Abstract
Several studies have quantified the responses of Eucalyptus globulus Labill. plantations to weed control on its early development (2–3 years after establishment). However, long-term results of competing vegetation effects have not been included into growth and yield models that incorporate treatments of competing vegetation control, and its interaction with site resource availability. In this article, we compared several models predicting stand volume yield of E. globulus plantations established across an environmental gradient, growing under different intensity levels of competing vegetation control. Four sites were selected encompassing a gradient in rainfall and amount of competing vegetation. Treatments were applied at stand establishment and were monitored periodically until age 9 years. Competing vegetation control intensity levels considered 0, 5, 20, 44, and 100% weed-free cover around individual E. globulus cuttings. Maximum competing vegetation biomass production during the first growing season were 2.9, 6.5, 2.2, and 12.9 Mg ha−1, for sites ranging from low to high annual rainfall. As expected, reductions in volume yield at age 9 years were observed as competing vegetation control intensity decreased during the first growing season. A strong relationship was established between stem volume yield loss and the intensity of competing vegetation control, the amount of competing vegetation biomass produced during the first growing season and mean annual rainfall. The slope of the relationship was different among sites and was related mainly to water and light limitations. Our results suggest that the biomass of competing vegetation (intensity of competition), affecting site resource availability, contribute to observed long-term effects on E. globulus plantations productivity. The site with the lowest mean annual rainfall showed the highest volume yield loss at age 9 years. Sites with highest rainfall showed contrasting results related to the amount of competing vegetation biomass.
Highlights
Expansion of Eucalyptus plantations in the world has been very successful because of their high-volume production and adaptability to a wide range of sites
A strong relationship was established between stand yield loss and the intensity of competing vegetation control, the amount of competing vegetation biomass produced during the first growing season and mean annual rainfall
There is an optimal intensity of competing vegetation control to reach the maximum stand volume yield
Summary
Expansion of Eucalyptus plantations in the world has been very successful because of their high-volume production and adaptability to a wide range of sites. In Chile, Eucalyptus plantations exceed 850,000 hectares, of which 68%. The application of competing vegetation control treatments requires a good understanding of tree growth and how competing vegetation affect site resource availability over time and which key resources affect stand growth [4,5]. It is well known that reducing weeds biomass during early stand establishment can increase light, water and nutrient and site resource availability [6,7,8] allowing better survival and tree growth [9,10,11,12]. Previous studies about managing of the intensity of competing vegetation or weed control (defined as the size of area free of competing vegetation around each tree) have shown an increase in stem volume—as the intensity of control increases in fast growing species such as Pinus taeda L. Previous studies about managing of the intensity of competing vegetation or weed control (defined as the size of area free of competing vegetation around each tree) have shown an increase in stem volume—as the intensity of control increases in fast growing species such as Pinus taeda L. [13], Pinus radiata D.Don [14,15], Pseudotsuga menziesii (Mirb.) Franco [10], and Eucalyptus spp. [16]
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