Temporal fluctuation in nutrient availability generally promotes the growth of exotic plant species and has been recognized as an important driver of exotic plant invasions. However, little is known about how the impact of fluctuating nutrients on exotic species depends on the availability of other resources, although most ecosystems are experiencing dramatic variations in a wide variety of resources due to global change and human disturbance. Here, we explored how water availability mediates the effect of nutrient pulses on the growth of six exotic and six native plant species. We subjected individual plants of exotic and native species to well-watered or water-stressed conditions. For each level of water availability, we added equivalent amounts of nutrients at a constant rate, as a single large pulse or in multiple small pulses. Under well-watered conditions, nutrient pulses promoted exotic plant growth relative to nutrients supplied constantly, while they had no significant effect on natives. In contrast, under water-stressed conditions, water deficiency inhibited the growth of all exotic and native species. More importantly, nutrient pulses did not increase plant growth relative to nutrients supplied constantly and these phenomena were observed for both exotic and native species under water-stressed conditions. Taken together, our study shows that the impact of fluctuating nutrient availability on the growth of exotic plant species strongly depends on the variation of other resources and that the positive effect of nutrient pulses under well-watered conditions disappears under water-stressed conditions. Our findings suggest that variation of multiple resources may have complex feedback to exotic plant invasions, and therefore it is critical to encompass multiple resources for the evaluation of fluctuating resource availability effects on exotic plant species. This will allow us to project the invasive trajectory of exotic plant species more accurately under future global change and human disturbance.

We collected this dataset from a greenhouse pot experiment. To examine whether and how water availability could mediate the effect of nutrient pulses on the growth of native and exotic species, we carried out a pot experiment in the greenhouse (50-70% relative humidity, 16/8 hr light/dark cycle, 26°Cday / 18°C night) at Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China. We established a 2*3*12 full factorial experiment incorporating two levels of water availability (well-watered or water-stressed), three levels of nutrient enrichment (a single large pulse, multiple small pulses or nutrients supplied at constant rate), and 12 plant species (six natives and six exotics). There were five replicates for each combination, resulting in 360 pots in total. After 10 weeks of nutrient and water treatments, we harvested the aboveground and belowground biomasses of each plant and stored them in labeled paper bags separately. Both the aboveground and belowground biomasses were then oven-dried at 80 °C for 72 h and weighed.