Allocation, morphology, physiology: multiple aspects of above- and below-ground responses to water table stress, duration of drainage in alpine wetland plants (Carex muliensis)

Plants respond to resource stress by modifying various aspects of morphology, physiology, and allocation. Yet, a comprehensive understanding of the mechanisms governing the functional coordination between phenotypic plasticity (the ability to regulate traits) and phenotypic integration (degree of association and coordination between traits) in alleviating resource stress remains elusive.

In alpine wetland, we investigated the interactions among root and leaf functional traits, phenotype plasticity, and integration mechanisms within a dominant species, Carex muliensis, under three water level treatments (control, deep, shallow) and two drainage durations (long-term, short-term).

Declining water table prompted a shift in leaf towards resource-conserving strategies, typified by reductions in specific leaf area and photosynthetic efficiency. Conversely, root shifted towards resource-acquisition strategies to improve competitiveness under low water tables. Notably, a discernible trade-off, manifests between leaf and root phenotypic plasticity and integration across instances of long-term drainage, while short-term drainage scenarios exhibit a synergistic relationship, between these attributes. This observation suggests that long-term drainage fosters a diminution in the integration of leaf and root traits despite heightened plasticity, contrasting with the more cohesive response observed in the context of short-term drainage.

We conclude that, declining water table altered the resource use strategies of plant leaf and root, and trade-offs/synergistic relationships between leaf and root phenotypic plasticity and integration contributed to plant adaptation to drainage durations. This study contributes to the understanding of the role of leaf and root overall phenotypic plasticity and integration in plant adaptation in the context of declining water tables of alpine wetlands, and will help predict the future dynamics of alpine wetland ecosystems.