Long-term response to area of competition control in Eucalyptus globulus plantations

Numerous studies have quantified the responses to vegetation management in Eucalyptus plantations but most publications have reported early responses in tree growth and a gap in knowledge exist about the magnitude and duration of growth responses throughout the whole rotation. We evaluated the long-term response (9 years-old) of E. globulus across a gradient of sites to different intensity levels of free area of competing vegetation around individual tree seedlings. Competing vegetation intensity levels considered free areas ranging between 0 (control) to 2.54 m(2) plus a treatment with total weed control. Competing vegetation biomass production during the first growing season was 2.9, 6.5, 2.2 and 12.9 Mg ha(-1), for sites ranging from low to high annual rainfall. Across sites, maximum response in stand volume ranged between 58 and 262 m(3) ha(-1) at age 9 years and was proportional to the amount of competing biomass controlled during the first growing season. Total competing vegetation control showed the largest response in stand volume at sites with 2.9 and 12.9 Mg ha(-1) of competing vegetation. However, the 2.54 m(2) vegetation control treatment showed the maximum response for sites with 2.2 and 6.5 Mg ha(-1) of competing vegetation. The duration of response for vegetation control treatments ranged between 5 and 9 years. However, at the site with the largest accumulation of competing vegetation biomass the response to vegetation control showed a sustained and divergent response. Our results suggest that vegetation control improved site resources acquisition increasing long-term stand productivity by reducing environmental limitations to tree growth differentially at each site.