Study On The Adaptive Growth Of Kochia Scoparia In Response Relationship To The Rainfall And Density In The Arid Zone Of Central Ningxia

This paper aims at the issue of the unclear mechanism of the seasonal vegetation growth adaptability affected by rainfall in the ecologically fragile areas of central Ningxia.Taking seasonal vegetation Kochia scoparia as an example,through outdoor barrel planting experiments,under different rainfall and different planting densities,seed germination rate,survival rate,growth characteristics(plant height,stem),physiological characteristics(microstructure,stomata opening,stomata density,photosynthetic rate),Law of water consumption(transpiration of Kochia scoparia leaf surface and soil evaporation),and changes in soil salt content and other angles,the effects of different hydrological years' rainfall and planting densities on the growth of seasonal vegetation Kochia and the salt content of the soil layer were analyzed.Clarified the response relationship between seasonal vegetation growth and rainfall and planting density in ecologically fragile areas in the arid zone of central Ningxia,Clarified the best improvement effect of rainfall and planting densities on soil and vegetation in arid areas of Ningxia,and established the vegetation biomass modeles.Mainly get the following conclusions:(1)Extreme drought stress(extremely low water years)has a significant inhibitory effect on the germination rate,germination index and vitality index of Kochia scoparia seeds.The general trend of the germination process of Kochia scoparia seeds is to germinate slowly first,and then the germination rate increases until it becomes stable in batches.The rainfall in dry years and extremely dry years has a greater inhibitory effect on the seed germination process than the rainfall in wet years and extremely high water years in promoting the process of seed germination.(2)The ratio of leaf evapotranspiration to total evapotranspiration in each growth period of Kochia scoparia under different rainfall levels,from large to small,is fruit maturity stage>fruit swelling stage>flowering and fruit setting stage>seedling stage.The water use efficiency of Kochia scoparia showed a trend of first increasing,then decreasing and then increasing with the decrease of rainfall.With the growth of Kochia scoparia,the ratio of leaf transpiration to total evapotranspiration shows a gradual decrease overall;the water use efficiency of Kochia scoparia at different planting density levels increases first and then decreases with the increase of planting density..(3)The daily changes of Kochia scoparia net photosynthesis rate(Pn),transpiration rate(Tr)and stomatal conductance(Gs)showed "double peak" and "single peak" curve changes,and the daily changes of intercellular CO2 concentration showed high morning and evening.The low"concave" curve change trend in the middle;the net photosynthetic rate(Pn)of Kochia scoparia has a significant positive correlation with its transpiration rate(Tr)and stomatal conductance(Gs),and a significant negative correlation with the intercellular CO2 concentration(Ci).There is no significant correlation with meteorological factors such as atmospheric temperature(Temp),relative air humidity(RH)and photosynthetically active radiation(PAR).(4)In the electron microscope scanning of the microstructure of Kochia scoparia leaves,with the decrease of rainfall,the protruding glands,irregular lobular stems and waxy layer of the epidermis of Kochia scoparia gradually increase,and the stomata opening and stomata density gradually decrease.,The shriveled degree of leaf epidermal cells gradually increased.With the increase of planting density,the epidermal gland spots and irregular small stems and leaves of Kochia scoparia gradually increase,the degree of epidermal cell shrinkage does not change significantly,and the waxiness of the leaf epidermis also shows a gradual increase trend.(5)In the arid zone of central Ningxia,the extremely low annual rainfall is only for the seasonal vegetation Kochia scoparia to maintain its viable state,but it does not reach its water requirement limit,that is,the water requirement for the entire growth period of Kochia scoparia is less than 84.5mm.(6)In the biomass model established by inputting the plant height,basal stem,and root length of Kochia scoparia as single independent variables,the root length of Kochia scoparia has a high correlation with the fresh quality in a rainy year,and the coefficient of determination is 0.773.Kochia scoparia plant height has a high correlation with dry quality,and its determination coefficient is 0.827.In a normal year,the stalk of Kochia scoparia has a high correlation with fresh quality and dry quality,and its determination coefficients are 0.722 and 0.731,respectively.In water years,the root length of Kochia scoparia has a high correlation with fresh and dry quality,and the coefficients of determination are 0.85 and 0.871 respectively.The biomass regression models under different hydrological years with Kochia scoparia plant height,basal stem and root length as input variables have a high correlation with fresh quality and dry quality,and the coefficient of determination ranges from 0.688 to 0.904.The stepwise regression model has high prediction accuracy for the fresh and dry quality of Kochia scoparia under different hydrological years,and its determination coefficient ranges from 0.722 to 0.927.