Autumn Fall Research Articles

Dynamics of nitrate leaching and 15N turnover in intensively fertilized and irrigated basket willow grown in lysimeters

A 13-month experiment was conducted to study the dynamics of nitrate leaching from basket willow ( Salix viminalis), and the fate of fertilizer-N applied after the growing season. Lysimeters with or without plants were supplied daily with water and liquid fertilizer. Nitrate leaching and transpiration were quantified, as well as leaf-, stem- and root growth and N-uptake. 15N-labelled fertilizer was applied in autumn after leaf fall for the determination of the fate of fertilizer-N. The N-uptake by the willow plants was high during the summer and was correlated with transpiration. It decreased drastically in autumn in the absence of transpiration, but was still significant, which was also the case in early spring, the following year. A leaf rust infection during autumn led to a 9-times increase in nitrate leaching, whereas transpiration was reduced by 26%. After a fertilizer application for 10 days after leaf fall in autumn, an average of 8% of the fertilizer-N was taken up by the plants, and 32% was unaccounted for, of which a large portion was likely to be lost through denitrification. Recalculated on a hectare basis, the whole-season nitrogen budget shows that 191 kg N / ha was applied as liquid fertilizer during the first season, of which 98 kg N / ha was taken up by plants, 69 kg N / ha was leached, and 24 kg N / ha was unaccounted for (i.e. possibly denitrified). The amount of nitrogen taken up by plants or lost from the system (possibly through denitrification) corresponded to 36 kg N / tonnes of dry stem wood produced.

Population dynamics and morphometries of Gammarus pulex L.: evidence of seasonal food limitation in a freshwater detritivore

SUMMARY. 1. Seasonal changes in population size structure of Gammarus pulex L. in a Cotswold stream appeared to indicate a growth check in late summer.2. The relationships between dry weight and body length, and between the number of primary flagellar segments on the first antenna and either dry weight or body length provided further evidence of a reduction in growth in mid and late summer.3. Body fat content was minimal (4% of dry weight) at the end of summer, when large particulate organic detritus was scarce or of poor quality, and maximal in late winter (17.9% dry weight in females; 9.4% in males), after a period of high food availability. In a field experiment, the fat content of animals in summer was raised to levels typical of winter by providing high quality food.4. Field and experimental evidence together strongly infer that this population of G. pulex was subject to severe food limitation from early summer until leaf fall in autumn.

Emission of nitrous oxide from temperate forest soils into the atmosphere

N2O emission rates were measured during a 13-month period from July 1981 till August 1982 with a frequency of once every two weeks at six different forest sites in the vicinity of Mainz, Germany. The sites were selected on the basis of soil types typical for many of the Central European forest ecosystems. The individual N2O emission rates showed a high degree of temporal and spatial variabilities which, however, were not significantly correlated to variabilities in soil moisture content or soil temperatures. However, the N2O emission rates followed a general seasonal trend with relatively high values during spring and fall. These maxima coincided with relatively high soil moisture contents, but may also have been influenced by the leaf fall in autumn. In addition, there was a brief episode of relatively high N2O emission rates immediately after thawing of the winter snow. The individual N2O emission rates measured during the whole season ranged between 1 and 92 μg N2O-N m−2 h−1. The average values were in the range of 3–11 μg N2O-N m−2 h−1 and those with a 50% probability were in the range of 2–8 μg N2O-N m−2 h−1. The total source strength of temperate forest soils for atmospheric N2O may be in the range of 0.7–1.5 Tg N yr−1.

The Proportion of Empneuston and Total Atmospheric Inputs of Carbon, Nitrogen and Phosphorus in the Nutrient Budget of a Small Mesotrophic Lake (Piburger See, Austria)

AbstractLitter and wet traps were employed to determine the inputs of coarse organic matter (empneuston), total organic carbon, total nitrogen and phosphorus through dry fallout and precipitation to a soft‐water, mesotrophic lake. The dispersal of airborne material over the lake surface was investigated, and a method for the calculation of total input was developed. The component of the particulate matter larger than 1 mm contained the largest proportion of organic carbon, while the dissolved and the fine particle (smaller than 1 mm) fractions made greater contributions to the inputs of nitrogen and phosphorus compounds. The importance of the large particle fraction of the airborne organic matter in the lake's nutrient budget during the autumnal fall of litter was confirmed. However, the maximum total airborne input seems to occur during spring and summer. The input of phosphorus compounds through the atmosphere to small forest lakes is large compared to that from other sources. Airborne material accounts for 39% of the total phosphorus loading.

The seasonal cycle of condition in the pollan, Coregonus autumnalis pollan Thompson, of Lough Neagh, Northern Ireland

The length–weight relationship for Lough Neagh pollan was log W= 3·2 log L–2·24. Covariance analysis indicated that there were no differences between the sexes, with maturity, or between years. While a seasonal cycle in relative condition was in phase with gonad development during late summer and autumn, changes in somatic condition presented a more complex pattern. Somatic condition increased in spring, as did the quantity and diversity of food consumed. Despite good conditions for feeding and growth, there was an autumn fall in somatic condition, caused by the diversion of energy to gonad growth.

