Nitrogen functional gene activity in soil profiles under progressive vegetative recovery after abandonment of agriculture at the Puding Karst Critical Zone Observatory, SW China

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Li, D., Zhang, X., Green, s., Dungait, J. A. J., Wen, X., Tang, Y., Guo, Z., Yang, Y., Sun, X. and Quine, T. 2018. Nitrogen functional gene activity in soil profiles under progressive vegetative recovery after abandonment of agriculture at the Puding Karst Critical Zone Observatory, SW China. Soil Biology and Biochemistry. 125 (October), pp. 93-102. https://doi.org/10.1016/j.soilbio.2018.07.004

AuthorsLi, D., Zhang, X., Green, s., Dungait, J. A. J., Wen, X., Tang, Y., Guo, Z., Yang, Y., Sun, X. and Quine, T.
Abstract

At the end of the 20th century, China launched the ‘Grain-for-Green’ Project (GGP) that recommended the abandonment of low-yielding sloping farmland (>15°) prone to soil degradation by erosion, to allow recovery through natural vegetative regeneration. The effect of this policy on soil nitrogen (N) cycling, as fertilization applications are also withdrawn after abandonment, is poorly understood. A space-for-time approach was applied to investigate the responses of nitrogen functional genes (NFGs) in soil profiles (surface to bedrock) associated with progressive vegetative recovery (sloping farmland > recently abandoned sloping farmland > secondary forest > primary forest) at the Puding Karst Critical Zone Observatory in Guizhou province, southwest China. Coincident soil chemical properties (dissolved organic carbon (DOC), nitrate (NO3- -N), ammonium (NH4+-N), available inorganic phosphorus (AP), soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP)) were also quantified. We found that the absolute abundance of NFGs significantly varied according to the phase of vegetation recovery, and that concentrations of AP and NO3--N were the best explanatory variables. The external N from fertilizer application promoted the absolute abundances of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in sloping farmland. The relative abundances of chiA (associated with decomposition) increased with soil depth across all vegetation recovery phases. The relative abundances of chiA and nifH (associated with N fixation) accounted for the largest proportion (58–72%) of the measured NFGs, indicating that active N-acquisition increased along the vegetation recovery gradient. The ratios of (chiA + nifH)/(AOA + AOB) and the sums of (nirK + nirS) were larger in the forest soil than those of sloping farmland and abandoned sloping farmland, implying a greater capacity for N storage potential, though accompanied by increased gas N emission potential, in the karst forest ecosystems. Our results provide a new and comprehensive understanding of soil N cycling potentials at the microscale in degraded and recovering karst ecosystems.

KeywordsNitrogen functional genes; Soil profile; Vegetation recovery; Karst ecosystems; NitratePhosphorus
Year of Publication2018
JournalSoil Biology and Biochemistry
Journal citation125 (October), pp. 93-102
Digital Object Identifier (DOI)https://doi.org/10.1016/j.soilbio.2018.07.004
Web address (URL)https://www.sciencedirect.com/science/article/pii/S0038071718302323?via%3Dihub#!
Open accessPublished as non-open access
FunderNational Natural Science Foundation of China
National Environmental Research Council
Funder project or code41571130043
41571251
NE/N007433/1
Output statusPublished
Publication dates
Online11 Jul 2018
Publication process dates
Accepted07 Jul 2018
Copyright licensePublisher copyright
PublisherElsevier
ISSN0038-0717

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