Premium
Soil Nitrogen and Greenhouse Gas Dynamics in a Temperate Grassland under Experimental Warming and Defoliation
Author(s) -
Bork Edward W.,
Attaeian Behnaz,
Cahill James F.,
Chang Scott X.
Publication year - 2019
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2018.04.0150
Subject(s) - environmental science , grassland , agronomy , temperate climate , growing season , global warming , mineralization (soil science) , nitrogen cycle , nitrification , soil water , biogeochemical cycle , greenhouse gas , nitrogen , chemistry , ecology , climate change , biology , soil science , organic chemistry
Core Ideas Warming but not defoliation increased short‐term N mineralization. The CO 2 efflux initially increased with warming and defoliation but promptly stabilized. Warming and defoliation reduced N 2 O emissions but not when combined. Soil responses to warming were complex and transient in this temperate grassland.Grasslands are important for C storage and supporting livestock production, yet little is understood about how warming interacts with defoliation to alter soil C and N dynamics. We examined how increased growing season temperature and defoliation influenced soil microbial biomass C (MBC) and N (MBN), N mineral dynamics, and greenhouse gas (GHG) flux within the top 15 cm of mineral soil in a northern temperate grassland of Alberta, Canada. We performed a 2‐yr experiment with open‐top chambers to increase soil temperatures, with warming assessed alone and combined with a single intense midsummer defoliation treatment. Soil MBC and MBN did not respond to warming or defoliation ( P > 0.05). Warming increased soil nitrification and net N mineralization in the spring of the second growing season ( P < 0.05) but did not persist beyond May. Although warming and defoliation both increased CO 2 efflux separately during the first growing season ( P < 0.05), the combination of these treatments reduced CO 2 efflux to levels similar to the controls, with no lasting effects into the following growing season. Warming also interacted with defoliation to increase N 2 O flux in the second growing season relative to plots under either warming or defoliation treatment, whereas CH 4 uptake was not influenced by our treatments. These results show the complex but transient impacts of warming and defoliation on soil C and N, particularly GHGs. Further research is needed to understand how these northern temperate grasslands respond to long‐term factorial experiments involving warming, defoliation, and variation in other factors (e.g., precipitation).