Wind erosion and surface stability in abandoned milled peatlands

Abstract

Peatlands exploited for their peat by the method of milling are poorly recolonized by plants after the cessation of extraction activities, in part due to unstable peat substrates. Wind erosion has been suspected to play a role in this instability. Four studies were conducted to investigate the role of wind erosion on abandoned milled peatlands. A wind tunnel experiment was performed to evaluate the erodibility of dry, loose peat as a function of its degree of decomposition. A second wind tunnel experiment was conducted to determine how crusted peats differ in their resistance to erosion as a function of their degree of decomposition, without the input of abraders. Third, wind profiles were measured in milled, revegetated and natural peatlands in southeastern Québec to determine their aerodynamic roughness length. Finally, field measurements were made at three abandoned milled peatlands through two field seasons to characterize substrate stability and particle movement. In the wind tunnel, the erodibility of loose surface peat decreased with increasing decomposition and was predicted by their equivalent diameter to mineral particles 0.84 mm in diameter. However, once surface crusts formed, peats were all resistant to erosion. Surfaces of abandoned milled peatlands were aerodynamically smooth; therefore, exposed surface elements are subject to strong erosive forces during wind events. The greatest subsidence on abandoned milled peatlands occurred in the spring, prior to the surface movement of particles. Erosion during the summer could not be clearly detected. The instability of the peat surface remains a constraint for the restoration of abandoned milled surfaces. Key Words: Peat, cutover peatland, wind erosion, soil crust, roughness length, soil stability