关于中国草原资源可持续利用的几点战略探讨

从草业的含义论述了草原资源可持续利用的意义,简述了我国草原资源开发利用中存在的主要问题,提出了草原资源可持续利用的几点战略把加强草原生态建设和环境保护作为草原资源开发利用的根本;合理利用牧草资源和提高畜牧业生产效率;草原资源综合开发和推进产业化.     

蝗虫微孢子虫病在蝗虫和群间的流行规律研究

在同德县北巴滩进行了不同浓度蝗虫微孢子虫（N.L)小区试验和大面积推广试验，并在1997和1999年对防治效果作了调查，结果表明N.L不仅当年虫口减退率和感病率可达60％和50％以上（30天），而且在1997年、1999年防区内平均感病率仍保持在30％和40％。说明N.L具有较强的水平扩散能力和垂直感染能力，可持续、有效地控制蝗灾的发生。     

阿拉善左旗土地合理利用的途径

本文分析了阿拉善左旗资源与环境,论述了土地利用现状及存在的问题,并提出在荒漠区如何合理经营畜牧业,防止草场退化,建立饲草料基地及扩大林地面积等措施。     

海北州草地保护建设现状与建议

草地保护和建设必须以科学发展观为指导，在总结经验和分析问题的基础上，明确发展思路，确保草地保护和建设工作全面长期有效的开展，实现人与自然和谐和经济社会的全面协调可持续发展。     

Nitrous oxide emissions from fertilised grassland: A 2-year study of the effects of N fertiliser form and environmental conditions

The aim was to investigate the effects of different N fertilisers on nitrous oxide (N₂O) flux from agricultural grassland, with a view to suggesting fertiliser practices least likely to cause substantial N₂O emissions, and to assess the influence of soil and environmental factors on the emissions. Replicate plots on a clay loam grassland were fertilised with ammonium sulphate (AS), urea (U), calcium nitrate (CN), ammonium nitrate (AN), or cattle slurry supplemented with AN on three occasions in each of 2 years. Frequent measurements were made of N₂O flux and soil and environmental variables. The loss of N₂O-N as a percentage of N fertiliser applied was highest from the supplemented slurry (SS) treatment and U, and lowest from AS. The temporal pattern of losses was different for the different fertilisers and between years. Losses from U were lower than those from AN and CN in the spring, but higher in the summer. The high summer fluxes were associated with high water-filled pore space (WFPS) values. Fluxes also rose steeply with temperature where WFPS or mineral N values were not limiting. Total annual loss was higher in the 2nd year, probably because of the rainfall pattern: the percentage losses were 2.2, 1.4, 1.2, 1.1 and 0.4 from SS, U, AN, CN and AS, respectively. Application of U in the spring and AN twice in the summer in the 2nd year gave an average emission factor of 0.8% – lower than from application of either individual fertiliser. We suggest that similar varied fertilisation practices, modified according to soil and crop type and climatic conditions, might be employed to minimise N₂O emissions from agricultural land. Received: 30 August 1996     

The impacts of individual plant species on rhizosphere microbial communities in soils of different fertility

To investigate the effects of individual plant species on microbial community properties in soils of differing fertility, a microcosm experiment was carried out using plant species representative of the dominant flora in semi-fertile temperate grasslands of northern England. Soil microbial biomass and activity were found to be significantly greater in the more fertile, agriculturally improved soil than in the less productive unimproved meadow soil. Differences in microbial community structure were also evident between the two soils, with fungal abundance being greater in the unimproved soil type. Individual plant species effects significantly differed between the two soils. Holcus lanatus and Anthoxanthum odoratum stimulated microbial biomass in the improved soil type, but negatively affected this measure in the unimproved soil. In both soil types, herb species generally had negative effects on microbial biomass. Patterns for microbial activity were less consistent, but as with microbial biomass, A. odoratum and H. lanatus promoted respiration, whereas the herbs negatively affected this measure. All plant species grown in the improved soil increased the abundance of fatty acids synthesised by bacteria (bacterial phospholipid fatty acid analysis) relative to bare soil, but they negatively impacted on this group of fatty acids in unimproved soil. Similarly, the abundance of the fungal fatty acid 18:26 was increased by all plants in the more fertile improved soil only, albeit non-significantly. Our data indicate that effects of plant species on microbial properties differ markedly in soils of differing fertility, making general predictions about how individual plants impact on soil properties difficult to make.     

