Onset Of Winter Rains Research Articles

Reach specific use of spawning habitat by adult green sturgeon ( Acipenser medirostris ) under different operation schedules at Red Bluff Diversion Dam

Mature green sturgeon, Acipenser medirostris, enter rivers along the western coast of North America in late winter to late spring and migrate upriver to spawning sites. After spawning, they may leave the river or spend the summer and autumn holding in deep pools before departing from the river with the onset of winter rains. Evidence exists that the seasonal Red Bluff Diversion Dam (RBDD) was an obstacle to the upriver migration of green sturgeon in the Sacramento River in Central California. We compared the migratory movements of green sturgeon under three different dam operation schedules, including post-decommissioning, to assess the impact of this management action. The proportion of green sturgeon carrying acoustic transmitters that moved above the RBDD was higher when the gates were closed on June 15, one month later than the historical closure date of May 15, and increased again after the dam was decommissioned. The application of statistical analyses (generalized linear and additive mixed models) to the detection records of green sturgeon highlighted an improvement in connectivity after dam decommissioning. The data also indicate that interannual variation in river condition is an important driver of sturgeon presence on the spawning grounds.

Downslope Windstorms of San Diego County. Part I: A Case Study

Abstract The “Santa Ana” wind is an offshore flow that affects Southern California periodically during the winter half of the year, typically between September and May. The winds can be locally gusty, particularly in the complex terrain of San Diego County, where the winds have characteristics of downslope windstorms. These winds can cause and/or rapidly spread wildfires, the threat of which is particularly acute during the autumn season before the onset of winter rains. San Diego’s largest fires, including the Cedar fire of 2003 and Witch Creek fire of 2007, occurred during Santa Ana wind events. A case study of downslope flow during a moderately intense Santa Ana event during mid-February 2013 is presented. Motivated by the need to forecast winds impinging on electrical lines, the authors make use of an exceptionally dense network of near-surface observations in San Diego County to calibrate and verify simulations made utilizing the Advanced Research version of the Weather Research and Forecasting (WRF) Model, which in turn is employed to augment the observations. Results demonstrate that this particular Santa Ana episode consists of two pulses separated by a protracted lull. During the first pulse, the downslope flow is characterized by a prominent hydraulic jumplike feature, while during the second one the flow possesses a clear temporal progression of winds downslope. WRF has skill in capturing the evolution and magnitude of the event at most locations, although most model configurations overpredict the observed sustained wind and the forecast bias is itself biased.

How soil moisture mediates the influence of transpiration on streamflow at hourly to interannual scales in a forested catchment

AbstractThe water balance equation dictates that streamflow may be reduced by transpiration. Yet temporal disequilibrium weakens the relationship between transpiration and streamflow in many cases where inputs and outputs are unbalanced. We address two critical knowledge barriers in ecohydrology with respect to time, scale dependence and lags. Study objectives were to correlate components of the water balance equation at hourly to annual scales, quantify time lags, and simplify critical components of the water budget during wet and dry conditions. We tested interrelationships among precipitation, vapour pressure deficit, transpiration, soil moisture, and streamflow within the confines of a 60‐hectare forested watershed in the western Cascades of Oregon. The Pacific Northwest is an ideal location to compare wet and dry seasons because of its Mediterranean climate. Soil moisture explained more than 80% of the variation in streamflow at all temporal scales investigated. Streamflow was most strongly coupled to soil moisture in the wet season because of gravitational drainage patterns; strong coupling of transpiration to vapour pressure deficit was dominant in the dry season and driven by low humidity. We observed progressively longer hourly time lags between soil moisture and streamflow in the dry season, which relates to an increasing soil moisture deficit that took an average of 48 days to refill after the onset of winter rains. We propose that transpiration drives seasonal patterns in soil moisture that relate to patterns in streamflow only after long time lags. In other words, soil moisture mediates the influence of transpiration on streamflow. Copyright © 2011 John Wiley & Sons, Ltd.

