Partial cutting does not maintain spider assemblages within the observed range of natural variability in Eastern Canadian black spruce forests

In boreal black-spruce forests of Eastern Canada, a cohort model of ecosystem management has been proposed whereby a combination of both partial and more intensive cutting are used to emulate old-growth stands and the re-establishment of stands following severe wildfire. As with other approaches to coarse filter conservation, partial cutting is hypothesized to maintain and potentially recreate plant and animal assemblages consistent with a range of natural variability. In this study, we used ground-dwelling spiders (Araneae) to evaluate whether partial cutting and a cohort model of ecosystem management are sufficient to preserve biodiversity found in mature and over-mature boreal black spruce stands prone to paludification. We compared the spider fauna (11,628 individuals representing 136 species) in replicated partial cuts, clear cuts and uncut control stands with a chronosequence of mature and over-mature naturally regenerated stands (94-288 years since the last fire) [25 stands in total] in the same region of the northern Clay belt in Québec (Canada). In stands that were old-growth prior to cutting, harvesting had strong repercussions on spider assemblages that were not attenuated by less intensive, partial cutting. The most obvious changes in spider assemblages were related to increased recruitment of species that were nearly absent in uncut stands. Several cosmopolitan species that were widely distributed among stands prior to harvest increased in cut stands. Spider assemblages collected following either cutting methods were not consistent with assemblages found within the chronosequence and thus fell outside the observed range of natural variability. However we did not observe a similar recruitment effect for spider species in younger stands with relatively higher levels of retention. We demonstrate that the interaction between stand age prior to cutting, the degree of paludification as well as remnant basal area are important considerations when evaluating the efficacy of partial cutting to maintain forest spider assemblages and biodiversity at large in black-spruce stands. “We also suggest that retention levels in partial cuts will have to be substantially increased to maintain spider communities within their range of natural variation in managed forested landscapes.” However partial cutting with higher levels of retention, particularly in younger stands, may be useful in coarse filter management particularly for establishing or accelerating spider assemblages towards those found in old-growth stands.     

Growth and yield of two grain crops on sites former covered with eucalypt plantations in Koga Watershed,northwestern Ethiopia

Farmers in the highlands of Ethiopia often plant Eucalyptus on their farmlands. However, growing Eucalyptus, especially on farm- lands suitable for crop production has become a great concern due to its alleged long-term site effects. Our study was conducted at Koga water- shed, Mecha District, northwestern Ethiopia to investigate whether crop- lands afforested with Eucalyptus camaldulensis Dehnh. can be restored for annual crop production after tree harvest. We compared growth and yield of two agricultural crops, barley （Hordeum vulgate L.） and finger millet （Eleusine coracana （L.） Gaertn.）, grown in clear-felled stands of E. camaldulensis and continuously cultivated croplands at twelve paired farmlands under a conventional farming system. Plant height and dry matter production were evaluated as indices of crop growth, while grain weight was evaluated as an index of crop yield. Crop growth and yield measurements averaged over all farmlands differed between land-use types. For both crops, plants grown on clear-felled stands were taller than on croplands. Dry matter production and yield were also significantly greater in crops cultivated on clear-felled stands. Cropland aboveground and belowground dry matter productions were lower by 31.8 and 25.4% for barley and 32.8% and 37% for finger millet, respectively. Clear-felled stands gave an average yield of 2.91 t.ha-1 for barley and 3.27 t.ha-1 for finger millet while cropland gave a yield of 1.97 and 2.31 t.ha-1 for barley and finger millet, respectively. Farmers also responded that farm plots on former eucalypt plantations showed greater crop growth and yield thandid continuously cultivated croplands. Farmers perceived that Eucalyptus plantations improved soil fertility and they preferred clear-felled stands for crop production and wished to plant Eucalyptus on their farmlands. Our results suggest that conversion of agricultural lands to Eucalyptus plantations can increase post-felling yields of cereal crops.     

