Topography and disturbance influence trait‐based composition and productivity of adjacent habitats in a coastal system

Abstract

Citation: Brown, J. K., and J. C., Zinnert. 2020. Topography and disturbance influence trait-based composition and productivity of adjacent habitats in a coastal system. Ecosphere 11(5):Abstract. Coastal systems experience frequent disturbance and multiple environmental stressors over short spatial and temporal scales. Investigating functional traits in coastal systems has the potential to inform how variation in disturbance frequency and environmental variables influence differences in trait-based community composition and ecosystem function. Our goals were to (1) quantify trait-based communities on two barrier islands divergent in topography and long-term disturbance response and (2) determine relationships between community trait-based composition and ecosystem productivity. We hypothesized that locations documented with high disturbance would have habitats with similar environmental conditions and trait-based communities, with the opposite relationship in low-disturbance locations. Furthermore, we expected higher productivity and lower site-to-site variation with low disturbance. Functional traits, biomass, and environmental metrics (soil salinity, elevation, and distance to shoreline) were collected and analyzed for two habitat types (dune and swale) on two Virginia barrier islands. Our results show that trait-based community composition differed among habitat types and was related to disturbance. Habitats exhibited more similarity on the high-disturbance island in both trait-based composition and environmental variables. Conversely, the low-disturbance island habitats were more dissimilar. We found the habitat with the lowest disturbance had the highest ecosystem productivity and had trait-based communities indicative of highly competitive environments, while the high-disturbance trait-based communities were influenced by traits that indicate rapid recovery and growth. Site-to-site variation was similar in all dune habitats but differed among inter-island swale habitats that varied in disturbance. These results highlight the importance of incorporating trait-based analyses when approaching questions about community structure and ecosystem productivity in disturbance-mediated habitats, such as coastal systems.

Plant community re-organization and increased productivity due to multi-year nutrient enrichment of a coastal grassland

“…We expected root productivity to increase in response to nutrient enrichment based on previous research indicating that N can have long-lasting effects on belowground biomass in coastal dune systems [ 43 ]. However, given that our study was conducted in a coastal grassland, interactions that influence plant success differ from those dominating in dune plant communities, such as increased competitive interactions and more frequent access to freshwater [ 30 , 35 ]. Similar to our findings, global scale research shows that aboveground and belowground productivity patterns do not always correlate in the presence of nutrient enrichment [ 60 ].…”

“…Nutrient fertilization plots were established on the southern end of the island in a grassland environment composed of perennial graminoid and annual/biennial forb species. The site consists of sandy, well-drained soils and has been described as stable due to presence of a linear dune ridge which provides protection from coastal disturbances [ 35 ].…”

“…Barrier islands occur along 30% of U.S. coastlines with more than half existing on the Atlantic coast where nutrient enrichment is expected to spike [31,32]. Barrier island dynamics including disturbance response and resilience are impacted by feedbacks between dominant physical processes and extant plant communities [30,[33][34][35]. By investigating barrier island response to nutrient enrichments, it is possible to better understand how increased nutrient deposition impacts ecosystems experiencing multiple disturbances over short temporal scales.…”

Comparing In-Person Versus Camera Monitoring of Shorebird Reproductive Success

“…It is low-lying (mean elevation around 1.0 m asl), with a flat topography that is frequently overwashed (Stallins et al 2020). As a result, the vegetative community on Metompkin Island is dominated by species such as Salt-meadow Cordgrass ( Spartina patens ) that exhibit rapid growth following frequent disturbances (Brantley et al 2014; Brown and Zinnert 2020). The sandy beach used by breeding shorebirds varies around the mid-point of the island.…”

Variance reflects resilience to disturbance along a stress gradient: Experimental evidence from coastal marshes

“…We are experiencing an increasing number of perturbations in an era of rapid global change (Burton et al, 2020; Nguyen & Liou, 2019), and the disturbances resulting from perturbations can affect the structural (Buma, 2015), compositional (Bowd et al, 2018), and functional (Brown & Zinnert, 2020) properties of ecosystems. It has been suggested that recovery time of an ecosystem after a disturbance tends to lengthen as the level of stress to the ecosystem increases (Dakos & Bascompte, 2014; Drake & Griffen, 2010).…”