Influences of sand cover on erosion processes of loess slopes based on rainfall simulation experiments

Aeolian-fluvial interplay erosion regions are subject to intense soil erosion and are of particular concern in loess areas of northwestern China.Understanding the composition,distribution,and transport processes of eroded sediments in these regions is of considerable scientific significance for controlling soil erosion.In this study,based on laboratory rainfall simulation experiments,we analyzed rainfall-induced erosion processes on sand-covered loess slopes(SS)with different sand cover patterns(including length and thickness)and uncovered loess slopes(LS)to investigate the influences of sand cover on erosion processes of loess slopes in case regions of aeolian-fluvial erosion.The grain-size curves of eroded sediments were fitted using the Weibull function.Compositions of eroded sediments under different sand cover patterns and rainfall intensities were analyzed to explore sediment transport modes of SS.The influences of sand cover amount and pattern on erosion processes of loess slopes were also discussed.The results show that sand cover on loess slopes influences the proportion of loess erosion and that the compositions of eroded sediments vary between SS and LS.Sand cover on loess slopes transforms silt erosion into sand erosion by reducing splash erosion and changing the rainfall-induced erosion processes.The percentage of eroded sand from SS in the early stage of runoff and sediment generation is always higher than that in the late stage.Sand cover on loess slopes aggravates loess erosion,not only by adding sand as additional eroded sediments but also by increasing the amount of eroded loess,compared with the loess slopes without sand cover.The influence of sand cover pattern on runoff yield and the amount of eroded sediments is larger than that of sand cover amount.Furthermore,given the same sand cover pattern,a thicker sand cover could increase sand erosion while a thinner sand cover could aggravate loess erosion.This difference explains the existence of intense erosion on slopes that are thinly covered with sand in regions where aeolian erosion and fluvial erosion interact.     

Simulation of future dissolved oxygen distribution in pond culture based on sliding window-temporal convolutional network and trend surface analysis

Dissolved oxygen (DO) is a key ecological factor to measure the quality of water in the aquaculture. As the pond water body is affected by the breeding environment, the spatial distribution of DO shows a certain law in the entire pond. Therefore, to simulate the distribution of DO in aquaculture waters and grasp the temporal and spatial variation of DO is the key to achieving precise regulation of DO. For this purpose, this paper proposed a method for simulating the temporal and spatial distribution of DO in pond culture based on a sliding window-temporal convolutional network together with trend surface analysis (SW-TCN-TSA). This paper first utilized SW to construct DO data sets with different prediction durations, and then used the improved TCN model to realize one-dimensional time series prediction for DO at single monitoring point. Based on the prediction results of DO, a TSA method was performed on the predicted values of DO at the extreme moments of all discrete monitoring points, so as to realize the simulation of the temporal and spatial distribution of DO in the pond. Experimental results show that the SW-TCN model has better prediction performance for one-dimensional time series prediction of DO. Compared with traditional deep networks, such as CNN, GRU, LSTM, CNN-GRU and CNN-LSTM, the values of evaluation indicators (MSE, MAE and RMSE) have been greatly improved. In the process of trend surface fitting, all fitting R² of DO at different water depths are higher than 0.9, indicating that the TSA can accurately reflect the temporal and spatial distribution of DO. This method can provide a basis for the prediction and early warning of DO in the three-dimensional space of the pond and has high practicability in aquaculture.     

城镇污水处理厂供配电系统分析

污水处理已成为城市建设中必不可少的环节,所以对相应的配套工程也提出了更高的要求,本文将对污水处理厂的供配电系统进行简要的分析。     

社群丰容对圈养小熊猫区域分配的影响

为探索社群丰容对重庆动物园圈养小熊猫行为区域分配的影响,2014年1月—2015年2月,用目标动物取样法对比观察春季、夏季、秋季、冬季社群丰容前后圈养小熊猫区域分配。结果表明:社群丰容增加了小熊猫对栖架、树上的利用,减少了内室和裸露地面和近游客区域的利用。树上利用的最大占比值在夏季,丰容增加了11.1%;栖架的利用最大占比值在春季,丰容增加了2.8%;冬季对内室的利用占比值最高,丰容后,其利用占比减少了8.4%,从而相应增加了小熊猫户外停留时间;丰容后,小熊猫对裸露地面的最大利用占比值减少了3.7%,近游客区域最大占比值减少了5.6%。小熊猫对六大区域的最高利用占比,丰容前后没有变化,最高为树上,最少为裸露地面。     

Greater humification of belowground than aboveground biomass carbon into particulate soil organic matter in no-till corn and soybean crops

Quantifying the amount of carbon (C) incorporated from decomposing residues into soil organic carbon (C_S) requires knowing the rate of C stabilization (humification rate) into different soil organic matter pools. However, the differential humification rates of C derived from belowground and aboveground biomass into C_S pools has been poorly quantified. We estimated the contribution of aboveground and belowground biomass to the formation of C_S in four agricultural treatments by measuring changes in δ¹³C natural abundance in particulate organic matter (C_POM) associated with manipulations of C₃ and C₄ biomass. The treatments were (1) continuous corn cropping (C₄ plant), (2) continuous soybean cropping (C₃), and two stubble exchange treatments (3 and 4) where the aboveground biomass left after the grain harvest was exchanged between corn and soybean plots, allowing the separation of aboveground and belowground C inputs to C_S based on the different δ¹³C signatures. After two growing seasons, C_POM was primarily derived from belowground C inputs, even though they represented only ∼10% of the total plant C inputs as residues. Belowground biomass contributed from 60% to almost 80% of the total new C present in the C_POM in the top 10 cm of soil. The humification rate of belowground C inputs into C_POM was 24% and 10%, while that of aboveground C inputs was only 0.5% and 1.0% for soybean and corn, respectively. Our results indicate that roots can play a disproportionately important role in the C_POM budget in soils. Keywords Particulate organic matter; root carbon inputs; carbon isotopes; humification rate; corn; soybean.     

