GSA Connects 2021 in Portland, Oregon

Paper No. 55-6
Presentation Time: 2:30 PM-6:30 PM


ZHANG, Zhuojun1, ZHAO, Zhiqi2, LIU, Congqiang3, CHADWICK, Oliver A.4, HU, Yongfeng5, VAUGHAN, Karen L.6 and ZHU, Mengqiang6, (1)Department of Ecosystem Science and Management, University of Wyoming, Laramie, WY 82071; State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Guiyang, 550081, China, (2)School of Earth Science and Resources, Chang'an University, Xi'an, WY 710054, China, (3)Institute of Surface-Earth System Sciences, Tianjin University, Tianjin, 300072, China, (4)Geography Department, University of California, Santa Barbara, Santa Barbara, CA 93106, (5)Canadian Light Source Inc., University of Saskatchewan, Saskatoon, SK S7N 2V3, Canada, (6)Department of Ecosystem Science and Management, University of Wyoming, Laramie, WY 82071

Phosphorus (P) availability in soils controls critical functions and properties of terrestrial ecosystems. However, the effects of climate and dust inputs on P availability and speciation in soils remain not fully understood. We determined P availability and speciation in soil profiles of contrasting climate using a combination of P K-edge X-ray absorption near edge spectroscopy and chemical extractions. The major features of the vertical distributions of P concentration and speciation persist under the contrasting climates and can be predicted by combinations of weathering, leaching, biolifting and dust inputs. Warmer/wetter climate results in decreases in the proportions of both calcium-bound P (Ca-P) and non-occluded P (Pn‑occ), but increases in the P loss and the proportions of organic P (Po), Fe- and Al-bound P [(Fe+Al)‑P] and occluded P (Pocc). Regardless of soil depth and climate, the inorganic P (Pi) speciation, i.e., the relative proportions of Ca-P and (Fe+Al)‑P over total Pi, correlates well with soil pH and weathering degree (Chemical Index of Alteration, CIA), and Po concentration with pedogenic Fe and Al and organic carbon concentration, which suggest that Pi speciation is primarily controlled by soil geochemistry/mineralogy, and Po concentration by both soil geochemistry/mineralogy and biological activities. Pocc correlates with CIA, and thus is mainly controlled by soil mineralogy; but Pn-occ correlates weakly with soil properties, probably due to its susceptibility to combined influences of dust inputs, leaching, biological activities, and sorption. Furthermore, we evaluated the effects of dust inputs on P transformation in sub-humid ecosystems. Continuous dust inputs increase the concentration of total P in the acidic surface soils and maintain relatively high Ca-P levels there although acidic dissolution constantly transforms the Ca-P to other forms. The dust-borne Ca-P in soils is likely the main source of soil labile P as suggested by a positive correlation between them. On the other hand, dust inputs bring iron-rich materials and enhance formation of large amounts of (Fe+Al)-P and Pocc in soils. In addition, C horizon shows a relatively high weathering degree, likely caused by dust inputs that increase soil moisture and microbial activities. This study provides an integration and synthesis of controls of climate, dust inputs and edaphic variables on P dynamics in forest soils.