Annual variation of adult survival of a south-temperate House Wren population in Argentina

Identifying factors affecting the survival of individuals is essential for understanding the evolution of life-history traits and population dynamics.Despite numerous studies on this subject in north-temperate environments,there is a lack of equivalent studies at similar latitudes in the south.Here,we used a 14-year dataset of capture,banding,and resighting to estimate the annual variation in the apparent adult survival probability of a south-temperate population of House Wrens(Troglodytes aedon bonariae).We evaluated temporal variation in sur-vival and the effect of environmental(climatic)and demographic variables(adult abundance,total number of fledglings produced during each breeding season)on survival estimators.We found that the probability of adult survival decreased as the abundance of breeding adults increased.This density-dependent effect could be related to the resident lifestyle of southern House Wrens,which could determine an intense competition for territories and resources that ultimately would affect their survival.

The changes in the annual distribution of mountain runoff during the period of 1965-2018 in Hexi Corridor,Northwest China

The annual distribution characteristics of river runoff in arid regions have significant implications for water resource stability and management.Based on the mountain runoff data from 1965 to 2018,this study examines the annual change characteristics of monthly runoff of the Shiyang River Basin,Heihe River Basin,and Shule River Basin in the Hexi Corridor,Northwest China.Many indexes are used and analyzed,including the coefficient of variance,the complete regulation coefficient,the concentration degree and concentration period,the magnitude of change,the skewness coefficient,and the kurtosis coefficient of the annual distribution curves.The results reveal the following:(1)The inhomogeneity of annual runoff distribution in the Taolai River and the rivers to the west of it,except the Shiyou River,show an increasing trend.Conversely,the inhomogeneity of the rivers to the east of the Taolai River generally show a downward trend,but the coefficient of variance value is still very high.(2)In the Shiyang River Basin,the annual distribution of the concentration period is characterized by a relatively discrete pattern.Conversely,the Heihe River Basin exhibits a relatively concentrated pattern,and the distribution pattern of the Shule River Basin is quite different.Notably,all concentration periods in the three basins have shifted backward after the 2000s.(3)The Shiyang River Basin exhibits disordered annual distribution curves of runoff in different years.In contrast,the Heihe River Basin presents a typical‘single-peak’pattern with a prominent right-skewed.The Shule River Basin has regular distribution curves,with a gradually significant‘double-peak’pattern from east to west.Overall,there has been a slight change in runoff in the Shiyang River Basin,while the Heihe River Basin and Shule River Basin have experienced significant increases in runoff.The annual distribution curves of runoff in the Liyuan River and the rivers to the east of it exhibit a gentle peak pattern,and the appearance probability of extreme runoff during the year is low.Conversely,the rivers to the west of the Liyuan River,excluding the Danghe River,display a sharp peak and thick tail pattern,indicating that the appearance probability of extreme runoff during the year is high.These findings have practical implications for the planning and management of water resources in the Hexi Corridor.Moreover,they provide a solid foundation for predicting future changes in regional water resources.

Fragipan Horizon Changes Using Annual Ryegrass and Other Admendments

A greenhouse experiment was conducted involving intact fragipan soil cores of 50 cm thickness after removing the topsoil horizons. The cores were maintained in moist condition throughout the experiment and received several treatments with various amendments for different periods ranging from 9 to 17 months. The amendments included annual ryegrass or Festulolium residues, powder limestone and various humate compounds alone or in combination with the grass residues. The results suggested a significant effect of ryegrass and Festulolium in reducing penetration resistance into the top 10 cm of the fragipan within 9 - 17 months, particularly when used in combination with certain humate materials such as Leonardite. Apparently, this is the result of the release of certain soluble organic compounds from the plant residues or the humate amendments that increase the solubility of Si and Al associated with the fragipan brittleness, thus decreasing the density of the compacted fragipan material.

