Determining the optimum climate preseason for plant phenology analysis using rubber (Hevea brasiliensis) as a model

Identifying the optimum preseason that best explains subsequent plant phenology is essential to understanding how climatic factors influence plant growth. This study evaluated the preseason (30, 60, 90, 120, and 180-day) influence of average temperature and rainfall accumulation on the two primary phenological events for rubber (Hevea brasiliensis): refoliation, or start of season (SOS), and defoliation, or end of the season (EOS). These phenological events were derived from Moderate Resolution Imaging Spectroradiometer (MODIS) Normalized Different Vegetation Index (NDVI) time-series data over a ten-year period (2010 to 2019). Pearson correlation and multiple linear regression analyses were performed using these datasets to determine the optimal climate preseason for rubber phenology, based on the highest coefficient results. The results showed that the 90-day preseason conditions prior to the SOS and EOS were critical in advancing or delaying the start and end of the rubber season compared to other preseasons, indicated by the best combination of moderate to high correlation values. The 90-day preseason had the highest coefficient of determination (R2) and lowest root mean standard error (RMSE), confirming its utility for identifying preseason conditions for studying rubber phenology.