Problems in Estimating Impacts of Future Climate Change on Midwestern Corn Yields

Recent studies of trends in Midwestern precipitation show marked increases over the last 50 years of the 20th Century, and most climate models project that future rainfall in the Corn Belt will be increased further. During five years, 1988–1991 and 1994, field tests were conducted on agricultural test plots in central Illinois, an area typical of the Corn Belt, to discern how corn yields reacted to varying levels of added rainfall (+10%, +25%, and +40%) during the growing season. The best treatment over the five years was a 40% rain increase, with an average yield increase of 9%. Its yield increase was up to 34% in a hot-dry year, but below that of natural rainfall in a wet year as were the yields of the other lesser increases. The average yield changes from the three treatments were not statistically significantly different. Major interannual yield differences were found in the yields for each rain treatment, reflecting how rain timing and temperatures also have major effects on yields. A 40% summer rain increase has little influence if natural rains do not occur in the high stress period of mid summer. The plots results show that only small average increases in corn yields occur from growing season rain additions in the 10% to 40% range, except in dry years. Weather-crop yield regression models incorporating the same rain increases predict greater yield increases than found in these field tests. This suggests that future yields projected for a wetter climate using yield-weather models may be over-estimated. The plot sample size is small but conditions sampled in the five years represented 43% of all past 97 growing seasons in central Illinois and extremely good and bad weather years, which resulted in large between-year yield differences. Hence, the experimental results provide useful information about how increased rainfall may affect future corn yields, especially since the sample included three of the five types of dry growing seasons found in the area's climate since 1900.     

Linkage between microzooplankton grazing and phytoplankton growth in a Gulf of Mexico estuary

Microzooplankton dilution grazing experiments were conducted with water collected from Pensacola Bay, Florida (USA) on 12 dates at 2 sites. Statistically significant grazing rates were observed in 22 of 24 experiments. Grazing rates in Upper Bay and Lower Bay were similar averaging 0.54 and 0.51 d⁻¹, respectively. Phytoplankton growth rates were also similar at the two sites, averaging 1.02 and 1.00 d⁻¹ at Upper Bay and Lower Bay, respectively. Phytoplankton growth rates usually exceeded grazing rates by about a factor of two, though microzooplankton grazing represented a significant mortality for phytoplankton. The literature suggests a linkage between phytoplankton growth and microzooplankton grazing that spans a wide variety of aquatic environments. While individual growth and grazing rates were variable, growth frequently exceeded grazing by about two-fold. This implies that the role of microzooplankton is similar across a wide variety of aquatic systems.     

Inundation,sea-level rise and transition from Neolithic to Bronze Age cultures,Yangtze Delta,China

Petrological, faunal and floral information derived from a new drill core taken in the Yangtze delta, coupled with data from borings recovered earlier, record a marked transition to warmer, wetter conditions which resulted in widespread inundation of the delta about 4000 years ago. Also identified for that time on the delta plain is a major discontinuity between the Neolithic Liangzhu and Bronze age Maqiao cultures. The cultural discontinuity is indicated by: (1) absence of in situ material between the two at ∼4000 yr B.P.; (2) missing Maqiao material in strata above many Liangzhu sites; (3) less sophisticated Maqiao material than in the older Neolithic phase; and (4) notably fewer Maqiao sites in more restricted areas of the delta plain. It is of note that the change from the Liangzhu to the younger Maqiao does not show an increasingly complex cultural advancement of the type generally associated with the foundation of Chinese civilization. We propose that this cultural discontinuity was caused by the interplay of increased environmental stress and new population migrations into the delta. © 1999 John Wiley & Sons, Inc.     

Identifying and Removing the Silences of Roma Culture in Polish School Texts

The Roma are the largest and, some scholars would argue, the most marginalized group in Europe, an observation evident in an examination of school texts for Polish children. Using the concept of the “geographies of silence,” we discuss the nature of text and graphical silences and the reasons behind the paucity of text, photo, and map coverage. We conclude by presenting photos that could be used in future texts to better inform Polish youth about a much-neglected part of their culture.     

