Positive feedbacks to growth of an invasive grass through alteration of nitrogen cycling

Abstract

Understanding the mechanisms by which invasive plants maintain dominance is essential to achieving long-term restoration goals. While many reports have suggested invasive plants alter resource availability, experimental tests of feedbacks between invasive plants and soil resources are lacking. We used field observations and experimental manipulations to test if the invasive grass Microstegium vimineum both causes and benefits from altered soil nitrogen (N) cycling. To quantify M. vimineum effects on N dynamics, we compared inorganic N pools and nitrification rates in 20 naturally invaded and uninvaded plots across a range of mixed hardwood forests, and in experimentally invaded and uninvaded common garden plots. Potential nitrification rates were 142 and 63 % greater in invaded than uninvaded plots in forest and common garden soils, respectively. As a result, soil nitrate was the dominant form of inorganic N during peak M. vimineum productivity in both studies. To determine the response of M. vimineum to altered nitrogen availability, we manipulated the dominant N form (nitrate or ammonium) in greenhouse pots containing M. vimineum alone, M. vimineum with native species, and native species alone. M. vimineum productivity was highest in monocultures receiving nitrate; in contrast, uninvaded native communities showed no response to N form. Notably, the positive response of M. vimineum to nitrate was not apparent when grown in competition with natives, suggesting an invader density threshold is required before positive feedbacks occur. Collectively, our results demonstrate that persistence of invasive plants can be promoted by positive feedbacks with soil resources but that the magnitude of feedbacks may depend on interspecific interactions.

Soil Degradation and the Decline of Available Nitrogen and Phosphorus in Soils of the Main Forest Types in the Qinling Mountains of China

“…Tree species can have a strong influence on soil properties [22]. Different vegetation types can have varying influence on the rate of soil N and P input, and these can affect the soil nutrient accumulation and loss [23,24].…”

Negative competitive effects of invasive plants change with time since invasion

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The Effects of Frangula Alnus miller on HEK Cells in Cell culture

“…The results of studies on the leaves of this plant have shown that F. alnus leaf litter has the capacity to alter soil properties and microbial function by stimulating N mineralization [12]- [16]. Bark of Frangula alnus Mill also referred as Frangulae cortex is widely used as laxative and can be found as component of herbal laxative preparations Laxative property of F. alnus bark has been attributed to the presence of anthraquinone glycoside derivatives, glucofrangulins and frangulins [17].…”