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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

01 Oct 2018-Forest Ecology and Management (Elsevier)-Vol. 425, pp 35-44

TL;DR: 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.

AbstractPrevious 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 °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.

Summary (2 min read)

1. Introduction

  • Environmental variables have large effects on tree growth.
  • At the same time, identifying driving factors or relationships similar to LUE and heat sums that influence growth will make this analysis applicable to other species.

2.1. Experimental design

  • The authors installed a split split-plot design with three or four replications at three sites (Vickers et al., 2011).
  • The second site (VA) had four replications and was in the Piedmont of Virginia, United States at the Reynolds Homestead (36.64232°, −80.1546138°) in an area where P. taeda grows successfully but is outside the native range of the species.
  • Plots with different initial density or genotypes were adjacent to each other.
  • When on-site data were not available, the nearest meteorological station available from CRONOS (2015) was used to fill in data for the VA and NC sites.

2.2. Statistical analyses

  • To examine their first hypothesis, the authors used a mixed model approach (PROC MIXED (SAS-Institute 2002)) to test for treatment effects for all sites after five years for diameter, diameter increment, height, height increment, basal area, basal area increment, volume, volume increment, and stand density.
  • Random effects were block and genetic entry by block (Schabenberger, 2013).
  • Non-significant terms were dropped from the model until all terms in the model were significant.
  • For a given hour, if the ambient temperature was 5 °C, it was during the day and the previous nighttime temperatures were above zero then the heat sum for that hour was 5–5 or 0.
  • = ∗CV DH S DH S where CV was cumulative volume in m3 ha−1 for each site at year end as an average of all individual plot estimates of volume, DH was the cumulative degree hour statistic and S was a class variable indicating each site, also known as The full model was.

3. Results

  • Site effects were significant for all growth metrics (diameter, diameter increment, height, height increment, basal area, basal area increment, volume, volume increment, stand density, peak and off-peak leaf area index) (Table 2).
  • Early survival was less for these genetic entries likely because they were planted as bare root seedlings whereas the other genetic entries at the VT and NC sites were containerized seedlings.

4. Discussion

  • Site did affect growth and, consequently, the authors rejected their first hypothesis.
  • At the same time, the diameter increment at the BR site was growing on a larger tree indicating that the total amount of stem wood required to produce this amount of diameter increment was much greater than that at the VA and NC sites and this was reflected in the stand scale measurements.
  • Density significantly influenced the intercept of the LUE relationship where increasing the number of trees per hectare increased the volume growth per unit of absorbed light (Fig. 2a and Table 4).
  • Clearly, it was warmer at the NC site (Table 1 and Fig. 1) and when examining only degree hours and accounting for potential loss of growth from cold temperatures, the NC site had considerably more degrees hours than the other sites.
  • Respiration increases with increasing temperature (Maier, 2001), which could reduce the carbon available for stem growth with the generally higher temperature at the NC site.

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Contents lists available at ScienceDirect
Forest Ecology and Management
journal homepage: www.elsevier.com/locate/foreco
A common garden experiment examining light use eciency and heat sum
to explain growth dierences in native and exotic Pinus taeda
Timothy J. Albaugh
a,
, Thomas R. Fox
b
, Chris A. Maier
c
, Otávio C. Campoe
d
, Rafael A. Rubilar
e
,
Rachel L. Cook
f
, Jay E. Raymond
a
, Clayton A. Alvares
g
, Jose L. Stape
h,i
a
Virginia Tech, Department of Forest Resources and Environmental Conservation, 228 Cheatham Hall, Blacksburg, VA 24061, USA
b
Forest Productivity and Sustainability, Forest Research Center, Rayonier Inc., Yulee, FL 32097, USA
c
USDA Forest Service, 3041 Cornwallis Road, Research Triangle Park, NC, USA
d
Federal University of Santa Catarina, Curitibanos, SC, Brazil
e
Cooperativa de Productividad Forestal, Facultad de Ciencias Forestales, Universidad de Concepción, Victoria 631, Casilla 160-C, Concepción, Chile
f
Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC 27695-8008, USA
g
Forestry Science and Research Institute IPEF, Piracicaba, SP 13400-970, Brazil
h
Department of Forest Science, Sao Paulo State University and Botucatu, SP, Brazil
i
Department of Forest Sciences, University of Sao Paulo, Piracicaba, SP, Brazil
ARTICLE INFO
Keywords:
Absorbed light
Density
Genotype
Natural range
Vapor pressure decit
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 eciency (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 ve 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
aect LUE but density and genetic entry did. The sites were at dierent latitudes but the average photo-
synthetically 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 decit exceeded 1.5 kPa and days following nights where nighttime tem-
peratures were less than 0 °C were excluded. Site was signicant for the cumulative volume and heat sum
relationship, for a given level of cumulative degree hours the sites ranked BR > VA > NC in cumulative vo-
lume. The dierent growth per unit of degree hours for each site indicated that something other than the heat
sum was causing the observed dierence in growth. Other factors including respiration and extreme climatic
conditions may contribute to growth dierences per unit degree hour and including these dierences in the
analysis would require a more detailed modeling eort to examine. The sites used in this study are ideally suited
to continue testing additional hypotheses to explain the dierent growth between native and exotic P. taeda
plantations because they have the same genotypes at all sites and consequently eliminate dierences in genetics
as a potential explanation for observed growth dierences.
1. Introduction
Environmental variables have large eects on tree growth. Trees
intercept light and transform light energy into biomass and this
transformation is limited by environmental factors aecting photo-
synthesis (Cannell, 1989b) and light interception is controlled by leaf
area (Vose and Allen 1988 ). Growth per unit intercepted light (light use
eciency (LUE)) has been used to understand how treatments, and
https://doi.org/10.1016/j.foreco.2018.05.033
Received 12 March 2018; Received in revised form 10 May 2018; Accepted 15 May 2018
Corresponding author.
E-mail addresses: Tim_Albaugh@vt.edu (T.J. Albaugh), tom.fox@rayonier.com (T.R. Fox), cmaier@fs.fed.us (C.A. Maier), otavio.campoe@ufsc.br (O.C. Campoe),
rafaelrubilar@udec.cl (R.A. Rubilar), rlcook@ncsu.edu (R.L. Cook), jayer11@vt.edu (J.E. Raymond).
Forest Ecology and Management 425 (2018) 35–44
Available online 22 May 2018
0378-1127/ © 2018 Elsevier B.V. All rights reserved.
T

