Changes in the soil meso- and micro-fauna community under the impacts of exotic Ambrosia artemisiifolia.
Successful establishment of invasive plant species may exert important effects on soil organisms and processes. To investigate the response of the soil meso- and micro-fauna community to Ambrosia artemisiifolia L. invasion and its age of colonization, samples were collected from three different depths in sites with and without the presence of A. artemisiifolia during the period of October, 2009 to July, 2010. Soil fauna were grouped into four categories, that is, Nematoda, Acarina, Collembola and other meso- and micro-fauna species. Seasonal changes in abundance and distribution patterns in relation to soil biochemical properties were then compared and examined. In general, invasion of A. artemisiifolia into native plants significantly increased the soil fauna densities, especially nematodes. Effects of invasion on soil fauna groups were seasonally variable with density peaking in autumn. Short-term invasion of A. artemisiifolia could weaken accumulation of soil fauna groups in the top layer. Vertical distribution of soil meso- and micro-fauna communities changed seasonally with the trend of remarkable upward migrations in the period from winter, summer to spring and autumn, though the degrees of upward migration in the invaded and noninvaded sites differed among the fauna groups. Responses of soil fauna communities may be associated with the enhancement of soil nutrient conditions and microbial activities in the presence of A. artemisiifolia. That is, the colonization of A. artemisiifolia, irrespective of colonization age, may exert an important influence on soil meso- and micro-fauna community over time and thus may be beneficial to its successful colonization.