Simulated longleaf pine (Pinus palustris Mill.) restoration increased streamflow—A case study in the Lower Flint River Basin

Abstract

Water scarcity in the southeastern United States has increased in recent decades due to population growth, land use intensification and climate variability. Precipitation is relatively abundant, but declines in streamflow suggest a need to better manage water yield. Restoration of low-density, frequent-fire longleaf pine (Pinus palustris Mill.) woodlands, which once dominated the southeastern Coastal Plain, represents a possible strategy to increase water yield and mitigate water scarcity. The Flint River Basin has seen recent conflicts over water appropriations and lies within the historic range of longleaf pine. We used the Soil and Water Assessment Tool (SWAT) to evaluate the potential effect of longleaf pine restoration on streamflow in the Ichawaynochaway Creek, a major tributary of the Flint River. Parameters governing plant water use, for example, leaf area and leaf physiology, were adjusted to create a longleaf pine land cover. We simulated the conversion of $95,000 ha of existing forest to longleaf pine, an increase from 3% to 35% of landcover in the basin. Modelled evapotranspiration was lower for longleaf pine compared with other forest types in the region, and conversion to longleaf pine increased annual water yield by 17.9 ± 1.6 mm, or 5.2%. Proportional changes in monthly streamflow were up to 74% higher during low flow periods, when in-stream habitat is most vulnerable. Restoration of longleaf pine could be a promising way to mitigate water scarcity in the southeastern United States and adding flow during extreme droughts may prove vitally important for conserving imperilled aquatic organisms.

Water availability and seasonality shape elemental stoichiometry across space and time

“…In the southeastern USA, stream flow, evapotranspiration, and temperature variations are strongly seasonal (Benke et al, 2000; Qi et al, 2022). Periods of low flow and water deficit typically occur during the summer (June–August) and fall (September–November) when cumulative ET typically exceeds cumulative precipitation.…”

“…Periods of low flow and water deficit typically occur during the summer (June-August) and fall (September-November) when cumulative ET typically exceeds cumulative precipitation. Periods of water surplus (P > ET) occur from winter (December-February) and spring (March-May) with higher flows and the likelihood of flooding (Qi et al, 2022). During periods of below-normal precipitation, the combined effects of climate warming and agricultural irrigation have led to significant declines in growing season base river flows throughout the ICH basin (Golladay et al, 2007).…”

Assessing the potential impact of retaining native off‐site tree species in woodland restoration

“…Consequently, net precipitation reaching the forest floor is greater in longleaf pine woodlands compared to closed canopy loblolly, slash, and shortleaf pine stands (Roth & Chang 1981). Indeed, restoring degraded longleaf pine woodlands has been shown to increase stream flow (Qi et al 2022;Younger et al 2023). However, no studies have examined the effect of species identity on water dynamics while controlling for stand density.…”

Opportunities for Research on Carbon Management in Longleaf Pine Ecosystems

“…For wet-mesic longleaf pine sites maintained with prescribed fire, the mean species richness at the scale of 3 m 2 quadrats was 36 plant species, which was more than double that of xeric sites [6]. Another characteristic of low-density stands is that they have fewer evaporative losses than high-density stands, which can increase streamflow, extend the wetland hydroperiod, and promote groundwater recharge [7,8]. These co-benefits highlight the need to conserve the remaining tracts of naturally regenerated longleaf pine stands.…”