PS 42-43 - The importance of priority effects and nutrient levels for semi-arid grassland community dynamics

Wednesday, August 17, 2022

5:00 PM – 6:30 PM EDT

Located in: ESA Exhibit Hall

Presenting Author(s)

Nathaniel Dungey

Graduate Student
Thompson Rivers University
Kamloops, British Columbia, Canada

Coauthor(s)

MA

Morodoluwa Akin-Fajiye

Thompson Rivers University, Canada
LF

Lauchlan Fraser

Thompson Rivers University, Canada

Background/Question/Methods

Background: The order of arrival of plant species into a community can influence the trajectory of community development and community structure. Priority effects occur when early arriving plants influence the establishment of later arriving plants. Soil nutrient levels can alter the strength of priority effects. Fast growing early arriving species are expected to quickly build biomass, when resources such as space and nutrients are plenty, while late arriving species are expected to be competitively dominant when resources are lower.

Methods: We used a greenhouse study to test a four week priority effect of early and late successional species of grasses and forbs native to interior British Columbia. We had three priority treatments: all species simultaneously (ESLS), early before late arriving species (ES), and vice versa (LS). We manipulated fertilizer levels using low (4 g/m2) and high fertilizer (10 g/m2). Each treatment combination was replicated six times for a total of 96 pots. The experiment is expected to run for 16 weeks, but here we report preliminary results on cover, and maximum height (top 3 plants) per pot after 8 weeks.

Results/Conclusions

Results: In a two-way Analysis of Variance, we found significant preliminary effects of order of arrival of ES and LS plants on grass and forb cover and maximum heights, but no significant effects of fertilizer levels. Grass cover was 13.4% and 8.2% higher when ES were planted first, compared to ESLS and LS first respectively (F2, 61 = 12.84, p = < 0.001). Forb cover was 7.2% higher when LS were planted first versus ES first, and 2.3% higher versus ESLS (F2, 66 = 3.55, p = 0.034). Average grass height in ESLS pots measured 6.2cm taller than ES first, and 6cm taller than LS first (F2, 219.35 = 18.03, p < 0.001). Average forb height in ESLS pots was 1.97cm taller than LS first, and 3.57cm taller than ES first. In LS first pots, we observed a 1.6cm taller average forb height over ES first (F2, 215.54 = 25.35, p < 0.001). Results are showing early arriving species to have a stronger inhibition effect than late arriving species.

Conclusion: Preliminary results suggest plant arrival order can be more influential than nutrient levels on success of specific functional groups and community composition.