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Spatial partitioning of competitive effects from neighbouring herbaceous vegetation on establishing hybrid poplars in plantations.

Goehing, J., Henkel-Johnson, D., Macdonald, S. E., Bork, E. W., & Thomas, B. R. . 2019. NRC Research Press


Spatial effects of vegetation control on early tree growth were investigated in central Alberta, Canada for four years after the establishment of hybrid poplar plantations including two clones: Walker (Populus deltoides x (P. laurifolia x P. nigra)) and its progeny Okanese (Walker x (P. laurifolia x P. nigra)). Tree survival and growth, herbaceous vegetation cover, soil nutrient availability, moisture and temperature, and light availability were assessed. Tree growth in the first two years post-establishment was improved through selective in-row vegetation control close (within 50 cm) to trees for both aboveground (mechanical) and above- and belowground (chemical) control. This was associated with increased light availability for trees. In contrast, growth in the third and fourth years benefited from control of aboveground vegetation within 140 cm of the stem and this was associated with increased nutrient availability. These findings suggest effects of neighbouring vegetation on trees shifts from aboveground competition near the tree stem to belowground competition further (> 50 cm) away; thus between-row vegetation control is more important starting in the third year after establishment. Okanese outperformed Walker poplar across all treatments and was more responsive to vegetation control, reflecting its superior performance, higher plasticity, and greater potential for short-rotation-intensive-culture plantations.

Key Words

hybrid poplar, tree growth, aboveground and belowground competition, resource availability, vegetation management.