基于大食物观的草地农业发展趋势及关键科学问题

大食物观下,国家食物安全的重点是饲料粮安全。草地农业是全球最重要的食物生产系统之一,既直接生产草畜产品,又间接地为食物生产提供生态保障,满足国家对食物安全、生态安全和边疆稳定不断增长的刚性需求。目前,草地农业保障国家食物安全的水平亟待提高,支撑国家高质量发展的能力亟待加强。种子是草地农业的物质基础,天然草原和栽培草地(也称“人工草地”)是草地农业生产食物的主要基地,草地保护为草地农业开展食物生产“保驾护航”,草地农业系统耦合促进食物生产的效益放大。草地农业是基础性战略产业,保障国家食物安全的水平依靠基础研究的创新。为此,本文分析了草类种质资源挖掘利用与种子生产控制、牧草优质高产栽培与转化、草原生态生产力维持与修复、草地有害生物管理、草地农业系统耦合与管理等5个方面的研究进展,并提出对应的关键科学问题。

Effect of Feed Restriction on Broiler Chicks Prior to Slaughter

The present study was conducted to study the effect of feed restriction prior to slaughter on carcass weight of male broiler chicks from 32 to 40 days of age. A total number of 180 (Pure line) male broiler chicks were taken randomly, labeled and divided into six groups. At 32 days of age, the experimental groups were put under the experimental feeding program. Group A fed ad libitum (control) while group B and C fed 120, 60 gm/bird/day for eight days, respectively. Group D and E fed 120, 60 gm/bird/day for four days respectively, followed by zero feeding for an extra 4 days. Group F deprived of food during the whole experimental period (8 days). The experimental diet was formulated to be approximately iso caloric-iso nitrogenous containing sorghum, groundnut cake, broiler concentrate, calcium, salt, lysine, methionine, and premix. The parameters taken were live body weight, feed intake, mortality, carcass, and non-carcass values. The effect of feed restriction program on male broiler chicks was not significant during the period from 32 to 34 days of age for parameters final live body weight, carcass weight, and dressing percentage, but net weight (gain or loss) was affected by feed restriction program and showed a significant difference (P < 0.01) between experimental groups. From 32 to 36 days of age male broilers subjected to feed restriction regimes showed the lowest reading for final live body weight, net weight (gain or loss) and carcass weight and the difference were significant (P 0.05) between experimental groups for dressing percentage during period from32 to 36 days of age. At the period from 32 to 38 days and the period from 32 to 40 days of age, all parameters were significantly affected by feed restriction program. It was concluded that carcass weight of broiler chickens can be controlled using different options of feed restriction programs according to the need of the market and the producer situation with special consideration to the economic return.

Neighbour effects on plant biomass and its allocation for forbs growing in heterogeneous soils

Focal plants are considerably affected by their neighbouring plants,especially when growing in heterogeneous soils.A previous study on grasses demonstrated that soil heterogeneity and species composition affected plant biomass and above-and belowground allocation patterns.We now tested whether these findings were similar for forbs.Three forb species(i.e.Spartina anglica,Limonium bicolor and Suaeda glauca)were grown in pots with three levels of soil heterogeneity,created by alternatively filling resource-rich and resource-poor substrates using small,medium or large patch sizes.Species compositions were created by growing these forbs either in monocultures or in mixtures.Results showed that patch size×species composition significantly impacted shoot biomass,root biomass and total biomass of forbs at different scales.Specifically,at the pot scale,shoot biomass,root biomass and total biomass increased with increasing patch size.At the substrate scale,shoot biomass and total biomass were higher at the large patch size than at the medium patch size,both in resource-rich and resource-poor substrates.Finally,at the community scale,monocultures had more shoot biomass,root biomass and total biomass than those in the two-or three-species mixtures.These results differ from earlier findings on the responses of grasses,where shoot biomass and total biomass decreased with patch size,and more shoot biomass and total biomass were found in resource-rich than resource-poor substrates.To further elucidate the effects of soil heterogeneity on the interactions between neighbour plants,we advise to conduct longer-term experiments featuring a variety of functional groups.