Harmonious Inter-decadal Changes of July–August Upper Tropospheric Temperature Across the North Atlantic, Eurasian Continent,and North Pacific

The authors have developed an integral view of the inter-decadal variability of July-August （JA） tropospheric temperature across the entire subtropical Northern Hemisphere. Using reanalysis data and complementary balloon-borne measurements, the authors identify one major mode of variability for the period 1958 2001 which exhibits a significant cooling center over East Asia and warming centers over the North Atlantic and North Pacific. The cooling （warming） signals barotropically penetrate through the troposphere, with the strongest anomalies at 200-300 hPa. The amplitude of the cooling over East Asia is stronger than that of the warming over the North Atlantic （North Pacific） by a factor of 2 （3）. This dominant mode exhibits a declining tendency for the entire period examined, particularly before 1980. After the mid-1980s, the tendency has leveled off. Variations of the harmonious change of JA upper tropospheric temperature represented by the principal component of Empirical Orthogonal Function analysis exhibit significant negative （positive） correlations with SST anomalies in the eastern tropical Pacific and the western tropical Indian Ocean （mid-latitude North Pacific）. Possible mechanisms are discussed.

Southern Ocean SST Variability and Its Relationship with ENSO on Inter-Decadal Time Scales

Empirical orthogonal function （EOF） analysis reveals a co-variability of Sea surface temperatures （SSTs） in the Southern Hemisphere （0°-60°S）. In the South Indian and Atlantic Oceans, there is a subtropical dipole pattern slanted in the southwest-northeast direction. In the South Pacific Ocean, a meridional tripole structure emerges, whose middle pole co-varies with the dipoles in the South Indian and Atlantic Oceans and is used in this study to track subtropical Pacific variability. The South Indian and Atlantic Ocean dipoles and the subtropical Pacific variability are phase-locked in austral summer. On the inter-decadal time scales, the dipoles in the South Indian and Atlantic Oceans weaken in amplitude after 1979/1980. No such weakening is found in the subtropical South Pacific Ocean. Interestingly, despite the reduced amplitude, the correlation of the Indian Ocean and Atlantic dipoles with E1 Nino and Southern Oscillation （ENSO） are enhanced after 1979/1980. The same increase in correlation is found for subtropical South Pacific variability after 1979/1980. These inter-decadal modulations imply that the Southern Hemisphere participates in part of the climate shift in the late 1970s. The correlation between Southern Hemisphere SST and ENSO reduces after 2000.

Inter-decadal variations,causes and future projection of the Asian summer monsoon

The present paper presents a concise summary of our recent studies on the Asian summer monsoon,with highting decadal and inter- decadal scales. The studies on the long- term variations of the Asian summer monsoon and its impacts on the change in the summer precipitation in China are reviewed. Moreover,recent changes in the Asian summer monsoon and summer precipitation in East Asia(including Meiyu precipitation)are discussed. Finally,the future changes of the Asian summer monsoon are also pointed out in this paper.

A decomposition study of moisture transport divergence for inter-decadal change in East Asia summer rainfall during 1958-2001

In this paper, we report on the results of an investigation into inter-decadal changes in moisture transport and divergence in East Asia for the two periods 1980-2001 and 1958 1979. The aim is to explore the mechanism of summer rainfall change in the region after abrupt changes. The relevant changes are calculated using ERA-40 daily reanalysis datasets. The results show that both stationary and transient eddy moisture transports to the Chinese mainland have declined since the abrupt change in atmospheric general circulation in the late 1970s, leading to more rainfall in South China and less in the North. The anomalous rainfall pattern coincides well with anomalous large-scale moisture divergence in the troposphere, of which stationary-wave or monsoon transport is dominant, in comparison with the contribution of the transient eddies. F^rthermore, their divergences are found to be in opposite phases. In addition, meridional divergence is more important than its zonal counterpart, with an opposite phase in East Asia. Abnormal zonal moisture convergences appear in northwestern and northeastern parts of China, and are related to the excess rainfalls in these regions. An increase in transient eddy activity is one of the major mechanisms for excess rainfall in northern Xinjiang. Consequently, the anomalous rainfall pattern in East Asia results from a decline of the East Asian monsoon after the abrupt change, while the rainfall increase in northwestern China involves anomalies of both stationary waves and transient eddies on boreal westerly over the mid- and high latitudes.

