Drought is an inherent trait of most rangelands and sound management necessitates managers address two fundamental questions when facing a drought situation. The first question is, ‘‘what is the probability that a useful amount of precipitation will be received over the period of concern?’’ and the second question is, ‘‘if it does rain, what will the impact be in terms of quantity and quality o...

1. Perturbations to ecosystems have the potential to directly and indirectly affect species interactions, with subsequent impacts on population dynamics and the vital rates that regulate them. 2. The few long-term studies of common eider breeding ecology indicate that reproductive success is low in most years, interrupted by occasional boom years. However, no study has explicitly examined the d...

irrigated barley is grown on about 50,000 hectares in the warm agro-climate zone in the south of iran. the average grain yield of barley in these areas is 2,000 kg/ha. wide adaptability and high grain yield stability are important assets for barley varieties to be grown by farmers. zahak barley cultivar was initially selected from international barley germplasm received from cymmit and based on...

as water is the most restrictive factor in national agricultural production, it is necessary to take decreased water consumption and increased water us efficiency in crop production into consideration. nowadays, spring sugar beet production areas are concentrated in the region with water limitation and hence, the increase in spring production area contradicts the principle of water and soil con...

Understanding how climate influences ecosystems is complicated by the many correlated and interrelated impacting factors. Here we quantify climate effects on Calanus finmarchicus in the northeastern Norwegian Sea and southwestern Barents Sea. By combining oceanographic drift models and statistical analyses of field data from 1959 to 1993 and investigating effects across trophic levels, we are a...

Kentucky is located in a unique ecological situation between the cold winters of northern prairie states and the very mild winters of the deep-south. Though cold enough to stop most insect activity during mid-winter, the great variation in date of first frost, fall onset of continuous cold, and spring onset of general warm weather makes it particularly difficult to predict insect impact in any ...