Unveiling secrets from the past: wood anatomy to disentangle masting and drought

Reconstructing masting, the variable and synchronized seed production by a plant population, is key to assessing trees species resilience to past climate variability and predict fecundity of forest ecosystems under global warming. Masting has shifted in recent decades, linked to climate warming, with consequences for seed production and forest reproduction, and wider cascading effects on forest food webs. Nevertheless, we have little understanding of natural long-term variability in masting, and no method to reconstruct masting in the absence of annual seed-crops observations.

Here, we investigated tree-ring width and a wide range of wood anatomical traits to disentangle the effect of masting and drought on wood anatomy, using individual times series (1980-2022) from Fagus sylvatica (L.) cores sampled in Woodbury (UK). Results showed that tree-ring width and the majority of wood anatomical traits were correlated with current-year May temperature, precipitation, and SPEI drought index, while stronger correlations were observed with previous-year summer conditions. In contrast, masting, quantified as seed production, mainly correlated with summer conditions two years prior. This complex multi-year pattern, supported by literature, is further reinforced by the evident one-year lag between the TRW chronology and the seed production time series.

These results set the premises for the implementation of a structural equation model that incorporates the underlying connections between biotic and abiotic variables. This approach will establish the possibility of disentangling of drought and masting effects on wood anatomy, and provide the basis for masting reconstructions using wood anatomy. The reconstruction of past masting events beyond current limitations is of extreme ecological relevance under ongoing climate condition and highlights the potential offered by wood anatomy in this framework.