changes in climate and location inuence growth (Albaugh et al., 2016;
Monteith 1977; Waring et al., 2016). Heat units have been used since
the 1700s to predict development and growth in crop species (e.g.
(McMaster and Wilhelm 1997)) and more recently in tree species (e.g.
(Way and Oren 2010)). Heat units can be simply summing of tem-
peratures within a specic threshold or they may include other vari-
ables to limit the summing (e.g. vapor pressure decit (VPD) (Sangines
de Carcer et al., 2017) when it is compared to some point of develop-
ment or cumulative growth. The amount and quality of light and
temperature patterns change when moving a species from one location
to another. Developing an understanding of how light and temperature
aect a given species would help predict how a species will behave in a
new environment. For example, the Köppen climate classication
system is used to identify similar environmental niches for exotic
planting of Eucalyptus species to improve the likelihood a species will be
planted successfully in other environments (Goncalves et al., 2013). At
the other end of the spectrum, there are species that are already planted
in exotic locales and do well (e.g. (Waring et al., 2008)). In this case,
improving our understanding of conditions that make a species grow
better as an exotic may help improve management in the native range.
At the same time, identifying driving factors or relationships similar to
LUE and heat sums that inuence growth will make this analysis ap-
plicable to other species. Pinus taeda L. is one species that may grow
extremely well outside its native range (Wallinger, 2002). This species
is one of the worlds most important commercial species, a native to
North America where it is responsible for about 60% of forestry pro-
duction in the United States (Prestemon and Abt, 2002). Future climate
change may inuence the species range in and near its native range
(Susaeta et al., 2014). Given that it is already planted extensively in
areas where it grows well as an exotic (Argentina and Brazil), P. taeda
would be a useful test case to compare native and exotic plantings to
develop a better understanding of the factors driving growth. Under-
standing what drives superior exotic growth may permit improvement
in silviculture of native grown P. taeda and help relieve pressure on the
land base from an increasing population and an increase in demand for
forest services predicted in the future (Susaeta et al., 2014).
From the 1940s to the 2000s, improvement in silvicultural prac-
tices greatly increased estimated productivity of P. taeda plantations
grown in the species native range in the southeastern United States
(Fox et al., 2007). There is evidence that maximum growth for the
species in its native range is about 16 Mg ha
1
yr
1
(mean annual in-
crement) (40 m
3
ha
1
yr
1
, assuming 400 kg m
3
wood density
(Antony et al., 2014)) given that additional silvicultural inputs do not
increase productivity beyond this amount (Zhao et al., 2016). Typical
mean annual growth rates for P. taeda in the southeastern United States
range from 16 to 33 m
3
ha
1
yr
1
(Zhao et al., 2016). However, the
theoretical maximum growth for P. taeda was estimated at
30 Mg ha
1
yr
1
mean annual yield (75 m
3
ha
1
yr
1
)(Farnum et al.,
1983). When P. taeda is grown outside its native range apparent pro-
ductivity is much higher. For example, P. taeda mean annual growth
rates of 50, 56 and 59 m
3
ha
1
yr
1
for stands in Brazil have been re-
ported (Barrichelo et al., 1977; Leite et al., 2006; Wallinger 2002). In
Argentina, Pezzutti (2011) reported mean annual volume growth up to
45 m
3
ha
1
yr
1
. Cubbage et al. (2007) estimated that mean annual
increments of 40 and 18 m
3
ha
1
yr
1
were possible in Brazil and the
United States, respectively, current annual increments would be higher.
A number of hypotheses to explain better exotic plantation growth
have been proposed. Rapid growth in Brazil was attributed to a longer
growing season, greater sunlight intensity, better soils and lack of pa-
thogens (Wallinger 2002). Harms et al. (1994) suggested that high solar
radiation intensities and high sun angles may be responsible for better
growth and noted that genetic characteristics may play a role in the
dierences observed between native and exotic plantations. Physiolo-
gical assessments (leaf light-saturated net photosynthesis, dark re-
spiration, stomatal conductance and quantum yield) completed on P.
taeda trees in exotic locations (Hawaii and Brazil) were comparable to
those reported in the native range (Samuelson et al., 2010). Samuelson
et al. (2010) suggested that better growth in Hawaii may be related to a
more favorable climate permitting year-round growth, high nutrient
availability, increased ushing and less belowground allocation.
However, few hypotheses have been tested to explain the dierent
growth between native and exotic plantations. Foliage longevity was
examined for P. taeda in North Carolina and in Corrientes, Argentina.
More foliage was displayed for a shorter time per fascicle in Argentina
and while study inference was limited (only one exotic and one native
site with dierent genotypes at each site) most fascicles at both sites
survived for two growing seasons, the one in which they were produced
and the following one (Albaugh et al., 2010 ). Waring et al. (2008) used
a combination of modeling and direct measurements to determine that
summer drought and evaporative demand limitations in native Dou-
glas- r(Pseudotsuga menziesii (Mirb.) Franco), limit growth to
30 m
3
ha
1
yr
1
in managed plantations in its native range in western
Oregon in the United States compared to 50 m
3
ha
1
yr
1
in exotic
plantations in New Zealand from the same seed source that do not
experience these moisture limitations. No studies were found in the
literature where the same genotypes were planted in the native range
and in exotic locations that would permit testing hypotheses to explain
the dierences in growth and carrying capacity observed between the
same species planted in native and exotic locations.
Consequently, we were interested in examining growth, LUE and
heat sums in P. taeda grown in native and exotic plantations where the
genotypes were the same in both locations. Specically, we examined
these hypotheses for P. taeda: (1) Growth is the same for native and
exotic plantations; (2) LUE is the same for native and exotic plantations
(site does not aect the volume growth and absorbed photo-
synthetically active radiation relationship); (3) heat sum per unit of
volume growth is the same for native and exotic plantations (site does
not aect the cumulative volume and degree hour relationship).
2. Methods
2.1. Experimental design
We installed a split split-plot design with three or four replications
at three sites (Vickers et al., 2011). The rst site (NC) with three re-
plications was selected in the Atlantic Coastal Plain of North Carolina,
United States in Bladen Lakes State Forest at (34.83133°, 78.5873°) in
the native range of P. taeda near where the genetic material used in the
study was sourced. The second site (VA) had four replications and was
in the Piedmont of Virginia, United States at the Reynolds Homestead
(36.64232°, 80.1546138°) in an area where P. taeda grows success-
fully but is outside the native range of the species. The third site (BR)
was in Paraná State in Brazil (26.1904805°, 49.49631°) with three
replications on land owned by Valor Florestal in an area where P. taeda
is commonly grown as an exotic species. Whole plot treatments were
two levels of silviculture, operational to match current operational
practices and intensive, which was designed to achieve near maximum
growth for the existing soil and climate. For this analysis, we excluded
the operational silviculture treatment because competing vegetation
interfered with our ability to estimate peak pine leaf area index in this
treatment and three of the genetic entries did not have operational
silviculture plots at the BR site due to a space limitation at the site and
insucient seedlings at planting. Consequently, we treated the ex-
periment as a split-plot design. Genetic entry was the main-plot treat-
ment and initial density was the split-plot treatment. There were six
genetic entries, four clonal varieties (C1, C2, C3, C4), one open polli-
nated family (OP) and one control mass pollinated family (MP). There
were three initial densities, 618, 1235, and 1853 stems ha
1
. These
treatments yielded six main-plots (genetic entry) each with three sub-
plots (initial density) per replicate.
All plots had a treated area with a smaller measurement plot cen-
tered in it. The BR site and three replicates at the VA site had 81 trees (9
T.J. Albaugh et al.
Forest Ecology and Management 425 (2018) 35–44
36