Gross fluxes of nitrogen in grassland soil exposed to elevated atmospheric pCO2 for seven years

Plant response to increasing atmospheric CO₂ partial pressure (pCO₂) depends on several factors, one of which is mineral nitrogen availability facilitated by the mineralisation of organic N. Gross rates of N mineralisation were examined in grassland soils exposed to ambient (36 Pa) and elevated (60 Pa) atmospheric pCO₂ for 7 years in the Swiss Free Air Carbon dioxide Enrichment experiment. It was hypothesized that increased below-ground translocation of photoassimilates at elevated pCO₂ would lead to an increase in immobilisation of N due to an excess supply of energy to the roots and rhizosphere. Intact soil cores were sampled from Lolium perenne and Trifolium repens swards in May and September, 2000. The rates of gross N mineralisation (m) and NH₄⁺ consumption (c) were determined using ¹⁵N isotopic dilution during a 51-h period of incubation. The rates of N immobilisation were estimated either as the difference between m and the net N mineralisation rate or as the amount of ¹⁵N released from the microbial biomass after chloroform fumigation. Soil samples from both swards showed that the rates of gross N mineralisation and NH₄⁺ consumption did not change significantly under elevated pCO₂. The lack of a significant effect of elevated pCO₂ on organic N turnover was consistent with the similar size of the microbial biomass and similar immobilisation of applied ¹⁵N in the microbial N pool under ambient and elevated pCO₂. Rates of m and c, and microbial ¹⁵N did not differ significantly between the two sward types although a weak (p<0.1) pCO₂ by sward interaction occurred. A significantly larger amount of NO₃⁻ was recovered at the end of the incubation in soil taken from T. repens swards compared to that from L. perenne swards. Eleven percent of the added ¹⁵N were recovered in the roots in the cores sampled under L. perenne, while only 5% were recovered in roots of T. repens. These results demonstrate that roots remained a considerable sink despite the shoots being cut at ground level prior to incubation and suggest that the calculation of N immobilisation from gross and net rates of mineralisation in soils with a high root biomass does not reflect the actual immobilisation of N in the microbial biomass. The results of this study did not support the initial hypothesis and indicate that below-ground turnover of N, as well as N availability, measured in short-term experiments are not strongly affected by long-term exposure to elevated pCO₂. It is suggested that differences in plant N demand, rather than major changes in soil N mineralisation/immobilisation, are the long-term driving factors for N dynamics in these grassland systems.     

青海草地毒草狼毒的发生及防治对策

本文就草地狼毒的发生、危害情况,结合当前青海草地草畜矛盾、地劳矛盾突出的问题,提出了在狼毒返青期,采用螺丝钻破坏狼毒根系的生长点,进行人工防治而不破坏草场植被;狼毒初花期使用48%盖灌能乳油3000ml.hm-2进行化学防治,对植被牧草安全,防除狼毒效果达90%以上,翌年灭除狼毒返青率为零。     

Management effects on the vegetation and soil seed bank of calcareous grasslands: An 11-year experiment

Calcareous grasslands, most of which are man made and therefore depend on some kind of human interference for their maintenance, are among the most species-rich communities on Earth at a small scale. For many centuries, most of these grasslands have been used as extensive pasture. However, after 1900, and particularly from 1940 onwards, livestock grazing has declined throughout Europe leading to the abandonment of low intensity grasslands over large areas. To conserve the remaining grasslands or to restore recently abandoned grasslands, better insights about the effects of grassland management on above and belowground species diversity are needed. Here, we describe the results of an 11-year experiment to investigate the role of grassland management (grazing, mowing and abandonment) in determining species composition and diversity both in the aboveground vegetation and the seed bank of a calcareous grassland in Belgium. Species diversity declined by about 60% 11 years after abandonment, from 29 species m⁻² to as few as 12 species m⁻². Plots that were grazed remained constant in species richness, whereas mown sites lost about 20% of their original species. Abandoned plots were largely dominated by a few grass species, in particular Festuca rubra. Concomitant with changes in the aboveground vegetation, both the number of species found in the seed bank and seed density (number of seeds m⁻²) had changed significantly 11 years after abandonment. Species diversity and seed density were significantly lower in abandoned plots than in grazed or mown plots. We conclude that abandonment of calcareous grasslands may lead to rapid decline of plant species diversity both in the aboveground vegetation and in the seed bank. As a result, seed banks probably have a limited role to play in the restoration of recently abandoned grasslands.