Fujiang Hou

A grassland classification system and its application in China

China possesses vast grassland resources that include alpine meadow, tundra, steppe and desert. It is, therefore, desirable to establish a grassland classification system that involves the formative factors contributing to this diversity. This paper reports a grassland classification system called the Integrated Orderly Classification System of Grassland (IOCSG), which was formulated through grouping or clustering units with similar properties. The IOCSG involves a hierarchy of three classification levels. At the first level, grasslands are grouped into classes according to an index of moisture and temperature. At the second level, grasslands are differentiated as subclasses by the edaphic conditions. At the third level, grassland types within a subclass are distinguished by vegetation types. Under the IOCSG, seven thermal zones and six humidity zones have been identified and used to differentiate grassland classes. The IOCSG recognises 42 grassland Classes, of which 41 are present in China.

Integrated crop-livestock production systems in China

The integrated crop-livestock production system provides most of the food needed by the people of China. Five types of integrated production systems are recognised; rangeland, grain crops, crop/pasture, agro-silvopastoral and ponds. Development of more sustainable and integrated crop-pasture-rangeland-livestock production systems has been recently achieved. Demonstrations of the integrated systems at household, village and regional levels are occurring for rain-fed agriculture on the Loess Plateau, the Hexi Corridor, north-western China and the Karst region of Guizhou Province, south-western China. These indicate that integration of crop, livestock and forage are effective means of improving agricultural productivity, environmental sustainability and farmers’ incomes. Widespread adoption of integrated farming systems should also reduce rangeland degradation.

Synergistic interactions of arbuscular mycorrhizal fungi and rhizobia promoted the growth of Lathyrus sativus under sulphate salt stress

In order to examine the influence of microsymbionts on plants, arbuscular mycorrhizal (AM) fungi and rhizobia were used to examine the growth of Lathyrus sativus under sulphate salt stress. Seedlings of L. sativus were inoculated with a combination of selected microsymbionts. Plants were grown under greenhouse conditions with five Na2SO4 concentrations (0, 1%, 2%, 3% and 4% (weight : weight)). The inoculations combinations used were the AM fungus, Glomus mosseae and/or the rhizobium, Mesorhizobium mediterraneum. The results showed that sulphate salinity inhibited plant growth and biomass production. However, compared with the control treatments, dual-inoculation of G. mosseae and M. mediterraneum reduced the harmful influence of sulphate salinity. Parmeters including plant height, the extent of AM colonization, total biomass, nodules biomass, P concentration, N concentration and proline concentration confirmed that dual inoculation plays a vital role in promoting the growth of L. sativus under sulphate salt stress. The results suggested that the use of this dual inoculation could be exploited in grassland plantation establishment and in pastoral ecosystem reclamation programmes in arid and semi-arid areas subject to moderate salt contamination.

Effects of grazing systems on herbage mass and liveweight gain of Tibetan sheep in Eastern Qinghai-Tibetan Plateau, China

Grazing strategies, consisting of grazing systems and stocking rate adjustments, have evolved from the need to sustain efficient use of the forage resources by livestock, increase animal performance and sustain forage production. A 3-year study was conducted with Tibetan sheep on the Eastern Qinghai-Tibetan Plateau, China to compare: (1) two grazing systems [season-long continuous (SLC; July to December) versus short duration with seasonal rotation (SDSR; July to September in growing-season pasture and October to December in cold-season pasture) with a stocking rate of 24 sheep months ha–1(SM ha–1)]; (2) SDSR system with 24, 36 and 48 SM ha–1; and (3) seasonal aspects of stocking rate under the SDSR system by comparing strategies of heavy stocking rate in the growing season and light stocking rate in the cold season (SDSR-HL) versus light stocking rate in the growing season and heavy stocking rate in the cold season (SDSR-LH). No differences were found between grazing systems in liveweight gain per head or per ha and in residual herbage mass. Liveweight gain per head for treatment SDSR24 was greater than for treatments SDSR36 and SDRS48, whereas liveweight gain per ha showed the opposite tendency. No differences were found between the SDSR-HL and SDSR-LH treatments in liveweight gain per head or per ha, whereas the ratio of residual herbage mass at the end of grazing the growing-season pasture to the cold pasture of treatment SDSR-LH was more than twice that of treatment SDSR-HL. Daily liveweight gain of Tibetan sheep decreased linearly with increasing grazing pressure in both growing and cold seasons. It was estimated that, at a grazing pressure index of 310 sheep days t–1 DM peak herbage mass, liveweight gain per head and ha appears to be optimised over the whole grazing period. Liveweight loss by Tibetan sheep during the cold season was apparent regardless of grazing pressure indicating that temperature had a stronger influence on sheep performance in the cold season than herbage availability.