Inter-decadal Analysis on the Intensity of Summer Monsoon in Northeast China

In this paper,the intensity index of East Asian summer monsoon in northeast China was defined objectively by using NCEP/NCAR daily reanalysis data and national precipitation data from 1961 to 2004.In the inter-decadal time scales,the correlations between sea-level pressure field,850 hPa flow field,500 hPa geopotential height,sea surface temperature,Arctic sea ice concentration,a variety of oscillation indexes and intensity index of East Asian summer monsoon in northeast China were analyzed.The analysis showed that the great value area of correlations was consistent between sea-level pressure field,500 hPa geopotential height field and intensity index of East Asian summer monsoon in northeast China in pre-winter or summer,and the correlation was much better in summer than in pre-winter.The correlation was poor between the sea surface temperature and intensity index of East Asian summer monsoon in northeast China,but the correlation was good between the Arctic sea ice concentration and intensity index of East Asian summer monsoon in northeast China.The correlation was better between the NPO index and intensity index of East Asian summer monsoon in northeast China than other indexes.

Modeled Influence of East Asian Black Carbon on Inter-Decadal Shifts in East China Summer Rainfall

Two inter-decadal shifts in East China summer rainfall during the last three decades of the 20th century have been identified.One shift occurred in the late 1970s and featured more rainfall in the Yangtze River valley and prolonged drought in North China.The other shift occurred in the early 1990s and featured increased rainfall in South China.The role of black carbon(BC) aerosol in the first shift event is controversial,and it has not been documented for the second event.In this study,the authors used Geophysical Fluid Dynamics Laboratory's(GFDL's) atmospheric general circulation model known as Atmosphere and Land Model(AM2.1) ,which has been shown to capture East Asian climate variability well,to investigate these issues by conducting sensitive experiments with or without historical BC in East Asia. The results suggest that the model reproduces the first shift well,including intensified rainfall in the Yangtze River and weakened monsoonal circulation.However,the model captures only a fraction of the observed variations for the second shift event.Thus,the role of BC in modulating the two shift events is different,and its impact is relatively less important for the early 1990s event.

Recent strong inter-decadal change of Meiyu in 121-year variations

The strongest change in Meiyu periods in the mid-lower Yangtze Basin （MLY） since 1885 occurred in the late 1970s： a stage of weak Meiyu from 1958 to 1978 abruptly transformed into a stage of plentiful Meiyu from 1979 to 1999. The average Meiyu amount of the latter 21 years increased by 66% compared with that of the former 21 years, accompanied by a significant increase in the occurrence of summer floods in the MLY. This change was closely related with the frequent phenomenon of postponed Meiyu ending dates （MED） and later onset dates of high summer （ODHS） in the MLY. To a considerable degree, this reflects an abrupt change of the summer climate in East China. Further analysis showed that the preceding factors contributing to inter-annual changes in Meiyu in the two 21-year stages delimited above were also very different from each other. The causes of change were associated with the following： China’s industrialization has greatly accelerated since the 1970s, accompanied by an increase in atmospheric pollution and a reduction of the solar radiation reaching the ground. The sand area of North China has also expanded due to overgrazing. The enhanced greenhouse effect is manifested in warm winters （especially in February）. Meanwhile, the January precipitation of the MLY has for the most part increased, and El Ni？o events have occurred more frequently since the late 1970s. A correlative scatter diagram consisting of these five factors mentioned above clearly shows that the two stages with opposite Meiyu characteristics are grouped in two contrasting locations with very different environmental （land-atmosphere） conditions. It is quite possible that we are now entering a new stage of lesser Meiyu, beginning in 2000.

