Divergent reproductive allocation trade-offs with canopy exposure across tree species in temperate forests

Variation in tree reproduction can alter forest community dynamics, especially if reproductive output is costly for other functions like growth. However, empirical studies reach conflicting conclusions about the constraints on reproductive allocation relative to growth and how they vary through time, across species, and between environments. Here, we test the hypothesis that a critical resource, canopy exposure to light availability, limits reproductive allocation by comparing long-term relationships between reproduction and growth for trees from 21 species in forests throughout the Southeastern United States. We found that species have divergent responses to light availability, with shade-intolerant species experiencing an alleviation of trade-offs at high light-and shade-tolerant species showing no changes in reproductive output across light environments. Correlations between temporal variation in individual growth and reproduction were weak and generally insensitive to canopy exposure, but changed when considering time lags. The diversity of responses across species indicates that reproductive allocation for trees in these forests is strongly influenced by both species' life history and environmental heterogeneity in space and time.