The smallest administrative unit of the sixth national census-township (town) is selected as the basic unit, the population spatial distribution characteristics at the township (town) level in karst mountainous areas of northwest Guangxi are analyzed by using Lorenz curve and spatial correlation analysis method, and the influence intensity of natural factors on regional population spatial distribution is detected by using geographic detector method. The results show that: 1. the spatial distribution of population at the township (town) level has the characteristics of imbalance, showing generally significant positive correlation and certain aggregation; 2. There are significant differences in the impact of the spatial distribution of various natural factors on the population distribution. For the towns without karst distribution in the northwest and central south of the study area, the population density increases with the increase of factors conducive to human residence, but the average population density is only 79 people/km². In the towns with karst distribution in the East and south, the spatial distribution of population density and natural factors is not a simple increase or decrease relationship, but fluctuates with the change of karst distribution area. 3. The factor detection results of the geographic detector show that the altitude has the greatest impact on the spatial distribution of population. The interactive detection results show that the impact intensity of any two natural factors after superposition and interaction presents nonlinear enhancement and two factor enhancement. It can be seen that the karst mountain area in northwest Guangxi is similar to other areas. Altitude is one of the main factors affecting the spatial distribution of population, but the river network density and unique geological landform of karst mountain area have a strong catalytic effect on the spatial distribution of population. The superposition and interaction with other factors can further strengthen the impact on population distribution.

With the continuous development of facilities and horticulture, the area of vegetable planting in facilities increased year by year. Watermelon (Citrullus vulgaris Schrad) as the main cultivars within the facility, the continuous cropping problem is very serious, resulting in continuous cropping obstacles become increasingly obvious, the incidence of fusarium wilt increased year by year. Grafted watermelon roots developed to improve the growth of grafted roots of the conditions, resulting in robust plant growth. At the same time, the use of different purposes of the rootstock can make watermelon in different soil conditions under normal growth, such as the use of low temperature, drought, salt tolerance, barren and other characteristics of the rootstock. Secondly, the rootstock of the strong absorption of water absorption capacity, to promote the growth of grafted watermelon plants strong, large watermelon fruit, high yields. In addition, grafted watermelon seedlings grow fast early, for early maturing cultivation and overcome the seedless watermelon early growth slow defects is extremely favorable. So the use of pumpkin as a watermelon grafting rootstock, can effectively improve the effect of watermelon resistance to Fusarium wilts. And provide the theoretical basis and scientific basis for the further study of photosynthetic characteristics, disease resistance breeding and effective control of watermelon. In this experiment, the watermelon varieties with different resistance to fusarium wilt were selected, and the anti-fusarium wilt watermelon was studied systematically. There are changes in physiological characteristics during growth and development. In conclusion, grafting promotes the growth of watermelon and physiological characteristics of the index rose.

KEYWORDS: watermelon; fusarium wilt; growth period; physiological characteristics

In November 2018, the sample plot survey method was used to analyze the population characteristics of Lithocarpus polystachyus in the natural secondary forest with different disturbance intensity in Jianning, Fujian Province, and compile its population static life table. The results showed that the number of individuals in the population was small, but it was clustered. With the increase of interference intensity, the first and second age seedlings and young trees decreased. The population types affected by human disturbance are all lacking level V trees, and the population type belongs to primary population (N₁); The undisturbed population lacks level I and II seedlings and young trees, but there are level V trees, and the population type belongs to medium decline population (S₂). In general, all populations of L. polystachyus are unstable and belong to the transitional type. In the static life table, the mortality of level I and II seedlings and young trees is high, the survival rate has a small peak in level III and IV, and then the survival rate decreases rapidly, and the average life expectation of level II is the highest. It shows that artificial conservation measures and appropriate space re-lease are needed to maintain the stability of the population.

In order to study the temperature change trend of the surrounding geotechnical soil during the operation and thermal recovery of the medium-deep geothermal buried pipe and the influence of the geotechnical soil on the operational stability of the vertical buried pipe after thermal recovery. Based on the data of geological stratum in Guanzhong area and the actual engineering application of medium-deep geothermal buried pipe heating system in Xi’an New Area, the influence law of medium-deep geothermal buried pipe heat exchanger on surrounding geotechnical soil is simulated and analyzed by FLUENT software. The results show that: after four months of heating operation, in the upper layer of the geotechnical soil, the reverse heat exchange zone appears due to the higher fluid temperature; in the lower layer of the geotechnical soil, the temperature decreases more with the increase of depth and shows a linear increase in the depth direction; without considering the groundwater seepage, after eight months of thermal recovery of the geotechnical soil after heating, the maximum temperature difference after recovery is 3.02 ℃, and the average temperature difference after recovery is 1.30 ℃ The maximum temperature difference after recovery was 3.02 ℃ and the average temperature difference after recovery was 1.30 ℃. The geotechnical thermal recovery temperature difference has no significant effect on the long-term operation of the buried pipe, and it can be operated continuously and stably for a long time. Practice shows that due to the influence of various factors such as stratigraphic structure, stratigraphic pressure, radioactive decay and stratigraphic thermal conductivity, the actual stratigraphic temperature below 2000m recovers rapidly without significant temperature decay, fully reflecting the characteristics of the Earth’s constant temperature body.