CLIMATIC CHARACTERISTICS OF THE ONSET OF SOUTH CHINASEA SUMMERMONSOON II.INTER-DECADAL VARIATION

By using the 40-year NCEP (1958-1997) grid point reanalysis meteorological data, we analyzed the inter-decadal variation on the climatic characteristics of the onset of South China Sea summer monsoon. The results are as follows. (1) There was great difference on the onset date of the SCS summer monsoon between the first two decades and the last two decades. It was late on the 6th pentad of May for the first two decades and was on the 4th and 5th pentad of May for the next two decades. (2) Except for the third decade (1978-1987), the establishment of the monsoon rainfall was one to two pentads earlier than the onset of the summer monsoon in all other three decades. (3) The onset of the SCS monsoon is the result of the abrupt development and eastward advancement of the southwesterly monsoon over the Bay of Bengal. The four-decade analysis shows that there were abrupt development of the southwesterly monsoon over the Bay of Bengal between the 3rd and 4th pentad of May, but there was great difference between its eastward movement and its onset intensity. These may have important effect to the earlier or later onset of the SCS summer monsoon. (4) During the onset of the SCS summer monsoon, there were great difference in the upper and lower circulation feature between the first two and the next two decades. At the lower troposphere of the first two decades, the Indian-Burma trough was stronger and the center of the subtropical high was located more eastward. At the upper troposphere, the northward movement of the center of subtropical high was large and located more northward after it landed on the Indo-China Peninsula. After comparison, we can see that the circulation feature of the last two decades was favorable to the establishment and development of the SCS summer monsoon.

Histology, physiology, and transcriptomic and metabolomic profiling reveal the developmental dynamics of annual shoots in tree peonies (Paeonia suffruticosa Andr.)

The development of tree peony annual shoots is characterized by“withering”,which is related to whether there are bud points in the leaf axillaries of annual shoots.However,the mechanism of“withering”in tree peony is still unclear.In this study,Paeonia ostii‘Fengdan’and P.suffruticosa‘Luoyanghong’were used to investigate dynamic changes of annual shoots through anatomy,physiology,transcriptome,and metabolome.The results demonstrated that the developmental dynamics of annual shoots of the two cultivars were comparable.The withering degree of P.suffruticosa‘Luoyanghong’was higher than that of P.ostii‘Fengdan’,and their upper internodes of annual flowering shoots had a lower degree of lignin deposition,cellulose,C/N ratio,showing no obvious sclerenchyma,than the bottom ones and the whole internodes of vegetative shoot,which resulted in the“withering”of upper internodes.A total of 36 phytohormone metabolites were detected,of which 33 and 31 were detected in P.ostii‘Fengdan’and P.suffruticosa‘Luoyanghong’,respectively.In addition,302 and 240 differentially expressed genes related to lignin biosynthesis,carbon and nitrogen metabolism,plant hormone signal transduction,and zeatin biosynthesis were screened from the two cultivars.Furtherly,36 structural genes and 40 transcription factors associated with the development of annual shoots were highly co-expressed,and eight hub genes involved in this developmental process were identified.Consequently,this study explained the developmental dynamic on the varied annual shoots through multi-omics,providing a theoretical foundation for germplasm innovation and the mechanized harvesting of tree peony annual shoots.

Detecting Climate Change Trend, Size, and Change Point Date on Annual Maximum Time Series Rainfall Data for Warri, Nigeria

The study focused on the detection of indicators of climate change in 24-hourly annual maximum series (AMS) rainfall data collected for 36 years (1982-2017) for Warri Township, using different statistical methods yielded a statistically insignificant positive mild trend. The IMD and MCIMD downscaled model’s time series data respectively produced MK statistics varying from 1.403 to 1.4729, and 1.403 to 1.463 which were less than the critical Z-value of 1.96. Also, the slope magnitude obtained showed a mild increasing trend in variation from 0.0189 to 0.3713, and 0.0175 to 0.5426, with the rate of change in rainfall intensity at 24 hours duration as 0.4536 and 0.42 mm/hr.year (4.536 and 4.2 mm/decade) for the IMD and the MCIMD time series data, respectively. The trend change point date occurred in the year 2000 from the distribution-free CUSUM test with the trend maintaining a significant and steady increase from 2010 to 2015. Thus, this study established the existence of a trend, which is an indication of a changing climate, and satisfied the condition for rainfall Non-stationary intensity-duration-frequency (NS-IDF) modeling required for infrastructural design for combating flooding events.

