Current status of coffee (Coffea arabica L.) genetic resources in Ethiopia: implications for conservation

The aim of this article is to provide an overview of the current situation of coffee genetic resources that are dwindling at an alarming rate in Ethiopia, the centre of diversity of Coffea arabica. Firstly, we describe the coffee growing systems (forest coffee, semi-forest coffee, garden coffee and plantation coffee) and recent research on the genetic diversity of the coffee planting material associated with those systems. Whilst the maximum genetic diversity revealed by DNA-based markers is found in the forest coffees of the south-western highlands, the natural habitat of C. arabica, the taxonomy of coffee landraces is particularly rich in garden coffee systems located in ancient growing zones such as Harerge in eastern Ethiopia. After reviewing the factors involved in the genetic erosion of the Ethiopian genepool, we give an update on the status of coffee genetic resources conserved ex situ in the field genebank of the Jimma Agricultural Research Centre, with 4,780 accessions spread over 10 research stations located in the main production areas, and in the main genebank of the Institute of Biodiversity Conservation located in Choche (Limu) with 5,196 accessions conserved. Lastly, we mention the in situ conservation operations currently being implemented in Ethiopia. Improving our knowledge of the genetic structure of Ethiopian forest and garden coffee tree populations as well as genetic resources conserved ex situ will help to plan the future conservation strategy for that country. To this end, modern tools as DNA-based markers should be used to increase our understanding of coffee genetic diversity and it is proposed, with the support of the international scientific community and donor organizations, to undertake a concerted effort to rescue highly threatened Arabica coffee genetic resources in Ethiopia.

塞罕坝机械林场樟子松人工林改建母树林的技术措施

通过对樟子松人工林采取松土、除草、割灌、施肥、修枝、疏伐、禁牧、统一采摘等技术及管理措施,达到早结实,提高种子产量和质量的目的,同时能够提高森林的健康水平,达到培育后备资源的目的。     

农场系统产地粮食处理中心选址的研究

本文在简述国营农场系统产地粮食处理中心发展情况的基础上,应用运筹学的单源连续与离散模型,研究并提出了选址的方法与步骤。以黑龙江省852农场为例,对各分场级粮食处理中心的选址进行了规划计算,提出了各分场较合适的厂址的示意图。     

Cattle Grazing Distribution in Shortgrass Steppe: Influences of Topography and Saline Soils

The distribution of livestock across heterogeneous landscapes is often uneven, which has important implications for vegetation dynamics and how rangeland managers achieve desired outcomes from these landscapes. Here, we use data from widely available digital elevation models to classify a landscape in the shortgrass steppe with subtle topographic variation using two different approaches: topographic wetness index (TWI) and topographic position classes (TPCs) derived from topographic position indices. We used global positioning system collars to track the grazing locations of cattle within replicate pastures and fit generalized linear mixed models to their locations to quantify the influence of topography on grazing distribution. In addition, we examine the influence of the presence of saline vegetation communities on cattle use of lowlands. The resulting models indicate that TPC more effectively predicts grazing distribution than TWI and that the patterns are strongest in the second half of the growing season (August ? October). Model performance was improved with the inclusion of saline vegetation communities, although the magnitude of cattle grazing time in these communities was not consistent across multiple pastures. These models, in combination with local knowledge, can be used by managers to predict and manage livestock distribution even in landscapes with relatively subtle topographic variability.     

北京西山林场可燃物含水率与气象要素关系

在北京西山林场建立侧柏、栓皮栎、黄栌、元宝枫和油松5种森林类型内建立观测点,从2008年12月至2009年9月,在各个类型内测定活可燃物和死可燃物含水率,并且建立可燃物含水率预测模型预测可燃物含水率。结果表明:1)可燃物含水率与气象要素中的温度、湿度、风速、降水量和连旱天数显著相关;2)可燃物含水率在每日变化呈现谷状,13:00—14:00达到每日最小值;3)可燃物含水率在1—3月初始值较低,4—6月活可燃物含水率急速增加,7—9月可燃物含水率基本达到一年内最大值。     

