Enclosure Rather Than Topography Enhances the Soil Ecological Stoichiometry in Typical Steppe on the Loess Plateau, China

Grassland is one of the largest terrestrial ecosystems in the world, a large part of which is distributed in varied topography. And grazing and enclosure are the main ways to use this part. Grazing changes the soil structure through feeding, trampling and excreta return, thus affects the soil nutrients. The aspect mainly affects soil temperature and moisture by affecting solar radiation. The slope affects soil nutrients by affecting surface runoff. Water and temperature are the main factors affecting soil nutrients. We carried out to explore the effect of enclosure years and topography on soil ecological stoichiometry. The results showed that: soil organic carbon density, soil nitrogen density and soil phosphorus density increased with the increasing enclosure years and decreased with the increasing slope. Soil N/P (ratio between soil nitrogen density and soil phosphorus density) increased with increasing the enclosure years and the slope while soil C/N (ratio between soil organic carbon density and soil nitrogen density) decreased. Soil C/P (ratio between soil organic carbon density and soil phosphorus density) increased with the increasing enclosure years, however the trend with slope change was not obvious. The enclosure of sunny slope is more beneficial to soil nutrient accumulation

Fe and MN Concentrations in Plants Correlated Negatively With Air Temperature Precipitation in Three Types of Grassland

Alpine meadows, typical steppe, and deserts are globally important grassland ecosystems. We investigated the seasonal trends in Fe and Mn concentrations in the dominant species and community of plants from diverse grassland types in northwest China. It was found that seasonal Fe and Mn concentrations in most plant species were negatively correlated with seasonal precipitation, biomass, and temperature. Additionally, seasonal Cu concentrations in Reaumuria soongorica was significantly correlated with seasonal precipitation. The seasonal mean temperature explained more of the seasonal variation of the Fe and Mn concentrations in the plant community of these grasslands than precipitation, except for the concentrations of Mn in typical steppe vegetation. However, there was almost no significant correlation between these factors and the seasonal Cu and Zn concentrations. These results provided a scientific basis for the assessment of plant trace elements in alpine meadows, typical steppes, and deserts around the world

Dietary supplementation of Allium mongolicum modulates rumen-hindgut microbial community structure in Simmental calves

Compared to traditional herbage, functional native herbage is playing more important role in ruminant agriculture through improving digestion, metabolism and health of livestock; however, their effects on rumen microbial communities and hindgut fermentation are still not well understood. The objective of present study was to evaluate the effects of dietary addition of Allium mongolicum on bacterial communities in rumen and feces of claves. Sixteen 7-month-old male calves were randomly divided into four groups (n = 4). All calves were fed a basal ration containing roughage (alfalfa and oats) and mixed concentrate in a ratio of 60:40 on dry matter basis. In each group, the basal ration was supplemented with Allium mongolicum 0 (SL0), 200 (SL200), 400 (SL400), and 800 (SL800) mg/kg BW. The experiment lasted for 58 days. Rumen fluid and feces in rectum were collected, Rumen fluid and hindgut fecal were collected for analyzing bacterial community. In the rumen, Compared with SL0, there was a greater relative abundance of phylum Proteobacteria (p < 0.05) and genera Rikenellaceae_RC9_gut_group (p < 0.01) in SL800 treatment. In hindgut, compared with SL0, supplementation of A. mongolicum (SL200, SL400, or SL800) decreased in the relative abundances of Ruminococcaceae_UCG-014 (p < 0.01), Ruminiclostridium_5 (p < 0.01), Eubacterium_coprostanoligenes_group (p < 0.05), and Alistipes (p < 0.05) in feces; Whereas, the relative abundances of Christensenellaceae_R-7_group (p < 0.05), and Prevotella_1 (p < 0.01) in SL800 were higher in feces, to maintain hindgut stability. This study provided evidence that A. mongolicum affects the gastrointestinal of calves, by influencing microbiota in their rumen and feces

Herbicide applications increase greenhouse gas emissions of alfalfa pasture in the inland arid region of northwest China

