Study reveals reproductive costs in shrubs are far higher than previously estimated, especially when measured in nutrients
A new study tracking 14 perennial heath shrubs across their full lifetimes found that reproductive allocation — the share of plant productivity devoted to reproduction — is substantially higher than conventional estimates suggest. Researchers measured dry mass, nitrogen, and phosphorus across all aboveground tissue types and applied multiple accounting methods, finding that nutrient currencies, especially phosphorus, dramatically increase the perceived cost of reproduction. The findings suggest that widely used forest growth models may be significantly overestimating how much net primary productivity is available for vegetative growth.
Researchers publishing in bioRxiv tracked 14 iteroparous perennial shrubs across their complete lifetimes, measuring dry mass, nitrogen, and phosphorus in every aboveground tissue type to calculate reproductive allocation (RA) under four accounting schemes and three currencies. They found that RA was substantially higher by mid-life than typical estimates derived from ecosystem-scale studies, and that separating standing biomass from yearly production revised RA estimates upward further. Expressing allocation in nutrient terms — particularly phosphorus — amplified the perceived costs of reproduction considerably, as propagules were found to be highly nutrient-enriched. Reproductive accessory structures consumed even more nutrients than the propagules themselves, and nutrient resorption from senescing leaves and wood shrank the effective vegetative nutrient budget, concentrating net annual nutrient demand in reproductive tissues. Broadly consistent allocation patterns were observed across species with differing functional traits and lifespans, suggesting the findings may generalize across biomes. The authors conclude that widespread underestimation of RA in forest growth models likely leads to substantial errors in predictions of vegetative growth and carbon cycling.
What's missing
The sample size of 14 shrubs from heath ecosystems may limit generalizability despite the authors' claims of broad applicability. It is also unclear how the proposed corrections to forest growth models would quantitatively affect carbon budget predictions at regional or global scales.
What different sources said
- bioRxivCenter
Nutrient currencies and P resorption greatly amplify the perceived costs of reproductive allocation in perennial heath shrubs
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