Evocatio Deorum and the Date of Mark

The date of Gospel of Mark is generally set a few years either side of destruction of second Temple on 9th of Av, 70 C.E.1 The grounds for this dating vary. Earlier commentators tended to place considerable stock in patristic testimony, which claimed that author of second Gospel was a companion of Peter, which in turn implied a date for Gospel either during Peter's lifetime or shortly after his death-in any event, before 70 C.E.2 More recent scholarship has insisted on internal evidence of date, with attention mainly falling on Mark 13. There is no strong tendency apparent: although perhaps majority hold that Mark looks back on destruction of second Temple,3 a few recent commentators, usually combining patristic testimony with internal evidence, hold that Mark ought to be placed shortly before 70 C.E.4 The pertinence and reliability of patristic testimony are much in question, but in any event do take us back much earlier than Clement of Alexandria and Irenaeus at end of second century.5 The best place to begin is with internal references. Several texts are routinely cited that point to a relatively early dating, but none of these permits us to narrow down date to one side of 70 C.E. or other. Mark 9:1 and 13:30 predict that some of Jesus' contemporaries will live to see parousia, predictions that, given a mean life expectancy of forty years, would point to a date too much later than 70 C.E. Such indications of date are very strong, however, since Matthew, usually dated in 80s, has taken over two Markan predictions almost unchanged. If Matthew was able to tolerate failed or obviously failing predictions, then so might Mark.6 Likewise, details such as explicit naming of Alexander and Rufus as sons of Simon of Gyrene (15:21) or Mark's unelaborated references to the high (14:53) and Pilate (15:2), in contrast to Matthew and Luke, who identify high priest as Caiaphas (Matt 26:3, 57; Luke 3:2) and Pilate as the governor (Matt 27:11; Luke 3:1), presuppose an audience that does need explanations for these persons.7 Or again, Mark's presentation of Jesus' opponents, which, unlike Matthew's account, distinguishes between scribes and Pharisees (Mark 2:15) and, unlike Matthew (3:7; 16:1), restricts Sadducees to environs of Jerusalem, reflects a greater awareness of religious topography of Judea prior to first revolt.8 These data, however, point only to a relatively early date for Gospel and do permit any greater precision. Thus, it seems unlikely that Mark 13:14 was specifically formulated with Titus's desecration of temple area in view, since it so poorly fits details.17 The disadvantages of this solution mount, however, when one considers Mark s inclusion of wish that events leading to flight not occur during (13:18). This fits well Caligula crisis, which was escalating during summer and fall of 40, just before onset of winter rains, but it hardly fits events of August 70 C.E.22 Thus, once again it would be necessary to posit a negligent editor, who missed fact that desecration of sanctuary by Titus and its subsequent destruction occurred before winter of 70 C.E. This is certainly possible-the redactors of Gospels elsewhere are guilty of clumsy editing23-but it is an entirely happy solution. Since both Matthew and Luke were quite capable of alleviating tensions created by w. 14 and 18 when read in a post-70 situation, it is odd that a post-70 Mark could or did not.24 Without abandoning advantages of positing a pre-Markan apocalypse to account for anachronistic reference to flight in winter,25 several authors have alleviated tensions created by w. 14 and 18 by arguing that Mark was composed prior to 70 C.E. Accordingly, for author of Mark, expectation of a desecration of sanctuary, either by installation of a pagan altar similar to that used by Antiochus IV Epiphanes or by a cult image such as that planned by Caligula, was yet unrealized, but under circumstances of an impending threat by Romans, scarcely an unrealistic apprehension. …

Ecophysiology of ectomycorrhizal fungi associated with Pinus spp. in low rainfall areas of Western Australia

As a potential means of monitoring functional properties of plantations of Pinus pinaster and Pinus radiata established as part of land rehabilitation in the wheatbelt of Western Australia, we examined aspects of the ecophysiology of ectomycorrhizal fungi associated with tree roots. A single species of ectomycorrhizal fungi, Rhizopogon roseolus, dominated the mycorrhizal flora. Sporocarps of Rhizopogon roseolus appeared with the onset of winter rains in May, increased in number and total biomass to peak in September, and decreased to negligible levels at the beginning of the summer drought in December. A greater number of sporocarps, and consequently a greater biomass of sporocarp tissue, was associated with roots of P. radiata than P. pinaster. A similar seasonal pattern of mycorrhizal root infection was determined by counts of individual ectomycorrhizal root tips from bimonthly collection of soil core samples. At the low rainfall (380 mm annually) site, greater numbers of live root tips were more strongly correlated with soil moisture than organic matter content of soil. In contrast, in wetter areas closer to Perth (800 mm annually), highest numbers of active root tips and greatest amounts of organic matter were both within 0–10 cm depths. Results suggest an overriding importance of soil moisture rather than nutrient status of the soil as the key determinant of spatial and temporal distribution of the fungus. Results from a range of assays determining enzyme activity of soil (protease, phosphomonoesterase, cellulase, L-asparaginase, L-glutaminase and β-glucosidase) surrounding mycorrhizal roots indicated seasonal patterns to be similar to those described for reproductive activity of mycorrhizal fungi. Factors responsible for patterns of seasonal activity and distribution of ectomycorrhizal roots are discussed in terms of managing systems in order to maximise tree growth and form while effectively restoring soil water balance.