rows × 9 planting spots) in each treated plot. The NC site and one re-
plicate at the VA site had 63 trees (7 rows × 9 planting spots) in the
treated plots. The smaller treated plots were used because of space
limitations. Each measurement plot had 25 trees (5 × 5). Plot size
varied with initial density. Distance between rows (3.66 m) was the
same at all sites and treatments. Distance between trees on the row
varied with 4.42, 2.21, and 1.47 m between trees on the row for the
618, 1235, and 1853 stems ha
1
initial density treatments, respec-
tively. Plots with dierent initial density or genotypes were adjacent to
each other.
The NC and BR sites were cutover P. taeda stands and the VA site
was a cutover mixed stand of P. taeda, P. strobus L. and P. virginiana.
Soils were well drained Fine, kaolinitic, mesic Typic Kanhapludults at
the VA site, somewhat poorly drained Fine-loamy silicieous, semiactive,
thermic Typic Paleaqualts at the NC site and well drained Inceptisols
and Hapludults at the BR site. The VA and NC sites were planted in
2009 and the BR site was planted in 2011. The genetic entries were the
same for all three sites. Containerized seedlings were used for all ge-
netic entries in BR and for the clonal material at VT and NC. The MP
and OP genetic entries at VT and NC were bare-root. Mechanical and
chemical vegetation control was applied as needed to keep the trees
free from competing vegetation at all sites. Fertilizer was applied as
needed based on foliar nutrient concentration and leaf area develop-
ment with the goal to maintain the trees free from nutrient limitations.
Meteorological data (air temperature, relative humidity, precipita-
tion and photosynthetically active radiation (PAR)) were from on-site
stations at the VA and NC sites and from an INMET (2017) station (Rio
Negrinho Station A862) 10.5 km away from the BR site. When on-site
data were not available, the nearest meteorological station available
from CRONOS (2015) was used to ll in data for the VA and NC sites.
When the data from the Rio Negrinho site were not available, data from
the nearest INMET station with available data was used for the BR site.
When above canopy irradiance was not available we used SolarCalc
(Spokas and Forcella 2006) to estimate it. Vapor pressure decit was
calculated as:
=−
∗+
V
PD (1 (RH/100)) ((610.7 10 )/1000
)
(7.5 T/237.3 T)
where VPD was vapor pressure decit in kPa, RH was relative humidity
in percent, and T was air temperature in °C.
Diameter at breast height (1.3 m) and height were measured on all
live trees annually. Individual tree volume was calculated from dia-
meter at breast height and height using an equation from Tasissa et al.
(1997). Individual tree volume and basal area were summed by plot
and scaled to a hectare basis. Incremental data was estimated as the
most recent measurement minus the measurement from the previous
year. The last measurement at the BR site was taken at 5.4 years; we
scaled the diameter and height measurements for each tree from 4 years
to 5.4 years by 0.714 (1 year divided by 1.4 years) to estimate 5 year
data and used these data to estimate basal area and volume. Leaf area
index was measured using a LICOR LAI 2200 Plant Canopy Analyzer
with a 10° view cap. Peak leaf area index measurements were collected
in August for the VA and NC sites and in January for the BR site. O
peak measurements were collected in January for the VA and NC sites
and in July for the BR site. Post processing of the LICOR data included
dropping the fth ring for measurements in the 1236 and 1854 trees
ha
1
plots because this ring sampled outside the plot area for these
treatments.
2.2. Statistical analyses
To examine our rst hypothesis, we used a mixed model approach
(PROC MIXED (SAS-Institute 2002)) to test for treatment eects for all
sites after ve years for diameter, diameter increment, height, height
increment, basal area, basal area increment, volume, volume incre-
ment, and stand density. This approach was used to examine treatment
eects on peak leaf area index and o peak leaf area index for the fth
year at the BR site and for the eighth year at the VA and NC sites. Leaf
area index was not measured in the fth year at the VA and NC sites.
Site, density, genetic entry and their interactions were xed eects.
Random e ects were block and genetic entry by block (Schabenberger,
2013). Site was considered a xed eect because we selected sites in
specic areas (inside and outside the native range of P. taeda)(Littell
et al., 2006; Piepho et al., 2003). We considered blocks as replicates,
there were a total of 10 blocks (4, 3 and 3 from the VA, NC and BR sites,
respectively). We sliced by site with the other xed eects to determine
signicant interactions with site. We used the Tukey-Kramer adjust-
ment to determine means separation.
To examine our second hypothesis, we developed a regression
equation for the volume growth and intercepted light (LUE) relation-
ship using a mixed eects model. The full model was:
=
V
I I S D G I*S I*D I*G S*D S*G D*G I*S*D I*S*G I*D*G S*D*G
I*S*D*G
where VI was volume growth (m
3
ha
1
yr
1
) for the eighth growing
season at the VA and NC sites and the fth growing season at the BR
site, I was intercepted light (absorbed PAR (MJ m
2
yr
1
)) corre-
sponding to the volume increment data, S, D and G were class variables
for site, density and genetic entry, respectively. We estimated absorbed
PAR as
=−
II[1exp]
ABS O
( kL)
where I
O
was above-canopy irradiance, k was the extinction coe cient
(0.5, (Sampson and Allen, 1995)), and L was peak leaf area index
(Landsberg, 1986). Above canopy irradiance was the annual sum of all
the hourly PAR data from the meteorological stations mentioned above.
The year corresponding to volume growth for the VA and NC sites was
the calendar year (January 1 to December 31), for the BR site it was
July 1 to June 30. Block and block by genetic entry were random ef-
fects. Non-signicant terms were dropped from the model until all
terms in the model were signicant.
To examine our third hypothesis, we calculated cumulative volume
for each plot for each year at the three sites. Plot volume for each year
was averaged across site because our meteorological data were at the
site scale. Our meteorological data were on an hourly basis, conse-
quently we estimated a degree hour metric for our heat sum. We esti-
mated the hourly heat sum two ways. First, the heat sum was the cu-
mulative degree hours greater than 5 °C where ambient temperature
was between 5 and 38 °C (Ellsworth, 2000; Tang et al., 1999) and
photosynthetically active radiation was greater than 0 (daytime). If the
preceding nighttime temperature was less than 0 °C, all hours the next
day were assigned a 0 value for the heat sum (Teskey et al., 1987). For a
given hour, if the ambient temperature was 5 °C, it was during the day
and the previous nighttime temperatures were above zero then the heat
sum for that hour was 55 or 0. If under the same conditions, the
ambient temperature was 30 °C then the heat sum for that hour was 30-
5 or 25. The second method to estimate the heat sum was the same as
the rst with an additional criteria where hours where the VPD ex-
ceeded 1.5 kPa were assigned a 0 value for the heat sum (Tang et al.,
1999). For each site, all the hourly heat sums for the year were summed
for the cumulative degree hour statistic. We developed a regression
equation for the cumulative volume growth and cumulative degree
hour relationship to test for site eects. The full model was:
=∗
C
VDH S DHS
where CV was cumulative volume in m
3
ha
1
for each site at year end
as an average of all individual plot estimates of volume, DH was the
cumulative degree hour statistic and S was a class variable indicating
each site. Non-signicant terms were dropped from the model until all
terms in the model were signicant. Residuals indicated a log log
transformation was appropriate to eliminate bias and hetero-
scedasticity. The Baskerville (1972), correction was applied when
converting back to real scale.
T.J. Albaugh et al.
Forest Ecology and Management 425 (2018) 35–44
37

