A common garden experiment examining light use efficiency and heat sum to explain growth differences in native and exotic Pinus taeda

Abstract

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 Paraná 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°C, hours where vapor pressure deficit exceeded 1.5 kPa and days following nights where nighttime temperatures were less than 0°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.

Crown architecture, crown leaf area distribution, and individual tree growth efficiency vary across site, genetic entry, and planting density

“…The BR trees grew faster than the VA and NC trees, in agreement with other data reported from this study (Albaugh et al 2018). Consequently, stands in the two regions were developing at different rates.…”

“…Soils at the VA, NC, and BR sites were well-drained, fine, kaolinitic, mesic Typic Kanhapludults; somewhat poorly drained, fine-loamy siliceous, semiactive, thermic Typic Paleaqualts; and well-drained Inceptisols and Hapludults, respectively. The average annual temperature during the study was 13.5, 16.5 and 16.8 °C, with average precipitation of 1218, 1144, and 1580 mm year −1 for the VA, NC, and BR sites, respectively (Albaugh et al 2018). The BR site rarely experiences extreme (below 0 °C and higher than 30 °C) temperatures, whereas the sites in the US regularly experience these extremes during the annual course of seasonal variation.…”

“…We installed an experiment with a split-plot design with three or four replications at three sites (Albaugh et al 2018;Vickers et al 2011 (− 26.1904805 o , − 49.49631 o ). Soils at the VA, NC, and BR sites were well-drained, fine, kaolinitic, mesic Typic Kanhapludults; somewhat poorly drained, fine-loamy siliceous, semiactive, thermic Typic Paleaqualts; and well-drained Inceptisols and Hapludults, respectively.…”

“…Over time, these improvements have resulted in large increases in productivity. However, P. taeda growth in parts of South America and Hawaii where it would be considered an exotic species outside its native range can be substantially greater than that in the southeastern US (Albaugh et al 2018;Harms et al 2000;Samuelson et al 2010;Wallinger 2002). For example, at 5 years of age, volume increment at a site in Brazil (40 m 3 ha −1 year −1 ) was more than twice that of sites in the southeastern US (average of 15 m 3 ha −1 year −1 ) (Albaugh et al 2018).…”

“…However, P. taeda growth in parts of South America and Hawaii where it would be considered an exotic species outside its native range can be substantially greater than that in the southeastern US (Albaugh et al 2018;Harms et al 2000;Samuelson et al 2010;Wallinger 2002). For example, at 5 years of age, volume increment at a site in Brazil (40 m 3 ha −1 year −1 ) was more than twice that of sites in the southeastern US (average of 15 m 3 ha −1 year −1 ) (Albaugh et al 2018). A number of hypotheses have been proposed to explain these differences in growth, including growing season length, sunlight intensity, soil characteristics, lack/presence of pathogens, sun angle, genetic entry, stand structure, and crown architecture (Harms et al 1994;Wallinger 2002).…”