排序方式: 共有102条查询结果,搜索用时 15 毫秒
61.
Biomechanical characteristics of the root system of hornbeam (Carpinus betulus) were assessed by measuring Root Area Ratio (RAR) values and tensile strength of root specimens of eight hornbeam trees growing
on hilly terrain of Northern Iran. RAR values of the roots were obtained using profile trenching method at soil depth of the
top 0.1 m. In total 123 root specimens were analyzed for tensile strength. Results indicate that in general, RAR decreases
with depth, following a power function. The RAR values in up and down slopes have no significant statistical differences.
In most cases, the maximum RAR values were located in soil depth of the top 0.1 m, with maximum rooting depth at about 0.75
m. The minimum and maximum RAR values along the profiles were 0.004% and 6.431% for down slope and 0.004% and 3.995% for up
slope, respectively. The number of roots in the up and down slope trenches was not significantly different. In the same manner
as for RAR, number of roots distributing with depth was satisfactorily approximated a power function. The penetration depths
of above 90 percent of the roots were at soil depths of 50 cm and 60 cm for up and down slopes, respectively. Results of Spearman’s
bivariate correlation showed no significant correlation between the RAR value with tree diameter and gradient of slope and
number of roots. The mean value of root tensile strength was 31.51 ± 1.05 MPa and root tensile strength decreased with the
increase in root diameter, following a power law equation. Using ANCOVA, we found intraspecies variation of tensile strength.
Biography: Ehsan Abdi (1978– ), Male, Ph.D candidate, in the Department of Forestry, University of Tehran, Karaj 31585-3314,
Iran. 相似文献
62.
63.
通过不同林分黑翅土白蚁采食工蚁的饵料筛选结果,分析白蚁取食经历对食物选择的影响。结果表明:来自不同林分的黑翅土白蚁喜食树种最佳为鹅掌楸树皮粉,其工蚁数量、泥被覆盖率和饵料被食率均较高,泥被出现时间在所有饵料中也相对较早。筛选出的辅食饵料最佳比例为15%小米粉和5%蔗糖,高糖分对黑翅土白蚁仅有短暂的诱食作用,一段时间后,高糖分诱食作用减退。白蚁采食工蚁存在取食记忆现象,取食记忆的持续时间与原取食材料在食物资源中的嗜食序列有关。若原取食材料属于食物选择试验中最嗜食物质,取食记忆可持续存在;否则,一定时间后发生食物选择的改变。试验筛选出最佳饵料配方为80%鹅掌楸树皮粉+15%小米粉+5%蔗糖,采食工蚁对不同树种树皮粉的取食选择可能与化学成分有关。 相似文献
64.
65.
A two-year field experiment was conducted in 2011 and 2012 at the College of Agriculture and Natural Resources, Shiraz University, Iran to determine the effect of the herbicide trifluralin, mechanical and integrated weed control under different application methods of P fertilizer (midrow banded and surface broadcast) on weed biomass and yield of rapeseed, cultivar Talayeh. Plants grown in unweeded plots at midrow banded and surface broadcast P fertilization methods produced the greatest rapeseed yield (3217 and 1034 kg ha?1, respectively). The increasing effect of P fertilizer on rapeseed yield was less consistent when rapeseed was competing with weeds. It showed that weeds were able to prevent rapeseed from capturing the full benefit of P fertilizer. Trifluralin at 1400 g ha?1 + rotary cultivator + sweep cultivator consistently provided the highest rapeseed grain (2953.5 and 2912 kg ha?1, respectively) and oil yield (1363 and 1320 kg ha?1, respectively). Additionally, trifluralin alone did not provide acceptable full season weed control in rapeseed. Since mechanical weed control implements such as rotary and sweep cultivators are available and inexpensive to Iranian farmers, trifluralin at 1400 g ha?1 + rotary cultivator + sweep cultivator is recommended to improve weed control in rapeseed. 相似文献
66.
Margarita Haruntyunyan Mohammad Ehsan Dulloo Naire Yeritsyan Armen Danielyan 《Genetic Resources and Crop Evolution》2010,57(8):1177-1189
The aims of this study are to determine the geographical and ecological distribution of nine Aegilops species in Republic of Armenia and to make an assessment of their IUCN Red List status, using the IUCN Red list categories
and criteria, in order to develop an in situ conservation strategy for wild relatives of wheat in Armenia. Ecogeographic surveys of nine Aegilops species were undertaken over 2 years in Armenia. They included a herbarium survey followed by extensive ground-truthing field
surveys where targeted Aegilops species occur. The study showed that of the nine Aegilops species studied, four are threatened and of these, Ae. mutica and Ae. crassa are critically endangered. The latter species may even be extinct in Armenia. Ae. neglecta and A. biuncialis are endangered. Additional studies are required to assess the threat status of Ae. umbellulata. Ae. columnaris was assessed as near threatened, while the remaining species (Ae. triuncialis, Ae. cylindrica and Ae. tauschii) are of least concern. There has been a dramatic decline in the genetic resources of Aegilops species during recent years in Armenia as a result of adverse human impacts such as expansion of agriculture, urbanization
and uncontrolled grazing. Several species, especially Ae. mutica and Ae. crassa, should be prioritized in conservation activities in Armenia. Efforts should be made to conserve genetic diversity of crop
wild relative species both in situ and ex situ, bearing in mind that their germplasm carries potentially valuable information (traits) that can improve adaptability and
productivity of cultivated wheat varieties. 相似文献
67.
