Salinity and geomorphology drive long‐term changes to local and regional fish assemblage attributes in the lower Pecos River,Texas

River systems throughout arid regions worldwide have been heavily impacted by human activities, resulting in long‐term ecological consequences. The lower Pecos River in the Trans‐Pecos region of Texas is no exception, having undergone anthropogenic changes that include decreased flow, elevated salinity, species loss and species invasion. We compared historical and contemporary fish assemblage attributes from the Pecos River at local (site‐specific) and regional (Trans‐Pecos region) scales across a 24‐year time period. Fish assemblage data were collected in October 1987 and 2011, by seining at 15 sites spanning 430 km of the river in Texas. Additionally, we examined contemporary environmental conditions to determine species–environment relationships. We found that fish assemblages were significantly different between time periods, likely due to increased salinisation in the upper half of the study region. Decreased species richness, species replacement and increases in euryhaline species were documented in the upstream sites. Freshwater springs lower the salinity and maintain flows in the downstream reach, allowing for maintenance of the native fish fauna. Careful management of regional aquifers, irrigation practices and petroleum waste water will be necessary for protecting biodiversity and environmental flows in the lower Pecos River.     

缓释复方免疫增强剂有效药物释放量及安全性试验

将100只14日龄健康肉杂仔鸡随机分成A、B、C、D、E 5个试验组,每组20只鸡,A、B、C、D 4组为试验组,E组为对照组。A、B、C 3组试验鸡每只分别投服批号为0308、0312、0402的缓释复方免疫增强剂1粒,进行有效药物释放量测定试验,试验结果表明,药物投服后日均磨损量20d前为6.2~6.7 mg,30 d前为6.0~6.3 mg,日均药物有效释放量为2.40~2.52 mg,经方差分析,批间差异不显著(P0.05),均在有效剂量之间,药物的有效释放期均在30 d以上。D组试验鸡每只投服缓释复方免疫增强剂3粒,进行有效药物安全性试验,试验结果表明,仔鸡投服后食、饮欲正常,精神状态良好,与对照组鸡相比未发现任何不良反应,从而说明该缓释制剂在鸡体内是安全有效的。     

Examination of thermal and acid hydrolysis procedures in characterization of soil organic matter

Abstract

Differential thermogravimetry (DTG), differential scanning calorimetry (DSC), and stepwise thermogravimetry (STG), together with two acid hydrolysis methods (hydrolysis with hydrochloric acid in a single step, and hydrolysis with sulfuric acid in two steps), were evaluated to determine the quality of four plant materials (Medicago sativa, Eucalyptus globulus, Quercus ilex, and Pinus halepensis) before and after mixing with a red earth. These quality indices were then compared with the same materials in the field, whether their decomposition could be predicted. All the thermal methods gave poor results. In both DTG and DSC, the presence of the mineral matrix gave rise to strong distortions in the spectra. Since the spectrum of any mixture is not simply the sum of the spectra of the two components (organic matter + mineral matter), these distortions could not be corrected by simply subtracting the spectrum of the red earth alone. STG trials also gave poor results, because the presence of the mineral matrix greatly increased the quality indices, and reduced the ability of the method to distinguish between organic matter qualities. In view of our results, the usefulness of thermal methods in the characterization of soil organic matter would seem to be restricted to certain organic horizons (L, F, and perhaps H). In contrast, methods based on acid hydrolysis were comparatively more satisfactory. Their resolution (ability to distinguish organic matter qualities) was much higher than that of thermal methods. However, they were able to distinguish carbon more accurately than nitrogen. The sulfuric acid method, unlike the hydrochloric acid method, was affected by the presence of a mineral matrix. While both methods could be improved, in their present form they seem to operate as good predictors of carbon and nitrogen mineralization.     

线损分析在轨道交通企业能源管理中的应用

轨道交通的不断发展需要更多的电能,但当今能源日趋紧张,对节能降损必须予以足够的重视.所以轨道交通企业须在供电用电管理中加强线损的分析和预测,从供电设计、规划、管理等方面实施降低线损管理,使企业节能降耗并有效提高经济效益.     

不同灌排模式稻田排水中氮磷流失规律

为了研究不同灌排模式稻田排水中氯磷流失规律,以集成合理的节水灌溉与控制排水技术,在江苏高邮开展田间试验.试验区排水斗沟出口处设水位调控闸门,在水稻不同生育阶段对排水沟水位及田间水分进行控制,形成新型的控制灌排模式.与常规灌排模式进行对比,两年田间试验成果表明,控制灌排模式较常规灌排模式节水16.7%,增产7.1%,排水总量减少54%,水稻全生育期稻田排水中NH4+;-N、NO3-N与TP流失总量分别减少38.07%、82.29%和52.15%,节水减排和降污效果显著.采用控制灌排模式,通过实施灌水调控和排水管理.控制了氮磷流失关键时期的排水量.高效利用了水分和养分,取得了节水高产、减排控污的效果.     