祁连山绿色发展:从生态治理到生态恢复

在祁连山生态环境经重锤整治、生态恢复初显成效之际,第二次青藏高原综合科学考察之'祁连山综合考察'全面开启.优先围绕生态系统与生态安全、固体水库动态变化、人类活动变化与生态生计影响三大关键任务,开展天-空-地一体化考察,定量核算了生态环境整治后局部的生态环境收益与经济损失,并基于远程耦合方法核算了祁连山的全局生态系统服务价值.研究发现:生态环境整治提升了生态环境服务价值;暖湿化背景下生态系统整体向好,珍稀物种种群扩大,但对局部草原过牧管控不力导致退化;冰川冰储量亏损加剧,冰川融水径流贡献率将越过临界点;过去10多年冻土融化释放的水量约为1.18 km3/a,相当于祁连山出山河流年径流总量的10%;祁连山全局生态系统服务估算价值高达10676(±1601)亿元,远高于2017年区域经济损失的53.09亿元.鉴于祁连山对于全国的巨大生态价值,建议国家加大生态补偿力度,实现祁连山生态生计双赢的绿色发展.祁连山综合科学考察成果可为祁连山国家公园建设,以及'山水林田湖草'系统保护与修复提供详实数据和决策依据,为'丝绸之路经济带'沿线国家流域治理提供典型案例和科学支撑.

典型草地土壤好氧甲烷氧化的微生物生态过程

【目的】针对我国甘肃三个典型生态区草地土壤(玛曲MQ、临泽LZ和环县HX),研究其甲烷氧化潜力、甲烷氧化菌(methane-oxidizingbacteria,MOB)丰度及可能存在的群落分异规律。【方法】通过原位分析、室内高浓度甲烷模拟培养三种典型土壤及实时荧光定量、高通量测序的方法研究甲烷氧化菌标靶基因pmoA序列的组成及其丰度变化规律。【结果】三种典型草地土壤的原位甲烷氧化菌的丰度存在显著差异,表现为MQ>HX>LZ,其数量范围为为0.18–6.86×10^7g/d.w.s.;甲烷氧化潜力也表现出类似规律,其通量为109–169mg/(m^2·h);甲烷氧化潜力与原位土壤中甲烷氧化菌丰度有正相关。三种草地土壤甲烷氧化菌存在明显的空间异质性,采用高通量测序的方法,发现三种草地原位土壤中的优势类群为USCγ(Upland Soil Cluster gamma,USCγ);然而,室内高浓度甲烷氧化过程中,传统的甲烷氧化菌均发生明显增加,MQ土壤中TypeⅡ的Methylocystis为优势类群,而LZ和HX土壤的优势类群均为TypeⅠ型Methylosarcina。【结论】这些研究结果表明,我国甘肃典型草地土壤中也存在难培养的大气甲烷氧化菌和经典的可培养甲烷氧化菌,这些微生物极可能氧化极低浓度的大气甲烷,也可能利用闭蓄于土壤中的高浓度甲烷生长。未来应采用先进技术原位观测大气甲烷氧化过程并分离相应微生物类群,研究草地土壤甲烷氧化菌地理分异规律及其环境驱动机制。

Sustainable management of Chinese grasslands—issues and knowledge

China has almost 400 Mhm^2 of grasslands,90% of which is considered degraded to varying degrees,on which 16 million herders depend for their livelihoods and many more indirectly, along the value-adding chain.Since 1950, average stocking rates across China have increased 4-fold. National policies have focused over recent decades on finding ways to rehabilitate the degraded grasslands, to sustain livestock production from them, and to improve the livelihoods of herder households, who are among the poorest people in China. A large collaborative program commenced in the early 2000 s to help find solutions to the sustainable management of grasslands.This paper summarizes key findings of many research projects, identifies where knowledge is weak and argues that the successful rehabilitation of grasslands will also require policies that provide incentives and support for herders as they move from a focus on survival to a focus on production of higher quality products, for which consumers are increasingly willing to pay. A key focus is to emphasize the improvement of animal production per head. When this is done, it naturally leads to lower stocking rates, which in turn provides the opportunities for grasslands to recover. Across a range of experiments, farm demonstrations and analyses using models, in Inner Mongolia and Gansu, a consistent result has been that a 50% reduction in stocking rates, improves net household income and starts the process of grassland rehabilitation.Rather than focusing on stocking rates, better management of grasslands could be achieved by maintaining the grasslands above critical values for herbage mass, values that help optimize botanical composition, reduce soil erosion, optimize animal growth rates and aid ecosystem functions. Managing to critical values for herbage mass is likely to be more effective than efforts to calculate sustainable stocking rates. An early summer rest is valuable for aiding grassland rehabilitation and summer productivity, but a total grazing ban(typically for 5 years)may not achieve its aims as evidence shows it may take 10–15 years to achieve a better grassland state. Lessdesirable plant species often increase in degraded grasslands that are rested and grazing can help manage those species. Surveys of herders indicate they have very mixed views on the benefits of total grazing bans that are unlikely to rehabilitate grasslands to an ideal botanical composition.The current objective is to work with grasslands that herders now have and optimize the existing composition.Grazing grasslands in winter results primarily in weight loss by animals and there is now evidence of how winter grazing reduces grassland growth in the next summer. It is better to keep animals in well-built sheds and feed them better, improved feeding through the cold months is required. In addition to the application of results from national programs designed to improve grasslands, it will be important to train herders as they move from survival to production, to foster the development of better markets for their livestock products, to devise better financial support for herder businesses and to revise land tenure arrangements so that herders can expand the area of land they graze on better terms than apply at present.

