The different spatial expansion strategies of clonal plants are the result of their adaptations to extreme heterogeneous environments. In this paper, the spatial expansion strategy and the adaptive responses of Phragmites australis to environmental factors were analyzed by comparing clonal modules along degradation gradients (from wetland ecosystem to desert ecosystem). The results show that:
1) With the deterioration of the environmental conditions, the clonal modules (rhizome internode length, spacer length, primary rhizome length and branch angle) showed a trend of first increasing and then decreasing, but the ramet number showed a trend of decreasing first and then increasing, which turned the survival strategy from “Phalanx” (with cluster distribution and showing the invasion attitude) to “Guerilla” (with discrete distribution and showing the evasive attitude) and then back to Phalanx in the process of space expansion.
2) The clonal modules were significantly different in the heterogeneous environment, and were shown the co-development and trade-off relationships (P<0.05).
3) Soil water content, bulk density, pH value and salinity were the main driving forces – especially soil water content, bulk density and pH values in the middle and deep layers and the soil salinity of each layer were the most important environmental factors.
The space expansion strategies of Phragmites australis in an extreme environment complemented the theories of traditional cloning plant ecology. And there was important guiding significance for the management and restoration of the degradation wetlands in arid and semi-arid regions to clarified environmental driving forces of clonal plants in inland river wetlands.