 56.4 to 62.4 Mt ha-1and were not affected by treatment. Pine and hardwood taproot biomass was affected by treatment, with vegetation control and disking significantly increasing pine taproot biomass and decreasing hardwood taproot biomass. Pine coarse roots not associated with the taproot were unaffected by treatment, but hardwood coarse roots not associated with the taproot were significantly reduced with vegetation control. Necromass was substantially lower than between-tree biomass, indicating that the decomposition of coarse root biomass from the previous stand is fairly rapid for coarse roots not associated with the taproot. Total aboveground biomass was significantly affected by vegetation control, with the lowest production on CHNO plots (180.2 Mt ha-1) and the highest production on plots receiving complete vegetation control, DIVC (247.3 Mt ha-1). Coarse root biomass ranged from 19 to 24% of total biomass. Silvicultural practices that increased aboveground pine productivity by reducing hardwoods did not increase total coarse root biomass C. Additionally, there is no evidence that coarse roots provide long-term C storage because they decompose rather quickly after harvest and during subsequent rotations.
Understanding Forest Floor Accumulation and Nutrient Dynamics in a Loblolly Pine Plantation Regenerated with Varying Forest Floor and Slash Retention
(2005-10-29) Zerpa, Jose Luis; Robert Campbell, Committee Member; H. Lee Allen, Committee Chair; Thomas Fox, Committee Member; Jenniffer Bennett, Committee Member; Deanna Osmond, Committee Member
The effects of varying forest floor and slash retention at time of regeneration were evaluated in a loblolly pine study established near Millport, Alabama 10 years after the retention treatments were imposed. The objectives were to determine the effects of removing, leaving unaltered, or doubling the forest floor and slash material, on forest floor mass, nutrient dynamics, litterfall, foliar nutrition, mineral soil properties, and stand yield. The parameters measured included ash-free weight, nitrogen (N), carbon (C), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), manganese (Mn), sulfur (S), boron (B), copper (Cu), and zinc (Zn) concentrations in the forest floor, litterfall, and foliar samples, N extracted from ion exchange membranes (IEM) from the forest floor, potential mineralized N and IEM-N, total C and N, exchangeable Ca, Mg, K, and sodium (Na), extractable P and Mn, pH, and bulk density from the mineral soil, and tree volume. Forest floor mass and nutrient content in the doubled treatment were significantly greater than in the other two treatments. The doubled accumulated 25, 45 and 350% more forest floor mass and 56, 56, and 310% more N than the control treatment in the L, F, and H layers, respectively, the other nutrients followed similar accumulation patterns. IEM and potential mineralized NO₃--N in the mineral soil were significantly higher in the doubled treatment. No significant treatment differences were found in the mineral soil properties assessed. The positive effect of doubling the forest floor on soil N availability was well reflected by the fact that the greatest foliage production (indicated by litterfall) and stand yield were found on this treatment. In addition, this linkage was indicated by strong positive correlations among stand yield, litterfall, potential nitrification, and IEM extractable NO₃--N. Greater amounts of available N in the mineral soil and most likely in the forest floor on the doubled treatment apparently resulted in a feed forward effect with greater growth and in turn greater litterfall and accumulation of new forest floor material (L and F layers). In addition, the retention of more forest floor material (at least in the manner it was done in this study) apparently resulted in slower decomposition of the retained material in a non linear proportion relative to its original mass. This in turn has resulted in long term increases in soil available N through the 10th year following plantation establishment.
Using Hyperspectral Remote Sensing to Estimate Leaf Area Index of Loblolly Pine Plantations
(2003-07-25) Flores, Francisco Jose; Jerry Davis, Committee Member; Daniel Kelting, Committee Member; H. Lee Allen, Committee Chair; Heather Cheshire, Committee Member; Montserrat Fuentes, Committee Member
High spectral resolution (Hyperspectral) and multispectral imagery was used to examine the spectral response of loblolly pine with contrasting LAI and foliar nitrogen concentration. The research studies included very different stand structures (age, number and size of the trees). As a result of treatments applied, seasonal, stand and site variation, the range in LAI (0.4 — 3.6 m2 m2) and foliar nitrogen concentration (0.79 — 1.62%) on our study covered most of the range observed in midrotation loblolly pine plantations. Hyperspectral data was used to calculate narrowband vegetation indices (VIs) based on reflectance in the red (R) and near infrared (NIR). LAI was linearly related to the simple ratio (SR) vegetation index, the relationship was not affected by site, stand structure or season. We also found a strong relationship between SR calculated from hyperspectral data and SR calculated from readily available Landsat 7 ETM+ data. Using that relationship, we determine an equation to estimate LAI from Landsat 7 ETM+ data. Hyperspectral data was also used to estimate foliar nitrogen concentration and content of loblolly pine. We found a stronger relationship between nitrogen content and reflectance data than nitrogen concentration and reflectance data.
Vegetation Differences in Neighboring Old Growth and Second Growth Rich Coves in Joyce Kilmer Wilderness Area: A Thirty-two-year Perspective
(2007-06-22) Jackson, Barry Clayton; Thomas R. Wentworth, Committee Member; J. Dan Pittillo, Committee Member; David L. Loftis, Committee Member; H. Lee Allen, Committee Chair
I surveyed vegetation in neighboring old growth and second growth rich coves in the Joyce Kilmer Wilderness Area, North Carolina. This data, combined with data from three previous studies, provide a 32 year perspective of stand structure, species frequencies of occurrence at the 1 m2 scale, and species richness at the 1 m2 scale. I sampled one 0.1 ha plot in each cove. I subdivided each plot into ten 10 m by 10 m modules and sampled percentage cover of all species present in each module, plus stem diameter for woody stems. Additionally, I sampled presence absence in a variety of subplots at scales of 0.01 m2, 0.1 m2, 1 m2, 10 m2, and 100 m2. A cohort of 30-40 cm diameter at breast height Liriodendron tulipifera trees dominated the second growth cove, while the old growth site had a broader mix of species with an inverse J-shape diameter distribution. In both rich coves, the frequencies of occurrence at 1 m2 appeared highly variable for individual species between sample years and distances of 200 m or less. The four studies provided species richness comparisons at the 1 m2 scale between the old growth and second growth (at ages 16, 35, 39, and 47 years). I concluded that the differences in second growth species richness between studies demonstrated rich cove forest succession. High species richness following disturbance reflected a surge of opportunistic species (age 16). The opportunistic species declined following canopy closure, resulting in significantly lower species richness (age 35). After further stand development, a resurgence of late-succession species increased species richness to equal levels with old growth (age 39 and 47). Finally, I examined species-area relationships between the two coves, and between these rich coves and the regional average. Arrehnius model (log10 species: log10 area between the scales of 0.1 m2 to 1000 m2) species-area curves indicated no difference in species-area relationships between the two coves. Collectively, these two rich coves had a significantly higher intercept but no difference in regression slope from the regional average. These findings reflect an average rate of species accumulation in the Joyce Kilmer coves, but with higher-than-average species density at all measured scales.