Feedback regulation of soil within invaded habitats on the interspecific relationship between Alternanthera philoxeroides and Digitaria sanguinalis

【Objective】 This study aimed to investigate the feedback regulation of soil legacy effects within Alternanthera philoxeroides-invaded habitats on itself and the native coexisting species Digitaria sanguinalis， so as to provide theoretical basis for predicting the invasion trends of Alternanthera philoxeroides under environmental changes and implementing biological substitution. 【Method】 Soil samples were collected from habitats seriously invaded by Alternanthera philoxeroides in four provinces （regions） of China， including Jiangxi， Hunan， Guangxi， and Guangdong. The three-factors potted experiment was conducted， which including the soil treatment （control treatment， feedback treatment （adding soil within invaded habitats）， planting method （mono and mixed culture）， and species trait （Digitaria sanguinalis， Alternanthera philoxeroides）， to examine the effects of soil within invaded habitats on the morphological trait， biomass， nutrition， and photosynthetic fluorescence of Alternanthera philoxeroides and Digitaria sanguinalis. 【Result】 The maximum stem length， content of total carbon and total nitrogen in Digitaria sanguinalis were significantly （P<0.05， the same below） or extremely significantly （P<0.01， the same below） higher than those in Alternanthera philoxeroides， while the root area， total biomass， shoot biomass， root biomass， root-shoot ratio， minimum fluorescence （F₀）， maximum fluorescence （F_m）， and photochemical quenching coefficient （qP-Lss） of Alternanthera philoxeroides were significantly or extremely significantly higher than those of Digitaria sanguinalis. Compared with the control treatment， feedback treatment led to extremely significant decrease in the maximum stem length， root length， root area， and leaf area of the entire stu-died plants， and caused a higher decrease in the root length of Alternanthera philoxeroides than that of Digitaria sanguinalis in mixed cultures. Feedback treatment led to significant or extremely significant decrease in the total biomass， shoot biomass， and root biomass of the entire studied plants， caused an extremely significant decrease of 48.28% in the root-shoot ratio of Digitaria sanguinalis and an extremely significant increase of 20.10% in that of Alternanthera philoxeroides. Feedback treatment led to an extremely significant increase of 13.79% and 148.00% in the total carbon of Digitaria sanguinalis and Alternanthera philoxeroides respectively. Feedback treatment led to significant increase in the maximum light quantum efficiency （F_v/F_m） of the entire studied plants and the steady-state light actual quantum efficiency （QY-Lss） of Digitaria sanguinalis， while caused significant decrease of 45.40% and 32.18% in F₀ and F_m of Alternanthera philoxeroides in mixed cultures respectively. 【Conclusion】 Soil within Alternanthera philoxeroides-invaded habitats on large scale weakens the morphology and biomass of itself and Digitaria sanguinalis， and interspecific competition intensifies the negative feedback of soil within invaded-habitats on photosynthetic fluorescence of Alternanthera philoxeroides. Thus， when the native species Digitaria sanguinalis exists in communities， soil within invaded habitats may not be conducive to the secondary invasion of Alternanthera philoxeroides， and the artificial planting of Digitaria sanguinalis in invasion areas can be considered as a method for substitutive control of A. philoxeroides.