Deeper Vernal Pools Persist under Drought: The Value of Depth for Ephemeral Wetland Resilience

Vernal pools are temporary wetlands that form during winter and spring and are common in glacially scoured crystalline bedrock regions of the northeastern United States. These habitats support many organisms, including threatened and endangered amphibians. However, increasingly severe droughts associated with climate change are causing pools to dry earlier and remain dry longer, threatening the ecological functions of these ephemeral ecosystems. Additional research is therefore needed to identify characteristics associated with drought resilience. The objective of this study was to identify vernal pool characteristics associated with persistence during drought and to evaluate whether readily measurable field attributes may serve as indicators of drought resilience. Ecohydrological dynamics, hillslope flow pathways, and hydroperiod characteristics were examined across vernal pools experiencing drought conditions. Phase I used field surveys to assess relationships between pool characteristics and amphibian breeding effort. Phase II used in situ sensor clusters to explore the influence of hydrologic flow pathways on pool stability. Phase III quantified relationships between pool depth and seasonal water retention. Initial findings suggest pool characteristics, specifically depth and size, were consistently associated with indicators of drought resilience across the study phases. These relationships highlight the value of maximum depth as a practical indicator for conservation prioritization, although additional work is needed to evaluate its importance relative to other physical, hydrologic, chemical, and landscape factors. By identifying characteristics associated with longer hydroperiods and greater biological persistence, this study provides information that may assist conservation practitioners in prioritizing vernal pools for monitoring and protection under increasingly variable climatic conditions.