Phytophthora species and oak decline - can a weak competitor cause significant root damage in a nonsterilized acidic forest soil?

Phytophthora species in general, and P. quercina in particular, have been suggested in several studies to be a contributing factor to the problem of oak decline in Europe. Although Phytophthora species are generally regarded as weak competitors, few studies of the pathogenicity of species causing root rot on oaks have hitherto been performed in natural, nonsterilized forest soils. This study describes the effects of seven southern Swedish isolates of P. quercina and one isolate of P. cactorum on root vitality of Quercus robur seedlings grown in a natural, nonsterilized, acidic forest soil. The pathogenicity of P. quercina and P. cactorum were tested using a soil infestation test. The climatic conditions applied were an attempt to simulate summer conditions in southern Sweden. Both species of Phytophthora caused a significant dieback of fine roots, and necrotic lesions on coarser roots, of Q. robur seedlings. Total and live root lengths were significantly lower in infected seedlings than in controls. No significant effects of Phytophthora on above-ground growth or leaf nutrient concentration were found. The results demonstrate that P. quercina and P. cactorum can cause substantial root dieback of seedlings of Q. robur in natural, acidic forest soils in competition with the inhabiting soil microflora under a mesic water regime

Landscape Analysis: What Are the Forefronts of Change in the US Hospitals?

Compilation of information is increasingly becoming more important for health organizations from financial and time aspects. By methodical study of adaptive systems, healthcare organizations can gain new insights of burdensome issues within the organization as well as healthcare delivery management. These actions have become more important with the changes in the healthcare environment in the last couple of decades where several external entities have impacts on healthcare organizations directly and/or indirectly. One of the most onerous tasks ahead of organizations is to anticipate these changes and prepare for them. Knowing the external environment can be the key to leading a successful and competitive health system. However, identifying and behaving toward all the external changes pose great time and resource challenges for organizations. Health organizations can posit the question of “what are the current external changes that have the power to affect them?” This study will take a look into emerging extrinsic changes for the US healthcare environment in different areas. A literature review will be performed in order to pinpoint the different contemporary change perspectives and their sub-criteria. In order to better illustrate these issues, Ishikawa diagram (cause-and-effect diagram) is used in this study

A conceptual model for the development of Phytophthora disease in Quercus robur

Here, a conceptual model is presented for the development of Phytophthora disease in pedunculate oak. The model is presented using the causal loop diagram tool and gives an overview of how various abiotic and biotic factors, such as soil moisture, nutrient availability and mycorrhizal colonization, may affect the reproduction and the infective capacity of soil-borne Phytophthora species, the susceptibility of the host and subsequent disease development. It is suggested that the link between the root damage caused by Phytophthora species and overall tree vitality is in the assimilation and allocation of carbon within the plants. The potential impact of environmental factors on these processes is discussed. The model is presented with reference to scenarios related to variation in soil moisture and nutrient availability. The need for species-specific validation of the model and the implications of the model are discussed