The Inter-Annual Variability of Rainfall Onset and Its Implication on Crop Planting in Selected East Africa Countries

The inter-annual variability of rainfall onset and crop replanting in East Africa (EA) was assessed using daily estimated rainfall data from climate hazard group infrared precipitation (CHIRPS Ver2.0) and monthly Sea Surface Temperature (SST) indices [Indian Ocean Dipole (IOD) and El-Ni?o Southern Oscillation (ENSO) at NINO3.4 region] from the National Center for Environmental Prediction (NCEP) and the National Center for Atmospheric Research (NCAR). The data covered a period of 40 years from1981 to 2020. The methods of cumulative of daily mean rainfall, percentage of onset date departure (PODD), Mann-Kendall (MK) trend test, student t-test, and correlation were applied in the analysis. The results showed that early onset with dry spell (WDS) consideration frequently occurs in Uganda between the first and second dekads of September, while late rainfall onset WDS occurs in the first and second dekads of December over central and Northern Kenya as well as in the Northeastern highlands, parts of the northern coast and unimodal regions in Tanzania. Rainfall onset with no dry spell (WnDS) portrayed an average of 10 days before the occurrence of true onset WDS, with maximum onset departure days (ODD) above 30 days across the Rift Valley area in Kenya and the Northeastern highlands in Tanzania. The high chance of minimum ODD is seen over entire Uganda and the area around Lake Victoria. However, few regions, such as Nakuru (Kenya) Gulu and Kibale (Uganda), and Gitega (Burundi), revealed a slight positive linear trend while others showed negative trend. Significant positive patterns for correlation between onset WDS and SST indices (IOD and NINO 3.4) were discovered in Northern and Northeastern Kenya, as well as areas along the Indian Ocean (over Tanzania’s Northern Coast). Inter-annual relationship between onset dates WDS and IOD (NINO3.4) indices exhibits a high correlation coefficient r = 0.23 (r = 0.48) in Uganda and r = 0.44 (r = 0.36) in Kenya. On the other hand, a negative correlation was revealed over Burundi and Tanzania (over a unimodal region). A high percentage of PODD was observed, ranging from 40% to 70% over the Rift Valley in Kenya and at the Northeastern highlands in Tanzania. However, a strong PODD above 70% was observed over Tanga and the Northern Pwani Region in Tanzania. These findings will help farmers to understand the appropriate time for crop planting, as well as help other socio-economic activities that strongly depend on rainfall.

基于第十三代国际地磁参考场模型在中国区域特征分析与研究

根据最新的第十三代国际地磁参考场模型(IGRF13),计算了2015—2020年中国区域地磁场模型七要素长期变化速率,并在此基础上分析我国区域地磁场长期变化特征。通过分析计算我国28个地磁台的IGRF13模型值与实际地磁场的长期变化速率、差值及均方误差,结果显示:IGRF13模型所显示的地磁场长期变化与我国区域地磁场实际观测变化基本一致,但在局部区域也存在差异,IGRF13模型能够体现中国区域地磁场的特征。应用IGRF13模型数据时需要考虑局部区域与台站实际观测数据的误差。

基于地球河流扇预测模型的火星地表水径流量预测

【目的】火星表面的水活动地质历史一直是科学界关心的热点,直接影响着火星探测的研究方向。【方法】根据火星和地球的可对比性,建立了融合345个地球现代河流扇沉积的数据集并形成了高精度扇体面积预测模型,从而识别火星上的河流扇沉积,预测火星河流扇发育期的地表水径流量。【结果】结果表示,在火星南部高地霍尔顿陨石坑附近识别出一个面积约84.35 km^(2)的典型河流扇沉积,并反向预测出该扇体形成需要的年平均地表水径流量为1.8828×10^(6)m^(3),推测出该区域径流量不是由单一降水构成,为雪山(冰川)融水和降水多种来源。【结论】该成果是河流扇研究在行星沉积学中的应用,为进一步深入研究火星和其他天体地表水活动提供了新的方法。