The effects of different intensities of long-term grazing on the direction and strength of plant–soil feedback in a semiarid grassland of Northwest China

AimsPlant–soil feedbacks (PSFs) and grazing drive community dynamics in grasslands. We examined how the intensity of grazing and PSF interact to affect plant growth and explored what drives the observed feedback effects.MethodsThree dominant perennial plant species; Artemisia capillaris, Lespedeza davurica, and Stipa bungeana were grown in field-conditioned soil (sterilized or unsterilized) collected from four grazing intensities in a semiarid grassland of northwest China. Soil nutrient concentrations and root fungal communities were determined.ResultsPlant biomass increased with grazing intensity for the three plant species. Within each grazing intensity, plant growth in sterilized soil relative to unsterilized soil differed markedly among species. Soil inorganic nitrogen (N) concentration tended to increase with increasing grazing intensity. Arbuscular mycorrhizal fungi (AMF) colonization was high for all grazing intensities for L. davurica. Fusarium tricinctum, the most common pathogenic Fusarium species, had the highest frequency from the control for A. capillaris and tended to increase with increasing grazing intensity for S. bungeana.ConclusionsOur results suggest that in grasslands plant growth can be modified by the intensity of grazing via grazing-induced changes in soil nutrient availability and fungal communities. Additional studies are needed to determine how grazing intensity affects species co-existence through PSFs to mixed communities.

The roles of an Embellisia sp. causing yellow stunt and root rot of Astragalus adsurgens and other fungi in the decline of legume pastures in northern China

The roles of fungal diseases in the decline of standing milk-vetch pastures were investigated in field plot and glasshouse experiments in Gansu Province, China. Experimental plots within 8-, 6-, 4- and 3-year-old stands were used for measurement of plant populations and productivity, and to survey the mycobiota of root, stem and foliage tissues of healthy plants and diseased plants (showing symptoms of yellow stunt and root rot disease). Selected fungal isolates were tested for pathogenicity by inoculating 2-day-old seedlings grown in pots of sterilised soil. Plant mortality increased and plant density and productivity decreased progressively with age of stand. Of the 27 fungal species of 21 genera isolated from field-grown plants, the most frequently isolated from roots were Fusarium chlamydosporum and F. solani (other Fusarium spp. were also common), whereas Embellisia sp. and Alternaria sp. were most common from aerial tissues of diseased plants. The 11 species tested for pathogenicity could be divided into four virulent types: strongly virulent (Embellisia sp.), moderately virulent (F. oxysporum, F. chlamydosporum and F. avenaceum), weakly virulent (F. solani, F. semitectum, F. verticilloides, Conostachys rosea and Cladosporium herbarum) and non-virulent (Alternaria alternata and Alternaria sp.). Root rot caused by Embellisia sp., together with Fusarium spp. and C. rosea, appears to be the main fungal disease contributor to decline of standing milk-vetch pasture in northern China.

Soil C, N, and P Stocks Evaluation Under Major Land Uses on China's Loess Plateau☆

