Genotype by silviculture interactions on growth, stand uniformity and leaf-level gas exchange of loblolly pine varieties Marco Yanez, Thomas Fox, John Seiler

Nutrient Availability, Fertilizer Uptake and Efficiency Decision Support Tools and Models Remote Sensing and Leaf Area Index Weed Control and Fertilization Fertilization Response Eucalyptus Silviculture Genetics X Silviculture Interactions Response Modeling, Growth and Yield Models Ecophysiology, Process Models, Potential Productivity Initial Spacing and Thinning Water and Environmental Impacts Forest Productivity Cooperative Research Priorities:

Rationale Forest productivity Extensive Intensity Precision Half-sib families Full-sib familiesVarieties Silvicultural practices Tree improvement

Rationale Forest productivity Extensive Intensity Precision Half-sib families Full-sib familiesVarieties Silvicultural practices Tree improvement

Rationale Forest productivity Extensive Intensity Precision Half-sib families Full-sib familiesVarieties Silvicultural practices Tree improvement

Part 1: Rationale – Stand uniformity Variation in Clonal Performance Due to Silviculture Low IntensityHigh Intensity Photos by Tom Fox

Operational, Piedmont VA Intensive, Piedmont VA Part 1: Rationale – Stand uniformity

Skid trail Bedding quality Part 1: Rationale – Stand uniformity

Study sites The site at Virginia Piedmont North Carolina Coastal Plain

Experimental design Stand productivity StockingSilvicultural practices Genetic entries = Varieties4 Varieties 1 OP family1 OP family 1 CMP family1 CMP family VA Reynolds NC Bladen 250 tpa 500 tpa 750 tpa Sites + OperationalIntensive Whole plot Split plot Split-split plot

Methods Virginia Piedmont Narrow-Crown Clone C1 and C3 Broad-Crown Clone C2 and C4

To assess the effect of silviculture on stand uniformity on loblolly pine varieties, and To assess the stability of those responses between different sites Part 1. Stand uniformity Objective

Growth Site x Silvi. Site x Gen

Part 1: Uniformity – DBH – Age 4 No effect of silviculture (p=0.054) Site by genotype interaction (p<0.01)

Part 1: Uniformity – Height – Age 4 No effect of silviculture (p=0.51) Site by genotype interaction (p<0.01)

Part 1: Stand uniformity vs stand volume

Part 2: Rationale- leaf physiology Variation in Leaf Level Physiology Among Varieties and Due to Silviculture Low IntensityHigh Intensity Photos by Tom Fox CO 2 carbohydrates H2OH2OH2OH2O CO 2 carbohydrates H2OH2OH2OH2O

To assess the effect of silviculture on leaf-level physiology on loblolly pine varieties, and To assess the stability of those responses between different sites Part 2. Leaf-level physiology Objective

Part 2: Measurements Tree height 3 trees/plot Total 108 trees/site Sample tree 1 Sample tree 2 Sample tree 3

Part 2: Measurements 2011 (3 rd growing season) 2012 (4th growing season) Photosynthesis Carbon isotope discrimination

3 fascicles Part 2: Measurements

1600 micromol/m2/s Asat Part 2: Measurements

Results photosynthesis

Part 2: Photosynthesis Narrow Crown Broad Crown Families

Part 2: Carbon isotope discrimination NCVA Narrow Crown Broad Crown Families

Correlation between physiological parameters and accumulated volume at age 4

Narrow-Crown Clone C1 and C3 Broad-Crown Clone C2 and C4 Leaf physiology Leaf area Canopy conductance N demand Intraspecific competition Stand dynamic Etc. Part 3: Rationale – Within crown variation

Low Silviculture High Silviculture Is nitrogen deficiency expressed first in the lower crown? Asat N Part 3: Rationale – Within crown variation

Narrow-Crown Clone C1 and C3 Broad-Crown Clone C2 and C4 Asat N Part 3: Rationale – Within crown variation

To assess the intra-crown variability on leaf- level physiology on loblolly pine varieties, and Part 3. Leaf-level physiology ‘within crown variation’ Objective

Part 3: Within crown variation in Asat Upper Crown Lower Crown Tree height Sampled tree Asat N (%)

Nitrogen: Site by crown position interaction

Silv by crown position Interaction on Asat and N

Gen by crown position Interaction on Asat and N

Conclusions Genetic by silvicultural effects on growth (magnitude of the response was site specific). Stand uniformity is not a trait intrinsic to varietal stand, but higher uniformity increased stand productivity. Some genotypes differed in both growth and gas-exchange parameters. Gas exchange parameters did not explain the differences in growth.

Implications Differences in canopy architecture affect the rate of canopy closure. Differences in physiology among the genotypes may interact with stand development to affect forest productivity Total canopy PS Impact of competition on crown development after crown closure

Differences in leaf area will affect total stand PS and carbon capture even if leaf level PS is the same Narrow-Crown Clone C1 and C3 Broad-Crown Clone C2 and C4 Age 3

Methods: Photosynthesis, part 1

Differences in leaf area will affect total stand PS and carbon capture even if leaf level PS is the same Age 5

modelling Modelling efforts to predict future performance

Questions Marco Yanez and John Peterson setting up equipment Photosynthesis being measured at Bladen lakes, NC