Studies On Dynamic Quality Evaluation And Fertilization Techniques Of Larix Olgensis Henry Seedlings

Seedling quality is a key factor in establishing forest plantations. It is important for improving cultural technique, increasing seedling quality and ensuring afforestation success to study staged seedling quality indicators in various growth periods and effects of major cultural operations on seedling quality.The annual growth span of Larix olgensis Henry seedling (1-0) and transplanted seedling (1-1) were divided into 4 periods respectively through Logistic Curve Fitting, and the best representative indicators, seedling quality control indicators that can be measured easily, were obtained through Principal Component Analysis of all morphological indicators at the end of each period. These periods and corresponding representative indicators wereâ‘ for seedling (1-0), height and aboveground dry weight in young seedling period (R>0.927), diameter and dry weight of aboveground and underground in the rapid growth period of height and diameter (R>0.929) and in sustained rapid growth period of diameter (R>0.937), height and dry weight of aboveground and underground in later growth period (R>0.93l).â‘¡for transplanted seedling (1-1), dry weight of underground in the initial growth period (R=0.971), diameter and dry weight of aboveground and underground in the height-then-diameter rapid growth period (R>0.902), diameter, dry weight of aboveground and underground, quality index in sustained rapid growth period of diameter and in hardening period (R>0.919). These seedling quality control indicators above can be taken as the staged target to manage seedling quality and adjust cultural operations accordingly, which provide a theoretical foundation for L. olgensis seedling quality evaluation and dynamic management.Effects of basic fertilizer and the combined proportion of nitrogen (N) and phosphorus (P) on L. olgensis seedling quality, and the integrated effect of transplanting density, applying quantity of N and P and additional times of N fertilizer on transplanted seedling quality were studied through randomized complete block design and quadratic orthogonal rotation combination design, respectively. The results ware shown as follow:(1) Organic fertilizer significantly improved the growth and quality of L. olgensis seedling. The height, diameter, total dry weight and N, P and K contents of the seedlings treated with organic fertilizer were 1.60,1.26,2.78, and 2.38,2.15,2.60 times of that with inorganic fertilizer, respectively. Excessive application of inorganic fertilizer restrained the growth of L. olgensis seedlings and reduced their quality. (2) Combined proportion of N and P affected significantly the growth and quality of L. olgensis seedling. In this trial site that effective nitrogen is abundant, seedling height and diameter showed a decrease trend as combined proportion of N and P increased. (3) Transplanting density, applying quantity of N and P and additional times of N had significant effects on the amount of lateral root longer than 1cm, K concentration of roots and total K content of transplanted seedling. In this trial levels, the amount of lateral root longer than 1cm decreased as applying quantity of N and P increased; N significantly enhanced the K concentration of roots; total K content increased as applying quantity and additional times of N increased. (4) Applying quantity of P, combined proportion of N and P and additional times of N affected the growth of height, diameter and biomass of the transplanted seedlings. In this trial levels, the height increased as the applying quantity of N increased prior to the period of rapid growth and reduced as the additional times of N increased later; diameter decreased as the applying quantity of P increased; total biomass showed an increasing tendency as the applying proportion of N and P increased.The relationship between seedling quality and outplanting performances was established through comparing the survival rate and the growth of seedlings and transplanted seedlings between grades. Total new roots longer than 1cm (TNR>1cm) can be used to evaluate the viability of seedlings between various ages and grades. The survival rate and growth of the first year showed a close relation with shoot-root ratio and height-diameter ratio. The seedling survival rate reached up to 95 percent when shoot-root ratio was between 0.59-1.27 (1-0) and 1.20-2.35 (1-1), respectively, and the height growth in the first year was greater than 24 cm and 12 cm when height-diameter ratio was between 38.20-52.40 (1-0) and 69.29-99.27 (1-1), respectively. Gradeâ… seedlings (1-0) (height>20cm, diameter>0.45cm) could be used to afforest in Jilin province and the field performances of too big transplanted seedlings (1-1) (height>70cm, diameter>0.75cm) were not as good as expected.