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Browsing by Author "Raymond, Jay E."

Now showing 1 - 3 of 3
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    A common garden experiment examining light use efficiency and heat sum to explain growth differences in native and exotic Pinus taeda
    Albaugh, Timothy J.; Fox, Thomas R.; Maier, Christopher A.; Campoe, Otavio C.; Rubilar, Rafael A.; Cook, Rachel L.; Raymond, Jay E.; Alvares, Clayton A.; Stape, Jose L. (2018-10-01)
    Previous work indicates that Pinus taeda L. grows faster and has a higher carrying capacity when grown outside its native range. We were interested in examining the hypotheses that growth, light use efficiency (volume growth and absorbed photosynthetically active radiation relationship, LUE) and volume growth per unit heat sum is the same for native and exotic plantations. To test these hypotheses, we installed a common garden experiment where the same six genetic entries of P. taeda (four clonal varieties, one open pollinated family and one control mass pollinated family) were planted at three densities (618, 1235, and 1853 stems ha(-1)) with three or four replications at three sites (Virginia (VA), and North Carolina (NC) in the United States and Parana State in Brazil (BR)). The VA and BR sites were outside the native range of P. taeda. After five years of growth, the BR site had larger trees and stand scale basal area and volume were increasing faster than the other sites. Site did not affect LUE but density and genetic entry did. The sites were at different latitudes but the average photosynthetically active radiation at the top of the canopy was similar for the years when all sites were operational, likely because the BR site receives more rain annually and the cloudiness associated with the rain may have reduced available light. We estimated an hourly heat sum where the daytime temperature was between 5 and 38 degrees C, hours where vapor pressure deficit exceeded 1.5 kPa and days following nights where nighttime temperatures were less than 0 degrees C were excluded. Site was significant for the cumulative volume and heat sum relationship, for a given level of cumulative degree hours the sites ranked BR > VA > NC in cumulative volume. The different growth per unit of degree hours for each site indicated that something other than the heat sum was causing the observed difference in growth. Other factors including respiration and extreme climatic conditions may contribute to growth differences per unit degree hour and including these differences in the analysis would require a more detailed modeling effort to examine. The sites used in this study are ideally suited to continue testing additional hypotheses to explain the different growth between native and exotic P. taeda plantations because they have the same genotypes at all sites and consequently eliminate differences in genetics as a potential explanation for observed growth differences.
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    Understanding the Fate of Applied Nitrogen in Pine Plantations of the Southeastern United States Using 15N Enriched Fertilizers
    Raymond, Jay E.; Fox, Thomas R.; Strahm, Brian D. (MDPI, 2016-11-11)
    This study was conducted to determine the efficacy of using enhanced efficiency fertilizer (EEFs) products compared to urea to improve fertilizer nitrogen use efficiency (FNUE) in forest plantations. All fertilizer treatments were labeled with 15N (0.5 atom percent) and applied to 100 m2 circular plots at 12 loblolly pine stands (Pinus taeda L.) across the southeastern United States. Total fertilizer N recovery for fertilizer treatments was determined by sampling all primary ecosystem components and using a mass balance calculation. Significantly more fertilizer N was recovered for all EEFs compared to urea, but there were generally no differences among EEFs. The total fertilizer N ecosystem recovery ranged from 81.9% to 84.2% for EEFs compared to 65.2% for urea. The largest amount of fertilizer N recovered for all treatments was in the loblolly pine trees (EEFs: 38.5%–49.9%, urea: 34.8%) and soil (EEFs: 30.6%–38.8%, urea: 28.4%). This research indicates that a greater ecosystem fertilizer N recovery for EEFs compared to urea in southeastern pine plantations can potentially lead to increased FNUE in these systems.
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    Use of Stable Isotopes to Trace the Fate of Applied Nitrogen in Forest Plantations to Evaluate Fertilizer Efficiency and Ecosystem Impacts
    Raymond, Jay E. (Virginia Tech, 2016-03-03)
    This study assessed five fertilizer treatments (control – no fertilizer, urea, urea treated with N-(n-butyl) thiophosphoric triamide (NBPT), coated urea + NBPT (CUF), polymer coated urea (PCU) ) during two application seasons (spring, summer) to: 1) compare fertilizer nitrogen (N) losses (see Chapter 2); 2) evaluate temporal N uptake patterns of loblolly pine (see Chapter 3); and 3) evaluate fertilizer N cycling and partitioning in a loblolly pine ecosystem (see Chapter 4). Chapter 2 results showed enhanced efficiency fertilizers (EEFs) significantly reduced ammonia (NH3) volatilization losses compared to urea. Mean NH3 volatilization after spring fertilization ranged from 4% to 26% for EEFs versus 26% to 40% for urea, and 8% to 23% for EEFs versus 29% to 49% for urea in summer. Chapter 3 results showed an increase in timing and development of foliage in fertilized compared to unfertilized plots. In addition, the cumulative N uptake by loblolly pines increased over the entire growing season from N originating from fertilizer and natural sources. Chapter 4 results showed greater fertilizer N recovery for EEFs in both spring and summer (80%, 70-80% respectively) compared to urea (60%, 50% respectively) with most fertilizer N recovered from mineral soil (20% to 50%) and loblolly pines (10% to 50%). Three primary conclusions come from this research: 1) EEFs reduce NH3 volatilization after N fertilization compared to urea regardless of application timing and weather conditions (see Chapter 2); 2) N uptake by loblolly pines increases over the entire growing season after N fertilization (see Chapter 3); more fertilizer N remains in the ecosystem with EEFs compared to urea with most fertilizer N remaining in the soil (see Chapter 4). From these findings, we hypothesize that the EEFs in this study: 1) reduce ammonia volatilization which 2) translates to an increase in fertilizer nitrogen remaining in the loblolly pine plantation system that 3) increases the amount of plant available nitrogen for an extended period into the stand rotation and 4) increases fertilizer nitrogen use efficiency (FNUE) for all enhanced efficiency fertilizers investigated in this study compared to the conventional form of fertilizer N used in forestry, urea.