Low Winter Precipitation Research Articles

The Mesolithic-Neolithic transition in western Scotland and its European context

The transition is considered in terms of four related questions: (i) HOW did the shift from foraging to farming happen? (ii) WHY did it happen? (iii) WHEN did it happen? (iv) WHY did it happen WHEN it did? The adoption of farming coincided with a shift to a more continental-type climate with lower winter precipitation, which improved the prospects for cereal cultivation. It is sug- gested that this was a key factor in the transition from Mesolithic to Neolithic across north-west Eu- rope as a whole.

Turnover and fate of 15N-labelled cattle slurry ammonium-N applied in the autumn to winter wheat

The fate of 15NH 4-N labelled cattle slurry applied before sowing in September of a winter wheat crop was studied on a loamy sand soil. The aim was to quantify immobilization of slurry NH 4-N into microbial biomass, the speed at which nitrate derived from the slurry NH 4-N was transported down the soil profile, and the utilization of slurry NH 4-N by the winter wheat crop. Cattle slurry was applied at a rate corresponding to 75 kg NH 4-N ha −1 , with very little loss by volatilization (<4%) due to rapid incorporation by ploughing. The slurry amendment resulted in a doubling of soil surface CO 2 flux, an index of microbial activity, over non-amended soil within the first c. 2 weeks, but ceased again after c. 4 weeks, due to depletion of the easily degradable substances, e.g. volatile fatty acids, in the slurry. Nitrification of the applied NH 4-N was fast and complete by 3 weeks from application, and at this time, the maximum immobilization of slurry NH 4-N into the microbial biomass (23% of applied 15NH 4-N) was also observed, although no significant increase in total microbial biomass was observed. Rapid turnover of the microbial biomass quickly diluted the assimilated 15N, with only 6% of applied 15NH 4-N remaining in the microbial biomass by next spring. Downwards transport of nitrate was rapid in spite of lower than normal precipitation, and slurry-derived 15NO 3-N appeared in ceramic suction cups installed at 60 cm depth already 2 months after slurry application. Due to the unusually low winter precipitation in the experimental year, wheat yields were high, and the recovery of N in above-ground plant biomass derived from slurry NH 4-N at harvest reached 32%. An additional 45% of the applied slurry NH 4-N could be found in the soil to a depth of 100 cm (mostly in organic form in the plough layer), indicating that 23% had been lost by leaching or in gaseous form. It was concluded that although significant immobilization of slurry NH 4-N did occur, this was not sufficient to prevent leaching of slurry-derived N over the winter and that the relatively high recovery of slurry-derived N in the wheat crop was due partly to lower than normal winter percolation and partly to a relatively high rooting depth on this particular site.

Survival of downy brome (Bromus tectorum) seed in four environments

Downy brome is one of the most troublesome winter annual weeds in winter wheat-fallow rotations in the central Great Plains. A 3-yr seed burial study was initiated to determine how long downy brome seed remained germinable when placed on the soil surface or 2.5 cm deep at four different times in four environments. Only 1 to 7% of the downy brome seed survived after 1 yr on the soil surface in chemical fallow and stubble mulch when deposited in August, but survival varied in September, October, and November. In 1970, a year with low fall and winter precipitation, 36 to 46% of the seed placed on the soil surface of chemical fallow in September, October, and November survived, compared with 1 to 8% for stubble mulch tillage. Early spring tillage covered more seed with soil, and downy brome seed survival decreased. When fall and winter precipitation was normal, stubble mulch and chemical fallow had 1 to 20% germinable seed remaining. Induced dormancy existed in some years. More downy brome seed survived when placed on the soil surface of crested wheatgrass sod (14 to 50%) than on smooth brome sod (0 to 36%). No differences existed among environments when downy brome seed was buried 2.5 cm deep. Only 0.4% of downy brome seed buried 2.5 cm survived after 1 yr when averaged across all environments.

Paleoclimate, controls on Upper Devonian source rock sequences and stacked extinctions

