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Keywords:

  • dioecy;
  • functional trade-offs;
  • nitrogen;
  • physiological compensation mechanisms;
  • reproductive investment;
  • δ13C

Summary

  • Differences in reproductive investment can trigger asymmetric, context-dependent, functional strategies between genders in dioecious species. However, little is known about the gender responses of dioecious species to nutrient availability.
  • We experimentally fertirrigated a set of male and female Juniperus thurifera trees monthly for 2 yr. Water potential, photosynthesis rate and stomatal conductance were measured monthly for 2 yr, while shoot nitrogen (N) concentration, carbon isotopic composition (δ13C), branch growth, trunk radial growth and reproductive investment per branch were measured yearly.
  • Control males had lower gas exchange rates and radial growth but greater reproductive investment and higher water use efficiency (WUE; as inferred from more positive δ13C values) than females. Fertirrigation did not affect water potential or WUE but genders responded differently to increased nutrient availability. The two genders similarly increased shoot N concentration when fertilized. The increase in shoot N was associated with increased photosynthesis in males but not in females, which presented consistently high photosynthetic rates across treatments.
  • Our results suggest that genders invest N surplus in different functions, with females presenting a long-term strategy by increasing N storage to compensate for massive reproductive masting events, while males seem to be more reactive to current nutrient availability, promoting gas-exchange capacity.