Data from: Anatomical traits explain drought response of seedlings from wet tropical forests

Water availability regulates plant community dynamics, but the drought
response of seedlings remains poorly known despite their vulnerability,
especially for the Asian tropics. In particular, discerning how functional
traits of seedlings mediate drought response can aid generalizable
predictions of tree responses to global environmental change. We assessed
interspecific variation in drought response explained by above- and
below-ground seedling traits. We conducted a dry-down experiment in the
greenhouse using 16 tree species from the humid forests of Western Ghats
in southern India, chosen to represent differences in affinity to
conditions of high and low seasonal drought (seasonality affiliation). We
compared survival, growth, and photosynthetic performance under drought
and well-watered conditions, and assessed the extent to which species’
responses were explained by seasonality affiliation and 12 traits of root,
stem, and leaf. We found that the species from seasonally dry forest
reduced photosynthetic rate in drought compared to well-watered
conditions, but seasonality affiliation did not explain differences in
growth and survival. Performance in drought vs well-watered conditions
were best explained by anatomical traits of xylem, veins and stomata.
Species with larger xylem reduced their growth and photosynthesis to
tolerate desiccation. In drought, species with smaller stomata correlated
with lower survival even though photosynthetic activity decreased by a
larger extent with larger stomata. Overall, anatomical traits of xylem and
stomata, directly related to water transport and gas-exchange, played a
more prominent role than commonly used traits (e.g., specific leaf area,
leaf dry matter content) in explaining species response to drought, and
may offer a good proxy for physiological traits related to drought
tolerance of seedlings. --