Soil properties and fine root morphological traits in relation to soil particle-size fractions in a broad-leaved beech (Fagus orientalis Lipsky) forest

Soil particle-size fractions play an important influence soil physico-chemical properties, microbial biomass processes as well as fine roots morphological traits in beech forest ecosystem. The objectives of study were to determine how soil texture interacts with soil physico-chemical properties and microbial biomass as well as fine roots traits in oriental beech forest in Guilan province, northern Iran. Five subplots of 400 m 2 were randomly selected at a plot of 1 ha. At five different locations, soil samples were collected at depth of 0–20 cm and fine root samples were also taken from beech trees. Results indicated that clay content was positively correlated with carbon, carbon/nitrogen (C/N) ratio, and moisture, but negatively correlated with nitrogen (N) and phosphorous (P). Silt values had significant positive correlation with C/N, and negative correlation with N and P. The microbial biomass carbon/carbon (MBC/C) ratio in soil increased significantly with clay, but microbial biomass nitrogen (MBN) decreased significantly with increasing clay. The MBC/C ratio decreased significantly with sand values in soil at depth 0–20 cm. Results showed that silt value of soil profile was negatively correlated with MBN, but positively with MBN/N ratio. Soil acidic phosphatase concentration was negatively correlated with clay content, but soil alkaline phosphatase was positively correlated with silt. Clay and sand contents were positively correlated with fine root density, fine root biomass, fine root length, and surface root area. Sand content was negatively correlated with fine root volume. The results of research, considering the correlation between soil particle-size fractions and some soil characteristics as well as fine root traits, show that soil texture in oriental beech forest can play an important role in forest stand dynamics. • The clay content was positively correlated with C, C/N ratio, and moisture. • Clay and sand fractions were positively related to some fine root traits. • 3.The MBC/C ratio in soil increased significantly with increasing clay amount.