Crown Responses to Fertilization in Juvenile Western Redcedar and Western Hemlock R.W. Negrave Research Silviculturist BC Forest Service
Crown Response to Fertilization: Focus on Cw and Hw Part I: What we know about crown response to fertilization Part II: Response of juvenile Cw and Hw stands to fertilization during establishment: Stand level foliage mass Tree level crown structure of Cw
Part I: What we know
Crowns and Resources: Context Forest growth a function of: Resource supply (soil and solar resources) Resource capture (roots, crowns) Resource use efficiency (foliage)
Crown Response to Fertilization Crown response a function of: Foliage amount Foliar efficiency Foliage deployment
Foliage Response to Fertilization Fertilization may change foliage: Amount Proportion Efficiency Deployment Response varies with: species, structure, site, time
Part II: Crown Response in Juvenile Cw and Hw
Study Outline Salal Cedar Hemlock Integrated Research Program (SCHIRP) on northern Vancouver Island Factorial experiment: Species ( (Cw, Hw) Fertilization ( (F0, F1) Density ( (500, 1500 and 2500 sph) Experiment was paired on two sites
Study Questions Would fertilization and high establishment density improve stand growth? What are site differences between Cedar Hemlock ( (CH)) and Hemlock Amabilis Fir (HA)) stands? How do treatments affect structure and its relation to growth?
Study Design: Main Trial Completely randomized block design with four replications Permanent sample plots with 64 trees in each treatment level replicate Continued re-measurement since establishment in 1988: 15-year measurements in 2002 (10 yrs since last fertilization)
Sampling: Tree-Level Study Individual trees sampled from density levels across three nutrient regimes: CH-F0 < CH-F1 < HA-F1 Sampling focussed on Cw: 84 Cw and 41Hw Covariate analysis to detect effects other than size (allocation/allometry)
Design: Tree-Level Study Mass prediction equations developed: lnyij = ln β0i + ln β1ixj + ln εij Equations used to calculate stand level total and component masses (r 2 values ranged from 0.81 to 0.98) Analysis of variance to examine tree-level effects in Cw
Stand Foliage Mass Response: CH Sites Species x fertilization x density interaction Fertilization increased stand foliage mass but varied with species and density Hw responded more than Cw
6 Foliage Mass on CH g 5 Cw-F0 fg Hw-F0 S tand Foliage M ass (t/h a) 4 3 2 1 de bc cd b efg ef c Cw-F1 Hw-F1 de ef a 0 500 1500 2500 Stand Density (Stems/ha)
Stand Foliage Mass Response: HA Sites Fertilization increased foliage mass about 153% Mass of Hw foliage was about 2X that of Cw
Foliage Mass and Growth Average annual increment (1997 2002) was closely associated with stand foliage mass: b 1 r 2 CH-Cw: Cw: 0.562 0.967 CH-Hw: Hw: 0.577 0.984 HA-Cw: 0.646 0.983 HA-Hw: Hw: 0.625 0.988
Foliage - Growth Relationships 4.5 8 Biom ass Incrrm ent (t/ha/yr) 4.0 3.5 3.0 2.5 2.0 1.5 1.0 Cw on CH r r = 0.967 No Fert. Fertilized Biom ass Increm ent (t/ha/yr) 7 6 5 4 3 2 Cw on HA r 2 = 0.983 No Fert. 0.5 1 Fertilized 0.0 0 1 2 3 4 5 6 7 8 Foliage Mass (t/ha) 0 0 2 4 6 8 10 12 Foliage Mass (t/ha) 7 16 Biom ass Increm ent (t/ha/yr) 6 5 4 3 2 Hw on CH r 2 = 0.984 No Fert. Fertilized Biom ass Increm ent (t/ha/yr) 14 12 10 8 6 4 Hw on HA r 2 = 0.988 Non Fert Fert 1 2 0 0 2 4 6 8 10 12 Foliage Mass (t/ha) 0 0 5 10 15 20 25 Foliage Mass (t/ha)
Individual Cw Foliage Mass Foliage mass increased with nutrient regime: Foliage Mass (kg) CH-F0: 2.15a CH-F1: 3.73b HA-F1: 5.96c
Individual Cw Foliage Mass Foliage mass decreased with increasing Density: Foliage Mass (kg) 500 sph: 5.30c 1500 sph: 3.83b 2500 sph: 2.71a
Foliage Height Profile Foliage mass increased with nutrient regime in the mid-crown section
Foliage Mass: Height x Nutrients 3.5 3.0 2.5 g CH-F0 CH-F1 HA-F1 Foliage Mass (kg) 2.0 1.5 bcde cdef ef ef 1.0 abcde abcd 0.5 abc abc 0.0 Lower Mid Top Tree Height Section
Branch Length Branch increased with nutrient regime
Branch Length: Height x Nutrient 250 g Branch Length (cm) 200 150 100 d f c d ad e a CH-F0 CH-F1 HA-F1 ab bc 50 0 Lower Mid Top Tree Height Section
Branch Diameter Branch diameter: Was reduced by density in the upper crown at the highest nutrient regime Increased with nutrient regime but less so at the top of the crown
Br. Diameter: Density x Nutrient 2.0 1.8 500 sph 1500 sph cd d d 1.6 2500 sph bc c Branch Diameter (cm) 1.4 1.2 1.0 0.8 0.6 ab a a ab 0.4 0.2 0.0 CH-F0 CH-F1 HA-F1 Nutrient Regime
Br. Diameter: Height x Nutrient 2.5 2.0 d e de CH-F0 CH-F1 Branch Diameter (cm) 1.5 1.0 c b c a HA-F1 ab b 0.5 0.0 Lower Mid Top Tree Height Section
Conclusion Fertilization increased stand growth and foliage mass 10 seasons after last application Growth was closely associated with foliage mass Crown structure in Cw influenced by density at higher nutrient regimes