Fine Root Distribution, Morphology And Adaptation To Competition Of Three Main Dominated Broad-leaved Species In A Secondary Subtropical Forest

Competition is common in nature. Generally, competition between tree species is divided into two groups:aboveground competition for light and belowground competition for soil and water resources. Environment in which trees grow is changed because of competition, while fine root is greatly vulnerable to environment change, which is mainly represented in morphology, architecture and distribution.Alniphyllum fortuneiMakino, Liquidanbar acakycina and Cyclobala-nopsis glauca were objectives of this paper to investigate competition intensity, root distribution and morphology adjusted to competition. The results were found in this paper:(1) the competitive index (CI) of Alniphyllum fortuneiMakino was 1.69, while Liquidanbar acakycina was 0.97 and Cyclobalanopsis glauca was 2.16. Obviously, the order was described as Cyclobalanopsis glauca> Alniphyllum fortuneiMakino>Liquidanbar acakycina.(2) the total biomass of stand fine root of Alniphyllum fortuneiMakino, Liquidanbar acakycina and Cyclobalanopsis glauca in 0-45cm layers were 104.1g·m-2,122.4g·m-2 and 54.4g·m-2 respectively. Fine root biomass of Alniphyllum fortuneiMakino, Liquidanbar acakycina and Cyclobalanopsis glauca were concentrated in top 0-30cm layers, and they decreased with increasing soil depth. Biomass of fine root of Alniphyllum fortuneiMakino and Liquidanbar acakycina were distributed similarly in each layers, but there were some differences between Cyclobalanopsis glauca and Alniphyllum fortuneiMakino, Liquidanbar acakycina in their distribution. In terms of horizontal distribution, there were no significant differences among fine root biomass of Alniphyllum fortuneiMakino, Liquidanbar acakycina and Cyclobalanopsis glauca. (p>0.05) Fine roots of Cyclobalanopsis glauca generally occupied the places nearby trees, while fine roots of Alniphyllum fortuneiMakino and Liquidanbar acakycina were not.(3) Vertical and horizontal distribution of root length density(RLD) and specific root area (SRA)of three tree species was similar to that of fine root biomass. RLD and SRA were significantly decreased with increasing soil depth. RLD and SRA of Alniphyllum fortuneiMakino and Liquidanbar acakycina were similar in different horizontal distance, while RLD and SRA of Cyclobalanopsis glauca were higher closed to tree species.(4) In terms of vertical distribution, specific root length (SRL), specific root area (SRA) and specific root tips (SRT) of Liquidanbar acakycina which decreased significantly with increased soil depth were higher than that of Alniphyllum fortuneiMakino and Cyclobalanopsis glauca in surface 0-15cm. In contrast, SRL, SRA and SRT were increased with increasing soil depth. In terms of horizontal distribution, SRL, SRA and SRT of Liquidanbar acakycina and Cyclobalanopsis glauca were higher than other tree species in different horizontal distances, while those of Alniphyllum fortuneiMakino were not predominant in each soil layers and each horizontal distance.(5) Although Cyclobalanopsis glauca was subjected to strong competition and competitive index was high, its fine roots had great adaptability to changed environment (differential distribution, higher SRL, SRA and SRT), and it can coexist with Liquidanbar acakycina for a long time. On the contrary, suffered from competition from aboveground and belowground, Alniphyllum fortuneiMakino is disadvantageous when competed with Liquidanbar acakycina and Cyclobalanopsis glauca.