Saeid Reza Nourollahi Fard Reza Kheirandish Ehsan Norouzi Asl Saeid Fathi 《Tropical animal health and production》2011,43(1):1-3
This research was carried out in order to detect the prevalence of nymphal stages of Linguatula serrata in mediastinal and mesenteric lymph nodes of sheep slaughtered in Kerman slaughterhouse, southeast of Iran. For this purpose,
mesenteric and mediastinal lymph nodes of 806 sheep of different sex and age were examined. One hundred and thirty out of
806 (16.1%) of the sheep were found positive for L. serrata infection. The infection rate increased with age (P < 0.001). Prevalence of L. serrata nymphs in males and females and different seasons was not significantly different (P > 0.05). Considering the results, it could be concluded that the prevalence of L. serrata in sheep of Kerman is high and plays an important role in epidemiology of linguatulosis. The zoonotic potential of this parasite
to human health is discussed. 相似文献
68.
Biodiversity and prevalence of parasites of domestic pigeons (Columba livia domestica) in a selected semiarid zone of South Khorasan, Iran 总被引:1,自引:0,他引:1
Radfar MH Asl EN Seghinsara HR Dehaghi MM Fathi S 《Tropical animal health and production》2012,44(2):225-229
Five species of nematodes and cestodes were collected from alimentary canals of pigeons: the nematodes were two species: Ascaridia colombae (16.66%) and Hadjelia truncata (1.96%), while the cestodes were Cotugnia digonopora (13.79%), Raillietina magninumida (18.62%) and Raillietina achinobothridia (32.35%); fecal examination revealed: Eimeria spp. (40.19%) and Cryptosporidium oocysts (2.94%); and blood smears showed: Haemoproteus cloumbae (47/05%); in mouth, throat and larynx: Trichomonans gallinae (57.84%); four species of ectoparasites were collected from feathers and subcutaneous nodules as follows: feathers: Pseudolynchia canariensis (63.72%), Columbicola columbae (79.41%), Menopen gallinea (44.11%); subcutaneous nodules: Laminosioptes cysticola (1.96%). From the parasitic fauna identified in this study, it is imperative to institute an integrated parasitic control
through constant changing of litter, regular use of antihelminthics, anticoccidials and dusting of birds with pesticides. 相似文献
69.
AbstractA two-year field experiment was conducted to investigate the impact of short crop rotation and organic amendments on rapeseed yield under weed competition conditions. The primary experimental plots consisted of either triticale or pea as a prior crop, consisting of four subplots with either 25 tons of composted cattle manure (CCM), 150?kg urea N ha?1 (N), 25 tons composted cattle manure + 75?kg urea N ha?1 (CCM?+?N), or no urea N or manure added as the control (C0). Rapeseed seed yield was not significantly affected by previous crops, except for rapeseed grown after pea which had slightly higher seed yield (2058?kg ha?1) than those grown after triticale (1942?kg ha?1). Plants that received CCM?+?N produced the highest amount of seed yield (2447?kg ha?1), but were not significantly different from plants that received just urea N (2218?kg ha?1). Weeds gained more biomass when the previous crop was pea compared to those whose previous crop was triticale. Weeds in plots that received CCM?+?N produced the greatest biomass, followed by N, and CCM plots, respectively. 相似文献
70.
Mahmood Mahmoodi-Eshkaftaki Amin Haghighi Ehsan Houshyar 《Soil Use and Management》2020,36(3):482-493
Land evaluation is the process of land performance predictions over time based on land uses and soil features. Traditional methods in determining soil features are proved to be time-consuming and costly. Therefore, in order to overcome these limitations, a simpler automated method using the image segmentation was developed in this study. The method was designed by integrating dynamic region merging and genetic algorithm. An area index was calculated for each soil profile using the automated method. It was used to present the amount of soil coarse particles and thereupon to determine the rating value of text-structure. Using the method, the mean intersection over union of above 0.7 was obtained for detecting the coarse particles which confirms its suitability. Data analysis showed that (a) compared to the Storie-land index (R2 = 0.71), the Square root-land index was more correlated to the harvest index (R2 = 0.73), and (b) comparing to manual methods, not only the automated text-structure had a higher correlation with the harvest index (R2 = 0.64) but also it decreased the determination time (>3.75 times). Furthermore, among the models developed by response surface methodology for estimation of soil features, the developed model for estimation of soil lime showed the highest accuracy (R2 = 0.89). In conclusion, since the developed method is more accurate, more economic and faster than the usual manual methods, it can be widely used in land suitability evaluation. 相似文献