Water Requirement Rule Of Seabuckthorn And Amorpha Fruticosa And Design Of Afforestation Without Irrigation

Object:Under the condition of irrigation,the water demand rules of Seabuckthorn and Amorpha fruticosa based on different water gradients were determined.On the basis of non-irrigation,the reasonable planting position of Seabuckthorn and Amorpha fruticosa and the soil moisture distribution characteristics and dynamic growth of different soil preparation measures were explored.Combined with the experiment,the suitable planting density of Seabuckthorn and Amorpha fruticosa was designed,in order to provide theoretical basis and practical basis for soil and water conservation afforestation in the arid zone of the Manas river basin.Methods:In this thesis,the combination of pit method and field test was used to explore the water demand and water demand intensity of Seabuckthorn and Amorpha fruticosa in each growth period under five water gradients.The variation trend of ET₀ and forest coefficient was analyzed by PM formula,and the water demand law of crops was finally obtained.Field experiments were used to explore the effects of different site conditions and engineering treatments on the soil moisture of Seabuckthorn and Amorpha fruticosa.On this basis,the reasonable stand density of the field test area was determined by combining the rainfall during the growth period,the evapotranspiration law of crops and the comprehensive analysis of the water demand of the test plants after engineering treatment.Results:（1）The water demand of Seabuckthorn and Amorpha during the whole growth period showed a trend of increasing first and then decreasing.The specific performance was as follows:fruit expansion period>flowering and fruiting period>early growth period>late growth period.The proportion of modulus ratio coefficient in fruit expansion period was 72.52%-64.73%and 68.33%-64.44%,respectively.The proportion of the late growth period was 3.48%-5.78%and 4.99%-6.63%.（2）The growth indexes of Seabuckthorn and Amorpha during the whole growth period increased first and then gradually approached the horizontal state.The specific changes of plant height and ground diameter under different water gradients were W5（400 mm）>W4（350 mm）>W3（300 mm）>W2（250mm）>W1（200 mm）.The crown width and shoot length of Seabuckthorn were W4>W3>W5>W2>W1,and that of Amorpha fruticosa was W4>W5>W3>W2>W1.The changes of net photosynthetic rate（Pn）,transpiration rate（Tr）and stomatal conductance（Gs）of Seabuckthorn and Amorpha fruticosa were basically the same,which were bimodal curves.Through the study,it was found that there was a turning point between the 14:00 and 18:00 curves,and the phenomenon of’photosynthetic midday depression’appeared.In summary,W4 treatment is more conducive to the growth and development of Seabuckthorn and Amorpha fruticosa.（3）On the time scale,the soil water storage of Seabuckthorn and Amorpha fruticosa had significant changes under different site conditions.The specific performance was that the soil water storage was shady slope>sunny slope,slope bottom>slope middle>slope top.According to the distribution of soil moisture,it can be divided into:consumption period（May-June）,rapid replenishment period（June-July）,and regression period（July-September）.On the spatial scale,according to the analysis of soil moisture content in slope direction and slope position,it was found that the maximum moisture content of Seabuckthorn and Amorpha fruticosa in shady slope and sunny slope appeared in 40-60 cm soil layer,and the peak moisture content of slope top slope and slope bottom appeared in 50-60 cm soil layer.According to the coefficient of variation,the soil water in each plot was divided into significant change layer（Cv>0.2）,secondary change layer（0.2>Cv>0.1）and relatively stable layer（Cv<0.1）.（4）Seabuckthorn and Amorpha fruticosa have a significant effect on soil moisture after mechanical land preparation.The overall soil moisture in Seabuckthorn land increased by 3.26%,and that in Amorpha fruticosa land increased by 2.92%.The effect of fish-scale pit treatment on soil available water in 20-40 cm soil layer was greater than that in 60-80 cm soil layer.Conclusion:According to the rainfall conditions in the test area for many years,combined with the water demand law of the test plants,it is inferred that the suitable planting density of Seabuckthorn is 2340plants/hm² and that of Amorpha fruticosa is 2169 plants/hm².