## 3 Results and Discussion
### Factors Affecting SDT Quality Differences Across Regions
Figure 7: Correlation heat map between environmental factors (**A**,**B**) and interactive Mantel test correlation heat map (**C**). *: \(p<0.05\), **: \(p<0.01\), ***: \(p<0.001\). The clustering analysis of soil nutrients and volatile compounds, excluding the PS and SH regions, demonstrated consistent patterns. The T1 group exhibited higher soil available phosphorus (AP) content compared to T2, while the T1 and C1 groups generally showed higher altitude levels than their T2 and C2 counterparts, with the exception of the WLS region. These findings suggest that soil phosphorus content and altitude serve as potential key markers influencing the floral, woody, caramel, fatty, and fruity characteristics of SDT. Specifically, regions characterized by elevated AP content and higher altitudes demonstrated a greater propensity for the accumulation of floral compounds. These results align with previous research demonstrating that high-altitude tea samples contain elevated levels of alcohols with floral and fruity characteristics, while low-altitude regions, such as those producing Xinyangmaojian, exhibit a higher proportion of woody compounds [10,43]. The consistency of these findings across different studies reinforces the significance of edaphic and altitudinal factors in shaping the aromatic profile of tea products. The results of interaction analysis also verified the above conclusions (Figure 7C). This may be due to the long-term growth of tea trees in acidic soil environments. The available phosphorus content in acidic soils is usually at a low level [44]. In order to adapt to this low phosphorus condition, tea trees will promote the synthesis of secondary metabolites, and these secondary metabolites play a positive role in assisting the synthesis of tea flavor substances in the subsequent process. Tea aroma serves as a critical determinant of sensory evaluation and quality attributes. Its formation mechanisms involve stress responses during both pre-harvest natural growth and post-harvest processing of tea plants (_Camellia sinensis_). Stressors enhance the biosynthesis, accumulation, and emission of aroma compounds by activating metabolic pathways, exerting dual functionality: improving tea aroma quality and strengthening stress adaptation through chemical defense mechanisms [45]. Previous studies have shown that the enrichment of phosphorus contributes to the formation of terpen, aliphatic compounds, and aromatic alcohols such as linalool. Phosphorus can effectively promote the formation of flavonoids in tea and the increase of TP, FAA, and caffeine content, thereby improving the nutritional value and aroma intensity of tea [46,47]; however, the phosphorus content needs to be within a certain range, and high concentrations of phosphorus content are negatively correlated with tea quality [48]. In a related study conducted by [PERSON] et al. [49], in Wuyi Mountain tea plantations, tea plants were subjected to two fertilization treatments: high phosphorus (HP, 112.5 kg P\({}_{2}\)O\({}_{5}\)/ha) and low phosphorus (LP, 60 kg P\({}_{2}\)O\({}_{5}\)/ha). The findings indicated that excessive phosphorus application (112.5 kg P\({}_{2}\)O\({}_{5}\)/ha) significantly reduced the accumulation of key aroma metabolites, such as 3-octen-2-oil, 4,8-dimethyl-1,7-nonadien-4-ol, and 3-ethyl-4-methylpyrrole-2,5-dione, in the high-mountain Shuixian tea variety, highlighting the importance of balanced phosphorus management for optimizing tea quality. The aroma characteristics of SDT 'local flavor' can be regulated to a certain extent by regulating the application amount of phosphate fertilizer.