1. a tree level perspective
Fertilization and irrigation effects on production and light use efficiency in a loblolly pine plantation:
a tree level perspective
José Luiz Stape – NCSU
Otávio C. Campoe - IPEF
Tim Albaugh, Lee Allen (NCSU),
Tom Fox (VT), Rafael Rubilar (UdeC), Dan Binkley (CSU)
17th Biennial Southern Silvicultural Research Conference
Shreveport LA March 5th 2013

2. Southeast Tree Research and Education Site SETRES
2 x 2
Fertilization x Irrigation
4 Blocks
0.62 acre plots
U.S. Forest Service
North Carolina State University
Duke University
Virginia Tech

3. +Nutrients+Water
+Nutrients
+Water
Control
Data from Albaugh et al 1998, 2004, 2006, 2008, and unpublished

4. SE US: SETRES site
Control
Nutrients + Water

5. +Nutrients+Water
+Nutrients
+Water
Control
Data from Albaugh et al 1998, 2004

6. SETRES: Volume Growth - Leaf Area
©H.L. Allen and T.J. Albaugh, 2007

7. And for a tree level interpretation ?
How LAI and LUE vary across tree sizes ?
Implications for Thinning,
Fertilization, Remote Sensing…
Control
Nutrients + Water

8. Does size matter? Growth = biomass production
APAR = amount of light absorbed
LUE = amount of biomass produced per amount of light absorbed
Binkley, Stape (2010)

9. Overall pattern
Larger trees within a stand tend to absorb more light and use it more efficiently in growing wood…
Greater growth of large trees typically results from a combination of
1 – Increased APAR (↑leaf area)
2 - Increased LUE
…but exactly how much for Loblolly Pine ?

10. To address that we need: A tree-level canopy light model
Overall pattern
Larger trees within a stand tend to absorb more light and use it more efficiently in growing wood…
To address that we need:
A tree-level canopy light model
- Accurated recorded data at tree-level
Greater growth of large trees typically results from a combination of
1 – Increased APAR (↑leaf area)
2 - Increased LUE
And we had that:
- MAESTRA Model
- SETRES dataset
…but exactly how much for Loblolly Pine ?

11. What is MAESTRA model Inputs
3-D process-based model for calculating absorbed radiation, transpiration and photosynthesis of individual trees
Inputs
Tree position → focal and neighbors
Canopy Structure → leaf area and seasonality, crown size and shape, leaf angles, needles optical characteristics.
Weather → mainly incoming PAR
MAESTRA estimates mean intercepted solar radiant energy (per square meter of foliage) PAR and NIR wave bands, using the radiative transfer model of Norman and Welles (1983)
For those interested, just Google it (“Maestra Model”)

13. How MAESTRA sees the trees
Control
I + F

14. RESULTS I+F Stand Level Production Control ↑ ANPP = Incoming light
↑ APAR
Suggests ↑ LUE
~3X
~2X
I+F
Control

15. Tree leaf area was linearly related with tree APAR for all treatments
Higher leaf area gives advantages in light absorption

16. Aboveground biomass (%, small to large)
Larger trees in a stand were more productive than smaller trees due to higher APAR and elevated LUE
Aboveground biomass (%, small to large)

17. non-dominant trees among treatments
Biometric variables
Increasing resource availability accentuated the differences between dominant and
non-dominant trees among treatments
Control
I + F
Small X Large trees:
2.2-fold larger DBH
59% taller
54% longer crown
3.2-fold more leaf area
Small X Large trees:
2.6-fold larger DBH
74% taller
75% longer crown
3.7-fold more leaf area

18. Aboveground biomass (%, small to large)
Larger trees in a stand were more productive than smaller trees due to higher APAR and elevated LUE
Aboveground biomass (%, small to large)

19. Irrigated + Fertilization
Production Ecology
Fertilization
increased the growth of the largest trees by 2-fold
(from 4.3 to 8.6 kg tree-1 year-1)
25% higher APAR (11 to 13.7 GJ tree-1 year-1)
75%from higher LUE (0.39 to 0.63 gMJ-1)
Irrigated + Fertilization
tripled productivity of the largest trees
(13.2 kg tree-1 year-1)
19% higher APAR (15.1 GJ tree-1 year-1)
81%from higher LUE (0.87 gMJ-1)

20. And for a tree level interpretation ?
Better initial silvicultural treatments to assure more uniform stands
Thinning from below is the way to go
Weed control after thinning
Fertilization after thinning
MAESTRA model for breeding...
Control
Nutrients + Water