Assessment of Arundinaria gigantea as Natural Infrastructure for Riparian Restoration

Abstract

Arundinaria gigantea, or rivercane, is a bamboo native to the riparian and bottomland areas of the southeast United States and carries significance among Indigenous peoples from this region. Dense clumps of rivercane, or canebrakes, provide wildlife habitat and the elaborate network of rhizomes offer streambank stabilization and nutrient and sediment retention benefits to support water quality; however, this culturally and ecologically important natural resource has declined to less than 2 percent of its former abundance. With the abundance of rivercane diminishing from the landscape, Indigenous peoples with ties to this keystone species are losing a significant tool for cultural crafts and uses. To better understand how rivercane productivity and resiliency are being affected by the changing climate, the first study was conducted within a wind tunnel-porous media test facility operated by the United States Army Corps of Engineers (USACE). The facility, the Synthetic Environment for Near-Surface Sensing and Experimentation (SENSE) wind tunnel at the USACE Engineer Research and Development Center (ERDC) in Vicksburg, Mississippi, USA, allowed for simulating micro-climatological scenarios of sudden below-freezing temperatures, or “cold snaps”, and extreme hot and dry conditions, or “flash droughts” on rivercane plants prepared in a soil-test bed and interfaced with the wind tunnel. Using manual and autonomous environmental sensors, the rivercane plants were monitored throughout the duration of each simulation. Chlorophyll/carotenoid index (CCI), used to monitor plant stress, and stomatal conductance (gs), enlisted to gage photosynthetic or transpiration activity, data were fit with a linear mixed effects model (LMM), which showed there were significant differences between the rivercane plants exposed to the two experiments and in situ values. Soil moisture and vapor pressure deficit (VPD) were compared to CCI and gs to further explore the effects of transplanting and extreme climate events (ECEs) on rivercane. Overall, the two ECE scenarios demonstrated how rivercane restoration via transplanting could be affected unless management for suitable acclimation occurs. Additionally, these studies provided insight on the importance of matching rivercane plant stock to their receiving climate for successful land resilient restoration and reintroduction projects. The next study focused on the collection of high-resolution multispectral aerial imagery data of known rivercane ecosystems, or canebrakes, within bottomland forest canopies along riparian areas and field edges. The reflectance data from red, blue, green, red-edge, and near infrared (NIR) wavelengths were analyzed to create index maps for detecting the canebrakes using remote sensing. Canebrakes were detected at the known locations; however, the imagery in dense vegetation areas did not allow for distinguishing rivercane from other riparian vegetation. Ground-truthing canebrakes is the most reliable method for identifying rivercane, but future combinations of readily accessible optical sensors, providing hyperspectral data, and light detection and ranging (LiDAR) would allow for more precise and accurate remote sensing of canebrakes in bottomland riparian areas to be conducted. The third study combined physical parameters collected at known locations of rivercane to inform a suitability model in geographic information system (GIS) software where potential rivercane restoration could be in the Illinois River watershed. Land use, soil type, elevation, and wetland datasets were reclassified according to the distribution of the known canebrake characteristics, which favored classes with greater rates of rivercane occurrence, and the sum of the four dataset’s criteria established a likelihood scale for rivercane occurrence within the watershed. Potential rivercane locations overlapped with 80 percent of the known canebrake locations, and remotely sensed rivercane locations from aerial imagery intercepted 82 percent of known canebrake locations. Rivercane restoration efforts can be focused on locations identified from the GIS model. The model could also serve as a guide for Indigenous nations to gather rivercane for cultural use. In the final study, rivercane restoration and wetland creation scenarios were compared using a calibrated hydrologic model, Gridded Surface/Subsurface Hydrologic Analysis (GSSHA), to determine their associated effects on water quality and quantity near Lake Frances in the Illinois River watershed of eastern Oklahoma and northwest Arkansas. The potential rivercane restoration and wetland creation scenarios demonstrated increased infiltration and groundwater recharge and decreased discharge and lateral inflow to channels, while surface water retention increased only for the wetlands. Based on these findings, it was estimated that the percent area of rivercane or wetland added to the watershed resulted in the logarithmic increase for the percent decreases of expected peak flow. Rivercane restoration and wetland creation also decreased sediment and associated nutrient loading into channels. GSSHA modeling allowed enhanced understanding of the watershed interactions of natural infrastructure implementation. In conclusion, culturally important species (i.e., rivercane) incorporated as natural infrastructure can restore riparian areas and subsequently increase utilization for cultural practices. Successful rivercane restoration depends on matching source plants to the environmental conditions of the restoration area to ensure resilience and survival. Rivercane remains difficult to access due to habitat loss and limitations in remote sensing, but future research can leverage high-resolution imagery combined with advanced wavelength ratios and transformations to enable faster and more accurate identification. Expanding knowledge of the physical characteristics that define canebrakes will help refine habitat suitability assessments for rivercane across diverse watersheds. Beyond improving water quality and hydrologic function through natural infrastructure in bottomland hardwood forests, restoring rivercane, wetlands, and associated vegetation also creates opportunities for cultural practices among Indigenous communities.