Karimi Tina, Stöckle Claudio O, Higgins Stewart Smock, Nelson Roger L
Department of Biological System Engineering, Washington State University, Pullman, WA, USA.
J Environ Manage. 2021 Jun 1;287:112301. doi: 10.1016/j.jenvman.2021.112301. Epub 2021 Mar 9.
Wheat covers a significant fraction of the US Pacific Northwest (PNW) dryland agriculture. Past studies have suggested that management practices can differentially affect productivity and emission of greenhouse gases (GHGs) across the different agro-ecological Zones (AEZs) in PNW. In this study we used CropSyst, a biophysically-based cropping systems model that simulates crop processes and water and nitrogen cycles, with the purpose of evaluating relevant scenarios and contributing analyses to inform adaptation and mitigation strategies aimed at reducing and managing the risks of climate change. We compared the baseline historical period of 1980-2010 with three future periods: 2015-2045 (2030s), 2035-2065 (2050s), and 2055-2085 (2070s). The uncertainty of the future climate was captured using 12 general circulation models (GCMs) forced with two representative carbon dioxide concentration pathways (RCP 4.5 and 8.5). The study region was divided into three AEZs: crop-fallow (CF), continuous cropping to fallow transition (CCF), and continuous cropping (CC). The results indicated that areas with higher precipitation, N fertilization, and mineralization produced more NO emissions during both baseline and future periods. The average annual NO emission during the baseline period was between 1.8 and 4.1 kg ha depending on AEZ. The overall NO emission showed decreasing future trends from 2030s to 2070s which resulted from a higher proportion of N used by crops. From 2015 to 2085 under RCP 4.5, the average NO emission was between 1.8 and 4.4 kg ha year. They are slightly higher under RCP 8.5 since it is a warmer scenario. The soil organic carbon (SOC) content decreased during the baseline period while SOC did not reach equilibrium with the cropping systems considered in the study. SOC decreased during the future periods as well, with rate of change ranging from -146 to -352 kg hayear depending on AEZ and RCP. Warming increased SOC oxidation in future scenarios, but after an initial increase of SOC losses during the 2030s period, the rate of SOC losses decreased in the 2050s, and more so in the 2070s as SOC and carbon input reached equilibrium with losses. Higher carbon input resulted from higher biomass production under elevated CO scenarios. The total GHG emissions were 1.95, 3.16 and 4.84 Mg CO-equivalent hayear under RCP 4.5, and 1.99, 3.43 and 5.49 Mg CO-equivalent hayear under RCP 8.5 during 2070s in CF, CCF and CC respectively, with NO accounting for about 81% of total GHG emissions.
小麦在美国太平洋西北地区（PNW）的旱地农业中占很大比例。过去的研究表明，管理措施对PNW不同农业生态区（AEZ）的生产力和温室气体（GHG）排放有不同影响。在本研究中，我们使用了CropSyst，这是一个基于生物物理的作物系统模型，用于模拟作物生长过程以及水和氮循环，目的是评估相关情景并进行分析，为旨在减少和管理气候变化风险的适应和缓解策略提供信息。我们将1980 - 2010年的基线历史时期与三个未来时期进行了比较：2015 - 2045年（2030年代）、2035 - 2065年（2050年代）和2055 - 2085年（2070年代）。使用12个通用循环模型（GCM）并结合两种代表性二氧化碳浓度路径（RCP 4.5和8.5）来捕捉未来气候的不确定性。研究区域分为三个AEZ：作物休耕（CF）、连作到休耕过渡（CCF）和连作（CC）。结果表明，在基线期和未来时期，降水、氮肥施用和矿化率较高的地区产生更多的一氧化氮（NO）排放。根据AEZ的不同，基线期的年均NO排放量在1.8至4.1千克/公顷之间。总体NO排放显示出从2030年代到2070年代呈下降趋势，这是由于作物对氮的利用率提高。在RCP 4.5情景下，2015年至2085年期间，平均NO排放量在1.8至4.4千克/公顷·年之间。在RCP 8.5情景下排放量略高，因为这是一个更温暖的情景。在基线期土壤有机碳（SOC）含量下降，而研究中考虑的作物系统的SOC未达到平衡。在未来时期SOC也下降，变化率在 - 146至 - 352千克/公顷·年之间，具体取决于AEZ和RCP。在未来情景中，变暖增加了SOC氧化，但在2030年代SOC损失初步增加后，2050年代SOC损失率下降，在2070年代下降得更多，因为SOC和碳输入与损失达到平衡。在二氧化碳浓度升高情景下，更高的生物量产量导致更高的碳输入。在2070年代，CF、CCF和CC区域在RCP 4.5情景下的总温室气体排放量分别为1.95、3.16和4.84吨二氧化碳当量/公顷·年，在RCP 8.5情景下分别为1.99、3.43和5.49吨二氧化碳当量/公顷·年，其中NO约占总温室气体排放的81%。
