Culturable autotrophic ammonia-oxidizing bacteria population and nitrification potential in a sheep grazing intensity gradient in a grassland on the Loess Plateau of Northwest China

2011 ◽  
Vol 91 (6) ◽  
pp. 925-934 ◽  
Author(s):  
Tianzeng Liu ◽  
Zhibiao Nan ◽  
Fujiang Hou
Keyword(s):  
Loess Plateau ◽  
Soil Depth ◽  
Grazing Intensity ◽  
Northwest China ◽  
Ammonia Oxidizing Bacteria ◽  
Stocking Rate ◽  
The Loess Plateau ◽  
Soil Microbial ◽  
Nitrification Potential ◽  
Dry Soil

Liu, T., Nan, Z. and Hou, F. 2011. Culturable autotrophic ammonia-oxidizing bacteria population and nitrification potential in a sheep grazing intensity gradient in a grassland on the Loess Plateau of Northwest China. Can. J. Soil Sci. 91: 925–934. Grazing is known to enhance the activity of soil microbial communities in many types of grasslands; however, the potential impacts of rotational grazing activity on soil microbial functional groups remain poorly understood. We investigated the effects of 9 yr of rotational grazing by livestock on culturable autotrophic ammonia-oxidizing bacteria (AOB) population size, nitrification potential and soil properties in a semi-arid grassland of the Loess Plateau in Northwest China. Three stocking rate treatments of 2.7, 5.3 and 8.7 wether lambs ha−1were evaluated in geographically separated paddocks. Grazing increased nitrification potential and culturable AOB populations compared with ungrazed treatments. Ammonia-oxidizing bacteria populations increased from 155 bacteria g−1dry soil with 0 sheep ha−1to 16 218 bacteria g−1dry soil with 8.7 sheep ha−1. Grazing led to an increase in population of AOB at 0–10 cm soil depth, but had no effect on AOB at 10–20 cm soil depth. Nitrification potential increased from 1.21 mg NO3-N kg−1soil d−1in ungrazed treatments to 2.86 mg NO3-N kg−1soil d−1at the highest stocking rate. Soil ammonium and nitrate concentrations increased; however, total soil nitrogen and soil moisture content decreased with increased stocking rate for both sampling depths (0–10 cm and 10–20 cm). Soil organic matter was not affected by grazing treatments. Soil nitrification potential and the size of culturable AOB populations were dependent on grazing intensity, soil depth and season. This information is potentially important for the optimal selection of stocking rate for grazed ecosystems.

Stocking rate effects on metabolizable energy intake and grazing behaviour of Tan sheep in steppe grassland on the Loess Plateau of Northwest China

2010 ◽  
Vol 148 (6) ◽  
pp. 709-721 ◽  
Author(s):  
X. J. CHEN ◽  
F. J. HOU ◽  
C. MATTHEW ◽  
X. Z. HE
Keyword(s):  
Loess Plateau ◽  
Northwest China ◽  
Metabolizable Energy ◽  
Stocking Rate ◽  
The Loess Plateau ◽  
Height Range ◽  
Grazing System ◽  
Grazing Systems ◽  
Grazing Period ◽  
Grazing Behaviour

SUMMARYA simulated grazing system was set up in Huanxian County, Gansu province, on the Loess Plateau of Northwest China, involving the purchase of 18-month-old wether lambs in June of each year at c. 20 kg body weight (BW) and sale 6 months later at c. 35 kg BW. Three stocking rate (SR) treatments of 2·7, 5·3 and 8·7 wether lambs/ha were evaluated on geographically separated warm season (WS) and cold season (CS) paddocks c. 1 km apart; 3 years' data are reported (2004–2006). The metabolizable energy (ME) yield of the grazing system, calculated from the weight of animals fed and their weight gain, averaged 1·7, 3·3 and 4·7 GJ/ha/year for 2004, 2005 and 2006, respectively, in the WS and 0·9, 1·9, and 2·7 GJ/ha/year, respectively, in the CS for SR of 2·7, 5·3 and 8·7 animals/ha. Detailed grazing behaviour records were kept in order to elucidate intake dynamics. In these grazing systems, bite weight was typically c. 0·04 g/bite, lower than for temperate grazing systems at comparable herbage mass. A hypothesis for further study is proposed that this may relate to the distribution of a similar herbage mass over a greater sward height range in steppe vegetation than in temperate grass pasture. Sheep increased their bite rate (bites/min) and the number of steps/min at higher SR to compensate, such that intake/animal was reduced by not more than 10% with a threefold increase in SR. At higher SR, herbage ground cover on grazed plots was still lower than on ungrazed plots, 1 year after a 90-day summer grazing period or a 48-day winter grazing period. The significance of the findings for management of these systems is briefly discussed.

