Browsing by Author "Stape, Jose L."
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- A common garden experiment examining light use efficiency and heat sum to explain growth differences in native and exotic Pinus taedaAlbaugh, 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.
- Using seasonal measurements to inform ecophysiology: extracting cardinal growth temperatures for process-based growth models of fiveWatt, Michael S.; Rubilar, Rafael A.; Kimberley, Mark O.; Kriticos, Darren J.; Emhart, Veronica; Mardones, Oscar; Acevedo, Manuel; Pincheira, Matias; Stape, Jose L.; Fox, Thomas R. (2014-06-11)Background Development of a relatively simple growth modelling approach for plantation species that allows derivation of cardinal (base, optimum and ceiling) air temperatures for growth, whilst accounting for changes in organism size, would represent a considerable advance over existing models. Such an approach would provide insight into species phenology and, in an agronomic setting, allow growers to closely match species to sites. Here, a model is described that can be used to predict seasonal variation in growth and cardinal air temperatures from simple seasonal measurements at a single site. Methods The model was applied to data from an irrigated trial comprising two Eucalyptus species and three Eucalyptus crosses. Using measurements of mean daily air temperature data and stem volume, taken over a two year period, the model was fitted to the data and used to estimate cardinal air temperatures for the five species/crosses. Results The model predictions corresponded well to the actual data for all five species/crosses, with R 2 ranging from 0.993 to 0.999. The optimum air temperature, T o, for E. camaldulensis x E. globulus of 26.9°C significantly exceeded T o for the other four species/crosses, where T o ranged from 15.4 to 18.7°C. As T o for E. camaldulensis x E. globulus was close to the highest mean daily air temperature recorded at the study site, the air temperature modifier for this species was almost always sub-optimal and consequently this cross was not well matched to the site. In contrast, T o for the other four species/crosses were considerably closer to the mean air temperature of the site with T o for E. nitens most closely approximating the mean air temperature (15.4 vs. 13.0°C). Conclusion The described approach can be used to account for complex variation in seasonal growth patterns and provides insight into how well a species may be matched to a particular site. As climatic information is available at a range of scales (from local to global), this type of model is likely to be useful for producing maps that describe species growth and areas of optimal suitability.