Constraints on farm woodland planting in England: a study of Nottinghamshire farmers

A recent change in British agricultural and forestry policyhas been the shift towards the encouragement of substantialplanting of new woodland on farmland in England. Previous studiesof farm woodland planting are reviewed. A study of the attitudesof 30 farmers on the Bunter Sandstone in western Nottinghamshireto the establishment of new farm woodland is assessed. It isconcluded that new policy instruments such as special farm woodlandplanting grants and the establishment of Community Forests andspecial regional forestry initiatives have not yet brought aboutany significant change in the general opposition of farmersto the conversion of agricultural land to woodland     

EFFECTS OF TIME OF SOWING OF SPRING WHEAT AN D DEFOLIATION OF AGROPYRON REFENS (L.) BEAUV. ON COMPETITION BETWEEN THEM

Summary. Spring wheat, sown at three different times, and Agropyron repens, defoliated at the same three times, were grown separately or together in pots kept in an open-sided cage. The pots were widely spaced and adequately watered. Early sowing of wheat gave a greater grain yield than late sowing, and lessened the loss from competition with Agropyron. Early defoliation of Agropyron slowed its subsequent early growth more than did late defoliation, and plants defoliated early suffered more from competition with wheat. Competition, probably mainly for nitrogen, decreased tillering and the number of ears produced by wheat, more when sowing was late than early, but grain dry weight per ear was decreased equally at the three times of sowing. The rate at which wheat produced leaves was affected by competition only at the last date of sowing. In competition with wheat, Agropyron produced fewer shoots and ears, had lighter shoots and rhizomes, and ear emergence was slightly delayed.     

SEED POLYMORPHISM AND GERMINATION II. THE ROLE OF HYBRIDIZATION IN THE GERMINATION POLYMORPHISM OF RUMEX CRISPUS AND R. OBTUSIFOLIUS

Summary. The morphology of Rumex crispus L., R. obtusifolius L. and putative hybrids was examined. There appeared to be evidence of introgressive hybridization, particularly with backcrossing to R. crispus. Seed germination in plants from a mixed population varied widely, but when plotted against the hybrid index for the parent plants the could be partially separated in respect of germination behaviour. Some of the polymorphism previously described may have resulted from inclusion in the tests, together with pure parental types, of plants of hybrid origin which had introgressed to such an extent that they were almost indistinguishable from the parent species. The implications of the discussed.     

新疆畜牧科技信息服务平台中会员管理体系建设

以新疆畜牧科技信息服务平台的正常运行和稳步发展为依据,提出会员管理体系建设的总体思路,并详细阐述了实施会员管理的主要措施.     

气候变化对河北低平原冬小麦需水量及水分生态适应性的影响

在气候变化和水资源短缺背景下,河北低平原地区冬小麦生产面临着巨大挑战。本研究以沧州市吴桥县为例,分析该地区1981—2015年冬小麦生育期内各项气象因素变化特征,采用SIMETAW模型模拟冬小麦各生育期需水量变化,分析冬小麦各生育阶段的水分生态适应性,提出影响冬小麦各生育阶段需水量的重要气象因素。结果表明:近35年来,气温是冬小麦生育期内变化最为显著的气象因素,其中最低气温呈极显著上升趋势,增幅为0.41℃/10a,平均气温呈显著上升趋势,增温幅度为0.27℃/10a;其次是降雨量的变化,冬小麦生育期内降雨量历年来呈增加趋势,每10年增加6.06mm;其他气象因素均呈不显著上升趋势。在上述气候变化背景下,冬小麦生育期内需水量近35年总体呈上升趋势,其中1981—1998年需水量呈下降趋势,1998—2015年呈上升趋势;冬小麦3个生长阶段(播种~越冬、返青~拔节、孕穗~成熟)的需水量均为上升趋势,其中拔节~返青阶段需水量显著高于其他2个生育阶段,且水分生态适应性最差,降水耦合度多年平均仅为17.84%。影响冬小麦各生育阶段需水量的气象因素有所不同,其中影响冬小麦返青~拔节阶段需水量的主要因素包括空气相对湿度(-)、最高气温(+)、平均风速(+)、太阳辐射(+)、最低气温(+)。根据回归方程,预测吴桥县冬小麦生育期需水量在2020和2030年分别为466.7和472.6mm。本研究结果将为河北低平原地区冬小麦节水种植制度构建提供理论依据。     

Some Effects of Afforestation with Lodgepole Pine on Rates of Nitrogen Mineralization in Peat

Rates of mineral nitrogen production and carbon dioxide evolutionin incubated samples from the upper 300mm of peat beneath lodgepolepine (Pinus contorta Dougl.) have been compared with those foradjacent unplanted areas at each of six sites in the North ofScotland. Under both aerobic (moist) and anaerobic (water logged)conditions, rates of mineral nitrogen production at 30°Care strongly influenced by peatland type, sampling depth andafforestation. During the early stages of the incubation underaerobic conditions, samples of planted peat showed a more rapidaccumulation of mineral nitrogen than did samples from unplantedareas, the amounts after 17 days being 170ppm and 46ppm mineralN, respectively; after 62 days however, the difference was nolonger significant. The mean rate of CO₂ production averaged446µg CO₂ g^–1 day^–1 in planted as against728µg in unplanted peat. Under anaerobic conditions, amountsof mineral nitrogen accumulated were similar in planted andunplanted sites but a difference in accumulation between the0–150 and 150–300mm horizons in unplanted peat wassignificantly reduced beneath the trees.