Browsing by Author "Brecheisen, ZS"
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Item Open Access Gully-erosion estimation and terrain reconstruction using analyses of microtopographic roughness and LiDAR(Catena, 2021-07-01) Brecheisen, ZS; Richter, DDBGully mapping techniques successfully identify gullies over a large range of breadths and depths in complex landscapes but practices for estimating gully volumes need further development. Gully gap-interpolation for estimation of gully volume does not often factor in landscape microtopography in the generation of the new surface. These approaches can thus overestimate large classical gully volumes, averaging over depressions, or underestimate volumes by creating overly-smooth highly curved surfaces. Microtopographic methodology was developed to estimate the pre-gully surface and gully volume across the Calhoun Critical Zone Observatory (CCZO) in South Carolina, USA. The CCZO is a Southern Piedmont landscape severely gullied by historic agriculture with upland Ultisols many meters deep. Our gully-mapping and gully-filling approaches used 1 m LiDAR elevation data and is based on the premise that gullies are local depressions on uplands which are deeply incised with high microtopographic roughness. Our smoothing-via-filling-rough-depressions (SvFRD) algorithm iteratively fills gullies until landscape microtopographic roughness is reduced and unchanging after a subsequent iteration. Results were evaluated in the context of prior landscape bulk erosion estimates ranging from 1483 to 3708 m /ha as well as field surveys of gullies. Minimally eroded reference and highly-eroded post-agricultural terrain were compared to test gully-mapping and volume accuracy. Comparing gully-volume estimation techniques, inverse-distance-weighting (IDW) yielded the highest volume (1072 m /ha) followed by ANUDEM (638 m /ha) while spline-interpolation yielded the lowest estimate (555 m /ha). SvFRD landscape gully volume estimates (615.5 m /ha) were most similar to ANUDEM interpolation with roughness and gully extent results most similar to spline interpolation. Spline interpolation is effective and easily implemented but if microtopographic accuracy and mapping of fine-scale erosions features is desired to hindcast pre-gully terrain conditions, our depression-filling approach, implemented using free GIS and statistical software, is an effective method to estimate reasonable erosion volumes. 2 3 3 3 3 3Item Open Access Ideas and perspectives: Strengthening the biogeosciences in environmental research networks(Biogeosciences, 2018-08-15) Richter, DD; Billings, SA; Groffman, PM; Kelly, EF; Lohse, KA; McDowell, WH; White, TS; Anderson, S; Baldocchi, DD; Banwart, S; Brantley, S; Braun, JJ; Brecheisen, ZS; Cook, CS; Hartnett, HE; Hobbie, SE; Gaillardet, J; Jobbagy, E; Jungkunst, HF; Kazanski, CE; Krishnaswamy, J; Markewitz, D; O'Neill, K; Riebe, CS; Schroeder, P; Siebe, C; Silver, WL; Thompson, A; Verhoef, A; Zhang, G© Author(s) 2018. Long-term environmental research networks are one approach to advancing local, regional, and global environmental science and education. A remarkable number and wide variety of environmental research networks operate around the world today. These are diverse in funding, infrastructure, motivating questions, scientific strengths, and the sciences that birthed and maintain the networks. Some networks have individual sites that were selected because they had produced invaluable long-term data, while other networks have new sites selected to span ecological gradients. However, all long-term environmental networks share two challenges. Networks must keep pace with scientific advances and interact with both the scientific community and society at large. If networks fall short of successfully addressing these challenges, they risk becoming irrelevant. The objective of this paper is to assert that the biogeosciences offer environmental research networks a number of opportunities to expand scientific impact and public engagement. We explore some of these opportunities with four networks: the International Long-Term Ecological Research Network programs (ILTERs), critical zone observatories (CZOs), Earth and ecological observatory networks (EONs), and the FLUXNET program of eddy flux sites. While these networks were founded and expanded by interdisciplinary scientists, the preponderance of expertise and funding has gravitated activities of ILTERs and EONs toward ecology and biology, CZOs toward the Earth sciences and geology, and FLUXNET toward ecophysiology and micrometeorology. Our point is not to homogenize networks, nor to diminish disciplinary science. Rather, we argue that by more fully incorporating the integration of biology and geology in long-term environmental research networks, scientists can better leverage network assets, keep pace with the ever-changing science of the environment, and engage with larger scientific and public audiences.Item Open Access Micro-topographic roughness analysis (MTRA) highlights minimally eroded terrain in a landscape severely impacted by historic agriculture(Remote Sensing of Environment, 2019-03-01) Brecheisen, ZS; Cook, CW; Heine, PR; Richter, DDB© 2018 Elsevier Inc. The 190 km2 Calhoun Critical Zone Observatory in the Piedmont region of South Carolina, USA lies in an ancient, highly weathered landscape transformed by historic agricultural erosion. Following the conversion of largely hardwood forests to cultivated fields and pastures for ~200 years, excess runoff from fields led to extreme sheet, rill, and gully erosion across the landscape. Roads, terraces, and a variety of other human disturbances have increased the landscape's surface roughness. By the 1950s, cultivation-based agriculture was largely abandoned across most of the Southern Piedmont due to soil erosion, declining agricultural productivity, and shifting agricultural markets. Secondary forests, dominated by loblolly and shortleaf pines, have since regrown on much of the landscape, including the 1500 km2 Sumter National Forest, which was purchased from farmers and private land owners in the 1930s. Although this landscape was intensively farmed for approximately 150 years, there are a few hardwood forest stands and even entire small watersheds that have never been plowed and degraded by farming. Such relatively old hardwood stands and watersheds comprise relic landforms whose soils, regoliths, and vegetation are of interest to hydrologists, environmental historians, biogeochemists, geomorphologists, geologists, pedologists, and others interested in understanding the legacy of land-use history in this severely altered environment. In this work we champion the need for high-resolution terrain mapping and demonstrate how Light Detection And Ranging (LiDAR) digital elevation model (DEM) data and microtopographic terrain roughness analyses (MTRA) can be used to infer land use history and management. This is accomplished by analyzing fine scale variation in terrain slope across the 1190 km2 CCZO using data derived from three independent and overlapping LiDAR datasets at varying spatial resolutions. Terrain slope variability MTRA is further compared to three other methods of capturing and quantifying fine-scale surface roughness. We lastly demonstrate how these analyses can be employed in concert with historic aerial photography from the 1930's, contemporary Landsat remote sensing data, and ecological field data to identify reference relic landforms: hardwood stands, hillslopes, and small watersheds that have experienced minimal anthropogenic erosion for study and conservation.