The Plant Photosynthetic Physiological Characteristics Of Typical Steppe In Inner Mongolia Advantage In The Context Of Climate Change Research

It is not disputed that the global climate has been changing. Photosynthesis is one of the physiological processes, which are the most sensitive to environmental changes. Warming, precipitation enhancement and nitrogen deposit enriched wil! affect it. Research responses of plant photosynthesis characteristics to the climate change, which is important for revealing the adaptability mechanism of plants to climate change.This study used the data from a manipulative experiment in Duolun County, Inner Mongolia, China, systematically explores warming, precipitation enhancement and nitrogen addition affected the photosynthesis physiological characteristics. The thesis mainly included two parts. The first part focused on the impacts of warming, precipitation enhancement and nitrogen addition on important photosynthetic parameters of the two dominant species, Stipa Krylovii and Artemisia frigida, a temperate steppe in northern China. The second part of this study was to compare the differential influences of warming (day, night and diurnal warming), precipitation enhancement and nitrogen addition on nutrient elements of Artemisia frigida. The key findings are as follows:(1) The impact of precipitation enhancement on plant photosynthesis was greater than warming and nitrogen addition. The responses of Stipa Krylovii and Artemisia frigida to warming, nitrogen addition and precipitation enhancement were not significant, constrained by water condition and significant, respectively. And the interactions of warming and nitrogen addition, warming and precipitation enhancement were not significant. The activation energies of RuBP carboxylation and regeneration were not significantly different among them, and positively correlated with soil temperature, while negatively correlated with soil moisture.(2) Warming inhibited plant photosynthesis to some extent. It decreased net photosynthetic rate, transpiration rate, stomatal conductance and leaf mass per area of Stipa Krylovii and Artemisia frigida, while increased dark respiratory rate. The inhibition of warming at the rate of RuBP carboxylation was greater than regeneration. Additionally, it decreased capacities of potential photosynthesis and use weak light, increasing CO2diffusion capacity.(3) Nitrogen addition inhibited plant photosynthesis because of constrained by water condition. It increased leaf nitrogen content per area, while decreasing the photosynthesis of Stipa Krylovii and Artemisia frigida, might affected by water condition. It decreased net photosynthetic rate, transpiration rate, stomatal conductance and leaf mass per area, while increased water use efficiency. The inhibition of nitrogen addition at the rate of RuBP carboxylation was greater than regeneration. Additionally, it decreased capacities of potential photosynthesis and use weak light, increasing CO2diffusion capacity.(4) Precipitation enhancement significantly promoted plant photosynthesis. Precipitation enhancement increased net photosynthetic rate, transpiration rate, stomatal conductance and dark respiratory rate of Stipa Krylovii and Artemisia frigida. It decreased water use efficiency and leaf mass per area. The improvement of precipitation enhancement at the rate of RuBP carboxylation was less than regeneration. Additionally, it increased capacities of potential photosynthesis and use weak light, decreasing CO2diffusion capacity.(5) The impacts of warming, nitrogen addition and precipitation enhancement on the contents of nutrient elements in reproductive branches and vegetative branches of Artemisia frigida were similar, and negative effects were greater than the positive. Warming decreased the contents of N, Al, Fe, Mn, Ni etc., while increased the content of C. Nitrogen addition decreased the contents of P, Al, Fe, Ca, Cu, Ni, Zn, N etc., while increased the contents of Mn. Precipitation enhancement decreased the contents of Fe, Mg, Mn, N, Ni etc.(6) The negative effects of night warming on the contents of nutrient elements of Artemisia frigida were greater than day warming. There was interaction between night and day warming. The impacts of day warming on the contents of nutrient elements were not significant. But night warming significantly decreased the contents of Al, Fe, Mn etc. The interaction of night and day warming was significantly shows on the effects of Al, Cu, Fe, K, Mn, Ni and Zn.