Fine Root Decomposition Of Cunninghamia Lanceolata And Schima Superba In Natural Evergreen Broad-leaved Forest In Dagangshan

Fine root is the main part of underground litter, its death and decomposition is an important source of soil C and nutrients, so study the fine root decomposition is beneficial to understand nutrient cycling and energy flow in forest ecosystem. At present, the study of fine root is focusing on the plantation, and mostly located in the tropical and temperate forests, while fewer study of fine root decomposition is carried out in the natural evergreen broad-leaved forest in subtropical regions. Therefore, in this paper, we selected young tree of Cunninghamia lanceolata and Schima superba in natural evergreen broad-leaved forest in Dagangshan as the study objects. According to the root order, the roots were divided into four orders, used litterbags technique to research the decomposition dynamic and nutrient releasing rule in each root order of fine root of Cunninghamia lanceolata and Schima superba under different altitude. The main results were found as follows:(1) Fine root decomposition was fast in the early stage but slow in the later stage. In the early90d of decomposition of Cunninghamia lanceolata and Schima superba, fine root had the biggest mass loss and fastest decomposition. After90d decomposition, the rate had slow down. Fine root decomposition is affected by the natural environment, the decomposition rate of Cunninghamia lanceolata and Schima superba was faster at an altitude of300m than the decomposition rate at an altitude of700m.(4) Fine root decomposition of four root orders with Cunninghamia lanceolata and Schima superba showed that, the decomposition of first order of fine root was slowest, then followed by third and fourth order, the fastest was the fifth order of fine root.(5) Study the factor of fine root decomposition showed that, root order had essential effects on the root decomposition. Meanwhile, the material quality of fine root would affect its decomposition rate. The fine root decomposition rate of Cunninghamia lanceolata was significant positively correlated with fine root initial carbon and nitrogen content, significant negatively correlated with fine root initial phosphorus content. The fine root decomposition rate of Schima superba was significant positively correlated with fine root initial carbon, phosphorus content and C/N, significant negatively correlated with fine root initial nitrogen content and N/P. In addition, soil temperature and moisture also affect the decomposition rate of fine roots, in the decomposition period of0-240d, the fine roots decomposition rate of Cunninghamia lanceolata and Schima superba were positively correlated with soil temperature and soil moisture.(6) In the study period, each chemical component content in fine roots was dynamic changed with its decomposition. The carbon and phosphorus content were reduced in four orders of fine root with Cunninghamia lanceolata and Schima superba at different altitudes, within the early decomposition stage (0-90d), the carbon and phosphorus content were significantly decreased, then the rate slowed. But during the decomposition, the nitrogen content was increased. The lignin content was fluctuated during the decomposition stage of0-150d, then decreased significantly.