GRASSLAND AGRICULTURE IN CHINA--A REVIEW

Interactions between crops and livestock have been at the core of the evolution of many agricultural systems.In this paper,we review the development and characteristics of mixed crop-livestock systems,with a focus on grassland-based systems,as these cover large areas in China,and face several challenges.Following the transition from the original hunting and foraging systems to a sedentary lifestyle with integrated crop-livestock production systems some 8000 years ago,a range of different mixed systems have developed,depending on rainfall,solar radiation and temperature,culture and markets.We describe 5 main types of integrated systems,(1)livestock and rangeland,(2)livestock and grain production,(3)livestock and crop-grassland rotations,(4)livestock,crops and forest(silvo-pasture),and(5)livestock,crops and fish ponds.Next,two of these mixed systems are described in greater detail,i.e.,the mountain-oasis-desert system and its modifications in arid and semi-arid regions,and the integrated crop-livestock production systems on the Loess Plateau.In general,crop-livestock interactions in integrated systems have significant positive effects on crop production,livestock production,energy use efficiency and economic profitability.We conclude that improved integration of crop-livestock production systems is one of the most important ways for achieving a more sustainable development of animal agriculture in China.

Effects of three-dimensional soil heterogeneity on seed germination in controlled experiments

Aims Seed germinations react to their local growing conditions,but the impacts of soil heterogeneity on seed germinations are not well known.Methods Effects of three-dimensional soil heterogeneity on seed germinations of grasses species were explored,where two levels of such soil heterogeneity were created via alternatively filling nutrient-poor and nutrientrich substrate in pot in all directions.Patch sizes of the two heterogeneity levels are around 7.5 and 15 cm,respectively.Fifty seeds of each of the grasses species(Lolium perenne and Elymus nutans)were set either in these heterogeneous soils or in petri dishes with distilled water.Seed germinations of these species were daily recorded.Important Findings We found that pots with smaller patches had relatively lower germination rate,which is con sistent with our expectati on that shorter distance between nutrient-rich and nu trient-poor patches in pots with smaller patches allows plants to reduce their germination rates and delay their germination,in order to reduce the negative impacts of the strong variation of soil resources in these pots.Our results also revealed that pots with smaller patches yielded more heterogeneous seed germination,i.e.seed germinations highly diverged among these pots.These findings highlight that the realistic three-dimensional design can improve our understanding of seed germination as driven by soil spatial heterogeneity.

Elevated and atmospheric-level methane consumption by soil methanotrophs of three grasslands in China

Background:Methane(CH4)oxidation driven by soil aerobic methanotrophs demonstrates the capacity of grassland as a CH4 sink.Methods:In this study,we compared the oxidation characteristics of atmospheric-level and elevated concentration(10%)CH4 in a typical grassland(steppe)on the Loess Plateau,an alpine meadow(meadow)on the Qinghai-Tibet Plateau,and an inland arid-area artificial grassland(pasture)in northwest China and investigated the communities of active methanotrophs and their contribution to CH4 oxidation using DNA-based stable-isotope probing and Illumina Miseq sequencing.Results:The results showed that the oxidation of atmospheric CH4 only occurred in steppe and meadow soils where the USCγgroup of methanotrophs was numerically dominant in the methanotroph community.Pasture soils,with their very low relative abundance of USCγ,did not show atmospheric CH4 oxidation.However,a DNA-stable isotope probing experiment with 10%CH4 indicated that conventional CH4 oxidizers(Methylocaldum and Methylocystis)rather than USCγcommunities assimilated significant amounts of 13CH4 for growth.Conclusions:The CH4 oxidation mechanisms in the three experimental grassland soils varied significantly.The USCγgroup may be obligate oligotrophic microorganisms or their growth requires specific unknown conditions.