Study On The Impact Of Climate Change On Seed Germination And Seedling Growth Of Quercus Mongalica

Global warming is already a fact that would affect the global water cycle, thus it will lead to significant changes of precipitation patterns. In order to clarify the impact of future climate change on seeds and seedlings of Quercus mongolica, our study based on the materials of Quercus mongolica seeds of Liangshui National Nature Reserve and one-year-old seedlings, we use indoor growth chamber method(temperature+2℃,+4℃and+6℃, precipitation+30%and-30%) and latitude sequence method(increase temperatures approximately2-6℃precipitation-47%or doubled, continuously measured for2years) to simulate the changes of temperatures and precipitations, based on indoor tests and outdoor simulation tests at the same time. We simultaneously measured photosynthesis, chlorophyll fluorescence and biomass of Quercus mongolica seedlings and germination rate and seedling growth state under field condition of Quercus mongolica seeds, then we made generalized analysis of these data can c ome to the conclusion that:1. With treatment of temperature-precipitation interactions, to some extent, the temperature increased of2℃and4℃groups have promoted the photosynthesis of Quercus mongolica seedlings. The groups which increased temperature by4℃, showed that the net photosynthetic rate is higher than temperature control group. At this time the light compensation point was low and water use efficiency was high, meanwhile, the content of Chlorophyll a, Chlorophyll b, and Chlorophyll a+b was higher than the control groups. Stomatal and intercellular CO2concentration were increased with the rising of temperature, in the case of temperature rise, the limiting value of stomata was lower than control groups, however, all the precipitation groups which increased temperature by6℃experienced a significant decrease in net photosynthetic rate. The decline was due to non-stomatal factors, water use efficiency of the groups which precipitation increased by30%and decreased by30%was also lower than control groups under the same treatment.2. The influence of separate temperature factors on the chlorophyll fluorescence characteristics was more than that of precipitation factors. In July and September, the maximum of photochemical efficiency of increasing4℃groups were slightly higher than the control groups, the NPQ measured in July was higher than that of September dramatically. This might be related with varies of temperatures and water treatments. In general, Fv/Fm of30%less precipitation treatment showed more advantages than30%more precipitation treatment.3The response of biomass index of Quercus mongolica seedlings to temperature and precipitation was far less sensitive than photosynthetic indicators. Temperature, precipitation and their interactions showed insignificant effect on leaf mass, root mass, stem mass ratio, root shoot ratio and specific leaf area, when temperature increased by6℃, leaf mass ratio and stem mass ratio has became larger, whereas root shoot ratio has fallen. In the aspect of biomass allocation, proportion of underground was far more than aboveground. when temperature increased by6℃, the allocation proportion of leaves and stems was higher than control groups, the root of distribution ratio decreased.4.The comprehensive effect of temperature and precipitation had no significant effect in germination rate and survival rate, but the germination rate and survival rate in the Xiaobeihu and Baishilazi were lower than those in Liangshui provenance, in the same temperature conditions, the Baishilazi of germination rate where precipitation increased nearly1times was higher than that of precipitation reduction47%of the Xiaobeihu, but the survival rate but showed the opposite trend, which Baishilazi whith increasing precipitation were less than xiaobeihu whith were reducing in precipitation. This indicated high soil water content is advantageous to the germination of germination stage, but the seedling stage is opposite.5. Through field experiments of Quercus mongolica seedlings with continuous observation for two years, in the first and second year, Quercus mongolica seedling height annual growth, basal diameter annual growth and main root length annual growth trend for consistent response to the combined effects of temperature and precipitation, and this trend was greater in second year. In general, the growth index of Xiaobeihu and Baishilazi were significantly lower than those in Liangshui provenance, and biomass allocation index of Quercus mongolica seedlings in the first and second years showed a different or even opposite trend, this experiment showed that interactive processing of temperature increased and increase or decrease in precipitation is not conducive to the growth of Quercus mongolica seedlings.6. According to the response of Quercus mongolica seeds and seedlings to temperature and precipitation, derived photosynthetic parameters and chlorophyll fluorescence parameters can be used as sensitive indicators of Quercus mongolica seedlings to temperature and precipitation, biomass parameters can be used as the basis to determine a certain lack of environmental factors, temperature rised6℃may be close to the threshold of Quercus mongolica seedlings response to climate change.The field experimental results showed that the interaction of more substantial temperature increases and precipitation increase or decrease is not conducive to the growth and survival of the Quercus mongolica seedlings, especially in the case of increased precipitation. It indicates that such a scenario the updates of Quercus mongolica will be greatly affected.