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Dryad

The dominant plant species Solidago canadensis structures multiple trophic levels in an old-field ecosystem

Cite this dataset

Eckberg, Julia et al. (2022). The dominant plant species Solidago canadensis structures multiple trophic levels in an old-field ecosystem [Dataset]. Dryad. https://doi.org/10.5061/dryad.2ngf1vhsn

Abstract

Dominant plant species are locally abundant and have large impacts on ecological communities via a variety of mechanisms. However, few studies have evaluated the influence of a dominant plant species both within and among trophic levels and on key ecosystem functions such as productivity. In this study, we evaluated the effect of the dominant plant species Solidago canadensis on plant and arthropod communities in an old-field ecosystem in southeastern Michigan. We found that S. canadensis negatively correlated with the richness and combined biomass of all other plant species in the community, likely by reducing light availability. In turn, less biomass of all other plant species led to lower arthropod abundance. Specifically, detritivore and predator arthropod abundance was lower with less biomass of all plant species excluding S. canadensis, but herbivore and omnivore abundance was unaffected. Our results highlight the significant role of dominant plants in determining plant diversity and ecosystem function, and further suggest that the effect of a dominant plant species on a community is observed at higher trophic levels.

Methods

Site description

We conducted this study in August 2021 in an old field at Matthaei Botanical Garden in Ann Arbor, Michigan (42.30° N, 83.66° W). Local average monthly temperature ranges from -4.6 ℃ in January to 22.6 ℃ in July (ClimateData 2021). Average annual precipitation is 954 mm (U.S. Climate 2021). The old field we worked in is typically mowed annually and burned semi-annually, maintaining it in an early-successional state. The most abundant plant species at the site is S. canadensis, a perennial, clonal herbaceous species common in the northeastern and midwestern United States. At this site, S. canadensis constitutes, on average, ~ 50% of above-ground plant biomass (Eckberg, unpublished data). Other than S. canadensis, the four most abundant plant species include Monarda fistulosa, Vitus riparia, Vicia tetrasperma, and Toxicodendron rydbergii (Table S1). 

Solidago canadensis impact on plant community

At the site, we placed 24 1-m2 quadrats in a grid. Quadrats were at least six meters apart, and we mowed paths among quadrats approximately monthly. To evaluate the effect of S. canadensis on light availability, we estimated light intensity above the tallest plants in each quadrat and 50 cm above the ground prior to removing all S. canadensis stems from each quadrat. We made five light intensity measurements above the canopy created by S. canadensis and five below using the iOS app Lux Light Meter Pro version 2.1.1 (Polyanskaya 2021). Then, for each quadrat, we calculated the average light intensity above and below the canopy. We calculated light availability as the proportion of light above the canopy that penetrated to 50 cm above the soil.

To evaluate the effect of S. canadensis on the plant community, we first estimated biomass of S. canadensis in each quadrat by clipping all of the S. canadensis stems at ground level. We then dried the S. canadensis stems in each 1-m2 quadrat for 72 hours at 60℃ and weighed them. After the S. canadensis stems were removed from each quadrat we estimated plant species richness in each 1-m2 quadrat. We then clipped, dried, and weighed those other plant species from each 1-m2 quadrat as described above.

Solidago canadensis impact on other trophic groups

To evaluate the effect of S. canadensis on the ground-foraging arthropod community, we buried one 50mL centrifuge tube pitfall trap flush with the soil surface in the center of each quadrat after S. canadensis was removed, but before we removed other plants. We partially filled each pitfall trap with a mixture of water and unscented dish soap. We left traps in place for 72 hours and immediately counted and stored arthropods in ethanol upon removing pitfall traps. Using a dissecting microscope in the lab, we identified arthropods to the lowest possible taxonomic level and categorized them by trophic level (herbivore, predator, detritivore, omnivore, parasite, or pollinator) using published sources and online guides. The most common arthropod families identified were the Formicidae (ants) and Armadillidiidae (pillbugs). We collected arthropods once to limit damage to the plant community caused by arthropod sampling. Additionally, sampling arthropods multiple times may have negatively affected arthropod populations and impeded our ability to study how arthropods affect, and are affected by, the plant community in this and future studies.

Funding

University of Michigan–Ann Arbor