Impact of climate change on greenhouse gas emissions and water balance in a dryland-cropping region with variable precipitation

Tina Karimi; Claudio O Stöckle; Stewart Smock Higgins; Roger L Nelson

doi:10.1016/j.jenvman.2021.112301

Impact of climate change on greenhouse gas emissions and water balance in a dryland-cropping region with variable precipitation

J Environ Manage. 2021 Jun 1:287:112301. doi: 10.1016/j.jenvman.2021.112301. Epub 2021 Mar 9.

Authors

Tina Karimi¹, Claudio O Stöckle², Stewart Smock Higgins³, Roger L Nelson⁴

Affiliations

¹ Department of Biological System Engineering, Washington State University, Pullman, WA, USA. Electronic address: tk662@cornell.edu.
² Department of Biological System Engineering, Washington State University, Pullman, WA, USA. Electronic address: stockle@wsu.edu.
³ Department of Biological System Engineering, Washington State University, Pullman, WA, USA. Electronic address: higgins.stewart@gmail.com.
⁴ Department of Biological System Engineering, Washington State University, Pullman, WA, USA. Electronic address: rnelson@wsu.edu.

PMID: 33706089
DOI: 10.1016/j.jenvman.2021.112301

Abstract

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 N₂O emissions during both baseline and future periods. The average annual N₂O emission during the baseline period was between 1.8 and 4.1 kg ha^-1 depending on AEZ. The overall N₂O 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 N₂O emission was between 1.8 and 4.4 kg ha^-1 year^-1. 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 ha^-1year^-1 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 CO₂ scenarios. The total GHG emissions were 1.95, 3.16 and 4.84 Mg CO₂-equivalent ha^-1year^-1 under RCP 4.5, and 1.99, 3.43 and 5.49 Mg CO₂-equivalent ha^-1year^-1 under RCP 8.5 during 2070s in CF, CCF and CC respectively, with N₂O accounting for about 81% of total GHG emissions.

Keywords: Climate change; CropSyst; Dryland; Nitrous oxide; Pacific Northwest; Soil organic carbon.

MeSH terms

Agriculture
Carbon
Climate Change
Greenhouse Gases*
Nitrous Oxide / analysis
Northwestern United States
Soil
Water

Substances

Greenhouse Gases
Soil
Water
Carbon
Nitrous Oxide