Abstract
Global climate change is increasing the frequency of extreme weather events and disrupting rainfall patterns, with far-reaching consequences for ecosystems. Plant growth and development processes are extremely sensitive to water conditions, so understanding the effects of rainfall variability on seedlings is critical. However, it is unclear how Cyphomandra betacea seedlings respond to changes in rainfall. This study investigated the response of Cyphomandra betacea seedling biomass, nutrient accumulation, and non-structural carbohydrates (NSC) content to different rainfall intervals and amounts. Using two rainfall intervals, T (3 day) and T+ (6 day), and three rainfall events, average monthly rainfall was used as a control (W), with a corresponding 40% increase in rainfall (W+) and 40% decrease in rainfall (W-) as rainfall treatments. The result showed that increasing rainfall under both rainfall intervals significantly promoted (P < 0.05) the growth of seedling height and soil diameter. The accumulation of root and stem biomass was reduced under the T+ rainfall interval. There was a correlation between the contents of NSC and C, N, and P and their stoichiometric characteristics in seedlings, Changes in N content among organs were crucial for NSC and its fractions and constrained the interconversion of soluble sugar (SS) and starch (ST). At T intervals, more rainfall favored N partitioning into stems and P partitioning into leaves; at T+ rainfall intervals, C and N partitioning into leaves was favored; and more rainfall significantly increased C, N, and P contents in all organs (P < 0.05), but decreased C:N and C:P in all organs of seedlings. In conclusion, the simulated July W+T treatment was effective in improving seedling growth and promoting the accumulation of non-structural carbon and C, N, and P contents in various organs.