春播和秋播对南方春大豆种子活力的影响

试验采用春播（４月４日）和秋播（７月３０日）两种播期法，研究春播种子活力低，秋播种子活力高的生理生化原因，结果表明，种子发芽率，发芽指数，电导率，过氧化物酶活性和真菌侵染率，这些反映种子活力的生理指标，秋播种子均优于春播种子，此外，秋播种了表皮结构较春播种子致密，种子表面小孔数目少而小，这可能也是秋播种子活力高的原因之一。     

广西草食动物现状及发展潜力

从广西草食动物存栏量大、优良品种多、农作物秸杆和牧草资源丰富的实际出发，提出充分利用这些资源优势，加快我区草食动物发展步伐的建议和策略。     

不同载牧量对苜蓿放牧地植被的影响

研究于１９９２年在甘肃河西半荒漠地区杂花苜蓿型人工草地进行，试验采用单因子设计，衣载牧量分轻牧、中牧、重牧３个处理６个重分区轮牧。结果表明，试验当年，草地类型未发生演变，披碱草随放牧加强而衰退，无芒雀麦和红豆草在中牧下得到促进，紫羊茅在重牧下受抑。由牧草产量和质量的分析表明，在西北干旱地区，苜蓿型草地可于６月初刈草后，连续放牧３次，且载牧量以中等为宜。     

Phosphorus losses in surface run-off from grazed permanent pastures on a volcanic soil from Chile

Reactive (RP) and organic phosphorus (OP) losses from grazed paddocks were determined on a volcanic soil during 2004 and 2005. Paddocks were grazed by Holstein Friesian steers (3.5 steers ha^?1) and received N (67.5 kg ha^?1) and P fertilizer (30 kg P ha^?1). Total losses ranged between 4 and 15 g P ha^?1 year^?1 and were greatly affected by incidental P losses associated with spring P fertilizer application. Reactive P constituted 90% of the total losses on average. Due to the high water infiltration capacity of the soil, run‐off was <1% of total drainage, therefore, phosphorus losses in run‐off were small.     

Contribution of White Clover Varieties in High-Productivity Systems under Grazing and Cutting

Two medium leaf size varieties of white clover (Trifolium repens L.) were grown in mixture with a range of grass species and varieties in a field experiment conducted over 4 years. The clovers were grown singly or as a blend in swards with a tetraploid perennial ryegrass (Lolium perenne L.), a diploid Italian ryegrass (Lolium multiflorum L.) or tetraploid hybrids between these two species (Lolium x boucheanum Kunth). These grasses were also grown in monoculture. Swards were managed in a regime involving two periods of sheep grazing, two periods of cattle grazing and a silage cut in the same year for 4 years. The objectives of this experiment were 3‐fold: (1) to examine the yield and persistency of white clover in highly productive systems with modern perennial, hybrid and Italian ryegrasses; (2) to compare the performance of white clover varieties grown singly in mixture with grasses with their performance together as a blend, and (3) to examine the persistency of new Italian ryegrass varieties, exemplified by AberComo. The clover content of the sward remained high throughout the experiment, with a mean of 31 % overall. Differences in clover yield between plots were largely attributable to the effects of companion grasses. Total yields were very similar in plots containing different clover varieties and in plots where these varieties had been grown singly or as a blend. Grass yields in mixture were greater than those in monoculture but showed similar relative rankings. The diploid Italian ryegrass variety AberComo showed an unexpectedly high yield in the 4th year of the experiment. The implications of these results for strategies for productive, sustainable agriculture using modern white clover and ryegrass varieties are discussed.     

