Changes of Soil Nutrient, Soil Enzymes Activities and Microbial Communities in Rhizosphere Soil of Chenopodium Ambrosioides L. at Different Development Phases
A pot experiment was used to study the effects of Chenopodium ambrosioides L. on soil ecosystem, through the variations of soil nutrient, soil extracellular enzymes activities and microbial communities in rhizosphere soil at its nutrient phase and fruiting stage. The results may help us further understand the invasion mechanism of C. ambrosioides and provide theoretical basis for the prevention and control measures. The results showed that:(1) The invasion of C. ambrosioides had certain effects on soil nutrients. Compared with the control group, except that the content of total K in rhizosphere soil of C. ambrosioides at nutrient phase was increased by 12.26%, the other soil nutrient indexes were decreased in varying degrees. Of which, the content of total K were decreased 3.27% at fruit phase; total organic matter at nutrient phase and fruit phase were decreased by 20.41% and 1.22%, respectively;total nitrogen at nutrient phase and fruit phase were decreased by 27.87%and 16.39%, respectively;total P at nutrient phase and fruit phase were decreased by 29.41% and 14.71%, respectively; available P at nutrient phase and fruit phase were decreased by 49.24%and 34.69%, respectively;available K at nutrient phase and fruit phase were decreased by 76.65%and 57.22%, respectively;(2)The invasion of C. ambrosioides also had influences on the soil extracellular enzymes. Compared with the control group, the activity of soil nitrate reductase at nutrient phase and fruit phase had a significant increase (P<0.05) that were increased by 87.23%and 137.23%respectively;Urease activity at nutrient phase reduced by 45.92%compared with the control group, which was a dramatic drop (P<0.05);The variations of activities of invertase, acid phosphatase and catalase in rhizosphere soil at nutrient phase and fruit phase did not have obvious differences (P>0.05);(3) The soil microbial population was increasing along with the growth of C. ambrosioides, but only the amount of fungi had significant difference with the control group (P<0.05). The amount of fungi at nutrient phase and fruit phase increased by 32.11%and 86.18%respectively;(4) Soil nutrient content, soil enzyme activity and the microbial population at nutrient phase were generally lower compared with the fruit phase. We speculated that at the early growth stage of C .ambrosioides, it inhibited the growth of surrounding plants which needs higher nutrition by reducing the soil nutrient, to improve its competitive advantage. Later at the fruit phase, the root exudates of C. ambrosioides may release into the soil to enhance the amount of soil microbe and activities of soil enzyme, which caused the recovery of rhizosphere soil nutrient and therefore provided favorable conditions for its breeding.
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