Herbicide options for effective weed management in dry direct-seeded rice under scented rice-wheat rotation of western Indo-Gangetic Plains

Farmers' participatory field trials were conducted at Madhuban, and Taraori, the two participatory experimental sites/locations of the Cereal Systems Initiative for South Asia (CSISA), a collaborative project of IRRI and CIMMYT in Karnal district of Haryana, India, during Kharif (wet season) 2010 and 2011. This research aimed to evaluate preemergence (PRE) and postemergence (POST) herbicides for providing feasible and economically viable weed management options to farmers for predominant scented rice varieties. Treatments with pendimethalin PRE fb bispyribac-sodium + azimsulfuron POST had lower weed biomass at 45 days after sowing (DAS). At Madhuban, highest grain yield of scented basmati rice (3.43 t ha⁻¹) was recorded with the sequential application of pendimethalin PRE fb bispyribac-sodium + azimsulfuron POST. However, at Taraori, yields were similar with pendimethalin or oxadiargyl PRE fb bispyribac-sodium and/or azimsulfuron POST. Applying oxadiargyl by mixing with sand onto flooded field was less effective than spray applications in non-flooded field. The benefit-cost ratio of rice crop was higher with herbicide treatments at both sites as compared with the non-treated weed-free check except single PRE and POST applications and sequential application of oxadiargyl PRE fb oxadiargyl PRE. In a separate experiment conducted at Nagla and Taraori sites, scented rice cultivars' ('CSR 30′ and 'Pusa 1121′) tolerance to three rates of azimsulfuron (15, 25, and 35 g ai ha⁻¹) was evaluated over two years (2010 and 2011). CSR 30 (superfine, scented) was more sensitive to higher rates (35 g ai ha⁻¹) of azimsulfuron as compared to Pusa 1121 (fine, scented). Crop injuries were 8 and 28% in case of CSR 30; 5 and 15% in Pusa 1121 when applied with azimsulfuron 25 and 35 g ai ha⁻¹, respectively. Azimsulfuron applied at 35 g ai ha⁻¹ reduced yield in both cultivars but in CSR 30 yield reduction was twofold (11.5%) as that of Pusa 1121 (5.2%).     

基于MaxEnt模型的可可潜在适宜分布研究

根据野外采样和文献查阅,系统整理了可可的地理分布记录,并利用MaxEnt生态位模型和ArcGIS软件对可可的潜在适宜分布范围进行预测。结果表明:北美洲南部、中南美洲北部、非洲西部、亚洲东南部以及太平洋美拉尼西亚群岛地区均是可可的潜在适宜分布区域。其中,中国海南、台湾南部、云南西双版纳、广东雷州半岛也属于可可的适生范围。经ROC(Receiver operating characteristic)曲线分析法验证,MaxEnt模型的AUC(Area under curve)值为0.977,表明预测结果具有较高的可信度。各环境变量重要性的Jacknife检验表明,极端最低温度、年降雨量、年温度变化范围、最暖季降雨量对可可的潜在分布影响最大。     

肌细胞增强因子2B基因在人和动物中的研究进展

肌细胞增强因子2B(MEF2B)基因属于肌细胞增强因子2(MEF2)基因家族成员,广泛表达于人和动物的肌肉和神经组织中,在肌肉生成、神经系统发育和分化、肝脏纤维化等方面具有重要的作用,作者从MEF2B基因的结构、组织分布、生物学功能及研究进展等方面对该基因进行了综述.     

仿生法评定抗草甘膦玉米和转Bt基因玉米的酶水解物能值的研究

本试验旨在分析抗草甘膦玉米和转Bt基因玉米原料及饲粮与同源非转基因玉米原料及饲粮体外总能消化率以及酶水解物能值,为转基因玉米的营养实质等同性仿生评定方法的研究提供参考。试验采用单因素完全随机设计,使用单胃动物仿生消化系统模拟饲料原料和饲粮在鸡胃肠道的消化过程,分析同源非转基因玉米、抗草甘膦玉米和转Bt基因玉米以及对应的3种玉米-豆粕饲粮在不同体外模拟消化阶段的干物质消化率、总能消化率和酶水解物能值的差异。结果表明:同源非转基因玉米、抗草甘膦玉米和转Bt基因玉米以及对应饲粮在常规概率成分含量上是相似的。抗草甘膦玉米及饲粮与同源非转基因玉米及饲粮相比,在干物质和能量胃消化率、全消化道消化率及酶水解物能值上均没有显著差异(P0.05)。转Bt基因玉米全消化道总能消化率低于同源非转基因玉米(P=0.03,变异系数=0.50%),对应玉米饲粮的酶水解物能值则高于同源非转基因玉米饲粮(P=0.02,变异系数=1.12%),但均处于仿生消化系统测试的误差范围内(变异系数≤1.64%)。由此可见,抗草甘膦玉米的酶水解物能值与同源对照玉米没有差异,而转Bt基因玉米存在统计学意义上的差异,但所有的测值均处于仿生消化系统的测试误差之内。仿生法发现的差异是否具有生物学意义有待体内试验验证。仿生法可为转基因饲料营养等同性研究提供一种新方法。