Diversity, distance and density impact seedling fitness

Authors: Svejcar, Lauren; HOVANES, KATHERINE - University Of Arizona; CHACON LABELLA, JULIA - University Of Arizona; GORNISH, ELISE - University Of Arizona; Davies, Kirk; MARTYN, TRACE - University Of Arizona

Submitted to: Ecological Society of America Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 5/2/2022
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Background/Question/Methods Dryland restoration through seed-based restoration practices is a challenge globally. Seed-based approaches commonly follow agricultural models of linear or haphazard spatial plantings. However, natural vegetation patterns infrequently follow linear or random spatial arrangements due to abiotic and biotic drivers of seedling mortality. As such, a deeper understanding of seedling mortality drivers is needed to inform seed-based restoration plantings. We conducted a greenhouse study utilizing varying densities, distances and diversity levels with three key C3 perennial species in Sonoran Desert restoration efforts: Trichachne californica, Senna covesii, and Aristida purpurea (using Aristida purpurea and Senna covesii as focal species of interest). For each focal species, 28 unique treatment combinations were planted (2 distances x 2 densities x 7 diversity combinations = 28 total treatments) with five replicates of each. The plants grew for 3 months and then we collected plant functional traits (height, Specific Leaf Area, Leaf Dry Matter Content, and biomass) on all focal individuals. We ran fitness models to quantify interactions between the focal individual and the neighboring individuals using each functional trait as a response variable. We compared models of varying complication from null to a full model with distance treatments and density of species-specific neighboring individuals. Results/Conclusions We found that for Aristida purpurea, the best fitting models tended to include only the total number of neighbors (no neighbor identity or distance treatment). This could indicate that just the density of surrounding neighbors is a strong influence for establishment of this species. For Senna covesii, we found that the best fitting models tended to be those that just included distance (not neighbor density or identity). From this result we concluded that Senna covesii performs best when planted alone. The results of our study can help inform optimal seeding combinations in the field based on theoretical understanding of species interactions and may be used to inform novel strategies for ecosystem restoration, such as seed enhancement technologies.