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761.
A. Araya P.V.V. Prasad P.H. Gowda I. Kisekka A.J. Foster 《Journal of the American Water Resources Association》2019,55(1):24-37
The Agricultural Production Systems sIMulator model validated in a prior study for winter wheat was used to simulate yield, aboveground crop biomass (BM), transpiration (T), and evapotranspiration under four irrigation capacities (ICs) (0, 1.7, 2.5, and 5 mm/day) with two nitrogen (N) application rates (N1, 94 kg N/ha; N2, 160 kg N/ha) to (1) understand the performance of winter wheat under different ICs and (2) develop crop water production function under various ICs and N rates. Evaluation was based on yield, aboveground crop BM, transpiration productivity (TP), crop water productivity (WP), and irrigation WP (IWP). Simulation results showed winter wheat yield increased with increase in N application rate and IC. However, the rate of yield increase gradually reduced with additional irrigation beyond 2.5 mm/day. A 5 mm/day IC required a total of 190 mm irrigation and produced a 5%–16% yield advantage over 2.5 mm/day. This indicates it is possible to reduce groundwater use for wheat by 50% incurring only 5%–16% yield loss relative to 5 mm/day. The TP and IWP for grain were slightly higher under IC of 1.7 mm/day (15.2–16.1 kg/ha/mm and 0.98–1.6 kg/m3) when compared to 5 mm/day (14.7–15.5 kg/ha/mm and 0.6–1.06 kg/m3), respectively. Since TP and IWPs are relatively higher under lower ICs, winter wheat could be a suitable crop under lower ICs in the region. Relationship between yield–T and yield–ET was linear with a slope of 15–16 and 9.5–10 kg/ha/mm, respectively. Editor's note : This paper is part of the featured series on Optimizing Ogallala Aquifer Water Use to Sustain Food Systems. See the February 2019 issue for the introduction and background to the series. 相似文献
762.
763.
Through human history, wealth has been measured in grain, gold, and, now, dollars. Though counterfeiting of coins and notes
goes back a long way, it is only with electronic financial accounting in a global economy tainted by toxic loans and imaginary
funds that there is an urgency to search for a realistic objective way to monitor and regulate what we are doing to our Earth
and ourselves. Various schemes using analysis of utility functions, oil equivalents, entropy, energy, and other units have
been tried and, while helping to understand some basic processes and flows, have always been swamped by the machinations of
financiers and the attention big sums of money attract. Now, the concept of exergy, pioneered in Eastern Europe in the 1950s,
is being researched, developed, and applied, especially in China, driven by the desperation to measure the reality beyond
the twin specters of global financial and environmental crises. A rough inventory of the matter in the biosphere at the coordinate
details of an angstrom and an appreciation of how humans harness and manipulate electromagnetic forces can be enlightening
as to what is and is not sustainable. Without that understanding, any financial estimate and proposed stimulus packages or
IMF reform will be wildly wrong and may even be headed in the wrong direction. 相似文献
764.
Since 1980, liver neoplasms in brown bullhead and polynuclear aromatic hydrocarbons (PAH) in sediment have been researched in a series of studies on the Black River in Lorain, Ohio. In the early 1980s the liver cancer prevalence in fish of age 3 and older was high, ranging from 22% to 39% of the adult population. These high cancer rates corresponded to high levels of PAHs in the sediment resulting from long-term releases by an upstream coking facility (USX). In 1983 this coking plant was closed, and by 1987 the PAH in sediment had declined by about two orders of magnitude. Coincidentally the tumor prevalence in 1987 was only about one-fourth of that in the early 1980s. In 1990, the most contaminated sediments were dredged. Neoplasm surveys in 1992 and 1993 found liver tumor frequencies in mature bullhead were as high as or higher than in the early 1980s. However liver tumor incidence declined in 1994, especially among age 3 fish, where neoplasm incidence was zero. These age 3 fish were the first group sampled that were not present during the 1990 dredging. These data are consistent with a hypothesis that the increase in tumor prevalence in 1992 and 1993 was caused by exposure to buried PAH-contaminated sediments released by the dredging. This research points out the insight provided by long term effects studies. 相似文献
765.
Robert Wood John Handley Sue Kidd 《Journal of Environmental Planning and Management》1999,42(3):341-354
The Mersey Basin Campaign was established in 1985 in the North West of England to address continuing problems of water quality and associated landward dereliction of the River Mersey and its tributaries. The Campaign's premise that water quality should be improved both for its own sake and as a stimulus to regeneration has proved to be well founded and has subsequently been extended to embrace community action to help nurture watercourse improvement and care. The Campaign can now be seen as a model for engaging co-ordinated environmental action through a partnership approach. This paper explores the nature of the Mersey Basin Campaign as an example of the new structures which are being developed in order to help deliver the new environmentalpolicy agenda. It is argued that the Campaign stands as a model for what will become an increasing need to develop focused environmental planning and management at the sub-regional and regional scales. 相似文献
766.
Salt Marsh Diking and Restoration: Biogeochemical Implications of Altered Wetland Hydrology 总被引:3,自引:0,他引:3
John W. Portnoy 《Environmental management》1999,24(1):111-120
Experimental short-term desalination and drainage of salt marsh cores in greenhouse microcosms caused Spartina production to increase after one growing season, reflecting decreased salt stress and sulfide toxicity. However, production
thereafter declined, likely due to pyrite oxidation and acidification in drained treatments and sulfide accumulation in waterlogged
treatments.
