Short‐term effects of sheep excrement on carbon dioxide, nitrous oxide and methane fluxes in typical grassland of Inner Mongolia

Abstract

Excrement patches of grazing animals play an important role in greenhouse gas (GHG) fluxes due to the high nitrogen (N) and available carbon (C) deposited in small areas, but little information is available for the effect of excrement in the Inner Mongolian grassland (43°26 N, 116°40 E). To elucidate the effect of grazing sheep urine, fresh dung and compost on fluxes of methane (CH 4 ), carbon dioxide (CO 2 ), and nitrous oxide (N 2 O), a short-term field study (65 days) was carried out in the typical grassland of Inner Mongolia with the optimised closed chamber/GC technique. Compared with the control, cumulative net CH 4 consumption decreased 36, 31, and 18% from urine, fresh dung, and compost plots, respectively; net CO 2 -C output increased by 6.5, 1.5, and 1.2% from urine, fresh dung, and compost treated soil, respectively; about three times as much N 2 O-N was emitted from urine and the fresh dung treatments during 65 days. Nitrous oxide emission was positively correlated with CO 2 emission (R = 0.691, P < 0.01) and water-filled pore space (R = 0.698, P < 0.01). The percentages of N 2 O-N loss of applied-N were 0.44 and 1.05% for urine and fresh dung, respectively. Our results suggest that in autumn in the degraded grassland of Inner Mongolia, the effect of sheep excrement may be ignored when evaluating the total GHG emissions.

Soil methane uptake by grasslands and forests in China

“…More than three fourths of all published measurements from grasslands of China were taken in the semi-arid steppe ecoregion of the NASD. Based on 306 data collected in this region we estimated the mean CH 4 uptake rate by grasslands as 74.31 AE 62.51 mg CH 4 m À2 h À1 Wang et al, 1998Wang et al, , 2000Wang et al, , 2005Ma et al, 2006;Liu et al, 2007Liu et al, , 2009aGeng et al, 2010;Zhou and Hao, 2010;Luo and Jiao, 2012), which is also the highest mean CH 4 uptake rate of grasslands for all ecoregions in China (Fig. 2).…”

“…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).…”

“…However, Wang et al (2000) found that there was no significant variation of CH 4 uptake under different grazing densities. Excrement patches of grazing animals also play an important role in significantly decreasing CH 4 uptake (Ma et al, 2006;Lin et al, 2009). CH 4 uptake was also substantially influenced by mowing through its effect on some biotic factors (such as net primary productivity, soil microbial C/N supply and soil microbial activities) not on soil temperature nor moisture .…”

“…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).…”

Methane Emission from Sheep Respiration and Sheepfolds During the Grazing Season in a Desert Grassland

“…However, our result was lower than the mean flux in summer sheepfolds in Chen et al [27], because our measurement did not include the flux of new feces (which were cleaned out in our study) was the direct reason. Many studies had reported pronounced and short pulses of CH 4 emission immediately following application of fresh animal excreta [28,29] and livestock can be an important source of CH 4 through direct enteric emissions and decomposition of excreta deposited on grassland [30,31]. Chen et al [27] also reported that the annual budget from sheepfolds in Inner Mongolia is mainly driven by emissions during the growing season, with most of these emissions occurring in the summer sheepfold.…”