| Ziziphus jujuba var.spinosa has the physiological and ecological characteristics of adapting to semi-arid environment with great potential value in vegetations recovery.The dynamic and spatial pattern of Ziziphus jujuba population serves as the theoretical basis for exploring its ecological adaptability and self-renewal capacity.This paper takes the three Ziziphus jujuba populations in Hongsibao District,Wuzhong City,Ningxia Hui Autonomous Region as the research object,based on the diameter characterization of Ziziphus jujuba,soil physical and chemical properties by means of using "space in the place of time",point pattern analysis,soil particle size and total carbon nitrogen content analysis.The population dynamics of the Ziziphus jujuba population were related to the age structure,the spatial distribution pattern of the population's various diameter stages,and the spatial correlation between the age classes and the influence of the Ziziphus jujuba population on the desert steppe soil.The main results are as follows:1)The age structure of the three Ziziphus jujuba populations exhibited a "pyramid" shape.The young individuals are rich in reserves and stable in population;the survival curve tended to be Deevey? type,and the mortality rate in young age was higher.There was a peak mortality rate,which appeared in the second or the third diameter grade(basal diameter is 5-10mm or 10-20mm);the number of young seedlings whose diameter grade was smaller than the fourth diameter grade(15-20mm)was large,and the number of old seedlings whose diameter grade was larger than the fourth diameter grade obviously decreased.The law of Ziziphus jujuba seedlings were dying with age increasing obviously,but it was mainly related to grassland enclosure and ban-grazing in the past 17 years.After 2,4,and 6 diameters in the future,the number of old sensillas would gradually increase,and the number of young plants would decrease.Therefore,if we want the Ziziphus jujuba population to remain stable for a long time,it is necessary to increase certain tending management.2)For the spatial distribution of different ages within the population,the population was aggregated.When it was smaller than the fourth diameter grade(basal diameter is 0-20mm),it had obvious aggregation distribution.After less than the fourth diameter grade,the aggregation intensity decreased,and gradually increased with the increase of the scale.In terms of the correlation between ages in the population,the small diameter plants in the first to third diameter(0-15mm)stages were positively correlated with the adjacent several diameter stages.There was mutual protection.There was no correlation between the small diameter level and the large diameter level of the seventh diameter level(greater than 30mm),which were independent of each other.The distance between different age classes was obviously restricted.The large diameter level and the adjacent several diameter stages were positively correlated within a scale of less than 85m,and they were uncorrelated in a large scale range.Individuals of different ages were staggered in space,forming redundant structures on the population structure,and individuals of different ages were connected in parallel to enhance the stability of the system.3)The Ziziphus jujuba population was distributed in the patch of desertification land.After the soil particle size analysis,it was found that the content of fine sand and coarse sand in the Ziziphus jujuba plot was higher than that of the sticky powder and the fine sand.The content was higher than that of the desert steppe outside the plot and the difference was significant;the total carbon content of soil was lower than that of the desert steppe outside the plot,but the difference was not significant Improvements to the surface soil of the desert steppe have not yet appeared. |
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