Effect of Plant Community on Soil Organic Carbon in the Chewaucan River Basin
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Date
2018-06-04
Authors
Lefore, Aaron
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Abstract
Variation in plant community composition has been shown to alter the concentrations of soil organic carbon (SOC) within the soil. Climate change, and anthropogenic disturbances have altered dominant plant communities across the globe, shifting them to new states of equilibrium, with important implications for SOC. The relationship between plant community and SOC is well understood in many regions; however, semi-arid ecosystems remain poorly represented in existing datasets liking above and belowground ecosystem properties. For example, in the Northwestern United States, ecosystems of the Great Basin have been both underfunded and understudied in terms of management and scholarship respectively. This is especially true within the state of Oregon, where a clear majority of research efforts are devoted to ecosystems West of the Cascades as opposed to the semi-arid ecosystems of the East. Ecosystems of eastern Oregon are undergoing rapid vegetation regime shifts that include woody encroachment, grass invasions, and large scale agricultural expansion simultaneously. To better understand the fundamental relationship between changes in plant communities and SOC within typical ecosystems of eastern Oregon, 14 plots were deployed to sample soil and vegetation across the Chewaucan Basin. Sampling sites were chosen based on a priori vegetation community type that included sagebrush (Artemisia tridentate, & Artemisia arbuscula), western juniper (Juniperus occidentalis), ponderosa pine (Pinus ponderosa), western juniper/ponderosa pine, and Alfalfa (Medicago sativa). Surface SOC was characterized for each vegetation category at a depth of 10 cm using the loss on ignition method. Woody vegetation communities showed substantially more SOC when compared to sagebrush and Alfalfa crops with plot average values ranging 67-83 Mg ℎ𝑎−1 to 33-47 Mg C ℎ𝑎−1 respectively. Sagebrush communities showed intermediate levels of SOC with 47 Mg C ℎ𝑎−1, Undeveloped plots directly adjacent to agriculture with 33.5 Mg C ℎ𝑎−1, and Alfalfa plots exhibited 43.5 Mg C ℎ𝑎−1. Juniper plots showed 67.8 Mg C ℎ𝑎−1, Pine dominated plots exhibited 83.6 Mg C ℎ𝑎−1, and Juniper/Pine dominated displayed 67 Mg C ℎ𝑎−1. This pilot study gives valuable insight into the current state of semi-arid ecosystems and provides the basis for future assessments of changes in vegetation cover and SOC concentrations.
Description
31 pages
Keywords
Soil organic carbon, Plants, Great Basin, Chewaucan Basin, Ecosystems