نتایج جستجو برای: seed density
تعداد نتایج: 483256 فیلتر نتایج به سال:
روانگرایی در ماسه های ریزدانه اشباع در هنگام زلزله، موجب خرابی سازه های زیادی در نقاط مختلف دنیا بوده است. از عوامل موثر در این پدیده می توان به تراکم خاک، دانه بندی خاک، عمق لایه مورد نظر و تنش های موثر همه جانبه، شدت و مدت زمان زمین لرزه و درصد عبوری از الک شماره 200 (مقدار ریزدانه و جنس آن) اشاره نمود. عالباً در روشهای رایج ارزیابی وقوع روانگرایی از خصوصیات درجای خاک، همانند نتایج آزمایش های ...
In order to determine the effect of plant density on yield and qualitative traits of four genotypes of sunflower (Helianthus annuus L.) an experiment was conduct in Research Farm of Kabotar Abad, Isfahan province, Iran, in 2009. The statistical design was factorial arrangement in complete randomized blocks with four replications. Four plant density (6, 8, 10 and 12 plants/m2) and four genotypes...
The ecological literature presents considerable evidence for top-down forcing on the maintenance of species diversity. Yet, in temperate forests, bottom-up forces often exert a strong influence on ecosystem functioning. Here, we report on the indirect influence of a pulsed resource, sugar maple (Acer saccharum) seed production, on nest survival in a migratory songbird. We hypothesized that seed...
Soil seed banks can act as an important source in forest regeneration, and the information on the seed bank composition is vital for determining the resilience of plant communities under severe environments such as urban settings. In this study, we examined the seed bank density and functional composition, and their relationships with aboveground vegetation in three remnant evergreen broad-leav...
Factors affecting the density and distribution of yellow-poplar regeneration after a single growing season prescribed fire were studied in mature upland oak stands in the southern Appalachian Mountains. In burned and unburned stands, density of one and two year old yellow-poplar seedlings was inventoried within 50 m from isolated yellow-poplar canopy seed trees in response to distance from seed...
Hunting may have drastic effects on some populations of frugivores and seed dispersal agents, which in turn may affect patterns of forest regeneration and plant diversity. However, when a species disappears, it is possible that the population of other species increases due to competition release, compensating or not, their ecological roles. The main aim of this study was to measure density comp...
in order to study the intercropping of barley (hordeum vulgare l.) and faba bean (vicia faba l.) an experiment was conducted as factorial based on randomized complete block design with two factors and three replications at sari agricultural science and natural resources university during 2009. the first factor was two seed ratios include d1: 75 and 150 kg.ha-1 of faba bean and barley, respectiv...
Flax (Linum usitatissimum L.), an oilseed crop, is widely adapted and grown in many regions of the world. Oil from regular flaxseed is used as an industrial drying oil because of the high level of linolenic acid (>50 %). However, the oils from new mutant genotypes of flax with a very low linolenic acid concentration (<2 %) are edible. Yellow seed colour can be used as a visual marker to disting...
—Pinyon-juniper (Pinus monophylla–Juniperus osteosperma) woodlands are expanding into shrubsteppe ecosystems in western portions of the Great Basin. Often, highly competitive trees displace the understory, and prescribed fire is increasingly used as a restoration tool. To inform management decisions about post-fire recovery, we examined immediate and long-term (i.e., 2 growing seasons) response...
Declines in riparian willow (Salix spp.) communities in Rocky Mountain National Park, Colorado, USA , coincident with a large increase in elk (Cervus elaphus L.) populations, has raised concerns about the future of willow communities. To identify possible constraints on willow establishment in two heavily browsed riparian areas, in 2000 and 2001, we examined seed dispersal phenology, germinabil...
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