Decades-Long Peat Decomposition and Preservation Under Cropland and Groundwater Management

A central challenge in managed peatland conservation, especially given present global warming, is determining whether groundwater stabilization can effectively suppress oxidative degradation of deep peat horizons over decadal timescales is a central challenge in managed peatland conservation, especially in warming climates. We evaluated the relationship between hydrological management and peat preservation in the semi-arid Hula Valley (Israel), a subtropical peatland drained in the 1950s and subject to integrated groundwater management (the Hula Restoration Project; HRP) since 1994. To distinguish between historical legacy damage and ongoing degradation, we integrated multi-proxy geochemical analyses of eleven 3-m deep profiles sampled along a 2-km North–South transect line, alongside 20 years of continuous groundwater monitoring and historical land subsidence records. Our results indicate vertical and spatial degradation gradients; while surface layers (0–60 cm) exhibit severe basin-wide degradation, deeper horizons (60–300 cm) are generally better preserved. Notably, degradation in the northern parts extends well below the recent average water table (~1.2 m), suggesting a legacy of pre-1994 drainage rather than a product of current management. Despite extreme summer evaporative stress and seasonal water table fluctuations, the intermediate peat (mesotelm) geochemical indices (e.g., TOC/TN of 14–24) that are comparable to the deeper horizons. We suggest this resilience is facilitated by the HRP's integrated hydrological practices, including year-round irrigation, a canal network, groundwater control and a permanent shallow lake. These components function as a buffer that prevents the peat profile from crossing a critical desiccation threshold. By decoupling deep horizons from surface climatic extremes, these practices limit further oxidation of legacy peat, demonstrating that hydrological intervention can stabilize carbon reservoirs in warming, semi-arid peatlands and limit mesotelm degradation in a decadal timeframe.