Seasonal Asynchrony in Above- and Below-Ground Phenology in a Temperate Forest: Carbon Allocation Trade-off and Plant-Microbe Interactions

Aim Understanding seasonal phenology changes in ecosystems is fundamental to modeling and predicting the response of ecosystem functions such as carbon and nitrogen cycling to climate change. Previous studies of cross-phenological studies mainly focused on the above- and below-ground plant parts, but poorly linked to soil microbes. Method To address this gap, we synchronously investigated the phenology in canopy leaf (by near-surface remote sensing and high-frequency litterfall), fine root (by sequential soil coring), and soil microbial biomass (by chloroform-fumigation-extraction method) for two years in a temperate deciduous broadleaved forest, and explored the correlations between the three parts of ecosystem. Results Root biomass peaked before leaf expansion, but persistently died off during leaf expansion period, suggesting a strong C allocation competition between above- and below-ground parts. The microbial biomass reached a maximum in winter, sharply declined to a minimum during leaf expansion, and recovered after leaf senescence. Moreover, root biomass was remarkedly positively correlated with microbial biomass in the previous, concurrent, and subsequent months, while root necromass and mortality were negatively correlated with microbial biomass in a subsequent month. Conclusion The cross-phenological asynchrony indicates a trade-off in carbon allocation between aboveground and belowground tree tissues, and a complex linkage between root dynamics and plant-microbe interactions. The cross-phenological perspective propose a new model for the interactions between aboveground and belowground phenology.