scholarly journals Vegetation Response to Goats Grazing Intensity in Semiarid Hilly Grassland of the Loess Plateau, Lanzhou, China

2021 ◽  
Vol 13 (6) ◽  
pp. 3569
Author(s):  
Hua Cheng ◽  
Baocheng Jin ◽  
Kai Luo ◽  
Jiuying Pei ◽  
Xueli Zhang ◽  
...  
Keyword(s):  
Growth Rate ◽  
Community Structure ◽  
Plant Growth ◽  
Loess Plateau ◽  
Grazing Intensity ◽  
Gps Tracking ◽  
Growth Stages ◽  
The Loess Plateau ◽  
Vegetation Community ◽  
Natural Grasslands

Quantitatively estimating the grazing intensity (GI) effects on vegetation in semiarid hilly grassland of the Loess Plateau can help to develop safe utilization levels for natural grasslands, which is a necessity of maintaining livestock production and sustainable development of grasslands. Normalized difference vegetation index (NDVI), field vegetation data, and 181 days (one goat per day) of GPS tracking were combined to quantify the spatial pattern of GI, and its effects on the vegetation community structure. The spatial distribution of GI was uneven, with a mean value of 0.50 goats/ha, and 95% of the study area had less than 1.30 goats/ha. The areas with utilization rates of rangeland (July) lower than 45% and 20% made up about 95% and 60% of the study area, respectively. Grazing significantly reduced monthly aboveground biomass, but the grazing effects on plant growth rate were complex across the different plant growth stages. Grazing impaired plant growth in general, but the intermediate GI appeared to facilitate plant growth rate at the end of the growing seasons. Grazing had minimal relationship with vegetation community structure characteristics, though Importance Value of forbs increased with increasing GI. Flexibility in the number of goats and conservatively defining utilization rate, according to the inter-annual variation of utilization biomass, would be beneficial to achieve ecologically healthy and economically sustainable GI.

scholarly journals Earthworm Burrowing Activity and Its Effects on Soil Hydraulic Properties under Different Soil Moisture Conditions from the Loess Plateau, China

2020 ◽  
Vol 12 (21) ◽  
pp. 9303
Author(s):  
Shuhai Wen ◽  
Ming’an Shao ◽  
Jiao Wang
Keyword(s):  
Soil Moisture ◽  
Loess Plateau ◽  
Hydraulic Properties ◽  
Soil Depth ◽  
Soil Aggregates ◽  
Field Capacity ◽  
Soil Hydraulic Properties ◽  
The Loess Plateau ◽  
Burrowing Activity ◽  
Soil Hydraulic

Earthworm activity has become more important in the Loess Plateau, where hydrological processes are crucial for ecosystem sustainability. In this study, we conducted a laboratory microcosm experiment to determine the various burrowing activities of Eisenia fetida and their impact on the soil hydraulic properties in response to different levels of soil moisture (50%, 70%, 90% of field capacity) in two common soil types (loessial and Lou soil) obtained from the Loess Plateau. Burrowing activity of E. fetida increased with higher soil moisture and was greater in loessial than in Lou soil. Most burrowing activities occurred within the top 5 cm and decreased with increasing soil depth. Macropores and burrow branching, which are highly related to the earthworm burrowing, were more prevalent in wetter soil. Earthworms significantly altered the formation of large soil aggregates (AGL, diameter >2 mm) under different soil moistures and depths. Distinct earthworm burrowing activities, controlled by soil moisture, altered soil hydraulic properties. However, soil saturated hydraulic conductivity (Ks) showed little differences between different treatments due to the horizontal and high–branched burrows of E. fetida, although higher burrowing activities were found in wetter soil. Soil field capacity was highest in drier soil due to the less macropores and burrowing activities.

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