I. The Impact of Altitude on Aroma

When Tea trees grow in different environments, it leads to noticeable differences in their aroma characteristics. The influence of altitude is primarily the result of comprehensive climatic conditions. In high-altitude tea gardens, tea trees grow in misty conditions with high air humidity, shorter and weaker sunlight exposure, more blue and violet light, and greater day-to-night temperature variations. This environment promotes the formation of more proteins, amino acids, and aromatic oils, while reducing sugars and polyphenols, resulting in softer leaves with better tenderness. Teas produced from these leaves have a higher aroma and superior quality.

On the same soil, under high-altitude conditions, tea trees form more high-boiling-point aroma substances, which are components that provide a strong and lasting fragrance. Under low-altitude conditions, tea trees form larger quantities of low-boiling-point aroma components, and both the content and variety of high-boiling-point components are inferior to those at higher altitudes. Areas with higher altitudes and lower temperatures lead to slower growth of tea trees, which is one of the reasons for the development of their unique aroma—a phenomenon commonly known as “high mountains produce fine teas.”

Many famous teas with unique aromas come from high-altitude environments, such as Tieguanyin from Anxi, Jin Huanggui, Rougui and Shuixian from Wuyi, Huangshan Maofeng, Lushan Yunwu, and Qiyun Shan Guapian. However, some areas, although not at high altitudes, have climate and soil conditions similar to those found at high altitudes, such as Fuxikou, Liukou, and Xikou in the premium tea-producing region of Tun Green Tea, and Shifeng in the premium Dragon Well tea-producing area. Despite being at lower altitudes, they have favorable microclimates, and the green teas produced there are no less fragrant than those from high-altitude areas.

II. The Impact of Season on Aroma:

The aroma of tea is influenced by seasonal changes, as temperature, humidity, rainfall, sunlight intensity, and the nature of light all vary throughout the year. China's tea regions experience distinct seasons, and generally, spring teas have a high and lasting aroma, followed by autumn teas, which although have a high aroma, lack the same level of persistence. Summer teas have the lowest aroma.

The types and contents of aromatic substances in each season are different. Spring teas contain ethanal, pentenol, and other substances with fresh or grassy aromas, as well as nonanal, ethyl acetate, dimethyl sulfide, elemene, and geraniol, which contribute to the fresh tea and floral aromas. These components are less prevalent in summer teas but are present in greater amounts in autumn teas, which contain more phenylethanol, phenylacetaldehyde, and isopentyl acetate, all of which impart floral aromas.

Therefore, in some tea-producing regions of China, autumn teas exhibit excellent floral aromas, commonly referred to as “autumn fragrance.”

Regardless of whether in high mountains or plains, the aroma of tea during dry seasons is higher than during rainy seasons. During high-humidity and rainy seasons, tea trees grow rapidly, and the Metabolism of the acetate synthesis pathway becomes more active, relatively weakening the leucine pathway outside the chloroplast membrane, which is unfavorable for the formation and accumulation of aroma substances.

III. The Impact of Tea Garden Soil Characteristics on Aroma

The soil conditions have a significant impact on the aroma and quality of oolong teas. For example, in the hometown of the famous tea Tieguanyin from Anxi—areas like Xiping, Changqing, Gande, and Xianghua—the soil layers are deep, mostly mountainous brown soils, with sandy loam textures. The topsoil has a higher organic matter content and abundant mineral nutrients, with pH values ranging from 4.5 to 6.5. These conditions are not only suitable for the growth of tea trees but also result in exceptionally high-quality processed teas.

In the production areas of Wuyi rock teas, the soil is predominantly dark-colored and derived from weathered rocks, with deep layers rich in organic matter and various mineral elements. This soil plays a crucial role in the formation of the excellent quality of rock teas. However, there are still significant differences in the soil across the entire Wuyi Mountain tea gardens, leading to variations in tea quality classified as Zhengyan (the best), Banyan (second best), Zhou tea (third), and Waishan tea (the worst). This clearly demonstrates the significant impact of tea garden soil on tea quality.