Agricultural intensification and loss of matrix habitat over 23 years in the West Wimmera, south-eastern Australia

The global trend toward more intensive forms of agriculture is changing the nature of matrix habitat in agricultural areas. Removal of components of matrix habitat can affect native biota at the paddock and the landscape scale, particularly where intensification occurs over large areas. We identify the loss of paddock trees due to the proliferation of centre pivot irrigation in dryland farming areas as a potentially serious threat to the remnant biota of these areas. We used a region of south-eastern Australia as a case study to quantify land use change from grazing and dryland cropping to centre pivot irrigation over a 23-year period. We also estimated rates of paddock tree loss in 5 representative landscapes within the region over the same period. The total area affected by centre pivots increased from 0 ha in 1980 to nearly 9000 ha by 2005. Pivots were more likely to be established in areas which had originally been plains savannah and woodlands containing buloke (Allocasuarina luehmannii), a food source for an endangered bird. On average, 42% of paddock buloke trees present in 1982 were lost by 2005. In the two landscapes containing several centre pivots, the loss was 54% and 70%. This accelerated loss of important components of matrix habitat is likely to result in species declines and local extinctions. We recommend that measures to alleviate the likely negative impacts of matrix habitat loss on native biota be considered as part of regional planning strategies.     

基于 Markov 模型的长沙市中心区土地利用变化研究简

以长沙市中心区为例,采用Rs和GIS技术对1991、1998、2004年3期TM数据进行处理,得到研究区土地利用现状图;在分析土地利用现状的基础上,采用Markov模型对研究区未来一段时期内土地利用变化格局进行了预测与分析。结果表明：2004～2017年,研究区土地利用变化趋势为：建设用地增加90．00％,林地增加9．25％,水域减小19．16％,耕地减小25．89％,未利用地减小0．91％。     

The effect of defoliation on bulb production of tulip cultivar ‘Apeldoorn’

The distribution of dry matter between the different bulblets of tulip is not markedly influenced by either changes in leaf area or the position of the leaf. On the contrary, total bulb yield is strongly affected.A reduction factor, S_c, for incomplete soil coverage, when the leaf area index (LAI) is less than 4, normally used for evaluation of planting density effects, can also be used for the effects of defoliation on dry matter increase. This LAI-dependent factor shows a distinctly asymptotic pathway closely resembling

$\text{S}{}_{\mathrm{c}}\text{=}\text{P}{}_{\mathrm{act}}\text{P}{}_{\mathrm{pot}}\text{=1?e}{}^{\mathrm{?k1LAI}}$

where k ～ 0.6 and in which P_act is the actual measured dry weight increase and $\text{P}\text{?}{}_{\mathrm{<mtext>pot</mtext>}}$ the potential net dry weight increase for a closed canopy.     

伴生有金雀花、黑麦草的辐射松幼苗Allophanic土壤磷肥驱动的各磷形态变化

对盆栽的伴生有金雀花(Cytisus scoparius)、黑麦草(Lolium multiflorum)的辐射松(Pinus radiata)幼苗施用3种浓度(O,50,100 μg·g-1)的三过磷酸钙,14个月后测定缺磷Allophanic土壤中各磷形态变化,确定根际土壤中施加的磷肥的去向.结果表明,施加磷肥增加了根际土壤中NaOH-Pi、NaOH-P0和H2SO4-Pi的浓度,但是减少了土壤残留磷的含量,而树脂磷浓度维持不变,在这种土壤中树脂磷浓度仍然较低(1 to 3μg·g-1).施加到土壤里的磷肥,有机磷的回收率最高(40%-49%),这是因为这种土壤具有较高的磷固定能力(92%),其次是不稳定有机磷(7%-19%).在磷肥缺乏或不施加磷肥的情况下,辐射松根际土壤中有机磷浓度低于周边土壤以及金雀花、黑麦草根际土壤.这可能与磷肥缺乏条件下,根系和菌根产生较高的草酸盐而释放部分磷到根际土壤中有关.但此观点需要进一步的研究检验.