All statistical tests were evaluated with alpha equal to 0.05.
Residuals were examined for bias for all statistical tests; none was found
except as previously noted.
3. Results
Average annual air temperature was 13.5, 16.5, and 16.8 °C for the
VA, NC and BR sites, respectively (Table 1). Average annual pre-
cipitation was 1218, 1144, and 1580 mm yr
1
for the VA, NC and BR
sites, respectively. Average annual photosynthetically active radiation
for 20112016 (the years when all three sites were operational) was
2231, 2358, and 2400 MJ m
2
yr
1
for the VA, NC and BR sites, re-
spectively. During the year, temperatures were out of phase with high
temperatures at the VA and NC sites in July corresponding to low
temperatures in the same month at the BR site (Fig. 2ac). Annual
temperature uctuations from minimum mean monthly temperature to
maximum mean monthly temperature were 3 to 29 °C, 1 to 35 °C,
and 8 to 27 °C for the VA, NC and BR sites, respectively. Average daily
VPD ranged from 0.25 to 0.75, 0.22 to 1.0, and 0.18 to 0.46 kPa at the
VA, NC and BR sites, respectively (Fig. 2d). Average monthly photo-
synthetically active radiation ranged from 83 to 277, 85 to 302, and
116 to 278 MJ m
2
mo
1
at the VA, NC and BR sites, respectively
(Fig. 2e). Similar to temperature, VPD and photosynthetically active
radiation were out of phase with the sites in North America having high
values when the site in South America had low values and vice versa.
During the year, precipitation ranged from 60 to 180 mm month
1
across all three sites (Fig. 2f).
Site eects were signicant for all growth metrics (diameter, dia-
meter increment, height, height increment, basal area, basal area in-
crement, volume, volume increment, stand density, peak and o-peak
leaf area index) (Table 2). The BR site had greater diameter, height,
basal area, basal area increment, volume, volume increment, stand
density, peak and o-peak leaf area than the VA and NC sites
(Table 3a). Diameter increment at the BR site was smaller than at the
NC site and height increment at the BR site was less than that at the VA
and NC sites. Site average density (an indicator of survival) was 91, 87,
99% at the VA, NC and BR sites, respectively. Most mortality at all sites
appeared in the rst year. No mortality had occurred at the BR site after
the rst year however, additional mortality was evident at the NC site
in the 1235 and 1854 trees ha
1
treatments. Peak and o-peak leaf area
indices were similar at the VA and NC sites. At the BR site, peak and o-
peak leaf area indices were 72 and 119% greater than the average of the
corresponding values at the VA and NC sites, respectively.
Density signicantly inuenced all growth metrics (Table 2). Den-
sity main eects generally followed similar patterns at all sites where
tree scale metrics (diameter, diameter increment, height and height
increment) either decreased with increasing density or stayed the same
(Table 3a). At the same time, stand scale metrics (basal area, basal area
increment, volume, and volume increment) increased with increasing
density. The general patterns of response were similar across sites
however, the magnitude of the dierences between density treatments
at the dierent sites was dierent and resulted in a signicant site by
density interaction for all growth metrics except height. For example,
basal area increment more than doubled (more than 100% increase)
going from the low to high density treatment at the VA and NC site
whereas at the BR site the corresponding increase was about 56%.
Density was generally less for the mass-control pollinated and open
pollinated genetic entries than the other genetic entries at the VA and
NC sites, respectively. Early survival was less for these genetic entries
likely because they were planted as bare root seedlings whereas the
other genetic entries at the VT and NC sites were containerized seed-
lings. All genetic entries at the BR sites were planted as containerized
seedlings.
Genetic entry signicantly inuenced all growth metrics except for
height and o-peak leaf area index (Table 2). For a given site, detect-
able dierences were observed among genetic entries for most growth
metrics (Table 3b). For example, at the VA site, a dierence among the
genetic entries was observed for all growth metrics except diameter
increment, peak and o-peak leaf area index. A genetic entry by site
interaction was found for all growth metrics except peak leaf area index
such that a dierent genetic entry typically grew the best at each site.
Clone 2 performed the best at the NC site having the greatest growth or
tied for greatest growth for diameter, height, height increment, basal
area, basal area increment, volume, volume increment and density. At
Table 1
Summary of environmental data including average annual air temperature, average daily maximum and minimum air temperature, annual precipitation and annul
incident photosynthetically active radiation for three sites (VA = Virginia, NC = North Carolina, BR = Brazil) where the same genetic material of Pinus taeda was
planted at all sites.
Air temperature Precipitation Photosynthetically active radiation
Average annual Average daily maximum minimum
Site Year °C °C °C mm yr
1
MJ m
2
yr
1
VA 2009 13.1 19.0 7.6 1280 2236
VA 2010 13.4 19.9 7.6 1107 2324
VA 2011 14.0 20.2 8.4 1340 2251
VA 2012 14.2 20.3 8.6 1266 2217
VA 2013 13.1 18.8 8.0 1305 2243
VA 2014 12.8 18.9 7.1 1104 2315
VA 2015 13.9 19.9 8.4 1421 2179
VA 2016 13.7 19.9 8.1 919 2181
NC 2009 16.8 24.3 10.4 1218 2442
NC 2010 16.5 24.8 9.7 1169 2702
NC 2011 17.0 25.1 10.3 945 2701
NC 2012 17.2 25.4 10.6 1051 2808
NC 2013 15.9 24.5 8.7 1175 2422
NC 2014 15.3 24.8 7.4 996 2120
NC 2015 16.7 25.7 9.4 1204 2063
NC 2016 16.5 25.9 9.3 1397 2034
BR 2011 16.0 21.8 12.3 1692 2431
BR 2012 17.0 23.4 13.0 1600 2482
BR 2013 16.3 22.4 12.2 1706 2398
BR 2014 17.3 23.3 13.4 1615 2445
BR 2015 17.5 23.3 13.8 1488 2244
BR 2016 16.6 22.8 12.5 1376 2401
T.J. Albaugh et al.
Forest Ecology and Management 425 (2018) 35–44
38

