Effects of Mowing on Methane Uptake in a Semiarid Grassland in Northern China

Background: Mowing is a widely adopted management practice for the semiarid steppe in China and affects CH4 exchange. However, the magnitude and the underlying mechanisms for CH 4 uptake in response to mowing remain uncertain. Methodology/Principal Findings: In two consecutive growing seasons, we measured the effect of mowing on CH 4 uptake in a steppe community. Vegetation was mowed to 2 cm (M2), 5 cm (M5), 10 cm (M10), 15 cm (M15) above soil surface, respectively, and control was set as non-mowing (NM). Compared with control, CH4 uptake was substantially enhanced at almost all the mowing treatments except for M15 plots of 2009. CH4 uptake was significantly correlated with soil microbial biomass carbon, microbial biomass nitrogen, and soil moisture. Mowing affects CH 4 uptake primarily through its effect on some biotic factors, such as net primary productivity, soil microbial C\N supply and soil microbial activities, while soil temperature and moisture were less important. Conclusions/Significance: This study found that mowing affects the fluxes of CH4 in the semiarid temperate steppe of north China

Interactive impacts of nitrogen input and water amendment on growing season fluxes of CO2, CH4, and N2O in a semiarid grassland, Northern China

Nitrogen and water are two important factors influencing GHG (primarily CO2 - carbon dioxide; CH4 - methane, and N2O - nitrous oxide) fluxes in semiarid grasslands. However, the interactive effects of nitrogen and water on GHG fluxes remain elusive. A 3-year (2010-2012) manipulative experiment was conducted to investigate the individual and interactive effects of nitrogen and water additions on GHG fluxes during growing seasons (May to September) in a semiarid grassland in Northern China. Accumulated throughout growing seasons, nitrogen input stimulated CO2 uptake by 33 +/- 1.0 g C m(-2) (g N)(-1), enhanced N2O emission by 1.2 +/- 0.3 mg N m(-2) (g N)(-1), and decreased CH4 uptake by 5.2 +/- 0.9 mg N m(-2) (g N)(-1); water amendment stimulated CO2 uptake by 0.2 +/- 0.1 g Cm-2 (mm H2O)(-1) and N2O emission by 0.2 +/- 0.02 mg N m(-2) (mm H2O)(-1) , decreased CH4 uptake by 0.3 +/- 0.1 mg C m(-2) (mm H2O)(-1). A synergistic effect between nitrogen and water was found on N2O flux in normal year while the additive effects of nitrogen and water additions were found on CH4 and CO2 uptakes during all experiment years, and on N2O-emission in dry years. The nitrogen addition had stronger impacts than water amendment on stimulating CH4 uptake in the normal year, while water was the dominant factor affecting CH4 uptake in dry years. For N2O emission, the N-stimulating impact was stronger in un-watered than in watered plots, and the water-stimulating impact was stronger in non-fertilized than in fertilized treatments in dry years. The interactive impacts of nitrogen and water additions on GHG fluxes advance our understanding of GHG fluxes in responses to multiple environmental factors. This data source could be valuable for validating ecosystem models in simulating GHG fluxes in a multiple factors environment. (C) 2016 Elsevier B.V. All rights reserved

Interactive impacts of nitrogen input and water amendment on growing season fluxes of CO2, CH4, and N2O in a semiarid grassland, Northern China

Nitrogen and water are two important factors influencing GHG (primarily CO2 - carbon dioxide; CH4 - methane, and N2O - nitrous oxide) fluxes in semiarid grasslands. However, the interactive effects of nitrogen and water on GHG fluxes remain elusive. A 3-year (2010-2012) manipulative experiment was conducted to investigate the individual and interactive effects of nitrogen and water additions on GHG fluxes during growing seasons (May to September) in a semiarid grassland in Northern China. Accumulated throughout growing seasons, nitrogen input stimulated CO2 uptake by 33 +/- 1.0 g C m(-2) (g N)(-1), enhanced N2O emission by 1.2 +/- 0.3 mg N m(-2) (g N)(-1), and decreased CH4 uptake by 5.2 +/- 0.9 mg N m(-2) (g N)(-1); water amendment stimulated CO2 uptake by 0.2 +/- 0.1 g Cm-2 (mm H2O)(-1) and N2O emission by 0.2 +/- 0.02 mg N m(-2) (mm H2O)(-1) , decreased CH4 uptake by 0.3 +/- 0.1 mg C m(-2) (mm H2O)(-1). A synergistic effect between nitrogen and water was found on N2O flux in normal year while the additive effects of nitrogen and water additions were found on CH4 and CO2 uptakes during all experiment years, and on N2O-emission in dry years. The nitrogen addition had stronger impacts than water amendment on stimulating CH4 uptake in the normal year, while water was the dominant factor affecting CH4 uptake in dry years. For N2O emission, the N-stimulating impact was stronger in un-watered than in watered plots, and the water-stimulating impact was stronger in non-fertilized than in fertilized treatments in dry years. The interactive impacts of nitrogen and water additions on GHG fluxes advance our understanding of GHG fluxes in responses to multiple environmental factors. This data source could be valuable for validating ecosystem models in simulating GHG fluxes in a multiple factors environment. (C) 2016 Elsevier B.V. All rights reserved

