Limited evidence that larger acorns bufferQuercus rubraseedlings from density‐dependent biotic stressors

Abstract

Plant performance and functional traits vary considerably within species, particularly in response to environmental variation. Plant responses may reflect lifehistory trade-offs, such as between resource acquisition and resource conservation. Larger seeds may buffer young plants from the negative effects of environmental variation, such as limitations in nutrients or water. However, whether seed size plays a similar role in how plants respond to variation in their biotic environment, including competition and soil microbial communities, remains poorly understood. Methods: We used a greenhouse experiment to test the interactive effects of intraspecific competition, the origin of the soil microbial community, and seed size on performance and functional traits in Quercus rubra L. seedlings. Results: Intraspecific variation in seedling traits weakly aligned with a resource acquisition-conservation trade-off. Across the wide range of initial acorn mass, competition decreased seedling biomass by about 35%. Competition directly decreased the root mass ratio and indirectly increased specific leaf area and specific root length, via the negative effects on total biomass. In contrast, soil microbial communities had minor effects on seedlings, and we found no differences between plants receiving soil originating from a conspecific adult and plants receiving soil originating from a heterospecific adult. Conclusions: Competition is a more important driver of intraspecific variation in young Quercus rubra seedling performance and traits, both directly and by delaying ontogenetic development, than soil microbial communities. Seed size is an important predictor of seedling biomass, but a larger seed does not necessarily buffer seedlings from the effects of competition.

Verified hypotheses on the “nurse” and “burial” effects on introduced Quercus rubra regeneration in a mesic Scots pine forest

“…However, Long and Jones ( 1996 ) and Clark and Schlarbaum ( 2018 ) revealed that neither acorn size nor mass could be used reliably as morphological indicators of seedling quality or to predict the survival of oak seedlings. Larger seeds deliver more resources at the early stages of seedling development but they do not necessarily buffer young plants from the negative effects of environmental variation (e.g., from limitations in nutrients or water) or competition of other plants (Jevon et al., 2021 ). However, larger acorns are attractive to seed consumers, so they can be more threatened by acorn predators (Buckley et al., 2006 ; Crawley, 2000 ; Merceron et al., 2017 ; Mezquida et al., 2021 ; Myczko et al., 2017 ).…”

Special Issue: The ecology of Quercus-dominated forests in the eastern United States

“…The dominance of Quercus and its economic importance in the eastern United States continued well into the early 20th century, when forest researchers began to notice and document the conversion of Quercus forests to different tree species (Abrams andDowns 1990, Hix andLorimer 1991). The recognition of a potential future decline in the abundance of Quercus triggered a flurry of research focused on seedling and sapling germination and regeneration (Gilbert et al 2003, Dey et al 2008, Hart and Kupfer 2011, Jevon et al 2021. As researchers work to untangle the complexities of Quercus-dominated forests, there has not always been agreement among scientists about how to interpret the data sets we have developed; however, there has always been agreement that researching these ecosystems has high scientific and forest conservation value.…”