Effects of cattle grazing on ecology and habitat of Columbia Basin pygmy rabbits (Brachylagus idahoensis)

Dramatic declines in the endangered Columbia Basin pygmy rabbit, a genetically unique population of small, burrowing rabbits in Northwestern United States, are likely the combined results of habitat degradation and fragmentation, disease, and predation. A critical component of pygmy rabbit habitat includes big sagebrush (Artemisia tridentata), which constitutes 82-99% of their winter diet and 10-50% of their summer diet. Sagebrush also forms the bulk of hiding cover around burrow sites. Across the range of pygmy rabbits, sagebrush habitat is grazed extensively by cattle. However, grazing has unknown effects on pygmy rabbits inhabiting the remaining, fragmented shrub-steppe habitat. We evaluated the effects of four grazing treatments on the distribution of pygmy rabbit burrows, diets of pygmy rabbits, and quality and quantity of vegetation at Sagebrush Flat in central Washington. Ungrazed areas contained significantly more burrows per unit area than did grazed areas. Vegetation composition and structure differed little among treatments in early summer before annual grazing by cattle. However, cattle grazing in late summer through winter removed about 50% of the grass cover, and reduced the nutritional quality (e.g., increased fiber and decreased protein) of the remaining grass. Although pygmy rabbits ate <2% grasses in winter, grasses and forbs comprised 53% of late summer diets. Because these endangered rabbits avoided grazed areas, removing cattle grazing from key habitat locations may benefit efforts to restore this rabbit in Washington.     

Management of Grazing Intensity in the Semi‐Arid Rangelands of Southern Australia: Effects on Soil and Biodiversity

Overgrazing contributes to rangeland degradation altering plant community composition, erosion and biodiversity. Little unanimity in the literature exists on the effects of livestock grazing on soil carbon and biodiversity, in part, due to uncontrolled grazing pressure from native and feral animals. Paired paddock contrasts at three, long‐term (>8 years) study locations in the southern Australian rangelands were used to examine the effects of managing grazing intensity through the use of exclusion fencing and rotational grazing on soil organic carbon (SOC), soil nitrogen (TN), ground cover and biodiversity (flora and invertebrates). Grazing management had no effect on SOC or TN on grey soils (Vertisols), but for red soils (Lixisols), significantly higher levels of SOC were found for both the 0 to 5 and 5 to 10‐cm soil depths (0·3% and 0·27% respectively) and associated with increased TN. We found strong and consistent relationships among SOC and higher perennial (p < 0·001), higher litter (p < 0·05) cover and close proximity to trees (p < 0·05). Managing grazing intensity resulted in significantly higher perennial ground cover (p < 0·001) on Vertisols (8·9 to 11%) and Lixisols (12·5 to 15%) and higher plant diversity (both native and exotic) but negatively impacted invertebrate diversity, indicating trade‐offs between production and resources. We provide evidence that the effects of grazing management on SOC are mediated by ground cover and increased organic matter supply and/or reduced soil carbon redistribution (erosion), which indicates that the management of grazing intensity may provide a tool to avoid soil carbon loss in rangelands. Copyright © 2016 John Wiley & Sons, Ltd.     

不同利用方式对贝加尔针茅草原土壤活性有机碳的影响

土壤活性有机碳能够准确反映土壤有效性,表征土壤质量变化,是探索可持续草地管理措施的关键指标之一。以内蒙古贝加尔针茅草原为研究对象,采用围封、放牧和刈割野外控制试验,探讨不同利用方式对土壤有机碳（SOC）和活性有机碳的影响,发现不同利用方式下土壤SOC含量表现为围封>刈割>放牧,其中围封区和刈割区土壤SOC含量显著大于放牧区,围封区与刈割区土壤SOC含量差异不显著,在土壤活性有机碳中土壤可溶性有机碳（DOC）含量表现为放牧>围封>刈割。土壤微生物量碳（MBC）和土壤易氧化有机碳（ROC）含量均表现为围封>刈割>放牧,围封区与刈割区土壤MBC和土壤ROC平均含量差异不显著,且均显著大于放牧区。土壤MBC、ROC和SOC之间呈极显著相关性（P<0.01）。土壤ROC和土壤MBC与土壤全氮和土壤全磷呈极显著相关性（P<0.01）。围封与刈割有利于土壤SOC、MBC、ROC的提升,放牧对土壤DOC有一定累积作用。围封和刈割增强了土壤SOC的稳定性,活性有机碳与土壤有机碳和土壤理化性质密切相关,能够敏感地反映土壤有机碳的变化。