Preface

Quantification of nitrate (NO-3) leaching is fundamental to understanding the efficiency with which plants use soil-derived nitrogen (N). A deep sand located in the northern wheatbelt of Western Australia was maintained under a lupin (Lupinus angustifolius)-wheat (Triticum aestivum) and a subterranean clover (Trifolium subterraneum) based annual pasture-wheat rotation from 1994to 1996. Fluxes of water and NO-3 through, and beyond, the root-zone were examined. Drainage was calculated on a daily basis from measurements of rainfall, evapotranspiration, and the change in soil water content to a depth of 1·5 m. Evapotranspiration was estimated from Bowen ratio measurements,and soil water content was determined by time domain reflectrometry. Soil was sampled in layers to1·5 m at the onset of winter rains and analysed for NO-3 . Ceramic suction cups were installed at 0·25, 0·4, 0·6, 0·8, 1·0, 1·2, and 1·4 m to sample soil solution from June to mid August. The NO-3 leached from each layer was computed by multiplying the daily drainage through each layer by the estimated concentration of NO-3 within the layer. The estimated concentration of NO-3 in a layer was calculated by taking into account NO-3 either entering that layer through mineralisation and leachingor leaving the layer through plant uptake. Mineral N was added to the surface 0·2 m in accordance with measured rates of net N mineralisation, and daily N uptake was calculated from the measured above-ground plant N derived from soil N. Root sampling was undertaken to determine root lengthdensity under pastures, lupin, and wheat. Cumulative drainage below 1·5 m was similar under wheat and lupin, and accounted for 214 mmfrom 11 May to 15 August 1995 and 114 mm from 2 July to 15 September 1996. The cumulative evapotranspiration (Ea) over these periods was 169 mm from a wheat crop in 1995, and 178 mm from a lupin crop in 1996. The amount of NO-3 in soil at the start of the growing season was afiected by previous crop, with a lower range following wheat (31-68 kg N/ha) than following legumes (40-106 kgN/ha). These large quantities of NO-3 in the soil at the break of the season contributed substantially to NO-3 leaching. Leaching of NO-3 below 1·5 m in wheat crops accounted for 40-59 kg N/ha where these followed either lupin or pasture. In contrast, less NO-3 was found to leach below 1·5 m in pastures (17-28 kg N/ha). Greater N uptake by capeweed (Arctotheca calendula L.) than by either wheat or lupin was the main reason for the lower amount of NO-3 leached in pastures.

Nitrogen and water flows under pasture - wheat and lupin - wheat rotations in deep sands in Western Australia. 2. Drainage and nitrate leaching

Quantification of nitrate (NO-3) leaching is fundamental to understanding the efficiency with which plants use soil-derived nitrogen (N). A deep sand located in the northern wheatbelt of Western Australia was maintained under a lupin (Lupinus angustifolius)-wheat (Triticum aestivum) and a subterranean clover (Trifolium subterraneum) based annual pasture-wheat rotation from 1994to 1996. Fluxes of water and NO-3 through, and beyond, the root-zone were examined. Drainage was calculated on a daily basis from measurements of rainfall, evapotranspiration, and the change in soil water content to a depth of 1·5 m. Evapotranspiration was estimated from Bowen ratio measurements,and soil water content was determined by time domain reflectrometry. Soil was sampled in layers to1·5 m at the onset of winter rains and analysed for NO-3 . Ceramic suction cups were installed at 0·25, 0·4, 0·6, 0·8, 1·0, 1·2, and 1·4 m to sample soil solution from June to mid August. The NO-3 leached from each layer was computed by multiplying the daily drainage through each layer by the estimated concentration of NO-3 within the layer. The estimated concentration of NO-3 in a layer was calculated by taking into account NO-3 either entering that layer through mineralisation and leachingor leaving the layer through plant uptake. Mineral N was added to the surface 0·2 m in accordance with measured rates of net N mineralisation, and daily N uptake was calculated from the measured above-ground plant N derived from soil N. Root sampling was undertaken to determine root lengthdensity under pastures, lupin, and wheat. Cumulative drainage below 1·5 m was similar under wheat and lupin, and accounted for 214 mmfrom 11 May to 15 August 1995 and 114 mm from 2 July to 15 September 1996. The cumulative evapotranspiration (Ea) over these periods was 169 mm from a wheat crop in 1995, and 178 mm from a lupin crop in 1996. The amount of NO-3 in soil at the start of the growing season was afiected by previous crop, with a lower range following wheat (31-68 kg N/ha) than following legumes (40-106 kgN/ha). These large quantities of NO-3 in the soil at the break of the season contributed substantially to NO-3 leaching. Leaching of NO-3 below 1·5 m in wheat crops accounted for 40-59 kg N/ha where these followed either lupin or pasture. In contrast, less NO-3 was found to leach below 1·5 m in pastures (17-28 kg N/ha). Greater N uptake by capeweed (Arctotheca calendula L.) than by either wheat or lupin was the main reason for the lower amount of NO-3 leached in pastures.

