Researcher effects on the biological structure and edaphic conditions of field sites and implications for management
Authors/Creators
- 1. University of Alabama, Tuscaloosa
- 2. San Diego State University
- 3. Southern California Coastal Water Resource Project*
- 4. Texas Tech University
- 5. University of Alabamac*
Description
Field studies are necessary for understanding natural processes, but they can disturb the environment. Despite researchers acknowledging these effects, no studies have empirically tested the direct (e.g., harvesting plants) and indirect effects (i.e., trampling) of researcher activities on biological structure and edaphic conditions. We leveraged field studies in Alabama and California to monitor the recovery of tidal marshes following research activities. Researcher effects on animals, plants, and sediment conditions remained prevalent almost one year after the disturbance ended. For instance, trampled plots had 14-97% lower plant cover than undisturbed plots after >10 months of recovery. Researcher effects also impacted plant composition, leading to increased subordinate species abundance. We encourage field researchers to adopt strategies that reduce their scientific footprints, including reducing field visits, limiting field team size, and considering ways to limit potential environmental impacts during study design.
Other
Funding provided by: University of Alabama
Crossref Funder Registry ID: https://ror.org/03xrrjk67
Award Number:
Methods
Experimental design
The study included four treatments: High Crab, Low Crab, Trampled, and Control (n = 5 treatment-1) at constructed and natural marshes in both regions. The High Crab and Low Crab treatments were established in the footprints of the high-crab density and low-crab density cages, respectively, that were part of the original burrowing crab manipulative studies conducted at each site (Appendix S1). Thus, these plots had their crab communities modified, aboveground biomass harvested, rhizomes severed, and sediments cored as part of prior experiments (Appendix S1). Trampled plots were established in areas where researchers frequently walked to maintain the original caging studies. Controls were placed in nearby habitat that was previously undisturbed by researcher activities. Plots sizes were 0.7 x 0.7m (length x width) in CA and 0.5 x 0.5m in AL.
Starting in February (AL: 2021; CA: 2019), we monitored crab burrow density, plant cover, and the mean height and stem density (AL: n ≤ 5 stems plot-1; CA: n ≤ 10 stems plot-1) of the dominant plant species (AL: needlerush; CA: Pacific cordgrass) in each marsh every-other month until September (CA) and October (AL). Additionally, in October in AL marshes, we collected one, 10-cm-deep sediment core using a Russian Peat corer (i.d. = 5cm) that we sub-sectioned in the field at 2.5cm intervals. Subsections were oven-dried at 60°C to a constant mass to obtain bulk density, and once dried, samples were ground with a mortar and pestle before being ashed in a muffle furnace (6h at 550°C) to estimate sediment organic matter (SOM) via loss on ignition. We also collected one, 10-cm-deep sediment core using a t-corer (i.d. = 7.9cm) that we sub-sectioned in the field at 5 cm intervals to assess belowground biomass at the AL sites. Subsections were rinsed to remove sediment attached to belowground biomass, which was then dried at 60°C to a constant mass (Conner & Cherry 2015).
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