COS 234-4 - Assessing drivers of ecosystem change using qualitative land health assessments and erosion models

Background/Question/Methods

Soil erosion drives ecosystem changes that negatively impact plant communities and ecosystem function. Qualitative and quantitative assessments can reveal soil erosion interactions with ecosystem change. Qualitative land health assessments compare erosion indicators to a defined reference condition to determine historic erosion and erosion risk based on ecosystem measurements and observations. Quantitative erosion models utilize ecosystem attribute data to more precisely estimate erosion risk and can evaluate erosion risk over time. Qualitative erosion indicators and erosion model outputs may therefore identify different soil erosion responses to ecosystem change. We evaluate what qualitative land health assessments and soil erosion models can tell us about soil erosion responses to ecosystem changes in the Chihuahuan Desert and how combining assessments can inform land management decisions. We compared Aeolian EROsion (AERO) model and Rangeland Hydrology and Erosion Model (RHEM) estimates with qualitative erosion indicator assessments from monitoring plots following Interpreting Indicators of Rangeland Health (IIRH) protocol. We identified patterns in qualitative erosion indicators and model outputs for areas with distinctive soil, vegetation, and physical characteristics (ecological sites). We then determined physical processes and ecosystem changes for the plots where qualitative indicators and model outputs identified soil erosion and whether responses among ecological sites were generalizable.

Results/Conclusions

Our results suggest that qualitative soil erosion indicators identified evidence of historic erosion and erosion risk, and the soil erosion model outputs identified risk of erosion for the selected ecological sites. However, soil erosion responses depended on the ecosystem change and ecological dynamics of the studied sites. Additionally, qualitative soil erosion indicators and the soil erosion model outputs reflected certain structural and functional changes, but these may not always align with defined ecosystem changes (e.g., states). For example, wind erosion may increase in response to structural vegetation changes (canopy height and spatial arrangement) associated with state changes at some sites, but vegetation changes at other sites may not increase erosion risk due to differences in scale (smaller gaps or taller vegetation) or other variables (e.g., soil surface armoring by rock). These results provide insights into applying qualitative land health assessments and soil erosion models together to assess drivers of ecosystem change and support identifying practical management actions.