Fourier transform infrared microspectroscopic characterization of Neoproterozoic organic microfossils from the Fifteenmile Group in Yukon,Canada

Conventional and synchrotron radiation‐based (SR) Fourier transform infrared microspectroscopies (micro‐FTIR) were applied to four types of ~ 810 Ma organic‐walled microfossils together with diffuse organic matter (OM) and one irregularly shaped structure from the Fifteenmile Group, in Yukon, Canada, for their chemical characterization. The microfossils comprised one filamentous type and three coccoidal types. Micro‐FTIR mapping analysis revealed the micrometer‐scale, spatial distribution of organic components (aliphatic C‐H bonds) and carbonate in the microfossils. Based on comparisons of CH₃/CH₂ peak height ratios (R_3/2) and morphologies of the microfossils (without the diffuse OM) to those of previously described Proterozoic microfossils, possible affinities of the microfossils are suggested, as follows. Palaeolyngbya? and Glenobotrydion belong to bacteria. Myxococcoides is not clearly characterized due to the significant mixing with diffuse OM containing abundant aliphatic C‐H groups. The irregularly shaped structure may represent a eukaryote. The diffuse OM may represent a mixture of decomposed microbial cells and extracellular polymeric substances (EPS). SR micro‐FTIR measurements of two coccoid types (Glenobotrydion and Unnamed Coccoid Form D) revealed that the R_3/2 values of the internal spots with wall structures are similar to those without wall structures in Glenobotrydion: those values from Unnamed Coccoid Form D were different. The results suggest that these two coccoids are different chemically as well as morphologically. Micro‐FTIR characterization of the organic‐walled microfossils together with morphological analysis provides new insight into their biological affinities.     

Distribution and geochronology of Oregon Plateau (U.S.A.) flood basalt volcanism: The Steens Basalt revisited

The timing and petrogenesis of mid-Miocene flood basalt volcanism in the northwest United States has been extensively addressed, yet the chemical characteristics and temporal details of the Steens Basalt, exposed on the Oregon Plateau, are poorly defined. Steens Basalt volcanism has generally been accepted to have occurred at ∼ 16.6 Ma, coeval and/or just prior to the onset of Columbia River Basalt Group volcanism to the north. New major and trace element analyses and nine ⁴⁰Ar/³⁹Ar ages ranging from 15.51 ± 0.28 to 16.58 ± 0.18 Ma were obtained on Oregon Plateau flood basalt lava flows from stratigraphic sections in close proximity to Steens Mountain. Additionally, new ⁴⁰Ar/³⁹Ar ages were obtained on the uppermost and thirty-first lava flow down from the top of the ∼ 1 km section of Steens Basalt exposed at Steens Mountain and yield eruption ages of 16.59 ± 0.10 and 16.55 ±0.10 Ma, respectively. Field relations between these basalt sections suggest that multiple eruptive centers were present in the vicinity of Steens Mountain.     

Practical use of video imagery in nearshore oceanographic fieldstudies

An approach was developed for using video imagery to quantify, in terms of both spatial and temporal dimensions, a number of naturally occurring (nearshore) physical processes. The complete method is presented, including the derivation of the geometrical relationships relating image and ground coordinates, principles to be considered when working with video imagery and the two-step strategy for calibration of the camera model. The techniques are founded on the principles of photogrammetry, account for difficulties inherent in the use of video signals, and have been adapted to allow for flexibility of use in field studies. Examples from field experiments indicate that this approach is both accurate and applicable under the conditions typically experienced when sampling in coastal regions. Several applications of the camera model are discussed, including the measurement of nearshore fluid processes, sand bar length scales, foreshore topography, and drifter motions. Although we have applied this method to the measurement of nearshore processes and morphologic features, these same techniques are transferable to studies in other geophysical settings     

The wind-speed measurement capability of spaceborne radar altimeters

This study represents an attempt to quantitatively assess the capability of a spaceborne radar altimeter to infer ocean surface wind speeds from a measurement of the backscattered power at vertical incidence. The study uses data acquired during 184 near overflights of NOAA data buoys with the GEOS-3 satellite radar altimeter and encompasses a wind-speed range from less than 1 to 18 m/s. An algorithm is derived from the data comparison for converting measurements of the normalized scattering cross section of the ocean surface at 13.9 GHz into estimates of the surface wind speed at the standard anemometer height of 10 m. The algorithm is straightforward and potentially useful for on-board processing of raw altimeter data for the purpose of providing real-time estimates of surface wind speed. For winds in the range of 1 to 18 m/s, the mean difference between the altimeter-inferred winds and the buoy measurements is negligible while the standard deviation of the difference is 1.74 m/s.