Thinning Impacts on Even-aged Stands of Eucalyptus in Brazil Thinning Impacts on Even-aged Stands of Eucalyptus in Brazil June 21, 2010 Missoula, MT Western Mensurationists’ Conference

Introduction Plantation forest in Brazil: 6.6 million hectares, representing 0.8 % of the land area From 2004 to 2008 the area in eucalyptus plantation increased by 33.1%, or 1.1 million ha solid wood products is minimal

Introduction Advances in wood technology and design have allowed various uses of eucalyptus wood as a solid product

Introduction The demand for wood from large trees has been supported by illegal harvesting in native forests Consequently, there are also few studies on the impact of thinning in stands of eucalyptus in Brazil

Introduction Studies of thinning in eucalyptus are strategic for Brazil, both economically and environmentally Thinning in eucalyptus forests can help increase Brazilian participation in the global market for solid wood products and may reduce pressure on Brazilian native forests

Introduction An experiment was established to obtain a database reliable for analyzing the difference among thinning treatments and for developing growth and yield models for thinned eucalyptus stands Requirements: - Selection of the sample units was deliberate (selective sampling), so that representation of the medium and extreme site conditions is guaranteed - The sample units were sufficiently large to faithfully represent the silvicultural practices applied to the remainder of the stand

Objective To analyze the effect of thinning on growth of stand variables in eucalyptus forests

Overview of the experiment - Species: Eucalyptus grandis x Eucalyptus urophylla hybrid - Location: Northeast region of Bahia State, Brazil

Overview of the experiment - Planting date: June/July Date of installation of the permanent plots: September Company: Bahia Specialty Cellulose (BSC) ( - Initial spacing between trees: 3.0 X 3.0 m - Thinnings accomplished: two selective thinnings, in 1998 and Final harvest: at the end of 2007

Experimental Design - based on level-of-growing-stock installation standards - Located in 3 installations, comprising medium and good quality site conditions

Experimental Design - Replicated randomized complete block with repeated measures - 6 blocks (two in each installation), each one involving two repetitions; - 4 treatments, corresponding to different basal area percentages removed in each thinning : Treatment 1: 20% without pruning; Treatment 2: 35% without pruning; Treatment 3: 50% without pruning; Treatment 4: 35% with pruning up to 6.0 meters; - Each block contained 8 permanent rectangular plots, with an area of 2,600 m 2, totaling 48 plots (6 blocks x 2 repetitions x 4 treatments)

- Layout Experimental Design Block 1 Block 2 Block 1Block 2 Block 1 A B C

Experimental Design - Replicated randomized complete block with repeated measures - 6 blocks (two in each installation), each one involving two repetitions; - 4 treatments, corresponding to different basal area percentages removed in each thinning : Treatment 1: 20% without pruning; Treatment 2: 35% without pruning; Treatment 3: 50% without pruning; Treatment 4: 35% with pruning up to 6.0 meters; - Each block contained 8 permanent rectangular plots, with an area of 2,600 m 2, totaling 48 plots (6 blocks x 2 repetitions x 4 treatments) - Plots were buffered by a few rows of trees on each side

Marked boundaries of a plot

Measurement Year of measurement Age (month) Age (year) Note before 1st thinning before 1st thinning before 1st thinning; 1st stem analysis (6 trees per dbh class) after 1st thinning after 1st thinning after 1st thinning after 1st thinning after 1st thinning after 1st thinning after 1st thinning after 2nd thinning after 2nd thinning after 2nd thinning; 2nd stem analysis (6 trees per dbh class) - Data Measurements

After 1st thinning (61 months) After 1st thinning (87 months) Measurements After 1st thinning (101 months) After 2nd thinning (165 months)

Volume equation outside bark: inside bark:

Volume equation outside bark inside bark

Height equation Installation A Installation B Installation C

Height equation A B

C

G rowth trend Mean per treatment Individual values

G rowth trends Mean per treatment Individual values

G rowth trends Mean per treatment Individual values

G rowth trends Mean per treatment Individual values

Analysis Variables: - periodic monthly increment (absolute): total height, dominant height, quadratic mean diameter and volume per tree - periodic monthly increment (percentage): basal area per hectare and volume per hectare Periods: A and B 1 (61 to 87) 3 (147 to 165) 2 (87 to 137) 1 (61 to 87) 2 (61 to 87) C

Analysis Anova: Mixed linear model, with thinning as the whole plot factor and period as the split-plot factor Random effect: block block*thinning Repetition(block*thinning) period period*thinning Fixed effect: thinning Pairwise comparisons: Bonferroni test

Effect on periodic increment of average total height ABC A: only thinning 35% and thinning 35% + pruning were equal B and C : Only thinning 20% was different from the other treatments There is thinning effect

Effect on periodic increment of dominant height No thinning effect

Effect on periodic increment of quadratic mean diameter AB C A, B and C: only thinning 35% and thinning 35% + pruning were equal There is thinning effect

Effect on periodic increment of basal area per hectare AB C A, B and C: only thinning 35% and thinning 35% + pruning were equal There is thinning effect

Effect on periodic increment of volume per hectare AB C A, B and C: only thinning 35% and thinning 35% + pruning were equal There is thinning effect

Effect on periodic increment of volume per tree A A, B and C: only thinning 35% and thinning 35% + pruning were equal There is thinning effect BC

Conclusion No surprise!

Conclusion Thinning affected the growth of total height, diameter, basal area per hectare, total volume per tree and total volume per hectare, but did not affect the growth of dominant height Thinning prevented regular tree mortality Prunning did not affect the growth trend of the variables analyzed