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

ABSTRACT

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.