Effects of precipitation exclusion on fine-root biomass and functional traits of Cunninghamia lanceolata seedlings.

Abstract

A precipitation exclusion experiment was set up in Cunninghamia lanceolata seedling plots in Chenda State-Owned Forest Farm, Sanming, Fujian Province, which included 50% precipi-tation reduction and ambient precipitation (control). Using soil coring and in-growth core me-thods, changes in fine-root functional traits of C. lanceolata seedlings, including fine-root biomass, morphology, stoichiometry, specific root respiration, and nonstructural carbohydrates, were exa-mined after 1 year's precipitation exclusion. The results showed that precipitation exclusion significantly decreased biomass of 0-1 mm diameter roots but had no effect on 1-2 mm diameter roots. However, adaptive morphological changes occurred in the precipitation exclusion treatment. The specific root length (SRL) of the 0-1 and 1-2 mm diameter roots increased by 21.1% and 30.5%, respectively, and root tissue density (RTD) significantly decreased and specific root surface area (SRA) significantly increased in the 0-1 mm diameter roots. Precipitation exclusion led to increase in nitrogen concentration in fine roots, but the absorption capacity for phosphorus was impeded, resulting in increased root N:P, which implied a nutritional imbalance in fine roots. Precipitation exclusion did not significantly change fine root specific respiration rate and nonstructural carbohydrate (NSC) content. However, the soluble sugar content and the ratio of soluble sugar to starch were significantly decreased, and the starch content was increased by 33.3% in the 1-2 mm diameter roots, indicating an adaptation response of C. lanceolata seedlings to reduced precipitation by increasing the storage of nonstructural carbohydrate in fine roots.