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1.
米槠人工林土壤微生物群落组成对凋落物输入的响应 总被引:1,自引:0,他引:1
全球气候变化显著影响森林凋落物数量,进而会对土壤微生物群落造成影响。本研究以亚热带米槠人工林为研究对象,探究不同凋落物量输入处理(凋落物去除、凋落物加倍、对照)下,森林土壤微生物群落组成的变化。结果表明:与去除凋落物相比,凋落物加倍后0~10 cm土壤铵态氮(NH4^+-N)、硝态氮(NO3^--N)、全氮(TN)、有效磷(AP)含量分别显著增加了30.30%、49.66%、12.77%和13.90%。与对照相比,凋落物加倍与去除处理土壤微生物生物量碳(MBC)和氮(MBN)含量分别显著增加和下降(P<0.05),但凋落物加倍与去除处理间无显著差异。凋落物加倍处理下土壤丛枝菌根真菌(AMF)、革兰氏阳性菌[G(+)]、革兰氏阴性菌[G(-)]、放线菌(ACT)、真菌(F)丰度和总磷脂脂肪酸(TPLFA)含量分别比去除凋落物处理的土壤高68.35%、63.35%、82.65%、69.02%、40.56%和65.85%,而土壤革兰氏阳性菌与阴性菌比值、真菌与细菌比值则分别降低11.64%和26.67%。冗余度分析表明,铵态氮是影响该人工林土壤微生物群落组成的最主要环境因子。可见凋落物输入量变化改变了土壤养分有效性,进而显著影响了土壤微生物群落组成,这对进一步深入探究全球气候变化对亚热带森林土壤养分循环的影响具有重要意义。 相似文献
2.
Contrast‐Enhanced Ultrasound Examination for the Assessment of Renal Perfusion in Cats with Chronic Kidney Disease 下载免费PDF全文
E. Stock D. Paepe S. Daminet E. Vandermeulen L. Duchateau K. Vanderperren 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2018,32(1):260-266
Background
Contrast‐enhanced ultrasound examination (CEUS) is a functional imaging technique allowing noninvasive assessment of tissue perfusion. Studies in humans show that the technique holds great potential to be used in the diagnosis of chronic kidney disease (CKD). However, data in veterinary medicine are currently lacking.Objectives
To evaluate renal perfusion using CEUS in cats with CKD.Animals
Fourteen client‐owned cats with CKD and 43 healthy control cats.Methods
Prospective case‐controlled clinical trial using CEUS to evaluate renal perfusion in cats with CKD compared to healthy control cats. Time‐intensity curves were created, and perfusion parameters were calculated using off‐line software. A linear mixed model was used to examine differences between perfusion parameters of cats with CKD and healthy cats.Results
In cats with CKD, longer time to peak and shorter mean transit times were observed for the renal cortex. In contrast, a shorter time to peak and rise time were seen for the renal medulla. The findings for the renal cortex indicate decreased blood velocity and shorter total duration of enhancement, likely caused by increased vascular resistance in CKD. Increased blood velocity in the renal medulla has not been described before and may be because of a different response to regulatory factors in cortex and medulla.Conclusions and Clinical Importance
Contrast‐enhanced ultrasound examination was capable of detecting perfusion changes in cats with CKD. Further research is warranted to assess the diagnostic capabilities of CEUS in early stage of the disease process. 相似文献3.
为搞清湿地土壤驱动N2O排放的关键氮源类型,有效减少湿地N2O的排放,本文通过室内控制温湿度,用气相色谱法分析不同外源氮素对湿地N2O排放的影响。结果表明:外加氮源组总是高于对照组N2O排放量(4.4 mg·m-3)。在设定的剂量范围内,单独添加尿素或尿素与硝酸铵1∶1配合时N2O排放量呈现先增后减的单峰分布趋势,峰值分别为10.6 mg·m-3和229.0 mg·m-3;单独添加硝酸铵时N2O排放量(32.6~111.0 mg·m-3)随着氮素添加量增加呈现持续上升趋势。单独添加尿素或硝酸铵、尿素与硝酸铵1∶1配合均促进N2O的排放,但硝酸铵尿素混合添加对N2O排放量的贡献单独添加硝酸铵单独添加尿素。这为预测内蒙古高原区农牧交错带湿地氮素输入可能带来的温室效应和有效减排提供科学依据。 相似文献
4.
