The Response of the Annual Rotation Width of Tea Trees to Climate Change in the Brown Mountains of Yunnan Province

Yunnan is located in the southwestern part of China, with rich tea tree germplasm resources and diversified geomorphological and climatic features, which help us to carry out research related to tea tree chronology and provide scientific and effective support information for enriching the database of tree rings in western Yunnan. This study took the Brown Mountain tea tree in Xishuangbanna as the research object, collected tea tree sample cores through tree growth cone sampling, measured the width of the annual rings, cross-dated them, and established a chronology of the width of the annual rings of the tea tree. The R language was used to analyze the response function of the tea tree’s annual ring chronology with the climatic factors of the study site, discussed the relationship between the radial growth of the tea tree in subtropical regions and climatic factors, and determined the main factors that affected the radial growth of the tea tree. The results of the study showed that the chronology of the tea tree’s whorl width spanned 70 years (1954–2023), with an average annual growth rate of 1.283 mm/year; the average sensitivity was 0.514, which indicated that the chronology contained richer climatic information. The representativeness of the sample group of the whorl width index (EPS) was 0.716, indicating that the consistency of the growth inter-annual variations was better among the different trees. The radial growth was correlated with climatic factors such as temperature and moisture; the radial growth of the tea tree was usually more sensitive to moisture availability, limited by hydrological and climatic factors throughout the rainy season of the year, and positively correlated with the temperature in summer and autumn. In terms of the stability of the radial growth of the tea tree in relation to the climatic response, the growth of the tea tree in the study area may have benefited from future warming of the climate and reduction in precipitation.