## 5 Conclusions  
ESs are crucial for maintaining ecological balance and supporting human existence. A comprehensive understanding of their spatiotemporal variation and interactions is essential for formulating effective ecological management strategies. This study focused on the typical ecological barrier zone in the hilly mountainous regions of southern China and systematically analyzed the spatiotemporal variations in five major ESs: food production (FP), carbon storage (CS), water yield (WY), habitat quality (HQ), and soil conservation (SC). Through analysis of trade-offs and synergies, the interaction relationships among the ESs were clearly identified, along with the key driving factors and clustering characteristics underlying their changes.  
The research results indicated that, over the past 23 years, the ESs exhibited significant fluctuations and their spatial distribution showed notable heterogeneity. This finding suggests that long-term sequence analysis more effectively captures the dynamic changes in ecological processes, underscoring the limitations of short-term and periodic studies. Additionally, the analysis of trade-offs and synergies allows for a more comprehensive understanding of the interactions among ESs. The results also demonstrated significant scale effects, with spatial integration becoming more pronounced from the micro to regional scales, while temporal variations reflected the dynamic changes in the competitive and complementary relationships among different services concerning resource allocation.  
This study further explored the multiple drivers that influence changes in ESs, including geographic, socioeconomic, vegetation, and climatic factors. The combined effects of these factors impact the temporal and spatial variations of ESs, providing important evidence for regional ecological management. Additionally, this study identified the predominant combinations of ESs in different regions through bundle analysis, offering practical strategies for optimizing ecological management and conservation measures.  
In summary, this study not only deepens the understanding of ESs but also highlights the importance of the relationships between them. Our analysis provides a better reflection of the fluctuations and long-term trends of ESs and offers scientific support for policymakers, thereby facilitating the effective implementation of ecological management.  
Y.W.: Formal analysis, Methodology, Software, Validation, Writing--original draft, Writing--review & editing. X.H.: Conceptualization, Supervision, Validation, Writing--review & editing. Z.W.: Software, Supervision, Validation, Writing--review & editing. Y.Z.: Writing--review & editing. C.C.: Validation, Writing--review & editing. B.W.: Validation. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Key Disciplines of State Forestry Administration of China (grant number 21 of Forest Ren Fa, 2016), Hunan Province \"Double First-class\" Cultivation discipline of China (grant number 469 of [PERSON], 2018), Hunan Provincial Innovation Foundation for Postgraduate (grant number CX20220739), and Hunan Provincial Innovation Foundation for Postgraduate (grant number CX20240713).  
Data Availability Statement: The datasets are available from the corresponding author upon reasonable request.  
The authors would like to thank the anonymous reviewers for their constructive comments that helped improve this paper.  
The authors declare that there are no known competing financial interests or personal relationships that could have influenced or appeared to influence any work that is reported in this paper.