Insect Pollinated Crops, Insect Pollinators and US Agriculture: Trend Analysis of Aggregate Data for the Period 1992–2009

In the US, the cultivated area (hectares) and production (tonnes) of crops that require or benefit from insect pollination (directly dependent crops: apples, almonds, blueberries, cucurbits, etc.) increased from 1992, the first year in this study, through 1999 and continued near those levels through 2009; aggregate yield (tonnes/hectare) remained unchanged. The value of directly dependent crops attributed to all insect pollination (2009 USD) decreased from $14.29 billion in 1996, the first year for value data in this study, to$10.69 billion in 2001, but increased thereafter, reaching $15.12 billion by 2009. The values attributed to honey bees and non-Apis pollinators followed similar patterns, reaching$11.68 billion and $3.44 billion, respectively, by 2009. The cultivated area of crops grown from seeds resulting from insect pollination (indirectly dependent crops: legume hays, carrots, onions, etc.) was stable from 1992 through 1999, but has since declined. Production of those crops also declined, albeit not as rapidly as the decline in cultivated area; this asymmetry was due to increases in aggregate yield. The value of indirectly dependent crops attributed to insect pollination declined from$15.45 billion in 1996 to $12.00 billion in 2004, but has since trended upward. The value of indirectly dependent crops attributed to honey bees and non-Apis pollinators, exclusive of alfalfa leafcutter bees, has declined since 1996 to$5.39 billion and $1.15 billion, respectively in 2009. The value of alfalfa hay attributed to alfalfa leafcutter bees ranged between$4.99 and $7.04 billion. Trend analysis demonstrates that US producers have a continued and significant need for insect pollinators and that a diminution in managed or wild pollinator populations could seriously threaten the continued production of insect pollinated crops and crops grown from seeds resulting from insect pollination

Postaci drgań płyt - analiza doświadczalna

Mode vibrations of plales - experimental analyses. In this paper results of the square MDF piate and circular saw blades examination with the use of the harmonic method to static identification of resonant frequencics and shapes of mode vibrations are presented. Obtained results reveled that for circular saws with large holes in a saw blade appeared two resonant frequencies for the same nodal number.Postaci drgań płyt - analiza doświadczalna. W pracy przedstawiono wyniki badań kwadratowej płyty MDF oraz piły tarczowej z zastosowaniem metody testu harmonicznego służącego do statycznego wyznaczania częstotliwości rezonansowych oraz towarzyszącym im postaciom drgań. Zaobserwowane wyniki pokazują, że dla pił tarczowych o dużych otworach w korpusie piły pojawiają się dwie częstotliwości rezonansowe dla tej samej liczby węzłowej

New design of circular saw blade body and its influence on critical rotational speed

Oscillation is an unwelcome state as it has adverse effects not only on the work piece but also on the tool. This paper deals with the problem of circular saw blade oscillation and the effect of modification of the circular saw blade body on the natural frequency as well as on the critical rotational speed. The calculation and experimental investigation of the natural frequencies and node shapes on two types of circular saw blades were carried out. Two methods used to determine the natural frequencies are presented: the first, modal analysis (FEM), a theoretical method, and the second, experimental measurement. The results of the investigation were used to compare the FEM and experimental methods and to show which modification achieved a higher critical rotational speed. Both methods were conducted on two circular saw blades for continual cutting with 36 teeth and slots

Farmlands with smaller crop fields have higher within-field biodiversity

Simple rules for landscape management seem elusive because different species and species groups are associated with different land cover types; a change in landscape structure that increases diversity of one group may reduce diversity of another. On the other hand, if simple landscape-biodiversity relationships do exist despite this complexity, they would have great practical benefit to conservation management. With these considerations in mind, we tested for consistent relationships between landscape heterogeneity and biodiversity in farmland (the cropped areas in agricultural landscapes), with a view to developing simple rules for landscape management that could increase biodiversity within farmland. Our measures of farmland heterogeneity were crop diversity and mean crop field size, where increases in crop diversity and/or decreases in mean field size represent increasing landscape heterogeneity. We sampled the abundance, and alpha, gamma and beta diversity of birds, plants, butterflies, syrphids, bees, carabids and spiders, in crop fields within each of 93 1 km × 1 km agricultural landscapes. The landscapes were selected to represent three gradients in landscape composition and heterogeneity: proportion of the landscape in crop, mean crop field size and Shannon crop type diversity of the farmland. We found that mean crop field size had the strongest overall effect on biodiversity measures in crop fields, and this effect was consistently negative. Based on our results we suggest that, if biodiversity conservation in crop fields is a priority, policies and guidelines aimed at reducing crop field sizes should be considered