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Effects of Eupatorium Adenophorum Invasion on Soil Characteristics

Author: LiuChao
Tutor: FengYuLong
School: Hebei University
Course: Botany
Keywords: biological invasion Eupatorium Adenophorum Sprengel soil enzyme activities soil fertility soil physical and chemical factors soil substrate-induced respiration
CLC: S451
Type: Master's thesis
Year: 2007
Downloads: 50
Quote: 1
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Abstract

Biological invasion is serious environmental and social problems. It has severe impact on biodiversity, and on social and economic development. The impact of exotic invasive plants on soil ecosystems has become one of the hot fields in invasion ecology. Eupatorium adenophorum is one of the most noxious invasive weeds in China. To explore the impacts of this weed invasion on soil ecosystem, we measured physical and chemical factors, enzyme activity, and substrate-induced respiration of 0-30 cm depth soils from a more than 10 years old invaded grassland of E. adenophorum, a secondary grassland (abandoned maize field in November of 2001), a primary grassland of Themeda yunnanensis and a two years old artificial grassland of Setaria sphacelata. The effects of soil microbial community on plant growth were also studied. The main results were as follows:1. With the increase of soil depth, the contents of organic matter, total N, total P, total Ca, hydrolyzable N, active P, active K, and pH value decreased, whereas total K content increased. The contents of organic matter, total N and hydrolyzable N in the soil of E. adenophorum community were much higher in rainy season than in dry season. The seasonal change of soil fertility for S. sphacelata community was similar to that for E. adenophorum community. However the organic matter contents were higher in dry season than in rainy season for the soils of the secondary grassland and T. yunnanensis community. The contents of organic matter, total N, total P, total Ca, hydrolyzable N were significantly higher in the soil of E. adenophorum community than in the soils of the other three communities. The higher soil fertility under E. adenophorum community maybe contributes to its invasion.2. With the increase of soil depth, the activities of polyphenol oxidase, alkaline phosphatase and urase decreased. For the four studied communities, the activitiy of peroxidase was higher in dry season than in rainy season, while the activities of alkaline phosphatase and acid phosphatase were higher in rainy season than in dry season. For E. adenophorum community, the activity of polyphenol oxidase was higher in rainy season than in dry season, while the difference between the two seasons in urase activity was not significant. The activities of alkaline phosphatase and urase were higher in the soil of E. adenophorum community than in the soils of other three studied communities.3.The substrate-induced respiration (SIR) decreased with the increase of soil depth. Lignin-, D-glucose-, L-gsparagine-, and glycerol-induced respiration were higher for the soil of E. adenophorum community than for the soils of other studied communities. The results indicated that soil microbial community had been changed by the invasion of E. adenophorum.4. There were extremely significantly positive correlations between the activities of alkaline phosphatase and urase and the contents of organic matter, total N, total P, hydrolyzable N, active P, and active K. The SIR with fumaric acid, lignin, D-glucose, glycerol as substrate respectively was also significantly correlated with the above variables. The activities of soil enzymes, soil nutrition contents, and soil microbial community were closely related to one another. The activities of alkaline phosphatase and urase can be used to describe the level of soil fertility.5. Soil microbial community affected plant growth significantly. The soil microbe under E. adenophorum community promoted seedling growth of E. adenophorum and other four studied species. The soil microbe under Digitaria sanguinalis community promoted seedling growth of E. adenophorum. The feedback between aboveground plant and soil microbial community maybe influence the competition between E. adenophorum and native species.In summary, the invasion of E. adenophorum increased soil fertility through increasing soil nutrient contents and soil enzyme activities, and through changing soil microbial community, which might in turn promote its further invasion. We hypothesized that the positive feedback between E. adenophorum and soil is one of the mechanisms underlying its invasion.

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