A survey of longer-term (decadal) effects of diking on peat composition of Cape Cod, Massachusetts, USA, marshes revealed
acidification, Fe(II) mobilization, and decreased organic content in drained sites. Despite the aerobic decomposition of organic
matter, abundant nutrients remained as sorbed NH4 and mineral-bound PO4. In diked, seasonally waterlogged sites, porewater alkalinity, sulfide, ammonium and orthophosphate were much lower, and
organic solids higher, than in adjacent natural marsh.
Seawater was added to cores from diked marshes to study the effects of tidal restoration. Salination of the drained peat increased
porewater pH, alkalinity, ammonium, orthophosphate, Fe, and Al; copious ammonium N, and Fe(II) for sulfide precipitation favored
Spartina growth. Salination of diked–waterlogged peat increased sulfate reduction and caused 6–8 cm of sediment subsidence. The resulting
increase in porewater sulfides and waterlogging decreased vigor of transplanted Spartina alterniflora. Results indicate that seawater restoration should proceed cautiously to avoid nutrient loading of surface waters in drained
sites or sulfide toxicity in diked–waterlogged marshes. 相似文献
767.
768.
Gary L. Ketcheson Walter F. Megahan John G. King 《Journal of the American Water Resources Association》1999,35(1):83-98
ABSTRACT: Erosion and sedimentation data from research watersheds in the Silver Creek Study Area in central Idaho were used to test the prediction of logging road erosion using the R1-R4 sediment yield model, and sediment delivery using the “BOISED” sediment yield prediction model. Three small watersheds were instrumented and monitored such that erosion from newly constructed roads and sediment delivery to the mouths of the watersheds could be measured for four years following road construction. The errors for annual surface erosion predictions for the two standard road tests ranged from +31.2 t/ha/yr (+15 percent) to -30.3 t/ha/yr (-63 percent) with an average of zero t/ha/yr and a standard deviation of the differences of 18.7 t/ha/yr. The annual prediction errors for the three watershed scale tests had a greater range from -40.8 t/ha/yr (-70 percent) to +65.3 t/ha/yr (+38 percent) with a mean of -1.9 t/ha/yr and a standard deviation of the differences of 25.2 t/ha/yr. Sediment yields predicted by BOISED (watershed scale tests) were consistently greater (average of 2.5 times) than measured sediment yields. Hillslope sediment delivery coefficients in BOISED appear to be overly conservative to account for average site conditions and road locations, and thus over-predict sediment delivery. Mass erosion predictions from BOISED appear to predict volume well (465 tonnes actual versus 710 tonnes predicted, or a 35 percent difference) over 15 to 20 years, however mass wasting is more episodic than the model predicts. 相似文献
769.
A toxic axenic strain of Alexandrium fundyense is shown to be capable of removing dissolved free amino acids (DFAAs) until concentrations are similar (low nM) to those found in natural waters. Uptake is greatest during exponential growth, rather than during C and/or N-stress as
is usual in diatoms and other flagellates. A wide range of amino acids can be taken up, their concentration being decreased
within a few hours to the levels observed prior to DFAA addition. The maximum rate of DFAA-N uptake, during early exponential
phase, was 0.8 pmol-N cell−1 h−1, equivalent to ≃20% of the total N requirement. More typically, the contribution of DFAA-N was only ≃5%. However, these uptake
rates are not sustainable. It is apparent that this organism cannot use amino-N to support significant growth, even though
it can take up DFAAs. This, and the fact that the composition of the internal amino acid pool differed from that externally,
is further evidence that the N-physiology of this genus is abnormal (differences to other dinoflagellates include an abnormally
high concentration of glutamine and arginine, an effective absence of amine X, and release of nitrite during the␣concurrent
assimilation of nitrate and ammonium in␣darkness). There is no evidence that the use of DFAAs enhance toxin content, except
when cells are supplied with very high (unnatural) concentrations of arginine.
Received: 8 May 1989 / Accepted: 14 September 1998 相似文献
770.
Contradictory findings in studies of sex ratio variation in roe deer (Capreolus capreolus) 总被引:3,自引:0,他引:3
A. J. Mark Hewison Reidar Andersen Jean-Michel Gaillard John D. C. Linnell Daniel Delorme 《Behavioral ecology and sociobiology》1999,45(5):339-348
Patterns of sex ratio variation and maternal investment reported in the literature are often inconsistent. This could be
due to intra- and inter-specific variation in social systems, but may also be a result of the a posteriori nature of much
of this type of analysis or the testing of models which are inappropriate. Two recent papers reported directly opposed results
concerning variation in offspring sex ratios in relation to maternal condition in roe deer, interpreting the results as support
for the Trivers and Willard model and for the local resource competition hypothesis, respectively. In this paper, we present
data on offspring sex ratios and early juvenile body weight from two long-term studies of this species to test predictions
arising from these two models concerning sex biases in litter composition and maternal care. First, we observed no consistent
pattern of sex differences in an index of weaning weight or body weight at 1 month old in either population, indicating a
lack of sex bias in maternal care. However, in one population, higher maternal body weight was associated with higher juvenile
body weight of daughters, but not of sons. Secondly, we found a negative, but not statistically significant, relationship
between maternal body weight and litter sex ratio such that heavier females tended to produce more daughters and lighter females
to produce more sons. These results indicate that roe females which have additional investment potential available do not
invest it in sons, as predicted by the Trivers and Willard model. Our results may provide some support that roe deer are subject
to local resource competition acting at the level of the individual mother; however, the fact that particular trends in sex
ratio data can be explained in functional terms provides no indication that they are actually adaptive.
Received: 9 December 1997 / Accepted after revision: 11 November 1998 相似文献