NO emissions from soils and ecosystems are of outstanding importance for atmospheric chemistry. Here we review the current knowledge on processes involved in the formation and consumption of NO in soils, the importance of NO for the physiological functioning of different organisms, and for inter- and intra-species signaling and competition, e.g. in the rooting zone between microbes and plants. We also show that prokaryotes and eukaryotes are able to produce NO by multiple pathways and that unspecific enzymo-oxidative mechanisms of NO production are likely to occur in soils. Nitric oxide production in soils is not only linked to NO production by nitrifying and denitrifying microorganisms, but also linked to extracellular enzymes from a wide range of microorganisms.Further investigations are needed to clarify molecular mechanisms of NO production and consumption, its controlling factors, and the significance of NO as a regulator for microbial, animal and plant processes. Such process understanding is required to elucidate the importance of soils as sources (and sinks) for atmospheric NO. 相似文献
5.
农村金融深化促进了农村产业融合发展吗?——基于区域差异视角的实证分析 总被引:1,自引:0,他引:1
在当前全社会高度重视金融服务乡村振兴的背景下,厘清农村金融深化对农村产业融合发展的影响至关重要。基于金融深化理论,利用2008—2017年中国省际面板数据,在测算农村产业融合发展水平和农村金融深化程度的基础上,采用FGLS方法和SYS-GMM方法,系统考察了农村金融深化对中国农村产业融合发展的影响及其区域差异。结果表明,农村金融深化程度和农村产业融合发展水平由2008年的1.029 5和1.039 3上升到2017年的2.717 4和2.604 8,年均增长率分别为11.39%和10.75%。农村金融深化显著促进了中国农村产业融合发展水平的提升,且这种影响存在明显的区域差异,相比于中西部地区,农村金融深化对农村产业融合发展的提升作用在东部地区更加显著。运用面板门槛模型检验发现,地区之间农村金融深化程度、农村人力资本水平和交通基础设施水平的不同,是造成农村金融深化对农村产业融合发展的影响存在区域差异的重要原因。因此,提出不断增加农村产业融合发展的金融供给,因地制宜实施农村产业融合发展的促进政策等建议。 相似文献
6.
为了研究磷酸铵镁堆肥产品的氮磷养分释放特性及其肥效,分别采用土柱淋溶方法及盆栽试验研究了磷酸铵镁堆肥(MAPC)产品的氮磷养分释放特性及对油菜的肥效,并与普通化肥(CCH)、普通堆肥(CCO)、磷酸铵镁肥(MAP)3种肥料进行对比。结果表明:在整个淋溶过程中,CCH和MAPC处理淋溶液的总氮及总磷浓度均较其他处理高;MAP肥具有缓释性,且堆肥对其养分释放具有促进作用;CCO处理的养分释放最慢。在最后一次淋洗(即第5次)后,总氮及总磷养分浓度排序均为:CCHMAPCMAPCCO。盆栽试验18 d后油菜快速生长,且与对照(不施肥)处理相比,MAP和MAPC处理能显著提高油菜的株高及生物量。在45 d盆栽试验结束时,CCH、CCO、MAP和MAPC处理的生物量分别是对照处理的14.8、4.8、20.5倍和16.0倍。MAP处理能显著提高油菜的养分含量,TN和TP含量分别比对照提高了2.24 g·kg~(-1)和1.54 g·kg~(-1)。研究表明,4种肥料均可改善油菜的生长发育情况,且MAP和MAPC的肥效优于CCH和CCO,在堆肥中利用鸟粪石结晶原理可固定部分氮磷元素,提高堆肥产品肥效。 相似文献
7.
Azin Rekowski Monika A. Wimmer Bernd Hitzmann Bernhard Hermannseder Heike Hahn Christian Zrb 《植物养料与土壤学杂志》2020,183(2):260-270
Background: Nitrogen losses is an economic problem for wheat production and a high risk to the environment. Therefore, improved N fertilizer management is a key to increasing the N efficiency and minimizing N losses. To increase N efficiency, enhanced fertilizers such as urea combined with urease inhibitor can be used. Aims: The aim of present study was to evaluate the effects of different N forms on grain storage protein subunits in winter wheat and to examine whether the observed changes correlate with parameters of baking quality. Methods: The investigation was performed over two consecutive years at two locations in Germany. Protein subunits were analyzed by SDS‐PAGE. Results: Protein concentrations were similarly increased after fertilization with ammonium nitrate and urea + urease inhibitor. Analysis of the individual storage protein fractions indicated that both fertilizers specifically enhanced ω‐gliadins and HMW glutenins, but the effect was more pronounced in the ammonium nitrate treatment. Application of urea + urease inhibitor had greater influence on the protein composition and resulted in higher specific baking volume as well as the best fresh keeping ability, in comparison with urea treatment. Conclusion: Considering that the urea + urease inhibitor treatment resulted in almost comparable improvements of NUE and baking quality, with the additional benefit of reduced N losses in combination with easy handling, urea + urease inhibitor can be recommended as a viable alternative to both urea alone and ammonium nitrate treatments. This opens up an opportunity for the reduction of N loss in wheat production when use of urea is preferred. 相似文献
8.
