نتایج جستجو برای: species evenness

تعداد نتایج: 548668  

Journal: :The American naturalist 2001
G Stirling B Wilsey

Diversity (or biodiversity) is typically measured by a species count (richness) and sometimes with an evenness index; it may also be measured by a proportional statistic that combines both measures (e.g., Shannon-Weiner index or H'). These diversity measures are hypothesized to be positively and strongly correlated, but this null hypothesis has not been tested empirically. We used the results o...

2011
SHANNON L. PELINI MARK BOUDREAU NEIL MCCOY AARON M. ELLISON NICHOLAS J. GOTELLI NATHAN J. SANDERS ROBERT R. DUNN

Climatic change is expected to have differential effects on ecological communities in different geographic areas. However, few studies have experimentally demonstrated the effects of warming on communities simultaneously at different locales. We manipulated air temperature with in situ passive warming and cooling chambers and quantified effects of temperature on ant abundance, diversity, and fo...

2016
Lionel R. Hertzog Sebastian T. Meyer Wolfgang W. Weisser Anne Ebeling Han Y.H. Chen

Changes in producer diversity cause multiple changes in consumer communities through various mechanisms. However, past analyses investigating the relationship between plant diversity and arthropod consumers focused only on few aspects of arthropod diversity, e.g. species richness and abundance. Yet, shifts in understudied facets of arthropod diversity like relative abundances or species dominan...

2016
Sumit Srivastava R. P. Shukla

The grassy landscape of north-eastern Uttar Pradesh showed quite high species richness and a total of 287 plant species belonging to 183 genera under 53 families were encountered within the sampled communities. We categorized each of 31 locations under 12 disturbance types under two light regimes. Their effects were observed in relation to different diversity attributes of grassland communities...

2016
Thomas P McKenna Kathryn A Yurkonis

Plant performance is determined by the balance of intra- and interspecific neighbors within an individual's zone of influence. If individuals interact over smaller scales than the scales at which communities are measured, then altering neighborhood interactions may fundamentally affect community responses. These interactions can be altered by changing the number (species richness), abundances (...

Journal: :The Journal of animal ecology 2014
Amanda D Rodewald Rudolf P Rohr Miguel A Fortuna Jordi Bascompte

Ecological networks are known to influence ecosystem attributes, but we poorly understand how interspecific network structure affect population demography of multiple species, particularly for vertebrates. Establishing the link between network structure and demography is at the crux of being able to use networks to understand population dynamics and to inform conservation. We addressed the crit...

2017
Brent Mortensen Karen C. Abbott Brent Danielson

Trait-based theories of biodiversity consider interspecific tradeoffs among species-specific traits as prerequisites to maintaining community evenness, a component of species diversity. Such tradeoffs are commonly observed in plant communities, particularly in relation to traits associated with resistance to herbivory. Indeed, global experiments show that interspecific tradeoffs are common betw...

Diana Askarizadeh Mahdieh Mahmoudi Mohammad Hassan Jouri Tina Salarian,

Recent attitude of vegetation assessors is using of new ecologic approaches to evaluate and analyse the complex rangeland ecosystems. Plant diversity is the most important indices to assess the ecological changes of rangelands. In order to survey of plant indices of rangelands, two exclosure areas (long-term and mid-term) and a grazing area in rangelands of Javaherdeh (Ramsar, Iran) were select...

2007
Karen R. Hickman Justin D. Derner

We studied short-term (1–3 years) responses of plant species and functional group abundances, richness, evenness, diversity, and similarity following cessation of 25 years (1972–1997) of herbicide application in a remnant of Blackland Tallgrass Prairie in central Texas. Substantial increases in plant cover from 1998 to 2000 were observed for annual forbs (359%–900%), primarily attributable to f...

Journal: :بوم شناسی کشاورزی 0
نسیبه پورقاسمیان روح اله مرادی

introduction agricultural biodiversity has spatial, temporal and scale dimensions especially at agro-ecosystem levels. these agro-ecosystems that are used for agriculture are determined by three sets of factors: the genetic resources (biodiversity), the physical environment and the human management practices. most agricultural areas can be returned to their natural landscape after subsequent ge...

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