Evaluating the productivity of ancient Pu'er tea trees (Camellia sinensis var. assamica): a multivariate modeling...

The demand for productive economic plant resources is increasing with the continued growth of the human population. Ancient Pu'er tea trees [Camellia sinensis var. assamica (J. W. Mast.) Kitam.] are an important ecological resource with high economic value and large interests. The study intends to explore and evaluate critical drivers affecting the species' productivity, then builds formulas and indexes to make predicting the productivity of such valuable plant resources possible and applicable.

Our analysis identified the ideal values of the seven most important environmental variables and their relative contribution (shown in parentheses) to the distribution of ancient Pu'er tea trees: annual precipitation, ca. 1245 mm (28.73%); min temperature of coldest month, ca. 4.2 °C (18.25%); precipitation of driest quarter, ca. 47.5 mm (14.45%); isothermality, 49.9% to 50.4% (14.11%); precipitation seasonality, ca. 89.2 (6.77%); temperature seasonality, ca. 391 (4.46%); and solar radiation, 12,250 to 13,250 kJ m^-2 day^-1 (3.28%). Productivity was indicated by the total value (viz. fresh leaf harvested multiplied by unit price) of each tree. Environmental suitability, tree growth, and management positively affected productivity; regression weights were 0.325, 0.982, and 0.075, respectively. The degree of productivity was classified as follows: > 0.8, "highly productive"; 0.5-0.8, "productive"; 0.3-0.5, "poorly productive"; and < 0.3, "unproductive". Overall, 53% of the samples were categorized as "poorly productive" or "unproductive"; thus, the management of these regions require attention.

This model improves the accuracy of the predictions of ancient Pu'er tea tree productivity and will aid future analyses of distribution shifts under climate change, as well as the identification of areas suitable for Pu'er tea tree plantations. Our modeling framework provides insights that facilitate the interpretation of abstract concepts and could be applied to other economically valuable plant resources.