The spatial pattern of Nitraria tangutorum shrub islands in the north of Ordos Plateau

The authors applied one of the most commonly used methods,called modified Ripley's K(i.e.(Ripley's) L) function and J function,to analyze the spatial point pattern and marked point pattern of Nitraria tangutorum shrub islands for 3 samples in 3 different towns(Duguitala,Huhemudu and Balagong).The results show that the spatial patterns of Nitraria tangutorum shrub islands in Duguitala,Huhemudu and Balagong were obviously different.In Duguitala,the pattern of Nitraria tangutorum shrub islands was regular in small scale(0-5.0 m),and random in middle and large scales(5.0——50.0 m).In Huhemudu,the pattern was regular in small scale ((0——8.0 m)) and random in middle and large scales (8.0——50.0 m).In Balagong,the situation was more complicated and the pattern was regular in small scale(0——3.5 m),random in small and middle scales(3.5——10.5 m),clumped in middle scale(10.5——19.5 m) and random again in middle and large scales((19.5——)50 m).While the marked point pattern analysis was more detailed and exact in the scale than point pattern analysis.For example,in Duguitala,the scale of regular was 2.9——11.6 m,and the scale of random was 0——2.9 m,11.6——13.5 m and 14.2——50.0 m.The reason causing the different patterns of Nitraria tangutorum shrub islands was the environment heterogeneity caused by different water conditions in the study region.Finally, the authors analyzed the environmental interpretation and ecological significance of the spatial pattern of Nitraria tangutorum shrub islands,and suggested that the utilization,protection and restoration of Nitraria tangutorum shrub islands must base on the relationships among spatial patterns,scales and different succession periods.