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A CO2 Concentration Gradient Facility for Testing CO2 Enrichment and Soil Effects on Grassland Ecosystem Function
Published on: November 21, 2015
Contrasting CH4 flux responses to distinct drought regimes and nitrogen enrichment in a temperate steppe
Lan Du1, Jiatao Zhang1, Yan Shen1
1Ministry of Education Key Laboratory of Ecology and Resource Use of the Mongolian Plateau & Inner Mongolia Key Laboratory of Grassland Ecology & Observation and Research Station for the Typical Steppe Ecosystem of the Ministry of Education, School of Ecology and Environment, Inner Mongolia University, Hohhot, 010020, China.
Abstract:
Drought and nitrogen (N) deposition alter greenhouse gas fluxes, but how distinct drought scenarios interact with N enrichment to regulate the methane (CH4) sink remains poorly understood. We conducted a 4-yr field experiment in a temperate steppe to examine CH4 fluxes under three drought regimes - early-season intense drought (ID), mid-season chronic drought (CD), and mid-season reduced rainfall frequency (RF) - and N addition. CH4 uptake and its driving mechanisms were assessed through field measurements and structural equation modeling, focusing on the interplay between soil physicochemical properties, microbial abundance, and plant-mediated emissions. All drought treatments reduced the CH4 sink with divergent temporal dynamics; reduced RF caused the most persistent reduction, while N addition alleviated the inhibitory effects of CD. These shifts were driven by distinct mechanisms: ID acted via lowering previous-year belowground net primary productivity and increasing dissolved organic N, CD functioned through increased Artemisia frigida cover and reduced arbuscular mycorrhizal fungal abundance, and RF suppressed uptake via the morphological expansion of A. frigida. We conclude that CH4 sink stability is highly sensitive to drought regime, and that the morphological expansion of specific plants such as A. frigida may partially offset the soil CH4 sink.
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