Once a pond in time: employing palaeoecology to inform farmland pond restoration

Abstract

The restoration of highly terrestrialized farmland ponds that combines the removal of woody vegetation and pond sediment greatly enhances aquatic biodiversity. Nonetheless, questions remain regarding the historical precedent of pond restoration, and particularly if post‐restoration aquatic macrophyte communities resemble pre‐terrestrialization assemblages. We used a paleoecological approach to address these questions for a typical, recently restored farmland pond in Norfolk, eastern England. Plant and animal remains in pond sediment cores were used to infer decadal‐centennial scale changes to pond communities and to identify past pond management events. We then evaluated the resemblance of restored and historical assemblages by comparisons with contemporary post‐restoration vegetation data. Based on changes in the abundance of terrestrial leaf remains and other indicators (increases followed by declines of aquatic organisms), the study pond appears to have a long history (going back to the early‐1800s) of canopy management (at least three inferred management events), but after the mid‐1970s, steady and substantial increases in terrestrial indicators suggest cessation of management resulting in uninterrupted terrestrialization. Aquatic macrophyte communities arising after restoration showed some similarities with historical assemblages, but also contained apparently new species. This study demonstrates how paleolimnological methods can improve understanding of pond ecological histories to better inform restoration targets and practices.

Effect of initial planting on vegetation establishment in different depth zones of constructed farm ponds

“…Although the effect of management was not examined in this study, management was considered to be necessary for the following reasons: (1) Woody plants gradually invaded the inner area of the ponds as part of the terrestrialization process. Shallow farm ponds without management can be fully terrestrialized in 20–30 years (Walton et al 2021); (2) Species diversity began to decrease after 1–4 years of construction. In addition, in the fifth year, the number of species in the experimental ponds decreased to below the regularly managed reference pond; (3) The percent vegetation cover in the ponds increased to 93% compared to 45% in the reference pond.…”

“…Although rapid vegetation establishment in farm ponds has been reported in some studies (Matthews & Endress 2010; Walton et al 2021), the net effect of planting in newly constructed farm ponds has not been fully evaluated yet. This study showed that fertile conditions and abundant seed sources allowed vegetation to establish quickly in farm ponds without planting.…”

“…Farm ponds have high ecological values, such as purifying water, controlling floods, and providing wildlife refuge, even though their sizes are small (Usio et al 2013). Farm ponds have been found to be biodiversity hotspots in several climatic regions (Casas et al 2012; Walton et al 2021). Due to their relatively small size and physicochemical characteristics, farm ponds cannot replace natural wetlands (Sánchez‐Zapata et al 2005).…”

Pond ecology and conservation: research priorities and knowledge gaps

“…Consequently, there are significant knowledge gaps regarding the long-term dynamics and patterns in pond environments, biological diversity, and functioning. As for larger lentic water bodies, paleoecological approaches could provide critical information for inferring long-term (c.100s-1000s years) changes in pond ecology in response to environmental change and, in turn, inform restoration strategies (Walton et al 2021). This is of particular importance for demonstrating the scope for returning communities to those recorded prior to major human impacts.…”

Ecoacoustics as a novel tool for assessing pond restoration success: Results of a pilot study

“…Furthermore, UK farmland ponds are widely threatened by terrestrialization, resulting in the overwhelming numerical dominance of late-successional ponds with high canopy shading and lowered species diversity at pond and pond-landscape scales (Sayer et al, 2013;Sayer & Greaves, 2020). To tackle the problem of terrestrialization, farmland ponds can be restored by active tree and sediment removal, and much recent research shows this approach to be highly effective (Sayer & Greaves, 2020;Walton et al, 2021). This pilot study investigated the potential of ecoacoustic surveys for assessing the success of pond restoration.…”