坡度和降雨强度对坡耕地入渗的影响

利用人工模拟降雨对黑龙江西部半干旱区坡耕地不同坡度和不同降雨强度下的土壤水分入渗规律进行了试验研究,采用产流历时和稳定入渗速率二项指标进行分析,发现随着地面坡度的增大,产流历时提前,稳定入渗速率逐渐减小,坡面产流历时与坡度呈对数函数关系,土壤稳渗速率与坡度呈幂函数关系;随着降雨强度的增大,产流历时提前,稳定入渗速率逐渐增大;坡面产流历时与降雨强度呈指数函数关系,土壤稳定入渗速率与降雨强度也呈指数关系。     

黑龙江省半干旱区防护林内主要气象因子观测初报

对齐齐哈尔(沙壤土区)、杜蒙(风沙土区)、青冈(黑土区)等3个代表黑龙江省半干旱区典型地点防护林区内7、8、9月主要气象因子(气温、气湿、风速、降雨量等)及土壤入渗率情况进行了定期观测,结果表明:3个月份平均气温杜蒙>齐齐哈尔>青冈,气湿为青冈>齐齐哈尔>杜蒙,风速为杜蒙>齐齐哈尔>青冈,土壤入渗率为杜蒙>齐齐哈尔>青冈,揭示了黑龙江省半干旱区防护林内不同土壤类型之间主要气象因子的变化特征及规律,为半干旱区防护林功能评价提供了重要依据。     

Management options to decrease phosphorus and sediment losses from irrigated cropland grazed by cattle and sheep

In southern New Zealand, grazing of forage crops is common practice to satisfy feed requirements of animals in winter when pasture growth is limited. This practice has been shown to cause soil physical damage and increased loss of surface water contaminants sediment and phosphorus (P) to water bodies. Strategies to mitigate the loss of sediment and P were trialled on a Pallic soil type (Aeric Fragiaquept) in the North Otago Rolling Downlands of New Zealand. All sites were irrigated and measurements were made of losses in overland and sub‐surface flow from intensive cattle or sheep grazed, winter forage crops, and sheep grazed pasture. Two mitigations (restricted grazing of crop to three hours and the application of aluminium sulphate) were assessed for their potential to decrease contaminant loss from cropland. Volumes of surface runoff and loss of total P, filterable reactive P and sediment showed significant differences (P < 0.05) between the control treatments (i.e. no mitigation) with cattle crop (88 mm surface runoff) > sheep crop (67 mm) > sheep pasture (33 mm). The contribution of irrigation water to overland flow water, as a result of saturation‐excess conditions, varied between treatments with more loss under cattle crop (20% of total) compared with sheep crop (15%) and sheep pasture (11%). These differences are probably an effect of soil physical condition and highlight the importance of accurate irrigation scheduling to keep soil moisture below field capacity. Restricted winter grazing and alum application after grazing significantly (P < 0.05) decreased P losses in surface runoff under cattle (from 1.4 to 0.9 kg P/ha) and sheep (from 1.0 to 0.7 kg/P/ha) grazed crop plots by about 30%. In cattle grazed plots, restricted grazing also decreased suspended sediments (SS) by 60%. The use of restricted grazing is suggested as a means of decreasing P and SS loss from grazed winter forage crops. The use of alum shows some promise for decreasing P losses, but requires further work to determine its long‐term effectiveness and use in other soils and management regimes.     

An advisory model for control of Puccinia recondita in winter wheat

Epidemics ofPuccinia recondita and resulting yield loss of winter wheat were studied in field experiments over three seasons in the Netherlands. Results are reported and used to construct an advisory model for control of brown rust, based on rust monitoring. If the fraction of leaves with rust (I) at a certain development stage is determined, the average number of rust sori per leaf (M) was estimated by: M=EXP(1.84+1.39ln(ln[1/(1-I)]). The final number of sori per leaf (Mf) at early dough was forecast by an exponential growth: Mf=M·EXP(RGR·t). The relative growth rate (RGR) averaged 0.163/day and the forecasting period, t, until early dough, was derived from published data. The forecast number of sori-days per leaf (S, AUDPC-value) was then obtained by: S=(Mf-M)/RGR. Yield loss (kg/ha) by brown rust was 1.15 times the number of sori-days per leaf at low rust intensities. The efficacy of the fungicides used was 85%. The forecast avoidable yield loss (L, kg/ha) was calculated by: L=0.85 (1.15 S). Economic thresholds for brown rust control at different development stages are given for Dutch wheat fields at a cost level of 270 kg/ha for one fungicide application.     

福建省葡萄病毒病的调查和研究

１９９０～１９９２年作者对福建省葡萄产区进行了抽样调查，发现该省约３１％的果园有葡萄扇叶病（ＧＦＬＶ）和葡萄卷叶病（ＧＬＲＶ）。在调查的１１３００株葡萄中（６０２亩），ＧＦＬＤ株发病率为１３．２７％，造成葡萄减产２７．２％；ＧＬＲＶ株发病率为７．３％，减产２１．５％。病株表现为不同程度的种性退化，生长赢弱、停滞，果实品质下降，果粒成熟不齐。