Abstract
The restoration of degraded ecosystems and landscapes is challenging, because returning to the original state is often socio-economically unfeasible. A novel approach is to construct new ecosystems to improve the functioning of degraded landscapes. However, the development of novel ecosystems is largely driven by the pre-construction hydrogeophysical and ecological conditions of the soil. In Lake Markermeer, a deteriorating freshwater lake in the Netherlands, a large archipelago is currently being constructed to boost the ecological functioning of the lake. Hence, islands – with wetlands and with more elevated and dryer areas – have been created to sustain biodiversity and key biogeochemical functions such as nutrient cycling. The islands are constructed from lake-bottom sediments. To study how two potentially important drivers, water level and bioturbation, affect soil characteristics in a novel wetland ecosystem, we experimentally tested the effects of water level (-30, -10 and 5 cm), and bioturbation by earthworms (Lumbricus rubellus) and Tubifex spp. in a microcosm experiment. We demonstrate that a high water level prevents soil subsidence, soil crack formation and carbon dioxide (CO2) emissions, and affects nitrogen cycling. In dryer soils, the presence of earthworms strongly increases CO2 emissions next to reducing soil crack formation, while Tubifex spp. in wetter soils hardly affect soil characteristics. Our findings highlight the important roles of both water level and bioturbation for the functioning of novel soils, which likely affects vegetation development in novel ecosystems. This knowledge can be used to aid the construction and nature development of novel wetlands.
Highlights
Anthropogenic disturbance is causing massive losses to ecosystems; including the degradation of iconic ecosystems such as wetlands, trop ical rainforests, savannahs, peatlands and coral reefs (Halpern et al, 2007; Leifeld et al, 2019; da Cruz et al, 2020)
Water level had a major influence on overall soil processes and structure, while biotic treatments seemed less important, as illustrated by a Principal Component Analyses (PCA) (Fig. 2)
In accordance with our hypotheses, our results show that earth worms affected soil properties, while Tubifex spp. did not at the density we used and irrespectively of the water level
Summary
Anthropogenic disturbance is causing massive losses to ecosystems; including the degradation of iconic ecosystems such as wetlands, trop ical rainforests, savannahs, peatlands and coral reefs (Halpern et al, 2007; Leifeld et al, 2019; da Cruz et al, 2020). The losses are large in wetlands, as 50–87 % of their global extent is currently degraded or has been lost since 1700 AD (Mitsch and Gosse link, 2007; Davidson, 2014). These losses result in the extinc tion of species and typical biodiversity, and in the loss of vital ecosystem services (Stirling et al, 2020). Conservation practitioners and policy makers are searching for new practises to halt the decline in wetland habitat. The restoration of degraded wetlands is often chal lenging and expensive, because many stressors (e.g. overgrazing, eutrophication, unfavourable environmental conditions for establish ment) frustrate restoration (Zedler, 2000; Temmink et al, 2020). A novel approach is the creation of entirely new ecosystems to enhance the functioning of severely altered and degraded landscapes (Hobbs et al, 2009), because many ecosystem services and functions operate at large scale, comprising different ecosystems (van der Zee et al, 2012; van de Koppel et al, 2015)
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