Effects of Soil Warming and Precipitation Exclusion on the Morphological and Stoichiometric Traits of Fine Roots of Different Orders in Cunninghamia lanceolata

In order to understand the responses of fine root morphological and stoichiometric traits to the interaction of warming and drought, the two-factor experiment of soil warming (no warming and 5℃ warming) and precipitation exclusion (no precipitation exclusion and 50% precipitation exclusion) with Cunninghamia lanceolata seedlings as the materials was carried out in the National Field Scientific Observation and Research Station of Forest Ecosystem in Sanming of Fujian. There were four treatments, namely the control group (CT), soil warming (W), precipitation exclusion (P), and soil warming+precipitation exclusion (WP). The morphological and stoichiometric traits of fine roots in the first three orders were measured after one year of treatment. The results showed that there was no significant interaction between temperature enhancement and precipitation exclusion on the morphological traits of fine roots. The main effect of temperature enhancement had no significant effect on the diameter of fine roots (RD), but significantly reduced the specific root length of fine roots (SRL, especially the first-order root) and the specific surface area of fine roots (SRA), while significantly increased the fine root tissue density (RTD). The main effect of precipitation exclusion only significantly reduced the specific root length (SRL), but had no significant effect on the root diameter (RD), specific surface area (SRA) and root tissue density (RTD). The effect of temperature enhancement, precipitation exclusion and their interactions had significant effects on the contents of carbon and nitrogen in fine roots and the carbon-nitrogen ratio. Compared with CT, the P treatment resulted in a significant decrease in carbon content and carbon-nitrogen ratio of fine roots in first and second order. The nitrogen content of fine roots in each order increased significantly under W and WP treatments, while the carbon-nitrogen ratio of fine roots decreased significantly. Under the effect of temperature enhancement and precipitation exclusion, the fine roots of Cunninghamia lanceolata may enhance the physiological absorption ability (high content of nitrogen), but weaken the ability to explore nutrients (low SRL and SRA). The results of this study were helpful to further understand the ecological strategies of the fine roots of Cunninghamia lanceolata to cope with the environmental stress in the subtropical regions in the context of global climate change.