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

TLDR: Examining the hypotheses that growth, light use efficiency, and volume growth per unit heat sum is the same for native and exotic plantations found that Pinus taeda grows faster and has a higher carrying capacity when grown outside its native range.

About: This article is published in Forest Ecology and Management.The article was published on 2018-10-01 and is currently open access. It has received 18 citations till now.

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Table 4 Parameter estimates for significant terms in the light use efficiency equation where I is absorbed photosynthetically active radiation, G is genetic entry (clones 1-4 (C1-C4), mass control-pollinated (MP), open pollinated (OP)), D is density (618, 1236, 1854 trees ha−1) and * denotes an interaction. These equations were used to generate regression lines in Fig. 2.

Table 2 Statistical summary (p values) for stand and growth increment metrics for three sites (Virginia (VA), North Carolina (NC) and Brazil (BR)) where Pinus taeda was planted using the same six genetic entries and three initial density levels. Growth data for all sites are after 5 years and the fifth growing season increment. Leaf area data for the BR site are from the fifth year, leaf area data for the VA and NC sites are for the eighth year.

Fig. 2. Light use efficiency (volume growth per unit absorbed photosynthetically active radiation (PAR)) for the eighth growth season at the Virginia (VA) and North Carolina (NC) sites and the fifth growing season at the Brazil (BR) site where the same Pinus taeda genetic entries were planted at three initial densities. Regression lines are for density main effects (a) where 618, 1236 and 1854 represent the corresponding density treatments (in trees ha−1) with the open pollinated genetic entry, and genetic entry main effects (b) (Clones 1-4 (C1–C4), MP (mass control pollinated), and OP (open pollinated)) with 1854 tree ha-1. Site was not a significant factor in the relationship. Each point represents one plot.

Table 3b Genetic entry treatment least square means for stand and growth increment metrics for three sites (Virginia (VA), North Carolina (NC) and Brazil (BR)) where Pinus taeda was planted using the same six genetic entries (4 clones (C1, C2, C3, C4), a mass-control pollinated family (MP), and an open pollinated family (OP)) and three initial density levels (618, 1236, 1854 trees ha−1). Growth data for all sites are after five years and the fifth growing season increment. Leaf area data for the BR site are from the fifth year, leaf area data for the VA and NC sites are for the eighth year. Lower case letters indicate means separation for the main effect treatment within a site.

Table 3b Genetic entry treatment least square means for stand and growth increment metrics for three sites (Virginia (VA), North Carolina (NC) and Brazil (BR)) where Pinus taeda was planted using the same six genetic entries (4 clones (C1, C2, C3, C4), a mass-control pollinated family (MP), and an open pollinated family (OP)) and three initial density levels (618, 1236, 1854 trees ha−1). Growth data for all sites are after five years and the fifth growing season increment. Leaf area data for the BR site are from the fifth year, leaf area data for the VA and NC sites are for the eighth year. Lower case letters indicate means separation for the main effect treatment within a site.

Fig. 3. Cumulative volume and cumulative degree hours (> 5 °C) where ambient temperature was between 5 and 38 °C, photosynthetically active radiation (PAR) was greater than zero (daytime) and if nighttime temperatures were below 0 °C no hours are counted the next day for three sites (Virginia (VA), North Carolina (NC) and Brazil (BR)) where the same Pinus taeda genetic entries were planted at three initial densities (a). In Panel b cumulative degree hours were estimated as in Panel a and included an adjustment for vapor pressure deficit (VPD) where hours when VPD exceeded 1.5 kPa were not included. Regression lines for each sites are shown. Each point is a site mean.

Frequently asked questions

Q1. What are the contributions in "A common garden experiment examining light use efficiency and heat sum to explain growth differences in native and exotic pinus taeda" ?

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.