Effects of Multi-nutrient Additions on GHG Fluxes in a Temperate Grassland of Northern China

Human activities have substantially enhanced the availability of important nutrient elements such as nitrogen (N), phosphorus (P), and potassium (K) in ecosystems worldwide. However, how the concurrent increase in all of these nutrients will affect greenhouse gas (that is, CO2, N2O, CH4) levels remains unknown. In a temperate steppe of northern China, a 2-year field experiment was conducted to examine the effects of multi-nutrient additions on GHG fluxes from 2009 to 2010. Four levels of annual nutrient loads were mimicked: 0 g NPK (control), 15.5 g P m(-2) and 19.5 g K m(-2) as KH2PO4 (PK), 10 g N m(-2) as NH4NO3 plus PK (10N + PK), and 20 g N m(-2) plus PK (20N + PK) per year. The results show that multi-nutrient additions led to significant increases in net primary production (NPP) and soil temperature (ST), a significant decrease in soil moisture (SM) in 2010, and no significant changes in other soil parameters. Seasonal patterns differed greatly for different GHG fluxes in response to different nutrient treatments, largely as a result of differences in influential factors. The 10N + PK treatment significantly increased CO2 uptake, whereas the 20N + PK treatment significantly decreased CO2 uptake. The application of P and K without additional N significantly enhanced CH4 uptake, whereas the two N + PK treatments significantly enhanced N2O emissions. Significant positive, linear relationships were found between cumulative CO2 uptake and soil total nitrogen (TN), microbial biomass carbon, and microbial biomass nitrogen, whereas significant negative, linear relationships were found with NPP, SM, and the C/N ratio. Significant positive, linear relationships were found between cumulative N2O emission and ST, TN, NPP, and total organic carbon, whereas no relationships were found between cumulative CH4 uptake and any soil parameters. CO2 flux was related to N2O flux temporally, to a certain extent, for all the treatments. In the control, N2O flux showed a negative, linear relationship with CH4 flux, whereas no regular relationships were detected between CO2 and CH4 fluxes in any treatment. Our findings imply that increasing nutrient deposition will change the magnitude, patterns, and relationships among GHG uptakes and emissions in the future

Results (P values) of repeated measures ANOVAs on the effects of mowing (M), sampling date (D), and their interactions on soil temperature (ST), soil moisture (SM), soil microbial biomass carbon (MBC), soil microbial biomass nitrogen (MBN) and CH₄ uptake rate in all the mowing treatments.

<p>Results (P values) of repeated measures ANOVAs on the effects of mowing (M), sampling date (D), and their interactions on soil temperature (ST), soil moisture (SM), soil microbial biomass carbon (MBC), soil microbial biomass nitrogen (MBN) and CH₄ uptake rate in all the mowing treatments.</p

Dependence of seasonal variation in CH₄ uptake on soil moisture (SM), microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN).

<p>Dependence of seasonal variation in CH₄ uptake on soil moisture (SM), microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN).</p

Effects of Mowing Heights on N 2 O Emission from Temperate Grasslands in Inner Mongolia

Abstract Grazing and mowing are two common practices for grassland management. Mowing is now recommended as an alternative to the traditional grazing for grassland conservation in Inner Mongolia, northern China. Many studies have revealed that mowing may alter ecosystem properties in various ways. However, little attention has been paid to the effect of mowing on trace gas emissions, especially on N2O flux. We conducted an experiment to investigate the effects of mowing on N2O fluxes from the semiarid grassland in Inner Mongolia. The mowing experiment, which started in 2003, comprised four mowing intensity treatments, i.e. mowing heights at 2 cm, 5 cm, 10 cm and 15 cm above the soil surface, respectively, and a control (non-mowing), with five replicates. Gas fluxes were measured through a closed static chamber technique during the growing seasons (usually from May to September, depending on local climate at the time) of 2008 and 2009, respectively. Our results showed that mowing decreased N2O emissions, above-ground biomass and total litter production. N2O emissions were greater in May and June than in other sampling periods, regardless of treatments (P &lt; 0.05). A co-relationship analysis suggested that variations in seasonal N2O fluxes were mainly driven by variations in soil moisture, except in July and August. In July and August, above-ground plant biomass and soil total nitrogen became the major drivers of N2O fluxes under the soil temperatures between 16˚C and 18˚C. Though there were some uncertainties due to the low frequency of N2O flux measurement, our study mainly indicated that 5 cm mowing height might decrease N2O emissions in grasslands during the growing season, and soil * The first common authors. # Corresponding author. L. H. Zhang et al. 398 properties affected the magnitude of the reduction

Dependence of seasonal cumulative CH₄ uptake on the net aboveground primary productivity (ANPP, g m⁻²).

<p>Dependence of seasonal cumulative CH₄ uptake on the net aboveground primary productivity (ANPP, g m⁻²).</p

Mowing-induced changes in seasonal mean CH₄ uptake rate and seasonal mean microbial biomass carbon (MBC).

<p>Mowing-induced changes in seasonal mean CH₄ uptake rate and seasonal mean microbial biomass carbon (MBC).</p