WATER QUALITY IN AGRICULTURAL WATERSHEDS: IMPACT OF RIPARIAN VEGETATION DURING BASE FLOW1

ABSTRACT: Water quality was monitored for 17 months during base flow periods in six agricultural watersheds to evaluate the impact of riparian vegetation on suspended solids and nutrient concentrations. In areas without riparian vegetation, both instream algal production and seasonal low flows appeared to be major determinants of suspended solids, turbidity, and phosphorus concentrations. Peak levels of all parameters were reached during the summer when flows were reduced and benthic algal production was high. Similar summer peaks were reached in streams receiving major point inputs but peaks occurred downstream from the input. Instream organic production was less important in regulating water quality in areas with riparian vegetation and permanent flows. Concentrations of suspended solids remained relatively constant, while phosphorus and turbidity increased in association with leaf fall in autumn. Intermittent flow conditions in summer increased the importance of instream organic production in controlling water quality, even when riparian vegetation was present. Efforts to improve water quality in agricultural watersheds during base flow should emphasize maintenance of riparian vegetation and stable flow conditions.

A pear rootstock trial in Israel

The pear cultivars ‘Spadona Estiva’, ‘Coscia’, ‘Beurré Superfin’ and a ‘Bartlett’ clone of South African origin (termed ‘Bartlett Sport’) were tested on 5 quince rootstock types, 5 Pyrus species and on 5 or 30 cm long interstocks of the pear cultivars ‘Bergamotte Esperen’ and ‘Spadona Estiva’ on quince MA, while ‘Dr. Jules Guyot’ was used as an interstock on ‘Bartlett’ seedlings. At the age of 10 years only ‘Spadona Estiva’ showed no signs of decline on quince rootstocks, ‘Coscia’ showed moderate decline, while the remaining cultivars had already declined severely. When the trunk circumference of ‘Beurré Superfin’ trees on the various quince clones was taken as an indicator for the degree of graft incompatibility, a negative correlation was found between this parameter and cyanogenic glycoside content in the stem bark of ungrafted quince plants belonging to the same clones. Pear interstocks on quince MA rootstocks did in some cases increase crops compared to the same quince alone, but did not prevent the decline of ‘Beurré Superfin’ and Bartlett Sport' on quince. The most vigorous and most prolific rootstock was Pyrus betulaefolia. However, with ‘Spadona Estiva’ differences in vigor between the rootstocks were only small and crops on the Israeli quince CI 7 were similar to those on Pyrus betulaefolia, but fruit size was larger on quince. Cropping of this cultivar at the age of 4 years was closely related to the intensity of flowering, whereas with ‘Coscia’ this relation was much less evident. Leaf fall in autumn and the opening of the vegetative buds of ‘Beurré Superfin’ in spring were earlier on quince than on Pyrus rootstocks.

Some physical and chemical effects of the Cow Green (Upper Teesdale) impoundment

SUMMARY. The paper describes observations on water temperature and dissolved oxygen in Cow Green reservoir and also changes caused by impoundment to temperature, chemistry, dissolved oxygen and the discharge regime of the River Tees immediately downstream of the dam.Impoundment and river regulation have considerably smoothed‐out fluctuations in discharge of the Tees and have ehminated the very low and very high discharges which were characteristic of the natural river.Reservoir water levels show an annual pattern of draw‐down during summer, refilling in autumn and overflow during winter and spring. Tliermal stratification of the reservoir occurs rarely and is generally of short duration. Water temperatures at mid‐reservoir correspond closely to those of water discharged from the reservoir. The temperature regime in the river downstream is modified as follows: reduction in amplitude of annual temperature fluctuations by 1–2°C, marked reduction of diel fluctuations, (3) delay of the spring rise in water temperature by 20–50 days and of the autumn fall by 0–20 days. These temperature changes could reduce the annual maintenance ration of a 10 g brown trout (Salmo trutta L.) by about 15% and delay the annual peak of metabolism by about 1 month. The effect upon growth rate of trout would be negligible. Fluctuations in ionic content at the reservoir inflow are comparatively large and can be related approximately to river discharge. Fluctuations at the outflow are smaller and appear to be largely seasonal. Regulation has not appreciably altered the dissolved oxygen content of the River Tees.

Innate seasonal oscillations in the rate of milk secretion in goats.

