Flatlining fens? Small-scale variations in peat properties and microtopography as indicators of ecosystem homogenisation

• For the first time, variogram ranges of peat properties and microtopography was used to assess homogenisation of alkaline fens. • The degraded fen shows longer variogram ranges, indicating greater soil and microtopographic homogeneity. • Higher SOM is associated with higher microelevation and moisture, highlighting peat accumulation’s role in shaping microtopography. • Non-linear and stronger soil-microtopography relationships are evident in the near-intact fen compared to degraded one. Fens, groundwater-fed mires, are important hotspots of biodiversity, carbon storage, and water regulation, but many have been degraded through drainage for agriculture, reducing their multifunctionality. Restoration efforts, particularly rewetting, are gaining attention in Europe, but understanding small-scale spatial processes driving ecosystem recovery remains limited. To explore spatial structure in soil properties and microtopography as indicators of ecosystem homogenisation, we collected ∼200 georeferenced soil samples from a near-natural alkaline fen and a degraded counterpart. Variogram analysis revealed distinct spatial structures in peat properties according to ecosystem status. The degraded fen exhibited longer autocorrelation ranges for soil organic matter (SOM), moisture, carbonate content, and surface microelevation, suggesting higher homogeneity compared to the near-natural fen. In addition, higher SOM was associated with higher surface microelevation and moisture content at both sites, highlighting the role of peat accumulation in shaping microtopography. The relationship between soil properties and microelevation showed stronger association and greater non-linearity in the near-intact fen compared to the degraded one. The variogram range appears to be a useful indicator of ecosystem status and homogeneity, providing valuable insights into the dynamics of fen degradation and restoration.