High quality (&gt;2% TOC) Upper Devonian source rocks are developed in several sequence types. The commonest type, accounting for 70% of the studied examples is the transgressive sequence with a basal hiatus. Others include shallowing upward sequences (12%), lacustrine sequences in fault-controlled basins (7%), distal slope sequences (7%), and evaporite capped sequences (4%).Starting from the synthesis of Johnson, Klapper, and Sandberg (1985) it has been possible to demonstrate correlativity of Upper Devonian transgressive episodes globally. The marked association of epeiric sea Upper Devonian source rocks with transgressions heightens interest in their causation. Could they have been produced by glacio-eustatic sea-level change as Stanley (1984; 1988) implies? Quantitative paleoclimate modeling and isotopic paleotemperatures for the Upper Devonian suggest not. Modeling using CCM1 at NCAR, including five year seasonal cycles, suggests the absence of any large southern hemisphere ice volume. Because much of the Upper Devonian land mass was either in equatorial or high latitude regions, there was little development of monsoonal climates. Midlatitude cyclonic activity was also much less than at present, meaning less polar transport of moisture and drier polar areas. Precipitation maxima largely coincided with topographic elevations. In contrast to the Late Ordovician to earliest Silurian, there was no Upper Devonian perennial snow cover even over the high latitude southern land mass. This was in spite of winter land temperatures as low as -40°. in eastern Gondwana. In that area and elsewhere, there was thin winter snow cover which melted in late spring resulting in no build-up of snow cover to produce glaciation. This was mainly the consequence of low winter precipitation in Gondwana. High latitude sea surface temperatures were certainly cold enough to displace or exclude some organisms. However, in low latitude areas where Upper Devonian extinctions also took place, modeled sea surface temperatures range between 27° and 34°. Such areas would have been refuges for any organisms displaced by cold, high latitude waters. The higher temperature values of low latitudes are convergent with the isotopic paleotemperatures determined by Brand (1989) using well preserved Upper Devonian brachiopods. Brand's determinations suggest temperatures even reaching lethal values for many plankton (37°). The extinction of reefs by the close of Frasnian time could have been partly a result of such elevated temperatures. Stacked extinctions of conodonts (Ziegler and Lane, 1987) and acritarchs may have been a further result. The loss of reefs, an important consumer of plankton, may have permitted a relative increase in plankton abundance crossing from more oceanic areas into epeiric seas, possibly contributing to high quality source rock deposition.

Influence of Fertilizer, Irrigation, and Non‐Growing Season Precipitation on Soil Nitrate‐Nitrogen under Corn

AbstractCorn (Zea mays L.) production requires large amounts of N fertilizer, which may be lost due to leaching or denitrification. Prediction of the amount lost would be helpful in minimizing these losses. A field experiment was conducted to investigate the effects of fertilization, irrigation, and non‐growing season precipitation on soil NO3‐N under corn in southwestern Quebec from 1984 to 1987. The high rate of fertilization (400 kg N ha−1, 300 kg P25 ha−1, 400 kg K2O ha−1) over the normal rate (170 kg N ha−1, 100 kg P25 ha−1, 170 kg K2O ha−1) significantly increased soil NO3‐N during the growing season, and a residual effect of fertilizer rate on soil NO3‐N levels was noted in 2 of 3 yr during the non‐growing season. The high rate of fertilization, however, did not increase NO3‐N accumulation in the soil profile over the normal rate of fertilization in successive years. Irrigation significantly decreased soil NO3‐N during the growing season. At the normal rate of fertilization, gains of soil NO3‐N over winter were found with lower winter precipitation. At the high rate of fertilization, however, losses of soil NO3‐N over winter occurred in 2 of the 3 yr. The changes in NO3‐N in the rooting zone over winter depended upon the precipitation received during the preceding winter and the amount of NO3‐N in the soil the previous fall.

Glacier-front variations of outlet glaciers from Jostedalsbreen and climate in the Jostedalsbre region of western Norway in the period 1901-80

This paper presents a comparison of glacier-front variations for three outlet valley glaciers from Jostedalsbreen with the climate at adjacent meteorological stations in the 1901-80 period. From 1901 to 1930 the front of the valley glaciers remained in approximately the same position. Warm summers in the 1930s and 1940s and low winter precipitation in the 1930s, however, caused an extensive retreat of the glaciers from the mid 1930s. Fåbergstølsbreen and Stegaholbrccn reached their maximum retreat c. 20 years later than Brigsdalsbreen. Since the 1950s the front of Brigsdalsbreen has experienced a net advance as a response to a general increase in winter precipitation, except the years around 1960, and an average 0.7°C decrease in summer temperature. The response time of Brigsdalsbreen is 2-3 years, while the average response time of Fåbergstølsbreen and Stegaholbreen is calculated to c. 24 years.

Multiple effects of precipitation on Salix lasiolepis and populations of the stem‐galling sawfly, Euura lasiolepis

AbstractRelatively low winter precipitation (e.g., 18–28 cm from October to May compared to 45 to 65 cm) caused reduced growth of the arroyo willow, Salix lasiolepis, with number of shoots per stem initiated and shoot length reduced. Resources were reduced for the stem‐galling sawfly, Euura lasiolepis, which declined in numbers after the relatively dry winter of 1980–81. Sawfly phenology was advanced relative to willow phenology in the 1981 generation, causing an additional reduction in resource availability. These direct effects of precipitation on the sawfly were increased by indirect effects on survivorship of the 1981 generation. Egg death in galls increased on water‐stressed willow plants, forming the major mortality in the generation. This resulted in very low survival in the generation and an even lower population in the 1982 generation, even though resources recovered after high precipitation during the 1981–82 winter (46.7 cm). An experiment using high, medium, and low water treatments on potted willow plants demonstrated that the effects on willows and sawflies could be reproduced using only water as a variable.