1. When goats were kept in continuous milk production for 2-4 yr the rate of milk secretion oscillated in a sinusoidal fashion with a mean wavelength of 49.7 +/- 1 weeks, being highest in summer and lowest in winter.2. Milk [Cl] tended to be higher in summer and [protein] highest in winter but there were no seasonal changes in [fat], [lactose], [Na] or [K].3. There were no seasonal oscillations in body weight but the udders were larger in summer than in winter although this did not solely account for the changes in milk yield.4. Although the autumnal fall in yield and the rise in the spring coincided with the breeding season, seasonal variations also occurred in two ovariectomized animals.5. Seasonal fluctuations were independent of diet, occurring equally in animals that had never eaten grass but were fed continuously on dry feed and hay ad libitum.6. Annual oscillations in yield and udder size but not [protein] and [Cl] were also exhibited in two goats kept in a constant temperature chamber at 14 +/- 2 degrees C, fed every 2 hr and subjected continuously to 16 hr light and 8 hr dark. These observations have so far persisted for 2 yr in one goat and for 3 yr in the other. However, the wave-length was reduced to 45 +/- 1 weeks. Oestrus was suppressed for 2 years.

Survival and reproduction of the musselXenostrobus securis(Lam.) (Mollusca: Bivalvia: Mytilidae) in a Western Australian estuary

Summary The Swan estuary is subject to extreme temporal and spatial variations in salinity. Downstream populations of the mussel Xenostrobus securis (Lamarck, 1819) are exposed to a seasonal range from 1·5‰. Cl to 20·0‰. Cl. In summer the estuary is progressively filled with saline water from the sea; in winter it is flooded by fresh river run-off water from the heavy and concentrated winter rains. The autumn fall in salinity is usually very rapid and constitutes a severe physiological shock for organisms inhabiting the estuary. The physiography and hydrology of the Swan estuary are described. Experiments are reported on the salinity tolerance and behavioural responses to salinity stresses of adult mussels and larval stages. Adult mussels show no ability to osmoregulate (except possibly at very low salinities). They can tolerate environmental chlorinities at least as high as 31‰. Cl and can withstand sudden dilutions from at least 18‰. down to 1‰.. They are capable of survival at 1‰. for many months. Clos...

Seasonal Variations in the Growth Rate, Thyroid Gland Activity and Food Reserves of Brown Trout (Salmo Trutta Linn.)

ABSTRACT Seasonal variations in the growth rate, food reserves and activity of the thyroid gland of hatchery-reared brown trout have been investigated. Two peaks of maximum growth rate were found, in spring and autumn. A marked depression of rate occurred during midsummer and winter. Fat which was laid down along the mesenteries and pyloric caecae was found to be the main food reserve. Glycogen was found in small quantities in the liver and muscle. The composition of the muscle and liver was constant except for an autumnal fall in the female liver glycogen level. The fat reserves reached a peak of 23 % by weight of the gut wall during July then fell to 5 % in autumn. Maturation of the gonads commenced in females in June and in males in July and was completed during October. The protein content of the ovary increased by 16%, and of the testis by 10%.The fat content of the ovary increased by 3 %. A new method is described for the determination of thyroid activity in fish using radioactive iodine. Peak thyroid activity was found to occur in midsummer.

The Library World Volume 46 Issue 2

“BEFORE the leaves of Autumn fall” we were assured by Mr. Churchill that there might be heavy fighting. They have not fallen yet, although with September, beautiful as it often is, we know the Summer is over and our minds must be occupied most immediately with the war. Libraries may seem to some, even librarians, secondary in this maelstrom but, even if they are, that secondariness is really so important that at this month everyone looks to his own work to see in what ways it may be geared up more fully for its own special contribution. Immediate planning concerns such matters as winter service hours, staffing, the growing wear and tear on stocks, the inadequacy of new book supply, the growing shabbiness of our buildings and our continuing inability to carry on the extension work which was so prominent a feature of many libraries. Frankly, in most towns we are giving a book service, not doing the library work, personal and bibliographical, which every librarian desires to give. To do what is within our limits to the best advantage is, then, the immediate problem.

High latitude ozone measurements

AbstractObservations were made at North‐East Land to determine the amount of ozone in the upper atmosphere by measuring the absorption of the ultra‐violet light in the spectrum of the Pole star. A quartz spectrograph was used and the spectra were examined by a photometer. The densities of the spectra for wave length 3,290 and 3,092 A were compared with the equal densities on an image on the plate of a source of light whose intensity varied along the image according to a known law. The constants were determined by carrying out a similar experiment at Oxford at night when the amount of ozone on the previous and following days had been measured by the standard method. Trouble was caused by the fogging of the plates caused by auroral light, but this was corrected for by a statistical method. The mean error of each determination was of the order of 30×10‐3 cms., but the day‐to‐day fluctuation was found to be far greater than this and than the fluctuation observed in lower latitudes. There was no apparent connection between the amount of auroræ and the amount of ozone. The results show that the autumn fall in the amount of ozone, observed at all latitudes is continued through the winter and is followed by a sudden rise in spring.