Do plant traits and preexisting ecosystem attributes predict the severity of invader impacts on nitrogen cycling?

Background/Question/Methods

Plant invasions can dramatically alter ecosystem processes such as nitrogen (N) cycling. However, the results of an invasion event are often contingent upon characteristics of the invading species and the invaded ecosystem. Whether this variation in the biogeochemical consequences of invasion is predictable based on the N cycling attributes of the existing community and the nutrient demands of the invader remains unknown. To address this question, we assessed whether (a) invader traits, (b) the difference between invader and native plant community traits, and/or (c) N cycling attributes of reference areas explain variation the magnitude of an invader’s impact on N cycling. In line with the empty-niche and novel traits hypotheses, we expected that invaders would have greater impacts in areas where there are large differences between the traits of the reference plant community and the invasive species or where reference N cycling attributes differ greatly from the invader’s trait-based resource acquisition strategy.

Results/Conclusions

Based on 118 observations collected in the literature that describe the impact of over 40 invasive plant species on N cycling, we found a negative relationship between invasive species’ foliar C:N and the magnitude of the invasion’s impact on net N mineralization rates.  We also found positive relationships between the native plant community’s foliar and litter C:N and the magnitude of the invasion’s impact on soil inorganic N concentrations. These results suggest that invader traits may be useful for predicting changes in N cycling after an invasion event. Conditions of the initial system, particularly native plant community foliar and litter C:N, may also mediate invader impacts. Furthering this research will contribute to our ability to predict and plan for the impact of plant invasions on nutrient cycling in many contexts.