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Fritz Hervé Saïd Sonia Renaud Pierre-Cyril Mutake Snoden Coid Craig Monicat François 《Landscape Ecology》2003,18(3):293-302
After the eradication of the Tse-Tse fly in the Mid-Zambezi valley, human settlements and fields extended mainly along the main rivers. In order to investigate the consequences of this human development on wildlife diversity we monitored three rivers of the Mid-Zambezi valley in Zimbabwe: Angwa, Manyame and Kadzi. The rivers were divided in segments of 200 m which were checked for spoors in order to assess the number of species and the number of individuals that used the segments. Human settlements were also recorded. We used a GIS to define the spatial characteristics of the fields present along the rivers, and related them to the distribution and abundance of wild species spoors in the river beds and banks. Our results show that the number of species in one segment of the river decreased with the increasing size of the field area bordering the segment. For all the major ungulate species, the numbers of individuals recorded per segment decreased with increasing field area. A similar trend was observed for small and medium-sized carnivores, though they were in lower numbers when present. Our analyses thus confirm that the extension of human agriculture in wildlife areas has an impact on most wild species, but we also define some threshold value of field size above which there seem to be an acceleration of the decrease in wildlife density and diversity: 3.2 ha for medium and small herbivores and carnivores; only the elephant seem to tolerate larger field area with a threshold value of 32 ha.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
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Composition and fatty acid profile of milk from cows supplemented with pressed oilseed cake
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Ronaldo Lopes Oliveira Severino Gonzaga Neto Francisco Helton Sa de Lima Ariosvaldo Nunes de Medeiros Leilson Rocha Bezerra Elzania Sales Pereira Adriana Regina Bagaldo Caius Barcellos de Pellegrini Braulio Rocha Correia 《Animal Science Journal》2016,87(10):1225-1232
This study compared the productive and nutritional parameters of milk from crossbred lactating cows managed on Panicum maximum Jacq. cv. Tanzania and with a diet supplemented with different pressed oilseed cakes. The supplements used were as follows: peanut cake, sunflower cake and palm kernel cake for replacement of soybean meal. Sixteen cows with an average weight of 544 ± 57 kg and producing 8 ± 1.4 L of milk per day were used in this study. The animals were randomly assigned to the treatments according to a Latin square design repeated over time, with four treatments, 16 animals and four experimental periods. Supplementation of the diet with peanut cake, sunflower cake and palm kernel cake compared with soybean meal in the diet of cows did not affect the average daily production or composition of the milk. The palm kernel cake promoted an increase in lauric fatty acids (C12:0) and palmitoleic acids (C16:1) (5.02 and 1.65%, respectively) compared with peanut cake and sunflower cake (4.13 and 4.01%, respectively). The levels of oleic fatty acids (C18:1) were higher for the sunflower cake and palm kernel cake supplements (26.01 and 25.01%, respectively) compared with peanut cake (23.11%). The replacement of soybean meal with sunflower cake and palm kernel cake improved the nutritional quality of the milk, with lower concentrations of saturated fatty acids and higher concentrations of unsaturated fatty acids, without compromising the production or nutritional composition of the milk. © 2015 Japanese Society of Animal Science 相似文献
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In Tunisia both Psammomys obesus and P. vexillaris are found. These taxa have been the subject of taxonomic controversy for some time, due to variability in the classical morphological characters used for taxonomic recognition. In this study we investigated skull size and shape variation in the genus Psammomys by using geometric morphometrics to evaluate the extent of intra- and interspecific shape variation and explicitly tested for the impact of allometric shape variation on species discrimination. Eleven populations of the two species from 10 localities in Tunisia were studied. Statistical analyses of size and shape showed large size variation within P. obesus, but no shape differences were revealed among populations of this species. Interspecific analysis revealed that P. vexillaris had the smallest skull. Principal component analysis and Procrustes distances showed good discrimination between the two species after removal of the allometric component of shape variation. The results obtained show that allometric-related shape variation could mask discrimination between the two Psammomys species. This finding might explain the uncertainty in classification of these species in the past. The interspecific allometric-free phenotypic differences observed may be associated with adaptive processes linked to the different environmental and trophic preferences of the two species. 相似文献
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早籼型水稻温敏核不育系M103S的选育与光温反应特性 总被引:3,自引:2,他引:3
以温敏核不育水稻安农S—1为母本,以常规高产早籼稻品系92153为父本进行杂交,通过低温选择和人工气候箱鉴定,育成了育性转换临界温度23—24℃的早籼型温敏核不育系M103S。光周期长于12.5h,日平均温度高于24℃,可以用于制种,日平均温度低于23℃,可以用于繁殖。光周期长于13.5h,日平均温度高于23℃,可以用于制种。自然条件下不育起点温度为日均温23—24℃,耐低温期为3—4d。敏感期为抽穗前的7—14d。播始历期为53—79d,主茎叶片数10.0—12.6片。从播种到始穗的活动积温和有效积温,分别为1493.8—1766.3℃和733.4—1058.3℃。不育期的株高63.6—77.5cm,平均72.0cm,单株有效穗6.4—12.0个,平均9.3个,穗长20.9—22.7cm,平均21.2cm,每穗颖花数112.1—137.3朵,平均122.3朵。可育期株高65.7cm,单株有效穗7.2个,穗长17.2cm,每穗总粒数114.1粒,结实率47.23%,千粒重31.34g。以M103S为母本,与100多个早籼品种进行测配,杂种表现生育期早、穗大、粒多、千粒重高。 相似文献
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不同品种紫花苜蓿中总皂苷含量的比较研究 总被引:5,自引:0,他引:5
采用比色法测定了北京地区栽培不同年限的45个紫花苜蓿品种茎、叶中总皂苷的含量。结果表明,各品种苜蓿叶片中的皂苷含量均高于茎,在不同品种之间存在明显差异。4年生植株中皂苷含量最高的品种“Vernal”为1.174%,最低的品种“Empress”为0.606%;3年生植株中最高的品种“WL442”为1.141%,最低的品种“农保”为0.788%;2年生植株中最高的品种“胜利者”为1.293%,最低的品种“全能”为0.722%。综合比较,含量最低品种与最高的品种相差2.13倍。栽培年限对紫花苜蓿皂苷含量具有一定影响。 相似文献
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基于ResNet-50深度卷积网络的果树病害智能诊断模型研究 总被引:2,自引:1,他引:1
[目的/意义]果树病害危及农业生产安全,运用人工智能技术帮助果农及时准确地识别果树病害对保障农业安全生产具有重要意义.[方法/过程]采用10 000张果树叶片病斑图像数据集,通过旋转、污化、增噪、切割等图像增强手段,提高样本图像的多样性;使用ResNet-50深度卷积网络模型,进行机器学习,获得果树病害识别模型,并基于... 相似文献