Rhizosphere effects of overstory tree and understory shrub species in central subtropical plantations'A case study at Qianyanzhou, Taihe, Jiangxi, China

Abstract

Aims The objective was to explore the differences in rhizosphere effect among different plants in plantation and provide important theoretical basis for understory vegetation management in plantation ecosystem. Methods We collected bulk and rhizosphere soils of overstory trees and understory shrubs (Loropetalum chinense, Adinandra millettii and Eurya muricata) in Cunninghamia lanceolata, Pinus massoniana and Pinus elliottii plantations which were planted in about 1985, at Qianyanzhou Ecological Research Station, Taihe, Jiangxi, to investigate soil pH value, soil nitrogen, carbon and phosphorus content and to access their rhizosphere effects. Important findings (1) Most of the chemical properties of rhizosphere soil and bulk soil were significantly different for overstory tree species (p < 0.05), while the differences between bulk soil and rhizosphere soil of understory shrubs were related to understory shrub species. For example, most of the properties were significantly different between bulk and rhizosphere soils for L. chinense, but not for E. muricata. (2) Rhizosphere effects among shrub species were significantly different except for those of nitrate nitrogen (NO3--N). Specifically, the rhizosphere effects of pH, ammonium nitrogen (NH4+-N), dissolved organic carbon (DOC), total nitrogen (TN), total carbon (TC), carbon-nitrogen ratio (C/N), available phosphorus (AP) and total phosphorus (TP) of L. chinense were significantly higher than those of E. muricata. And the rhizosphere effects of TN, TC, C/N and AP of L. chinense were significantly higher than those of A. millettii. No significant differences were found between the rhizosphere effects of A. millettii and those of E. muricata. (3) The rhizosphere effects of C. lanceolata were significantly higher than those of the three understory shrubs. But no significant difference was found between P. massoniana or P. elliottii and L. chinense. While the rhizosphere effects of P. massoniana were significantly higher than those of A. millettii and E. Muricata, and the rhizosphere effects of P. elliottii were significantly higher than those of E. muricata. The results showed that the rhizosphere effects of overstory tree species were higher than those of understory shrubs (especially for E. muricata), indicating overstory tree species have stronger ability to obtain nutrients. But the differences in rhizoshpere effects between overstory trees and understory shrubs varied between shrub species and forest types. Therefore, this study suggested that understory shrub species should be considered according to forest stand type in plantation management in order to provide higher productive and ecological value.