Population Structure And Spatial Pattern Of Coniferous Forests In Luoshan,Ningxia

As natural secondary forest species.Picea crassifolia and Pinus tabuliformis are important for biodiversity conservation,water conservation,regional climate regulation and ecological balance maintenance in Luoshan.In this study,one sample plot of 80m X 125m Picea crassifolia,one sample plot of 100m × 100m Pinus tabuliformis,and one sample plot of 100m ×100m mixed forest of Picea crassifolia and Pinus tabuliformis were set up to investigate the survival of the populations and the diameter level of the populations,and the population age structure,static life table,survival curve,mortality curve,disappearance rate curve and survival function curve were analyzed by using the method of diameter level instead of age.The spatial point pattern method was used to analyze the spatial distribution patterns and spatial correlations of populations at different ages and survival conditions,and to reveal the factors limiting population renewal.The main findings are as follows:The age structure of pure and mixed forests of Picea crassifolia was inverted "J" type,which belonged to the declining population;the age structure of pure forest of Pinus tabuliformis was single-peaked,which belonged to the stable to declining over population.The survival curve of the pure forest population of Picea crassifolia tended to be similar to the Deevey-Ⅱ type,and the survival curve of the pure and mixed forest populations of Pinus tabuliformis tended to be similar to the Deevey-Ⅰtype.All populations were characterized by rapid decline in the early stage,stabilization in the middle stage,and decline in the late stage,in accordance with the negative density constraint.The overall plants,overall seedlings,overall young trees,living seedlings,living young trees,dead seedlings and dead young trees of all populations basically showed aggregated distribution at small scales,and the spatial distribution pattern tended to be random as the spatial scale increased;the large trees of all populations basically showed random distribution;the dead plants of pure stands of Pinus tabuliformis showed random distribution;the seedlings and young trees of mixed forests showed aggregated distribution at larger scales.The distribution of seedlings and young trees in mixed forests still showed aggregation at a large scale.Individual large trees of each age group showed negative correlation or weak negative correlation with the overall plants of other age groups at small scales,and the correlation showed no correlation as the scale increased.The spatial correlations between living plants at small scales were positive,and the spatial correlations between dead plants and living plants in pure and mixed forest populations of Picea crassifolia varied from positive to no correlation to weak negative correlation,while the spatial correlations between dead plants and living plants in pure forest populations of oleander were basically no correlation.This study takes all the plants in the Luoshan coniferous forest sample site as the object of study,and further deepens the understanding of the survival status,future trends,spatial distribution patterns and associations of coniferous forest populations in the Luoshan area,thus contributing to a better understanding of their potential degradation mechanisms and succession trends,with a view to clarifying the degradation mechanisms of natural forests and the constraints of understory regeneration,and providing theoretical support for the restoration and functional enhancement of the Luoshan forest ecosystem.This will provide theoretical support for the restoration and functional enhancement of the Luoshan forest ecosystem.