the BR site, the open pollinated family performed the best and at the VA
site, clones 2 and 4 typically performed the best.
Absorbed photosynthetically active radiation, genetic entry, density
and absorbed photosynthetically active radiation by genetic entry were
signicant terms in the LUE analysis (Table 4). Site was not a signicant
term in this analysis. For the open pollinated genetic entry and an ab-
sorbed photosynthetically active radiation of 1600 MJ m
2
yr
1
, pre-
dicted volume growth was 22.9, 32.9, 42.2 m
3
ha
1
yr
1
for the den-
sities of 618, 1236, 1854 trees ha
, respectively (Fig. 2a). For a density
of 1854 trees ha
1
and an absorbed photosynthetically active radiation
of 1600 MJ m
2
yr
1
, predicted volume growth was 47.6, 43.9, 45.5,
48.1, 45.2, and 42.2 m
3
ha
1
yr
1
for C1, C2, C3, C4, MP and OP ge-
netic entries, respectively (Fig. 2b). The overall slope of the equation
was positive (0.0222 Table 4). However, the interaction term of ab-
sorbed photosynthetically active radiation by genetic entry had nega-
tive parameter estimates which resulted in a near zero slope (no/little
change in volume growth with increasing absorbed photosynthetically
active radiation) for C3 and a negative slope (decreasing volume
growth with increasing absorbed photosynthetically active radiation)
for C4.
With no adjustment for VPD, the NC site accumulates about twice as
many degree hours in the last year measured than the BR site with the
VA site intermediate between the NC and BR sites (Fig. 3a). Setting
hours where VPD was greater than 1.5 kPa to 0 for the cumulative
degree hour calculation reduces the cumulative degree hours for the NC
and VA sites much closer to the BR site values (Fig. 3b). Cumulative
degree hours and site were signicant independent variables explaining
cumulative volume. For a given level of cumulative degree hours the
sites rank BR > VA > NC for cumulative volume. For example, the
last measurement at the BR site was from the fth year of growth when
cumulative volume was 102 m
3
ha
1
and cumulative degree hours to-
taled 270,000. After the seventh year of growth at the VA and NC sites,
cumulative degree hours were 266,000 and 272,000, respectively,
however, cumulative volume was 91 and 73 m
3
ha
1
, respectively.
Fig. 1. Mean monthly air temperature (a), maximum air temperature (b), minimum air temperature (c), mean daily vapor pressure decit (VPD) (d), mean monthly
photosynthetically active radiation (PAR) (e), and mean monthly precipitation (f) for the sites in Virginia (VA), North Carolina (NC) and Brazil (BR) where the same
Pinus taeda genetic entries were planted at three initial densities.
T.J. Albaugh et al.
Forest Ecology and Management 425 (2018) 35–44
39

