Vulnerability of diked marsh ecosystems under climate change

Diked marsh soils are natural laboratories where soil-forming processes take place over a short period of time, such as the aeration of previously water-saturated soil environments along with desalinization. These manmade ecosystems are threatened by climate change in multiple ways. Since long-term data to evaluate the vulnerability of these settings is scarce, we merged hydrological (water table, WT; electrical conductivity, EC; sea level rise), pedological (redox potential, EH; air-filled porosity, AFP), and meteorological variables (evapotranspiration, ET0; climatic water balance, CWB), and discussed the holistic relationship between these under future climate scenarios. Our multifactorial data identified ET0 as the strongest driver of WT development with a causal dependency on AFP and subsequently on EH. Within 11 years of intense monitoring, we encountered an extension of the soils’ aeration windows (EH > 300 mV) due to an enhanced seasonal WT component; i.e., the difference between winter and summer WT positions increased. This process has an impact on capillary rise from groundwaters and EC patterns due to increased seasonal variations. Desalinization stabilized two decades after diking, and the present EC does not indicate any saltwater intrusion to these near-coastal settings at present. However, sea level rise and a reduced CWB in the future will foster capillary rise from potentially salt-enriched groundwaters into the topsoils of these highly productive ecosystems. These mechanisms need to be evaluated to account for climate change–driven impacts on coastal-diked marsh soils. Indeed, a holistic view of pedological, meteorological, and hydrological variables is urgently needed.