Genetic characterization of the orphan crop tef [Eragrostis tef (Zucc.) Trotter] accessions using simple sequence repeat markers

Tef is the most important and well adapted cereal crop in Ethiopia and grows better than other cereals both in biotic and abiotic stress conditions. In this study 93 tef accessions representative of various agro-ecologies of Ethiopia along with four improved varieties, one local check and six wild relatives were studied. The materials were genotyped with 12 simple sequence repeat markers (SSRs) to investigate the extent and structure of the genetic diversity of tef. A total of 152 alleles were detected indicating high polymorphism in the studied accessions. The number of alleles per polymorphic loci ranged from seven for CNLT 538 to 29 for CNLT150 with an average of 12.67. High average polymorphic information content (0.82) and average expected heterozygosity (0.86) also signifies the suitability and efficiency of SSR markers to discriminate among tef genotypes. Cluster, principal coordinate and structure analyses grouped the 98 tef genotypes and six wild relatives into four distinct classes. The groupings showed no special pattern despite the different regions of origins for the accessions; however, the five wild relatives were grouped together. The analysis of molecular variance and fixation index showed low genetic differentiation and high gene flow between regions revealing that much of the variability was attributed to within populations variation. Generally, the present study showed that there is high genetic variability with unstructured genetic pattern among the studied tef genotypes which implies the vitality of conserved tef germplasms at Ethiopian Biodiversity Institute and the impact of the seed exchange system on tef breeding activities in Ethiopia.

     

Prevalence study on bovine tuberculosis and molecular characterization of its causative agents in cattle slaughtered at Addis Ababa municipal abattoir, Central Ethiopia

A cross-sectional study was conducted on 500 cattle slaughtered at Addis Ababa abattoir to determine the prevalence of bovine tuberculosis (BTB) and characterize its causative agents. Postmortem examination, mycobacteriological culturing, region of difference-4 (RD4)-based PCR and spoligotyping were applied. The prevalence of BTB was 5 % on the basis of postmortem inspection alone but 1.2 % based on molecular confirmation. Factors including age, sex, and breed showed statistically significant association with BTB (p?<?0.05). Gross lesions were observed most frequently (68 %) in the lungs and lung-associated lymph nodes compared to other organs and lymph nodes. Of the 25 grossly suspicious TB lesions processed and cultured, only six (24 %) were culture-positive, yielding Mycobacterium bovis confirmed by RD4 deletion typing. Further characterization of the six M. bovis isolates at the strain level by using spoligotyping revealed that one did not belong to any previously known type, while the others belonged to types SB1176 (two), SB1477 (two), and SB0133 (one). The new strain was submitted to the international M. Bovis.org database for international code designation. The study confirms the considerable prevalence of bovine tuberculosis in cattle slaughtered at Addis Ababa abattoir and highlights the need for control of bovine tuberculosis in the country.     

Farmers' perceptions of sorghum stem-borer and farm management practices in eastern Ethiopia

A survey of 90 farmers, randomly selected over six sorghum-growing districts in eastern Ethiopia was carried out during July to August, 2001 in the long rainy season. The study investigated farmers' perceptions of the importance of stem-borer and farm practices influencing the pest. Sorghum farming was characterized by smallholdings with an average land size of 4.3 ha, an average family size of 6 and an average yield of 878?kg ha^???1. Farmers cited pests, drought, and shortage of seed, land and labour as the main constraints upon sorghum production. Stem-borers were perceived to be the major pests requiring control. The majority of the farmers never applied chemical insecticides against stem-borers due to lack of capital and unavailability of insecticides. Because of restricted access to improved varieties, farmers largely used local cultivars of sorghum selected for yield potential but with little emphasis on insect resistance. Very few farmers destroyed sorghum residues after harvest. The majority of farmers grew sorghum under intercropping mainly due to the high yield expected. Crop rotation in sorghum fields was not widely practised due to land shortage.     

Skin pathology in Hawaiian goldring surgeonfish,Ctenochaetus strigosus (Bennett)

Twenty‐eight goldring surgeonfish, Ctenochaetus strigosus (Bennett), manifesting skin lesions and originating from the north‐western and main Hawaiian Islands were examined. Skin lesions were amorphous and ranged from simple dark or light discolouration to multicoloured tan to white sessile masses with an undulant surface. Skin lesions covered 2–66% of the fish surface, and there was no predilection for lesions affecting a particular part of the fish. Males appeared over‐represented. Microscopy revealed the skin lesions to be hyperplasia, melanophoromas or iridophoromas. The presence of skin tumours in a relatively unspoiled area of Hawaii is intriguing. Explaining their distribution, cause and impact on survivorship of fish all merit further study because C. strigosus is an economically important fish in the region.     

