Blackman, Taylor, Department of Ecosystem Science and Management, The Pennsylvania State University, 1619 Houserville Rd, State College, PA 16801, tnb5149@psu.edu.
Vernal pools are small ephemeral wetlands most well-known for supporting amphibian reproduction, among other unique biota. In the Ridge and Valley of central Pennsylvania, vernal pools occur naturally and artificially by the thousands across different landscape positions and underlying lithologies. The origins of these features stem largely from periglacial soil processes during the Pleistocene, legacy roads, and shallowing surface mining. This presentation will cover the different settings in which pools are found and the landscape conditions that underpin their hydrology. A comparison of two distinctly different settings, forested headwaters versus an urbanized valley floor, will highlight the variety of observed vernal pool hydro-regimes and degrees of stream connectivity: 1) a cluster of 11 pools above the headwaters along a topographic saddle underlain by shale and 2) three created vernal pools at Millbrook Marsh in the middle of State College.
In the first setting, pools were formed over 10 k.y.a. with some containing 36% soil organic matter at 1.25 m, and they reside just above the stream network. High-frequency water level monitoring was conducted within pools and nearby shallow groundwater wells during Water Year 2022. At Millbrook Marsh, pools were built by targeting specific soil strata. The marsh is covered by legacy sediment (post-European arrival) that is 1 to 1.5 m thick, with plastic trash marking the top of the horizon and metal at lower extents. Below this layer is a dense fragipan layer comprised of loamy textures 0.5 m or less thick, which caps a deep mixed gravel layer. For groundwater to reach the created wetlands, it was key to have the lowest extent of the vernal pool within the gravel layer. Vernal pools can be created or enhanced for an array of specific outcomes such as carbon sequestration, amphibian habitat, nutrient management and water quality, and as provisioning resource for terrestrial species. A vernal pool’s functions are primarily controlled by hydrology, specifically how it responds to rainfall and dries out seasonally. The lessons learned from natural systems are crucial to guiding creation and restoration efforts.
Vernal Pools, Headwaters, Legacy Sediments, Ephemeral Hydrology