OSCE在儿科规培年度考核的应用

目的探讨客观结构化临床考试(OSCE)在儿科住院医师规范化培训(以下简称“规培”)年度考核中的应用价值。方法选取2018年一、二年级规培学员67人及2019年二、三年级规培学员67人(与2018年相同的规培学员、只是年级产生变化)。设2018年一年级规培学员为A组、二年级规培学员为B组,那么2019年二年级规培学员为A组、三年级规培学员为B组。对2018年及2019年A组、B组规培学员进行OSCE年度考核,进行成绩分析、问卷调查并开展点评会。结果2018年A组学员各站成绩及考试总成绩低于2018年B组学员,差异有统计学意义(P<0.05),2019年A组学员总成绩较2018年A组明显提升,差异有统计学意义(P<0.05);2019年A组总成绩和2019年B组比较,差异有统计学意义(P<0.05),2019年B组总成绩与2018年B组比较,差异有统计学意义(P<0.05)。考官及学员对OSCE考核形式100%满意,各考站设置合理,试卷难易程度适度;带教老师及规培管理人员100%肯定点评会发现教学及管理工作中的不足之处。结论规培学员低年级学习成绩提升速度最快、高年级能达到规培标准,OSCE在年度考核中的应用可以全面考查学员本年度专业知识及临床实践操作的掌握情况,同时也可以综合测评基地规培管理及临床带教工作,值得推广应用。

“妃子笑”荔枝高产若干生长发育性状

“妃子笑”荔枝是我国栽培区域最广的荔枝品种,比较研究不同区域“妃子笑”生长发育特性可为树冠、养分管理和成花着果调控及区域适应性发展等参考,为荔枝品种制订高产和克服“大小年”技术方案提供借鉴。2008—2022年,调查统计华南六省(区)北纬18°32′~28°47′的24县(区)39个示范园“妃子笑”物候期;于始花期调查海南、广东、广西和云南省(区)18个果园“妃子笑”结果树枝条、叶片和花穗生长量,并取样分析枝条、叶片、花穗主要养分含量,计算植株不同部位营养需求量。结果表明,主产区“妃子笑”末次秋梢成熟期8月下旬至11月中旬,现“白点”(花穗原基)期11月下旬至翌年2月中旬,盛花期2月上旬至4月上旬,果实成熟期4月下旬至7月底。3次秋梢生长分别约为35.9、39.5和40.2 d,秋梢老熟至现花穗原基(花诱导)约87 d,花穗与花芽分化期约56 d,果实发育期约需63 d。海南等地区“妃子笑”采果后树冠重回缩修剪至1.5 m高,形成矮化树形,而粤西等地修剪至2~3 m高,塑造高大树形。“妃子笑”结果植株采果后秋梢生长1~3次,树冠表面积的平均枝梢数16条/m2,秋梢平均长度37.7 cm,秋梢复叶数17片、叶片数104片。“妃子笑”单株不同部位年生长量,以鲜质量计分别为秋梢枝条16.8 kg,叶片40.2 kg,花穗17.2 kg;以干质量计为秋梢枝条9.50 kg,叶片23.24kg,花穗7.19kg。主要养分含量为秋梢枝条中氮0.76%、磷0.26%、钾0.72%、钙0.54%、镁0.15%;叶片中氮1.79%、磷0.17%、钾0.94%、钙0.77%、镁0.25%;花穗中氮2.20%、磷0.30%、钾1.74%、钙0.32%、镁0.29%。单株50 kg的产量,年度枝叶、花穗和果实生长所需主要元素为氮0.70 kg、磷0.10 kg、钾0.46 kg,秋梢期氮、磷、钾用量分别占比全年用量的71.4%、70.0%、63.0%。从多年产量稳定性看,海南省陵水县、琼海市、海口市,广西北海铁山港区、合浦县,广东省廉江市等地是“妃子笑”适应性表现较好的栽培区。综合而言,随着纬度北移和海拔升高,“妃子笑”物候期延后,果实成熟期持续3个月以上;各地区“妃子笑”物候期相差较大的是末次秋梢成熟期和果实成熟期,差异较小的是花芽诱导期;枝叶养分需求较大,确保秋梢生长量是支撑产量和品质的重要基础。

