Setting a reference for wetland carbon: the importance of accounting for hydrology, topography, and natural variability

Abstract

Wetland soils are a key global sink for organic carbon (C) and a focal point for C management and accounting efforts. The ongoing push for wetland restoration presents an opportunity for climate mitigation, but C storage expectations are poorly defined due to a lack of reference information and an incomplete understanding of what drives natural variability among wetlands. We sought to address these shortcomings by 1) quantifying the range of variability in wetland soil organic C (SOC) stocks on a depressional landscape (Delmarva Peninsula, USA) and 2) investigating the role of hydrology and relative topography in explaining variability among wetlands. We found a high degree of variability within individual wetlands and among wetlands with similar vegetation and hydrogeomorphic characteristics. This suggests that uncertainty should be presented explicitly when inferring ecosystem processes from wetland types or land cover classes. Differences in hydrologic regimes, particularly the rate of water level recession, explained some of the variability among wetlands, but relationships between SOC stocks and some hydrologic metrics were eclipsed by factors associated with separate study sites. Relative topography accounted for a similar portion of SOC stock variability as hydrology, indicating that it could be an effective substitute in large-scale analyses. As wetlands worldwide are restored and focus increases on quantifying C benefits, the importance of appropriately defining and assessing reference systems is paramount. Our results highlight the current uncertainty in this process, but suggest that incorporating landscape heterogeneity and drivers of natural variability into reference information may improve how wetland restoration is implemented and evaluated.

Multi-Scenario Simulation of Ecosystems Based on Adaptive Restoration to Promote Human–Nature Harmony: A Case Study of Loess Hills Micro-Watershed

“…The characteristics of dominance degree of each stable ecosystem on the slope gradient are similar to those of the elevation gradient, but the difference in the dominance degree compared to the elevation gradient is relatively small (Figure 5) [28]. Through the analysis of the distribution index of stable ecosystems, and combined with the changing patterns of dominant position of ecosystems in different periods, the above adjustment strategies for variable ecosystem types are reasonable [29].…”

“…The characteristics of dominance degree of each stable ecosystem on the slope gradient are similar to those of the elevation gradient, but the difference in the dominance degree compared to the elevation gradient is relatively small (Figure 5) [28]. Through the analysis of the distribution index of stable ecosystems, and combined with the changing patterns of dominant position of ecosystems in different periods, the above adjustment strategies for variable ecosystem types are reasonable [29]. The comparative analysis of soil properties between variable and stable ecosystems under different terrain combinations shows that the soil physical and chemical properties of variable ecosystems are similar to those of stable farmland ecosystems, followed by stable grassland ecosystems, and significantly different from stable shrub and forest ecosystems (Table 4).…”