Abstract
This study reports the stem volume of 10 Populus genotypes in a randomized split-plot design with different tillage treatments (disking versus sub-soiling) after two years of growth. Height, diameter at breast height (DBH), stem aboveground volume index, survival, Melampsora rust resistance, leaf area index (LAI), chlorophyll content, and foliar nitrogen concentration (Foliar N) were measured to identify how tillage treatments might alter poplar growth. Stem volume index and LAI were positively correlated and differed significantly among tillage treatments, taxa, and genotypes. Melampsora rust resistance was also positively correlated with volume index, but significant differences were only detected among taxa and genotypes. Foliar N and chlorophyll did not correlate to stem volume for genotypes or tillage treatments. Overall, sub-soiling yielded 37% more estimated volume compared to disking. Within the sub-soiled treatments, four genotypes (140, 176, 185, and 356) had high survival (>80%) and produced substantial stem volume (>32 dm3·tree−1). These findings show that tillage practices do impact poplar stem volumes after two years and that sub-soiling improves productivity for poplar short rotation woody crops on loamy fine-sandy soils.
Highlights
International and domestic policies mandate increased reliance on forest resources to decrease greenhouse gas emissions and global dependence on fossil fuels
leaf area index (LAI) in the sub-soiled tillage treatment (Table S4 contains summary statistics for LAI). These results demonstrate that LAI and disease resistance are well correlated with stem volume and selecting for these traits can improve establishment and early stem productivity in poplar short rotation woody crops (SRWC) grown in the southeastern U.S.A
This study found that proper soil tillage and genotype selection will be critical to achieve viable yields
Summary
International and domestic policies mandate increased reliance on forest resources to decrease greenhouse gas emissions and global dependence on fossil fuels. In the U.S.A., the 2010 Renewable Fuel Standard mandates that the volume of biofuel blended into transportation fuels increase from 9 billion gallons in 2008 to 36 billion gallons by 2022 [3]. Given these policies, a large amount of land (between 33 and 51 million hectares (ha)) is needed to grow dedicated biomass in highly productive plantations [4,5]. The southeastern U.S.A. represents a promising region with over 80 million ha in timber production and a large area of marginal and abandoned lands available for dedicated biomass production [6,7,8,9,10,11].
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