断层虚位错模式揭示的2022年1月8日青海门源M_(S)6.9地震前的地电阻率变化

选取2022年1月8日青海门源M_(S)6.9地震震中400 km范围内四个地电阻率观测台站的观测精度高、具有稳态年变、震前无显著干扰的地电阻率ρ_(s)观测数据,结合ERA5同化数据集中的多层土壤温度和土壤水分含量,在利用多项式拟合获取各台站(或测道)地电阻率正常年动态的基础上,分析了门源地震前地电阻率的异常变化。结果显示:金银滩台EW测道、武威台NS测道和山丹台EW测道、N45°W测道震前存在超阈值的异常变化,并呈现各向异性特征。基于断层虚位错模式分析了地电阻率异常变化与孕震过程之间的联系,结果表明:金银滩台震前处于压缩区并受到NNE方向的挤压,与主压应变近似正交的EW测道于震前10个月出现负异常;同样位于压缩区的武威台,受到了ENE向的挤压,NS测道的地电阻率在孕震早期(震前13个月)以负异常为主,孕震中晚期(震前3个月)出现了正异常;山丹台,位于膨胀区,受到近似NS向的拉张,与主张应变平行的NS测道未发现异常,但EW测道震前一年地电阻率出现正异常,N45°W测道的地电阻率也在震前半年左右出现超阈值并呈正异常。此外,金银滩台、山丹台和武威台距离门源地震震中的距离分别为92 km,113 km和139 km,相应的地电阻率异常最大变化幅值分别为−3.0σ,2.2σ和−2.1σ。此外,门源地震前地电阻率异常变化的时空特征与岩石实验结果及理论模型一致,也符合震源区应力应变积累程度较高、向外围方向逐渐衰减的分布特征。由此推断,2022年门源M_(S)6.9地震前地电阻率的时空变化可能与区域介质变形及应力变化有关。

黄土高原径流侵蚀功率输沙模型的改进

水土流失对流域生态危害严重,输沙量模拟和预测可以为流域水土流失防治提供依据,因此精确的输沙模型是流域水土流失治理的重要工具。为了精确模拟变化环境下黄土高原年输沙量,该研究基于黄土高原19个水文站的径流和输沙数据,通过随机森林变量重要性度量方法评估年径流侵蚀功率、淤地坝指数、淤地坝相对指数、归一化植被指数、不透水地面积等因子对流域年输沙量的影响,使用非线性最小二乘法估算年输沙模型参数,对比分析不同因子组合的年输沙模型精度,提出适用性较强的黄土高原年输沙模型,据此开展年输沙量变化贡献率分析。结果表明:1)以幂函数形式构建的仅含径流侵蚀功率单因子输沙模型精度与流域面积有显著的负相关关系,相关系数为-0.505(P<0.05),模型精度随着流域面积增大而下降,在面积大于7000 km^(2)的流域适用性较差;2)年径流侵蚀功率、淤地坝指数及不透水地面积因子组合建立的多因子年输沙模型在黄土高原适用性最佳,模型在率定期纳什效率系数平均值为0.84,均方根误差平均值为0.21亿t,在验证期纳什系数平均值为0.79,均方根误差平均值为0.27亿t。3)影响研究流域年输沙量变化的因素依次是:年径流侵蚀功率、不透水地面积和淤地坝指数。研究可以为黄土高原不同区域水土流失防治和生态治理工作提供理论支撑。