نتایج جستجو برای: diversity of vegetation density

تعداد نتایج: 21214870  

Journal: :Philosophical transactions of the Royal Society of London. Series B, Biological sciences 2007
Chengyu Weng Henry Hooghiemstra Joost F Duivenvoorden

Change in diversity of fossil pollen through time is used as a surrogate for biodiversity history. However, there have been few studies to explore the sensitivity of the measured pollen diversity to vegetation changes and the relationship between pollen diversity and plant diversity. This paper presents results of a study to assess the relationship between pollen diversity and relative abundanc...

2014
ZhiQiang Fang XiaoLi Yan Xin Liu

The active effect of natural regeneration on understory vegetation and diversity on clear-cut forestlands, in contrast to conifer reforestation, is still controversial. Here we investigated differences in understory vegetation by comparing naturally regenerated deciduous forests (NR) and reforested spruce plantations (SP) aged 20–40 years on 12 similar clear-cuts of subalpine old-growth spruce-...

Journal: :محیط زیست طبیعی 0
زهره کرمانی القریشی دانش آموخته کارشناسی ارشد دانشکده منابع طبیعی، دانشگاه تربیت مدرس، ایران عباس علیمحمدی سراب عضو هیأت علمی، دانشکده مهندسی ژئودزی و ژئوماتیک، دانشگاه خواجه نصیرالدین طوسی، ایران بهرام حسن زاده کیابی عضو هیأت علمی، دانشکده علوم زیستی، دانشگاه شهید بهشتی، ایران

habitat associations of wild sheep, alborz red sheep (ovis orientalis gemelini x ovis orientalis arkali ), in khojir and sorkheh hesar national parks were studied over three seasons (spring, autumn and winter) in 2000. the position of observed maternal groups (including ewe with lamb) and male groups (including rams, barren ewes and juveniles) were determined on topographical maps during the fi...

2017
Aida Cuni Sanchez Jeremy A. Lindsell

Remnant tree presence affects forest recovery after slashand-burn agriculture. However, little is known about its effect on above-ground carbon stocks, especially in Africa. We focused our study on Sierra Leone, part of the Upper Guinean forests, an important centre of endemism threatened by encroachment and forest degradation. We studied 99 (20-m-radius) plots aged 2–10 years with and without ...

Journal: :ecopersia 2011
bakhtiar fattahi ali reza ildoromi

species diversity is an index for sustainability of rangeland ecosystems. we studied the effect of environmental factors (soil properties and aspects) on plant species diversity in zagros mountainous rangelands (vegetation type: festuca ovina-astragalus parrowianus) in the west of hamadan in march–july 2009. for this purpose, four aspects were defined in the study area. vegetation types were st...

2005
ANTHONY JOERN

Understanding determinants of local species diversity remains central to developing plans to preserve biodiversity. In the continental United States, climate, grazing by large mammals, fire, and topography are important ecosystem drivers that structure North American tallgrass prairie, with major impacts on plant community composition and vegetation structure. Frequency of fire and grazing by b...

Journal: :Ecological Informatics 2008
P. Michel J. Jenkins N. Mason K. J. M. Dickinson I. G. Jamieson

In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: In the study of habitat use by animals, it is important to sample vegetation structure or the degree of cover at different h...

        In this study we evaluate the effects of different types on soil Physical and chemical Properties and plant species biodiversity in the hyrcanian forests of Iran. For this porpuse 33 sample plots were established in 5 vegetation types consist of pure beech (Fagus orientalis), Ash plantation (fraxinus excelsior), spruce plantation (Picea abies), mixed forest and degraded forest. In each ...

Journal: :Remote Sensing 2016
Rasmus Revermann Manfred Finckh Marion Stellmes Ben J. Strohbach David Frantz Jens Oldeland

In many parts of Africa, spatially-explicit information on plant α-diversity, i.e., the number of species in a given area, is missing as baseline information for spatial planning. We present an approach on how to combine vegetation-plot databases and remotely-sensed land surface phenology (LSP) metrics to predict plant α-diversity on a regional scale. We gathered data on plant α-diversity, meas...

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه رازی - دانشکده علوم 1387

boron nitride semiconducting zigzag swcnt, $b_{cb}$$n_{cn}$$c_{1-cb-cn}$, as a potential candidate for making nanoelectronic devices was examined. in contrast to the previous dft calculations, wherein just one boron and nitrogen doping configuration have been considered, here for the average over all possible configurations, density of states (dos) was calculated in terms of boron and nitrogen ...

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