Reproduction alternation in trees: testing the resource depletion hypothesis using experimental fruit removal in...

Area of Science:

• Ecology
• Plant Physiology
• Forest Science

Background:

• Mast seeding in forest trees is explained by resource budget models.
• Fruit production depletes stored resources, limiting future flower production.
• These hypotheses are rarely tested in forest trees.

Purpose of the Study:

• To test if preventing fruit development enhances nutrient and carbohydrate storage.
• To determine if resource storage impacts subsequent reproduction and vegetative growth.
• To investigate the effects of fruit removal on nutrient and carbohydrate dynamics in *Quercus ilex*.

Main Methods:

• Conducted a fruit removal experiment on adult *Quercus ilex* trees.
• Measured nutrient (N, P, Zn, K) and starch concentrations in leaves, twigs, and trunk.
• Compared reproductive and vegetative organ production in the subsequent year between treated and control trees.

Main Results:

• Fruit removal prevented nutrient depletion (N, Zn) in leaves during fruit growth.
• Altered seasonal dynamics of Zn, K, and starch in twigs, with no trunk effect.
• Increased female flower and leaf production, but decreased male flower production the following year.

Conclusions:

• Resource depletion impacts male and female flowering differently due to distinct organogenesis timing and positioning.
• Nitrogen and zinc availability appear to constrain flower production in *Q. ilex*.
• Further multi-year experiments are needed to elucidate causal links between resource storage and flowering in masting species.