Factors Limiting the Recruitment of Eucalyptus salmonophloia in Remnant Woodlands .II. Postdispersal Seed Predation and Soil Seed Reserves

This study examined post-dispersal seed predation and soil seed reserves in four remnant populations of E. salmonophloia in the central wheatbelt of Western Australia to determine the effect of these factors on recruitment. Diurnal observations of post-dispersal seed predation at regular intervals of 2 months were undertaken over a 12 month period using artificial baits. Four species of ants were seen removing seeds from artificial baits regularly. Surveys of soil seed reserves revealed that E. salmonophloia does not form a soil seed bank despite a continual seed rain from canopy seed reserves. These observations suggest that ants probably destroy a large proportion of E. salmonophloia seed following dispersal. Burial of E. salmonophloia seeds in the soil in autumn, winter, spring and summer suggest that any seeds which do escape predation are unlikely to persist in the soil for much longer than 12 months and probably germinate with the onset of winter rains. Both the depredation of seeds by ants and the short term viability of seed in the soil contribute to the inability of E. salmonophloia to form a soil seed reserve.

The effect of rain in the dry-season on the formation of vesicular-arbuscular mycorrhizas in the growing season of annual clover-based pastures.

In a mediterranean climate with hot dry summers and cool winter growing seasons, rain in summer may initiate seed germination and seedling emergence in annual clover-based pastures. If soil moisture becomes limiting and the seedlings die before the onset of winter rains then a'false break'has occurred. The effect of false breaks on the formation of mycorrhizas in subterranean clover (Trifolium subterraneum L.) in the winter growing season was investigated. Undisturbed cores were collected in the summer from two annual clover-based pastures in Western Australia. The cores were treated with one or two false breaks, or left dry. For each false break, 3 centimetres of water were applied to the surface of the core over a 3 day period and then the cores were let dry in glasshouse conditions. The second false break and the growing season were initiated after the complete death of plants that had emerged in the previous cycle. The growing season was simulated by watering all cores to field capacity and planting to a uniform stand of subterranean clover. Mycorrhizal colonization in the growing season was decreased by false breaks with little difference between One and two false breaks. In one soil, the percentage of the root length containing arbuscules (AC%) at 14 d after planting in the growing season was decreased from 52 to 33% by false breaks and at 42 d after planting from 16 to 46%. In the other soil, the AC% at 28 d after planting in the growing season was decreased from 72 to 55% by false breaks. Assessment of the morphology of the mycorrhizas indicated that colonization by fine endophytes was decreased but colonization by Acaulospora spp., Glomus spp. and Scutellospora and Gigaspora spp. was not decreased by false breaks. Shoot phosphorus concentration at 14 d after planting and shoot dry mass at 42 d after planting were decreased by false breaks in only one soil.

Improving feeding systems for sheep in a Mediterranean rain-fed cereals/livestock area of Morocco.

In rain-fed cereal-producing areas of Morocco, stubble and straw from barley and wheat and forage grazed from fallow lands are important feeds for sheep. Supplementation to maintain BW of ewes pregnant while grazing stubble, methods to improve utilization of straw, annual forage legumes to complement grazing of fallow land, and by-product feeds in diets for weaned lambs have been tested in collaborative research trials. Pregnant ewes grazing cereal stubble for 10 to 12 wk at a modest stocking rate and unsupplemented, or at a heavier stocking rate and supplemented after 5 wk, gained about 3 kg; most of the gain occurred in wk 1 to 4 due to intake of residual scattered grain. Following the stubble-grazing period (coincident with late gestation), straw plus an energy supplement alone resulted in low lamb birth weight and survivability. Urea treatment increased N content of straw and holds potential. After the onset of winter rains, self-reseeding annual legume (Medicago spp.) pastures allowed lactating Timahdit ewes to gain 4 kg during 90 d postpartum. Their suckling lambs gained 260 g/d, thus doubling the weight of lamb weaned per ewe compared with those grazing unimproved fallow. Confined growing lambs fed diets with 40% sugarbeet pulp or 20% carob meal gained more than 200 g/d, reducing the time needed to reach market weight. These results demonstrate that marked improvements in performance and efficiency of sheep in Mediterranean rain-fed cereal/livestock systems are possible using locally available resources.