ABSTRACT Loess Plateau covers 640 000 km2 in the central northern China. Despite a semiarid environment, harsh winters, and hot summers, agriculture has been practiced in this region for > 5 000 yr, and the food production systems are among Chinas oldest. The environment is fragile because the loessial soils are prone to erosion. Sound scientific information is therefore required to underpin future land use planning in the region. To this end, total soil organic carbon (SOC), N, and P stocks were measured in Huanxian County of the wider Loess Plateau, representing five major land use categories. Sites were sampled three times over 3 yr. In all, almost 2 800 soil analyses were performed. A feature of these soils is low SOC content in the A horizon but comparatively small decline with soil depth. For example, SOC levels for the 0–20 cm and 70–100 cmsoil depths averaged 6.1 and 4.1Mg ha-1, respectively. Alfalfa and rangeland sites had 5.1 Mg ha-1 (10%) more total than cropland and 7.5 t ha-1 (16%) more total SOC to 100-cm soil depth than the two silvopastoral sites. For total soil N (0- to 100-cm soil depth) the averages of alfalfa and RL siteswere 20% and 28%, respectively, higher than the cropland and silvopastoral site group means, although soil C, N, and P levels are very low, relative to those of typical soils elsewhere. When these observations are scaled up to a regional level, it can be calculated that a 5% shift in land use from cropping or silvopastoral systems to alfalfa-based systems could increase soil C sequestration by as many as 20 million t CO2 per yr, although some caution is needed in making extrapolations, as the present data are from a single locality on the Loess Plateau.

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

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-1 were 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-1 dry soil with 0 sheep ha-1 to 16 218 bacteria g-1 dry 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-1 soil d-1 in ungrazed treatments to 2.86 mg NO3-N kg-1 soil d-1 at 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.

Does dormancy protect seeds against attack by the pathogenic fungus Fusarium tricinctum in a semiarid grassland of Northwest China

AimsSoil fungal pathogens can result in the failure of seedling establishment, but the effects of fungicide applications on seed/seedling survival have differed among studies. We assumed that the variation may relate to seed dormancy/germination characteristics and hypothesized that nondormant germinating seeds are more likely to be killed by fungal pathogens than dormant seeds.MethodsDormant and nondormant seeds of Stipa bungeana and Lespedeza davurica were inoculated with a pathogenic fungus Fusarium tricinctum under laboratory and field conditions. The outcomes of seed/seedling fate and other parameters were evaluated.ResultsIn the laboratory, nondormant seeds inoculated with F. tricinctum developed white tufts of mycelium on the radicles of germinating seeds causing them to quickly die, but dormant seeds remained intact. In contrast, in the field inoculation with F. tricinctum did not cause higher mortality of nondormant than dormant seeds but resulted in higher percentages of seedling death before they emerged from soil than the controls.ConclusionsOur results suggest that dormancy protects seeds from being attacked by some pathogens by preventing germination, but the protection is lost once germination has commenced. Further study involving various plant species with more seeds is needed to assess the generality of this pathogen-seed interaction hypothesis.

Seasonal hogget grazing as a potential alternative grazing system for the Qinghai-Tibetan plateau: weight gain and animal behaviour under continuous or rotational grazing at high or low stocking rates

The traditional transhumance grazing system on the Qinghai-Tibetan Plateau (QTP) is being replaced by a system in which pastoralists are allocated fixed areas for grazing. In this context, we conducted experiments to evaluate a possible change to seasonal grazing of young animals for weight gain, and the effects of grazing management (continuous grazing (CG) vs rotational grazing (RG)) and stocking rate (SR) on the performance and behaviour of Oura-type Tibetan sheep. In Experiment 1 (June–December 2014), 72 Tibetan sheep (initial bodyweight (BW) 32.2 ± 3.37 kg) were allocated to one of three treatments: (1) CG24 – eight sheep grazed continuously in a single 2-ha plot for the entire duration of the experiment; (2) RG24 – eight sheep grazed in a 1-ha plot from June to September (growing season), and then moved to a new plot for September–December grazing (early cold season); (3) RG48 – eight sheep grazed in a 0.5-ha plot, but otherwise as for RG24. All treatments had three replicates. In Experiment 2 (September–December 2014), 48 Tibetan sheep (initial BW 46.3 ± 1.62 kg) were used to repeat the RG24 and RG48 treatments imposed in the early cold season of the Experiment 1. In both experiments, increasing SR significantly reduced bodyweight gain (BWG) per head and increased BWG per ha in the RG treatments. In Experiment 1, RG, compared with CG, did not significantly affect BWG per head, BWG per ha, or feed utilisation efficiency. In both experiments weight gain was small or negative in the early cold season. These results indicate that removal of sheep at the onset of the cold season will be important for retention of the weight gain achieved in the growing season but choice between a CG and RG grazing system is unimportant for the production efficiency in the proposed grazing system of Tibetan sheep.