Evaluation of Atriplex Halimus Germination on Saline Soil Substrates Under Semi-Arid Environment Using a Combination of Germination, Climate and Hydrological Models.

Saline-sodic soils can be revegetated using halophytes. However, poor soil physical conditions can restrict leaching salts and also revegetation. Soil amendments can be used to improve soil physical conditions and leaching of salts to create a favourable condition for plant germination. However, plant communities are controlled by climatic conditions as well as soil conditions. This is particularly important for revegetation of sites located in arid and semi-arid environments where an extended period of dry condition can limit successful seed germination. Consequently, the interaction of soil, climate and plants should be considered for the evaluation of revegetation of saline-sodic soil substrates under natural climatic conditions. For the purpose of the evaluation of the germination success of Atriplex halimus under a typical semi-arid environment of Australia, four replicates of 25 seeds of Atriplex halimus were investigated in their response to salinity and water stress. From these data, the parameters of the hydrotime model, which simulates timing and success of seed germination, were estimated. LARS-WG was used to generate ten year series of rainfalls of a location in a semi-arid region of Australia based on the historical climatic conditions. HYDRUS-1D was used to evaluate the water potential and sodium concentration of different saline-sodic soil substrates under the generated climatic conditions. The results indicated that Atriplex halimus seeds are tolerant to salinity and water stress. Germination with an average of 31% was observed at a water potential of -1.5 MPa although germination reduced to 3% when seeds were exposed to NaCl solution with -1.5 MPa osmotic potential. The numerical simulations indicated success of seed germination on the non-amended soil under the tested semi-arid environment conditions. This study highlighted that the numerical simulations can be used to evaluate revegetation success under natural climatic conditions.

Key words: Atriplex halimus, Germination, Hydrotime model, HYDRUS-1D, LARS-WG