Abstract:Population structure and spatial distribution patterns of a naturally regenerated Jatropha curcas L.population were studied in a dry hot valley of Yuanmou in Yunnan.The objectives were to analyze the population structure type,the characteristics of the population’s spatial distribution pattern and their factors.Size class structure was analyzed by means of space-for-time substitution.Spatial distribution of the population was evaluated with the index of dispersion,Morisita’s index,Green’s index,mean crowding intensity,and the parameter K of the negative binomial distribution.The Greig-Smith method of pattern analysis was also used in this study.Results indicated that the amount of seedlings,accounting for 79.84% of the total,were much more abundant than that of the other four demographic stages (sapling,young trees,medium trees,and large trees),whereas the amount of the large trees were very scarce.The size structure diagram showed an expansive type population pyramid.In general,the population followed a clumped distribution pattern,yet the distribution pattern differed in different developmental stages.The distribution pattern of the population generally transformed from aggregated distribution into random distribution with age,which often occurred at medium or large tree stages for the population.Greig-Smith pattern analysis revealed that the scale of the spatial pattern varied among the populations from different plots,and the identified patch sizes were about 50 m2 and 100 m2 in this study.