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

Abstract

BackgroundMowing is a widely adopted management practice for the semiarid steppe in China and affects CH4 exchange. However, the magnitude and the underlying mechanisms for CH4 uptake in response to mowing remain uncertain.Methodology/Principal FindingsIn two consecutive growing seasons, we measured the effect of mowing on CH4 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 CH4 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/SignificanceThis study found that mowing affects the fluxes of CH4 in the semiarid temperate steppe of north China.

Soil methane uptake by grasslands and forests in China

“…Similar with other studies all over the world (Dengel et al, 2011;Imer et al, 2013), the maximum uptake rate is usually observed in the afternoon due to the warmest soil condition during the day (Wang et al, 2003a;Du et al, 2005;Kato et al, 2013), except for a few reporting peak values at other times Dong et al, 2000;Qi et al, 2004). Typical seasonal patterns have been found in Inner Mongolia Wang et al, 1998Wang et al, , 2000Wang et al, , 2003aDu et al, 2005;Chen et al, 2010;Zhang et al, 2012) and on the Qinghai-Tibetan Plateau (Pei et al, 2003;Wang et al, 2009a), with larger uptake rates in summer and lower rates in winter (Liu et al, 2007;Holst et al, 2008;Chen et al, 2010 À1 based on 65 data) (P < 0.01), similar to the results of Wang et al (2005) due to warming condition in growing season enhancing activities of methanotrophs. The dominant factors for seasonal variation of CH 4 uptake are soil temperature and soil moisture (Jiang et al, 2010).…”

“…Thus, livestock grazing may have been the most important management of grasslands on both domains. Grazing was found to have complicated effects on CH 4 uptakes by grasslands, probably due to different grazing density and grazing patterns, or accompanied by difference of weather conditions and vegetation Wang et al, 2000;Wang et al, 2001Wang et al, , 2003bQi et al, 2003;Ma et al, 2006;Li et al, 2007;Liu et al, 2007Liu et al, , 2012cLin et al, 2009;Wan et al, 2010;Zhou and Hao, 2010;Zhou et al, 2011;Jiang et al, 2012;Zhang et al, 2012). In both semi-arid steppe ecoregion and alpine steppe and meadow ecoregion, the CH 4 uptake rate of freely grazed grasslands was lower than that of fenced grasslands (Table 1), partly due to grazing-induced changes in soil bulk density by tramping, soil nutrient and biomass allocation Qi et al, 2003;Wang et al, 2003b;Liu et al, 2007) based on 10 data).…”

“…So far to the best of our knowledge, there is no synthesis study on a comprehensive CH 4 budget for either grasslands or forests in China, which is indispensable for a general CH 4 uptake estimate for this country. Multiple studies on CH 4 fluxes of grasslands in China have already been carried out Wang et al, 1998Wang et al, , 2000Wang et al, , 2005Wang et al, , 2007Wang et al, , 2009bDong et al, 2000Dong et al, , 2005Ma et al, 2006;Li et al, 2007;Liu et al, 2007Liu et al, , 2011Liu et al, , 2012aHolst et al, 2008;Sun, 2008;Chen et al, 2010;Geng et al, 2010;Zhou et al, 2011;Luo and Jiao, 2012;Wei et al, 2012;Zhang et al, 2012), some even making efforts to estimate the total emission for specific regions Liu et al, 2009a;Wang et al, 2009c). Relatively fewer studies on CH 4 fluxes of forests in China have been published (Xu et al, 1995;Sun, 2000;Dong et al, 2003;Du et al, 2004;Mo et al, 2005;Yang et al, 2010;Liu et al, 2010bLiu et al, , 2012bGuan et al, 2012;Yang, 2012).…”

Effects of Mowing Heights on N&lt;sub&gt;2&lt;/sub&gt;O Emission from Temperate Grasslands in Inner Mongolia, Northern China

“…Soil temperature and moisture varied seasonally at this site (see Ref. [20]). Briefly, soil temperature at 5 cm depth ranged from 13.1˚C to 31.1˚C with an average of 22.3˚C in 2008, 8.5˚C to 27.9˚C with an average of 18.1˚C in 2009.…”

“…N 2 O reduction by denitrifying microorganism is associated with reduced levels of oxygen, which is usually related to increased moisture contents [26]. Despite the different patterns of N 2 O fluxes in July 2008 and 2009, soil moisture contents were not significantly different between these months [20]. Hence, unknown soil factors might have been responsible for the observed differences in the fluxes in July.…”