Vegetative and reproductive phenology in a tropical grassland-savanna-forest gradient

Question

Climate, particularly
precipitation, is the primary
factor driving tropical plant
phenology because of its relevant role in regulating
water availability. However, differences
in soil physicochemical properties can also drive resource availability,
potentially affecting plant phenology, especially under similar rainfall regime
environments. We determined whether
seasonality and synchrony of vegetative and reproductive phenophases differ
along a grassland-savanna-forest gradient under the same climate regime
in a Neotropical seasonal ecosystem. We hypothesized that species growing on
shallow, nutrient-impoverished soils have a higher capacity to respond to
precipitation pulses than rich soils.

Location

Serra do Cipó, southeastern
Brazil

Methods

We quantified soil
physicochemical properties associated with fertility and water retention of the
grassland (campo rupestre), savanna
(cerrado) and forest, and determined phenological strategies of 70 species across
the three vegetations types by monitoring vegetative and reproductive
phenophases over one year. For each phenophase, in each vegetation type, we
evaluated seasonality and synchrony of phenological patterns. We quantified the
phylogenetic signal for phenophases to disentangle the relative roles of
historical versus ecological drivers of plant phenology.

Results

Soils from campo rupestre
were more nutrient- and water-limited than those of cerrado and forest. Cerrado
and forest communities had similar phenological strategies, whereas species
from campo rupestre showed strategies that maximize resource acquisition
and conservation. In the cerrado and forest, leafing and flowering patterns
were seasonal, with leaf flushing and flowering peak at the onset of the rainy
season and leaf senescence in the dry season. Conversely, species from campo
rupestre showed continuous leafing and flowering patterns, while fruiting was
seasonal. Phenophases did not show phylogenetic signal.

Conclusions

We demonstrated changes in
vegetative and reproductive phenology that are likely associated with variation
in soil physicochemical properties. We argue that more severe edaphic filters may have shaped different
phenological patterns in campo rupestre.