Abstract: [Objective] This paper proposed a new method to judge tree horizontal distribution pattern by uniform angle index in order to further improve the theory of the uniform angle index to judge tree horizontal distribution pattern.[Method] 6000 simulated stands with an area of 70 m×70 m and with different densities and distribution patterns were produced by stand spatial structure analysis software (Winkelmass), the 2 field-tested broad-leaved korean pine forests in northeast China were then used to verify the accuracy of the new method for judging the stand and population horizontal distribution pattern, and the results were also compared with R aggregation index and Ripley's L.[Result] According to the conclusion of the mean value of uniform angle index (W) of random distribution stand conform to the normal distribution and its relationships with the standard deviation, this contribution proposed the new method of judgment stand/population spatial horizontal distribution pattern by uniform angle index. The 6000 simulated stands with different density and horizontal distribution patterns were produced by Winkelmass with an area of 70 m×70 m. The results of simulation data showed that the coincidence rate of uniform angle index normal distribution test method was 100% to different density in the same area,and the coincidence rate of aggregation index R increased with the increasing stand area. The judgment results of 70 m×70 m stand area and 50 trees showed that the average distance between adjacent trees was the key factor affecting the judgments results of aggregation index R to tree horizontal distribution pattern and the distance didn't affect the judgment results by the uniform angle index mean value normal distribution test. The results of stand data of temperate pine oak mixed forests on Xiaolongshan showed that stand and population horizontal distribution pattern was consistent with that judged by the new method and Ripley's L test when the confidence level was 0.05, however, the R aggregation index judged Pinus armandii horizontal distribution was random pattern. The results of stand data for Pinus koreansis broad-leaved forest in Jiaohe exhibited that Fraxinus mandshurica and Pinus koreansis horizontal distribution patterns were random by new method, other trees' population were consistent with Ripley's L test. The R aggregation index judged results showed that the stand distribution was cluster pattern, whereas Juglans mandshuric horizontal distribution pattern was random. When the confidence level was 0.1, the results of horizontal distribution pattern judged by the uniform angle index mean value normal distribution test were consistent with Ripley's L test, however, the difference increased significantly when judged by the R aggregation index with Ripley's L test, the confidence level influenced the pattern of the judgment results obviously.[Conclusion] Using the normal distribution test of uniform angle index mean value to judge the stand/population horizontal distribution pattern overcome the two problems.Firstly, uniform confidence interval is not suitable for evaluating the horizontal distribution pattern of sample surveys;Secondly,the distribution pattern of community in less population number might be soloved.Furthermore,this study could improve the theory of the uniform angle index to judge distribution pattern of trees, and enhance the accuracy and application scope.

Key words: uniform angle index, horizontal distribution pattern, the normal distribution test, method