Genetic distance among doubled haploid maize lines and their testcross performance under drought stress and non-stress conditions

In contrast to conventional inbreeding that takes up to seven generations to develop inbred lines, the doubled haploid (DH) technology allows production of inbred lines in two generations. The objectives of the present study were to: (a) evaluate testcross performance of 45 doubled haploid lines under drought stress and non-stress conditions (b) estimate heritabilities for grain yield and other traits and (c) to assess the genetic distance and relationship among the DH lines using 163,080 SNPs generated using genotyping-by-sequencing (GBS). The 45 hybrid and five checks were evaluated using a 10 × 5 alpha lattice in six drought stress and nine well-watered environments in Kenya, Uganda, and Tanzania. Differences in trait means between the drought stress and well-watered conditions were significant for all measured traits except for anthesis date. Genetic variances for grain yield, grain moisture, plant height and ear height were high under well-watered environments while genetic variance for anthesis date, root lodging and stalk lodging were high under drought stress environments. Combined analyses across drought stress and well-watered environments showed that ten top hybrids produced 1.6–2.2 t/ha grain yield under well-watered condition and 1–1.4 t/ha under drought stress condition higher than the mean of the commercial checks. Genetic distance between pairwise comparisons of the 38 of the 45 DH lines ranged from 0.07 to 0.48, and the overall average distance was 0.36. Both cluster and principal coordinate analysis using the genetic distance matrix calculated from 163,080 SNPs showed two major groups and the patterns of group was in agreement with their pedigree. Thirteen (13) of the best hybrids are currently in National Performance Trials testing, an important step towards commercialization in Kenya, Tanzania and Uganda.     

The metal silo: An effective grain storage technology for reducing post-harvest insect and pathogen losses in maize while improving smallholder farmers’ food security in developing countries

Traditional storage practices in developing countries cannot guarantee protection against major storage pests of staple food crops like maize, leading to 20-30% grain losses, particularly due to post-harvest insect pests and grain pathogens. As a result, smallholder farmers end up selling their grain soon after harvest, only to buy it back at an expensive price just a few months after harvest, falling in a poverty trap. The potential impact on poverty reduction and greater livelihood security will not be realized, however, if farmers are unable to store grains and sell surplus production at attractive prices. Apart from causing quantitative losses, pests in stored grain are also linked to aflatoxin contamination and poisoning. To address this problem, a metal silo was developed as a valid option and proven effective in protecting stored grains from attack by storage insect pests. A metal silo is a cylindrical structure, constructed from a galvanized iron sheet and hermetically sealed, killing any insect pests that may be present. The impact of metal silo technology in Africa, Asia and Latin America includes, improving food security, empowering smallholder farmers, enhancing income opportunities and job creation, and safeguarding the agro-ecosystems. The metal silo can be fabricated in different sizes, 100 kg-3000 kg holding capacity by trained local artisans, with the corresponding prices of $35 to $375. The use of metal silo, therefore, should be encouraged in order to prevent storage losses and enhance food security in developing countries.     

挪威云杉无性系林业发展现状与趋势

概述了德国、瑞典、丹麦、挪威和苏兰5个国挪威云杉自由授粉种子园经营状况，育种群体规模，无性系林业的研究背景、研究方法、技术路线、生产规模、应用前景、可能障碍与发展趋势等。     

辽宁省推进农业产业化经营的战略对策

农业产业化经营在带动农民增收、加快现代农业发展步伐、促进工业化城镇化进程、推动社会主义新农村建设4个方面体现出重要作用,但仍面临龙头企业规模小、加工增值链条短,产业链条带动和承载力不强,中介服务组织不适应形势要求,农产品市场流通体系不健全,农企利益联结机制有待完善,农产品品牌建设有待加强等问题.结合辽宁实际,提出培育重点龙头企业、建设优质特色农产品生产和加工基地、发展完善农业产业链、培育中介服务组织、建设高效畅通的农产品流通市场体系、促进农企利益联结机制建设等9项具体措施,以推进全省农业产业化和农产品加工业发展.