## 5 Conclusions  
Research indicates that, in terms of sensitivity, there are differences in the response of the GPP of natural rubber plantation ecosystems to drought scenarios in different initiation seasons. GPP exhibits relatively higher sensitivity to droughts that occur in the early rainy season while showing less sensitivity to the majority of droughts that occur in the peak rainy season and early dry season. However, highly sensitive drought scenarios also occur within the peak rainy season and early dry season. Compared to gradual droughts, GPP is more sensitive to flash droughts. Additionally, GPP exhibits higher sensitivity to longer-duration drought scenarios. In most drought scenarios, GPP shows higher sensitivity to extreme drought than to mild drought. Overall, GPP exhibits higher sensitivity to extreme flash droughts with a long duration in the early rainy season. In terms of vulnerability, the impact of drought initiation at different climatic nodes on GPP varies significantly. The maximum GPP loss caused by drought initiation at the peak rainy season is higher than that associated with droughts occurring in the early rainy season and the early dry season. The impact of flash droughts on GPP is more pronounced than that of gradual droughts. The damage effect of long duration drought on GPP is higher than that of short duration drought. Meanwhile, the loss of GPP also increases with the intensity of drought. The impact of extreme flash drought with long duration on GPP is obvious. Therefore, complete logging during rubber plantation renewal will lead to fluctuations in productivity. The next research step will consider incorporating the succession process of logging cycles into simulations under different drought scenarios to explore their effects on GPP variation. **Supplementary Materials:** The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/land13060745/s1](https://www.mdpi.com/article/10.3390/land13060745/s1)]([https://www.mdpi.com/article/10.3390/land13060745/s1](https://www.mdpi.com/article/10.3390/land13060745/s1)), Figure S1: Standardized Precipitation Index (SPI) preliminary experiment, intensity \(=-0.75\), initiation season in April (a); August (e); April (i). Intensity \(=-1.25\), initiation season in April (b); August (f); April (j). Intensity \(=-1.75\), initiation season in April (c); August (g); April (k). Intensity \(=-2\), initiation season in April (d); August (h); April (l). The sensitivity of GPP varies with the duration of drought and the SPI time scale; Figure S2: Standardized Precipitation Index (SPI) preliminary experiment. Intensity \(=-0.75\), initiation season in April (a); August (e); April (i). Intensity \(=-1.25\), initiation season in April (b); August (f); April (j). Intensity \(=-1.75\), initiation season in April (c); August (g); April (k). Intensity \(=-2\), initiation season in April (d); August (h); April (l). The vulnerability of GPP varies with the duration of drought and the SPI time scale. **Author Contributions:** Conceptualization and methodology, R.Z., Z.S. and L.W. ; data processing, R.Z., Y.A., Q.B., X.E. and Z.M. ; investigation, R.Z., Z.S., L.W., Y.A., Q.B., X.E., Z.M. and Z.W. ; visualization, R.Z. ; writing of manuscript, R.Z. ; providing and processing vorticity data, Z.W. ; review and editing, R.Z., Z.S., Y.A., Q.B., X.E. and L.W. All authors have read and agreed to the published version of the manuscript. **Funding:** This research was jointly funded by the National Natural Science Foundation of China (Grant No. 42101101, 32160320), the National Key Research and Development Program of China (Grant No. 2021 YFD220040), and the Hainan Province Science and Technology Innovation Talent Platform Project (Grant No. NHXXRCXM202303). Data Availability Statement: All data are available through the website provided, except for data from the Danzhou Rubber Plantation Flux Observation Site.