9.
Soo-Young CHOI Woo-Chang JEONG Young-Won LEE Ho-Jung CHOI 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2016,78(2):239-244
Contrast enhanced ultrasound (CEUS) is useful to evaluate tissue perfusion in the kidney. In veterinary
medicine, sedation or anesthesia may be required in uncooperative or panting patients. The aim of this study
was to evaluate and compare the normal kidney perfusion patterns in conscious and anesthetized dogs using
CEUS. Eight healthy beagles were used in this study. Scanning was performed in conscious dogs using manual
restraint (conscious group), or under general anesthesia using tiletamine-zolazepam and medetomidine (TZM
group) or medetomidine (M group). The contrast agent (Sonovue®) was administered as an IV bolus.
The peak intensity (PI), time to peak enhancement from injection (TTP0) and the time to peak
enhancement from the initial rise (TTPup), upslope, downslope and area under the curve (AUC) were
analyzed. Compared to the cortical values in the conscious group, TTP0 was significantly delayed in
the TZM group, and upslope, TTP0 and TTPup were significantly different in the M group.
The AUCs in the TZM and M groups were not different from those in the conscious group. The upslope of renal
medullary perfusion was significantly decreased in the TZM and M groups. TTP0 and TTPup
were also significantly delayed in these groups. The AUC of the medulla was significantly decreased in the M
group. Therefore, TZM is useful as an anesthetic protocol when performing CEUS, and the obtained data may
serve as reference values in the evaluation of renal perfusion using CEUS in dogs under anesthesia. 相似文献
10.
改性尿素硝酸铵溶液调控氮素挥发和淋溶的研究 总被引:1,自引:0,他引:1
为了提高肥料的利用率,以尿素硝酸铵溶液为原料、聚氨酸为保护剂,复合抑制剂NBPT(N-丁基硫代磷酰三胺)和DMPP(3,4-二甲基吡唑磷酸盐)为材料,开发出改性尿素硝酸铵溶液(YUL1和YUL2),研究其对华北平原夏玉米追肥过程中的氨挥发和淋溶损失的调控效果。田间试验设置6个处理:不施氮肥(CK)、农民习惯追施尿素(CN)、优化追施尿素(CNU)、优化追施尿素硝酸铵溶液(UAN)、优化追施改性尿素硝酸铵溶液(YUL1)和优化追施改性尿素硝酸铵溶液(YUL2)。采用扫描电镜和能谱仪分析相关指标变化,在夏玉米喇叭口期追施氮肥后15d内进行田间原位连续动态观测氨挥发和土壤铵态氮和硝态氮变化,并在玉米成熟期测定产量,计算经济效益。结果表明,改性尿素硝酸铵溶液清澈无杂质,流延后成膜表面光滑、致密,抑制剂在膜表面分布均匀;能谱测试膜层表面磷硫含量增高,证明复合抑制剂与尿素硝酸铵溶液达到有效融合。在同等优化施氮量下:与CNU相比, YUL1氨挥发总量显著降低19.3%, YUL2增加9.6%;与UAN相比, YUL1、YUL2分别显著降低57.3%和42.0%。与其他施氮处理相比, YUL1和YUL2夏玉米季生长中后期0~20 cm土层依然保持相对较高的氮素含量水平,夏玉米收获后土壤硝态氮含量分别比CNU高46.0%和43.4%,比UAN高45.6%和44.7%;180~200cm土层硝态氮含量显著低于其他处理。在保证产量和净收益的同时,改性尿素硝酸铵肥料显著降低了氮素的氨挥发和淋溶损失浓度,尿酶抑制剂含量相对较高的YUL1抑制氨挥发的效果更好,硝化抑制剂含量相对高的YUL2硝态氮向下淋失的风险更小。 相似文献