Evidence for the retention of genetic variation in Erodium seed dormancy by variable rainfall.

The periodic occurrence of summer/early autumn precipitation in the California annual grassland can result in the formation of early and late emerging cohorts of Erodium botrys and E. brachycarpum. The occurrence of early rainfall and the timing of such rainfall are highly variable from year to year. A series of field watering experiments in 1980-81 were used to simulate early emergence conditions that would result from significant rainfall (1 cm) occurring in mid-July, late August, and mid-September. Net reproduction was used to estimate fitness differentials between Erodium cohorts emerging in response to a watering treatment (early emerging cohorts) and Erodium cohorts emerging with the onset of winter rains in mid-October (late emerging cohorts). Survival was lower and gross reproduction was higher among early emerging cohorts than late emerging cohorts. For both species, net reproduction of the early cohort was lower than that of the late cohort under the July watering treatment and higher than that of the late cohort under the August watering treatment.Early cohorts, formed in response to rainfall in mid-September, 1982, were also compared demographically to later cohorts emerging in October. Compared to late cohorts, net reproduction, gross reproduction and survival were higher for the early cohorts.Common garden experiments indicate that differences in the duration of seed dormancy between the progenies of early and late emerging plants reflect a significant genetic component. Progency produced by early cohorts of E. brachycarpum from all three watering treatments possessed more extended seed dormancy than progeny of late cohorts. In E. botrys, progeny from early cohorts emerging in response to the July watering treatment were also more dormant than late progeny. In contrast, early cohorts of E. botrys emerging in response to the September watering treatment produced seed less dormant than seed produced by late cohorts. When combined with demographic data, indicating that fitness differentials between early and late cohorts varied with changes in the date of early emergence, genetic results suggest that year to year variation in early rainfall may act to retain genetic variation in the duration of seed dormancy.

Influence of added nutrient on the seasonal variation of algal growth potential of Mt Bold reservoir, South Australia

Bioassay experiments with the natural phytoplankton assemblage showed that the major nutrient input to Mt Bold reservoir, South Australia, occurred with the onset of winter rains. Growth potential within the euphotic zone generally increased from June to November but was undetectable from December to March when the autumn overturn circulated nutrient-rich water from the hypolimnion to cause an increase in growth. Subsequently, the growth potential fell and did not rise until the onset of winter rains. Routine enrichment experiments with phosphorus, nitrogen and Na-EDTA substantially increased the growth potential above the control during periods of suspected nutrient depletion. During periods of nutrient depletion, the influence of 10 single and 45 dual nutrient additions showed that only the combined addition of nitrogen and phosphorus caused a significant increase in growth potential. To investigate further the influence of nitrogen and phosphorus on algal growth, factorial nutrient-enrichment experiments using five levels of both nitrogen and phosphorus and three of Na-EDTA at two temperatures (11 and 20�C) were conducted. The work is discussed in relation to the routine nutrient analyses done by the Engineering and Water Supply Department of South Australia.

Review Of The Pakistan Economy (Food And Agriculture)

During the period under review, from October 1960 to March 1961, prices of wheat at Lyallpur (West Pakistan) recorded a small net increase while prices of rice at Dacca (East Pakistan) registered an appreciable net decline. (See Table below) Wheat prices at Lyallpur showed a persistent tendency to rise owing partly to drought conditions and partly to withholding of stocks by traders in expectation of shortages of foodgrains following enlarged shipments to the cyclone affected areas of East Pakistan. Prices touched a peak of Rs. 17/12/- 18/14/- in the middle of January from Rs. 15/8/- 17/- per maund at the close of September 1960. The continued release of government stocks at a fixed rate of Rs. 16/- per maund through 250 centres was a major factor for the reversal in the rising trend in prices. The onset of winter rains also had a favourable impact on prices. As a result, there was a marked decline in prices which closed finally at Rs. 16/- to 17/- at the end of March 1961. Meanwhile, the final estimate of wheat crop for 1959-60 placed output at about 0.6 per cent higher at 3,876,000 tons compared with the preceding year, the area under wheat cultivation having risen by 1.6 per cent to 12,193,000 acres. However, the first forecast of wheat crop for 1960-61 places the cultivated area at 10,428,000 acres or a decline of 16.0 per cent as against the first forecast for 1959-60.