Herbicides are used to control weeds in agricultural crops such as alfalfa (Medicago sativa L.), which is a forage crop. It is unclear what, if any, effect herbicides have on greenhouse gas (GHG) emissions when used on alfalfa. Our study was conducted in 2017 and 2018 to investigate the effects of two herbicides (Quizalofop-p-ethyl, QE and Bentazone, BT) on methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O) emissions from soil planted with alfalfa. QE is used to control grasses and BT is used for broadleaf weed control. Soil CO2 emissions and soil uptake of CH4 increased significantly in both years following the QE and BT treatments, although CO2 emissions differed significantly between the trial years. N2O emissions decreased relative to the control and showed no significant differences between the trial years. The application of QE and BT on alfalfa resulted in a significant increase in CO2 emissions which contributed to a significant increase in GHG emissions. The application of QE influenced GHG emissions more than BT. We demonstrated the potential effect that herbicide applications have on GHG fluxes, which are important when considering the effect of agricultural practices on GHG emissions and the potential for global warming over the next 100 years

Multi-Scale Evaluation of Dominant Factors (MSDF) on Forage: An Ecosystemic Method to Understand the Function of Forage

Grassland agroecosystem plays a key role on resource cycling and sustainability of global ecosystem. Forage is the basic factor and core of the grassland agroecosystem. At a single scale, the most of forage evaluation remain in a state of qualitative or quantitative evaluation, and lack a series of quantitative evaluation at multi spatial scales and influence of society, environment and economy. This study collected dominant indicators at micro, plot, farm, ecoregional and macro scales to compile a systemic evaluation of forage in agroecosystems. A case study is presented for forage evaluation by using plot, farm, and regional data from an arid region of Gansu, China. Multi-scale evaluation of dominant factors (MSDF) was used to aggregate forage evaluation indicators. Results showed that the scale of evaluation had significant effects on the results of the evaluation. The evaluation results of the single index for the same forage species among plot, farm and ecoregional scales were different. Results implied that forage MSDF are needed to guide the evaluation of forage and then production of forage and herbivore in the future. An appropriate scale of evaluation could be selected in term of the forage production objectives and moreover, MSDF evaluation of forage should be used to improve the environmental, social and productive evaluation of forage in a grassland agroecosystems

Optimizing alfalfa productivity and persistence versus greenhouse gases fluxes in a continental arid region

Alfalfa in China is mostly planted in the semi-arid or arid Northwest inland regions due to its ability to take up water from deep in the soil and to fix atmospheric N2 which reduces N fertilizer application. However, perennial alfalfa may deplete soil water due to uptake and thus aggravate soil desiccation. The objectives of this study were (1) to determine the alfalfa forage yield, soil property (soil temperature (ST), soil water content (SWC), soil organic carbon (SOC) and soil total nitrogen (STN)) and greenhouse gas (GHG: methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2)) emissions affected by alfalfa stand age and growing season, (2) to investigate the effects of soil property on GHG emissions, and (3) to optimize the alfalfa stand age by integrating the two standard criteria, the forage yield and water use efficiency, and the total GHG efflux (CO2-eq). This study was performed in alfalfa fields of different ages (2, 3, 5 and 7 year old) during the growing season (from April to October) in a typical salinized meadow with temperate continental arid climate in the Northwest inland regions, China. Despite its higher total GHG efflux (CO2-eq), the greater forage yield and water use efficiency with lower GEIhay and high CH4 uptake in the 5-year alfalfa stand suggested an optimal alfalfa stand age of 5 years. Results show that ST, SOC and RBM alone had positive effects (except RBM had no significant effect on CH4 effluxes), but SWC and STN alone had negative effects on GHG fluxes. Furthermore, results demonstrate that in arid regions SWC superseded ST, SOC, STN and RBM as a key factor regulating GHG fluxes, and soil water stress may have led to a net uptake of CH4 by soils and a reduction of N2O and CO2 effluxes from alfalfa fields. Our study has provided insights into the determination of alfalfa stand age and the understanding of mechanisms regulating GHG fluxes in alfalfa fields in the continental arid regions. This knowledge is essential to decide the alfalfa retention time by considering the hay yield, water use efficiency as well as GHG emission