Home About us Contact
|
Home About us Contact | ||
|
|
||
Previous Autumn (previous + autumn)
Selected AbstractsBurying beetle Nicrophorus investigator reproduction on Pacific salmon carcassesECOLOGICAL ENTOMOLOGY, Issue 1 2006M. D. Hocking Abstract., 1.,In many undisturbed watersheds along the Pacific Rim, anadromous salmon (Oncorhynchus spp.) provide a predictable source of carrion to the riparian zone, largely due to horizontal transfer of salmon carcasses by bears (Ursus spp.) and other vertebrates. 2.,Burying beetles are important members of the north-temperate carrion fauna, and may utilise salmon carcasses and remnants for breeding. In this study, isotopic and observational data are reported that demonstrate previously unrecognised Nicrophorus investigator (Zetterstedt) reproduction on large salmon carcasses from five watersheds in coastal British Columbia. 3.,Stable isotope signatures (,15N and ,13C) of adult beetles collected in autumn indicate a diet of salmon origin in all but one individual from all watersheds, suggesting that this beetle,salmon association is widespread. Comparison of autumn isotope signatures to individuals collected randomly in summer suggests that isotope signatures represent the larval carrion source from the previous autumn rather than immediate adult diet. 4.,In a survey of N. investigator use of salmon carcasses from two watersheds, 35 broods were observed on chum and pink salmon carcasses, including 16 natural brood complexes containing over 100 larvae, and five ranging from 250 to 750 larvae. 5.,Overall, north-coastal populations of N. investigator breed on the rich and reliable salmon resource and may exhibit a system of communal breeding on these carcasses. This is most relevant when the dramatic reduction in salmon spawning biomass over the last century is considered. [source] Radial growth responses to drought of Pinus sylvestris and Quercus pubescens in an inner-Alpine dry valleyJOURNAL OF VEGETATION SCIENCE, Issue 6 2007Pascale Weber Abstract Question: Lower montane treeline ecotones such as the inner Alpine dry valleys are regarded as sensitive to climate change. In the dry Valais valley (Switzerland) the composition of the widespread, low altitude Pinus forests is shifting towards a mixed deciduous state. The sub-boreal P. sylvestris shows high mortality rates, whereas the deciduous sub-mediterranean Quercus pubescens is spreading. These species may act as early indicators of climate change. We evaluate this hypothesis by focusing on their differences in drought tolerance, which are hardly known, but are likely to be crucial in the current forest shift and also for future forest development. Methods: We used dendroecological methods to detect species-specific patterns in the growth response to drought. The relationship between radial growth of 401 trees from 15 mixed stands and drought was analysed by calculating response functions using yearly tree-ring indices and monthly drought indices. PCA was applied to the response ratios to discover spatial patterns of drought response. Results: A species-specific response to moisture as well as a sub-regional differentiation of the response patterns were found. While Quercus showed a response mainly to the conditions of the previous autumn and those of current spring, Pinus did not start responding before May, but showed responses throughout the whole summer. Quercus may restrict physiological activity to moist periods; growth of Pinus was much more dependent on prior growth. Conclusions: Given that the climate is changing towards (1) longer summer drought periods, (2) higher mean temperatures and (3) shifted seasonally of moisture availability, Quercus may benefit from adapting better to drier conditions. Pinus may increasingly face problems related to drought stress as it depends on summer moisture and has a smaller adaptive capacity due to its long-lived photosynthetic tissue. [source] Light rings in Chinese pine (Pinus tabulaeformis) in semiarid areas of north China and their palaeo-climatological potentialNEW PHYTOLOGIST, Issue 4 2006Eryuan Liang Summary ,,Light rings in conifer trees are characterized by a light-coloured, narrow latewood band of thin-walled tracheids. Most reports on light rings have been for subarctic and subalpine regions, and little is known about their occurrence in semiarid areas. ,,Dendrochronological methods were used to date the occurrence of light rings in Chinese pine (Pinus tabulaeformis) in the semiarid region of north China. The anatomical and chemical characteristics and the potential environmental controls of their formation were investigated. ,,Light rings in Chinese pine were dated to the year of their formation. The wall thickness and lumen diameter of the wood cells of light rings and reference rings were distinctly different. However, the configuration of the light-ring latewood cell walls was normal, although they were thinner than average, and their lignification had been completed normally. ,,The climate characteristics that result in light-ring formation appear to be ongoing severe drought from the previous autumn to July of the current year in conjunction with a warm summer, suggesting that light rings can be used as indicators for past drought events. [source] Long-term changes of aphid vectors of Barley yellow dwarf viruses in north-eastern Italy (Friuli-Venezia Giulia)ANNALS OF APPLIED BIOLOGY, Issue 1 2009P.G. Coceano Abstract Migrations of aphid vectors of Barley yellow dwarf viruses (BYDV) were monitored using a Rothamsted Insect Survey suction trap in Friuli-Venezia Giulia (north-eastern Italy). Catches from 1983 to 2002 were studied for trends, correlations of total catches of each year with those of previous years, correlations between the autumn and the spring + summer catches of the same year and between spring + summer catches of one year with catches of the previous autumn. Infectivity of autumn alates was studied using biological tests, and infectivity indexes were calculated for all vector species and for Rhopalosiphum padi alone. Colonisation of barley and proportion of infected plants were checked in a field close to the suction trap from 1992 to 2002 and related to trap catches. Catches were also correlated to acreage dedicated to cereal and fodder crops in the region. During the 20 years, 15 BYDV vector species were caught in the trap, but only five species were found consistently colonising barley plants during autumn. R. padi was the most numerous species in catches, while Sitobion avenae was the predominant colonising species in the barley field. Relatively to R. padi, S. avenae colonies were about six times more numerous than expected from catches. The yearly abundance of catches of most species did not change significantly during the 20 years, with a few exceptions, significantly correlated to changes in the acreage dedicated to cereal and fodder crops. There was a significant decrease of the autumn catches of both R. padi and the total of BYDV vectors. [source] | ||||||||||