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The early growth performances of Pinus densiflora and Larix kaempferi seedlings under open-field experimental warming and precipitation manipulation

XV World Forestry Congress, 2-6 May 2022










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    Environmental stresses do not always adversely affect seedling growth
    XV World Forestry Congress, 2-6 May 2022
    2022
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    Excessively high temperatures and droughts after winter dormancy breaking can affect the growth and mortality of seedlings. An open-field experiment was conducted to understand the growth and mortality of Larix kaempferi seedlings to spring warming and drought treatments, and further to explore if seedlings could recover the growth capability when the treatments ceased. One-year-old seedlings were subjected to two temperature levels (ambient temperature and infrared heater warming of 4 °C compared to ambient temperature) and two precipitation levels (ambient precipitation and drought) for four weeks. Warming and drought treatments decreased the height and root collar diameter of seedlings throughout the period. After the cessation of treatments, mortality rates continued to increase in the drought-treated plots until the end of the growing season in November; the combination of warming and drought treatments had the highest mortality rates, followed by the drought treatment, the control, and the warming treatment. However, the combination of warming and drought treatments increased the biomass accumulation, seedling height, and root collar diameter at the end of the growing season. This indicates that the reduced number of seedlings per plot due to the increased mortality may reduce the negative effects of warming and drought on seedling growth through alleviating resource competition among seedlings. This study shows the growth of Larix kaempferi seedlings could decline under warmer and drier conditions, and such effects are likely to be mitigated by the decreased density due to the increased mortality rates. Keywords: climate change; drought; growth; Larix kaempferi; mortality ID: 3622945
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    Effects of drought stress and nitrogen fertilization on growth and physiological characteristics of Pinus densiflora seedlings under elevated temperature and CO2 concentrations
    XV World Forestry Congress, 2-6 May 2022
    2022
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    Pinus densiflora is the most widely distributed tree species in South Korea. Its ecological and socio-cultural attributes makes it one of the most important tree species in S. Korea. In recent times however, the distribution of P. densiflora has been affected by dieback. This phenomena has largely been attributed to climate change. This study was conducted to investigate the responses of growth and physiology of P. densiflora to drought and nitrogen fertilization according to the RCP 8.5 scenario. A Temperature Gradient Chamber (TGC) and CO2- Temperature Gradient Chamber (CTGC) were used to simulate climate change conditions. The treatments were established with temperature (control versus +3 and +5°C; aCeT) and CO2 (control: aCaT versus x1.6 and x2.2; eCeT), watering (control versus drought), fertilization (control versus fertilized). Net photosynthesis (Pn), stomatal conductance (gs), biomass and soil water content (SWC) were measured to examine physiological responses and growth. Relative SWC in aCeT significantly decreased after the onset of drought. Pn and gs in both aCeT and eCeT with fertilization were high before drought yet decreased rapidly after 13 days under drought. The fastest mortality showed in aCeT but the longest survival was observed in eCeT. Total and partial biomass (leaf, stem and root) in both aCeT and eCeT with fertilization were significantly high, but significantly low in aCeT. The results of the study are helpful in addressing P. densiflora vulnerability to climate change by highlighting physiological responses related to carbon allocation under differing simlulated environmental stressors. Keywords: Climate change ID: 3621653
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    The survival rate and stem moisture content after planting of Larix kaempferi container seedling according to thawing conditions
    XV World Forestry Congress, 2-6 May 2022
    2022
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    This study was conducted to find out the optimal thawing conditions in connection with refrigerated storage in nursery stage in order to maintain high seedling quality until planting in plantation. Refrigerated container seedlings of Larix kaempferi were produced under 32 different thawing conditions [2 thawing timings (April, May) × 2 shadings (shading, non-shading) × 2 packaging boxes (open, closed) × 4 thawing duration regimes (1, 3, 6, 12 days)] and then planted in plantation. We performed four-way ANOVA to test the effect of the thawing conditions on survival rate (SR) and stem moisture content (SMC) of thawed seedling after planting. The SR of L. kaempfer seedlings was statistically different in each of the four factors, such as thawing timing, shading, packaging box and duration, and significant interactive effects of four factors were also confirmed. Thawing showed a higher SR of seedlings in April than in May. In both thawing timings, it showed the highest SR of seedlings in the thawing condition in which light was shaded and packaging box was opened. As thawing duration increased, SR of seedlings decreased. The shading and thawing duration significantly affected SMC of L. kaempferi seedlings. The SMC of seedlings tended to increase as the thawing duration becomes longer, which is opposite to the result for SR. High temperature in the prolonged thawing duration may result in more active growth of seedlings with enhancing water movement in stem, as refrigerated dormant seedlings started growing with thawing. These results suggest that the best thawing condition is thawing duration of less than 3 days before planting and opening package box in well-ventilated shady locations nearby plantation. The optimal thawing condition will improve the quality of seedling production in nursery stages and increase seedling growth performances in plantation stages. Keywords: Deforestation and forest degradation, Climate change ID: 3622374

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