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Tree-ring isotopic imprints on time-series of reproductive effort indicate warming-induced co-limitation by sink and source processes in stone pine
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  • Tatiana A. Shestakova,
  • Ester Sin,
  • Javier Gordo,
  • Jordi Voltas
Tatiana A. Shestakova
Universitat de Lleida Departament de Produccio Vegetal i Ciencia Forestal

Corresponding Author:[email protected]

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Ester Sin
Universitat de Lleida Departament de Produccio Vegetal i Ciencia Forestal
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Javier Gordo
Junta de Castilla y Leon Consejeria de Agricultura y Ganaderia
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Jordi Voltas
Universitat de Lleida Departament de Produccio Vegetal i Ciencia Forestal
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Abstract

Increasing evidence indicates that tree growth processes, including reproduction, can be either sink- or source-limited, or simultaneously co-limited by sink and source, depending on the interplay between internal and environmental factors. We tested the hypothesis that the relative strengths of photosynthate supply and demand by stem growth and reproduction create variable competition for substrate that is imprinted in tree-ring isotopes of Pinus pinea, a gymnosperm with large costs of reproduction, under warming-induced drought. Over a 60-yr period, we also identified reproductive phases where weather drivers of cone yield have varied. We found that these drivers gradually shifted from winter-spring conditions three years before seed rain (cone setting) to a combination of three- and one-year lagged effects (kernel filling). Together with positive associations between Δ 13C of the year of kernel filling and cone yield arising at the turn of this century, our results pinpoint increasing dependence of reproduction on fresh assimilates. This indicates sink and source co-limitation superseding the sink-limited functioning of reproduction dynamics dominant before 2000. Under climate warming, it could be expected that drier conditions reinforce the role of source limitation on reproduction and, hence, on regeneration, forest structure, and economic profit of the nutlike seeds of the species.