A trade-off between leaf carbon economics and plant size among mangrove species in Dongzhaigang, China

Plant size is closely linked to its leaf trait characteristics, which are
essential for determining its form and function. These relationships
constitute a fundamental component of the global spectrum of plant
diversity. Despite this, the size-trait relationships in coastal mangroves
have often been overlooked, with a common assumption that they would
mirror those found in terrestrial tropical trees. However, recent studies
have begun to challenge this assumption, revealing unique adaptations and
trait variations in mangroves that are influenced by their specific
environmental conditions, such as salinity and nutrient availability. In
this research, we investigated the leaf structural traits, plant height,
and diameter at breast height or basal height (DBH) of 10 shrub and tree
species. This study was carried out along an intertidal gradient within a
mangrove forest located in Southeast China. We found that leaf traits
differed significantly between shrubs and trees in their response to
intertidal gradients, indicating that different species have evolved
specific adaptations to thrive in their respective intertidal zones. This
insight can help us decipher the selective pressures that have shaped
trait evolution. Among all species, leaf carbon (C) economics (leaf dry
mass content, leaf mass per area, and leaf density) decreased
significantly with increasing plant height and DBH. For each growth form
and intertidal zone, the relationships between plant size (height or DBH)
and leaf C economics traits were consistent with those in the pooled
dataset. Our study reveals that mangrove plants exhibit size-related
adjustments in leaf C economic strategies, indicating that plant size
potentially acts as a proxy for the “slow-fast” continuum of plant
performance. This discovery is pivotal for advancing our understanding of
plant functional ecology and for enhancing the precision of global C cycle
models, which are highly responsive to perturbations in atmospheric CO2
and climate change.