title: Carbon budget of a rainfed spring maize cropland with straw returning on the Loess Plateau, China.
abstract: Assessing the carbon budget of rainfed agricultural ecosystems is a vital component in the process of estimating the global carbon balance. We used eddy covariance techniques combined with soil respiration measurements to estimate the carbon budget of a rainfed spring maize field where straw returning was practiced, on the Loess Plateau, China, during 2012-2014. Carbon fluxes and their components (except heterotrophic respiration, Rh) exhibited single-peak seasonal patterns, and linear relationships were found between daily gross primary productivity (GPP) and net ecosystem exchange (NEE), and between daily GPP and ecosystem respiration (Re), with goodness of fit value of 0.96 and 0.85, respectively. The green leaf area index was the most important factor controlling seasonal variations in daily NEE, Re, and GPP during the growing season, followed by photosynthetically active radiation and air temperature (Ta). Daily Rewas mainly controlled by air temperature during the non-growing season, when Reaccounted for only ~17% of the annual Redue to winter temperatures. Growing season plant respiration (Rp) was the most important source of carbon emissions from the maize field, with aboveground plant respiration being the major part of Rp. Rhaccounted for ~60% of total soil respiration. Only ~60% of the annual GPP was lost as Re, resulting in an average annual net CO2uptake of 509gCm-2. Taking into account carbon exported (483gCm-2) and carbon imported (10gCm-2), the average annual net biome productivity was 37gCm-2, indicating that the spring maize field with straw returning on the Loess Plateau was a weak carbon sink.
authors.affiliation: Key Laboratory of Dryland Agriculture, Ministry of Agriculture, Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China. Electronic address: gaoxiang20061186@126.com.
authors.forename: Xiang
authors.initials: X
authors.lastname: Gao
authors.affiliation: Key Laboratory of Dryland Agriculture, Ministry of Agriculture, Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China. Electronic address: gufengxue@caas.cn.
authors.forename: Fengxue
authors.initials: F
authors.lastname: Gu
authors.affiliation: Key Laboratory of Dryland Agriculture, Ministry of Agriculture, Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China. Electronic address: haoweiping@caas.cn.
authors.forename: Weiping
authors.initials: W
authors.lastname: Hao
authors.affiliation: Key Laboratory of Dryland Agriculture, Ministry of Agriculture, Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China. Electronic address: meixurong@caas.cn.
authors.forename: Xurong
authors.initials: X
authors.lastname: Mei
authors.affiliation: Key Laboratory of Dryland Agriculture, Ministry of Agriculture, Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
authors.forename: Haoru
authors.initials: H
authors.lastname: Li
authors.affiliation: Key Laboratory of Dryland Agriculture, Ministry of Agriculture, Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
authors.forename: Daozhi
authors.initials: D
authors.lastname: Gong
authors.affiliation: Key Laboratory of Dryland Agriculture, Ministry of Agriculture, Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
authors.forename: Lili
authors.initials: L
authors.lastname: Mao
authors.affiliation: Key Laboratory of Dryland Agriculture, Ministry of Agriculture, Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
authors.forename: Zuguang
authors.initials: Z
authors.lastname: Zhang
keywords: Carbon budget; Eddy covariance; Soil respiration; Spring maize; The Loess Plateau