rangeland ecosystems shift across dynamic thresholds between differentecological states in response to natural or human-induced factors. these differentecological states are the result of interactions among climate, soils, grazing history,and management practices. the notion of a single ‘‘pristine’’ final state is onlyconceptual in nature, and because of this, dynamic thresholds and the effects...

we apply the two-sector production function developed by ram (1986) to estimate the threshold regression model for iran, concerning the effect of government size on economic growth. three government size indicators are used to find out the different threshold points. the results show a non-linear relationship of the armey curve in iran, in which the threshold effects corresponding to total gove...

The zooplankton biomass and distribution were studied during two oceanographic cruises in NE part of the Persian Gulf in autumn 2012 (November) and summer 2013 (August) with 300 μmmesh net. Zooplankton samples were analyzed for biomass content. Zooplankton biomass expressed as mg m-3 dry wt., was greatest during summer cruise (mean of 18.8 ± 4.6 mg m-3 dry wt.). The mean zooplankton bioma...

many studies on cold environments have been developed over the past two decades. highmountain freshwater presents high variability of nutrients and chemico-physical parameters, showing variations of ph, oxygen concentration, metals and temperature throughout the year. national park of sierra nevada (granada, spain) (37°032 n 03°182 w), has almost 40 lakes that are reported to be both endemic an...

the length-weight relationships, (lwrs) were calculated for 14 fish species belonging to five families (cyprinidae, cobitidae, nemacheilidae, salmonidae, and gobiidae) collected from the tajan river, north of iran. significant length-weight relationships with high correlation coefficients were found for all species.

There are many unavoidable noise interferences in image acquisition and transmission. To make it better for subsequent processing, the noise in the image should be removed in advance. There are many kinds of image noises, mainly including salt and pepper noise and Gaussian noise. This paper focuses on the research of the Gaussian noise removal. It introduces many wavelet threshold denoising alg...

the future of biomass energy in the global energy system depends on many major factors, among others on the attitude of society in rural areas to the biomass energy and the renewable energy resources. biomass energy plays increasing role in rural areas with its contribution to the self sufficiency of people in the countryside. the paper deals with the analysis the opportunities of utilization o...

In 2009, the European Commission estimated that 88% of monitored marine fish stocks were overfished, on the basis of data that go back 20 to 40 years and depending on the species investigated. However, commercial sea fishing goes back centuries, calling into question the validity of management conclusions drawn from recent data. We compiled statistics of annual demersal fish landings from botto...

Ecosystems may shift abruptly between alternative states in response to environmental perturbations. Early warning indicators have been proposed to anticipate such regime shifts, but experimental field tests of their validity are rare. We exposed rocky intertidal algal canopies to a gradient of press perturbations and recorded the response of associated assemblages over 7 years. Reduced cover a...