DOI: 10.5061/dryad.cc2fqz690
title: Effects of nutrient pulses on exotic species shift from positive to neutral with decreasing water availability

description: 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.
description: 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.