Seed dormancy and germination traits of 27 species inhabiting the degraded karst mountain from central Yunnan-Guizhou Plateau: Seed mass and moisture content correlates with germination capacity

Seed dormancy and germination play an important roles in regulating
germination timing and plant fitness in harsh environment, especially for
fragile karst region. Broadening the knowledge regarding seed ecology of
native plant species can improve local restoration management due to the
increased biodiversity and success of seedling establishment, yet few
studies have addressed this. We examined the dormancy types and
germination responses to temperature regimes as well as light conditions
of totally 27 that were dominant or common species inhabiting a degraded
karst mountain from central Yunnan-Guizhou Plateau and assessed the
relationships between seed traits and germination index using a partial
least squares regression (PLSR). Approximately 48% of the investigated
species exhibited physiological dormancy, 37% exhibited nondormancy, 7%
exhibited morphophysiological dormancy, 4% exhibited morphological
dormancy and 4% exhibited physical dormancy. Germination behaviors
occurred in 16 of 27 species. The seed germination of 13 species strongly
responded to seasonal temperature regimes, whereas 12 species were
substantially affected by light conditions. About 94% species germinated
to the maximum percent in warm temperature regimes (20/13 and 25/18 °C),
while the remaining was in cool temperature regime (10/4 °C). The PLSR
analysis indicated a significant positive correlation between seed mass
and T50 m (time to 50% final germination), and a negative correlation
between seed moisture content and percent germination, showing that small
seeds, particularly those with a low moisture content, were more likely to
have a greater germination capacity (including relative less germination
time and higher germination percent) than large seeds in harsh karst
environments. In general, these results strengthen the understanding of
seed dormancy classification of dormant species and germination
requirements of nondormant ones that representative of pioneer species of
early stage of positive succession in seriously degraded sites and provide
suggestion for species selection in local seed-based vegetation
restoration.