Impact Of Simulated Drought And Climate Warming On Larrix Gmelinii Radial Growth

This paper takes Larix gmelinii as study materials to research the effects of climatic va riation (Precipitation reduction and temperature increment) to radial growth by field sim ulation experiment. In precipitation reduction experiment, the artificial forest of Larix g melinii in Mao’ershan was taken as experimental subject to simulate drought environme nt by different degree of closure and to research the influence of drought to radial gro wth by the observation of annual ring width、tracheid and cambium. In climate warmin g experiment, Larix gmelinii transplanted to low latitude areato simulate temperature in crease of living environment. The influence of climate warming to radial growth was st udied by the variation of annual ring width、tracheid and cambium. The climate simula tion experiment provided certain amount of basic data to ecological adaptation of Larix gmelinii to climatic change. 1. Simulation experiment of precipitation reductionThe results showed that the radial growth of Larix gmelinii significantly positively correlated with monthly mean temperature at growing season, and negatively correlated with monthly total precipitation at the end of growing season. The results of mature tracheid of tree core indicated that the number of mature tracheid in snow removal treatment was the largest, followed by the control treatment, and then in 50% and 100% rainfall removal treatment in terms of three plots taken together. Radial length of mature tracheid did not show significant difference among treatments. However, quantity and radial length of mature tracheid among treatments were different. In plot 1, the number of mature tracheid of the four treatments all increased with the increasing of soil moisture, but the radial tracheid length did not show obviously difference. In plot 2, the radial length of mature tracheid in snow removal treatment was significantly smaller than those in other three treatments, while the radial length of mature tracheid in 50% and 100% rainfall removal treatments were not significantly different with that in control treatment. In plot 3, there was no significant difference in the radial length of mature tracheid among four treatments, except the radial length of mature tracheid in 100% rainfall removal treatment was slightly smaller than that in other three treatments. It could be caused by lots of shade and higher soil moisture in plot 3. The results of cambium cell of paraffin showed that the number of expansion cells in plot 3 was decreased with the decrease of soil moisture among different treatments in the beginning of decreasing precipitation (in June). In the end of decreasing precipitation (in August), the number of expansion cells in plot 1 was decreased with the decrease of soil moisture among four treatments. Above-mentioned results indicated that precipitation reduction produced significant impacts on radial growth of Larix gmelinii, while the extent of the influences was determined by the microenvironment of tree growth. In addition, the effects of decreasing precipitation in different seasons on Larix gmelinii radial growth are significant differences.2. Simulation experiment of temperature incrementThe results indicated that Songling with higher latitude, the mean size of cell enlargement was 5 pm, and differentiation quantity was 4 in August, and the mean size of differentiated cell enlargement was 9.9μm, and differentiation quantity was 7 in transplanting area, suggesting the mean values of size and quantity was doubled. Our study showed that temperature was the main factor of radial growth of Larix gmelinii, to some extent, temperature increment was advantageous to the radial growth of trees, including the size and quality of cell enlargement. However, temperature increment could not directly change plant physiological property that controlled by gene, such as growth cycle. But different position showed different influence, trunk had more deeply impacts than branch. While temperature increased and precipitation reduced, radial growth directly decreased, including diameter, quantity and growth cycle of tracheid.