Abstract
Abstract. Soil respiration (Rs) is the most important source of carbon dioxide emissions from soil to atmosphere. However, it is unclear what the interactive response of Rs would be to environmental changes such as elevated precipitation, nitrogen (N) deposition and warming, especially in unique temperate desert ecosystems. To investigate this an in situ field experiment was conducted in the Gurbantunggut Desert, northwest China, from September 2014 to October 2016. The results showed that precipitation and N deposition significantly increased Rs, but warming decreased Rs, except in extreme precipitation events, which was mainly through its impact on the variation of soil moisture at 5 cm depth. In addition, the interactive response of Rs to combinations of the factors was much less than that of any single-factor, and the main response was a positive effect, except for the response from the interaction of increased precipitation and high N deposition (60 kg N ha−1 yr−1). Although Rs was found to show a unimodal change pattern with the variation of soil moisture, soil temperature and soil NH4+-N content, and it was significantly positively correlated to soil dissolved organic carbon (DOC) and pH, a structural equation model found that soil temperature was the most important controlling factor. Those results indicated that Rs was mainly interactively controlled by the soil multi-environmental factors and soil nutrients, and was very sensitive to elevated precipitation, N deposition and warming. However, the interactions of multiple factors largely reduced between-year variation of Rs more than any single-factor, suggesting that the carbon cycle in temperate deserts could be profoundly influenced by positive carbon–climate feedback.
Highlights
Global climate warming, changes in precipitation patterns and increased atmospheric nitrogen (N) deposition have all occurred since the Industrial Revolution, especially in temperate regions (IPCC, 2013), which will be expected to significantly change soil respiration (Rs), the most important source of carbon dioxide (CO2) from soil to atmosphere (Wu et al, 2011): the annual CO2 flux from Rs was 10-fold that of fossil fuel emissions (Eswaran et al, 1993; Batjes, 1996; Gougoulias et al, 2014)
Soil microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) were greatly increased by N deposition, but significant negative effects on soil MBC and MBN were observed by warming and the interaction of precipitation and N deposition (Fig. 1d)
This is because the growth of desert plants and microbial activity are significantly activated by increasing precipitation (Huang et al, 2015a), and microbial biomass, mass-specific respiration, microbial biomass carbon (MBC) and nitrogen (MBN), and microbial PLFAs were consistently significantly enhanced by increased precipitation (Zhang et al, 2013; Huang et al, 2015a)
Summary
Changes in precipitation patterns and increased atmospheric nitrogen (N) deposition have all occurred since the Industrial Revolution, especially in temperate regions (IPCC, 2013), which will be expected to significantly change soil respiration (Rs), the most important source of carbon dioxide (CO2) from soil to atmosphere (Wu et al, 2011): the annual CO2 flux from Rs was 10-fold that of fossil fuel emissions (Eswaran et al, 1993; Batjes, 1996; Gougoulias et al, 2014). A number of experiments of the effects of warming, precipitation and N deposition on Rs have been conducted in alpine grasslands, tundra regions, peatlands and temperate forests (Lafleur and Humphreys, 2008; Strong et al, 2017; Yang et al, 2017; Zhao et al, 2017), studies in temperate desert ecosystems are scarce, especially those on the impact of these changes’ interactions on Rs. A field study of multi-factor interactive effects on Rs was conducted in a temperate desert ecosystem to help in understanding the response of Rs to climate. Yue et al.: Responses of Rs to precipitation warming and nitrogen deposition in temperate desert change and N deposition in future and highlight the main driving factors
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