TY - JOUR

T1 - Characterization and formation of the pristine rhizoliths around Artemisia roots in dune soils of Tengeri Desert, NW China

AU - Sun, Qingfeng

AU - Zamanian, Kazem

AU - Huguet, Arnaud

AU - Fa, Keyu

AU - Wang, Hong

N1 - Funding information: We express special gratitude to the anonymous reviewers and the editors for their constructive and valuable comments to improve the paper. We thank Wenhui Xue and Wentao Pei for assistant in field exploration; Darden Hood, Ronald Hatfield, Christopher Patrick for radiocarbon analysis; Pu Wang for microscopy and work; Professor Lijun Ling for photographing; Professor Huyue Song for analyzing isotopes; Professor Xuelin Chen for identifying vegetation species; Professor Keyu Liu, Professor Guangui Yuan, Professor Viktor Golubtsov, and Doctor Eron Raines for their comments. We also thank Professor Fahu Chen for suggestions on this study. This work is supported by National Natural Science Foundation of China (No. 41561046 ) and Sino-German Mobility Project (M-0069).

PY - 2020/10

Y1 - 2020/10

N2 - Rhizoliths are the products of mineralization, petrification, or fossilization around and/or within plant roots. Among them, carbonate rhizoliths are the most common. Pristine carbonate rhizoliths with co-existing plant root relicts in the Tengeri Desert, NW China were studied, with a combination of intensive field observations and laboratory methods such as microscopy, scanning electronic microscopy, energy dispersive X-ray spectra, radiocarbon dating, and isotope mass spectrometer. The field observations revealed that the pristine rhizoliths are only present at the sites where Artemisia sphaerocephala Krasch are growing i.e. in swales among sand dunes. Soil moisture of the swales is the main controlling factor of rhizoliths formation. It is in turn affected by the soil physical properties, landscape position, and climate variability, consistent with the locations of sampled rhizoliths in the swales where Artemisia plants are mostly distributed. The 14C AMS dating indicated that the rhizoliths are much older (4000–5000 years) than their co-existing modern plant root relicts in agreement with field observations. Morphological, mineralogical and isotopic analyses revealed that carbon sources used for the rhizoliths formation were partially derived from decomposing plant roots but with significant contribution from dissolution of lithogenic carbonates. The calcium sources were suggested to be the in situ weathering of minerals (mostly lithogenic carbonates) and the pressure-dissolution of carbonates. Enough CO2 from the root decomposition have triggered carbonate accumulation around the root to form rhizoliths. Other minor chemical components of the root are S, N, P, which produce acidic water with the negative ions of SO4 2−, NO3 –, PO4 3-, have also favored acidic soil environment and enhanced carbonate dissolution and mineral weathering. Redox environment around Artemisia roots were also observed to be a key factor for the pristine rhizolith formation. The pristine rhizoliths were preferentially formed in semi-closed redox condition with water nearly always available at intermediate depths. In addition, they were formed through carbonate epidiagenesis in shallow soils of the desert. Altogether, our results showed that the formation of the pristine rhizoliths was affected by the combination of several environmental factors. This led us to propose a conceptual model of rhizolith formation in desert soils.

AB - Rhizoliths are the products of mineralization, petrification, or fossilization around and/or within plant roots. Among them, carbonate rhizoliths are the most common. Pristine carbonate rhizoliths with co-existing plant root relicts in the Tengeri Desert, NW China were studied, with a combination of intensive field observations and laboratory methods such as microscopy, scanning electronic microscopy, energy dispersive X-ray spectra, radiocarbon dating, and isotope mass spectrometer. The field observations revealed that the pristine rhizoliths are only present at the sites where Artemisia sphaerocephala Krasch are growing i.e. in swales among sand dunes. Soil moisture of the swales is the main controlling factor of rhizoliths formation. It is in turn affected by the soil physical properties, landscape position, and climate variability, consistent with the locations of sampled rhizoliths in the swales where Artemisia plants are mostly distributed. The 14C AMS dating indicated that the rhizoliths are much older (4000–5000 years) than their co-existing modern plant root relicts in agreement with field observations. Morphological, mineralogical and isotopic analyses revealed that carbon sources used for the rhizoliths formation were partially derived from decomposing plant roots but with significant contribution from dissolution of lithogenic carbonates. The calcium sources were suggested to be the in situ weathering of minerals (mostly lithogenic carbonates) and the pressure-dissolution of carbonates. Enough CO2 from the root decomposition have triggered carbonate accumulation around the root to form rhizoliths. Other minor chemical components of the root are S, N, P, which produce acidic water with the negative ions of SO4 2−, NO3 –, PO4 3-, have also favored acidic soil environment and enhanced carbonate dissolution and mineral weathering. Redox environment around Artemisia roots were also observed to be a key factor for the pristine rhizolith formation. The pristine rhizoliths were preferentially formed in semi-closed redox condition with water nearly always available at intermediate depths. In addition, they were formed through carbonate epidiagenesis in shallow soils of the desert. Altogether, our results showed that the formation of the pristine rhizoliths was affected by the combination of several environmental factors. This led us to propose a conceptual model of rhizolith formation in desert soils.

KW - Artemisia roots

KW - Carbonatization

KW - Dune soil

KW - Pristine rhizoliths

KW - Redox condition

KW - Soil moisture

UR - http://www.scopus.com/inward/record.url?scp=85084342653&partnerID=8YFLogxK

U2 - 10.1016/j.catena.2020.104633

DO - 10.1016/j.catena.2020.104633

M3 - Article

AN - SCOPUS:85084342653

VL - 193

JO - CATENA

JF - CATENA

SN - 0341-8162

M1 - 104633

ER -