Figures (8)
Citations
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Journal ArticleDOI
Abstract: We estimated timber investment returns for 22 countries and 54 species/management regimes in 2017, for a range of global timber plantation species and countries at the stand level, using capital budgeting criteria, without land costs, at a real discount rate of 8%. Returns were estimated for the principal plantation countries in the Americas—Brazil, Argentina, Uruguay, Chile, Colombia, Venezuela, Paraguay, Mexico, and the United States—as well as New Zealand, Australia, South Africa, China, Vietnam, Laos, Spain, Finland, Poland, Scotland, and France. South American plantation growth rates and their concomitant returns were generally greater, at more than 12% Internal Rates of Return (IRRs), as were those in China, Vietnam, and Laos. These IRRs were followed by those for plantations in southern hemisphere countries of Australia and New Zealand and in Mexico, with IRRs around 8%. Temperate forest plantations in the U.S. and Europe returned less, from 4% to 8%, but those countries have less financial risk, better timber markets, and more infrastructure. Returns to most planted species in all countries except Asia have decreased from 2005 to 2017. If land costs were included in calculating the overall timberland investment returns, the IRRs would decrease from 3 percentage points less for loblolly pine in the U.S. South to 8 percentage points less for eucalypts in Brazil.

16 citations


Cites background from "A common garden experiment examinin..."

  • ...In contrast, Sedjo (1983) reported that IRRs in Brazil and Chile in South America were quite high, ranging from 16% to 28%....

    [...]

  • ...South America and Asia also increased their area of planted forests (Nepal et al., 2019)....

    [...]

  • ...Sedjo (1983) led in performing this line of research, and generally found relatively high IRRs for South America and Asia; lesser returns for Oceania and the U.S. South; and the smallest returns for Europe....

    [...]

  • ...South American industrial plantations are generally comprised of exotic species of pine (e.g., P. taeda, P. radiata) from North America and eucalypt (e.g., E. grandis, E. urophylla, E. globulus, E. dunii, or hybrids) from Australia....

    [...]

  • ...On the other hand, in much of the Southern Cone of South America, the sunk (and cheap) land costs are one major reasons that vertically integrated pulp and paper companies have not yet sold their timberland asset....

    [...]


Journal ArticleDOI
TL;DR: Results indicate that Sentinel-2’s improved spatial resolution and temporal revisit interval provide new opportunities for managers to detect within-stand variance and improve accuracy for LAI estimation over current industry standard models.
Abstract: Leaf area index (LAI) is an important biophysical indicator of forest health that is linearly related to productivity, serving as a key criterion for potential nutrient management. A single equation was produced to model surface reflectance values captured from the Sentinel-2 Multispectral Instrument (MSI) with a robust dataset of field observations of loblolly pine (Pinus taeda L.) LAI collected with a LAI-2200C plant canopy analyzer. Support vector machine (SVM)-supervised classification was used to improve the model fit by removing plots saturated with aberrant radiometric signatures that would not be captured in the association between Sentinel-2 and LAI-2200C. The resulting equation, LAI = 0.310SR − 0.098 (where SR = the simple ratio between near-infrared (NIR) and red bands), displayed good performance ( R 2 = 0.81, RMSE = 0.36) at estimating the LAI for loblolly pine within the analyzed region at a 10 m spatial resolution. Our model incorporated a high number of validation plots (n = 292) spanning from southern Virginia to northern Florida across a range of soil textures (sandy to clayey), drainage classes (well drained to very poorly drained), and site characteristics common to pine forest plantations in the southeastern United States. The training dataset included plot-level treatment metrics—silviculture intensity, genetics, and density—on which sensitivity analysis was performed to inform model fit behavior. Plot density, particularly when there were ≤618 trees per hectare, was shown to impact model performance, causing LAI estimates to be overpredicted (to a maximum of X i + 0.16). Silviculture intensity (competition control and fertilization rates) and genetics did not markedly impact the relationship between SR and LAI. Results indicate that Sentinel-2’s improved spatial resolution and temporal revisit interval provide new opportunities for managers to detect within-stand variance and improve accuracy for LAI estimation over current industry standard models.

