Abstract
This study aims to identify correlations between growth variables and the Dickson quality index in seedlings of Eucalyptus grandis and Pinus elliottii var. elliottii. The experiment was conducted in a greenhouse and the following variables were observed: stem base diameter, shoot height, number of leaves, leaf dry matter, stem base dry matter, root dry matter, shoot dry matter, total dry matter, ratio of shoot dry matter to root dry matter and ratio of shoot height to stem base diameter in E. grandis 60, 75, 90, 105 and 120 days after seedling emergence, and in P. elliottii 25, 50, 75, 100, 125, 150 and 175 days after seedling emergence. Using Pearson correlation and also path and regression analyses, correlations were analyzed between observed variables according to day after emergence and the Dickson quality index. Stem base diameter was found to have stronger correlation with days after emergence in comparison to shoot height, in both species. Root dry matter was found to have stronger correlation with the Dickson quality index. Stem base diameter was the most suitable parameter to indicate seedling quality due to its higher correlation level with the Dickson quality index. Shoot height was only effective to indicate seedling quality if analyzed together with stem base diameter. Variables relating to dry matter showed the highest correlations with the Dickson quality index (DQI), followed by stem base diameter. Conversely, number of leaves showed the poorest correlations with DQI, followed by seedling height.
Highlights
Production of forest seedlings is one of the most important stages in the establishment of forest stands as it strongly affects forest yield
A simple linear regression analysis was conducted, always computing days after emergence as independent variable, in full and varied competition. These analyses enable identifying, among non-destructive testing variables, those with stronger correlations with Dickson quality index (DQI) and days after emergence, allowing estimations of seedling quality on the basis of time spent in the nursery
In Pinus elliottii, variable height showed a higher correlation with other variables in comparison to Eucalyptus grandis
Summary
Production of forest seedlings is one of the most important stages in the establishment of forest stands as it strongly affects forest yield. A successful, high yielding stand is closely dependent on the quality of planted seedlings, which should be capable of resisting adverse field conditions and grow into trees with an economically desirable volume (GOMES et al 2002). One of the problems faced by producers of forest seedlings involves being able to pinpoint characteristics with which to anticipate seedling size and performance in the field. This type of analysis, according to Reis et al (2008a), is often intuitive and lacks an appropriate definition to explain seedling survival and growth requirements. Identifying the best production methods and planting seasons to ensure good quality seedlings (REIS et al 2008b). Several variables are used to evaluate seedling quality, including shoot height, root configuration, stem base diameter, ratio of shoot to root, ratio of stem base diameter to shoot height, dry and fresh matter weight of shoot and root, shoot stiffness and nutritional aspects (PAIVA & GOMES 1993)
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