نتایج جستجو برای: some perennial plants may cause accumulation of seed bank under their canopy
تعداد نتایج: 21397331 فیلتر نتایج به سال:
Medicago spp. is the most important forage crop in many regions of the world.Annual medics have distinct advantages over perennial Medicago. These species have fastergrowth rate in cultivation year, higher crude protein percentage, tolerance to pests and morevigorous seedlings. Morphological and physical aspects of pod and seeds of annual medicsplay a major role in the tolerance of the plants t...
drought is a major limiting factor for agricultural production in most parts of the world and landraces areimportant genetic resources for crop improvement in dry areas. during the 2007-2008 cropping season, 23 chickpea (cicer arietinum l.) genotypes consisting of 21 kabuli chickpea landraces provided by the national plant gene bank of iran and two known commercial varieties (hashem and arman) ...
We formulate an integro-difference model to predict the growth and spatial spread of a plant population with an age-structured seed bank and juvenile cohort. We allow the seeds in the bank to be of any age, producing a system of infinitely many equations. We assume that juvenile plants mature into adults at a particular age. The production of new seeds can be densitydependent and so the functio...
During early stand development, coniferous forests of the coastal Pacific Northwest commonly pass through a period of dense shade and intense competition during which the abundance and diversity of understory plants decline dramatically. In young, managed forests, silvicultural thinning has been proposed to enhance the structural and floristic diversity of the understory. Although germination o...
abstract this study evaluated and compared medical terminology and english for the students of medicine (ii) as two representatives of the textbooks available on the iranian market for teaching english to the students of medicine. this research was performed on the basis of a teacher’s and a number of students’ attitudes and the students’ needs analysis for two reasons: first, to investigate...
wireless sensor networks (wsns) are one of the most interesting consequences of innovations in different areas of technology including wireless and mobile communications, networking, and sensor design. these networks are considered as a class of wireless networks which are constructed by a set of sensors. a large number of applications have been proposed for wsns. besides having numerous applic...
abstract. rangeland vegetation dynamics encompass all processes of changes in vegetation composition and structure over time. investigating the rangeland ecosystem dynamics makes it possible to determine the effects of climatic and management conditions on qualitative and quantitative changes of the vegetation in a specific period of time. accordingly, data collection and measurements for evalu...
turfgrasses are usually important groundcover plants in many landscapes. they occupy the lowest surface of the landscape, close to pollutant particles. so, they can be an attractive option for environmental remediation. today, high concentrations of hazardous chemicals such as lead are among the most serious environmental problems. in vitro selection of turfgrass accumulator or tolerant of toxi...
We assessed the size and composition of the seed bank in 31 plots representing a range of habitats within an old-growth, temperate deciduous forest at Mont St. Hilaire, Québec, Canada. We identified 49 taxa in the seed bank, with an average of 40 species·m–2 and a median density of 1218 seeds·m–2. The most frequent seeds were species of Carex and Rubus, Diervilla lonicera, and Eupatorium rugosu...
let h be a separable hilbert space and let b be the set of bessel sequences in h. by using several interesting results in operator theory we study some topological properties of frames and riesz bases by constructing a banach space structure on b. the convergence of a sequence of elements in b is de_ned and we determine whether important properties of the sequence is preserved under the con...
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