7 citations


Cites background from "A common garden experiment examinin..."

  • ...Two of the sites—Regionwide 20 in Bladen Lakes, North Carolina (RW20-NC), and Reynold’s Homestead, Virginia (RW20-VA)—were part of an ongoing trial established in 2009 to quantify the impact of silviculture intensity, stand density, and genetics on loblolly pine productivity (Table 1) [27]....

    [...]


Journal ArticleDOI
TL;DR: Why P. taeda can grow much better in Brazil than in the southeastern United States is likely due to a combination of factors, including leaf area distribution, crown architecture, and other factors that have been identified as influencing the site effect.
Abstract: We examined crown architecture and within crown leaf area distribution effects on Pinus taeda L. growth in North Carolina (NC), Virginia (VA), and Brazil (BR) to better understand why P. taeda can grow much better in Brazil than in the southeastern United States. The NC, VA, and BR sites were planted in 2009, 2009, and 2011, respectively. At all sites, we planted the same two genetic entries at 618, 1236, and 1854 trees ha−1. In 2013, when trees were still open grown, the VA and NC sites had greater branch diameter (24%), branch number (14%), live crown length (44%), foliage mass (82%), and branch mass (91%), than the BR site. However, in 2017, after crown closure and when there was no significant difference in tree size, site did not significantly affect these crown variables. In 2013, site significantly affected absolute leaf area distribution, likely due to differences in live crown length and leaf area, such that there was more foliage at a given level in the crown at the VA and NC sites than at the BR site. In 2017, site was still a significant factor explaining leaf area distribution, although at this point, with crown closure and similar sized trees, there was more foliage at the BR site at a given level in the crown compared to the VA and NC sites. In 2013 and 2017, when including site, genetic entry, stand density, and leaf area distribution parameters as independent variables, site significantly affected individual tree growth efficiency, indicating that something other than leaf area distribution was influencing the site effect. Better BR P. taeda growth is likely due to a combination of factors, including leaf area distribution, crown architecture, and other factors that have been identified as influencing the site effect (heat sum), indicating that future work should include a modeling analysis to examine all known contributing factors.

5 citations


Journal ArticleDOI
Abstract: Carbon dioxide emissions to the atmosphere from human activity continue to increase, and accordingly, strategies of biological carbon (C) sequestration in terrestrial ecosystems have been proposed. Forestation projects have garnered wide public support, and research has focused principally on how soil C storage is affected. Nevertheless, our mechanistic understanding of how forestation, particularly with exotic woody species, affects ecosystem processes is not well understood. We took advantage of a land-use change in Patagonia, Argentina, that involved the simultaneous planting of a single conifer species (Pinus ponderosa) along a broad precipitation gradient [250–2200 mm mean annual precipitation (MAP)], replacing natural ecosystems from semi-arid steppe to broadleaf forest. Comparing C fluxes and stocks in five paired natural and planted forest sites during three consecutive years demonstrated that aboveground net primary production (ANPP) was consistently greater in forested areas along the gradient, while litter decomposition markedly decreased. Dramatic increases in leaf litter detritus, coupled with increased aboveground woody biomass, contributed to identical levels of C accumulation in pine plantations from 250 mm to 1350 mm MAP, without significantly detectable differences in surface soil C. The replacement of intact forest in the most humid site resulted in large decreases in vegetation C pools. The implications for ecosystem C cycling suggest that inhibition of C turnover, along with the aboveground woody growth, are key variables contributing to the observed patterns of C accumulation from exotic pine forestation along this precipitation gradient. Given the transient nature of these C stocks, vulnerable to loss as CO2 due to climatic or anthropogenic disturbances, these changes may not contribute to long-term C sequestration in these ecosystems. The conversion of natural ecosystems as a management tool for C mitigation should include a consideration of the realized sequestration potential but also the unintended consequences for changes in both C inputs and C turnover that determine the ecosystem C balance, as well as potential effects on biodiversity and long-term ecosystem functioning.

4 citations


Journal ArticleDOI
Abstract: Pinus taeda plantations are an important economic activity in southern Brazil, where edaphoclimatic conditions are optimal. Understanding how meteorological conditions influence tree growth is important in such a favorable environment for reaching high growth rates and for predicting tree growth responses to climate change. The study was designed to evaluate the influence of meteorological variables on 30 years of radial growth of P. taeda trees subjected to different crown thinning intensities in southern Brazil. In total, 9280 measurements of ring width and age were evaluated. Residual chronologies were obtained according to standard dendrochronology techniques. Correlation was calculated between chronologies and meteorological variables, and thus the direction and magnitude of the relationship between meteorology and growth was addressed. Results indicated that, accounting for the whole year, meteorological conditions show no particular influence on the radial growth of Pinus taeda trees in the studied region. The exception was the vapor pressure deficit, with a significant and negative correlation with the radial growth of trees at all thinning intensities. When considering seasons, several consistent correlations were detected. Rainfall during winter, previously or at the end of the growing season, was positively correlated with the radial growth of trees at all thinning intensities. A consistent negative correlation between minimum and maximum temperature during winter and the radial growth of trees shows that P. taeda in southern Brazil, regardless of thinning intensity, benefit from colder winters in general and, particularly, from colder days during winter. Although temperature increases in the highlands of southern Brazil, as a result of global warming, may not render the cultivation of P. taeda unfeasible, they may restrict or shift the region of optimum growth as well as require changes in the genetic material. Results also suggest that high-intensity thinning may increase the influence of temperature on growth pattern of the stands.

