The role of topography in shaping the spatial patterns of soil organic carbon

Zhu, Meng and Feng, Qi and Qin, Yanyan and Cao, Jiajun and Zhang, Mengxu and Liu, Wei and Deo, Ravinesh C. and Zhang, Chengqi and Li, Ruolin and Li, Baofeng (2019) The role of topography in shaping the spatial patterns of soil organic carbon. Catena, 176. pp. 296-305. ISSN 0341-8162

Abstract

In regions with a relatively complex topography, the soil organic carbon (SOC) is characterized by a high spatial heterogeneity, which is likely to contribute to large uncertainties in the regional SOC estimation. Generally, the elevation and aspect are expected to be the two main topographic controls of the spatial patterns of SOC on steep hillslopes. However, the manner in which the aspect-induced variability in SOC varies with elevation zone is still less understood. In this study, SOC in three elevation-dependent vegetation zones (~2450 m: the shrub-steppe zone, ~2900 m: the forest-steppe zone, and ~3350 m: the shrub-meadow zone) was examined in the Qilian Mountains. Soil samples at 0–10, 10–20, 20–40, and 40–60 cm were collected on the south-, southwest-, west-, northwest-, and north-facing slopes with similar slope gradients (~32°) in each of the three vegetation zones. The results showed that the SOC density tends to increase following the elevation zone, with an average density of about 24.30 kg m−2 at the 0–60 cm. In addition, the SOC concentration appeared to have increased with the cosine of the aspect following an exponential function. The average rate of increase in terms of the aspect at 0–10 cm in the forest-steppe zone was approximately 0.46 g kg−1 degree−1, which amounted to 1.39 and 2.19 fold greater than in the shrub-steppe and shrub-meadow zones, respectively. Path analysis performed using structural equation modelling (SEM) demonstrated that the elevation and the aspect had an indirect influence on the SOC density, through a direct effect on the soil temperature, vegetation type, and soil moisture, and this could possibly explain 88% of the total variation in the SOC density. The present results suggest that the forest-steppe zone is characterized by the strongest aspect effect on SOC in comparison with the shrub-steppe and shrub-meadow zones, and confirm the importance of elevation and aspect in shaping the spatial patterns of SOC.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Permanent restricted access to Published version, in accordance with the copyright policy of the publisher.
Faculty/School / Institute/Centre: Current - Institute for Life Sciences and the Environment
Date Deposited: 12 Mar 2019 23:48
Last Modified: 13 Jun 2019 04:59
Uncontrolled Keywords: soil organic carbon; elevation; aspect; vegetation type; structural equation modelling
Fields of Research : 07 Agricultural and Veterinary Sciences > 0703 Crop and Pasture Production > 070302 Agronomy
Socio-Economic Objective: E Expanding Knowledge > 97 Expanding Knowledge > 970107 Expanding Knowledge in the Agricultural and Veterinary Sciences
Identification Number or DOI: 10.1016/j.catena.2019.01.029
URI: http://eprints.usq.edu.au/id/eprint/35760

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