Effects Of Irrigation And Nitrogen Application On Growth And Photosynthesis Of Catalpa Bungei And Picea Saplings

Moisture is inseparable from the growth and development of plants,and can affect the morphological structure and physiology of various nutrients and reproductive organs of plants.As a life element of plants,nitrogen affects the life activities of plants.With global climate change,rainfall has decreased in many areas,groundwater levels have decreased,soil erosion has been severe,and the frequency of drought disasters has increased significantly.Moreover,with the continuous increase of population,people's free development of land resources has led to a sharp reduction in the available land area,deepening of soil depletion,coupled with the blind pursuit of high yields and the extensive use of nitrogen fertilizer,which has not only fundamentally solved soil nitrogen.The problem of lack of resources has led to a decline in the efficiency of nitrogen use.Drought and water shortage and nitrogen deficiency are often restricted by forest growth,but there are few studies on the impact of the two on the growth of forest trees.In this paper,the different water irrigation methods and nitrogen forms were applied to the Catalpa bungei to explore the effects of different water irrigation methods and nitrogen forms on the growth and photosynthesis of Catalpa bungei,and the preliminary study on the effects of irrigation,nitrogen application and their interaction on the photosynthetic capacity of Picea.The study found:1.Under drought stress,the net photosynthetic rate and transpiration rate of Catalpa bungei decreased significantly,which led to the decrease of growth index of Catalpa bungei tree height,ground diameter and stem biomass.However,drought stress significantly increased the root-shoot ratio and water use efficiency of Catalpa bungei,and the degree of change in root-shoot ratio and water use efficiency of nitrogen supply was greater.Nitrogen application can effectively alleviate the effects of drought stress on photosynthesis of Catalpa bungei,and the effect of nitrate nitrogen is best;2.Compared with complete drought,local irrigation in the root zone significantly promoted the growth and photosynthesis of Catalpa bungei,and greatly alleviated the impact of drought stress on Catalpa bungei.In the local irrigation of root zone,nitrogen mainly promotes the extension of fine roots rather than lateral roots to improve the soil moisture acquisition of Catalpa bungei in the moist zone and enhance the adaptability of plants to local drought in the root zone;3.In the root zone local irrigation mode,the application of appropriate amount of nitrogen fertilizer significantly promoted the leaf water content and photosynthetic capacity of Catalpa bungei,and the root zone deep irrigation×nitrate nitrogen?2.0 mM Ca?NO₃?₂?was the most effective treatment.Good,the plant water use efficiency is also higher at this time;4.Under drought stress,the photosynthesis of Picea was seriously affected,but the water use efficiency of Picea increased significantly.Increasing the amount of nitrogen fertilizer could effectively alleviate the effects of drought stress on photosynthesis of Picea and further improve Picea.Water use efficiency;5.The Picea pungens showed high photosynthetic capacity and water use efficiency under different water-nitrogen combination treatments,and its resistance to stress was stronger than other Picea.