3 citations


References
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Journal ArticleDOI
Abstract: The efficiency of crop production is defined in thermodynamic terms as the ratio of energy output (carbohydrate) to energy input (solar radiation). Temperature and water supply are the main climatic constraints on efficiency. Over most of Britain, the radiation and thermal climates are uniform and rainfall is the main discriminant of yield between regions. Total production of dry matter by barley, potatoes, sugar beet, and apples is strongly correlated with intercepted radiation and these crops form carbohydrate at about 1.4 g per MJ solar energy, equivalent to 2.4% efficiency. Crop growth in Britain may therefore be analysed in terms of ( a ) the amount of light intercepted during the growing season and ( b ) the efficiency with which intercepted light is used. The amount intercepted depends on the seasonal distribution of leaf area which, in turn, depends on temperature and soil water supply. These variables are discussed in terms of the rate and duration of development phases. A factorial analysis of efficiency shows that the major arable crops in Britain intercept only about 40 % of annual solar radiation and their efficiency for supplying energy through economic yield is only about 0.3%. Some of the factors responsible for this figure are well understood and some are immutable. More work is needed to identify the factors responsible for the large differences between average commercial and record yields.

3,117 citations


"A common garden experiment examinin..." refers background in this paper

  • ...T changes in climate and location influence growth (Albaugh et al., 2016; Monteith 1977; Waring et al., 2016)....

    [...]


Book
01 Jan 2006

2,864 citations


Journal ArticleDOI
Abstract: Heat units, expressed in growing degree-days (GDD), are frequently used to describe the timing of biological processes. The basic equation used is GDD = [(TMAX + TMIN)2]−TBASE, where TMAX and TMIN are daily maximum and minimum air temperature, respectively, and TBASE is the base temperature. Two methods of interpreting this equation for calculating GDD are: (1) if the daily mean temperature is less than the base, it is set equal to the base temperature, or (2) if TMAX or TMIN < TBASE they are reset equal to TBASE. The objective of this paper is to show the differences which can result from using these two methods to estimate GDD, and make researchers and practitioners aware of the need to report clearly which method was used in the calculations. Although percent difference between methods of calculation are dependent on TMAX and TMIN data used to compute GDD, our comparisons have produced differences up to 83% when using a 0°C base for wheat (Triticum aestivum L.). Greater differences were found for corn (Zea mays L.) when using a base temperature of 10°C. Differences between the methods occur if only TMIN is less than TBASE, and then Method 1 accumulates fewer GDD than Method 2. When incorporating an upper threshold, as commonly done with corn, there was a greater difference between the two methods. Not recognizing the discrepancy between methods can result in confusion and add error in quantifying relationships between heat unit accumulation and timing of events in crop development and growth, particularly in crop simulation models. This paper demonstrates the need for authors to clearly communicate the method of calculating GDD so others can correctly interpret and apply reported results.

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Abstract: The basic assumptions of regression analysis are recalled with special reference to the use of a logarithmic transformation. The limitations imposed on inference-making by failure to comply with th...

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"A common garden experiment examinin..." refers methods in this paper

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Journal ArticleDOI
TL;DR: It was found that elevated temperatures enhanced growth in deciduous species more than in evergreen trees, and Tropical species were indeed more susceptible to warming-induced growth declines than temperate or boreal trees in both analyses.
Abstract: Summary The response of tree growth to a change in temperature may differ in predictable ways. Trees with conservative growth strategies may have little ability to respond to a changing climate. In addition, high latitude and altitude tree growth may be temperature-limited and thus benefi tf rom some degree of warming, as opposed to warm-adapted species. Using data from 63 studies, we examined whether trees from different functional groups and thermal niches differed in their growth response to a change in growth temperature. We also investigated whether responses predicted for a change in growth temperature (both reduced and elevated) were similar for increased temperatures by repeating the analysis on the subset of raised temperature data to confirm the validity of our results for use in a climate-warming scenario. Using both the temperature-change response and the warming response, we found that elevated temperatures enhanced growth (measured as shoot height, stem diameter and biomass) in deciduous species more than in evergreen trees. Tropical species were indeed more susceptible to warminginduced growth declines than temperate or boreal trees in both analyses. More carbon may be available to allocate to growth at high temperatures because respiration acclimated more strongly than photosynthesis, increasing carbon assimilation but moderating carbon losses. Trees that developed at elevated temperatures did not simply accelerate growth but followed different developmental trajectories than unwarmed trees, allocating more biomass to leaves and less to roots and growing taller for a given stem diameter. While there were insufficient data to analyze trends for particular species, we generated equations to describe general trends in tree growth to temperature changes and to warming for use at large spatial scales or where data are lacking. We discuss the implications of these results in the context of a changing climate and highlight the areas of greatest uncertainty regarding temperature and tree growth where future research is needed.

620 citations


Frequently Asked Questions (1)
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.