Influences of various grazing systems on community biomass of a desert grassland in Inner Mongolia,China

This study investigated the effects of various grazing systems, including continuous grazing, rotational grazing, and no-grazing systems, on the community biomass in the Stipa breviflora Griseb desert grassland during the grazing seasons in 2005, 2006, and 2007, based on study sites established in 1999. We found that the seasonal dynamics of the aboveground biomass were quite similar among the three treatments, which reached peak values in period from August to September during each study year. The continuous grazing system reduced the aboveground biomass from 2005 to 2007 under drought conditions, and the rotational grazing and no-grazing systems maintained more aboveground biomass than the continuous grazing system did. The belowground biomass declined with the increase of soil depth among the three treatments, and in the surface 20-cm soil layer it accounted for more than 60% of the total biomass. The belowground biomass was found to be highly correlated with soil depth under rotational grazing. The total belowground biomass within the 0--100-cm soil layer for rotational grazing was sig- nificantly higher than for continuous grazing and no-grazing, and had 15,775 kg/ha more biomass. Our results demonstrate that conservative rotational grazing can alleviate grassland deterioration by reserving more aboveground and belowground biomass than the continuous grazing system does.

Effects of the grazing systems on germinable soil seed bank of desert steppe

We studied a soil seed bank in the Stipa breviflora desert steppe under three grassland management systems, namely continuous grazing, rotational grazing, and no grazing, from 1999 until 2007. The germinable seed bank species in rotational, continuous and no gazing were 11, 9 and 8 species, respectively. Rotational grazing increased the number of seed bank plant species and perenni- al grasses. The density of germinal soil seed bank was significantly higher in the enclosed area （19,533.33 seeds/m2） than those in rotational （3,233.33 seeds/mz） and continuous grazing areas （2,553.60 seeds/m2）. The vertical distribution of the soil seed bank had a similar trend： 75.06%-83.19% of the seeds are distributed in the top 0-5 cm soil layer, 14.16%-21.68% in the 5-10 cm lay- er, and 2.65%-4.95% in the 10-15 cm layer, which varied between the grazing treatments. Density of the soil seed bank was sig- nificantly higher in the enclosed area, and there was no significant difference between rotational and continuous grazing. The Margalef and Shannon-Wiener indices for the soil seed bank were higher for rotational grazing treatment than for continuous grazing. The Sorensen＇s similarity index for the soil seed bank between the enclosed and rotational grazing areas reached 0.857.

Litter mixing significantly affects decomposition in the Hulun Buir meadow steppe of Inner Mongolia, China

Aims We explored the decomposition rates of single-and mixed-species litter,the litter-mixing effect and the effect of component litters in a mixture on decomposition.Methods In a litter bag experiment,shoot litters from two dominant grasses(Leymus chinensis and Stipa baicalensis)and one legume(Melissitus ruthenica)were decomposed separately and as a mixture from May 2010 to September 2011 in the Hulun Buir meadow steppe of Inner Mongolia,China.We separated the litter mixture into its individual component litters(i.e.the different single-species litters)and analyzed the changes in litter mass remaining and litter nitrogen(N)remaining during single-and mixed-species litter decomposition.Important Findings(i)Litter mixing had significant positive effects on litter decomposition.The litter-mixing effect was strongest for the mixture of S.baicalensis and L.chinensis litters,followed by the mixture of S.baicalensis and M.ruthenica litters.(ii)Single-species component litters decomposed faster in the mixtures than separately(positive effect),but these effects were not significant for legume species M.ruthenica litter.Relative to single-species litter decomposition,the decomposition rates of the two grass(S.baicalensis and L.chinensis)litters significantly increased when they were mixed with each other or with M.ruthenica litter.(iii)For each species litter type,the percentage of litter N remaining during decomposition(NR)differed between the single-species litter and mixed litter treatments.The NR of S.baicalensis litter was higher when it was decomposed in the mixture than in isolation.However,the NR of L.chinensis litter was lowest in its mixture with M.ruthenica among the treatments.Regardless of its decomposition in the mixture or in isolation,the NR of M.ruthenica litter varied little among treatments.There was a significant positive relationship between the NR and percentage of initial litter mass remaining in both the single litter and mixed litter treatments.These results suggest that N transfer may happen among component litters in mixture and further affect the decomposition.

Understanding livestock production and sustainability of grassland ecosystems in the Asian Dryland Belt

Background:Companioned by economic development,a dietary shift toward higher meat consumption is seen in developing countries and transitional economies,where the demand for livestock production has been increasing in response to such a dietary shift.In the Asian Dryland Belt,approaches to meet this demand have focused on grazing intensification,cropland conversion for animal feed,and supplemental feeding.With the scarcity of water,energy,and food in the region,a key question is whether or not the current approaches are sustainable.If not,what are the pathways to increase livestock production while protecting the region’s environment for a sustainable future?We provide our reviews and discuss current approaches in response to these dietary shifts and assess their environmental resilience with a focus on the grassland ecosystems in the Asian Dryland Belt.Results:While current approaches alleviate the urgent need for short-term livestock production,they lead to longterm vulnerability in food security.Trade-offs between short gains and long-term losses,between food for humans and for animals,and between agricultural intensification and environmental degradation need to be holistically examined for the sustainable development of the region.A grassland water,energy,and food nexus framework is proposed with specific recommendations to increase livestock production while considering other ecosystem services of the dryland grassland ecosystems in the Asian Dryland Belt.Conclusions:Current practices to increase livestock production are likely to lead to long-term,large-scale ecological degradation of the grassland ecosystems in the Asian Dryland Belt and are thus unsustainable.By considering the trade-offs in the nexus of water,land,food,and livelihoods,sustainable pathways were articulated and recommended.Future pilot studies are needed for validation and adoption.

Managed grassland alters soil N dynamics and N2O emissions in temperate steppe

Reclamation of degraded grasslands as managed grasslands has been increasingly accelerated in recent years in China. Land use change affects soil nitrogen（N） dynamics and nitrous oxide（N2O） emissions. However, it remains unclear how large-scale grassland reclamation will impact the grassland ecosystem as a whole. Here, we investigated the effects of the conversion from native to managed grasslands on soil N dynamics and N2O emissions by field experiments in Hulunber in northern China. Soil（0-10 cm）, nitrate（NO3-）,ammonium（NH4＋）, and microbial N were measured in plots in a temperate steppe（Leymus chinensis grassland） and two managed grasslands（Medicago sativa and Bromus inermis grasslands） in 2011 and 2012. The results showed conversion of L. chinensis grassland to M.sativa or B. inermis grasslands decreased concentrations of NO3--N, but did not change NH4-N . Soil microbial N was slightly decreased by the conversion of L. chinensis grassland to M.sativa, but increased by the conversion to B. inermis. The conversion of L. chinensis grassland to M. sativa（i.e., a legume grass） increased N2O emissions by 26.2%, while the conversion to the B. inermis（i.e., a non-legume grass） reduced N2O emissions by 33.1%. The conversion from native to managed grasslands caused large created variations in soil NO3-＋-N and NH4-N concentrations. Net N mineralization rates did not change significantly in growing season or vegetation type, but to net nitrification rate. These results provide evidence on how reclamation may impact the grassland ecosystem in terms of N dynamics and N2O emissions.