Abstract: Ephemeral plants germinate at different times in desert. They germinate in spring and occasionally in autumn, but very rarely in summer. Changes of precipitation pattern increase the probability of the occurrence of short-lived summer-germinated plants. However, life history strategy of summer-germinated plants remains unclear. Therefore, we measured key traits and the temporal variations of biomass allocation of summer-germinated plants, Erodium oxyrhinchum, in different growth periods and four different slope positions (the base of the sand dune facing west (BW), the middle of the sand dune facing west (MW), the middle of the sand dune facing east (ME), and the base of the sand dune facing east (BE)) in the Gurbantünggüt desert. We further examined the synergetic effects of different slope position and aspect of sand dunes. We found that: (1) The summer-germinated individuals of E. oxyrhinchum crossed the winter and completed life cycle in early spring of next year, with a life cycle of 281.95±3.55 days. (2) There were differences in the root/shoot ratio of the summer-germinated individuals at different growth stages. The ratio showed a significant increase trend before overwintering (P<0.05), and a significant decrease trend after overwintering (P<0.05). (3) There were significant differences in the key traits of summer-germinated individuals in different slope positions and directions of the sand ridge. Plant height, leaf number and biomass per plant on the west slope were significantly greater than those on the east slope, but there was no significant difference in the root/shoot ratio between different slope positions and directions. It is of great significance to explore life history strategy of summer-germinated individuals of E. oxyrhinchum in different slope positions and directions of sand ridges for assessing the vegetation dynamics of desert ecosystems under the background of climate change.

Key words: summer-germinated plant, root/shoot ratio, slope position, slope aspect