The enormous variation in seed mass along gradients of soil resources has fascinated plant ecologists for decades. However, so far, this research has focused on the description of such variation, rather than its underlying mechanisms. Here we experimentally test a recent model relating such variation to two fundamental properties of plant growth: allometry of biomass growth and size-asymmetry of light competition. According to the model, mean seed mass should increase, and the variance of seed mass should show a unimodal response, to increasing soil resource availability (productivity). We test these predictions and their underlying assumptions using a combination of field observations, mesocosm experiments and greenhouse experiments focusing on Mediterranean annual plants. Our results support the predictions and assumptions of the model, and allow us to reject alternative models of seed mass variation. We conclude that growth-allometry and size-asymmetric light competition are key drivers of seed-mass variation along soil resource gradients.
Bibliographical noteFunding Information:
We thank Lior Iluz and Tzruya Yaari for their technical assistance. We also thank Bill Shipley and two anonymous reviewers for constructive comments on previous version of this manuscript. The study was supported by the Israel Science Foundation grants no. 454/11 and 447/15, the Ring Foundation and the Israeli Nature and Parks Authority. N.D. is supported by the Rothschild Fellowship.
© 2018 John Wiley & Sons Ltd/CNRS
- Annual plants
- community-weighted mean
- community-weighted variance
- competition-colonisation trade-off
- functional diversity
- functional traits
- seed size
- soil depth