Latest Pleistocene and Holocene palaeoenvironment of Japan and its marginal sea

Analyses of pollen and radiolarian abundance variations in a deep-sea core from the Sea of Japan indicate that major vegetational changes on mainland Japan during the last 80,000 years coincided with events of similar magnitude offshore in the marginal sea. On land, dry cold temperate conditions alternate with wet cold temperate periods throughout most of the last glacial period (80,000–10,000 yr B.P.). Offshore, during glacial times of low winter precipitation, the radiolarian fauna was dominated by assemblage similar to those present today along the Subarctic Front and throughout much of the Subpolar Gyre associated with cold winter and summer sea-surface temperatures. During most of the high-precipitation stadials, the dominant radiolarian assemblage was comparable with that existing in today's Sea of Okhotsk, associated with cold winter and cool summer sea-surface temperatures. On the western coast of Honshu warmer temperate conditions throughout the Holocene were associated with a marine faunal assemblage similar to that living in waters overlying the core site today. Radiolarian abundance levels (productivity) were lower during most of the last glacial period compared to Holocene values. The presence of radiolaria throughout all but a portion of the early stage of the last glacial interval indicates that, although restricted, some degree of exchange between the southern Sea of Japan and North Pacific waters took place throughout most of the last glacial period. These data place major constraints on local reconstructions of sea level and of climate on the adjacent coast of Honshu during this time.

Trophic Relationships among Small Mammals in a Chilean Semiarid Thorn Scrub Community

The food habits of seven species of small mammals were analyzed for a 15-month period during a live-trapping and snap-trapping study in a semiarid thorn scrub community in north-central Chile. The species included four cricetids (Akodon olivaceas, A. longipilis, Phyllotis darwini, and Oryzomys longicaudatus), two caviomorphs (Octodon degus and Abrocoma bennetti), and a didelphid (Marmosa elegans). The community was characterized by a semiarid mediterranean climate with low winter precipitation and frequent fog formation. Dominant physical features included high cover of spiny evergreen and drought-deciduous shrubs, low ground cover of herbaceous plants, and open sandy areas. Year-round food habit trends indicated three functional trophic guilds and one omnivorous species. A. longipilis and M. elegans were insectivorous, O. degus and A. bennetti were herbivorous, P. darwini and O. longicaudatus were granivorous, and A. olivaceus was omnivorous. This pattern of trophic specialization agrees generally with other studies of various species in the Chilean region, and suggests contrasts with patterns in the mediterranean and desert communities of North America and Argentina.

Seasonal Weather Trends in Relation to Fluctuations of the Jan Mayen Glaciers Since 1920

AbstractThe meteorological records for Jan Mayen have been examined on a seasonal basis in order to obtain a clearer understanding of the fluctuations of the Beerenberg glaciers from 1920 to the present day. Summer and winter have been arbitrarily defined as including those months with mean monthly temperatures, at sea-level, above and below 0°C., respectively. The results indicate that the retreat of Sørbreen prior to 1940 was associated with high summer temperatures and high summer precipitation, and relatively low winter precipitation. A rapid rise in winter precipitation followed, which culminated about 1950. The advance of Sørbreen since about 1954 is thought to have been caused by this rapid rise of precipitation and has also been associated with a slight drop in summer temperature, which is considered to be of secondary importance. The most recent trends of rising summer temperature since 1956 and falling winter precipitation since 1958, if they continue, must lead to a renewed retreat of the glaciers. Studies on Sørbreen in the summer of 1963, which show that the recent advance has ceased, support this view.

Seasonal Weather Trends in Relation to Fluctuations of the Jan Mayen Glaciers Since 1920

AbstractThe meteorological records for Jan Mayen have been examined on a seasonal basis in order to obtain a clearer understanding of the fluctuations of the Beerenberg glaciers from 1920 to the present day. Summer and winter have been arbitrarily defined as including those months with mean monthly temperatures, at sea-level, above and below 0°C., respectively. The results indicate that the retreat of Sørbreen prior to 1940 was associated with high summer temperatures and high summer precipitation, and relatively low winter precipitation. A rapid rise in winter precipitation followed, which culminated about 1950. The advance of Sørbreen since about 1954 is thought to have been caused by this rapid rise of precipitation and has also been associated with a slight drop in summer temperature, which is considered to be of secondary importance. The most recent trends of rising summer temperature since 1956 and falling winter precipitation since 1958, if they continue, must lead to a renewed retreat of the glaciers. Studies on Sørbreen in the summer of 1963, which show that the recent advance has ceased, support this view.